A comparative study of the direct calorimetric determination of the denaturation enthalpy for lysozyme in sodium dodecyl sulfate and dodecyltrimethylammonium bromide solutions
A comparative study of the direct calorimetric determination of the denaturation enthalpy for lysozyme in sodium dodecyl sulfate and dodecyltrimethylammonium bromide solutions
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DOI：
10.1007/s10953-008-9267-1
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发表时间：
2008-05-01
影响因子：
1.2
通讯作者：
Taleshi, E.
中科院分区：
文献类型：
--
作者：
Behbehani, G. Rezaei;Saboury, A. A.;Taleshi, E.
本文用等温滴定量热法研究了溶菌酶与阴离子表面活性剂十二烷基硫酸钠（SDS）和阳离子表面活性剂十二烷基三甲基溴化铵（DTAB）在pH = 7.0和27 ℃的磷酸盐缓冲溶液中形成的复合物。采用一种新的直接量热法跟踪蛋白质变性过程，研究表面活性剂对蛋白质稳定性的影响。用扩展溶剂化模型描述了溶菌酶与SDS在整个SDS浓度范围内的相互作用。从新方程恢复的溶剂化参数归因于溶菌酶的结构变化及其生物活性。在低SDS浓度下，结合主要是静电与一些同时与附近的疏水区域的溶菌酶的疏水性尾部的相互作用。这些最初的相互作用可能会导致一些蛋白质解折叠，并暴露出额外的疏水位点。SDS对溶菌酶的诱导变性焓为160.81 ± 0.02kJ·mol ~（-1）。溶菌酶-DTAB复合物的行为非常不同于溶菌酶-SDS复合物。SDS诱导溶菌酶去折叠的能力强于DTAB。DTAB变性溶菌酶的诱导焓为86.46 ± 0.02kJ·center-dot·mol ~（-1）。
The complexes of lysozyme with the anionic surfactant sodium dodecyl sulfate (SDS) and the cationic surfactant dodecyltrimethylammonium bromide (DTAB) have been investigated by isothermal titration calorimetry at pH = 7.0 and 27 degrees C in a phosphate buffer. A new direct calorimetric method was applied to follow the protein denaturation and study the effect of surfactants on the stability of proteins. The extended solvation model was used to represent the enthalpies of lysozyme + SDS interaction over the whole range of SDS concentrations. The solvation parameters recovered from the new equation are attributed to the structural change of lysozyme and its biological activity. At low SDS concentrations, the binding is mainly electrostatic with some simultaneous interaction of the hydrophobic tail with nearby hydrophobic regions of lysozyme. These initial interactions presumably cause some protein unfolding and expose additional hydrophobic sites. The induced enthalpy of denaturation of lysozyme by SDS is 160.81 +/- 0.02 kJ center dot mol(-1). The lysozyme-DTAB complexes behave very differently from those of the lysozyme-SDS complexes. SDS induces a stronger unfolding of lysozyme than DTAB. The induced enthalpy of lysozyme denaturation by DTAB is 86.46 +/- 0.02 kJ center dot mol(-1).