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The mechanism for [H.sub.2] cleavage in NeFe-hydrogenase is reinvestigated with large models by using both hybrid density functional theory (DFT) by itself, or in a quantum mechanics (QM)/molecular mechanics (MM) scheme following the ONIOM approach. The studies have shown that the ONIOM results for the reaction mechanism in NiFe-hydrogenase had to be corrected by large model DFT results, which is due to overestimation of polarization effects of the QM region by the MM region.

The molecular dynamics (MD) simulations were used to study residues in and surrounding the active site and domain movements to gain insight into the role of catalytic mechanism of wild type Escherichia coli biotin carboxylase. The results obtained for the active-site interactions and dynamics of WT biotin carboxylase provide the insight into the design and interpretation of further experiments.

Friedel-Crafts acylation has been known since the 1870s, and it is an important organic synthetic reaction leading to aromatic ketone products. Friedel-Crafts acylation is usually performed with carboxylic acid chlorides or anhydrides, while amides are generally not useful substrates in these reactions. Despite being the least reactive carboxylic acid derivative, we have found a series of amides capable of providing aromatic ketones in good yields (55-96%, 17 examples). We propose a mechanism involving diminished C-N resonance through superelectrophilic activation and subsequent cleavage to acyl cations.

The infrared spectrum of phosphoenol pyruvate (PEP) in aqueous solution was studied experimentally and theoretically in its fully ionized, singly protonated and doubly protonated form. The density functional theory with the B3LYP functional and with the 6-31G(d,p), 6-31++G(d,p), and 6-311++G(d,p) basis sets were used in the theoretical study. The calculations with the two latter basis sets and the CPCM continuum model for water showed good agreement with the experiments except for vibrations assigned to hydroxyl groups. These needed to be modeled with explicit water molecules. The effects of deuteration and of (13)C(2,3) labeling of PEP were reproduced by the calculations.