Analyzing the N-H+center dot center dot center dot pi interactions of protonated tryptophan and phenylalkylamines using QTAIM, NCl, and NBO

Author(s)

Rodrigues-Oliveira, Andre F. ^[1] ; Batista, Patrick R. ^[1] ; Ducati, Lucas C. ^[1] ; Correra, Thiago C. ^[1]

Affiliation

^[1] Univ Sao Paulo, Dept Fundamental Chem, Inst Chem, Av Prof Lineu Prestes 748, BR-05508000 Sao Paulo, SP - Brazil

• Document type: Journal article
• Source: THEORETICAL CHEMISTRY ACCOUNTS; v. 139, n. 8 JUL 14 2020.
• Web of Science Citations: 0

Abstract

Tryptophan and phenylakylamines (PAAs) are important biomolecules, which are involved in a myriad of processes. These molecules have been experimentally reported to exhibit N-H+center dot center dot center dot pi interactions in their protonated form; however, this has not been theoretically investigated in detail. Generally, such interactions are observed in diverse biological systems, and their evaluation would be useful for understanding protein folding and functioning. Therefore, in this study, we have described the N-H+center dot center dot center dot pi interactions of the abovementioned classes of molecules using the Quantum Theory of Atoms In Molecules (QTAIM), Natural Bond Orbital (NBO), and Non-Covalent Interaction (NCI) analyses. The results of our N-H+center dot center dot center dot pi interaction energy calculations were consistent with the experimental energies derived from the redshift of the vibrational stretches. The energy values obtained using the QTAIM-based Espinosa's approach provided a relatively better result than similar approaches previously reported in the literature. Furthermore, we observed that the N-H+center dot center dot center dot pi interaction energy in tryptophan is weaker than the resonance-assisted hydrogen bond energy of the N-H+center dot center dot center dot O=C interactions of its three most stable conformers accessible at room temperature. In contrast, the strength of the N-H+center dot center dot center dot pi interaction in PAAs was observed to increase with increasing alkyl lateral chain length. The increased flexibility of longer chains increases the distance between nitrogen and the phenyl ring without disturbing the N-H+center dot center dot center dot pi interaction. (AU)

• FAPESP's process: 19/25634-9 - Real-time reaction analysis in complex matrices by advanced mass spectrometry techniques
• Grantee: Thiago Carita Correra
• Support Opportunities: Regular Research Grants
• FAPESP's process: 14/15962-5 - Reaction mechanism of asymmetric catalysts by mass spectrometry and gas-phase vibrational ion spectroscopy
• Grantee: Thiago Carita Correra
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 15/08539-1 - Multi-User Equipment approved in grant 2014/15962-5: ion trap mass spectrometer modified to perform infrared vibrational spectroscopy (IRMPD)
• Grantee: Thiago Carita Correra
• Support Opportunities: Multi-user Equipment Program
• FAPESP's process: 18/07308-4 - Effect of solvent on shielding tensor and coupling constant calculations of platinum (iii) dinuclear complexes via ab initio molecular dynamics
• Grantee: Patrick Rodrigues Batista
• Support Opportunities: Scholarships in Brazil - Doctorate