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1,1,1,3,3,3-hexafluoroisopropanol induced thermal unfolding and molten globule state of bovine alpha-lactalbumin: Calorimetric and spectroscopic studies

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Title 1,1,1,3,3,3-hexafluoroisopropanol induced thermal unfolding and molten globule state of bovine alpha-lactalbumin: Calorimetric and spectroscopic studies
 
Creator KUNDU, A
KISHORE, N
 
Subject partially folded state
beta-sheet protein
guanidine-hydrochloride
prion protein
cytochrome-c
trifluoroethanol
lysozyme
denaturation
peptide
nmr
bovine alpha-lactalbumin 1,1,1,3,3,3-hexafluoroisopropanol
differential scanning calorimetry
circular dichroism
fluorescence
molten globule
 
Description 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 .
 
Publisher JOHN WILEY & SONS INC
 
Date 2011-08-04T09:21:38Z
2011-12-26T12:54:39Z
2011-12-27T05:42:47Z
2011-08-04T09:21:38Z
2011-12-26T12:54:39Z
2011-12-27T05:42:47Z
2004
 
Type Article
 
Identifier BIOPOLYMERS, 73(4), 405-420
0006-3525
http://dx.doi.org/10.1002/bip.20014
http://dspace.library.iitb.ac.in/xmlui/handle/10054/9312
http://hdl.handle.net/10054/9312
 
Language en