BIOC 2580 Lecture Notes - Lecture 5: Bond Length, Bond Order, Keratin

• School: University of Guelph
• Department: Biochemistry
• Course: BIOC 2580
• Professor: Enoka Wijekoon

Document Summary

Won 2 nobel prizes: chemistry and peace. Key finding: the peptide bond has double bond character. The peptide bond has two resonance forms, one with a double bond. Pauling compared lengths of c-n bonds to correlate bond length with bond order: normal c-n is 1. 49 , peptide c-n is 1. 32 , normal c=n is 1. 27 . A peptide bond is rigid, fixed in trans-geometry, because it behaves more like a double bond than a single bond. Peptide bond forms rigid planes connecting tetrahedral -c atoms. In normal peptide chain, -amino and -carboxylate are locked in rigid planar peptide bonds, only the two bonds to -carbon can rotate freely. Restricted bond rotation leads to only a few possible structures. Restricted bond rotation limits freedom of motion, so that only a few regular structure can form. If there is no regular, repeating structure, random coil is formed.