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Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/jspui/handle/10054/3592

Title: Thermodynamics of the interactions of calcium chloride with alpha-chymotrypsin
Authors: KAR, K
ALEX, B
KISHORE, N
Keywords: differential scanning calorimetry
binding-site
magnetic-resonance
globular-proteins
surface-tension
stabilization
hydration
stability
trypsin
Issue Date: 2002
Publisher: ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD
Citation: JOURNAL OF CHEMICAL THERMODYNAMICS, 34(3), 319-336
Abstract: High sensitivity differential scanning calorimetry (d.s.c.) and uv-visible spectrophotometry have been used to study the thermal unfolding of alpha-chymotrypsin in presence of calcium chloride at pH = 2.8, 3.4, 5.0, 7.0, and 8.2. Quantitative thermodynamic parameters accompanying the thermal transitions have been evaluated. In the absence of calcium ions, the thermal denaturation of a-chymotrypsin is a reversible process giving a ratio of the van't Hoff to calorimetric enthalpy of 0.92 at pH = 2.8. At pH values higher than 5.0, the thermal denaturations in the absence of calcium chloride were observed to be completely irreversible. In the presence of calcium chloride, alpha-chymotrypsin undergoes irreversible thermal denaturation and its thermal transitions are found to be scan-rate dependent fitting to the model N-2 --> I, yielding an average activation energy of (419 +/- 16) kJ (.) mol(-1) using different approaches at pH = 2.8. It is also observed that at pH 2.8 and 3.4, calcium reduces the transition temperature of the protein. However, at pH 5.0, 7.0, and 8.2, it stabilizes initially, and at higher concentrations the salt acts as a destabilizer of the native structure of alpha-chymotrypsin. The surface tension values of aqueous calcium chloride solutions were measured and it is observed that the role of surface tension of the medium is not dominant in providing thermal stability of this protein. (C) 2002 .
URI: http://dx.doi.org/10.1006/jcht.2001.0855
http://dspace.library.iitb.ac.in/xmlui/handle/10054/3592
http://hdl.handle.net/10054/3592
ISSN: 0021-9614
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