Peptide Bond Flashcards
Features of Peptide bond
- Resonance stabilized (hence)
A. Less reactive than ester
B. Rigid and planar bond (but alpha C bond will rotate)
C. Large dipole moment in trans configuration - UV absorption
A. 220nm - Peptide bond
B. 280nm- aromatic bond - CN Bond - partial double bond character
UV absorbance by
1. Trytophan
2. Tyrosine
3. Phenylalanine
4. histidine, cysteine and Methionine
- 280nm
- 274nm
- 257nm
- 200 to 210nm
Formation of amino acid in
A. In vitro
B. In vivo
A. C-N terminal (by chemical method)
B. N- C terminal (by ribosome)
Primary Structure of protein suggests
- Molecular weight (Avg weight of a.a. - 110dalton
- Isoelectric point
- Traversing of protein through the membrane by hydropathy plot.
Bonds and their Rotation around peptide bond.
- Psi bond - between alpha carbon and carbonyl carbon
- Phi bond - between alpha carbon and amide nitrogen
- Omega bond - between carbonyl oxygen and amide hydrogen
Omega bond- a. 180 in trans configuration
B. 0 in cis configuration of carbonyl oxygen and amide hydrogen
Ramachandran plot in left handed amino acid (L chiral) and right handed (D chiral)
L chiral
1st quadrant - Alpha left handed( +,+)
2nd quadrant - beta sheet parallel
Beta sheet anti parallel
Phi
Collagen ( -,+)
3rd quad- Alpha right handed 310 ( -,-)
4th quad- empty( +,-)
D chiral
Diagonally opposite
alpha helix of secondary structure of protein
- hydrogen bond = n to n+4
2) 3.6 amino acid per turn
3) length of each turn =5.4 A
4) right handed conformation
5) h bond btwn amide nitrogen and carbonyl oxygen
6) 13 membered h bond
310 helix
1) H bond = n to n+3
2) 10 membered H bond
3) per turn is 6 A long.
beta sheet antiparallel in secondary structure
- bond angle - 180
- bond strength more, bond strain less hence more stability
