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

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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