CHE 4341 Lecture Notes - Lecture 2: Peptide, Collagen, Fibroin
Document Summary
Proline"s cyclic side chain sterically destabilizes an helix. > thus, pro not likely found in an helix. Steric (or charge) repulsion by adjacent bulky (or like-charged) aa. > -keratin coiled coil motif of 2 amphipathic -helices. This is a super secondary structure (more info. in ch. 6 video lecture) It is a key structural material in hair, skin, nails. Horns are made up of keratin covering a core of live bone. -keratin rich in cys == forms disulfide bonds. Can come from same polypeptide, completely different sections of a polypeptide or even different polypeptides. H-bonds occur in the y axis b/t aa"s on adjacent strands perpendicular to strand direction (y axis) Side chains (r-groups) alternate in pointing above & below in the z-axis perpendicular to h-bonds and strands. Run in opposite n to c-terminal direction. Run in the same n to c-terminal direction. Repeating unit of 2 aa residues w/distance 7a.
