This is an updated and improved version of an earlier well-known and widely-used analysis of the peptide structure by Engh and Huber (1991).1 These geometric parameters were obtained from Cambridge Structural Database (CSD).2 Additional restrains on dihedral angles were found in a separate study from Protein Data Bank (PDB).3
Bond lengths angles are given in angstroms and degrees respectively. Each value is followed by its standard deviation in parentheses on the scale of the least significant digit.
| Peptide (1165) | Proline (297) | Glycine (83) | |
| Lengths | |||
| N-CA | 1.459 (20) | 1.468 (17) | 1.456 (15) |
| CA-C | 1.525 (26) | 1.524 (20) | 1.514 (16) |
| C=0 | 1.229 (19) | 1.228 (20) | 1.232 (16) |
| CA-CB (all) | 1.532 (31) | 1.531 (20) | |
| CA-CB (CH3) | 1.521 (33) | ||
| CA-CB (CH2) | 1.535 (22) | 1.531 (20) | |
| CA-CB (CH) | 1.542 (23) | ||
| C-N | 1.336 (23) | 1.338 (19) | 1.326 (18) |
| Angles | |||
| N-CA-C | 111.0 (27) | 112.1 (26) | 113.1 (25) |
| N-CA-CB (all) | 110.6 (21) | 103.1 (12) | |
| N-CA-CB (CH3) | 110.4 (15) | ||
| N-CA-CB (CH2) | 110.6 (18) | 103.1 (12) | |
| N-CA-CB (CH) | 111.1 (23) | ||
| CA-C-N | 117.2 (22) | 117.1 (28) | 116.2 (20) |
| CA-C=O | 120.1 (21) | 120.2 (24) | 120.6 (18) |
| O=C-N | 122.7 (16) | 121.1 (19) | 123.2 (17) |
| C-CA-CB (all) | 110.6 (23) | 111.8 (20) | |
| C-CA-CB (CH3) | 110.5 (15) | ||
| C-CA-CB (CH2) | 110.4 (20) | 111.8 (20) | |
| C-CA-CB (CH) | 111.3 (20) | ||
| C-N-CA | 121.7 (25) | 122.0 (42) 119.3 (15) trans 127.0 (24) cis | 122.3 (21) |
| Dihedrals | |||
| C-N-CA-C (φ) | -64.2 (100) -58.9 (73) up -69.8 (93) down | ||
| φ + ψ | -130.0 () π-helix -105.0 () α-helix -75.0 () 310-helix | ||
| CA-C-N-CA (ω) |
179.3 (62) trans 0.5 (62) cis |