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A peptide corresponding to the large intercellular loop that contains a histidine-rich sequence from the first iron-regulated transporter of Arabidopsis thaliana, which transports [Fe.sup.2} ions as well as [Mn.sup.2}, [Co.sup.2}, [Zn.sup.2} and [Cd.sup.2} was prepared and studied to provide a chemical basis for its role in the widespread ZIP family of transmembrane metal-transporting proteins. The histidine-rich sequence was found to have a very high entropy-driven affinity for [Fe.sup.3}, which may have biological significance.

A study uses colorimetric (near-UV absorption spectroscopy) and calorimetric (isothermal titration calorimetry) methods to quantify the equilibrium and thermodynamics of arsenite and monomethylarsenite (MMA) coordinating to glutathione (GSH) and the dithiols dimercaptosuccinic acid (DMSA), dihydrolipoic acid (DHLA), and dithiothreitol (DTT). The findings shows that arsenite and MMA form moderately stable complexes (beta = 10(super 6)-10(super 7) with GSH.

The binding of Ni(II) and Cu(II) to histidine, to the tripeptides His, GlyGlyHis, and HisGlyHis, and bovine serum albumin is studied by isothermal titration calorimetry (ITC) to determine the experimental conditions and data analyses necessary to reproduce liteature values for the binding constants and thermodynamic parameters. Guidelines are developed for accurate ITC measurements of metal binding to biological macromolecules.

Metallohydrolases with two metal atoms held together by bridging ligands have peptidase or phosphoesterase activity. These include enzymes that catalyze the hydrolysis of the C-N bond of urea and guanidine, the N-terminal peptide bond of proteins and the P-O bond of phosphate monoesters. The peptidase hydrolytic activity involves a nucleophilic attack on the carbonyl carbon, whereas in phosphatases the nucleophilic attack occurs at the phosphorous atom opposite the leaving group. Binuclear metallohydrolases contain a metal-bound solvent nucleophile.

Extended X-ray absorption fine structure measurements and spectroscopic studies of three metallothionein (MT) samples having 99Tc reveal that binding between TcO3+ and the protein involves a square pyramidal coordination with equatorial ligands containing 2 O/N donor ligands and 2 cysteine thiolates. Reaction of Zn7-MT with TcO(glucoheptonate)(sub 2)(super -) produces the technetium metallothionein.

Thiolate sulfur of the inhibitor, 2-mercaptoethanol (2-ME), connected the two Ni(II) ions found in the structures of dinuclear Ni(II) active sites of Klebsiella aerogenes and jack bean. X-ray absorption spectroscopy facilitated the study of 2-ME-inhibited and native bacterial plant enzymes. Urease, which catalyzes the hydrolysis of urea to yield carbonic acid and ammonia, is an Ni-dependent enzyme.

The structural properties of the Cr(III)-alkyl complexes (CpCrMeCl)2, (Cp*CrRCl)2 (R= Me, Et, CH2SiMe3) and (Cp*CrMeBr)2 was studied using electron paramagnetic resonance spectroscopy (EPR) spectroscopy. EPR allows scientists to study the electronic properties, structure, bonding and reactivity of paramagnetic organometallic complexes. Results provide insights into the solution structure of coordinatively unsaturated mononuclear Cr(III)-alkyl complexes.

The ability of the [Zn.sup.2+], as well as the monomethlyarsenite (MMA) ions to act as the binding sites in the glucocorticoid receptor (GR) is discussed. MMA is shown to form more stable complexes with the biologically relevant thiol glutathione (GSH), as compared to arsenite.

The effect of oxygen in the EPR spectral properties of wood charcoals is measured and a model based on the properties of charcoals and EPR relaxation mechanisms is developed. EPR line broadening in these materials has correlated with char surface area and the concentration of adsorbed oxygen.

Isothermal titration calorimetry (ITC) is used to quantify the stoichiometry, affinity and thermodynamics of [Ni.sup.2+], [Cu.sup.2+] and [Zn.sup.2+] binding. The stoichiometries and affinities obtained by ITC are in good agreement with the equilibrium dialysis results.

A C[u.sup.2+] titration of Hpn was monitored by EPR spectroscopy to understand the metal coordination of the protein. The histidine-rich cytoplasmic protein Hpn represents a novel class of metal binding proteins with relative binding affinities: C[u.sup.2+] > N[i.sup.2+] > B[i.sup.3+] ~ Z[n.sup.2+].

Experiments were conducted to determine thiosulfinate formation in a protein or peptide. The oxidation of two cysteines in Spl-3 to thiosulfinate was analyzed. Quantitative HPLC analysis on the peptide products rom 24-hour reactions of Spl-3 super 22 with oxygen or hydrogen peroxide in the absence or presence of Zn(II) or Ni(II) was performed. The findings indicated the permanent elimination of thiosulfinate's ability to bind to zinc and interact with DNA.

Reaction of Ti(Cl)(NRAr3) (R = C(CD3)2CH3, Ar = 3,5-C6H3Me2) with sodium amalgam produces Ti(NRAr)3. X-ray crystallography helps determine the structure of Ti(NRAr)3. Synthesis of hetero-binuclear mu-oxo complex involves the reaction of Ti(NRAr)3 with V(O)(O-i-Pr)3. X-ray diffraction and EPR spectroscopy help characterize the hetero-binuclear mu-oxo complex.