Indi an Journal of Chemistry Vol. 41A, January 2002, pp. 98-142 Posters Oxovanadium(IV) complexes of bioinorganic relevance: Synthesis and characterization of some oxovanadium(IV) complexes involving schiff bases derived from biologically active 4-benzoyl-3-methyl-l-phenyl-2-pyrazolin-5-one and certain aromatic amines R C Mauryu*, H Singh, T Singh & A K Singh Coordination Chcmistry Laboratory, Dcpartlllent of PG Studics and Research in ChcmiSll"y. RD Univcrsity, Jabalpur 482 001 (MP). India Recognition of vanadium as an essential trace element found in living organisms i has generated increasing interest in the structure and function of its complexes. Tunicates accumulate vanadi um(V) from the marine environment and store it in their blood cells in the reduced tetra- and tri-valent states. The mushroom 2 accumulates vanadium to produce amavadin . Spectroscopic investigati ons have shown a distinct preference of 3 this metal center for N-and/or O-coordinated environments . There is increasing interest in the biological chemistry of vanadium due to the discovery of two types of vanadium dependent enzymes: vanadium nitrogenase and vanadium bromoperoxidase. Although in recent years a number of vanadium complexes have been synthesized and characterized as models of amavadin and vanadium dependent metalloenzymes, the biological role of vanadium in li ving organisms and also in both reductive and oxidative catalytic transformations is still debatable, and not c1 ear3. Since the seventies, vanadium has been associated with insulin and its role in the body. The recently reported4 and structurally documented bis(maltolato)oxovanadium(IV) (BMOV) has been found to be effective to regulate glucose levels in the plasma in di abetic rats with no significant toxic effects on hepatic and kidney functions. In view of the above, the spectral and magnetic behaviour of some oxovanadium(lV) complexes in N,O­ and N20 2- type schiff base environments have been studied. The schiff bases were prepared by the condensation of 4-benzoyl, -3-methyl-l-phenyl-2-pyrazolin-5-one with certain aromatic amines, viz, p-anisidine, /11- phenitidine, p-toluidine, a-phenylenediamine, m-phenylenediamine, p-phenylenediamine or benzidine. The bi­ and tetra-dentate schiff bases were reacted with vandal sulphate in 2: 1 and 1: 1 mole ratio to obtain mononuclear and ligand bridged binuclear complexes. All the complexes have been characterized by analytical data, molar conductance and magnetic measurements, IR, UV -vis and EPR spectral studies. References I Rehder D, Angew Chern Jnt Ed Engl, 30 (1991) 148; Butler A & Walker J Y, Chern Rev, 93 (1993) 1937. 2 Kneifel H & Bayer E, Angew Chern lnt Ed Engl, 12 (1973) 508. 3 Dai J, Wang H & Mikuria M, Polyhedron, 15 (1996) 1801 and references cited therein. 4 Burgess J, De Castro B, Oliveira C, Ramgel M & Schlidwein W, Polyhedron, 16 (1997) 789 and references cited therein. A model study for vanadium protein interactions: Synthesis and characterization of oxovanadium (IV and V) complexes with L-carnosine Asit R Sarkar* & Shipra Mandai Department of Chemistry, University of Kalyani, Kalyani 741 235, WB, India The binding of a metal ion by a protein may principally involve ionisable side chains and the -NHCO group of the peptide chain backbone'. The axial coordination of histidine to the vanadium center in haloperoxidases has increased the interest in the interactions of vanadium with ligands containing the imidazole moietl. Most of the POSTERS 99 reported investigations in this field are on mixed ligand vanadium (IV and V) complexes with amino acids or its adducts in solution3 The reports on the interactions of vanadium with peptides containing the imidazole moiety 4 in the solid state are scanty. Till date there is no report on the interaction of vanadium (IV and V) with the ligand L-carnosine ( ~-al a nyl-L-hi st idin e), which itself is a ligand of biochemical importance5 In the present work, potential metal binding sites of L-carnosine wi th respect to vanadium have been investigated. Two novel oxovanadium complexes containing dideprotonated L-carn osine anion were isolated havin g the composition NH4[V02L]. 2H20 and VOL. 2H20, where H2L =L-carno sin e. The infrared spectra of th e complexes indicate th at the dideprotonated L-carnosin e coordin ates to va nadium in both the complexes through the three donor atoms, namely the oxygen of th e carboxylate group, two nitrogens one each from the primary amine and the other from the amide group of the ligand. The pattern of shi ft of the I3C NMR signal for the C(2), C(4) and C(S) 6 signals for the complex NH4[V02L]. 2H]O, with respect to the free li gand indicates that the imidazole moiety of L-carnosine has, undergone tautomeric change from N(3)-H to N(l) - H. The nitrogen donor atom of the imidazole moiety coordinates to vanadium through N(3). The EPR spectrum of the complex VOL. 2H20, ex hibits eight resonance li nes in accordance with the presence of vanadiu m(IV) species in the complex, whi ch is consistent with the observed magnetic moment (l 74 BM). The cyclic voltammogram of th e complex shows the presence of a reversible redox couple involvi ng one electron transfer. References I Cams DC. Holst H, Keramidas A D & Rehder D, In org Chelll. 34 ( 1995) 2524. 2 Mukherjee J, Gangul y S & Bhattaeharjee M, Indian J Ch el1l, 35A (1996) 47 1. 3 Elvin gson K, Keramidas A D, Crans D C & Pelt ersson L, Inorg Ch ell7 , 37 (1 998) 6153. 4 Keramidas A, Miller S M, Anderson 0 P & Crans DC, J AI1I chelll Soc, 11 9 (1997) 8901. 5 Kochen R, Yamamoto Y, Cundy K C & Ames B N, Proc Natl Acad Sci, USA, 85 (1988) 3 175. 6 Sarkar A R & Sarkar M, J chem. Research (5), (1997) 304. Chromium(III) induced long range ordering of collagen: A step in exploring a unified theory for tanning Raghuraman Gayatri, Rama R ajaram & Thirumalachari Ramasami* Central Leather Research Institute, Adyar, Chennai 600020, India Stability against enzymatic degradation of collagen and dimensional changes of skin forms the basic principle of tanning. A mixture of Il-hydroxy species bearing dimeric, trimeric, tetrameric and higher oligomeric structures of chromium(III) is used in commercial tanning process. We have recently demonstrated that the different chromium(III) complexes, viz, [(H20)4Cr(OHhCr(H20)4t+ 1 (dimer), [Cr3(OHMH20)9]5+ 2 (trimer) and [Cr4(OHMOhCH20)u]4+ 3 (tetramer) present in commercial tanning salts are capable of inhibiting collagenase activity employing different mechanisms. An explanation for the stability of chrome tanned rat tail tendon (RTT) collagen against enzymatic attach has been offered. In the present work, an attempt has been made to investigate the ultra- and micro-structural changes in collagen induced by different chromium(III) complexes of relevance to tanning by employing circular dichroism (CD) and atomic force microscopy (AFM) techniques. Significant changes in CD spectra are observed when collagen solution is treated with dimer, 1 and trimer, 2. On the other hand, the interaction of collagen with tetramer, 3 does not influence the CD spectra of the protein sample. The influence of the secondary structural changes on the quaternary structure of the protein has been addressed using AFM technique. The studies reveal changes in the D-periodicity of RTT fibre treated with different species of chromium(III). Differences in topological distribution as well as the nature of reaction of various chromium(III) complexes with collagen may be responsible for such observations. Studies with monomeric collagen in solution provide convincing evidence for the chromium induced self-assembly of the protein into supramolecular aggregates with an axial repeat of 64±2 nm in the case of dimer, 1 and 72±1 in the case of trimer, 2. The studies indicate that a unified theory of tanning may include the level of conformational changes and induced long range ordering in the protein, collagen. 100 INDIAN J CHEM, SEC. A, JANUARY 2002 Influence of ligand environment in the induction of apoptosis by Cr(Ill) compounds K Balamurugan, Rama Rajaram & T Ramasami* Chemical Laboratory, Central Leather Research Institute, Chennai 600020, India The redox state and the speciation of chromium involved in generating mutagenicity and carcinogenicity in living systems have attracted wide interest. The biotoxicity of chromium is in focus; but the underlying mechanisms for the observed toxicity is not well-understood. In one of our earlier studies, we have demonstrated the influence of Cr(lll) to cause apoptosis in human lymphocytes and afforded the species specific explanation. In the present study the influence of trisphenanthrolinechromium(III) 1, trisbipyridinechromium(III) 2 and aquapentamminechromium(III) 3, has been evaluated, for their effect on cell culture systems involving human peripheral blood lymphocytes. Complexes 1 and 2 bring about inhibition of DNA synthesis as assessed by eH]­ thymidine incorporation and decrease in viability of cells in a dose-dependent manner (5-50 MM). It is found that apoptosis is brought about by these Cr(lll) complexes as verified through DNA fragmentation and by morphological studies. Complex 3 is inefficient in inducing apoptosis. The complexes 1 and 2 can, in principle, participate in redox processes generating radical species, which can induce mutagenicity of Salmonella typhymurium. Whether redox pathways are responsible for switching on the genes up-regUlating apoptosis is being addressed in this work. Studies to experimentally investigate the formation of oxygen radicals in vivo in cell culture systems are being carried out. The interaction of chromium(III) schiff base complexes with DNA R Vijayalakshmi, M Kanthimathi, V Subramanian & Balachandran Unni Nair* Chemical Laboratory, Central Leather Research Institute, Chennai 600020, India The binding of schiff base complexes of chromium(III) of the type [Cr(salen)(H20)2t and [Cr(salpm)(H20ht [where salen denotes 1,2 bis(salicylideneamino)ethane and salpm denotes 1,3 bis(salicylideneamino)propane] to calf thymus DNA has been investigated by absorption and emission spectra, circular dichroism, melting temperature and viscosity measurements.