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Enthalpy relaxation of bovine serum albumin and implications for its storage in the glassy state
Author(s) -
Farahnaky Asgar,
Badii Fojan,
Farhat Imad A.,
Mitchell John R.,
Hill Sandra E.
Publication year - 2005
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.20265
Subject(s) - enthalpy , chemistry , differential scanning calorimetry , bovine serum albumin , endotherm , endothermic process , denaturation (fissile materials) , calorimetry , relaxation (psychology) , enthalpy of fusion , thermodynamics , analytical chemistry (journal) , chromatography , nuclear chemistry , psychology , social psychology , physics , adsorption
Two endothermic peaks could be observed for five commercial samples of bovine serum albumin (BSA). The smaller peak observed by differential scanning calorimetry (DSC) corresponded to enthalpy relaxation. This peak was followed on storage of BSA, in its glassy state, after it had been heated above its denaturation temperature. Enthalpy and peak temperature increased with duration of storage. On storage for one week at 60°C, a sample at 8.3% moisture showed a peak at 100°C with an energy value of approximately 2 J per g protein. BSA samples were heated within the DSC sufficiently to eliminate the lower enthalpy peak but without altering the denaturation enthotherm. The amount of physical aging shown by these BSA samples was similar to that of the heat‐denatured samples. It was concluded that the heating endotherms of dry BSA reflect both the storage and thermal history of the sample. Possible implications of the enthalpy relaxation of BSA on the behavior of this important protein are considered. © 2005 Wiley Periodicals, Inc. Biopolymers 78: 69–77, 2005