Convergence of electric field and electric field gradient versus atomic basis sets in all-siliceous and Mg substituted phillipsites.

Electrostatic potential (EP), electric field (EF), and electric field gradient (EFG) values are calculated in periodic models of magnesium substituted phillipsite (MgPHI) zeolite forms using periodic DFT (PDFT) hybrid B3LYP level with fourteen different basis sets. Relative root mean square differences between the EP, EF, or EFG values estimated between different basis sets are evaluated in several spatial domains available for adsorbate molecules in the zeolite. In these areas, the EF increase in MgPHI is evaluated relative to all-siliceous PHI types. The EP is interpreted in terms of framework ionicity for MgPHI and all-siliceous PHI models. Angular Si-O-Si dependence of the EFG asymmetry at (17)O atoms in all-siliceous zeolites is discussed.

[Enzymic activity of polymer-protein complexes in water-miscible organic solvents]. / Fermentativnaia aktivnost' kompleksov polimer-belok v smeshivaiushch ikhsia s vodoi organicheskikh rastvoriteliakh.

The enzymic activity of noncovalent complexes of alpha-chymotrypsin with polyethylene glycol and a block-copolymer of polyethylene oxide and polypropylene oxide (proxanol) was studied in aqueous-organic media. It was shown that complex formation activated the enzyme in media with a high content of the organic solvent, whereas in systems containing more than 50% water the enzymic activity of complexes was the same as that of the native enzyme. The activation in polyethylene glycol-containing complexes was greater than in complexes with proxanol of the same molecular mass.