J Biol Inorg Chem (2014) 19 (Suppl 2):S749–S764 DOI 10.1007/s00775-014-1159-9

ORAL PRESENTATION

Oral presentations

OP 1 Development of potential anticancer agents by coordination of bioactive molecules to organometallic fragments Wolfgang Kandioller1,2, Stephan Mokesch1, Carmen Hackl1, Michael Jakupec1,2, Christian G. Hartinger3, Bernhard K. Keppler1,2

OP 2 Effect of a hexacationic ruthenium complex as potential anticancer drug on the cell metabolome studied by 1H HR-MAS NMR spectroscopy Martina Vermathen1, Lydia E.H. Paul1, Gae¨lle Diserens2, Peter Vermathen2, Julien Furrer1 1

Institute of Inorganic Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna, Austria. [email protected] 2 Research Platform ‘‘Translational Cancer Therapy Research’’, University of Vienna, Waehringer Strasse 42, 1090 Vienna, Austria 3 The University of Auckland, School of Chemical Sciences, Private Bag 92019, Auckland 1142, New Zealand Ru(II)-arene complexes are promising alternatives for the clinically applied platinum-based chemotherapeutics. One approach is the attachment of bioactive molecules to organometallic moieties, leading to compounds with potential multi-targeted character which are able to interact with different biological targets [1,2]. [1,4]Naphthoquinones are known for its broad range of biological activities such as antibacterial, anti-inflammatory and anticancer activities and the mode of action is supposed to be related to reactive oxygen species (ROS) formation. [1,3]-Dioxoindan-2-carboxamides have shown promising topoisomerase inhibiting properties and this compound class can be easily obtained by rearrangement of the [1,4]-naphthoquinone backbone. With the aim to develop novel metallodrugs with potential multi-targeted properties, these bioactive scaffolds were coordinated to organometallic fragments. The synthesized ligands and the corresponding Ru(II), Os(II) and Rh(III) complexes were characterized by standard analytical methods and their behaviour under physiological conditions, binding affinity towards biomolecules, cytotoxicity in human cancer cell lines, ROS generating ability and further mode of action studies will be discussed. Financial support by the University of Vienna and the Johanna Mahlke ne´e Obermann Foundation is gratefully acknowledged.

Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland 2 Departments of Clinical Research and Radiology, University of Bern, 3010 Bern, Switzerland A water soluble hexacationic Ruthenium complex [(p-cymene)6Ru6(tpt)2(dhnq)3](CF3SO3)6 with tri-pyridyl-triazene (tpt) and dihydroxy-naphthoquinone (dhnq) as bridging ligands was prepared and tested for its anticancer activity and interaction with potential biological targets [1]. The complex was found to be highly cytotoxic against human ovarian carcinoma cells (A2780) with an IC50 value of 0.45 lM. To learn more about the specificity and the mechanism of action, the effect of the complex on the metabolic profile of three different human cell lines was studied by high resolution magic angle spinning (HR-MAS) NMR spectroscopy. HR-MAS NMR allows obtaining well resolved 1H NMR spectra from living cell suspensions [2] well suited for chemometric analyses. Cisplatin-sensitive and -resistant cancer cells (A2780 and A2780cisR) as well as human embryonic kidney cells (HEK-293) as healthy model cells were each incubated with the Ru-complex for 24 and 72 h, respectively. The corresponding cell suspensions were submitted to HR-MAS NMR yielding a total of 104 1H NMR spectra of control and drug treated samples. Multivariate statistical analysis (PCA and PLS) of the spectra indicated clear metabolic changes between control and drug-treated cells for all 3 cell lines, as shown in the Figure for tincub = 24 h. The changes were most pronounced for A2780 cancer cells mainly due to lipids and choline containing compounds indicating potential drug-induced membrane breakdown. The single components responsible for the discrimination between all control and drug treated groups are discussed in more detail in this presentation. Financial supports by the University of Bern and SNF are gratefully acknowledged.

References 1. Kilpin KJ, Dyswon PJ (2013) Chem Sci 4:1410–1419 2. Nazarov AA, Hartinger CG, Dyson PJ (2013) J Organomet Chem 751:251–260

References 1. Paul LEH, Therrien B, Furrer J (2012) J Biol Inorg Chem 17:1053 2. Griffin JL, Bollard M, Nicholson JK, Bhakoo K (2002) NMR Biomed 15:375

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OP 3 Fluorescent ‘‘crowdoxidation’’ probes David G. Churchill1 1

Department of Chemistry (Molecular Logic Gate Laboratory), Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon, 305-701, Republic of Korea. [email protected] The chalcogens, as individual atoms, can be incorporated into the design of fluorescent (fluorogenic) molecules. Novel classes of fluorophores can be produced and exploited for, not only sensing, but also therapeutics and theranostics (e.g., GPx systems). So far, we have produced four different chalcogen-containing molecular motifs. A simple electron photoinduced electron transfer (PET) donor–acceptor design is utilized. The rotation of the electron donor is critical in fluorescence properties in these systems. Our laboratory has reported the first well-defined molecular probe involving chalcogen oxidation (benzothienyl–BODIPY) as the chemical switch for fluorescence/optical changes. It serves as the electron donor in a PET donor–acceptor design [1]. Our laboratory first reported a probe in which there are multiple sites of oxidation (multi-input) [2]. A total of four oxidation sites are possible here. Our laboratory first synthesized a BODIPY diselenide probe [3]. It is the second one, only, to behave as a reversible superoxide probe. This probe involves BODIPY–Phenyl–Se–Se–Phenyl–BODIPY attachments. The selenides are connected ortho in the electron receptor to maximize the impact on sterics. The sensitivity, selectivity, time response, cell studies, stability are all affirmative and decent, or excellent. In the process of repairing a diselenide probe for the non-substituted system, an unexpected reaction occurred. This is the first annulation product of its class [4]; importantly, it is the first chalcogen annulation product known for dipyrrins, or aryl-meso porphyrins, etc. The probe is an ‘‘off–on’’ fluorescent probe; it is reversible and \500 Da. The structure shows large mean planarity and rigidity; the uniquely-placed chalcogen atom is saddled halfway between the aryl ring and chromophore. This results in a red-shifted emission band molecule where, again, the molecule is kept small. Organoselenides also feature in a chelation site in a BODIPY conjugate in a recent paper devoted to modelling subsequent Fenton chemistry based on ferrous/ferric ion coordination and detection [5]. Financial support by the National Research Foundation of Korea and the Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science.

References 1. Choi SH, Kim K, Jeon J, Meka B, Bucella D, Pang K, Khatua S, Lee J, Churchill DG (2008) Inorg Chem 47:11071–11083 2. Singh AP, Mun Lee K, Murale DP, Jun T, Liew H, Suh Y-H, Churchill DG (2012) Chem Commun 48:7298–7300 3. Manjare ST, Kim S, Heo, WD, Churchill DG (2014) Org Lett 16:410–412 4. Manjare ST, Kim J, Lee Y, Churchill DG (2014) Org Lett 16:520–523 5. Murale DP, Manjare ST, Lee Y-S, Churchill DG (2014) Chem Commun 50:359–361

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OP 4 Sulfite oxidase: A paradigm for the mechanistic complexities and mysteries of metallo-enzymes with multiple domains, subunits and cofactors John H. Enemark, Gordon Tollin, Susan Borowski Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721 USA Human sulfite oxidase (hSO) is a complex enzyme that is essential for normal neonatal neurological development. Each of the two identical subunits of the homodimeric hSO protein possesses two domains that are linked by a flexible polypeptide tether. One domain contains the molybdenum cofactor and the other a b-type heme. The generally accepted catalytic mechanism for the oxidation of sulfite to sulfate by SO involves five different formal oxidation states for the Fe and Mo centers and both oxygen atom transfer and electron transfer processes. However, several recent studies of recombinant variants of hSO have produced seemingly paradoxical kinetic, structural and spectroscopic data that are not easily explained by previous mechanistic proposals. We have developed a comprehensive model for the catalytic mechanism of hSO that involves extensive inter-domain conformational changes of all five formal oxidation states of the Fe and Mo centers. This mechanistic model provides a framework for interpreting previous results on hSO and for planning future research. In addition, this model clearly shows that hSO is not just a medical curiosity related to a rare inherited disorder. Rather, hSO is an excellent example of a multi-cofactor, multi-subunit, multi-domain, multi-conformational state metallo-enzyme whose properties have broad and general importance for medicine and for bioinorganic chemistry.

OP 5 Molybdenum and tungsten enzyme’s active site models: some new developments in dithiolene chemistry Carola Schulzke1, Yulia B. Borozdina1, Christian Fischer1, Ashta Chandra Ghosh,1 Muhammad Zubair2 1

Institut fu¨r Biochemie, Ernst-Moritz-Arndt-Universita¨t Greifswald, Felix-Hausdorff-Str. 4, 17487 Greifswald, Germany 2 School of Chemistry, Trinity College Dublin, College Green, Dublin 2, Ireland. [email protected] Some new developments in dithiolene molybdenum model chemistry, in particular focusing on structural aspects of molybdopterin, will be presented. These are, for instance, synthesis, characterisation and reactivity of pyrane dithiolene complexes of molybdenum and tungsten and derivatives thereof. Chemical, electrochemical and catalytic properties were studied in comparison in order to further understand the role of the pyrane unit in molybdopterin. The pyrazine ring in combination with the dithiolene moiety has been addressed separately. Among intended outcomes of the various synthetic approaches, some unexpected and pleasantly surprising observations were made [1, 2]. These are for instance unusual binding motifs found crystallographically (e.g. dithiolene-sulfur hydrogen bonds, interactions involving the M=O moiety and packing motifs; Fig.), the discovery of a very mild synthetic route to pentathiepins and the unexpectedly facile oxidation of complexes by air.

J Biol Inorg Chem (2014) 19 (Suppl 2):S749–S764 Generous financial support by the ERC is gratefully acknowledged (project: MocoModels).

S751 formation of stable metal complexes despite the lack of any common strongly coordinating donor functions. In this work we demonstrate through the studies of the above mentioned peptides those tendencies which finely regulate the equilibrium, structural and electrochemical parameters of metal complexes. Acknowledgement: The research was supported by the EU and cofinanced by the European Social Fund under the project ENVIKUT ´ MOP-4.2.2.A-11/1/KONV-2012-0043) (TA References 1. Tima´ri S, Cerea R, Va´rnagy K (2011) J Inorg Biochem 105:1009–1017 ´ , Tima´ri S, Nagy EM, Sanna D, Garribba E, 2. Ka´llay C, Da´vid A Micera G, De Bona P, Pappalardo G, Rizzarelli E, So´va´go´ I (2011) Dalton Trans 40:9711–9721

References 1. Zubair M, Ghosh AC, Schulzke C (2013) Chem Commun 49:4343–4345 2. Do¨ring A, Fischer C, Schulzke C (2013) Z Anorg Allg Chem 639:1552–1558

OP 6 The role of side chains in the fine tuning of metal binding ability of peptides Katalin Va´rnagy, Gizella Csire, Sarolta Tima´ri, ´ gnes Da´vid, Csilla Ka´llay A Department of Inorganic and Analytical Chemistry, University of Debrecen, Egyetem te´r 1, 4032 Debrecen, Hungary. [email protected] It is well known that peptides have high metal binding affinity, but both the thermodynamic stability and the coordination geometry of peptide complexes are very much influenced by the amino acid sequence of the ligands. One field of our present research work is the synthesis and investigation of polypeptides containing various side chain donor groups, in which the coordination of side chain donor atoms comes to the front and their sequences serve as the models of different metalloproteins. These molecules include peptide fragments of Cu, Zn-superoxide dismutase enzyme and amylin which is a 37-residue peptide hormone cosecreted with insulin by pancreatic bcells [1, 2]. We synthesized such series of multihistidine peptides in which the systematic change of the amino acid sequence is carried out and the equilibrium, structural and electrochemical parameters of their complexes are determined. These molecules include oligopeptides built up from 4 to 12 amino acid residues containing 2–4 histidines among them. The thermodynamic, structural and electrochemical properties of these peptides are primarily determined by the number and location of histidyl residues. The presence of positively or negatively charged and polar or bulky side chains of other amino acids in the neighbourhood of the metal binding sites can, however, significantly contribute to the above mentioned parameters of these complexes. To understand the specific effects of these side chains aspartic acid, serine or phenylalanine are inserted into the sequence of the multihistidine peptides [Ac-(HisXaa)n-His, Xaa=Ala, Phe, Asp, Ser etc.]. On the other side, the studies of amylin fragments (-ValArgSerSerAsnAsn-) and their mutants reveal that the presence of more polar side chains (Ser, Asn etc.) in the peptide could result in the

OP 7 Transition metals alter the biological properties of dithiocarbamates: formation of metal complexes and the uses of metal–organic frameworks Raymond W.-Y. Sun1, Ming Zhang1, Shan Deng2, Alice S.-T. Wong3, Nikki P.-Y. Lee4 1

Department of Chemistry, Shantou University, No. 243 Daxue Road, Shantou, Guangdong 515063, People’s Republic of China. [email protected] 2 Department of Chemistry, 3 School of Biological Sciences and 4 Department of Surgery, The University of Hong Kong, Pokfulam Road, Hong Kong Various sulphur-containing molecules including dithiocarbamates and an anti-alcoholism agent disulfiram have shown promising in vitro and in vivo anti-cancer activities. Major hurdles in the development of these molecules include the stability, bioavailability, specificity, drug detoxification and cellular resistance accounting for by the direct binding of their active sulphurs to the thiol-containing peptides/proteins. Different metal ions and their coordination compounds present unique structural features and distinctive physical, chemical and biological properties, thus rendering them irreplaceable roles over common organic moieties in biological systems. By appropriate selection of coordinating metal ions, dithiocarbamates can be tuned and rationally designed to achieve different biological activities. Moreover, metal can be used to construct biologically-relevant metal– organic frameworks (MOFs). These materials can also be used as carriers to enhance the bioavailability of the encapsulated materials. In this work, we have demonstrated the alteration in physical properties and the anti-cancer/viral activities of various transition metalbased dithiocarbamato complexes compared to that of their corresponding dithiocarbamates. The encapsulating and sustained-release properties of MOFs render to these dithiocarbamates and their related complexes have also been reported. Financial supports by Shantou University (2013 NTF13005), General Research Fund (HKU 704812P), University Grants Committee of the Hong Kong Special Administrative Region are gratefully acknowledged.

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References 1. Zhang JJ, Lu W, Sun RWY, Che CM (2012) Angew Chem Int Ed 51:4882 2. Zhang JJ, Lok CN, Ng KM, Sun RWY, Che CM (2013) Chem Commun 49:5153–5155

OP 8 Ruthenium complexes of redox-active intercalating ligands as an emerging class of anti-cancer agents Frederick M. MacDonnell, Nagham Alatrash, Eugenia S. Narh Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, TX 76019, USA The clinical success of cisplatin in cancer therapy has demonstrated the tremendous potential of metal complexes as therapeutic agents, however despite decades of subsequent research only a handful of such metallodrugs exist, and most of these are simple derivatives of cisplatin. We have reported on a new class of ruthenium complexes which have low animal toxicity, good cytotoxicity and selectivity for malignant over normal cells and which show *83 % regression in H358 tumors implanted in nude mice compared to controls and a doubling of lifetime [1, 2]. This paper will focus on examining the mechanism of cytotoxicity which is correlated with their DNA cleaving properties. The key structural feature common to the most active complexes is the presence of a redox-active intercalating ligand (see figure below) which can be bioreduced in situ. One redox product is a reactive radical intermediate which is held in close juxtaposition with the DNA backbone, and ultimately responsible for DNA cleavage reaction. The pO2 is observed to affect the steady-state concentration of the radical in a manner which results in enhanced DNA cleavage as the pO2 is lowered. This has therapeutic implications as many tumor cells are often under hypoxic stress. Financial support by the Robert A. Welch Foundation (Y-1301) and US NCI-NIH is gratefully acknowledged. RAIL N

N

N

N

N

N

N N

N

N

N

N

N

N

N

N

= {Ru(diimine)22+ fragment

References 1. Yadav A, Janaratne T, Krishnan A, Singhal SS, Yadav S, Dayoub AS, Hawkins DL, Awasthi S, MacDonnell FM (2013) Mol Cancer Ther 12:643–653 2. Janaratne TK, Yadav A, Ongeri F, MacDonnell FM (2007) Inorg Chem 46:3420–3422

OP 9 Ferritin: another ‘dialogue concerning the two chief world systems’ Kourosh Honarmand-Ebrahimi, Peter-Leon Hagedoorn, Wilfred R. Hagen Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628BC Delft, The Netherlands. [email protected] Some four decades of intensive biochemical research on the ubiquitous iron storage protein ferritin has provided a wealth of structural,

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spectroscopic, kinetic, and thermodynamic data, from whose analysis in recent years a sub-molecular picture of the mechanism of action is beginning to emerge. Consensus, however, does not seem to be around the corner yet, although the spectrum of viewpoints at this time appears to condense into two well demarcated but mutually exclusive models: (1) the unifying proposal that all ferritins essentially work according to a single mode of operation (e.g. [1, 2]), versus (2) the diversifying proposal that different classes of ferritins exhibit fundamental differences in their respective mechanisms (e.g. [3, 4]). Drawing from Galileo’s format of a trialogue between two specialists and a layman to juxtapose arguments for/against Copernican and Ptolemaic systems [5] we will present the main sets of data and arguments for/against unifying and diversifying systems of ferritin action with sufficient contrast to allow the informed layman to take position. The debate centers around the question by what driving force—after catalytic oxidation—the two iron ions leave the ferroxidase center of ferritin en route to core formation in the protein’s cavity.

References 1. Honarmand-Ebrahimi K, Bill E, Hagedoorn P-L, Hagen WR (2012) Nat Chem Biol 8:941–948 2. Watts RK (2013) Chem Bio Chem 14:415–419 3. Turano P, Lalli D, Felli IC, Theil E, Bertini I (2010) Proc Natl Acad Sci USA 107:545–550 4. Bradley J, Moore GR, Le Brun NE (2014) J Biol Inorg Chem. doi: 10.1007/s00775-014-11363 5. Gallileo G (1632) ‘‘Dialogo sopra I due massimi sistemi del mondo’’ Landini Firenze

OP 10 Tuning the nuclease activity of macrocyclic copper complexes Jan Hormann1, Nora Kulak1 1

Institute of Chemistry and Biochemistry, Freie Universita¨t Berlin, Fabeckstr. 34/36, 14195 Berlin, Germany. [email protected] The cleavage of DNA is of high importance for biotechnological and therapeutic applications [1, 2]. The degradation of DNA in cancer cells is among the applications that could be carried out by so-called nucleases. Whereas there are a variety of natural enzymes available, as synthetic chemists we seek for small metal complexes that do the same job, but come with some advantages concerning stability, prize and accessibility to rational design. Some of the artificial metallonucleases used so far are based on the macrocyclic ligand cyclen (1,4,7,10-tetraazacyclododecane). Approaches for increasing the efficiency of such metallonucleases comprise the design of multinuclear metal complexes and the attachment of DNA intercalators and positively charged residues to the ligand moiety in order to increase the affinity to DNA [3]. We show here, that the exchange of one of the nitrogen atoms in the cyclen ligand by oxygen (oxacyclen) or sulfur (thiacyclen) has an

J Biol Inorg Chem (2014) 19 (Suppl 2):S749–S764 important impact on the oxidative cleavage activity of its copper complexes (O [ S [ N) [4]. Recent results are also presented to show that further derivatization in the ligand’s donor set and periphery leads to an increase in efficiency. The knowledge acquired during these studies allows us now to tune the nuclease properties of cyclen copper complexes. Financial support by the Deutsche Forschungsgemeinschaft (DFG) is gratefully acknowledged. References 1. Hormann J, Perera C, Kulak N (2013) Nachr Chem 61:1003–1006 2. Wende C, Lu¨dtke C, Kulak N (2014) Eur J Inorg Chem (in press). doi:10.1002/ejic.201400032 3. Mancin F, Scrimin P, Tecilla P (2012) Chem Commun 48:5545–5559 4. Hormann J, Perera C, Deibel N, Lentz D, Sarkar B, Kulak N (2013) Dalton Trans 42:4357–4360

OP 11 DNA-interacting molecular switches Andreu Presa1, Guillem Va´zquez1, Patrick Gamez1,2 1

Departament de Quı´mica Inorga`nica, Facultat de Quı´mica, Universitat de Barcelona, Martı´ i Franque`s 1-11, 08028 Barcelona, Spain. [email protected] 2 Institucio´ Catalana de Recerca i Estudis Avanc¸ats (ICREA), Passeig Lluı´s Companys 23, 08010 Barcelona, Spain Photoactivated chemotherapy drugs provide the prospect to achieve highly controllable activity with reduced side effects [1]. Photoactivation of coordination compounds are commonly based on metalcentred processes [2]. Dithienylcyclopentene (DTE) molecules undergo thermally irreversible cyclization reactions between colourless (open) and coloured (closed) forms when stimulated with UV and visible light (see figure) [3]. This closing/opening event gives rise to a contraction or expansion of the molecule, respectively. For instance, the distance between the methyl groups in 1,2-bis(2,5-dimethyl(3-thienyl))-3,3,4,4,5,5˚ upon ring closure hexafluorocyclopent-1-ene decreases by 1.138 A (figure). In this presentation, a series of photoswitching metal complexes obtained from DTE-based ligands will be described together with their properties. Actually, in addition to the expected distinct optical properties, the open and closed forms of such coordination compounds exhibit different DNA-interacting properties. Financial support by the Ministerio de Economı´a y Competitividad (MINECO) of Spain (Project CTQ2011-27929-C02-01). COST Action CM1105 is kindly acknowledged.

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OP 12 Reversible transformation between cuboidal Fe4S4 and dinuclear Fe2S2 cores Kazuki Tanifuji, Kazuyuki Tatsumi, Yasuhiro Ohki Research Center for Materials Science, and Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan Splitting of the [Fe4S4] cluster core into two [Fe2S2] fragments has not been realized in synthetic inorganic chemistry. On the other hand, it has been proposed that the [Fe4S4] cubane in the fumarate nitrate reductase regulatory protein is transformed to dinuclear [Fe2S2] cores under O2, while the protein dissociates DNA [1]. A similar oxidative decomposition of [Fe4S4] in Nif-IscA was postulated to occur generating [Fe2S2] cores [2]. In this presentation, we show a series of reactions displaying interconversion between [Fe4S4] and [Fe2S2] core structures based on the preformed all-ferric [Fe4S4]4+ cluster, [Fe4S4{N(SiMe3)2}4] (1). Treatment of 1 with excess pyridine (py) or pyridine derivatives (py-R) resulted in splitting of the cubane core to [Fe2S2{N(SiMe3)2}2(py-R)2] (2). The 1H NMR spectra of the dinuclear products 2 in C6D5Cl show presence of 1 and py-R, indicating that 2 and 1 are in equilibrium in solution. Conversely, fusion of two [Fe2S2] cores of 2 was found to be facilitated by B(C6F5)3, generating [Fe4S4{N(SiMe3)2}4] (1) and (Py-R)B(C6F5)3. [Fe4S4] cores with lower oxidation states were formed by chemical reduction of cluster 2. Treatment of 2 with 1.2 equiv of Na[C10H8] in THF afforded [Fe4S4{N(SiMe3)2}4]2- (3), while an analogous reaction of 2 with 0.5 equiv of Na[C10H8] gave rise to [Fe4S4{N(SiMe3)2}4]- (4). Interestingly, while the reduced forms of [Fe4S4] clusters, 3 and 4, are intact in the presence of excess pyridine, the addition of excess oxidant ([Cp2Fe]+) to the reaction systems readily gave [Fe2S2{N(SiMe3)2}2(py-R)2] (2), presumably via formation of all-ferric [Fe4S4{N(SiMe3)2}4] (1). Thus, the all-ferric [Fe4S4]4+ state is essential for dissociation of [Fe4S4] into [Fe2S2].

References 1. Popescu C, Bates DM, Beinert H, Mu¨nck E, Kiley PJ (1998) Proc Natl Acad Sci USA 95:13431–13435. 2. D. T. Mapolelo DT, Zhang B, Naik SG, Huynh BH, Johnson MK (2012) Biochemistry 51:8071–8084

OP 13 Conversion of readout from transcriptional regulator by electron transfer proteins Hiroshi Nakaijma1, Souji Miyazaki2, Takaaki Itoh1, Yoshihito Watanabe2 1

References 1. Farrer NJ, Salassa L, Sadler PJ (2009) Dalton Trans 10690–10701 2. Szaciłowski K, Macyk W, Drzewiecka-Matuszek A, Brindell M, Stochel G (2005) Chem Rev 105:2647–2694 3. Feringa BL (ed) (2001) Molecular switches. Wiley-VCH, Weinheim

Department of Chemistry, Nagoya University, Chikusa-ku, 464-8602, Nagoya, Japan 2 Reseach Centre of Materials Science, Nagoya University, Chikusa-ku, 464-8601, Nagoya, Japan. [email protected] In a biological system there are various transcriptional regulator proteins which evolved to detect environmental factors, control appropriate biological events, and retain the homeostasis of living

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S754 cells at the transcriptional level. The high, specific sensitivity of these proteins is attractive for constructing novel bio-based sensor modules. However, facile conversion of the biological readout from the protein to a readily detectable signal is a major issue to be solved before application. We have recently developed a signaltransducing mechanism consisting of a pair of electron transfer (ET) proteins [azurin and cytochrome c (Cyt c)] and a stimulus responsive molecule that was introduced at the hydrophobic surface of azurin so as to modulate inter-proteins interaction and the subsequent ET step in the stimulus dependent manner [1]. In this study, we show application of the signal-transducing mechanism to a transcriptional regulator (figure). Thereby, the readout from the regulator is converted to a change in the apparent ET rate between the ET proteins [2]. The hydrophobic surface of azurin was chemically modified with a double stranded oligo-DNA (DNA-Azu) that contains a recognition sequence of a carbon monoxide (CO) dependent transcriptional regulator, CooA [3]. CooA showed reversible binding to DNA-Azu, depending on CO. The apparent ET rate constant (kET) for Cyt c and DNA-Azu was determined to be 6.2 9 104 M-1 s-1, which was 16 folds smaller than that for Cyt c and wild type azurin (1.0 9 106 M-1 s-1) [1], likely due to steric and electrostatic hindrance of DNA. The CooA binding to DNA-Azu partially recovered the ET rate (5.0 9 105 M-1 s-1). We will discuss this behavior and possible application to a modified electrode. We gratefully acknowledge financial support by MEXT, Japan.

References 1. Rosenberger N, Studer A, Takatani N, Nakajima H, Watanabe Y (2009) Angew Chem Int Ed 48:1946–1949 2. Nakajima H, Miyazaki S, Itoh T, Hayamura M, Watanabe Y (2014) Chem Lett (in press) 3. Thorsteinsson MV, Kerby RL, Conrad M, Youn H, Staples CR, Lanzilotta WN, Poulos TJ, Serate J, Roberts GP (2000) J Biol Chem 275:39332–39338

OP 14 Contribution of each Trp residue towards the intrinsic fluorescence of the Gia1 protein Duarte Mota de Freitas, Matthew S. Najor, Kenneth W. Olsen, Daniel J. Graham Department of Chemistry and Biochemistry, Loyola University Chicago, USA Gia1 is the inhibitory G-protein that, upon activation, reduces the activity of adenylyl cyclase. Comparison of the crystal structures of Gia1 bound to GDP•AMF or GTPcS with that of the inactive, GPDbound protein indicates that a conformational change occurs in the activation step centered on three switch regions. The contribution of each tryptophan residue (W211 in the switch II region, W131 in the ahelical domain, and W258 in the GTPase domain) toward the intrinsic protein fluorescence was evaluated by using W211F, W131F and

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J Biol Inorg Chem (2014) 19 (Suppl 2):S749–S764 W258F mutants. Regardless of the conformation, all three tryptophan residues contributed significantly toward the emission spectra. When activated by either GDP•AMF or GTPcS, the maximal fluorescence scaled according to the solvent accessibilities of the tryptophan residues, calculated from molecular dynamics simulations. In the GDP•AMF and GTPcS, but not in the GDP, conformations, the residues W211 and R208 are in close proximity and form a p-cation interaction that results in a red shift in the emission spectra of WT, and W131F and W258F mutants, but a blue shift for the W211F mutant. The observed shifts did not correlate with the span of the W211-R208 bridge but rather with the electrostatic energy of the interactions in the various proteins. Trypsin digestion of the active conformations only occurred for the W211F mutant indicating that the electrostatic p-cation interaction blocks access to R208, which was consistent with the molecular dynamics simulations. We therefore conclude that solvent accessibility and electrostatic interactions account for the fluorescence features of Gia1.

OP 15 Label-free DNA-based biosensing using luminescent metal complexes Dik-Lung Ma Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong. [email protected] Oligonucleotides represent a versatile sensing platform due to their ease of synthesis, sensitivity to particular analytes, low cost and robust stability [1, 2]. Interest in DNA-based detection has exploded in the scientific literature over the last few years. In particular, the use of luminescent metal complexes as signal transducers in label-free DNA sensing holds great promise as they are highly sensitive to changes in the local environment, making them suitable to monitor the DNA-switching event. Moreover, the application of luminescent metal complexes in DNA sensing could further reduce the cost of assay compared to the use of fluorescently-labelled oligonucleotides. Transition heavy metal complexes possess salient advantages that render them suitable for sensing applications: (1) their long emission life-time allows their phosphorescence to be distinguished in highly fluorescent media with the use of time-resolved spectroscopy, (2) they usually display significant Stokes shifts which can prevent selfquenching, and (3) their interaction with biomolecules and their photophysical properties can be readily tuned without lengthy synthetic procedures [3]. In this poster, I will present continuing progress in the field of ‘‘label-free’’ luminescent based detection platform for a variety of biologically and environmentally important analytes based on oligonucleotides and luminescent metal complexes from our research group.

J Biol Inorg Chem (2014) 19 (Suppl 2):S749–S764 References 1. Du Y, Li B, Wang E (2012) Acc Chem Res 46:203–213 2. Ma DL, He HZ, Leung KH, Zhong HJ, Chan DSH, Leung CH (2013) Chem Soc Rev 42:3427–3440 3. Zhao Q, Huang C, Li F (2011) Chem Soc Rev 40:2508–2524

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OP 17 pH dependence of amyloid-b–Cu(II) binding and oligomerization kinetics Jeppe T. Pedersen1, Christian B. Borg2, Kaare Teilum2, Lars Hemmingsen3 1

OP 16 Copper(II), nickel(II) and zinc(II) binding ability of the N-terminal fragments of amyloid-b peptide ´ gnes Grena´cs Imre So´va´go´, A Department of Inorganic and Analytical Chemistry, University of Debrecen, 4010 Debrecen, Hungary Amyloid-b is a 40–43 residue peptide responsible for the development of Alzheimer’s disease. The N-terminus of the peptide is reach in histidyl residues and contains some other polar side chains which enhance the metal binding ability of the peptide. Speciation and characterization of the copper(II), nickel(II) and zinc(II) complexes of the N-terminal hexadecapeptide fragment, Ab(1–16)-PEG, have already been reported in our previous publications [1] but the elucidation of the metal binding sites requires further studies. In this work we report the synthesis of two nonapeptide domains of the native peptide: Ab(1–9) and Ab(8–16) and their mutants. The sequences of the six peptides studied are NH2-DAEFRHDSG-NH2, NH2-DAAAAHAAA-NH2 and NH2-DAAAAAHAA-NH2 for Ab(1–9) and Ac-SGAEGHHQK-NH2, Ac-SGAEGHAQK-NH2 and Ac-SGAEGAHQK-NH2 for Ab(8–16). The results obtained from combined potentiometric and spectroscopic (UV–vis, CD, ESR, NMR and ESI–MS) studies will be presented here. Both thermodynamic and structural data support the primary role of the amino termini of peptides in copper(II) and nickel(II) binding. Moreover, it can be unambiguously stated that the amino acid sequence of the N-terminal domains of amyloid peptides is especially well suited for the complexation with copper(II) ions as it is represented by the figure showing the distribution of copper ions among the native and two mutant peptides. The enhanced stability of the copper(II) complexes was attributed to the secondary interactions of the polar side chains of Asp, Glu, Ser and Arg residues present in the native peptides.

Department of Pharmacy, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark. [email protected] 2 Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, 2200 Copenhagen, Denmark 3 Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark Extracellular aggregation of amyloid-b peptides (Ab) is implicated in the pathogenesis of Alzheimer’s disease. Metal ions such as Cu(II) can promote aggregation of Ab on the millisecond–second time scale upon binding [1, 2]. Hence, aberrant metal–Ab interaction may play a role in development of AD. It is well-established that there are multiple coordination states of Cu(II) in soluble Ab and the different states co-exist in a dynamic equilibrium depending on the pH [3,4]. It is reasonable to think that distinct Ab–Cu(II) species could have distinct oligomerization propensity. Here, we study the Cu(II) binding mechanism to Ab and the subsequent oligomerization at different pH using stopped-flow fluorescence and light scattering in combination with NMR relaxation. Financial support by the Villum Foundation is gratefully acknowledged.

References 1. Noy D, Solomonov I, Sinkevich O, Arad T, Kjaer K, Sagi I (2008) J Am Chem Soc 130:1376–1383 2. Pedersen JT, Teilum K, Heegaard NHH, Østergaard J, Adolph H-W, Hemmingsen L (2011) Angew Chem Int Ed 50:2532–2535 3. Drew SC, Noble CJ, Masters CL, Hanson GR, Barnham KJ (2009) J Am Chem Soc 131:1195–1207 4. Dorlet P, Gambarelli S, Faller P, Hureau C (2009) Angew Chem Int Ed 48:9273–9276

β

OP 18 Probing the efficacy of novel bismuth (III and V) complexes as anti-leishmanial agents Philip C. Andrews,1 Lukasz Kedzierski,2 Yih Ching Ong1 1

The research was supported by EU and co-financed by the European Social Fund under the project ENVIKUT (TAMOP-4.2.2.A-11/ 1/KONV-2012-0043). Reference 1. Arena G, Pappalardo G, So´va´go´ I, Rizzarelli E (2012) Coord Chem Rev 256:3–12

School of Chemistry, Monash University, Melbourne, VIC 3800, Australia. [email protected] 2 Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Melbourne, Australia Even after 70 years, Leishmaniasis, the deadly parasitic disease endemic in various forms across the developing world, is treated primarily with two Sb(V) compounds; sodium stibogluconate and meglumine antimoniate [1]. While effective, these drugs have significant problems; treatment for visceral leishmania requires intravascular or intramuscular injections daily for 28 days under strict medical monitoring, and intracellular reduction processes involving

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S756 trypanothione produce active Sb(III) which is both highly toxic and biodistributed [2]. Alternative drugs amphotericin B and pentamidine are expensive and do not overcome the need for parenteral administration or reduce the onset of severe side effects, and miltefosine, while orally active, is also expensive and teratogenic [3]. Bismuth and its compounds are considered to have low systemic toxicity in humans, while showing good antimicrobial activities. In this context, we have been examining and assessing novel organometallic and metal–organic Bi(III) and highly oxidising Bi(V) compounds for their anti-leishmanial activity and toxicity towards human fibroblasts. This has involved synthesis using a range of ligand classes (e.g. carboxylates, thiocarboxylates, thioamides, thioxoketonates, hydroxamates), full characterisation, including crystal structures, and an examination of stability in aqueous and biological environments [4]. In this presentation we will report our most recent results in the chemistry and biological assays, demonstrating the potential of bismuth compounds in treating leishmaniasis.

References 1. Kedzierski L, Sakthianandeswaren A, Curtis JM, Andrews PC, Junk PC, Kedzierska K (2009) Curr Med Chem 16:599–614 2. Demicheli C, Fre´zard F (2005) Drug Design Reviews-Online 2:243–249 3. Richard JV, Werbovetz KA (2010) Curr Opin Chem Biol 14:447 4. Andrews PC, Junk PC, Kedzierski L, Peiris, RM (2013) Aus J Chem 13:6276–6279.

OP 19 Searching for new aromatic amine N-oxide metal complexes as prospective agents against infectious diseases Esteban Rodrı´guez1, Ignacio Machado1, Leonardo Biancolino Marino2, Florencia Mosquillo3, Leticia Pe´rez3, Clarice Q. F. Leite2, Fernando R. Pavan2, Lucı´a Otero1, Dinorah Gambino1 1

Ca´tedra de Quı´mica Inorga´nica, Facultad de Quı´mica, Universidad de la Repu´blica, Gral. Flores 2124, 11800 Montevideo, Uruguay 2 Facultade de Ciencias Farmaceuticas, Unesp, 14801-902 Araraquara (SP), Brazil 3Laboratorio de Interacciones Moleculares, Facultad de Ciencias, Universidad de la Repu´blica, Igua´ 4225, 11400 Montevideo, Uruguay Infectious diseases are major causes of human disease worldwide. Despite the progress in efforts to control the spread of tuberculosis, this ancient and currently re-emerging infectious disease still remains a global public health issue. Chagas disease (American Trypanosomiasis) is a chronic infection caused by the protozoan parasite

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J Biol Inorg Chem (2014) 19 (Suppl 2):S749–S764 Trypanosoma cruzi that affects about 10 million people in Latin America. Current chemotherapy for both diseases is inadequate and new strategies for the discovery of new drugs are needed. Our group is focused on the development of prospective metal-based drugs mainly based on bioactive ligands and pharmacologically active metals. As part of this work, we had previously developed Pd(II), Pt(II) and Au(I) complexes of pyridine-2-thiol N-oxide (Hmpo). The ligand blocks T. cruzi’s growth affecting all stages of the life cycle of the parasite and showing low IC50 values. The complexes showed high antitrypanosomal activities with adequate selectivity indexes. Results suggested that the trypanocidal action of the complexes could mainly rely on the inhibition of the parasite-specific enzyme NADH fumarate reductase, main known parasite target for the free ligand. In the search for new metal-based therapeutic tools against tuberculosis and Chagas disease, and to further address the therapeutic potential of mpo metal complexes, two new octahedral [MIII(mpo)3] complexes, with M = Ga or Bi, and two new Pd(II) and Pt(II) heterobimetallic compounds [MII(L)(mpo)](PF6), with L = ferrocene derivative, were synthesized and characterized in the solid state and in solution. The compounds showed excellent activity, both on the standard M. tuberculosis strain H37Rv ATCC 27294 (pansusceptible) and on five clinical isolates that are resistant to the standard first-line anti-tuberculosis drugs isoniazid and rifampicin. In addition, the complexes showed an enhancement of the anti-T. cruzi activity compared with the parent compound. These new derivatives are highly promising for the development of prospective agents for the treatment of resistant tuberculosis and/or Chagas disease. References 1. Vieites M, Smircich P, Guggeri L, Marcha´n E, Go´mez-Barrio A, Navarro M, Garat B, Gambino D (2009) J Inorg Biochem 103:1300–1306 2. Vieites M, Smircich P, Parajo´n-Costa B, Rodrı´guez J, Galaz V, Olea-Azar C, Otero L, Aguirre G, Cerecetto H, Gonza´lez M, Go´mezBarrio A, Garat B, Gambino D (2008) J Biol Inorg Chem 13:723–735

OP 20 The role of covalent heme to protein bonds in the formation and reactivity of redox intermediates of a bacterial peroxidase with high homology to human peroxidases Paul G. Furtmu¨ller1, Markus Auer1, Andrea Nicolussi1, Georg Schu¨tz1, Marzia Bellei2, Gianantonio Battistuzzi2, Christian Obinger1 1

Department of Chemistry, Division of Biochemistry, VIBT-Vienna Institute of BioTechnology, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria. [email protected] 2Department of Chemistry and Geology, University of Modena and Reggio Emilia, 41100 Modena, Italy Reconstructing the phylogenetic relationships of the evolutionary lines of the mammalian peroxidases revealed the presence of novel bacterial heme peroxidase subfamilies [1]. Recently, an ancestral bacterial heme peroxidase of the peroxidockerin clade was shown to possess halide oxidation activities similar to human peroxidases. Moreover, the recombinant protein allowed monitoring of the autocatalytic (i.e. hydrogen peroxide-driven) formation of covalent heme to protein bonds (which are also found in vertebrate peroxidases [2]. Here, for the first time, the direct impact of the covalent heme to protein bonds on the formation and reactivity of all relevant redox intermediates of this peroxidase is demonstrated by transient kinetic

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measurements. Protein species with covalently bound heme were compared with those having predominantly unmodified heme b. We report the kinetics of binding of the low-spin ligand cyanide and demonstrate the strong influence of this posttranslational modification on the redox reactions including formation of Compound I by hydrogen peroxide as well as two- and one-electron reduction reactions of Compound I to either the ferric enzyme or Compound II. The presented data are discussed with respect to the known crystal structures and kinetic data available from mammalian peroxidases. This research was supported by the Austrian Funding Fund (FWFstand-alone project P20664 and the doctoral program BioToP- Biomolecular Technology of Proteins W1224).

3. Hofbauer S, Gysel K, Mlynek G, Kostan J, Hagmu¨ller A, Daims H, Furtmu¨ller PG, Djinovic-Carugo K, Obinger C (2012) Biochim Biophys Acta Proteins Proteomics 1824:1031–1038 4. Hofbauer S, Bellei M, Su¨ndermann A, Pirker KF, Hagmu¨ller A, Mlynek G, Kostan J, Daims H, Furtmu¨ller PG, Djinovic´-Carugo K, Oostenbrink C, Battistuzzi G, Obinger C (2012) Biochemistry 51:9501–9512 5. Hofbauer S, Gysel K, Bellei M, Pirker KF, Hagmu¨ller A, Schaffner I, Mlynek G, Kostan J, Daims H, Furtmu¨ller PG, Battistuzzi G, Djinovic-Carugo K, Obinger C (2014) Biochemistry 53:77–89 6. Hofbauer S, Schaffner I, Furtmu¨ller PG, Obinger C (2014) Biotechnol J 9:461–473

References 1. Zamocky M, Jakopitsch C, Furtmu¨ller PG, Dunand C, Obinger C (2008) Proteins 71:589–605 2. Auer M, Gruber C, Bellei M, Pirker KF, Zamocky M, Kroiss D, Teufer SA, Hofbauer S, Soudi M, Battistuzzi G, Furtmu¨ller PG, Obinger C (2013) J Biol Chem 288:27181–27199

OP 22 Metal mobilization from waste hydroxide sludge by sulfur oxidizing bacteria Helmut Brandl1, Carlotta Fabbri1, Thomas Wu¨thrich2 1

1

Department of Chemistry, Division of Biochemistry, Department for Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria 3 Department of Chemistry and Geology, University of Modena and Reggio Emilia, 41125 Modena, Italy Chlorite dismutases (Clds) are oligomeric heme b-dependent oxidoreductases capable of catalyzing the conversion of chlorite (ClO2-) into chloride and dioxygen (designation as ‘‘dismutase’’ is wrong and should be eliminated in future). This presentation compares two model Clds [1–3] from the two main lineages that differ in oligomeric structure and subunit architecture. Here, we compare the available X-ray structures and discuss the role of conserved heme cavity residues in maintenance of the active site architecture as well as in catalysis [4, 5]. A reaction mechanism is presented that underlines the important role of the highly conserved distal arginine in keeping the transiently formed intermediate hypochlorous acid in the reaction sphere for recombination with the oxoiron(IV) of Compound I. In this reaction a covalent oxygen–oxygen bond is formed and O2 is released. Finally, we discuss the close phylogenetic relationship between Clds and recently discovered dye-decolorizing peroxidases [6]. Our research was supported by the Austrian Funding Agency (FWF-doctoral program BioToP-Biomolecular Technology of Proteins, W1224 and the stand alone project P25270). 2

References 1. Kostan J, Sjoeblom B, Maixner F, Mlynek G, Furtmu¨ller PG, Obinger C, Wagner M, Daims H, Djinovic-Carugo K (2010) J Struct Biol 172:331–342 2. Mlynek G, Sjo¨blom B, Kostan J, Fu¨reder S, Maixner F, Gysel K, Furtmu¨ller PG, Obinger C, Wagner M, Daims H, Djinovic-Carugo K. (2011) J Bacteriol 193:2408–2417

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OP 21 Chlorite to chloride and O2 conversion: new lessons from structural and mechanistic investigations of chlorite dismutase Christian Obinger1, Stefan Hofbauer1, Irene Schaffner1, Katharina F. Pirker1, Georg Mlynek2, Kristina Djinovic-Carugo2, Gianantonio Battistuzzi3, Paul G. Furtmu¨ller1

Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland 2ALAB AG, In der Luberzen 5, 8902 Urdorf, Switzerland When applying biological techniques (‘‘biohydrometallurgy’’) in the mining of valuable metals such as copper and gold (‘‘bioleaching’’, ‘‘biomining’’), sulfur oxidizing microorganisms play a fundamental role [1]. Sulfur oxidizers belong to the group of acidophilic microbes, thrive on carbon dioxide, and form sulfuric acid as end product of their metabolism resulting in the mobilization of elements from solid materials. However, when treating metal-containing industrial waste, high salt content along with high alkalinity might inhibit these acidloving microbes. Therefore, we investigated the physiological potential of Halothiobacillus neapolitanus for the mobilization of metals from waste hydroxide sludge originating from flue gas purification. H. neapolitanus is salt tolerant and metabolically active over a pH range of 4–8.5 (with an optimum between 6.5 and 7), which seems to be ideal for the biological treatment of alkaline waste materials. Within a growth period of 10 days in a suspension of 10 g sludge per liter, pH values dropped from 7 to 3.4. It was possible to solubilize certain metals completely (e.g., Cd, Zn), whereas others were mobilized to a smaller extent (e.g. Pb 30 %, Cu 50 %). Zn was the major constituent (*95 %) of the leachate. By gradually increasing bulk density, H. neapolitanus adapted to suspensions of 30 g sludge per liter. In summary, results showed that H. neapolitanus can cope with alkaline salt-containing waste materials and mobilize some metals to a high extent. In perspective, this might be the base for a biological recovery of metals from hydroxide sludge, all the more because the selective environment (high salt and metal content, low pH) might allow a biological treatment of wastes under non-sterile conditions.

60 40 20 0 Al

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S758 Reference 1. Brandl H (2001) In: Rehm HJ (ed) Biotechnology, vol 10. WileyVCH, Weinheim, pp 191–224

OP 23 Hydride binding to the active-site H-cluster of [FeFe]hydrogenase Petko Chernev1, Camilla Lambertz2, Nils Leidel1, Kajsa Sigfridsson1, Ramona Kositzki1, Thomas Happe2, Michael Haumann1 1

Department of Physics, Free University Berlin, Arnimallee 14, 14195 Berlin, Germany. [email protected] 2 Institute for Biochemistry of Plants, Department of Photobiotechnology, Universita¨tsstrasse 150, Ruhr-University Bochum, 44801 Bochum, Germany [FeFe]-hydrogenase from green algae (HydA1) is the most efficient enzyme for hydrogen (H2) production in nature. Its active site is a unique six-iron center (H-cluster) composed of a [4Fe4S]H cluster linked to a diiron unit, [2Fe]H. The molecular and electronic configurations of the H-cluster need to be determined to understand the specific restraints for high-rate H2 production to be implemented in novel synthetic catalysts. We have probed the electronic configuration of the H-cluster in purified HydA1 protein using site-selective X-ray absorption and emission spectroscopy experiments for the first time [1, 2]. This has provided novel and distinct spectroscopic signatures, which were reproduced and interpreted by quantum chemical calculations (DFT), thereby leading to specific H-cluster model structures. The electronic configuration of several redox intermediates thus was determined. We show that iron-hydride bonds are absent in the oxidized and one-electron reduced states of the H-cluster. Only in the two-electron (super-)reduced state an ironhydride bond could be directly detected. The hydride binding possibly occurs to the Fe–Fe bridging position at [2Fe]H. These results suggest a catalytic cycle of [FeFe]-hydrogenases with at least three main intermediates, involving protonation, hydride binding, and electron transfer steps prior to the H2 formation chemistry. Our methods open a new perspective for characterization of metalhydride species in (bio)inorganic chemistry. MH acknowledges financial support by the DFG (Grants Ha3265/ 2-2,/3-1, and/6.1), the BMBF (Grant 05K14KE1 within the Ro¨ntgenAngstro¨m Cluster), and Unicat (CoE Berlin).

References 1. Chernev P, Lambertz C, Sigfridsson K, Leidel N, Kositzki R, Hsieh C, Schiwon R, Yao S, Limberg C, Driess M, Happe T, Haumann M (2014) manuscript submitted 2. Lambertz C, Chernev P, Klingan K, Leidel N, Sigfridsson K, Happe T, Haumann M (2014) Chem Sci 5:1187–1203

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OP 24 Probing the electron transfer mechanism of diironcarbonyl complexes relevant to the diiron sub-unit of [FeFe]-hydrogenase Guifen Qian2, Zhinyin Xiao1, Li Long1, Xiaoming Liu1, 2 1

College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing, 314001 Zhejiang, China 2 Department of Chemistry, Nanchang University, Nanchang, 330031 Jiangxi, China. [email protected] [FeFe]-hydrogenase and its mimicking chemistry have attracted a great deal of attentions since its structural revelation about 15 years ago due to its relevance to hydrogen energy, a promising energy vector in future. Under physiological conditions, this enzyme catalyses hydrogen evolution with zero-overpotential. It is appealing to understand the intrinsic chemistry behind this feature. The confirmation of azodithiolate as the bridge of the diiron centre suggests that PCET contributes certainly to decrease the overpotential [1]. Since either evolution or oxidation of hydrogen, two-electron per molecule is involved. Therefore, there ought to be other explanation for the zero-overpotential. Electrochemical investigations into the mimics of the diiron sub-unit show that the reduction of the diironcarbonyl complexes may involve two-electron process despite a single reduction wave observed often in their cyclic voltammograms, that is, involving potential inversion caused by isomerisation upon reduction [2]. By incorporating a ferrocenyl group into the mimics to calibrate the number of electron [3], the ECE process is clearly demonstrated and it is concluded that the inversed potential (E2) can not be more positive than the first potential (E1). In conclusion, PCET and the potential inversion are the main causes for the zero-overpotential of the enzymatic catalysis in hydrogen evolution. Financial support by Natural Science Foundation of China is gratefully acknowledged.

References 1. Berggren G, Adamska A, Lambertz C, Simmons TR, Esselborn J, Atta M, Gambarelli S, Mouesca JM, Reijerse E, Lubitz W, Happe T, Artero V, Fontecave M (2013) Nature 299:66–70 2. Lounissi S, Zampella G, Capon JF, De Gioia L, Matoussi F, Mahfoudhi S, Petillon FY, Schollhammer P, Talarmin J (2012) Chem Eur J 18:11123–11138 3. Zeng X, Li Z, Xiao Z, Wang Y, Liu X (2010) Electrochem Commun 12:342–345

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OP 25 M–Purine(C8) constructs and their potential applications in catalysis Pablo J. Sanz Miguel, Andrea Cebollada, Alba Velle´

OP 26 Geometric and electronic structures of 5d metallocorroles: Au, Pt, Os Abhik Ghosh

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Department of Chemistry, UiT-The Arctic University of Norway, 9037 Tromsø, Norway. [email protected] Because of the size mismatch between the contracted N4 cores of corroles and the large ionic radii of the 5d transition metals in their lower oxidation states, the synthesis of 5d metallocorroles has been a challenge for synthetic coordination chemists [1]. Against this backdrop, gold corroles were synthesized recently and, in as yet unpublished work in our laboratory, the first platinum and osmium corroles have been synthesized. The work provides fascinating examples of synthetic strategy, heavy-element mediated C–H activation, and ligand noninnocence, the last perhaps best exemplified by a series of oxidized Pt corroles with the formula Pt(corrole•2-)ArAr0 . A representative crystal structure is shown below. The potential anticancer properties of the Pt complexes are currently being examined.

Departamento de Quı´mica Inorga´nica, Instituto de Sı´ntesis Quı´mica y Cata´lisis Homoge´nea (ISQCH), Universidad de Zaragoza-CSIC, 50009 Zaragoza (Spain). [email protected] Coordination of transition metals to the imidazolic positions of purines or their derivatives has been widely studied in the cases of the N7 and N9 sites [1], but only scarcely for C8. There are few examples of metal coordination to the C8 sites of N7,N9-methylated purines [2]. Houlton et al. prepared several C8-coordinated metal complexes with purines by cyclometallation [3], with N7/N9 available for metal coordination. In addition, only three examples of caffeine as C8monodentate ligand for Os, Ru, and Co have been reported [4]. Our interest on C8-coordination of transition metals at purines is grounded on their analogy with the N-heterocyclic carbene ligands, commonly employed in catalysis. We report on the first examples of twofold metal coordination to both the C8 and N9 sites of purines, including examples of (1) catalytic active Mn(purine-C8)n cyclic compounds, and (2) a stepwise formation strategy of a Pt4,Pd4,Ag2 aggregate in which its central skeleton is supported by dative bonds and strong intermetallic interactions [5]. Financial support by the Spanish Ministerio de Economı´a y Competitividad (CTQ2011-27593, and Ramo´n y Cajal Program) is gratefully acknowledged.

References 1. See e.g.: (a) Lippert B (2000) Coord Chem Rev 200–202:487–516; (b) Houlton A (2002) Adv Inorg Chem 53:87–158 2. (a) Kascatan-Nebioglu A, Panzner MJ, Garrison JC, Tessier CA, Youngs WJ (2004) Organometallics 23:1928–1931; (b) Skander M, Retailleau P, Bourrie B, Schio L, Mailliet P, Marinetti A (2010) J Med Chem 53:2146–2154; (c) Stefan L, Bertrand B, Richard P, Le Gendre P, Denat F, Picquet M, Monchaud D (2012) ChemBioChem 13:905–912 3. See e.g.: (a) Price C, Elsegood MRJ, Clegg W, Rees NH, Houlton A (1997) Angew Chem Int Ed 36:1762–1764; (b) Price C, Shipman MA, Rees NH, Elsegood MRJ, Edwards AJ, Clegg W, Houlton A (2001) Chem Eur J 7:1194–1201 4. (a) Krentzien HJ, Clarke MK, Taube H (1975) Bioinorg Chem 4:143–151; (b) Johnson A, O’Connell LA, Clarke MJ (1993) Inorg Chim Acta 210:151–157; (c) Zhenga T, Suna H, Lua F, Harmsc K, Li X (2013) Inorg Chem Commun 30:139–142 5. Cebollada A, Velle A, Sanz Miguel PJ (2014) unpublished results.

Reference 1. Thomas KE, Alemayehu A, Conradi, J, Beavers CM, Ghosh A (2012) Acc Chem Res 45:1203–1214

OP 27 Investigation of metal complexes-RNA interaction Marianthi Zampakou1, Elena Alberti1, Michael P. Coogan2, Daniela Donghi1 1

Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland. [email protected] 2 Department of Chemistry, Faraday Building, Lancaster University, Bailrigg, Lancaster, LA1 4YB, UK The use of metal complexes as therapeutic and diagnostic agents is well acknowledged [1]. Depending on their chemical nature, these complexes can interact with their biological target via covalent and non-covalent binding [1]. The anticancer drug cisplatin and its derivatives belong to the first class of compounds, and are believed to mainly target DNA by preferentially binding to N7 atoms of guanine

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bases [2]. Conversely, various complexes studied as potential bioimaging agents belong to the second class, and show luminescence upon DNA intercalation [3]. In addition to DNA, metal complexes can also target other biomolecules, including RNA [4]. The latter is involved in several crucial biological processes and its structural diversity makes it an attractive target for the development of structure-selective RNA targeting molecules [5]. For example, platinum drugs can inhibit RNA dependent processes [4] and metal complexes with potential in bio-imaging were shown to accumulate in RNA-rich regions within the cell [6]. Nevertheless, information on metal containing molecules binding to RNA is still scarce. We are currently investigating the interaction of different classes of metal complexes with RNA to rationalize the basis of structureselective recognition. We use as model systems RNA constructs that contain structural features widespread in RNA, e.g. GU wobbles, internal and terminal loops. On the one hand, we study RNA interaction with platinum drugs with a special focus on cisplatin and oxaliplatin. On the other hand, we investigate the RNA binding ability of mononuclear rhenium(I) metallo-intercalators [6]. The interaction is studied by several techniques, including gel mobility shift assays, UV–vis, luminescence and CD spectroscopy and mass spectrometry. Special attention is given to NMR spectroscopy, which is used to both localize the interaction site and to evaluate the structural changes induced by metal complex binding. Financial support by the Swiss National Science Foundation (Ambizione fellowship PZ00P2_136726 to DD), by the University of Zurich (including the Forschungskredit FK-13-107 to DD) and within the COST Action CM1105 is gratefully acknowledged.

treatments to facilitate thiocyanate formation since it does not affect oxygen carrying capacity in smoke inhalation victims [2–3]. We describe our approach to catalytically transfer sulfur from thiosulfate to cyanide to facilitate thiocyanate formation, using well-tolerated compounds in small amounts to minimize toxicity without sacrificing oxygen transport. Data for spontaneous and catalytic sulfur transfer reactions will be presented along with results from toxicity and efficacy studies. In one instance we show near complete elimination of cyanide from solution in 20 min, in a reaction of cyanide with thiosulfate solutions containing 10 mol% of a molybdenum sulfur complex. The molybdenum sulfur complexes were shown non-toxic in hepatocytes, and safe dose in mice was measured as 0.5 g/kg. Financial support by the University of Iceland Research Fund, and NIH NINDS Grant No. 5R21NS067265 is gratefully acknowledged.

References 1. Ma D-L, He H-Z, Leung K-H, Chan DS-H, Leung C-H (2013) Angew Chem Int Ed 52:7666–7682 2. Alderden RA, Hall MD, Hambley TW (2006) J Chem Educ 83:728–734 3. Zeglis BM, Pierre VC, Barton JK (2007) Chem Commun 4565–4579 4. Chapman EG, Hostetter AA, Osborn MF, Miller AL, DeRose VJ (2011) Met Ions Life Sci 9:347–377 5. Guan L, Disney MD (2012) ACS Chem Biol 7:73–86 6. Thorp-Greenwood FL, Coogan MP, Mishra L, Kumari N, Rai G, Saripella S (2012) New J Chem 36:64–72

References 1. Leininger K, Westley J (1968) J Biol Chem 243:1892–1899 2. Ivankovich AD, Braverman B, Kanuru RP Heyman HJ Paulissian R (1980) Anesthesiology 52:210–216 3. Baud FJ (2007) Hum Exp Toxicol 26:191–201

OP 29 Metal complexes as molecularly-targeted agents against protein–protein interactions Hai-Jing Zhong1, Li-Juan Liu1, Daniel Shiu-Hin Chan2, Dik-Lung Ma2, Chung-Hang Leung1 1

OP 28 Cyanide detoxification by molybdenum sulfur complexes Sigridur G. Suman1,2, Johanna M. Gretarsdottir1, Thorvaldur Snæbjo¨rnsson1, Gerdur R. Runarsdottir1, Paul E. Penwell2, Shirley Brill3, Carol Green3 1

Science Institute, University of Iceland, Dunhagi 3, 107 Reykjavik, Iceland 2 Physical Sciences Department, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025, USA 3 Biosciences Department, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025, USA. [email protected] Thiocyanate is a product of a biocatalytic reaction of cyanide and sulfur by the rhodanase enzyme in the liver. Mechanistic studies in vitro of the rhodanase catalyzed reaction of cyanide and thiosulfate showed the reaction takes place by a conformational change of the enzyme and metal assisted thiosulfate binding. The rate limiting step of this reaction is the rupture of the sulfur–sulfur bond in thiosulfate [1]. Natural sulfur substrates are quickly depleted at toxic levels of cyanide. Thiosulfate is commonly administered with cyanide

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Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China 2 State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao, China Protein–protein interactions (PPIs) are ubiquitous in essential biological processes such as cell proliferation and differentiation, hostpathogen interactions, and signal transduction pathways [1]. Pioneering advances in the field of interactomics have uncovered new networks of protein interactions within cells, with estimates for the size of the interactome ranging up to 650,000 PPIs [2]. Hence, PPIs have emerged as attractive targets in medicinal chemistry and drug discovery [3]. Meanwhile, transition metals possess variable oxidation states and molecular geometries that enable the design of intricate coordination sphere architectures. The ability to arrange organic ligands in a precise three-dimensional arrangement around the metal centre can be harnessed to generate unique scaffolds for recognizing the binding sites of proteins. Due to the adverse side effects associated with ‘‘shotgun’’ cytotoxic metal complexes such as cisplatin and its analogues, there has been a recent upsurge in interest in the development of kinetically-inert metal complexes as molecularly-targeted agents against enzymes or PPIs [4–7]. We present recent examples of biologically active, kinetically-inert metal

J Biol Inorg Chem (2014) 19 (Suppl 2):S749–S764 complexes developed by our group, and highlight possible future directions for this exciting field. Financial support by the University of Macau is gratefully acknowledged. References 1. Lievens S, Eyckerman S, Lemmens I, Tavernier J (2010) Expert Rev Proteomics 7:679–690 2. Stumpf M, Thorne T, de Silva E, Stewart R, An H, Lappe M, Wiuf C (2008) Proc Natl Acad Sci USA 105:6959–6964 3. Wells J, McClendon C (2007) Nature 450:1001–1009 4. Meggers E (2011) Angew Chem Int Ed 50:2442–2448 5. Leung CH, Zhong HJ, Yang H, Cheng Z, Chan DS, Ma VP, Abagyan R, Wong CY, Ma DL (2012) Angew Chem Int Ed 51:9010–9014 6. Zhong HJ, Leung KH, Liu LJ, Lu L, Chan DSH, Leung CH, Ma DL (2014) ChemPlusChem (in press) 7. Leung CH, He HZ, Liu LJ, Wang M, Chan DSH, Ma DL (2013) Coord Chem Rev 257:3139–3151

OP 31 Lanthanide complexes as tools for structural biology Bim Graham1, James D. Swarbrick1, Michael D. Lee1, Phuc Ung1, Sandeep Chhabra1, Choy Theng Loh2, Thomas Huber2, Gottfried Otting2 1

Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia. [email protected] 2 Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia The tagging of proteins with paramagnetic lanthanide ions produces large effects that are observable in NMR spectra, including pseudocontact shifts, paramagnetic relaxation enhancements and residual dipolar couplings [1, 2]. These effects provide valuable structural restraints to expedite protein structure determination and facilitate structure analysis of protein–protein and protein–ligand interactions. In addition, the attachment of pairs of gadolinium complexes to proteins enables highly accurate distance measurements to be made in protein assemblies via EPR spectroscopy [3]. Our group has developed a range of new tagging reagents and strategies for attaching lanthanide ions to proteins in a site-specific manner, which have greatly facilitated such structural studies. This presentation will describe the synthesis, testing and utilization of some of our most successful designs and approaches. Financial support by the Australian Research Council is gratefully acknowledged, including a Future Fellowship to B.G.

S761 References 1. Otting G (2010) Annu Rev Biophys 39:387–405 2. Keizers PHJ, Ubbink M (2011) Prog Nucl Magn Reson Spectrosc 58:88–96. 3. Yagi H, Banerjee D, Graham B, Huber T, Goldfarb D, Ottin G (2011) J Am Chem Soc 133:10418–10421

OP 32 Expanding nature’s toolbox with artificial metalloenzymes Jo¨rg Eppinger1, Johannes Fischer1, Anna Zernickel1, Arwa Makki1 1

Division of Physical Sciences and Engineering and KAUST Catalysis Centre (KCC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia. [email protected] Artificial metalloenzymes are expected to combine enzymatic selectivity with the broad range of catalytic motifs provided by homogeneous catalysts. Using specifically designed metal-conjugated affinity labels to introduce metal centres into the binding pocket of cysteine proteases, we were able to overcome the lack of structural definition, which tends to hamper catalytic selectivity. Experimental results proof, that the protein ligand induces enantioselectivities. The novel modular platform and the in situ protocol allow fast generation of diverse libraries of organometallic enzyme hybrid catalysts (see figure) [1]. Site-selective orthogonal incorporation of metal binding unnatural amino acids (UAA) into a host protein represents another novel tool to create catalytically active metalloenzymes in vivo. The incorporated UAA provides stable ligation of late transition metals or serves as an anchoring point to selectively conjugate metal chelating motives to the host protein. This presentation details our studies on the development of an optimized fluorescent host protein (mTFP*) with minimized metal binding affinity and its conversion into an artificial metalloenzyme through UAA incorporation and specific UAA-metal conjugation. X-Ray crystallographic studies, post-translational modification (e.g. CuAAC) and catalytic tests for asymmetric cyclo-addition and Pd-catalyzed cross-coupling reactions are presented. Financial support by the King Abdullah University of Science and Technology, KAUST (faculty baseline fund and KAUST-GCR project FIC/2010/07) is gratefully acknowledged.

Reference 1. Reiner T, Jantke D, Marziale AM, Raba A, Eppinger J (2013) ChemistryOpen 2:50–54

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OP 33 Synthesis of fac-{99(m)TcO3}+ complexes: activation of [99(m)TcO4]2 by phosphonium cations Henrik Braband, Michael Benz, Roger Alberto Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland. [email protected] 99m Tc is a very practical nuclide for nuclear medical applications due to its availability from generators, its short physical half-life time (6 h), and the emission of low energy c-rays (140.5 keV). We are aiming at a general understanding of the reactivity of technetium at its highest oxidation state +VII. Our research foremost focuses on compounds containing the fac-{99(m)TcO3}+-core, due to its interesting chemical reactivities ((3+2)-cycloaddition with alkenes) [1]. This reactivity enables an innovative approach for the synthesis of novel radioconjugates [2]. Recent developments, based on the interaction of phosphonium salts with the robust [99(m)TcO4]- anion in neutral water, led to a simple procedure for the synthesis of [99mTcO3(tacnR)]+ type complexes (tacnR = 1,4,7-triazacyclononane or derivatives) [3]. Due to this new approach fac-{99mTcO3}? complexes are now available in high yields and purity for stereoselective labeling of biomolecules. The potential of the new bioconjugation strategy has been demonstrated by labeling of a series of different vectors (pharmacophores, non-natural amino acids, and carbohydrates) [4]. Furthermore, the labeling via (3?2)-cycloaddition has been established as a novel procedure for the labeling of silica based particles, which will help to gain more detailed in vivo data of silica (nano)particles by non-invasive radioimaging, in the future [5].

H

H N N

N

+

Tc O

O

H

H

O

R

H N N

N

H

Tc O

O O

R

R = pharmacophores, amino acids, carbohydrates (nano)particles

References 1. Pearlstein RM, Davison A (1988) Polyhedron 7:1981–1989 2. Braband H, Tooyama Y, Fox T, Alberto R (2009) Chem Eur J 15:633–638 3. Braband H, Benz M, Tooyama Y, Alberto R (2014) Chem Commun 50:4126–4129 4. Braband H, Tooyama Y, Fox T, Simms R, Forbes J, Valliant, JF, Alberto R (2011) Chem Eur J 17:12967–12974 5. Wuillemin, MA, Stuber WT, Fox T, Reber MJ, Bru¨hwiler D, Alberto R, Braband H (2014) Dalton Trans 43:4260–4263

OP 34 Alkalimetal controlled DNA nanoswitch Ce´lia Fonseca Guerra1, Jordi Poater1, Marcel Swart1,2, F. Matthias Bickelhaupt1 1

Department of Theoretical Chemistry, VU University Amsterdam, 1081 HV Amsterdam, The Netherlands 2 Institut de Quı´mica Computacional, Universitat de Girona, 17071 Girona, Spain. [email protected] The self-assembly capacity of DNA has been an inspiration in the field of supramolecular chemistry. We show with dispersion-corrected density functional theory that DNA itself can be used as a nanoswitch, able to alternate between three states (weak, moderate and strongly bound). The suitable DNA base pair to act as the switch is the Watson–Crick GC base pair. Substitution of H8 at the six-membered

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ring of the purine by OH enables via protonation or deprotonation to obtain the switching capacity. This capacity is also observed when the switching aggregate is addressed through coordination of alkali metal cations to OH instead of protons. The switching behavior is still preserved when the subsitituent is linked to the DNA base pair via ˚ ) turning the substituent into a remote an acetylene linker (26 A control. The switching could therefore pass through a membrane allowing for different experimental conditions of the controller and the switch. The last step in the computational design of a DNA switch was to introduce the switch into a DNA helix and ‘‘submerge’’ it into different solvents. This computational investigation of the artificial DNA nanoswitch showed that the switch conserves its switching capacities under experimental conditions which in general involve solvation. Financial support by the NRSC-C, NWO, MICINN and HPCEuropa2 is gratefully acknowledged.

References 1. Fonseca Guerra C, van der Wijst T, Bickelhaupt FM (2006) Chem Eur J 12:3032–3042 2. Fonseca Guerra C, Szekeres Z, Bickelhaupt FM (2011) Chem Eur J 17:8816–8818 3. Poater J, Fonseca Guerra C, Swart M, Bickelhaupt FM, submitted

OP 35 The diverse functions of calcium in natural water oxidation Dimitrios A. Pantazis, Marius Retegan, Vera Krewald, Frank Neese, Nicholas Cox Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34–36, 45470 Mu¨lheim an der Ruhr, Germany Natural water oxidation, carried out by an inorganic Mn4CaO5 cluster embedded in the enzyme photosystem II of photosynthetic organisms, underpins all oxygenic life on earth [1]. Among the many poorly understood aspects of this process, which serves as the ultimate blueprint for synthetic efforts towards development of synthetic water splitting catalysts, is the role of calcium: why does the catalyst depend critically on calcium for its function, and why is natural water oxidation inhibited by very similar cations, even though they may be structurally incorporated in the catalytic cluster? We address these questions by combining recent results from spectroscopy (EPR/ENDOR), information from kinetics measurements, and extensive theoretical modelling of photosystem II and its oxygen evolving complex [1–4]. Our results suggest that the calcium ion satisfies not one but several diverse requirements,

J Biol Inorg Chem (2014) 19 (Suppl 2):S749–S764 which are electronic as much as structural in nature. Most importantly, calcium simultaneously modulates the properties of not only the Mn4CaO5 cluster itself, but also of the redox-active tyrosine residue that mediates electron transfer from the water oxidation site to the photodriven charge separation site of the enzyme.

S763 4. Liu H, Li Y, Wang ST et al J Am Chem Soc 135:7603–7609 5. Zhang PC, Chen L, Zhou J, Wang ST et al (2013) Adv Mater 25:3566–3570 6. Wang ST, Liu K, Liu J et al (2011) Angew Chem Int Ed 50:3084–3088

OP 37 A comprehensive platform to investigate protein-metal ion interactions by affinity capillary electrophoresis (ACE) Hassan A. AlHazmi1, Markus Nachbar1, Mona Mozafari Toshizi1, Sabine Redweik1, Sami El Deeb2, Deia El Hady3,4, Hassan M. AlBishri3, Hermann Wa¨tzig1 References 1. Cox N, Pantazis DA, Neese F, Lubitz W (2013) Acc Chem Res 46:1588–1596 2. Pantazis DA, Ames W, Cox N, Lubitz W, Neese F (2012) Angew Chem Int Ed 51:9935–9940 3. Retegan M, Neese F, Pantazis DA (2013) 9:3832–3842 4. Retegan M, Cox N, Lubitz W, Neese F, Pantazis DA (2014) Phys Chem Chem Phys. doi:10.1039/C1034CP00696H

OP 36 Engineering biointerface with controlled cell adhesion towards cancer diagnostics Gao Yang1, Pengchao Zhang1, Xueli Liu1, Hongliang Liu1, Shutao Wang1 1

Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences, Beijing 100190, China. [email protected] Circulating tumor cells (CTCs) have become an emerging ‘‘biomarker’’ for monitoring cancer metastasis and prognosis. Although there are existing technologies available for isolating/counting CTCs, the most common of which using immunomagnetic beads, they are limited by their low capture efficiencies and low specificities. By introducing a three-dimensional (3D) nanostructured substrate—specifically, a silicon-nanowire array coated with anti-EpCAM—we can capture CTCs with much higher efficiency and specificity. The conventional methods of isolating CTCs depend on biomolecular recognitions, such as antigen–antibody interaction. Unlikely, we here proposed that nanoscaled local topographic interactions besides biomolecular recognitions inspired by natural immuno-recognizing system. This cooperative effect of physical and chemical issues between CTCs and substrate leads to increased binding of CTCs, which significantly enhance capture efficiency. Recently, we have also developed a 3D cell capture/release system triggered by aptamer enzyme, electrical potential and Temperature, which is effective and of ‘‘free damage’’ to capture and release cancer cells. The bio-inspired interfaces of cell capture and release open up a light to rare-cell based diagnostics, such as CTCs, fetal cells, stem cell and so on. Financial support by the Chinese Academy of Sciences is gratefully acknowledged. References 1. Liu X, Wang ST(2014) Chem Soc Rev 43:2385–2401 2. Liu H, Liu X, Wang ST et al (2013) Adv Mater 25:922–928 3. Jin J, Wang ST, Liu DS et al (2013) Adv Mater 25:4714–4717

1

Institute of Medicinal and Pharmaceutical Chemistry, University of Braunschweig, Germany 2 Department of Pharmaceutical Chemistry, Al-Azhar UniversityGaza, Gaza, Palestine 3 Chemistry Department, Faculty of Science-North Jeddah, King Abdulaziz University, Jeddah, Saudi Arabia 4 Chemistry Department, Faculty of Science, Assiut University, 71516-Assiut, Egypt Affinity Capillary Electrophoresis (ACE) provides an important enhancement to characterize molecular interactions. In exciting recent studies, the influence of various metal ions, including Li?, Na?, Mg2?, Ca2?, Ba2?, Al3?, Ga3?, La3?, Pd2?, Ir3?, Ru3?, Rh3?, Pt2?, Pt4?, Os3?, Au3?, Au?, Ag?, Cu2?, Fe2?, Fe3?, Co2?, Ni2?, Cr3?, V3?, Mn2?, MoO42- and SeO32- was investigated by ACE, giving deep insight into the functional interactions between these species and biomolecules. The predominant role of ACE is in the early screening stage when binding and non-binding compounds are sorted out. The requirements for sample amount and purity are low, but high precision of binding information in reasonable short analysis times can be expected [1]. ACE can now be performed in *5 min including rinsing procedures. An excellent precision, corresponding to RSD % of 0.2–1.0 % was achieved. Long term stability and appropriate method transfers have also been established. The capillary manufacture batch, the type of temperature controlling tool, the purity of running buffer constituents and the quality of the ligands involved, including their stability, have been identified as main parameters for robustness. Further ACE key method development parameters include protein concentration, length of injected plug, applied voltage, and the choice of the regression method [2]. Now we not only provide a generic concept and experimental conditions for all relevant metal ions to be investigated, which could be easily enhanced to each and every further species, but we also provide reference values for characteristic interactions to a set of reference proteins. These concepts have already been successfully applied for a number of applications, namely Extracellular-signal Regulated Kinase (ERK), dehydrins (metal-ion storing plant proteins), potentially Ca2? binding peptides and transferrin. References 1. AlHazmi H, El Deeb S, Nachbar M, Redweik S, AlBishri HM, Abd El-Hady D, Wa¨tzig H Submitted to electrophoresis, manuscript no. elps.201400064 2. El Deeb S, Wa¨tzig H, El-Hady D (2013) Trends Anal Chem 48:112–131

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OP 38 Specific recognition of DNA depurination by a luminescent terbium(III) complex Xiaohui Wang1,3, Xiaoyong Wang2, Zijian Guo1

J Biol Inorg Chem (2014) 19 (Suppl 2):S749–S764 Financial support by National Natural Science Foundation of China is gratefully acknowledged.

1

State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, People’s Republic of China. [email protected] 2 State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing 210093, People’s Republic of China. [email protected] 3 College of Sciences, Nanjing Tech University, Nanjing 211816, People’s Republic of China. [email protected] Recognition of DNA depurination is of great importance for early cancer detection [1]. Luminescent lanthanide complexes possess some fascinating optical properties that have shown potential applications in biomedical researches [2]. In this study, a novel terbium(III) complex (TbL) has been demonstrated to be capable of recognizing purine nucleobases in DNA as a selective time-resolved luminescence probe. The luminescence of TbL is enhanced remarkably upon reaction with oligonucleotides or natural DNA containing purine bases in aqueous solution, while it is quenched dramatically as depurination occurs to DNA. Mechanistic studies using the circular dichroism and fluorescence spectroscopies revealed that the luminescence enhancement results from the preferential intercalations between nitroimidazole moieties of TbL and purine bases of DNA, which regulate the electron withdrawing effect of nitro groups via hydrogen bonds and thereby affect the energy transfer from the ligand to the metal center of the probe. This mechanism is also supported by the molecular dynamics simulation results for the reaction. The distinct luminescence responses of TbL in the presence and absence of purine bases in DNA make it a sensitive probe for DNA depurination in physiological conditions.

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References 1. Dahlmann HA, Vaidyanathan VG, Sturla SJ (2009) Biochemistry 48:9347–9359 2. Bu¨nzli JCG, Eliseeva SV (2013) Chem Sci 4:1939–1949