title: Infrared probing of 4-azidoproline conformations modulated by azido configurations.
abstract: 4-Azidoproline (Azp) can tune the stability of the polyproline II (P(II)) conformation in collagen. The azido group in the 4R and 4S configurations stabilizes and destabilizes the P(II) conformation, respectively. To obtain insights into the dependence of the conformational stability on the azido configuration, we carried out Fourier transform (FT) IR experiments with four 4-azidoproline derivatives, Ac-(4R/S)-Azp-(NH/O)Me. We found that the amide I and azido IR spectra are different depending on the azido configuration and C-terminal structure. The origin of such spectral differences between 4R and 4S configurations and between C-terminal methylamide and ester ends was elucidated by quantum chemistry calculations in combination with (1)H NMR and time- and frequency-resolved IR pump-probe spectroscopy. We found that the azido configurations and C-terminal structures affect intramolecular interactions, which are responsible for the ensuing conformational and thereby IR spectral differences. Consequently, 4-azidoproline conformations modulated by azido configurations can be probed by IR spectroscopy. These findings suggest that 4-azidoproline can be both a structure-control and -probing element, which enables the infrared tracking of proline roles in protein structure, function, and dynamics.
authors.affiliation: Department of Chemistry, Korea University, Seoul, Korea.
authors.forename: Kyung-Koo
authors.initials: KK
authors.lastname: Lee
authors.forename: Kwang-Hee
authors.initials: KH
authors.lastname: Park
authors.forename: Cheonik
authors.initials: C
authors.lastname: Joo
authors.forename: Hyeok-Jun
authors.initials: HJ
authors.lastname: Kwon
authors.forename: Jonggu
authors.initials: J
authors.lastname: Jeon
authors.forename: Hyeon-Il
authors.initials: HI
authors.lastname: Jung
authors.forename: Sungnam
authors.initials: S
authors.lastname: Park
authors.forename: Hogyu
authors.initials: H
authors.lastname: Han
authors.forename: Minhaeng
authors.initials: M
authors.lastname: Cho
mesh_terms: D000577:Amides / Q000737:chemistry; D001386:Azides / Q000737:chemistry*; D008968:Molecular Conformation; D011392:Proline / Q000031:analogs & derivatives* / Q000737:chemistry; D011789:Quantum Theory; D017550:Spectroscopy, Fourier Transform Infrared; D013237:Stereoisomerism
chemical_list: C434308:4-azidoproline; D000577:Amides; D001386:Azides; D011392:Proline