Thermodynamic and dynamic factors involved in the stability of native protein structure in amorphous solids in relation to levels of hydration

Thermodynamic and dynamic factors involved in the stability of native protein structure in amorphous solids in relation to levels of hydration
August 2005
John J. Hill 1, Evgenyi Y. Shalaev 2, George Zografi 3
1ICOS Corporation, 22021 20th Avenue SE, Bothell, Washington 98021
2Pfizer, Incorporated, MS 8156-004, Groton Laboratories, Global R&D, Eastern Point Road, Groton, Connecticut 06340
3School of Pharmacy, University of Wisconsin-Madison, 777 Highland Avenue, Madison, Wisconsin 53705-2222
Journal of Pharmaceutical Sciences, Volume 94, Issue 8 , Pages 1636 - 1667
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Keywords
amorphous ? glass transition ? solid state stability ? dynamical transition ? hydration ? dehydration ? sugars/lyoprotectants ? protein folding/refolding ? thermodynamics ? freeze drying/lyophilization ? spray drying ? protein formulation
Abstract
The internal, dynamical fluctuations of protein molecules exhibit many of the features typical of polymeric and bulk small molecule glass forming systems. The response of a protein's internal molecular mobility to temperature changes is similar to that of other amorphous systems, in that different types of motions freeze out at different temperatures, suggesting they exhibit the --modes of motion typical of polymeric glass formers. These modes of motion are attributed to the dynamic regimes that afford proteins the flexibility for function but that also develop into the large-scale collective motions that lead to unfolding. The protein dynamical transition, Td, which has the same meaning as the Tg value of other amorphous systems, is attributed to the temperature where protein activity is lost and the unfolding process is inhibited. This review describes how modulation of Td by hydration and lyoprotectants can determine the stability of protein molecules that have been processed as bulk, amorphous materials. It also examines the thermodynamic, dynamic, and molecular factors involved in stabilizing folded proteins, and the effects typical pharmaceutical processes can have on native protein structure in going from the solution state to the solid state.
? 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:1936-1967, 2005