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利用差示扫描量热(DSC)和温度调制差示扫描量热(MDSC)研究了鸡蛋白溶菌酶在纯水及二甲基亚砜(DMSO)/水混合溶剂中的热变性过程,探讨了酶的浓度、扫描速率和共溶剂的含量对热变性行为的影响规律.在纯水溶液中,溶菌酶的变性焓(“Hm)随酶浓度的增大而增大.而在DMSO/水混合溶剂中,变性温度(Tm)随DMSO体积分数的增大向低温方向移动,变性峰变低变宽;当DMSO体积分数达到70%后,热变性曲线变成了一条光滑的直线.另外,在纯水溶液中溶菌酶的MDSC图除了出现DSC中可观察到的主吸热峰(I)外,在峰(I)的前面还出现一个小而对称的吸热峰(II),并且当体系中有DMSO存在时也未能观察到此峰.当溶菌酶浓度增大时,Tm(II)移向低温,”Hm(II)减小,Tm(I)与Tm(II)之间的距离变长.吸热峰(II)的出现被认为是由于水溶液中溶菌酶二聚体的可逆离解造成的.
The heat denaturation of hen egg white lysozyme in pure water and dimethylsulfoxide (DMSO) / water mixed solvent was studied by differential scanning calorimetry (DSC) and temperature-modulated differential scanning calorimetry (MDSC) Enzyme concentration, scan rate and co-solvent content on the heat-denatured behavior were investigated.The denaturation enthalpy (“Hm”) of lysozyme increased with the increase of enzyme concentration in pure water solution, while in DMSO / water mixture In the solvent, the denaturation temperature (Tm) shifts to the low temperature with the increase of the volume fraction of DMSO, and the denaturation peak broadens and width decreases. When the volume fraction of DMSO reaches 70%, the thermal denaturation curve becomes a smooth straight line. In addition, In addition to the main endothermic peak (I) observed in DSC, a small but symmetrical endothermic peak (II) appears in front of peak (I), and when the MDSC pattern of lysozyme in pure water solution appears in the system This peak was also not observed in the presence of DMSO. As lysozyme concentration increased, Tm (II) shifted to lower temperatures, "Hm (II) decreased and the distance between Tm (I) and Tm The appearance of endothermic peak (II) is believed to be due to the reversible dissociation of lysozyme dimer in aqueous solution.