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Elucidating the binding thermodynamics of 8-anilino-1-naphthalene sulfonic acid with the A-state of alpha-lactalbumin: An isothermal titration calorimetric investigation

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Title Elucidating the binding thermodynamics of 8-anilino-1-naphthalene sulfonic acid with the A-state of alpha-lactalbumin: An isothermal titration calorimetric investigation
 
Creator SINGH, SK
KISHORE, N
 
Subject molten globule state
enthalpy-entropy compensation
intramolecular interactions
guanidine-hydrochloride
protein
fluorescence
water
intermediate
recognition
transition
alpha-lactalbumin
a-state
molten globule
isothermal titration calorimetry
8-anilino-1-naphthalene
sulfonic acid
ligand binding
 
Description Isothermal titration calorimetry has been used to demonstrate that the heat profile associated with the binding of 8-anilino-1-naphthalene sulfonic acid (ANS) with the acid induced molten globule state (A-state) of alpha-lactalbumin (alpha-LA) is different from that with the native and denatured states of the protein. The results corroborate the spectroscopic observations that ANS binds more strongly to the partially folded states of the protein compared to that with the native and denatured states. ANS binds to the A-state of a-LA at two independent binding sites that remain nearly the same in the temperature range of 10-35 degrees C. The number of moles of ANS binding at site 1 at 10 degrees C is 14.0 +/- 0.2 and remains nearly the same with rise in temperature. However, the number of moles of ANS molecules binding at site 2 show an increase from 1.6 +/- 0.2 at 10 degrees C to 4.1 +/- 0.1 at 35 degrees C. The deviation of the slope of enthalpy-entropy compensation plot from unity and nonadherence to van't Hoff dictates implies that the binding sites on the A-state of alpha-LA for ANS are not well defined and specific; rather, these binding sites are formed due to greater exposure of hydrophobic clusters in the A-state of the protein. The results for the first time demonstrate the use of isothermal titration calorinzetry in characterizing the A-state of alpha-LA both qualitatively and quantitatively. (c) 2006 .
 
Publisher JOHN WILEY & SONS INC
 
Date 2011-08-16T04:53:27Z
2011-12-26T12:54:45Z
2011-12-27T05:43:01Z
2011-08-16T04:53:27Z
2011-12-26T12:54:45Z
2011-12-27T05:43:01Z
2006
 
Type Article
 
Identifier BIOPOLYMERS, 83(3), 205-212
0006-3525
http://dx.doi.org/10.1002/bip.20547
http://dspace.library.iitb.ac.in/xmlui/handle/10054/9390
http://hdl.handle.net/10054/9390
 
Language en