PROTEIN INACTIVATION IN AMORPHOUS SUCROSE AND TREHALOSE MATRICES - EFFECTS OF PHASE-SEPARATION AND CRYSTALLIZATION

Trehalose is the most effective carbohydrate in preserving the structu re and function of biological systems during dehydration and subsequen t storage. We have studied the kinetics of protein inactivation in amo rphous glucose/sucrose (1:10, w/w) and glucose/trehalose (1:10, w/w) s ystems, and examined the relationship between protein preservation, ph ase separation and crystallization during dry storage. The glucose/tre halose system preserved glucose-6-phosphate dehydrogenase better than did the glucose/sucrose system with the same glass transition temperat ure (T-g). The Williams-Landel-Ferry kinetic analysis indicated that t he superiority of the glucose/trehalose system over the glucose/sucros e system was possibly associated with a low free volume and a low free volume expansion at temperatures above the T-g. Phase separation and crystallization during storage were studied using differential scannin g calorimetry, and three separate domains were identified in stored sa mples (i.e., sugar crystals, glucose-rich and disaccharide-rich amorph ous domains). Phase separation and crystallization were significantly retarded in the glucose/trehalose system. Our data suggest that the su perior stability of the trehalose system is associated with several pr operties of the trehalose glass, including low free volume, restricted molecular mobility and the ability to resist phase separation and cry stallization during storage. (C) 1998 Elsevier Science B.V. All rights reserved.