Structure parameters of solvated silver(I) ions in eight neat solvents were determined by extended X-ray absorption fine structure spectroscopy. The coordination geometry of the solvated silver(I) ion is four-coordinate tetrahedral at the Ag−O bond distances of 239 pm in trimethylphosphate, 239 pm in N,N-dimethylformamide, 238 pm in 1,1,3,3-tetramethylurea, and 238 pm in dimethyl sulfoxide as oxygen-donating solvents, and at the Ag−N bond distances of 229 pm in acetonitrile, 230 pm in 2-methylpyridine, 229 pm in n-propylamine, and 231 pm in ethylenediamine as nitrogen-donating solvents. According to our present ab initio molecular orbital calculations concerning the structure of the silver(I) ion bound by n molecules of hydrogen cyanide (n = 1−6) and acetonitrile (n = 1−5) in the gas phase, the maximal stabilization for the solvation is observed at n = 4. The results of the theoretical calculations in the gas phase are consistent with the experimental observations in solution.

4-Hydroxy-2-nonenal (HNE), a major racemic product of lipid peroxidation, reacts with histidine to form a stable HNE-histidine Michael addition-type adduct possessing three chiral centers in the cyclic hemiacetal structure. In the present study, we characterized configurational isomers of a HNE-N ␣ -acetylhistidine adduct by NMR spectroscopy and by molecular orbital calculations. In addition, we raised monoclonal antibodies against (R)-HNE-histidine and (S)-HNE-histidine adducts, characterized their specificities, and examined in vivo localizations of each adduct under oxidative stress. To facilitate structural characterization of the configurational isomers of an HNE-histidine adduct, we prepared the (R)-HNE-histidine and (S)-HNE-histidine adducts by incubating N␣ -acetylhistidine with each HNE enantiomer, both of which provided two peaks (Ra and Rb from (R)-HNE-histidine and Sa and Sb from (S)-HNEhistidine adducts) in reversed-phase high-performance liquid chromatography. The NMR analysis showed that each peak was a mixture of two diastereomers. In addition, the analysis of the nuclear Overhauser effect enabled the determination of configurations of the eight isomers. The relative amounts of these isomers in the NMR analysis correlated with the relative energies calculated by molecular orbital methods. On the other hand, using (R)-HNE-modified and (S)-HNE-modified keyhole limpet hemocyanins as the antigens, we raised the monoclonal antibodies, mAbR310 and mAbS412, which enantioselectively recognized the (R)-HNE-histidine and (S)-HNE-histidine adducts, respectively. Among the mixtures (Ra, Rb, Sa, and Sb) of diastereomers, mAbR310 showed the highest immunoreactivity to Rb (the mixture of 2R,4S,5R and 2S,4S,5R isomers), whereas mAbS412 preferentially recognized Sa (the mixture of 2R,4S,5S and 2S,4S,5S isomers). The presence of (R)-HNE and (S)-HNE epitopes in vivo was immunohistochemically examined in the kidney of rats exposed to the renal carcinogen, ferric nitrilotriacetate, by which nuclear and cytosolic stainings with mAbR310 and mAbS412, respectively, were detected.

10261detected by ESR (3%), the second part comprises the electron pairs which participate in superconductivity, and the third part comprises electron spins arranged antiferromagnetically. ColleldoILsDuring about 24 h the ESR signals of Rb3Ca evolve with time. This is suggested to be related to diffusion of the Rb atoms within the Cm crystallites. Near T, the ESR susceptibility is found to change from antiferromagnetic to paramagnetic behavior. The magnitude of the ESR susceptibility is described by a two-component model of localized and conduction electrons. The ESR signals of K3Ca and Cs3Ca also show a similar timedependent behavior. Acknowledgment.Raseinsky, M. J.; Murphy, D. W.; Duclos, S. J.; Lyons, K. B.; Miller, B.; Rosamillia, J. M.; Fleming, R. M.; Kortan, A. R.; Glarum, S. H.; Makhija, A. V.; Muller, A. J.; Eick, R. H.; Zahurak, S. M.; Tycko, R.; Dabbagh, G.; Thiel, F. A. Nature 1991,350,320. (3) Zhakhidov, A. A,; Ugawa, A.; Imaeda, K.; Yakushi, K.; Inokuchi, H.; Kikuchi, K.; Ikemoto, I.; Suzuki, S.; Achiba, Y. Solid State Commun. 1991,

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Five dinitrogen-molybdenum complexes bearing bis(diphenylphosphino)amine derivative ligands (L(R)) that form a unique 4-membered P-N-P chelate ring, trans-[Mo(N(2))(2)(L(R))(2)] (2(R): R = Ph, Xy, p-MeOPh, 3,5-iPr(2)Ph, iPr), were prepared for the purpose of binding a dinitrogen molecule. The corresponding two dichloride-molybdenum complexes, trans-[MoCl(2)(L(R))(2)] (1(R): R = Ph, Xy), were also prepared as comparisons. FT-IR spectra of 2(R) were measured and compared the ν(N≡N) values. Moreover, X-ray crystal structure determination of 1(R) (R = Ph, Xy) and 2(R) (R = Xy, 3,5-iPr(2)Ph) is performed. These experimental results indicated that the coordinated dinitrogen molecule gets easily influenced by the N-substitutent of diphosphinoamine ligand. In addition, to investigate the effect of the properties of the diphosphinoamine ligand for the dinitrogen molybdenum complexes, we performed DFT calculations that focused on the difference of N-substituent, the dihedral angle between P-N-P plane and N-substituent aryl group, and the P-N-P bite angle. This calculation revealed that the competition between the back-donation from metal to dinitrogen and that from metal to ligand was affected by P-N-P bite angle and the dihedral angle of N-substituent of ligand. In order to examine the reactivity with respect to conversion of dinitrogen to ammonia, protonation and trimethylsilylation reactions of the coordinated dinitrogens were carried out for 2(R).

The origin of the inverted tetrahedral configurations of the bridgehead carbons in bicyclo[1.1.0]butane has been investigated in a theoretical manner. The delocalization of σ-electrons between the central C 1 -C 3 bond and the side C 1 -C 2 bonds was found to be bonding to relax the angle strains, while the delocalization between the geminal C-C bonds is antibonding in propane and cyclopropane, etc. The bonding property of the geminal delocalization was shown to be related to the inversion of the configurations. Inverted and normal tetrahedral bridgehead configurations in the bicyclo[1.1.0]butane frameworks were designed by controlling the geminal delocalization and confirmed by ab initio molecular orbital calculations.

Ab initio calculations of 12-crown-4, 15-crown-5, and 18-crown-6 and their protonated species have been performed. As a reference molecule, 1-(2′-methoxy)ethoxy-2-methoxyethane (glyme-2) is also examined. Three protonated crown ethers are found to have quite similar moieties to that of glyme-2H + . The ring strain due to formation of intramolecular hydrogen bonds is a measure of proton affinity (PA) values. The present computational result supports Meot-Ner's and Kebarle's PA values of 12-crown-4. Those of 15-crown-5 and 18-crown-6 reported by Kebarle were very close to the present theoretical values.

We developed a computer program MOLCAT to visualize results of vibrational analysis calculation. This program can treat Z-matrix used in ab initio molecular orbital calculation, and shows the vibrational mode as arrows with the molecular structure. We applied this program to show transition vectors of the intramolecular inversion of ammonia and the water exchange reaction of hexaaquacalcium(II). We are preparing to distribute MOLCAT as a free software.