Chiral compounds are known to have different physiological activities depending on their absolute configuration. As a familiar example, it is known that L-glutamic acid feels umami, whereas D-glutamic acid feels bitter while thalidomide R body has sedative action, whereas S form has teratogenicity . In addition, functional studies of chiral compounds are actively studied in the development of next generation functional molecules. In this way, studies on chiral compounds are diversified, mainly in natural products, pharmaceuticals, functional molecules, etc. An important task among them is structure analysis of chiral compounds. X-ray diffraction method, nuclear magnetic resonance analysis (NMR), electronic circular dichroism spectroscopy (ECD) using ultraviolet and visible light, etc. are used as structural analysis of chiral compound. This time we will introduce examples of measurement of chiral molecules using vibration circular dichroism spectroscopy (VCD) using infrared light.

VCD is a technique to measure the difference in absorption intensity between counterclockwise and clockwise infrared circularly polarized light. The characteristic of VCD is that almost all organic compounds can be applied like infrared spectroscopy. In addition, by comparing the measurement result by VCD with the calculation result by molecular orbital calculation, absolute configuration of sample can be determined. However, since the peak intensity of the VCD spectrum is about 1,000 to 10,000 times weaker than that of ordinary infrared spectroscopy, a stable device with high sensitivity and small baseline fluctuation is required. The FVS - 6000 can accurately measure weak VCD spectrum peaks by mounting a high - sensitive detector, optical filter, constant - temperature PEM and so on. Here, FVS-6000 is used, and hemoglobin is measured as representative various chiral compound and model protein, and good results are obtained.