College Park, Maryland      June 6 - 10 , 2004

T2-A3 (2:15 PM): The role of "anchoring" molecules and residual water on the stability of biomolecules

A. M. Pivovar, S. Takata, J.E. Curtis (NIST Center for Neutron Research)

In order to slow the deactivation of a biologically active material, biomaterials are commonly stored within glass networks formed by small molecules with extensive hydrogen bonding interactions (e.g., saccharides or polyols). The glass network is believed to reduce the rate of deactivation by suppressing the dynamic mobility of biomolecular residues through thermodynamically favorable interactions between the glass and the surface of the native biomolecule. The “rigidity” imparted on the biomolecule by the glass matrix is dependent upon both the inherent rigidity of the glass and the strength of the interactions “anchoring” the biomolecule to the glass. To ascertain the role of the anchoring interactions on biopreservation, we have measured the ensemble temperature dependent mean square displacement dynamics of lysozyme-glucose composites using the High Flux Backscattering Spectrometer at the NIST Center for Neutron Research. Selective isotopic substitution of deuterium for hydrogen permits exclusive measurement of the dynamics of the biomolecular component in the mixture and evaluation of the total scattering from a fully hydrogenated sample allows us to ascertain the dynamics of the sugar. As expected, our results indicate that the dynamics of the biomolecule are suppressed through interactions with the anchoring sugar when compared with a pure lysozyme powder. However, the results also indicate that the dynamics of the anchored glucose molecules is less than what is observed in a pure glucose glass. We believe these results imply a strong dependence between the residual water present in the mixtures and biostability enhancement. The details of this conclusion and its ramifications on biopreservation formula design will be discussed.

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