Search

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.

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.