QTAIM-Based Characteristic Group Infrared Intensities of Amino Acids and Their Transference to Peptides

Author(s)

Silva, Arnaldo F. ; Duarte, Leonardo J. ; Bruns, Roy E.

• Document type: Journal article
• Source: Journal of Physical Chemistry A; v. 120, n. 42, p. 8387-8399, OCT 27 2016.
• Web of Science Citations: 2

Abstract

Dynamic atomic contributions (DACs) to the infrared intensities of 14 amino acids have been transferred to three peptide molecules, glycylglycine, trialanine, and the melanocyte-inhibiting factor MIF-1, to estimate the infrared intensities of the most strategic peptide bands. The DACs of the amino acids and infrared intensities of the peptides were determined at the DFT B3LYP/6-311+(d,p) level. The Quantum Theory of Atoms In Molecules (QTAIM) Charge Charge Transfer Dipolar Polarization (CCTDP) model at this Density Functional Theory (DFT) level was used to classify the O-H, NH2, N-H, and C=O stretching as well as the NH2 bending characteristic groups for use in the transference procedure. Contrary to the frequencies, the intensities within these groups can have very diverse values, although their electronic structure changes upon vibration have predictable QTAIM behaviors for each group. Compared to the DFT calculated values, the two transferred O-H stretching intensities of the peptides are estimated with a root-mean-square (rms) error of 19.1 km mol(-1). Six NH2 symmetric and antisymmetric stretching intensities were determined with a 9.9 km mol(-1) error. The eight estimated C=O stretching bands have a rms error of 78.0 km mol(-1) or 23.6% of the average DFT peptide C=O intensity of 328.4 km mol(-1). The proposed procedure is applicable to experimental infrared intensities if a calibration set of molecules with known atomic polar tensors and normal coordinate transformations is available. (AU)

• FAPESP's process: 14/21241-9 - The inclusion of polarization effects in the description of amino acids and peptides through the use of atomic multipoles obtained from electron densities
• Grantee: Arnaldo Fernandes da Silva Filho
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 16/07411-4 - Assessment, validation and interpretation of the absolute infrared intensities of the vibrational bands of chlorofluoromethanes
• Grantee: Leonardo José Duarte
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 09/09678-4 - A CCFDF/QTAIM model investigation of fundamental infrared intensity sum rules
• Grantee: Roy Edward Bruns
• Support Opportunities: Regular Research Grants