Page 76 - Color Atlas of Biochemistry

Peptides and Proteins 67

A. Peptide bonds B. Resonance

H H
C N
C N
O
O
Resonance
structures
H
H
C N
C N
O
O
ϕ ψ

H
H
C N C N
O
Seryl alanine O
(Ser-Ala, H N-Ser-Ala-COO , SA) Mesomeric
3
structure
C. Peptide nomenclature
Residue 1 Residue 2 Residue 3 Residue 4 Residue

R 1 H O R 3 H O R n
Amino H H Carboxy-
terminus C N C C N C C terminus
(N terminus) H N C C N C C N COO (C terminus)
3
H H H
O R 2 H O R 4 H
D. Conformation space of the peptide chain

ϕ = 0°
3 ψ = 180°
R ϕ (Phi): Rotation about ϕ
j (Phi): N – C α 2 R
ϕ ψ (Psi): Rotation about
2 ψ y (Psi): C α – C ψ
3
ϕ = -139° 180 1
1 ψ = -135° B-23
β a C
2. 120 β p d = 115 pm 4.

60
α l
Allowed Forbidden
ψ 0

α r ϕ = 180° 3
-60 ψ = 0°
ϕ = -57°
ψ = -47° R
-120 d =
ϕ A-9 B-20 155 pm
2 ψ B-8 R ψ
2
ϕ
-180 -120 -60 0 60 120 180
1. ϕ
1
3
1
3. α r Pleated sheet (antiparallel) β a α Helix (right-handed) 5.
α l Pleated sheet (parallel) β p α Helix (left-handed) C Collagen helix

Koolman, Color Atlas of Biochemistry, 2nd edition © 2005 Thieme
All rights reserved. Usage subject to terms and conditions of license.