Characterization of water molecule in biological tissues and foods.

生物组织和食物中的水在生物学和物理化学方面都发挥着重要作用。水质子弛豫时间T1和T2反映了水所处的不同环境以及水与周围组织或生物大分子的不同相互作用。本研究以不同孔径和含水量的葡聚糖凝胶为模型化合物，考察了影响T1和T2的因素，如区室水的大小、含水量或周围基质的柔韧性。在T_2弛豫时间分析中发展了多指数分析过程，并应用于犬心肌组织定征。水分子的动力学行为也与室壁水的特性有关。研究的第二个目的是用自旋探针-ESR方法来明确水的热运动。探针的旋转相关时间反映了探针与周围水分子的碰撞速率，结果表明：1）弛豫时间强烈依赖于凝胶的孔径和含水量。运动行为中出现弛豫时间冲突的临界尺寸是G25凝胶的尺寸。结果发表在Magn.Reson.Med. 9，1-7（1989）中。2)松弛过程是由两种相互作用引起的，一种是分子内和分子间的偶极相互作用，另一种是凝胶基质中结合水与羟基质子之间的质子交换。后者的机制是占主导地位的情况下，G25凝胶和前者是占主导地位的凝胶与更大的孔比G25的水。3)自旋探针在G25凝胶中的旋转相关时间和旋转扩散活化能与其它凝胶中的有很大的不同。有趣的是，在ESR和NMR中观察到的特定运动性质恰好发生在观察到异常热行为的条件下。

Water in biological tissues and foods plays an important role both biologically and physicochemically. Relaxation times of water proton, T1 and T2, reflect different environments of water and different interactions of water with the surrounding tissues or biological marcomolecules. In the present research such factors determining T1 abd T2 as the size of compartmentalized water, water content or flexibility of the surrounding matrix were investigated by using sephadex gels with various pore sizesand water contents as the model compound. Multi-exponential analysing process was developed in the analysis of T2 relaxation time and applied to tissue characterization of the myocardium of dog.Dynamic behavior of water molecules also relates to characteristic of compartmentalized water. The second purpose of the research is to make the thermal motion of water clear by spin probe-ESR method. Rotational correlation times of the probe reflects the rate of confliction between the probe and surrounding water molecules.Results are summalized as follows; 1) Relaxation times depend strongly on pore size of gel and water content. A critical size in motional behavior at which a confliction of relaxation times appeared was the size of G25 gel. The result was published in Magn.Reson.Med. 9, 1-7(1989). 2) Relaxation process was caused by two interactions, one is intra- and inter- molecular dipolar interaction and the other is proton exchange between bound water and hydroxyl proton of gel matrix. The latter mechanism was dominant in the case of G25 gel and the former one was dominant for water in gels with larger pore than G25. 3) Rotational correlation time and activation enerby of rotational diffusion of spin probe in G25 gel are quite different from those in other gels. It is interesting that the specific motional property observed in ESR and NMR occurs just under the condition in which the abnormal thermal behavior was observed.