REDUCTION REACTIONS OF BOVINE SERUM-ALBUMIN AND LYSOZYME BY CO2- RADICAL IN POLYVINYL-ALCOHOL SOLUTION - A PULSE-RADIOLYSIS STUDY

Pulse radiolytic reduction of bovine serum albumin (BSA) and lysozyme by CO(2)radical anion radical in presence of polyvinyl alcohol (PVA)ha s been studied. At pH 6.8 in presence of 2% (w/v) PVA, reduction of BS A and lysozyme (both at 1 x 10(-4) mol dm(-3)) give an additional tran sient peak at 390 nm along with the usual 420 nm peak. The bimolecular rate constants for the reaction of CO(2)radical anion radical at pH 6 .8 +/- 0.2 with BSA are 2.7 x 10(8) and 7.13 x 10(8) dm(3) mol(-1) s(- 1) at 420 rim and 390 nm respectively. The same for lysozyme are 3.2 x 10(8) and 5.6 x 10(8) dm(3) mol(-1) s(-1) at 420 nm and 390 nm, respe ctively. Dimethyl disulfide also gives 390 nm and 420 nm peaks in this System upon reduction with CO(2)radical anion radical. The 390 nm pea k is ascribed to the sulfenium radical (RSS(H)R), Studies on the varia tion of pH suggests the protonation of RSSR- radical (420 nm) to form RSS(H)R-. radical (390 nm) in this viscous media. The decay of RSS(H)R -. radical occurs via formation of RS' radical and RS(H)S(H)R;;the fin al product being RSH in both cases: (C) 1998 Elsevier Science Ltd. All rights reserved.