유일태 (충북대학교)

허지영 (상명대학교)

김남준 (충북대학교)

유일태 (충북대학교)

정진호 (충북대학교)

은한준 (한국표준과학연구원연구원)

윤지연 (충북대학교)

허지영 (상명대학교)

김남준 (충북대학교)

Understanding the structural variations of conformational isomers in proteins is crucial for elucidating protein folding mechanisms. Here, we present a novel method for obtaining conformation-selective ultraviolet (UV)–UV hole burning (HB) spectra of ubiquitin ions ((Ubi^+zH)^+z, z = 7–10) produced via electrospray ionization. Our approach involves binding multiple N₂ molecules to ubiquitin ions ((Ubi^+zH)^+z(N₂)_m, m = 1–55) within a cryogenic ion trap. Upon exposure to UV irradiation, efficient fragmentation of (Ubi^+zH)^+z(N₂)_m occurs, primarily yielding bare (Ubi^+zH)^+z ions as fragments. The significant mass difference between the parent and fragment ions facilitates the acquisition of UV–UV HB spectra, which reveal the presence of at least two distinct conformers. Molecular dynamics simulations suggest that these conformers correspond to A-state structures, differing only in the interactions of a tyrosine residue with neighboring residues. Our findings underscore UV–UV HB spectroscopy of protein ions as a powerful tool for exploring diverse protein isomers.

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