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沙冬青抗冻蛋白热滞活性的DSC研究 总被引:3,自引:0,他引:3
在某些极地鱼类的血清以及某些昆虫和植物中 ,人们发现了一类特殊的物质 .它们的共同特点是能通过直接与冰晶核相互作用,抑制冰晶核的形成和生长,从而降低溶液冰点 .现已发现的这类抗冻物质都属于蛋白质,被统称为抗冻蛋白( Antifreeze Proteins, AFPs) .抗冻蛋白能以非依数性形式大大降低溶液的冰点,但对熔点的影响很微弱,而且遵从依数性的原则,使冰点低于平衡态的熔点,溶液处于反常的非平衡相变状态 .这种冰点低于熔点的特性称为热滞 (Hysteresis).因此,抗冻蛋白也叫热滞蛋白或温度迟滞蛋白( Thermal Hysteresis Proteins, … 相似文献
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抗冻蛋白能使生物体在寒冷环境下生存,具有极大的潜在应用价值。近年来,人们对抗冻蛋白开展了广泛的研究,但其抗冻机理还未明确。本文阐述了抗冻蛋白的功能特性和结构特征,并从结构的角度对其抗冻机制方面的分子模拟研究成果进行了综述。另一方面,对目前已知晶体结构的29个野生型抗冻蛋白的结构特性进行了分析,发现在整个抗冻蛋白表面和在冰结合位点处都存在亲水残基与水形成氢键和疏水残基与类冰结构特异性结合的特点。然后,探讨了抗冻蛋白的二级结构、冰结合位点残基的疏水性与抗冻活性之间的关系。最后,从结构的角度讨论了抗冻蛋白的机制和影响抗冻活性的因素并简要总结了仿生抗冻材料设计和应用的研究进展。 相似文献
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云杉蚜虫(Choristoneura fumiferana)体内可产生一种抗冻蛋白(AFP), 能够保护其在寒冷的冬季安全越冬, 这类昆虫抗冻蛋白(简称 CfAFP)存在多种异构体, 其中CfAFP-501和CfAFP-337均呈现相似的左手β-螺旋结构. 实验测定, 相比CfAFP-337仅多出两个插入螺旋环的CfAFP-501的抗冻活性竟然是CfAFP-337的3倍左右. 蛋白异构体CfAFP-501显著增强的抗冻活性和它的插入环数不成比例, 当然也不能简单归因于两个插入环所导致的与冰晶作用部位及接触面积的增加. 为了探讨两种昆虫抗冻蛋白异构体抗冻活性差异的分子基础, 深入了解抗冻蛋白作用特点的普遍规律, 分别使用分子力学、分子动力学模拟和量子力学方法来系统研究蛋白及其切割体与冰晶结合的结构特征及相互作用. 结果表明, CfAFP-501中多数螺旋环比CfAFP-337具有更强的冰晶相互作用和破坏冰晶中水分子的成键的能力, 由于螺旋长度增加导致CfAFP-501中各b-螺旋环之间协同效应的增强, 是其具有显著增强的抗冻活性的主要来源. 这种协同作用对具有b-螺旋结构的抗冻蛋白起十分关键的作用和重要贡献. 相似文献
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设计系列昆虫抗冻蛋白CfAFP突变体, 通过分子动力学模拟确定各突变体与冰晶的最佳作用模式, 并用半经验分子轨道方法AM1和PM3研究了其与冰晶的相互作用. 结果表明, TXT面上的苏氨酸在蛋白与冰晶相互识别和结合过程中十分关键, 对CfAFP与冰晶间相互作用的贡献大, 用其它疏水或亲水氨基酸残基替换都将削弱抗冻蛋白与冰晶的相互作用强度, 从而降低蛋白的抗冻活性. 但是, 在维系蛋白和冰晶结构匹配的基础上, 疏水基团的增加加强了抗冻蛋白与冰晶的结合, 从而增加蛋白的抗冻活性. 相似文献
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调制式DSC在高聚物研究中的应用 总被引:4,自引:0,他引:4
综述了一种新的热分析技术--调制式差示扫描量热示(Modulated Differentail Scanning Calorimetry)。对其工作原理,优点及在高聚物研究中的应用作了简介。 相似文献
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本文采用差示扫描量热法(DSC),研究了水合醛缩酶在含水量h从0.08g/g至2.28g/g范围内的热变性行为。实验结果表明,当h=0.08g/g时,水合醛缩酶样品的温度扫描热谱图呈现了两个吸热峰,其中低温峰很小,高温峰很大。随着h的增大,低温峰变得更小,高温峰则出现了分峰现象。当h=0.22g/g时,低温峰消失,高温峰则分裂成了两个独立的吸热峰。随着h的继续增大,其中前峰的位置不断移向低温,直至h_0.65g/g时,才不再变化。后峰的位置则始终保持不变。当再进行第二次温度扫描时,前峰消失,而后峰却能再现。本文给出了两峰在不同含水量时的转变温度、转变焓和转变焓之和,以及它们与含水量的关系。最后,对上述诸峰的起因作了分析讨论,认为低温峰可能起因于水合醛缩酶结晶的熔化作用,前峰和后峰可能起因于醛缩酶中两种A亚基的热变性。 相似文献
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冬小麦麸皮抗冻蛋白(TaAFP)的一级结构是研究其高级结构和功能的基础.本研究结合N-末端测序技术和肽指纹图谱技术,测定TaAFP的一级结构,并对其同源性进行分析.MALDI-TOF-MS质谱分析显示TaAFP的分子量为13637.711 Da.使用Trypsin(胰蛋白酶)、Hydroxylamine(羟胺)和Chymotrypsin(胰凝乳蛋白酶)分别对TaAFP酶解,并对各个酶解片段的肽指纹图谱进行解析和连接,最终确定TaAFP的一级结构为MARKVIALAFLLLLTISLSKSNAARVKYNGGESGGGGGGGGGGGGGGNGSG-SGSGYGYNYGKGGGQSGGGQGGGGGGGGGGGSNGSGSGSGYGYGYGQGNGGAQGQGSGGGGGGGGGGGGGGSGQGSGSGYGYGYGKGGGGGGGGGGDGGGGGGGGSAYVGRHE,测定覆盖度达到了100%.序列比对分析以及同源性分析结果显示,TaAFP是一种与植物细胞壁和抵抗寒冷相关的蛋白质. 相似文献
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差示扫描量热技术(DSC)的发展已有半个世纪的历史.热流型DSC基于Boersma原理(1955年):仪器的热阻与样品无关,因此热流可以定量测定.功率补偿型DSC基于Watson和O'Neill在1963年提出的原理,测量输入到样品和参比之间的功率差. 相似文献
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Differential Scanning Calorimetric and Circular Dichroistic Studies on Plant Antifreeze Proteins 总被引:3,自引:0,他引:3
Lu M. Wang B. Li Zh. Fei Y. Wei L. Gao Sh. 《Journal of Thermal Analysis and Calorimetry》2002,67(3):689-698
Antifreeze protein (AFP) can lower the freezing point by inhibiting the growth of ice crystals. In this article, the thermal
hysteresis activity (THA) of a plant AFP was measured with differential scanning calorimetry (DSC). As is shown, when the
amount of ice in the sample was less than 5% THA of this AFP reached as high as 0.35°C. The secondary structure of this AFP
was studied with circular dichroism (CD). The CD spectrum from 195to 240 nm indicated a well-defined secondary structure consisting
11% α-helix, 34%antiparallel β-sheet and 55% random coil.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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New approaches to the analysis of differential scanning calorimetry (DSC) data relating to proteins undergoing irreversible
thermal denaturation have been demonstrated. The experimental approaches include obtaining a set of DSC curves at various
scanning rates and protein concentrations, and also reheating experiments. The mathematical methods of analysis include construction
of a linear anamorphosis and simultaneous fitting of a theoretical expression for the dependence of the excess heat capacity
on temperature to a set of experimental DSC curves. Different kinetic models are discussed: the one-step irreversible model,
the model including two consecutive irreversible steps, the Lumry and Eyring model with a fast equilibrating first step, and
the whole kinetic Lumry and Eyring model.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Dr. Hiroshi Ohno Dr. Robin Susilo Raimond Gordienko Dr. John Ripmeester Dr. Virginia K. Walker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(34):10409-10417
Recombinant antifreeze proteins (AFPs), representing a range of activities with respect to ice growth inhibition, were investigated for their abilities to control the crystal formation and growth of hydrocarbon hydrates. Three different AFPs were compared with two synthetic commercial inhibitors, poly‐N‐vinylpyrrolidone (PVP) and HIW85281, by using multiple approaches, which included gas uptake, differential scanning calorimetry (DSC) temperature ramping, and DSC isothermal observations. A new method to assess the induction period before heterogeneous nucleation and subsequent hydrate crystal growth was developed and involved the dispersal of water in the pore space of silica gel beads. Although hydrate nucleation is a complex phenomenon, we have shown that it can now be carefully quantified. The presence of AFPs delayed crystallization events and showed hydrate growth inhibition that was superior to that of one of the benchmark commercial inhibitors, PVP. Nucleation and growth inhibition were shown to be independent processes, which indicates a difference in the mechanisms required for these two inhibitory actions. In addition, there was no apparent correlation between the assayed activities of the three AFPs toward hexagonal ice and the cubic structure II (sII) hydrate, which suggests that there are distinctive differences in the protein interactions with the two crystal surfaces. 相似文献
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Jianjun Zhang 《物理化学学报》2020,36(6):1907048-0
正采用描述物质热传导能力的参数为热导率。热导率直接影响材料加工过程的工艺调节和产品器件质量。近年来,导热材料在电子芯片、新能源汽车、网络通信和人工智能等方面有越来越重要的应用,快速准确地表征材料的热导率是一项很重要的工作。 相似文献
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DSC studies of cracker mixtures of different compositions of potassium nitrate, sulphur and aluminum have shown some critical characteristics either with the increase or decrease in the composition of the components. Specifically, sulphur composition below 8% showed no exothermic activity. The studies revealed that a minimum of 11% to a maximum of 17% of sulphur is required for good cracking characteristics. The kinetics of decomposition of cracker mixture is carried out employing DSC multiple heating rate kinetic method. Increase in sulphur content decrease the energy of activation facilitating easy ignition of the cracker mixtures. Arrhenius parameters for cracker mixture decomposition are reported in this paper. 相似文献
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