abstracts poster presentations (z10)

Journal of lnorganic Biochemistry 86 (2001) 461

Heterod inuc lear ZnnFe m complexes of an asymmetr ic l igand for model l ing purple acid phosphatases

Vladimir Trukhan". H~kan Carlsson ~, Matti Haukka b, and Ebbe Nordlander ~. "Inorganic Chemistry 1, Chemical Center, Lund University, Box 124, Se-221 O0 Lund, Sweden (e-mail: Vladimir. Trukhan@inorg. lu.se) SDepartment o[ Chemistry, University of Joensuu, Box 101, FIN 80101, Joensuu, Finland

There are often pronounced asymmetries in catalytically active metallobiosites and these are very likely essential for the catalytic properties. In order to mimic such an asymmetric environment, a new ligand, 2-(N.-isopropyl-N-((1-methylimidazol)methyl)aminomethyl)-6-(N- (carboxylmethyl)-N-((1-methylimidazol)-methyl)aminomethyl)-4-methylphenol, containing different pendant arms was synthesized. Synthesis of iron complexes of this ligand resulted in formation of mono- and dinuclear species which were identified by mass-spectrometry and X-ray crystallography.

The mononuclear complex crystallizes as a dimer of two mononuclear species connected via hydrogen bonds (a). In solution, there appears to be an equilibrium between the mononuclear and dinuclear species which may be shifted in favor of the dinuclear species by addition of an excess of carboxylate and an iron(IlI) salt. The mononuclear complex reacts with equimolar amount of zinc perchlorate to give a heterodinuclear ZnnFe HI complex. At the same time, the use of zinc acetate in the next step provided formation of a ZnHFe m p-biscarboxylate complex (c).

The catalytic activity of the heterodinuclear complexes towards phosphate ester cleavage is under investigation.

H ~ \ / ' H \ / . . ~ ~N~

/'~z~ '--e7 ~ .rN,_.k ? Y ~,- ~',

Nitri le hydratase has a c o m m o n post- translat ional modif icat ion

Masanari Tsujimura a, Naoshi Dohmae a, Hiroshi Nakayama a, Masafumi Odaka a, Koji Takio ~, Isao Endo b and Michihiko Kobayashi c. a RiKEN (The institute of Physieal and Chemical Research), Hirosawa 2-1, Wako, Saitama 351-

0198, Japan (e-mail:[email protected]) b Department of Applied Biochemistry, Utsunomiya University, Mine-cho 350, Utsunomiya,

Tochigi 321-8505, Japan Clnstitute of Applied Biochemistry, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, Ibaraki

305-8572, Japan

Nitrile hydratase (NHase, EC 4.2.1.84) is a bacterial metalloenzyrne catalyzing the hydration of various nitrile compounds to their corresponding amides. NHase consists of a and [3 subunits and contains a non-heine Fe 3+ or non-corrin Co 3+ at the catalytic center. Crystal structure analysis ~ of Fe-type NHase from Rhodococcus sp. N-771 revealed the iron center having two post-translationally modified ligands, cysteine sulfenic acid (Cys-SOH) and cysteine sulfinic acid (Cys- SO2H). The structure of the active center including the post-translational modifications is likely to be conserved among other NHases because the amino acid sequences stabilizing the active center are highly conserved in all known NHases. To confirm this hypothesis, we examined two kinds of NHases from Pseudomonas chlororaphis B23 (Fe-type) and Rhodococcus rhodochrous J-1 H (Co-type). The NHases were cleaved with proteases. The metal center peptide was purified by reversed-phase HPLC and analyzed by MALDI-TOF MS. The observed mass values were 32 Da larger than the calculated ones, showing that the Cys-SO2H stabilization were conserved in both two NHases by mass spectrometric measurements of the metal center peptides. On the other hand, we could not detect a Cys-SOH in both enzymes. This is probably due to the lability of Cys-SOH during preparing MS samples. We have been trying to develop a new method to identify the Cys-SOH directly.

1. Nagashima S. et al., Nat. Struc. Biol. 5,347-351 (1998)

462 Journal of Inorganic Biochemistry 86 (2001)

E x t r e m e l y s low intramolecular electron transfer in cy tochrome c modif ied with a d ie thylenetr iaminepenta-

acetatocobaltate(III) complex

Kei i ch i T s u k a h a r a a, Y u k a K a i d a a, N a o I i da a, H i ro sh i T a k a s h i m a a, M a y a M i z o b e b, R y u i c h i A r a k a w a b

~Department of Chemistry, Faculty of Science, Nara Women's University, Nara 630-8506, JAPAN (e-mail: [email protected])

ODepartment of Applied Chemistry, Faculty of Engineering, Kansai University, Suita 564-8680, Osaka, JAPAN

Horse heart cytochrome c (cytc) modified with a diethylenetriaminepentaacetatocobaltate(III) complex was prepared and characterized. The largest yield of the singly modified cytcln{CoH1(dtpa)} contains Lys 13 whose amino group is linked by a [Com(dtpa)] complex with an amide bond. The one-electron reduced protein, cytcH{Com(dtpa)}, was prepared by a reduction with a methylviologen radical cation which was produced in situ by a photoreduction using a tris(2,2'-bipyridine)ruthenium(II) ion in the presence of EDTA at 25 °C, pH 7.5 (10 mM phosphate buffer), and an ionic strength of 0.50 M (NaC1). The reaction of cytcH{Com(dtpa)} to form cytc HI{ColE(dtpa)} was very slow and followed by a conventional spectrophotometry. The reaction was of first order in the protein and the first-order rate constant ((3.1 + 0.5) × 1 0 -4 S -|) was independent of the My2÷ concentrations of the protein, indicating p- I~u~)~+)" • t~ [.uco~l~2÷ that the predominant reaction is the ~ " [nufalr/)a 13' /""~EOrA intramolecular process. The extremely uv~. slow intramolecular electron transfer rate J /

on arc s t oryo, distance dependence of the rate of reaction.

¢ .

Conformat iona l studies of angiotensin II-metal complexes by N M R spectroscopy

Andreas Tzakos a, Anastasios Troganis a, Roberta Pierattelli b, Ioannis Gerothanassis a, Alexandre Bonvin c, Nico van Nuland c, and Paul Kordopatis d

Department of Organic Chemistry and Biochemistry, University of loannina, GR-451 10, Greece b Dertment of Magnetic Resonance Center, University of Florence, 50019, Sesto Fiorentino, Italy CBijvoet Center, NMR spectroscopy, Utrecht University, 3584 CH Utrecht dDepartment of Pharmacy, University of Patras,265 04, Patras, Greece (e-mail: chO1811@cc, uoi.gr)

Angiotensin II is a linear octapeptide hormone (DRVYIHPF) with a wide range of biological activities ~. Biological studies have indicated that the activities of AII are selectively enhanced in vivo and in vitro by certain metal ions (Ca 2+, Na + Li + M f + and Mn2+) 2. Further, it has been suggested that cations induce conformational changes in AII to result in a more physiologically active conformer 3. This work addresses the , , ~ ~ - question of the structural features of angiotensin II when bound to metal ions (Ca 2+, Zn 2÷, lanthanide ions). The nature of the metal-peptide complexes and the topology of this peptide in this complexes is examined by the use of tSC, two-dimensional 1H-tH nuclear magnetic resonance and molecular dynamics.

1. Lucius R., Gallinat S., Busche S., Rosentiel P., Unger T., Cell. Mol, Life Sci., 1008 (1999) 2 Degani et al,, Biochemistry, 19, 3430 (1980) 3. Scchaechtelin G., Walter R., Salomon H., Jelinek J., Karen P., and Cort J. H., Mol. Pharmacol., 10, 57 (1974)

The Greek General Secretary of Research and Technology (PENED 99) is acknowledged for financial support

Journal of Inorganic Biochemistry 86 (2001) 463

Ni(III) dithiolene complexes - comparisons with Ni centres in enzymes

Josephine M. Tunney, Alexander J. Blake, E. Stephen Davies, C. David Garner, Jonathan McMaster, Claire Wilson School of Chemistry, University of Nottingham, University Park, Nottingham, UK, NG7 2RD

A distinctive feature of nickel-containing enzymes is the existence of Ni(III).l It appears that, for the Ni(III)/Ni(II) couple to be utilised, sulfur-donor ligands are required. 2 We have synthesised and characterised a series of bis(dithiolene)nickel(III) complexes to aid our understanding of the electronic structure and redox properties of nickel centres in enzymes. The spectroscopic and electrochemical properties of these complexes demonstrate that both the Ni(III)/Ni(II) and Ni(IV)/Ni(III) couples are available and reversible. The crystal structures of three [PPh4][Ni(dithiolene)2] complexes show the Ni(III)S4 centres to be square planar. The electronic structures of these series of Ni(II), Ni(III) and Ni(IV) complexes have been investigated by a variety of structural, spectroscopic, and theoretical techniques. Comparisons with Ni centres in enzymes will be presented.

1. Kolodziej A. F., Prog. Inorg. Chem., 41,493 - 597 (1994) 2. Maroney M. J., CULT. Opin. Chem. Biol., 3, 188 - 199 (1999)

Interactions of vanadium and quinolone family member-ciprofloxacin

Iztok Turel a, Ales Klavzar a, Boris Pihlar a, Dieter Rehder b, Peter Buglyo c, Kristina Sepcic d ~Faculty of Chemistry and Chem. Technology, University of Ljubljana, Askerceva 5, 1000

~jubljana, Slovenia (e-mail: iztok, [email protected] 0 '~Chemistry Department, University of Hamburg, Martin-Luther-King Platz 6, D-20146 Hamburg,

Germany CDepartment of Inorganic and Analytical Chemistry, University of Debrecen, H-4010 Debrecen,

Hungary dBiotechnical Faculty, Department of Biology, University of Ljubljana, Vecna pot 111, 1000

Ljubljana, Slovenia

Quinolones are a group of synthetic antibacterial agents used in clinical practice. It was found that quinolones react with several metal ions. The complex of vanadium(IV) and ciprofloxacin (Scheme) was isolated and characterized by several physico-chemical methods in solid state (elemental analysis, IR, EPR, X-ray structure analysis) and in solutions (UV-VIS, potentiometry, cyclic voltammetry). The biological activity of the sample against various microorganisms as well as insulin- mimetic behaviour was tested.t

1. Rehder D., Costa Pessoa J., Geraldes C.F.G.C., Kabanos T., Kiss T., Meier B., Micera G., Pettersson L., Rangel M., Salifoglou A., Turel I., Wang D., submitted.

o o

0, T" P o .

H/N"~ '2' /iX

The Ministry of Science, Education and Sport of Slovenia is acknowledged for financial support (P0-511-103-00).


Dynamics of electron transfer protein complexes probed by NMR

Marcellus Ubbink a, Peter B. Crowley a, Jonathan A. R. Worrall a

~ Leiden Inst i tute o f Chemistry, Leiden University, Gorlaeus Laboratories , PO BOX 9502, NL-2300 RA, Leiden, The Netherlands, e-mail: m.ubbink@chem. le idenuniv .n l

NMR studies were performed on a range of electron transfer protein complexes, involving various cytochromes c, cytochromesf cytochrome bs, plastocyanins, cytochrome c peroxidase and myoglobin. Line broadening and chemical shift titrations were used to demonstrate complex formation. Chemical shift perturbation assays showed that the size of the chemical shift changes caused by complex formation varies more than an order of magnitude for various 1:1 complexes and also depends on the redox states of the proteins. Also the nature of the affected residues varies between different complexes. Furthermore, in some complexes interprotein paramagnetic effects are observed, while these are absent in others. In combination, these results indicate that some complexes exist predominantly in a single orientation, stabilised by both electrostatic and hydrophobic forces, and others are a dynamic ensemble of relative orientations, of a purely electrostatic nature. The results can be related to kinetic data and explain the large differences in rates of electron transfer, such as observed for electron transfer from cytochromefvs, cytochrome c to plastocyanin.

Computing macroscopic and microscopic pKa vaules of the Rieske iron-sulfur cluster using a combined electrostatic-density functional method

G. Matthias Ullmann a, Louis Noodleman b, and David A. Case b a

IWR - Biocomputing, University Heidelberg, Im Neuenheimer Feld 368, 69120 Heidelberg, Germany b Department of Molecular Biology, The Scripps Research Institute, 10550 N. Torrey Pines Rd., La Jolla, CA 92037, USA

The redox potential of the Rieske iron-sulfur center of bc-type cytochromes depends on pH. It was proposed that the histidines coordinating one of the iron are responsible for this pH dependence. An experimental proof for this suggestion is, however, still lacking. In this work, we present a density functional/continuums electrostatic calculation of the pKa values in the Rieske center. The calculated apparent pKa values are 6.9 and 8.8 in the oxidized state, which are in agreement with the measured pH dependence of the redox potential. Neither of the two pKa values can, however, be assigned to only one of the histidines. We find that both histidines titrate over a wide pH range in the oxidized state. The meaning of microscopic and macroscopic pKa values is discussed. Reduction of the Rieske center shifts the pK~ values to 11.3 and 13.4, thus above 10.0 as found experimentally.

1. Alexey Onufriev, David A. Case, and G. Matthias Ullmann (2001): A Novel View of pH Titration in Biomolecules. Biochemistry 40, 3413-3419.

2. G. Matthias Ullmann (2000): The Coupling of Protonation and Reduction in Proteins with Multiple Redox Centers. Theory, Computational Method, and Application to Cytochrome c3. J. Phys. Chem. B 104, 6293-6301.

3. G. Matthias Ullmann and Ernst-Walter Knapp (1999): Electrostatic Computations of Protonation and Redox Equilibria in Proteins. Eur. Biophys. J. 28, 533-551.


C o p p e r ( I ) - c o m p l e x e s wi th N-donor - l i gands as tyros inase mimics

Diana Utz, Siegfried Schindler

Department of Inorganic Chemistry, University of Erlangen-Niirnberg, Egerlandstrasse 1, 91058 Erlangen, Germany (e-mail: [email protected])

The dicopper containing enzyme tyrosinase catalyses the ortho-hydroxylation of phenols to ortho-diphenols. In order to mimic tyrosinase activity, we prepared and investigated structural and functional model compounds for this monooxygenase. It has been demonstrated that the macrocyclic dinuclear copper(I)-complex [Cuzmac] ~+ exhibits intramolecular hydroxylation of the ligand. 1"2 The oxidation reaction was studied kmetically. 3 In order to find a relationship between structure and reactivity, [CuEmac] 2+ was characterized by single crystal x-ray diffraction. Each copper(I)-center is coordinated in a pseudotetrahedral manner by three nitrogen atoms of the ligand and one acetonltrile molecule. In order to demonstrate that dinuclearity is essential for hydroxylation reactions, we also synthesized the open-chain mononuclear analogue of the macrocyclic compound. In methanolic solution this complex reacts with dioxygen in an ordinary redox reaction to give a bis-g-dimethoxide dimer. Both the copper(1)- complex and the resulting copper(II)-species have been structurally characterized.

c c 7 c ~ c ~ o

ca

cls ,a

4 ca

l. R. Menif, A. E. Martell, P. J. Squattrito, A. Clearfield, Inorg. Chem., 29, 4723-4729 (1990) 2. R. Menif, A. E. Martell, J. Chem. Soc., Chem. Comm., 1521-1523 (1989) 3. M. Becker, S. Schindler, R. van Eldik, Inorg. Chem., 33, 5370-5372 (1994)

Direct ev idence for m o n o a n i o n i c b inding of substrate to 2 , 3 - d i h y d r o x y b i p h e n y l 1 ,2 -d ioxygenase p r o b e d by U V resonance raman and UV/Vi s absorpt ion spectroscopies

• * a b Fr6d6fic H. Valllancourt ' ' ~ Christopher J. Barbosa*' c, d Thomas G. Spiro e, Michael W. Blades c, Robin F.B. Turner d' f, and Lindsay D. Eltis a' b " Shared f irs t authorship (fvaillan@hotmail. com, [email protected]) Departments o f MicrobiolofiS, Biochemistry b, Chemistry c, Electrical Engineering y, and Biotechnology Laboratory , University o f British Columbia, B.C., V6T IZ3, Canada

e Department of Chemistry, Princeton University, Princeton, N J, 08544, USA

2,3-Dihydroxybiphenyl 1,2-dioxygenase (DHBD), the Fe(II)-containing extradiol dioxygenase of the microbial biphenyl / PCB degradation pathway, catalyses the cleavage of 2,3-dihydroxybiphenyl (DHB) with the incorporation of dioxygen into the product. Based on bond lengths, it had been proposed that the catecholic substrate of extradiol dioxygenases binds to the active site Fe(II) as a monoanion. In this study, ultraviolet resonance Raman spectroscopy (UVRRS) and electronic absorption spectroscopy were used to directly probe the nature of DHB-binding to DHBD under anaerobic conditions. UVRRS experiments were performed using custom designed optical fiber probes which allow for very rapid signal acquisition. Spectra of neutral, monoanionic, and dianionic DHB in solution were compared with difference spectra between the free enzyme and the enzyme-substrate complex. Both UVRRS and electronic absorption results are consistent with monoanionic binding of the substrate. For example, in samples of neutral, monoanionic, and enzyme- bound DHB, respectively, a Raman band at c.a. 1300 cm ~ shifted approximately 20 cm 1 when the sample was prepared using deuterated buffer. These and other DzO-induced changes in the Raman spectra of the bound substrate rule out the binding of the latter as a dianion. The data further indicate that the two rings of the enzyme-bound DHB are orthogonal to each other, consistent with crystallographic data. In summary, the results provide direct evidence that the catecholic substrate of extradiol dioxygenases binds as a monoanion. Comparison with the dianionic binding mode of the substrate in Fe(III)-containing intradiol dioxygenases will be discussed. (This research was funded by NSERC of Canada, CFI, and BCHRF).


N M R studies on the interaction of angiotensin II

with fragment peptides of the rat angiotensin II receptor AT1a

Daniela Valensin, Nicola D'Amelio, Elena Gaggelli, Nicola Gaggelli, and Gianni Valensin Department of Chemistry and the NMR Center, University of Siena, Via A. Moro, Siena 53100, Italy.

Interaction between Ang II and fC74°°4:° was demonstrated by relaxation measurements, NOE effects and chemical shift variations. Dipolar cross-relaxation rates of HN-H= pairs were measured by double-selective longitudinal relaxation rates in order to determine backbone inter-proton distances for bound Ang II. The correlation times modulating dipolar interactions for the bound and free forms of Ang II were estimated by the ratio of the non-selective and single- selective longitudinal relaxation rates. Among the intermolecular NOEs observed in NOESY spectra, those between HN protons of 3TyrfcT and 4Tyrang, 9Lysfc T and 6Hisang, ~°PhefcT and Spheaag, indicated that Ang II aromatic residues are directly involved in the interaction, as also verified by relaxation data. Some f f T 3°°'32° backbone features were inferred by the CSI method revealing that the fragment is mainly in helical conformation at pH = 4.0 and T= 318 K and that binding of Ang II does not alter this structure significantly. Restrained MD using the simulated annealing protocol was performed with intermolecular NOEs as constraints and a "frozen" backbone structure. One strongly preferred interaction was found that allows inter-molecular stacking between aromatic rings and forces the peptide to wrap around the 6Leu side-chain of the receptor fragment.

1. Timrnermans P.B., Wong P.C., Chiu A.T., Herblin W.F., Benfield P., Carini D.J., Lee R.J., Wexler R.R., Saye J.A. and Smith R.D., Pharmacol.Rev., 45,205-251(1995).

2. Hunyady L., Bor M., Baukal A. J., Balla T. and Catt K., J. Biol. Chem., 270, 16602-16609 (1995). 3. Franzoni L., Nicastro G., Perthinez T.A., Tat6 M., Nakaie C.R., Paiva A.C.M., Schreier S. and Spisni A., J.Biol.

Chem., 272, 9734-9741(1997). 4. D'Amelio N., Gaggelli E., Gaggelli N., Valensin D., Valensin G., Lozzi L. and Neri P., J.Biol.Chem., submitted.

Design and synthesis of a new class of DNA-binding dinuclear ruthenium complexes

Karlijn van der Schilden, Aldrik H. Velders, Jaap G. Haasnoot, Jan Reedijk Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA, Leiden, The

Netherlands (e-mail. [email protected], nl)

One class of novel anticancer compounds comprises the dinuclear and trinuclear platinum and ruthenium complexes. These polynuclear complexes are of special interest, because they are capable of molecular interactions with biomolecules not accessible to monomeric complexes, thereby achieving a possible alteration of the anticancer activity.

We developed a strategy for the synthesis and characterization of a new series of dinuclear compound¢. A new dinucleating ligand, bis[4'-(2,2':6',2"-terpyridyl)] diethyleneglycolether (dtdeg), has been used to synthesize dinuclear ruthenium complexes based on the mononuclear complexes mer-[Ru(tpy)C13] and [Ru(bpy)(tpy)C1]C1 (tpy = 2,2':6',2"-terpyridine, bpy = 2,2'-bipyridine) of which the former has been shown to be antitumor active 2. To define relationships between structure, DNA- binding mode and antitumor activity for this new series of compounds, both coordination spheres have been varied. The syntheses of the dinuclear complexes and their characterization with (paramagnetic) NMR techniques will be presented.

N 0 0 ~ 0

N-- --N

dtdeg

1. Velders, A. H., PhD Thesis, Leiden University (2000) 2. Novakova O., Kasparkova J., Vrana O., Vanvliet P. M., Reedijk J. and Brabec V., Biochemistry, 34, 12369-12378 (1995)

We thank Johnson & Matthey Chemicals for a generous loan of RuC133H20. This work was supported by the Council for Chemical Sciences of the Netherlands Organization for Scientific Research (NWO). COST is gratefully acknowledged.


Activity of metal complexes of acyclovir against herpes simplex virus 1 (HSV 1) infection in cultured cells

• a t iana L. V a r a d i n o v a a, Pe t ia D. G e n o v a a, A n g e l G a r c i a - R a s o b, Juan J. F io l 2, A n g e l T e r r o n 2, R o s a C o n s b,

M i g u e l Q u i r o s c '~ Laboratory of Virology, Faculty of Biology, Sofia University, 8 Dragan Tzankov Blvd., 1421 Sofia, Bulgaria, e-mail. [email protected] b Departament de Quimica, Universitat de les llles Balears, 07071 Palma de Mallorca, Spain Departamento de Quimica Inorganica, Faculty de Ciencias, Universidad de Granada, 18071 Granada, Spain

it is well known that the activity of organic drugs can be modulated when bonding to a proper metal ion. Thus, we previously showed that Cu-ACV complexes are more active against HSV1 than ACV alone (1). In the present study we continue our investigations on metal-ACV complexes in order to evaluate comparatively whether the bioactivity of ACV could be modulated by metal ions such as Zn(II), Ni(II), Cd(II), Co(II) and Ag(II). In antiviral experiments compounds were applied in maximal non-toxic (MNC) and lower concentrations. Selective indexes (SI) calculated as CC50 (concentration required to reduce cell viability by 50%) to ICs0 (concentration required to reduce virus yield by 50%) ratio, were indicative for anti-HSV 1 activity. It was found that : (i) when bond to Zn(II) the anti-HSV activity of ACV is increased up to 5 times as compared to that of ACV applied alone; (ii) [Cd(ACV)C12] was indifferent to HSV 1 infection; (iii) under the action of [Ni(ACV)(NO3)]3.5H20 infectious virus yield was up to 80% higher than that in viral control. These, as well as previously reported (1), are the first comparative data showing that the anti-HSV activity of ACV can be increased when bonding to the proper metal ion.

• Panteva M., Varadinova T., Turel I. MBD, 5, 1, 19o23 (1998)

Antitumour and antiviral activity of mixed-metal Cu/Co complexes with aminoalcohols obtained by direct synthesis

O . Y u . V a s s i l y e v a a, V . G . M a k h a n k o v a a, V . N . K o k o z a y a, A.L. B o y k o b, V,P. P o l i s h u k b, W . L i n e r t c ': Department of Inorganic Chemistry, National Taras Shevchenko University, Volodimirska str. 64, 01033 Kyiv, Ukraine "~ Department of Biology, National Taras Shevchenko University, Volodimirska str. 64, 01033 Kyiv, Ukraine ~ blstitute of Inorganic Chemistry, Vienna University of Technology, Getreidemarkt 9/153 A - 1060 Vienna, Austria

Mixed-metal complexes have received considerable attention particularly in view of their occurrence in metalloprotein active sites where the catalytic function depends on cooperation between two or more metal centres. The reactions of direct synthesis have been developed and successfully employed to obtain mixed-metal complexes• A number of Cu/Co compounds have been synthesised under one-step interaction of copper powder with cobalt salts in non-aqueous solutions of aminoalcohols: [CuzCoX2(LI)3(OH)]2nSolv, [CuCo(HzLZ)(L2)z]2XznSolv, CuCoXz(H2L3)2 HL I - 2-dimethylaminoethanol, H2 L2 - diethanolamine, H~L 3 - triethanolamine; X - CI, Br, I, SCN, CHaCO0; Solv - CH3CN, CH3OH, DMF, DMSO. Some examples of crystal structures will be presented.

Antitumour activity of mixed-metal complexes was studied using experimental transplanted tumors of mice - Lewis carcinoma (3LL) and solid melanoma (B16). It was found that Cu/Co complexes with diethanolamine decreased the tumor growth (from 71 to 100% for 3LL and from 87 to 100% for BI6).

The investigation of antiviral activity was carried out by a method of plants - indicators on the modeling system "virus - plant" (Nicotiana rustica and Datura stramonium). The antiviral activities of the Cu/Co complexes with diethanolamine and triethanolamine with respect to these viruses vary in the range 12 - 84%. The work was in part supported by the Science and Technology Center in Ukraine (Project Gr-32j).

~0(5~


SOD-like activity of copper(II) complexes of J3-cyclodextrins functionalized with carnosine

G. Vecchioa,D. La Mendola a, E. Rizzarelli a'b, S. Sortino a "Dipartimento di Scienze Chimiche, Universit5 di Catania, Idle A. Doria 8, 95125, Catania, Italy ([email protected]); blstituto per lo Studio delle Sostanze Naturali di Interesse Alimentare e Chimico Farmaceutico, CNR, Idle A. Doria 8, 95125 Catania, Italy.

Oxidation mediated by superoxide is currently believed to participate in the phatogenesis of a number of important degenerative diseases. The application of SOD enzymes has been shown to be effective, but complications in clinical trials (such as immunogenic response) limit the use of SOD for the treatment of human diseases. Recently a number of low molecular weight SOD mimics have recently been investigated as promising pharmaceutical agents which could be advantageously used instead of SOD enzyme I. Bearing the above in mind, in this study copper(II) complexes of [3-cyclodextrm monofunctionalized with camosine were synthesized as SOD models. The dipeptide carnosine has a number of biological roles including the control of both the intracellular concentration of metal ions and the ROS 2. Functionalization with cyclodextrin could protect the moiety camosine against degradation due to the camosinase enzyme. The SOD-like activity of copper(II) complexes of carnosine derivatives were determined by means of the pulse radiolysis technique. The Of scavenger ability shown by these complexes together with the biological activity of the ligands alone against the OH radicals, render these systems promising in the field of SOD synzyme.

1 D.P.Riley Chem.Rev, 99, 2573-2587 (1998). 2. Boldrev A.A., (Eds) Biological Role of Camosine in the Functionalizing of Excitable Tissues, Biochemistry (Moscow) vol 65, 749 (2000).

Design of biomimetic nucleases: dinuclear iron complexes as hydrolytic species

Francois Verge, St6phane M6nage and Marc Fontecave Laborato ire de Chimie et B ioch imie des Centres Redox Biologiques, UMR CNRS 5046, UniversitO Joseph Fourier , DBMS/ C B CEA-grenoble , bat iment K', 17 Avenue des Martyrs , 38054 Grenoble Cedex 9. E-mail: s m e n a g e @ c e a . f r

Cleavage of P-O bond is a key reaction for life, in particular in DNA chemistry. Nature has evolved a number of enzymes such as restriction endonucleases and topoisomerases that catalyze DNA hydrolysis. Few / / / ' ~ synthetic complexes have been reported as capable for DNA hydrolysis and most of them ~ ~

N / are dinuclear metal centers, revealing the importance of their cooperativity in an N . ~ I I I ~ / O ~ [ijy ~ intramolecular nucleophilic attack of the phosphoester bond. 1 ,~ ~ 1 " re t \ F~_~_ , We have previously demonstrated that a dinuclear Fe(III) complex, t " - - - / \ / \ ~ ' ) IFe20(L)4(H20)(OH)] 3. (L = dinitrogen binucleating ligands), a catalyst reproducing k,,._., b N H O / N ,._./

partly the active center of purple acid phosphatase (PAP), was capable of hydrolysis of \ / / phosphodiesters. 2 One aspect of the structure of PAP active sites is theft disymmetry (in ~ i~'.~o fact often two different metals) and we have tried to address the influence of such a ° ' / V R structural parameter in our catalyst by generating two different coordination spheres. As oR expected, the kinetics of hydrolysis ofphosphodiesters was enhanced at least by one order of magnitude and we will show a combinationarial approach to select the most efficient ligand to introduce in the coordination sphere. Based on these results, we will show that the most efficient catalyst is able to hydrolyse double-stranded DNA.

1. Sreedhara A. and Cowan, J. A. J. Biol. Inorg. Chem, 6, 337-347 (2001) 2. Toia C., M6nage S,, Vincent J. M., Averbuch-Pouchot M.T., Latour J. M. and Fontecave Marc Inorg. Chem., 32,

6148-6149 (1997)


Synthesis of mixed 2-(2r-pyridyl)quinoxaline-dithiolene ligand complexes of Re and Mo and their characterization

Irene Veroni , Chr is t iana .A. Mitsopoulou, C. Dagas

Inorganic Chemistry Laboratory, Department of Chemistry, University of Athens, Panepistimiopolis, Zografou 15771 , Hellas (email: [email protected])

On one hand it is wellknown the interesting bioinorganic activity of molybdenum and rhenium as well as the use of oxomolybdenum dithiolene complexes as models in oxygen transfer reactions. On the other hand quinoxalines, as natural products, are compounds of particular interest for biochemistry ~ and material science 2'3 and their study as ligands in metal complexes is extremely prominent.

Herein we present the synthesis and characterization by spectroscopic methods of some novel complexes of Mo and Re with mixed 1,2 dithiolene and quinoxaline ligands. Following a thermal high yield procedure, we have been able to prepare complexes of the previous type. 1H-, t3C- and 2D NMR techniques as well as FT- IR, UV-Vis, and Es-MS have been employed for complexes' characterization

1. S.Kasselouri, A.Garoufis, A.Katehanakis, G.Kalkanis, S.P.Perlepes, N.Hanjiliadis, Inorg. Chim. Acta, 207, 255-258 (1993). 2. M.Innoue, M.Kubo, Coord.Chem.Rev., 21, 1-24 (1976). 3. E.Hyde, J.R.Kalman, D.H.Williams, D.G.Reid, R.K.Olsen, J.Chem.Soc.Perkin Tram.I, 1041- 1048, (1982).

We thank the Special Research Account of Athens University for financial support.


A diiron center in a 13-1actamase-like fold is responsible for oxygen reductase activity in the emerging family of mosaic proteins, the A-type flavoproteins

J.B. Vicente , a C.M. G o m e s , a A. Wasserfa l len , b L.M. Saraiva, a M. Teixeira . a

a Ins t i tu to de T e c n o l o g i a Quimica e Biol6gica , Univers idade Nova de Lisboa, Rua da Quinta Grande 6, Apt. 127, 2780-1 56, Oeiras , Por tugal , (e-mai l : j v i c en t e@i tqb . un l . p t ) blnst i tut f i ir Mikrob io log ie , E idgen6ss i s che Technische Hochschule , ETH, Swi t ze r land

The emerging family of A-type flavoproteins (ATF) consists of mosaic proteins containing multiple distinct domains fused together[i]. The structural prototype is the D.gigas rubredoxin:oxygen oxidoreductase[2]. Here we report two other ATFs, a flavorubredoxin (F1Rd) from E.coli [3] and an ATF from Synechocystis sp. (SsATF). F1Rd is involved in an electron transfer chain along with its flavoprotein reductase partner and it has a C-terminal rubredoxin unit fused together with the ATF signature, which consists of a flavodoxin-like and a [3-1actamase-like domains, whose binuclear site binds iron and is responsible for dioxygen reductase activity. SsATF is yet another example of domain fusion among this family, having a C-terminal putative reductase module fused with the ATF unit. Sequence alignments showed that the C- terminal unit is homologous to NAD(P)H:flavin reductases and also to the N-terminal of Moorella thermoacetica high molecular weight mbredoxin, thus suggesting that it may act either as a mbredoxin reductase or a flavin reductase. Truncated forms of both ATF were obtained, namely F1Rd's ATF and mbredoxin domains, and SsATF's reductase module, thus allowing, through spectroscopic and biochemical studies, the establishment of the role of each unit (and its cofactors) in electron transfer leading to oxygen reduction.

1. Gomes, C.M., et al. (1999) Flavins and Flavoproteins (Ghisla, et al. Eds.) pp. 219-222, Agency for Scientific Publications, Berlin 2. Frazao, C., et al. (2000) Nat. Struct. Biol. 7, 1041-1045 3. Gomes, C.M. et al. (2000) Biochemistry 39, 16230-16237

Investigation of radical formation from the reaction between tert-butyl hydroperoxide and iron porphyrin in solution and encapsulated in silica matrix

by the sol-gel process

E. A. Vidoto a, Y. Iamamoto", G.G. Pereira b and O. R. Nascimento b. ~University o f S6o Paul, Av. Bandeirantes , 3900, Zip. 14040.90, Ribe irdo Preto - SP, Brazil, bUniversi ty o f S~o Paulo - Av. Trabalhador S~oCarlense , 400 - CP 369, Zip. 13560.970, Sdo Carlos, SP, Braz i l (e-mail: eav ido to@yahoo .com)

There is an increasing interest in the investigation of cytochrome c by tert-butyl hydroperoxide in order to understand the peroxidation process of mitochondrial membranes when exposed to oxidative stress. Besides this biological relevance, another subject is the mechanism of O-O bond cleavage of hydrogen peroxide and tert-butyl hydroperoxide when catalyzed by metalloporphyrins. Iron porphyrins molecules immobilized in the silica-based porous sol-gels consist of a good system for to study these reactions. This hybrid organic-inorganic material is stable and transparent, which has been shown to be relatively inert while allowing encapsulate proteins to retain their structure and reactivity. We have been studied the reaction between tert-butyl hydroperoxide and iron(III) meso-tetramethylpyridilporphyrins (FeTMPyP) in solution and encapsulated in silica matrix by the sol-gel process. The UV-Vis spectra evidenced the FeW(O)P species as intermediate. The EPR studies shown initially the disappearing of high spin Fem signal, indicating the formation of EPR silent species and the appearance of an anisotropic radical. We also detected the FeW(O)P °+ species and other different radical, depending on the preparation conditions. Acknowledgment: (FAPESP, CNPq and CAPES)

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