Unité Matériaux Et Transformations, UMR CNRS 8207, Université de Lille 1, 59655 Villeneuve d Ascq Cédex, France.
J Phys Chem B. 2010 May 20;114(19):6675-84. doi: 10.1021/jp1006022.
The thermal denaturation process of beta-lactoglobulin has been analyzed in the 20-100 degrees C temperature range by Raman spectroscopy experiments simultaneously performed in the region of amide modes (800-1800 cm(-1)) and in the low-frequency range (10-350 cm(-1)). The analysis of amide modes reveals a two-step thermal denaturation process in the investigated temperature range. The first step corresponds to the dissociation of dimers associated with an increase of flexibility of the tertiary structure. In the second step, large conformational changes are detected in the secondary structure and described as a loss of alpha-helix structures and a concomitant formation of beta-sheets. Raman investigations in the low-frequency range provide important information on the origin of the denaturation process through the analysis of the solvent dynamics and its coupling with that of the protein. The softening of the tetrahedral structure of water induces the dissociation of dimers and makes the tertiary structure softer, leading to the water penetration in the protein interior. The methodology based on Raman investigations of amide modes and in the low-frequency region was used to analyze the mechanism of beta-lactoglobulin thermostabilization by trehalose. The main effect of trehalose is determined to be related to its capabilities to distort the tetrahedral organization of water molecules.
通过同时在酰胺模式（800-1800cm(-1))和低频范围（10-350cm(-1))进行拉曼光谱实验，分析了β-乳球蛋白在 20-100°C 温度范围内的热变性过程。酰胺模式的分析揭示了在所研究的温度范围内存在两步热变性过程。第一步对应于与三级结构柔韧性增加相关的二聚体的解离。在第二步中，在二级结构中检测到较大的构象变化，并描述为α-螺旋结构的丧失和β-折叠结构的同时形成。低频范围内的拉曼研究通过分析溶剂动力学及其与蛋白质动力学的耦合，为变性过程的起源提供了重要信息。水的四面体结构的软化诱导二聚体的解离，并使三级结构变软，导致水渗透到蛋白质内部。基于酰胺模式和低频区的拉曼研究的方法被用于分析海藻糖对β-乳球蛋白热稳定性的机制。海藻糖的主要作用被确定与其扭曲水分子的四面体组织的能力有关。
