Role of Sugar Glasses in Anyhydrobiosis
In general, when biological cells are dehydrated the structure and function of cell membranes become disrupted and the carbohydrates, amino acids, and proteins necessary to sustain a cell leak out, and the cell dies. Certain organisms, however, are known to survive complete dehydration by going into a state of suspended animation. When these dehydrated organisms come in contact with water they rapidly swell and resume metabolic activity.
It is now understood that a key factor allowing these organisms to accomplish this feat is a synthesis of glassy disaccharide sugars such as α-α' trehalose to replace water while in the dehydrated state. The glassy sugars appear to inhibit two sources of damage during drying: fusion and lipid phase transitions. Many questions, however, about the specific interactions between the phospholipids and the disaccharide sugars remain unanswered. Our group is interested in employing solid-state NMR techniques for measuring nuclear spin dipolar coupings, chemical shift anisotropy, and quadrupolar couplings to (1) elucidate the structure and dynamics of sugars in the glassy state, (2) elucidate structure and dynamics in sugar/lipid mixtures, and (3) determine the specific interactions that may exist between phospholipids and glassy sugars, such as α-α' trehalose. Advances in the fundamental knowledge of the mechanism of anhydrobiosis should have an impact in such a diverse range of technologies such as seed storage, gene banks, and the preservation of dry foods and pharmaceutical products.
In one of our preliminary studies we have used solid state 13C NMR and ab initio quantum mechanical methods (Gaussian 94) in order to characterize the possible molecular conformations of trehalose. Using a simplified structure (2-(tetrahydropyran-2-yloxy) tetrahydropyran) as a model we have calculated the energy and 13C magnetic shielding parameters as a function of the two glycosidic torsion angles. Combining ab initio derived maps and using the 13C lineshape as constraints we were able to construct the torsion angle distribution map for α-α' trehalose. We believe measurements of 13C isotropic chemical shift and other solid-state NMR tensor parameter distributions in combination with ab initio methods can prove useful in identifying sources of structural disorder in glassy trehalose. By monitoring these structural distributions new information about the membrane surface associative properties of trehalose and other sugars should be accessible.
References and Related Resources from our Lab
Solid-State C-13 NMR Investigations of the Glycosidic Linkage in aα-α'-trehalose,,
P. Zhang and A. N. Klymachyov and S. Brown and J. G. Ellington and P. J. Grandinetti