(4be) Molecular Motions of the Beta Relaxation and Glassy Biomolecular Preservation

It has long been known that sugar glasses can stabilize a variety of macromolecules. This effect has been observed in the natural protection of lipid bilayers against freezing and drying, and it is employed artificially in the preservation of otherwise unstable dehydrated protein drugs. Recent experimental results employing antiplasticizer additives have suggested that it is the fast dynamics, rather than structural relaxation, of an encapsulating sugar glass that is most coupled to biomolecular preservation. This conclusion could have important implications in the leveraging of this preservation phenomenon, and it exemplifies a broader need to better understand the molecular origins of fast relaxation processes in glasses and supercooled liquids.

A central issue both in understanding the fast dynamics of glasses and in clarifying the coupling of these processes to biomolecule preservation is the nature of the fast beta relaxation. Although the behavior of this relaxation has been proposed to relate to dynamic heterogeneities characteristic of glass forming liquids, the exact nature of the molecular motions corresponding to this relaxation are not known. Such short-time dynamics have been characterized by the Debye-Waller factor ? a measure of caging size ? and yet the exact physical relationships of this quantity to molecular dynamics and beta relaxation are likewise unknown. Accordingly, results are presented of coarse-grained molecular dynamics simulations representative of the two biological systems mentioned above? a bulk glass-former and a multicomponent lipid membrane ? in order to elucidate the connections between fast dynamics, the beta relaxation, dynamics heterogeneites, and biomolecular preservation by biological glasses.

Funding for this research has been provided by NIH Grant # R01 EB006398-01.