MBB 222 Lecture Notes - Lecture 9: C-Terminus, Peptide, Ramachandran Plot
20 Dec 2018
School
Department
Course
Professor
Document Summary
Learning objective: know that a protein sequence is always written from the amino (n-terminus) to the carboxyl terminus (c-terminus). Fyi: the main chain is everything but the side chains. C and the carbonyl carbon (n, c , c). The peptide bond has partial double bond character due to resonance. The delocalization of electrons in the peptide bond (c-n) fixes the amide group and its flanking c atoms in a plane. The peptide backbone cannot rotate around the peptide bond. This conformational restriction limits the way a protein can fold. Rotation can occur about the backbone bonds with c (n-c , c -c). With the lack of rotation around the peptide bond, the points of flexibility along the backbone of the protein occur in the bonds to the -carbon. Peptide backbones are free to rotate around two bonds, n-c (phi, ) and c -c (psi, ), allowing proteins to fold in many ways.
