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The set of mixed valence bis(tetrathiafulvalene) bis(TTF) compounds are prepared from the TTF-type synthon. The bis(TTF) compounds demonstrating four reversible sequential one-electron oxidation steps have two identical electrophores associated by an aromatic link. The electrochemically obtained radical cations from mixed valence compounds are the intervalence transitions. Non-adiabatic coupling occurs between the multiple low-lying excited states and ground states of the open-shell species.

Nucleophilic substitutions of a sequence of gem-dihalogenated alkenes with 1,2-benzenedithiolate were studied. The progress of the reactions and the structures of the yielded products are altered, depending on the structures of the R groups. At the AM1 level, the energy contents of the anionic intermediates obtained from the additions of the nucleophile 1, 2-benzenedithiolate to the unsaturated centers were estimated in the frame of the addition-elimination-type process for these nucleophilic substitutions. The estimated energies are fairly consistent with experimental findings for four compounds.

The study evidence related to the interaction between the indole group of Trp154 and the carboxylated lysine which is critically essential for the stability of the posttranslationally modified Lys70 in the class D [beta]-lactamase OXA-10 catalysis is reported. The result obtained offer insight into the important role of the Lys70 carboxylation during the deacylation step and emphasize the importance of Trp154 for the ideal positioning of active site residues leading to an optimum activity.

The energies of the fundamental and several excited states of tetrapeptide radical cations were determined at the outer valence green's function (OVGF) level. It was found that, from a purely energetic point of view, a charge initially created on the tyrosine chromophore could migrate without any geometrical change and without further activation once the excited electronic state of the ionized chromophore was formed.

The electronic structure of the radical cations of the DNA base is investigated using ab initio calculations. The proposed optimized medium size basis set, as exemplified by the calculation of ionization potentials of a stacked dimer of guanines, renders possible the study of larger ionized systems related to DNA.

Replacement of the catalytic cleft active site residues Lys38, Ser96 in the Streptomyces K15 DD-transpeptidase almost completely abolishes the penicillin binding and impairs the transpeptidase activity, while the Cys98 replacement decreases transpeptidase activity and increases hydrolysis of the thioester substrate. However, their role in the catalytic mechanism itself is uncertain.

Abstract: The triplet Hartree–Fock (HF) instability is investigated through the examples of substituted ethylenes and the small linear conjugated systems butadiene, hexatriene, octatetraene. A statistical analysis is performed for several conformations of the latters. The second eigenvalue of the instability matrix appears to be able to discriminate the groups of unsaturated compounds. The HF instability is largely influenced by conjugation and mesomeric effects and thus by the geometry. The number of π electrons is also an important factor. The electronic correlation related to the HF instability is not quantified by the energy difference between the post-HF and HF levels. [Copyright &y& Elsevier]

Although commercialized inhibitors of active site serine beta-lactamases are currently used in coadministration with antibiotic therapy, no clinically useful inhibitors of metallo-beta-lactamases (MBLs) have yet been discovered. In this paper, we investigated the inhibitory effect of mercaptophosphonate derivatives against the three subclasses of MBLs (B1, B2, and B3). All 14 tested mercaptophosphonates, with the exception of 1a, behaved as competitive inhibitors for the three subclasses. Apart from 13 and 21, all the mercaptophosphonates tested exhibit a good inhibitory effect on the subclass B2 MBL CphA with low inhibition constants (K(i) < 15 muM). Interestingly, compound 18 turned out to be a potent broad spectrum MBL inhibitor. The crystallographic structures of the CphA-10a and CphA-18 complexes indicated that the sulfur atom of 10a and the phosphonato group of 18 interact with the Zn(2+) ion, respectively. Molecular modeling studies of the interactions between compounds 10a and 18 and the VIM-4 (B1), CphA (B2), and FEZ-1 (B3) enzymes brought to light different binding modes depending on the enzyme and the inhibitor, consistent with the crystallographic structures.