Development of measurement system of function analysis of membrane using low-coherence interferometry

通过本研究项目，我们开发了利用低相干干涉仪进行膜功能分析的体内测量方法。所研制的测量系统用于人工膜（DPPC）和大鼠肠系膜的相变检测。特别详细考察了膜环境对相变的影响；结果发现，磷脂双分子层的相变与分子结构密切相关。(1)利用低相干干涉仪测量薄膜的折射率和厚度，其相变检测精度分别为0.1%和0.1μm。相变使膜的透射率发生了剧烈的变化。(2)实验将DPPC和大鼠肠系膜浸泡在缓冲液中，通过改变缓冲液的pH值来检测其相变。在DPPC和大鼠肠系膜中，随着pH值的降低，主相转变的温度升高。提示大鼠肠系膜主要由磷脂双分子层组成。(3)在DPPC中加入乙醇时，当乙醇浓度为bb0 ~ 25mg/ml时，亚相变消失。这种相变的剧烈变化是由于磷脂双层转变为数字间结构。(4)加入表面活性剂（棕榈酸），磷脂双分子层转变为胶束；因此，正常的相变完全消失。(5)另一方面，乙醇和表面活性剂的加入对大鼠肠系膜的相变没有影响。提示蛋白质和胶原蛋白干扰了大鼠肠系膜分子结构的转变；也就是说，即使在乙醇和表面活性剂存在的情况下，大鼠肠系膜中的磷脂双分子层仍能维持。(6)为了在体内测量，采用分辨率仅为1.3μm的超低相干干涉技术，展示了大鼠肠系膜的断层扫描图像。在实验结果的基础上，如上所述，我们正计划开发一种用于生理学领域的实用测量系统。少

Through this research project, we have developed in vivo measurement method for function analysis of membrane, using the low-coherence interferometery. The developed measurement system was used for detection of phase transition of both artificial membrane(DPPC)and rat mesentery. In particular, influence of circumstances of membrane on the phase transition was examined in detail ; as a result, it was found that the phase transition was closely related to the molecular structure of phospholipid bilayers.(1)In our developed system, refractive index and thickness of membrane are measured with an accuracy of 0.1% and 0.1μm, respectively, for detection of phase transition, using the low coherence interferometery. The transmission of membrane changes drastically by phase transition.(2)In the experiment, DPPC and rat mesentery were immersed in buffer solution, and the phase transition was detected by changing pH of buffer solution. In both DPPC and rat mesentery, it was found that the temperat … More ure for the main phase transition became higher as pH decreases. This result indicates that rat mesentery mainly consists of phospholipid bilayers.(3)In the case where ethanol is added to DPPC, the sub phase transition disappears for ethanol concentration of >25mg/ml. This drastic change for phase transition is due to the fact that phospholipid bilayers transforms to an inter digital structure.(4)By addition of surface active agent(palmitic acid), phospholipid bilayers transforms to micelle ; therefore, the normal phase transition disappears completely.(5)On the other hand, phase transition of rat mesentery is not influenced by addition of ethanol and surface active agent. This results suggests that protein and collagen disturb transformation of molecular structure of rat mesentery ; in other words, phospholipid bilayers are maintained in rat mesentery even in the presence of ethanol and surface active agent.(6)In order for in vivo measurement, a tomography image of a piece of rat mesentery was demonstrated, using the ultra-low coherence interferometry, which ere the resolution is only 1.3μm.On the basis of the experimental results, as described above, we are planning to develop a practical measurement system used in the field of physiology. Less