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Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/jspui/handle/10054/9312

Title: 1,1,1,3,3,3-hexafluoroisopropanol induced thermal unfolding and molten globule state of bovine alpha-lactalbumin: Calorimetric and spectroscopic studies
Authors: KUNDU, A
KISHORE, N
Keywords: partially folded state
beta-sheet protein
guanidine-hydrochloride
prion protein
cytochrome-c
trifluoroethanol
lysozyme
denaturation
peptide
nmr
Issue Date: 2004
Publisher: JOHN WILEY & SONS INC
Citation: BIOPOLYMERS, 73(4), 405-420
Abstract: The thermal denaturation of a-lactalbumin was studied at pH 7.0 and 9.0 in aqueous 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) by high-sensitivity differential scanning calorimetry. The conformation of the protein was analyzed by a combination of fluorescence and circular dichroism measurements. The most obvious effect of HFIP was lowering of the transition temperature with an increase in the concentration of the alcohol up to 0.30M, beyond which no calorimetric transition was observed. Up to 0.30M HFIP the calorimetric and van't Hoff enthalpy remained the same, indicating the validity of the two-state approximation for the thermal unfolding of alpha-lactalbumin. The quantitative thermodynamic parameters accompanying the thermal transitions have been evaluated. Spectroscopic observations confirm that a-lactalbumin is in the molten globule state in the presence of 0.50M HFIP at pH 7.0 and 0.75M HFIP at pH 9.0. The results also demonstrate that alpha-lactalbumin in the molten globule state undergoes a noncooperative thermal transition to the denatured state. It is observed that two of four tryptophans are exposed to the solvent in the HFIP induced molten globule state of alpha-lactalbumin compared to four in the 8.5M urea induced denatured state of the protein. It is also observed that the HFIP induced molten globule states at the two pH values are difterent from the acid induced molten globule state (A state) of alpha-lactalbumin. (C) 2004 .
URI: http://dx.doi.org/10.1002/bip.20014
http://dspace.library.iitb.ac.in/xmlui/handle/10054/9312
http://hdl.handle.net/10054/9312
ISSN: 0006-3525
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