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Low-Temperature Glass Transitions of Quenched and Annealed Bovine Serum Albumin Aqueous Solutions

Kiyoshi Kawai ^*, Toru Suzuki  and Masaharu Oguni 

^* National Food Research Institute, Tsukuba 305-8642, Japan; Department of Food Science and Technology, Tokyo University of Marine Science and Technology, Tokyo 108-8477, Japan; and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, Tokyo 152-8551, Japan

Correspondence: Address reprint requests to Kiyoshi Kawai, E-mail: kiyoshik{at}affrc.go.jp.

To investigate the glass transition behaviors of a 20% (w/w) aqueous solution of bovine serum albumin, heat capacities and enthalpy relaxation rates were measured by adiabatic calorimetry at temperatures ranging from 80 to 300 K. One series of measurements was carried out after quenching from 300 down to 80 K and another after annealing in 200–240 K. The quenched sample showed a heat capacity jump indicating a glass transition temperature T_g = 170 K, and the annealed sample showed a smaller jump with the T_g shifted toward the higher temperature side. The temperature dependence of the enthalpy relaxation rates for the quenched sample indicated the presence of two enthalpy relaxation effects: one at around 110 K and the other over a wide temperature range (120–190 K). The annealed sample showed three separate relaxation effects giving 1) T_g = 110 K, 2) 135 K, and 3) temperature higher than 180 K, whereas nothing around 170 K. These effects were thought to originate, respectively, from the rearrangement motions of 1) primary hydrate water forming a direct hydrogen bond with the protein, 2) part of the internal water localized in the opening of a protein structure, and 3) the disordered region in the protein.

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				Y. A. Goddard, J.-P. Korb, and R. G. Bryant Structural and Dynamical Examination of the Low-Temperature Glass Transition in Serum Albumin Biophys. J., November 15, 2006; 91(10): 3841 - 3847. [Abstract] [Full Text] [PDF]