TY - JOUR
T1 - Intrinsic structure of pentapeptide Leu-enkephalin
T2 - Geometry optimization and validation by comparison of VSCF-PT2 calculations with cold ion spectroscopy
AU - Roy, Tapta Kanchan
AU - Kopysov, Vladimir
AU - Pereverzev, Aleksandr
AU - Šebek, Jiří
AU - Gerber, R. Benny
AU - Boyarkin, Oleg V.
N1 - Publisher Copyright:
© 2018 the Owner Societies.
PY - 2018
Y1 - 2018
N2 - The intrinsic structure of an opioid peptide [Ala2, Leu5]-leucine enkephalin (ALE) has been investigated using first-principles based vibrational self-consistent field (VSCF) theory and cold ion spectroscopy. IR-UV double resonance spectroscopy revealed the presence of only one highly abundant conformer of the singly protonated ALE, isolated and cryogenically cooled in the gas phase. High-level quantum mechanical calculations of electronic structures in conjunction with a systematic conformational search allowed for finding a few low-energy candidate structures. In order to identify the observed structure, we computed vibrational spectra of the candidate structures and employed the theory at the semi-empirically scaled harmonic level and at the first-principles based anharmonic VSCF levels. The best match between the calculated "anharmonic" and the measured spectra appeared, indeed, for the most stable candidate. An average of two spectra calculated with different quantum mechanical potentials is proposed for the best match with experiment. The match thus validates the calculated intrinsic structure of ALE and demonstrates the predictive power of first-principles theory for solving structures of such large molecules.
AB - The intrinsic structure of an opioid peptide [Ala2, Leu5]-leucine enkephalin (ALE) has been investigated using first-principles based vibrational self-consistent field (VSCF) theory and cold ion spectroscopy. IR-UV double resonance spectroscopy revealed the presence of only one highly abundant conformer of the singly protonated ALE, isolated and cryogenically cooled in the gas phase. High-level quantum mechanical calculations of electronic structures in conjunction with a systematic conformational search allowed for finding a few low-energy candidate structures. In order to identify the observed structure, we computed vibrational spectra of the candidate structures and employed the theory at the semi-empirically scaled harmonic level and at the first-principles based anharmonic VSCF levels. The best match between the calculated "anharmonic" and the measured spectra appeared, indeed, for the most stable candidate. An average of two spectra calculated with different quantum mechanical potentials is proposed for the best match with experiment. The match thus validates the calculated intrinsic structure of ALE and demonstrates the predictive power of first-principles theory for solving structures of such large molecules.
UR - http://www.scopus.com/inward/record.url?scp=85054391175&partnerID=8YFLogxK
U2 - 10.1039/c8cp03989e
DO - 10.1039/c8cp03989e
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C2 - 30234204
AN - SCOPUS:85054391175
SN - 1463-9076
VL - 20
SP - 24894
EP - 24901
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 38
ER -