[M-IS08] アストロバイオロジー

[MIS08-P09] Experiments on circularly polarized VUV light irradiation on racemic amino acid sanples to verify cosmic scenario of homochirality

*小林 政弘¹、高橋 淳一²、太田 絋志³、松尾 光一⁴、エイブラハム モハメッド⁴、湊 丈俊³、藤森 玄⁵、加藤 政博^4,3、小林 憲正⁵、癸生川 陽子⁶、中村 浩章¹ (1.核融合科学研究所、2.神戸大学、3.分子科学研究所、4.広島大学、5.横浜国立大学、6.東京科学大学)

キーワード：ホモキラリティ、真空紫外円偏光、円二色性、光化学

The homochirality of life remains one of the most enigmatic issues in the study of the origin of life. A proposed mechanism for symmetry breaking involves irradiation by circularly polarized light (CPL). To investigate the photoreaction of amino acids under CPL irradiation, a vacuum ultraviolet (VUV) CPL irradiation system was developed at the synchrotron light source UVSOR-III. Hydrogen Lyman-α CPL (121.6 nm) is considered a potential asymmetric source in space. Therefore, racemic alanine film samples were irradiated with Lyman-α CPL to explore the photoreaction of biomolecules. Circular dichroism (CD) spectra measurements revealed that irradiation with right- (left-) handed CPL induced a positive (negative) anisotropy factor g in the wavelength range of 180–240 nm. However, the spectra differed from those of enantiopure alanine, exhibiting broad wavelength ranges and no sign change. Liquid chromatography-mass spectrometry (LC-MS) measurements indicate formation of larger molecules, such as oligomeric alanine adducts or modified oligomers after the Lyman-a CPL irradiation. Additionally, CPL irradiation considerably changes the microstructure of the alanine film surface, leading to the formation of circular network aggregates on the scale of 100 nm. The morphology changes in the alanine film and/or the formation of the larger molecules could be possible causes of the modified anisotropy factor spectra compared to those of enantiopure alanine. These findings highlight the need for further research on the photoreaction of biomolecules in solid states under VUV CPL irradiation, particularly in the photoionization energy range, to validate the cosmic scenario of homochirality.