THE SUPPOSED ROLE OF MICROBIOLOGICAL AEROSOL STABILIZERS AS SUBSTITUTES FOR BOUND WATER: AN IN VITRO MODEL SYSTEM

To test a current belief that inositol can take the place of water in maintaining the stability of desiccated cells, the effect of inositol on the reversible association-dissociation reaction of tobacco mosaic virus protein in 0.06 M phosphate buffer, pH 6.5, was studied by turbidimetric analysis. Addition of inositol lowered the temperature at which the association takes place. Enthalpy (H) increased from the control value of +196 kcal/mole to +260, +273, and +300 kcal/mole in the presence of 0.10, 0.15, and 0.20 M inositol, respectively, while entropy (S) increased from the control value of +600 cal/ (mole deg) to +870, +920, and +960 cal/(mole deg), respectively. In view of these results, it seems unlikely that inositol displaces bound water, for this would be expected to cause the equilibrium to shift in favor of the dissociated protein at a given temperature and thus to decrease H and S. A less direct effect seems likely, such as, for example, a conformation change brought about by binding of inositol at positions adjacent to the site of the association reaction.