Step-Wise Computational Synthesis of Fullerene C60 derivatives. 1.Fluorinated Fullerenes C60F2k

The reactions of fullerene C60 with atomic fluorine have been studied by unrestricted broken spin-symmetry Hartree-Fock (UBS HF) approach implemented in semiempirical codes based on AM1 technique. The calculations were focused on a sequential addition of fluorine atom to the fullerene cage following indication of the cage atom highest chemical susceptibility that is calculated at each step. The effectively-non-paired-electron concept of the fullerene atoms chemical susceptibility lays the foundation of the suggested computational synthesis. The obtained results are analyzed from energetic, symmetry, and the composition abundance viewpoints. A good fitting of the data to experimental findings proves a creative role of the suggested synthesis methodology.Comment: 33 pages, 11 figures, 2 tables, 2 chart

Purification and properties of an acid lipase from human gastric juice

An acid lipase (EC 3.1.1.3) from human gastric juice was purified by using poly(ethylene glycol)-6000 precipitation, ethanol fractionation and Sephadex G-75 gel filtration. A molecular weight of 44000 was obtained by SDS-polyacrylamide gel electrophoresis. pH-dependent aggregation was observed and by using Sephadex G-200 gel filtration, a molecular weight of 90000 was obtained at pH 6.0 and 45000 at pH 3.0, for the purified enzyme. A pH optimum of 5.3 was obtained using triolein as substrate. The apparent K<SUB>m</SUB> for tributyrin and triolein was found to be 21 and 73 µ mol, respectively. Diacylglycerol and free fatty acids were the major hydrolytic end products of this enzyme. Studies on the positional specificity of the enzyme showed that the preferred site of hydrolysis was sn-3 and sn-1, although a good percentage of the sn-2 position was also hydrolysed. Conjugated bile salts inhibited the enzyme when triolein was used as substrate, whereas they activated it when tributyrin was used. Some of the properties of the purified human gastric juice acid lipase resembles those of rat and human lingual lipase