Thermodynamics Research Today is a free monthly online journal that collates and summarizes the latest research about Thermodynamics, including details on enthalpy, entropy, energy transitions. | ||||||||
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Pressure effects on the heat-induced aggregation of equine serum albumin by FT-IR spectroscopic study: Secondary structure, kinetic and thermodynamic properties.Okuno A, Kato M, Taniguchi Y Department of Applied Chemistry, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan. Pressure can restrain the heat-induced aggregation and dissociate the heat-induced aggregates. We investigated the aggregation-preventing pressure effect and the aggregates-dissociating pressure effect to characterize the heat-induced aggregation of equine serum albumin (ESA) by Fourier transform infrared spectroscopy. The results suggest that the alpha-helical structure collapses at the beginning of heat-induced aggregation, then the rearrangement of structure from partially unfolded structure to the intermolecular beta-sheet takes place through the activated state. We determined the activation volume for the heat-induced aggregation (DeltaV( not equal)=+92+/-8 ml mol(-1)) and the partial molar volume difference between native state and heat-induced aggregates (DeltaV(N-->HA)=+32 ml mol(-1)). This positive partial molar volume difference suggests that the heat-induced aggregates have larger internal voids than the native structure. Moreover, the positive volume change implies that the formation of the intermolecular beta-sheet is unfavorable under high pressure. We also determined the free energy profile of ESA. This energy profile explains the restriction of the formation of heat-induced aggregates by pressure. These results explain the structural differences between heat-induced aggregates with intermolecular beta-sheet and pressure-induced aggregates without intermolecular beta-sheet. Published 7 May 2007 in Biochim Biophys Acta, 1774(5): 652-60.
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