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Frontiers of Chemistry in China

ISSN 1673-3495

ISSN 1673-3614(Online)

CN 11-5726/O6

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Front Chem Chin    2009, Vol. 4 Issue (1) : 32-38    https://doi.org/10.1007/s11458-009-0009-8
RESEARCH ARTICLE
Denaturation study of bovine serum albumin induced by guanidine chloride or urea by microcalorimetry
Xiangrong LI1,2(), Wei GUO1, Yan LU2
1. Department of Chemistry, School of Basic Medicine, Xinxiang Medical College, Xinxiang 453003, China; 2. College of Chemistry and Environmental Science, Henan Normal University, Xinxiang 453007, China
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Abstract

The denaturation of bovine serum albumin (BSA) induced by guanidine chloride or urea at different pH values was studied by isothermal microcalorimetry measurements at 30°C. The simple bonding model, which was developed by Privalov, was employed to obtain the apparent bonding constant K, the apparent singular bonding Gibbs bonding energy ΔG and the total Gibbs energy ΔG(a) between the protein and denaturant, from analysis of the calorimetric data. Furthermore, linear extrapolation at the midpoint of transition was employed to determine the apparent denaturation enthalpy ΔHd. The results showed that for guanidine chloride, the bonding between BSA and guanidine chloride could proceed more easily in an alkaline condition, and the apparent denaturation enthalpy ΔHd of BSA due to guanidine chloride was 350 kJ·mol–1 at pH 6.97 and 7.05, while it was 275 kJ·mol–1 at pH 9.30, which indicated that BSA was more stabilized in a neutral condition. However, for urea, the bonding between BSA and urea could proceed more easily in an acidic condition, and the apparent denaturation enthalpy ΔHd of BSA due to urea was 295 kJ·mol–1 at pH 6.97, while it was 230 kJ·mol–1 at pH 7.05 and 9.30. The results indicate that the degree of expansion of BSA in the two denaturants is different.
Keywords bovine serum albumin      isothermal microcalorimetry      guanidine chloride      urea      denaturation     
Corresponding Author(s): LI Xiangrong,Email:lixiangrong79@sohu.com   
Issue Date: 05 March 2009
 Cite this article:   
Xiangrong LI,Wei GUO,Yan LU. Denaturation study of bovine serum albumin induced by guanidine chloride or urea by microcalorimetry[J]. Front Chem Chin, 2009, 4(1): 32-38.
 URL:  
https://academic.hep.com.cn/fcc/EN/10.1007/s11458-009-0009-8
https://academic.hep.com.cn/fcc/EN/Y2009/V4/I1/32
a/(mol·L–1)0.51.01.52.02.53.03.54.04.55.05.56.0
Q(a) (pH=4.80)–91–140–182–226–238–241–267–409–503–543–630–698
Q(a) (pH=7.05)–89–150–199–229–230–233–271–419–478–538–646–670
Q(a) (pH=9.30)–90–150–200–217–232–241–351–401–436–522–601–657
Tab.1  The thermal effect of bonding () (kJ·mol) between BSA and guanidine chloride
a/(mol·L–1)1.02.03.04.05.06.07.08.0
Q(a) (pH=4.80)–230–357–389–401–431–433–609–739
Q(a) (pH=7.05)–78–155–198–248–261–271–352–444
Q(a) (pH=9.30)–81–144–207–258–264–273–320–401
Tab.2  The thermal effect of bonding () (kJ·mol) between BSA and urea
nΔH/(kJ·mol–1)KΔG/(kJ·mol–1)
Guanidine chloride pH=4.80, BSA pH=6.97–3990.5731.40
Guanidine chloride pH=7.05, BSA pH=7.05–3960.5971.30
Guanidine chloride pH=9.30, BSA pH=9.30–3870.6261.18
Tab.3  The value of Δ, and Δ for the reaction of bonding between BSA and guanidine chloride
nΔH/(kJ·mol–1)KΔG/(kJ·mol–1)
Urea pH=4.80, BSA pH=6.97–5630.7200.83
Urea pH=7.05, BSA pH=7.05–6930.1335.09
Urea pH=9.30, BSA pH=9.30–7480.1225.31
Tab.4  The value of Δ, and Δ for the reaction of bonding between BSA and urea
Fig.1  Effect of guanidine chloride activity on –Δ() for the interaction of BSA and guanidine chloride
Fig.2  Effect of urea activity on –Δ() for the interaction of BSA and urea
Fig.3  Effect of guanidine chloride activity on –() for the interaction of BSA and guanidine chloride
Fig.4  Effect of urea activity on –() for the interaction of BSA and urea
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