title: Density functional theory (DFT) and natural bond orbital (NBO) study of vibrational spectra and intramolecular hydrogen bond interaction of L-ornithine-L-aspartate.
abstract: In this study, exhaustive conformations of (S)-4-amino-4-carboxybutan-1-aminium (S)-3-amino-3-carboxypropanoate (LOLA) have been scanned. Experimental and theoretical studies on the structure and vibrations of the title compound are presented. The optimized molecular structure, vibrational wavenumbers, Mulliken atomic charges, natural bond orbital (NBO) and molecular electrostatic potential studies have been performed by density functional theory (DFT) using B3LYP method with the 6-311++G(d,p) basis set. Computed X-ray powder diffraction (XRPD) data has been carried out by DFT calculations and ab initio from measured XRPD finding. The LOLA molecular geometry has been determined which exists in the form of salt by intramolecular H-bonds and ionic bonding. Moreover, calculated vibrational frequencies were applied to simulate IR and Raman spectra of the title compound which showed excellent agreement with observed spectra. Reliable vibrational assignments have been made on the basis of potential energy distribution (PED) and 0.992 has been obtained by least squares method which is the uniform scaled factor for theoretical frequencies at 6-311++G(d,p) basis set. In addition, the hydrogen bonding in LOLA molecule has been explored by calculation of the hyperconjugative charge transfer interaction on [LP X-σ(*)(Y-H)], under NBO analysis, Mulliken atomic charge analysis, molecular electrostatic potential map (MEP) and vibrational spectra. Finally, HOMO-LUMO of the title compound has been plotted for predicting reactive sites.
authors.affiliation: Key Laboratory of Structure-Based Drug Design and Discovery, Shenyang Pharmaceutical University, Ministry of Education, Shenyang 110016, PR China.
authors.forename: Linwei
authors.initials: L
authors.lastname: Li
authors.affiliation: Key Laboratory of Structure-Based Drug Design and Discovery, Shenyang Pharmaceutical University, Ministry of Education, Shenyang 110016, PR China.
authors.forename: Chengjun
authors.initials: C
authors.lastname: Wu
authors.affiliation: Key Laboratory of Structure-Based Drug Design and Discovery, Shenyang Pharmaceutical University, Ministry of Education, Shenyang 110016, PR China.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Key Laboratory of Structure-Based Drug Design and Discovery, Shenyang Pharmaceutical University, Ministry of Education, Shenyang 110016, PR China.
authors.forename: Lixia
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Structure-Based Drug Design and Discovery, Shenyang Pharmaceutical University, Ministry of Education, Shenyang 110016, PR China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Li
authors.affiliation: Pharmacy Department, Shenyang Pharmaceutical University, Shenyang 110016, PR China. Electronic address: freescs@163.com.
authors.forename: Changshan
authors.initials: C
authors.lastname: Sun
authors.affiliation: Key Laboratory of Structure-Based Drug Design and Discovery, Shenyang Pharmaceutical University, Ministry of Education, Shenyang 110016, PR China. Electronic address: suntiemin@126.com.
authors.forename: Tiemin
authors.initials: T
authors.lastname: Sun
mesh_terms: D000588:Amines / Q000737:chemistry; D018360:Crystallography, X-Ray; D004151:Dipeptides / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D055672:Static Electricity; D013816:Thermodynamics; D014732:Vibration
chemical_list: D000588:Amines; D004151:Dipeptides; C002939:ornithylaspartate
keywords: DFT; Infrared; NBO; Vibrational assignment; X-ray powder diffraction; l-Ornithine–l-Aspartate