PROTEIN STABILITY IN THE AMORPHOUS CARBOHYDRATE MATRIX - RELEVANCE TOANHYDROBIOSIS

The formation of intracellular glass is proposed to be relevant to pro tein stabilization and survival of anhydrobiotic organisms in the dry state. The stability of proteins in the amorphous carbohydrate matrix and its relevance to seed survival have been investigated in the prese nt study. Glucose-6-phosphate dehydrogenase (G6PDH) was preserved in t he amorphous glucose/sucrose (1:10, w/w) matrix by freeze-drying. The stability of freeze-dried G6PDH was examined at temperatures above and below the glass transition temperature (T-g). The rate of G6PDH inact ivation in the amorphous carbohydrate matrix deviated significantly fr om the Arrhenius kinetics, and conformed to the Williams-Landel-Ferry (WLF) relationship. The temperature dependence of G6PDH inactivation i n two sets of samples with different T-g values was compared. Identica l temperature dependence of G6PDH inactivation was observed after temp erature normalization by (T-T-g). Seed survival of Vigna radiata Wilcz ek (mung bean) showed a similar WLF kinetics at storage temperatures T greater than or equal to T-g. In situ protein stability in mung bean embryonic axes was studied using differential scanning calorimetry (DS C), Thermal stability of seed proteins exhibited a strong dependence o n the T-g of intracellular glass. These results indicate an important role of the glassy state in protein stabilization. Our data suggest an association between protein stability in intracellular glass and seed survival during storage. (C) 1998 Elsevier Science B.V. All rights re served.