Bovine serum albumin +reductant systems

Although similar efforts have been devoted to related polymer systems (Overberger and Cho, 1968 Overberger and Dixon, 1977 Okamoto, 1978), large enantioselectivity has not been observed. Goldberg et al. (1978) conducted borohydride reduction of phenyl ketones in micelles of the chiral surfactant [44]. The result was disappointing, since the maximal enantioselectivity was only 1.66% for phenyl propyl ketone. A much better optical yield was reported when this reaction was carried out under phase-transfer conditions (Masse and Parayre, 1976). The cholic acid micelle and bovine serum albumin exhibited the relatively high enantioselectivity in the reduction of trifluoroacetophenone (Baba ef al., 1978). 

An experimental complication is the difficulty in effecting molecular interaction between the components. The usual technique for preparing lipid-protein phases in an aqueous environment is to use components of opposite charge. This in turn means that the lipid should be added to the protein in order to obtain a homogeneous complex since a complex separates when a certain critical hydrophobicity is reached. If the precipitate is prepared in the opposite way, the composition of the complex can vary since initially the protein molecule can take up as many lipid molecules as its net charge, and this number can decrease successively with reduction in available lipid molecules. It is thus not possible to prepare lipid— protein—water mixtures, as in the case of other ternary systems, and to wait for equilibrium. Systems were prepared that consisted of lecithin-cardiolipin (L/CL) mixtures with (a) a hydrophobic protein, insulin, and with (b) a protein with high water solubility, bovine serum albumin (BSA). 

The most efficient system of this type is obtained by the reduction of bovine serum albumin in the presence of molybdate. Apparently disulfide links in the peptide are broken and form thiolate groups which then bind molybdenum. In a borate buffer, this system will reduce dinitrogen and acetylene, although not using dithionite as an electron source. The turnover is similar to that of the iron-molybdenum cofactor (see Section XII), and dinitrogen reduction is inhibited by carbon monoxide and stimulated by ATP. The yield of ammonia is linearly dependent upon PN2, and the yield is also depressed in the presence of fumarate and, more surprisingly, succinate. It is calculated that the... 

Many investigators have shown that nonspecific reagents as diverse as calcium phosphate gel, EDTA, histidine, and nonspecific proteins activate succinoxidase preparations in otherwise unfavorable environments. The mechanism of the activation is not established, but it has been repeatedly suggested that the activators in some manner influence the steric orientation of components of the particulate succinoxidase. Another component of electron-transport systems has been implicated by Nason and Lehman. DPNH oxidation by a particulate fraction of rat muscle was found to be decreased by extraction of 10 per cent of the lipid with isooctane the activity was restored by addition of a-tocopherol (vitamin E) or the lipid extracted from muscle or bovine serum albumin. These lipids are able to reverse the inhibition of cytochrome c reduction caused by antimycin A. It has not been determined whether the tocoph-... 

In the present study, the equilibrium surface tension reduction of adsorbed films from mixtures of proteins and lipids possessing different interactions in bulk solution are reported. The systems investigated are bovine serum albumin (BSA) and ovalbumin (OA) in sodium dodecylsulphate (SDS) and OA in 1-monocaproin. The interaction between SDS and proteins are well documented in literature and reviewed in reference [8]. SDS is known to bind to most proteins in a nonspecific, co-operative manner, thereby gen-... 

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