H/D Isotope Effects in Protein Thermal Denaturation: The Case of Bovine Serum Albumin

Abstract : The present work investigates the effects of HID isotopic sub stitution on the structural and thermodynamic stability of bovine serum albumin (BSA) in aqueous solution over the temperature range of 5-90 degrees C. Using far-ultraviolet circular dichroism, we have compared protein unfolding pathways in H(2)O and D(2)O. Our results show that BSA possesses similar conformations in H(2)O and D(2)O at temperatures below 50 degrees C but follows different unfolding pathways at higher temperatures. The presence of D(2)O retards the occurrence of irreversible thermal denaturation in BSA, as evidenced by a higher onset temperature of 58 degrees C, in contrast to 50 degrees C in H(2)O center dot D(2)O exhibits a protective effect on the domain structure during the early stages of domain denaturation. Following incubation at 90 degrees C over a period of minutes, D(2)O causes a rapid aggregation of BSA molecules. This behavior is not observed in H(2)O solutions. Meanwhile, H/D substitution does not influence the reversible structural transformation of the protein in a significant manner. Partly renatured BSA in H(2)O and D(2)O undergoes very similar reversible structural transformations during a second heating cycle.
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Submitted on : Wednesday, August 17, 2011 - 11:53:21 AM
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Ling Fu, Sandrine Villette, Stéphane Petoud, Felix Fernandez-Alonso, Marie-Louise Saboungi. H/D Isotope Effects in Protein Thermal Denaturation: The Case of Bovine Serum Albumin. Journal of Physical Chemistry B, American Chemical Society, 2011, 115 (8), pp.1881-1888. ⟨10.1021/jp104769v⟩. ⟨hal-00614896⟩



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