da Silva Marcelo A, Farhat Imad A, Arêas Elizabeth P G, Mitchell John R
Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, Caixa Postal 26077, CEP 05513-970 São Paulo, SP, Brazil.
Biopolymers. 2006 Dec 5;83(5):443-54. doi: 10.1002/bip.20561.
The gelation process of lysozyme in water/tetramethylurea in the presence of salt was investigated as a function of temperature and system composition by rheology, infrared spectroscopy, and microcalorimetry. Times and temperatures of gelation were determined from the variation of the storage (G') and loss (G'') moduli. It was found that gelation times follow exponential decays with both protein and tetramethylurea (TMU) concentrations and with temperature. The activation energy for the overall process shows a linear dependence on TMU mass fraction. A strongly increased beta-sheet content and reduced alpha-helix occur with the increase of TMU concentration in the binary solvent. Also, a linear decrease of lysozyme denaturation temperature and enthalpy on TMU concentration is found for the TMU mass fraction up to 0.5, above which no denaturation signal can be detected.
通过流变学、红外光谱和微量量热法，研究了在盐存在下，溶菌酶在水/四甲基脲中的凝胶化过程与温度和体系组成的关系。根据储能模量（G'）和损耗模量（G''）的变化确定凝胶化时间和温度。结果发现，凝胶化时间随蛋白质和四甲基脲（TMU）浓度以及温度呈指数衰减。整个过程的活化能与TMU质量分数呈线性关系。在二元溶剂中，随着TMU浓度的增加，β-折叠含量显著增加，α-螺旋含量减少。此外，对于TMU质量分数高达0.5的情况，发现溶菌酶变性温度和焓随TMU浓度呈线性下降，高于此质量分数则检测不到变性信号。
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