Analysis of protein back-extraction processes in alcohol-and carboxylic acid-mediated AOT reverse micellar systems based on structural changes of proteins and reverse micelles

摘要

The effects of the addition of alcohol and carboxylic acid on the back-extraction of several small globular proteins such as beta-lactoglobulin(beta-LG),bovine carbonic anhydrase(CAB),and lipase have been studied using reverse micellar systems(RVMS).The protein back-extraction induced by the addition of alcohol and carboxylic acid was markedly influenced by the structural changes of reverse micelles(beta_t)and protein(m).The alcohols and carboxylic acids suppressing the formation of reverse micelle clusters(positive value of beta_t)remarkably enhanced the back-extraction of proteins.On the other hand,the alcohols and carboxylic acids enhancing the formation of reverse micelle clusters(negative value of beta_t)suppressed the back-extraction of proteins.The markedly effective alcohol and carboxylic acid molecules on the denaturation of proteins(high values of m)suppressed the back-extraction of proteins.The m values were estimated by measuring the dependence of the free energy change of denaturation on the concentration of alcohol or carboxylic acid,and were correlated well with the solvent-accessible surface area(ASA)of alcohol and carboxylic acid molecules.We have constructed a simple equation on the basis of these factors for explaining the effect of alcohols and carboxylic acids in back-extraction processes of proteins of RVMS.These results suggested that the back-extraction processes were controlled by the formation of reverse micelle clusters as well as the denaturation of proteins.