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Title
Japanese:Cation-responsive cavity expansion of valinomycin revealed by cryogenic ion trap infrared spectroscopy 
English:Cation-responsive cavity expansion of valinomycin revealed by cryogenic ion trap infrared spectroscopy 
Author
Japanese: 平田 圭祐, 佐藤 映虹, LISY JAMES MICHAEL, 石内 俊一, 藤井 正明.  
English: Keisuke Hirata, Eiko Sato, James M. Lisy, Shun-ichi Ishiuchi, Masaaki Fujii.  
Language English 
Journal/Book name
Japanese:Physical Chemistry Chemical Physics 
English:Physical Chemistry Chemical Physics 
Volume, Number, Page Vol. 25    No. 2    pp. 1075-1080
Published date Dec. 2022 
Publisher
Japanese:The Royal Society of Chemistry 
English:The Royal Society of Chemistry 
Conference name
Japanese: 
English: 
Conference site
Japanese: 
English: 
Official URL http://dx.doi.org/10.1039/D2CP04570B
 
DOI https://doi.org/10.1039/D2CP04570B
Abstract Valinomycin (VM) is a natural K+-selective ionophore that transports K+ through the cell membrane. VM captures K+ in its central cavity with a C3-symmetric ﾎｲ-turn-like backbone. Although the binding affinity is drastically decreased for the VM-sodium (Na+VM) complex with respect to K+VM, VM holds relatively high affinity to Rb+ and Cs+. The high affinity for larger ions irrespective of ionic size seems to conflict with the expected optimal size matching model and raises questions on what factors determine ion selectivity. A combination of infrared spectroscopy with supporting computational calculations reveals that VM can accommodate larger Rb+ and Cs+ by flexibly changing its cavity size with the elongation of its folded ﾎｲ-turn-like backbone. The high affinity to Rb+ and Cs+ can be ascribed to a size-dependent cavity expansion. These findings provide a new perspective on molecular recognition and selectivity beyond the conventional size matching model.

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