Structures, vibrational frequencies, topologies, and energies of hydrogen bonds in cysteine‐formaldehyde complexes

Abstract

ABSTRACT:The hydrogen bonding interactions between cysteine (Cys) and formaldehyde (FA) were studied with density functional theory regarding their geometries, energies, vibrational frequencies, and topological features of the electron density. The quantum theory of atoms in molecules and natural bond orbital analyses were employed to elucidate the interaction characteristics in the Cys-FA complexes. The intramolecular hydrogen bonds (H-bonds) formed between the hydroxyl and the N atom of cysteine moiety in some Cys-FA complexes were strengthened because of the cooperativity. Most of intermolecular H-bonds involve the O atom of cysteine/FA moiety as proton acceptors, while the strongest H-bond involves the O atom of FA moiety as proton acceptor, which indicates that FA would rather accept proton than providing one. The H-bonds formed between the CH group of FA and the S atom of cysteine in some complexes are so weak that no hydrogen bonding interactions exist among them. In most of complexes, the orbital interaction of H-bond is predominant during the formation of complex. The electron density (q b ) and its Laplace (! 2 q b ) at the bond critical point significantly correlate with the H-bond parameter dR, while a linearly relationship between the second-perturbation energy E(2) and q b has been found as well.

Theoretical Study on the Hydrogen Bonding Interactions in Paracetamol-Water Complexes

“…According to QTAIM, the H-bond, including inter-or intramolecular H-bonds, is characterized by the BCPs between H-donor (X-H) and H-acceptor (Y), and ring structure formed by multiple H-bonds is characterized by a ring critical point (RCP). The shorter distance between the RCP and corresponding BCP means less stability of the H-bond [47][48][49][50] . As a note, the RCP at the center of the ring of benzene has nothing to do with H-bond.…”

Preparation and characterization of cysteine‐formaldehyde cross‐linked complex for CO2 capture

“…Compared with the results shown in Figures and , the active proton peaks of the amino group near 8.52 and hydroxyl near 12.39 in Figure were not detected and shown in Figure . The chemical shift at 1.24 was possibly caused by a residual thiol (HS) restrained hydrogen bond . The chemical shift at 1.79 was possibly ascribed to the proton from conjugated carbon (C‐CH 2 ‐C) in the structures (R‐4,3’) and (R‐5,0’).…”

“…The chemical shift at 1.24 was possibly caused by a residual thiol (HS) restrained hydrogen bond. [50] The chemical shift at 1.79 was possibly ascribed to the proton from conjugated carbon (C-CH 2 -C) in the structures (R-4,3') and (R-5,0'). The double peaks appearing near 3.36 (one narrow peak and one wide peak) resulted from the protons of conjugated carbon (S- The demonstrated bridge connection action of the formaldehyde by element analysis indicated that the nucleophilic substitution SN2 of carbonyl carbon for formaldehyde mainly occurred among thiol, amine, and carbon with α-H from cysteine, which could be regarded as electron donors.…”

Interaction of Cysteine with Li+ and LiF in the Presence of (H2O)n (n = 0–6) Clusters

“…Cysteine (Cys) is an important amino acid carrying an amino (NH 2 ) group and a carboxylic acid (COOH) group, which can be the donor or acceptor of HBs. Besides, the thiol (SH) group of Cys can also donate and accept protons . The interaction of Cys and alkali metal cation complexes has already been investigated both theoretically and experimentally. ,,, In the gas phase, zwitterionic forms of Cys (Z-Cys) are reported to be neutralized during interaction with alkali and alkaline earth metal cations by Shankar et al, who determined that the structure of cysteine is not modified upon metal ion substitution, but the metal ion binding site changes noticeably.…”