Ab initio SCF investigation of the intramolecular hydrogen bonding in δ-aminopentanoic acid

1995 ◽  
Vol 6 (1) ◽  
pp. 15-24 ◽  
Author(s):  
Michael Ramek
Keyword(s):  
Hydrogen Bonding ◽  
Ab Initio ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Hydrogen

Peptide model XXVIII: An exploratory ab initio and density functional study on the side-chain-backbone interaction in N-acetyl-L-cysteine- N-methylamide and N-formyl-L-cysteinamide in their γL-backbone conformations

2002 ◽  
Vol 80 (7) ◽  
pp. 832-844 ◽  
Author(s):  
M A Zamora ◽  
H A Baldoni ◽  
A M Rodriguez ◽  
R D Enriz ◽  
C P Sosa ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Energy Surface ◽  
Geometry Optimization ◽  
Intramolecular Hydrogen Bonding ◽  
Functional Study ◽  
Side Chain ◽  
Intramolecular Hydrogen

A conformational and electronic study on the energetically preferred conformations (γL) of N- and C-protected L-cysteine (P-CONH-CH(CH2SH)-CONH-Q, where P and Q may be H or Me) was carried out. After restraining the backbone (BB) conformation to its global minimum (γL or C7eq), all nine possible side-chain (SC) conformations were subjected to geometry optimization at the HF/3–21G and the B3LYP/6–31G(d,p) levels of theory. Seven of the nine side-chain conformers were located on the potential-energy surface. All conformers were subjected to an AIM (atoms in molecules) analysis. This study indicates that three of the seven optimized conformers exhibited either or both SC [Formula: see text] BB- or BB [Formula: see text] SC-type intramolecular hydrogen bonding. Five conformers, however, had distances between a proton and a heteroatom that suggested hydrogen bonding.Key words: L-cysteine diamides, side-chain potential-energy surface, ab initio and DFT geometry optimization, AIM analysis, intramolecular hydrogen bonding.

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