乳源抗菌肽是一种新型的天然抗菌物质，能够抑制多种食品腐败菌的生长，在食品保藏中有广阔的应用前景。在前期研究中，本课题组首次从生牛乳中检测到一种新型抗菌肽Casein31（C31），对枯草芽孢杆菌有很强的抑制作用（最小抑菌浓度为1.8-4μM），能引起细胞膜结构损伤，进而导致细胞死亡，但损伤的机制尚未明确。本项目拟利用圆二色谱，荧光探针技术，超微技术和X-射线衍射技术研究C31对细胞膜的损伤机制：分析在枯草芽孢杆菌细胞表面的疏水环境诱导下，C31二级结构和两亲性的变化；明确细胞壁及其组分在C31入侵细胞过程中的作用；基于原生质体从动力学角度分析C31引起细胞膜结构损伤的过程，包括C31与细胞膜相互作用，细胞膜变薄，孔洞的形成和扩大的动态过程及位置分析，阐明C31损伤细胞膜的作用机制。本项目的研究将为抗菌肽的设计开发奠定理论基础，且为C31在食品保藏中的应用提供科学依据。

Milk-derived antimicrobial peptides can inhibit the growth of various spoilage bacteria and thus are used as natural antimicrobials for food preservation. In the previous study, a novel antimicrobial peptide Casein31 was identified in raw milk with minimum inhibitory concentration against Bacillus Subtilis between 1.8 and 4μM. In the mechanism study, Casein31 can form pores on the bacterial membrane, leading to the membrane disruption and cell death. But how Casein31 forms pores and disrupts bacterial membrane are still unknown. In this project, circular dichroism, fluorescent probe technique, ultramicro-technique and X-ray diffraction technique will be applied to study the mechanism of Casein31 action on bacterial membrane: Firstly, the transition of secondary structure of casein31 during the insertion into bacterial membrane will be analyzed; Secondly, the interaction of Casein31 with main components of cell wall and the role of cell wall on the insertion of Casein31 into bacteria will be investigated; Finally, the alterations in membrane structure will be analyzed based on protoplast, including the interaction between Casein31 and bacterial membrane, thinning, pore formation and the location of pores, and the mechanism of membrane disruption by Casein31 will be elucidated. The result of this project will provides a basis for the designing and development of antimicrobial peptides and the application of Casein31 on food preservation.