title: Thermodynamic characterizations of an intramolecularly hydrogen bonded C5-structure across proteinogenic residue.
abstract: Thermodynamic investigations of a smallest possible intramolecularly hydrogen bonded C5-structure, across a Thr residue, in model peptides Boc-Xxx-Thr-NH2 (Xxx = Ile, 1 or Leu, 2), indicated unusual thermal stability of the structure in non-polar medium. An analysis of van't Hoff plots, constructed from variable temperature 1H NMR data, yielded the thermodynamic parameters of a hydrogen bonded five-membered ring. The non-significance of the spatial organizations of the preceding CdeltaH3 bearing hydrophobic proteinogenic residue on the thermal stability of the C5-structure has been observed. The results revealed that the contribution of this element of secondary structure is quantifiable and the stability appeared to be roughly comparable to other intramolecularly hydrogen bonded reverse turn structures frequently observed in polypeptides and proteins.
authors.affiliation: Institute of Microbial Technology, Chandigarh, India. kishore@koel.imtech.ernet.in
authors.lastname: Ashish
authors.forename: R
authors.initials: R
authors.lastname: Kishore
mesh_terms: D000577:Amides / Q000737:chemistry; D006860:Hydrogen Bonding; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013696:Temperature; D013816:Thermodynamics; D013912:Threonine
chemical_list: D000577:Amides; D010455:Peptides; D013912:Threonine