低场核磁共振分析乳酸菌细胞中水分分布及其变化

Water distribution and variation in lactic acid bacteria using low-field nuclear magnetic resonance

该文选取乳酸菌发酵剂为研究对象,利用低场核磁共振(low-field nuclear magnetic resonance,LF-NMR)分析方法研究乳酸菌细胞水分分布及其变化。横向弛豫时间(T_(2))可以提供样品组织结构中的水分状态及水分分布的信息。根据弛豫时间T_(2)可以将乳酸菌细胞的水分依次划分为结合水(T_(21))、半结合水(T_(22))以及自由水(T_(23)),并分别对应不同的细胞结构中,包括T_(21)<10 ms对应与细胞壁结合的水质子;10 ms<T_(22)<100 ms对应细胞质中与蛋白质等大分子结合的水质子;T_(23)>100 ms具有较高的自由度,代表细胞壁水。渗透压冲击会改变乳酸菌细胞内水分分布情况,使得水分的自由度增大;而反复冻融会使得细胞内的水分结成冰晶,损伤细胞结构,造成解冻后细胞内水流失,导致细胞塌陷破裂。研究结果表明,LF-NMR分析方法可以准确地提供乳酸菌细胞内部水分分布信息,并且细胞内部水分分布情况的变化与细胞损伤情况密切相关。

In this paper,water distribution and variation were investigated in lactic acid bacteria using low field nuclear magnetic resonance(LF-NMR).Three different water fractions in bacterial cells,bounding water(T_(21)),semi-combined water(T_(22))and free water(T_(23))were represented respectively,according to the information of water distribution provided by transverse relaxation time(T_(2)),T_(21),corresponding to water particles bound to cell wall,was less than 10 ms,T_(22),corresponding to the water particles bound to proteins and other macromolecules in the cytoplasm and representing intracellular water,is in the range of the 10 ms to 100 ms,T_(23),corresponding to water particles which have a high degree of freedom and representing extracellular water,is larger than 100 ms.Osmotic shock can change water distribution in lactic acid bacteria cells and increase the degree of water freedom.The multigelation can lead to formation of ice crystals from the intracellular water,which further influence the cell structure,and then cause the loss of intracellular water,resulting in cell collapse and rupture finally.LF-NMR analysis could provide the quantitative information of water distribution information in lactic acid bacteria cells precisely,and prove water distribution in the cells is closely related to cell damage further.