軟X線吸収分光法を用いたリン酸の二重結合性の観測に成功 －生化学反応の詳細なメカニズム解明に道筋－

2026-06-26 分子科学研究所

図1 : 固体と液体のリン酸のO K吸収端XASスペクトル。固体のNaH₂PO₄からNa₃PO₄になると、P=O π*ピークの強度が大きくなることが分かる。Na₃PO₄水溶液ではP=O π*ピークが消失することが分かる。

＜関連情報＞

• https://www.ims.ac.jp/news/2026/06/0626.html
• https://pubs.acs.org/doi/10.1021/acs.jpclett.6c00737

酸素K吸収端X線吸収分光法による固体と液体のリン酸の二重結合性の観測 Double-Bond Character of Phosphates in Solid and Liquid Phases Probed by Oxygen K-Edge X-ray Absorption Spectroscopy

Masanari Nagasaka,Fumitoshi Kumaki,Jun-ichi Adachi

The Journal of Physical Chemistry Letters  Published June 1, 2026

DOI:https://doi.org/10.1021/acs.jpclett.6c00737

Abstract

Double-bond character of phosphate groups has important roles for biological reactions and was investigated using the P═O π* peaks in the oxygen K-edge X-ray absorption spectroscopy (XAS). The O K-edge XAS spectra of phosphates in the solid phase found that the double-bond character of phosphates is enhanced as the negative charge increases, where the weak P═O π* peak was observed in NaH₂PO₄, but distinct P═O π* peaks were obtained in Na₂HPO₄ and Na₃PO₄. Conversely, the P═O π* peaks were not observed in the XAS spectra of any phosphates in the liquid phase, indicating a substantial reduction in the double-bond character of the phosphate groups owing to the interaction of Na⁺ ions and the formation of hydration structures. The XAS spectra of diphosphates validated that change in the double-bond character of the phosphate groups is a general phenomenon also observed in high-energy phosphate compounds, which is closely related to the reactivity of adenosine triphosphate hydrolysis.