title: Weak H-bonds. Comparisons of CH···O to NH···O in proteins and PH···N to direct P···N interactions.
abstract: Whereas CH···O H-bonds are usually weaker than interpeptide NH···O H-bonds, this is not necessarily the case within proteins. The nominally weaker CH···O are surprisingly strong, comparable to, and in some cases stronger than, the NH···O H-bonds in the context of the forces that hold together the adjacent strands in protein β-sheets. The peptide NH is greatly weakened as proton donor in certain conformations of the protein backbone, particularly extended structures, and forms correspondingly weaker H-bonds. The PH group is a weak proton donor, but will form PH···N H-bonds. However, there is a stronger interaction in which P can engage, in which the P atom, not the H, directly approaches the N electron donor to establish a direct P···N interaction. This approach is stabilized by the same sort of electron transfer from the N lone pair to the P-H σ* antibond that characterizes the PH···N H-bond.
authors.affiliation: Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322-0300, USA. steve.scheiner@usu.edu
authors.forename: Steve
authors.initials: S
authors.lastname: Scheiner
mesh_terms: D002244:Carbon / Q000737:chemistry; D006860:Hydrogen Bonding; D009584:Nitrogen / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*
chemical_list: D011506:Proteins; D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen; D010100:Oxygen