Effect of DMSO on Denaturation of Hen Egg-white Lysozyme in Aqueous Solution

FANG Ying-Ying, 温州大学化学与材料科学学院, 浙江 温州 325027; 山东大学胶体与界面化学教育部重点实验室, 济南 250100, College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325027, Zhejiang Province, P. R. China; Key Laboratory for Colloid and Interface Chemistry of the Ministry of Education, Shandong University, Jinan 250100, P. R. China, HU Xin-Gen, YU Li, LI Wen-Bing, ZHU Yu-Qing, YU Sheng
2007 Wuli huaxue xuebao  
摘要: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(驻H m )随酶浓度的增大而增大. 而在 DMSO/水混合溶剂中, 变性温度(T m )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, T m (II) 移向低温, 驻H m (II)减小, T m (I)与 T m (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. 关键词: DSC;MDSC; DMSO; 鸡蛋白溶菌酶; 热变性 中图分类号: O642 Abstract:
more » ... 42 Abstract: Astudyonthermaldenaturationofhenegg鄄whitelysozyme(HEWL)wascarriedoutbydifferential scanningcalorimetry(DSC)andmodulatedtemperaturedifferentialscanningcalorimetry(MDSC).Itwasfoundthat DSCprofilesofHEWLweredependentonheatingratesandconcentrationsofenzymeaswellascosolvent.Theenthalpy ofdenaturation(驻H m )increasedwithincreasingenzymeconcentrationinaqueoussolution.Inaqueoussolutioncontaining dimethylsolfoxide(DMSO),denaturationtemperature(T m )shiftedtowardlowertemperature,andthetransitionpeak becameshallowerandbroaderwithincreasingvolumeproportionofDMSO.WhenthecontentofDMSOwasmore than70 % ,onlyadecliningsmoothlinecouldbeobservedinsteadofasingleendothermictransitioncurve. Interestingly,fromMDSCcurvesofHEWLinaqueoussolutionwithoutDMSO,asmallandsymmetricalpeakinfront ofthemaintransition(I)wasobservedmarginally,whichwasregardedasapre鄄transition(II).Specially,thissmalland marginalpeakcouldnotbefoundinaqueoussolutioncontainingDMSO.Inaddition,withincreasingamountof protein, T m (II)shiftedtowardlowertemperature,and 驻H m (II)decreasedalongwiththetemperaturegapbetweentwo transitionslengthened.TheresultswereconsideredtobeduetothereversibledissociationofHEWLdimersinaqueous solution.
doi:10.3866/pku.whxb20070712 fatcat:bkzka4cu6reorp4h54xgos7z6e