多光谱结合探究变性β-乳球蛋白与牛乳纤溶酶的结合特征

Exploring the binding characteristics of denatured β-lactoglobulin and plasmin in milk using multispectral analysis

中文关键词:  β-乳球蛋白  纤溶酶  超高温  交互作用

英文关键词:β-lactoglobulin  plasmin  ultra-high temperature  interaction

中文摘要:

      目的 基于超高温(ultra-high temperature, UHT)乳的加工过程, 探究不同变性程度β-乳球蛋白(β-lactoglobulin, β-Lg)与纤溶酶的互作及形成复合体的理化性质。方法 β-Lg经过预热和UHT处理后, 利用小角X射线散射明确了不同变性程度的β-Lg与纤溶酶的结合状态, 通过动态光散射表征了聚集体的粒径。采用傅里叶红外光谱、圆二色谱、内源荧光和紫外光谱分析了β-Lg与纤溶酶的结合基团, 以及聚集体的结构性质; 原子力显微镜结合透射电镜揭示聚集体的形貌特征。结果 β-Lg能与纤溶酶结合形成二聚体, 该聚集体粒径为20~220 nm。热变性导致β-Lg二级结构无序化, 三级结构展开, 进而增强了其与纤溶酶之间的氢键作用, 最终形成了球状或不规则形貌的聚集体。结论 β-Lg与纤溶酶通过非共价作用形成复合体, 且变性促进了β-Lg与纤溶酶的结合。该研究为优化低纤溶酶活力UHT乳的加工参数提供了新观点, 对延长UHT乳货架期和开发新型纤溶酶抑制剂提供了理论依据。

英文摘要:

      Objective To explore the interaction between β-lactoglobulin (β-Lg) and plasmin in different degrees of denaturation and the physical and chemical properties of complex formation based on the processing of ultra-high temperature (UHT) milk. Methods After β-Lg was preheated and treated with UHT, small-angle X-ray scattering clarified the binding state between β-Lg with different degrees of denaturation and plasmin, and dynamic light scattering characterized the particle size of the aggregates. Furthermore, Fourier-transform infrared spectroscopy, circular dichroism, intrinsic fluorescence, and ultraviolet spectroscopy analyzed the binding groups between β-Lg and plasmin, as well as the structural properties of the aggregates. Atomic force microscopy combined with transmission electron microscopy revealed the morphology of the aggregates. Results β-Lg could bind with plasmin to form dimers, with aggregate sizes ranging from 20 nm to 220 nm. Thermal denaturation caused the disordering of the secondary structure of β-Lg structure and the unfolding of its tertiary structure, thereby enhancing hydrogen bonding interactions with plasmin and ultimately forming spherical or irregularly shaped aggregates. Conclusion β-Lg and plasmin form complexes through non-covalent interactions, and denaturation promotes the binding of β-Lg with plasmin. This study provides new insights into optimizing processing parameters for UHT milk with low plasmin activity, and offers a theoretical basis for extending the shelf life of UHT milk and developing new plasmin inhibitors.