Thermodynamic origin of prolyl peptide bond isomers

✍ Scribed by Eric S. Eberhardt; Stewart N. Loh; Ronald T. Raines

• Book ID: 104225794
• Publisher: Elsevier Science
• Year: 1993
• Tongue: French
• Weight: 140 KB
• Volume: 34
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)93377-x

✦ Synopsis

The truns (Z) isomer of a typical peptide bond is favomd greatly over the cis Q isomer. Iu contrast, a trans bond involving the nitrogen atom of a proline residue is favored only slightly, and both isomers ate common in peptides and folded proteins.' &towing the thermodynamic origin for the relative stahility of X-Pm bond isomers is essential for understanding the conformation of peptides and proteins containing such bonds.2 The diffemnce in enthalpy for the cir and nwts isomers of X-Pm bonds in aqueous solution has heen reported to be zero for model pe~tides.~ or small (ca 1.2 kcal/mol) for poly(P~+Gly).~ The difference in free energy for the cis and rruns isomers of amides has been calculated with the 6-3 lG** basis set of the Gaussian 82 ab initio program to be largely enthalpic in the gas phase: We have synthesized a peptide containing 'C-