Vibrational Circular Dichroism Spectra of Lysozyme Solutions: Solvent Effects on Thermal Denaturation Processes
Vibrational Circular Dichroism Spectra of Lysozyme Solutions: Solvent Effects on Thermal Denaturation Processes
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DOI：
10.1021/jp311268x
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发表时间：
2013-03-07
影响因子：
3.3
通讯作者：
Nafie, Laurence
中科院分区：
文献类型：
--
作者：
Giugliarelli, Alessandra;Sassi, Paola;Nafie, Laurence
振动光谱法已被应用于溶菌酶热变性过程中构象变化的研究。本文用红外光谱和振动圆二色光谱（VCD）分析了溶菌酶在D_2O、D_2O/EtOD和D_2O/DMSO三种不同溶剂中的溶解行为。通过对溶于氘代水的溶菌酶的酰胺Ⅰ带的分析，揭示了对氨基的完全氘代效应。溶菌酶在D_2O中的红外吸收光谱与VCD光谱的比较表明，VCD技术对溶菌酶二级结构的部分或全部氘代具有较高的灵敏度。在不同的溶剂组成和pH值下，溶菌酶的热诱导聚集。有趣的是，IR和VCD显示出不同的灵敏度，以揭示热变性下的分子间β-折叠聚集。随着聚集体尺寸的增加，观察到VCD强度增强，而IR对该过程的成核步骤敏感。此外，通过对VCD符号图的分析，揭示了超分子物种的手性。这是第一次，我们展示了如何在不同的溶剂组合物下产生的聚集体，但VCD符号模式，因此相同的意义上的增长。相似的pH值显示出相同的VCD符号模式，因此显示出相同的生长感。
Vibrational spectroscopy has been applied to the study of conformational variation of lysozyme during thermal denaturation. An infrared and vibrational circular dichroism (VCD) analysis of lysozyme in D2O, D2O/EtOD, and D2O/DMSO at different solvent compositions and pH's was accomplished. Complete deuteration effects on amidic groups were revealed through the analysis of the amide I band of lysozytne dissolved in deuterated water. The comparison of IR absorption and VCD spectra of lysozyme in D2O revealed the higher sensitivity of the VCD technique to the presence of partially or fully deuterated secondary structure of lysozyme. Aggregation was induced by thermalization of lysozyme at different solvent compositions and pH values. Interestingly, IR and VCD showed different sensitivities to reveal intermolecular beta-sheet aggregation under thermal denaturation. The VCD intensity enhancement was observed as the aggregate dimension increased, whereas IR was sensitive to the nucleation step of the process. Moreover, chirality of supramolecular species was revealed through the analysis of the VCD sign pattern. For the first time, we demonstrate how aggregates produced under different solvent compositions but VCD sign pattern and consequently the same sense of growth. similar pH's showed the same VCD sign pattern and consequently the same sense of growth.