Nonaqueous chemical modification of lyophilized proteins

Abstract

Publisher Summary The catalytic properties of a wide variety of enzymes remain intact in organic solvents. These findings imply that proteins may also retain their native structures when lyophilized and dispersed in organic solvents. Evidence has been obtained that crystallized proteins have essentially the same structure in water and organic solvent. In the lyophilized state, proteins are also in a nonaqueous environment and it is expected that their physicochemical properties will differ from that in solution, as the dynamic conformational equilibria that exits in solution will be absent. Some physicochemical studies indicate that the structure of the lyophilized state is very similar to that in solution, while others indicate that there is some limited but reversible conformational change. There are likely to be differences among proteins in this regard, however, the results of extensive studies with lyophilized enzymes in organic solvents provide strong evidence that most proteins in the lyophilized state retain the essential elements of their native structure. It is therefore expected that the reactivity of functional groups in lyophilized proteins can reflect their properties in solution and provide information on the solution structure. The present chapter reports that modification of lyophilized proteins in a nonaqueous environment has significant advantages over aqueous procedures. It shows that nonaqueous modification of lyophilized proteins in octane or in vacuo is feasible and practical. The increased temperature stability of proteins in the lyophilized state permits the use of elevated temperatures to accelerate the reactions. Modification in organic solvent has the advantage that volatile and nonvolatile reagents both can be used.