title: Contributions of various noncovalent bonds to the interaction between an amide and S-containing molecules.
abstract: N-Methylacetamide, a model of the peptide unit in proteins, is allowed to interact with CH(3) SH, CH(3)SCH(3), and CH(3)SSCH(3) as models of S-containing amino acid residues. All of the minima are located on the ab initio potential energy surface of each heterodimer. Analysis of the forces holding each complex together identifies a variety of different attractive forces, including SH⋅⋅⋅O, NH⋅⋅⋅S, CH⋅⋅⋅O, CH⋅⋅⋅S, SH⋅⋅⋅π, and CH⋅⋅⋅π H-bonds. Other contributing noncovalent bonds involve charge transfer into σ* and π* antibonds. Whereas some of the H-bonds are strong enough that they represent the sole attractive force in several dimers, albeit not usually in the global minimum, charge-transfer-type noncovalent bonds play only a supporting role. The majority of dimers are bound by a collection of several of these attractive interactions. The SH⋅⋅⋅O and NH⋅⋅⋅S H-bonds are of comparable strength, followed by CH⋅⋅⋅O and CH⋅⋅⋅S.
authors.affiliation: Department of Chemistry and Biochemistry, Utah State University, Logan, 84322-0300, USA.
authors.forename: Upendra
authors.initials: U
authors.lastname: Adhikari
authors.forename: Steve
authors.initials: S
authors.lastname: Scheiner
mesh_terms: D000577:Amides / Q000737:chemistry*; D003198:Computer Simulation; D006860:Hydrogen Bonding; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry*
chemical_list: D000577:Amides; D010455:Peptides; D013455:Sulfur