卵黏蛋白复合体凝胶特性在蛋清稀化过程中的动态转化规律与分子机制

Thinning of egg white is regarded as a sensitive indicator for egg quality deterioration. Ovomucin complex has been considered to be the key to maintaining the viscoelastic properties of egg white. However, there is lack in understanding of the dynamic changes of this important protein complex during egg white thinning, and the molecular mechanism of ovomucin complex transition is still not clear. To solve this issue, mass spectrometry combined with FI-IR、CD、DLS、biological electron microscopy, rheological technologies are applied to identify and characterize the composition and molecular properties of ovomucin complex. Transformation regularities of ovomucin complex composition and molecular properties during egg white thinning are further investigated. Statistical methods such as clustering and discriminant analysis as well as exponential regression model are implied to explore the relationship between ovomucin complex conformational changes and egg white quality. Key environmental parameters of egg white, significantly associated with ovomucin complex changes are then selected. Then, the effect of degree of polymerization, protein concentration, and pH, ionic strength of the protein complex on supramolecular conformation, intermolecular interactions and the rheological properties of ovomucin complex are studied. Exploration of the transformation kinetics of key proteins will be also involved; This project attempts to explain the possible molecular mechanisms of egg white thinning from the view of supramolecular conformational dynamics change of ovomucin complex, thus further to provide a theoretical basis for the clarification of the egg quality changes mechanism during storage.

蛋清稀化是蛋品质劣变的重要指标，卵黏蛋白复合体是维持蛋清天然凝胶特性的关键成分，而对这类重要的蛋白质复合体在蛋清稀化过程中的动态变化规律与机制却并不清楚。本课题以蛋清中的卵黏蛋白复合体为研究对象，应用质谱技术结合FI-IR、CD、DLS、生物电镜及流变学等技术手段对该复合体的组成、结构与超分子特性进行鉴定与表征，进而分析其构象与凝胶特性在蛋清稀化过程中的转变规律；应用聚类和判别分析及指数回归模型筛选与卵黏蛋白复合体变化显著相关的关键蛋清环境参数，进一步研究分子大小、蛋白浓度以及pH、离子强度等关键因素对该蛋白质复合体组成、超分子构象、分子间相互作用与凝胶特性的影响，分析复合体中关键蛋白的转化动力学，以探讨卵黏蛋白复合体的凝胶特性在蛋清稀化过程中转变的分子机制，最终从卵黏蛋白复合体超分子构象动态变化的角度揭示蛋清稀化的生化机制，为蛋品质变化机理的深入研究和鲜蛋的贮运保鲜提供理论。

蛋清稀化是蛋品质劣变的重要指标，卵黏蛋白复合体是维持蛋清天然凝胶特性的关键成分，而对这类重要的蛋白质复合体在蛋清稀化过程中的动态变化规律与机制却并不清楚。本项目在分析鉴定了蛋清黏蛋白复合体的结构和组成的基础上，研究了蛋清稀化过程中鲜蛋品质和卵黏蛋白复合体含量的变化规律及其相关关系，证实卵黏蛋白含量与蛋清粘弹性之间存在显著相关性，在此基础上建立黏蛋白含量为指标的壳蛋新鲜度的评价模型；研究了蛋清稀化过程中卵黏蛋白理化性质（如溶解度、疏水性、粒度）、亚基组成、光谱特性（荧光、IR、CD）和二级结构的变化规律，分析了其与蛋清品质（HU）之间的关系，阐述了蛋清稀化的可能机制：即贮藏期间由于蛋清pH的升高，导致黏蛋白亚基解离、糖链降解同时二级结构中无规则卷曲增加，折叠结构降低，导致分子粒度减小，聚合度降低，溶解性增加，黏度降低，凝胶结构破坏，最终导致蛋清黏弹性的降低，从而出现稀化现象。