Conformers of Gaseous Serine

• Published in: Journal of chemical theory and computation Vol. 12; no. 8; pp. 3571 - 3582
• Main Authors: He, Kedan, Allen, Wesley D
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 09.08.2016
• Subjects: Absorption; Amino acids; Anharmonicity; Computation; Constants; Distortion; Gases - chemistry; Hydrogen Bonding; Infrared; Molecular Conformation; Rotational spectra; Serine - chemistry; Spectrophotometry, Infrared; Thermodynamics
• ISSN: 1549-9618; 1549-9626
• DOI: 10.1021/acs.jctc.6b00314

The myriad conformers of the neutral form of natural amino acid serine (Ser) have been investigated by systematic computations with reliable electronic wave function methods. A total of 85 unique conformers were located using the MP2/cc-pVTZ level of theory. The 12 lowest-energy conformers of serine fall within a 8 kJ mol–1 window, and for these species, geometric structures, precise relative energies, equilibrium and vibrationally averaged rotational constants, anharmonic vibrational frequencies, infrared intensities, quartic and sextic centrifugal distortion constants, dipole moments, and 14N nuclear quadrupole coupling constants were computed. The relative energies were refined through composite focal-point analyses employing basis sets as large as aug-cc-pV5Z and correlation treatments through CCSD­(T). The rotational constants for seven conformers measured by Fourier-transform microwave spectroscopy are in good agreement with the vibrationally averaged rotational constants computed in this study. Our anharmonic vibrational frequencies are compared to the large number of experimental vibrational absorptions attributable to at least six conformers.