Table 4. Geometrical parameters of the imidazole moiety of histidine proposed as revised restraint target values and their standard uncertainties, based on statistical analysis of the CSD version 5.35.
The EH99 values are also included for comparison.
| CSD | CSD | CSD | EH99 | EH99 | EH99 | |
|---|---|---|---|---|---|---|
| Only ND1 protonated | Only NE2 protonated | ND1 and NE2 protonated | Only ND1 protonated | Only NE2 protonated | ND1 and NE2 protonated | |
| Bonds () | ||||||
| CGND1 | 1.371 (9) | 1.382 (9) | 1.379 (7) | 1.369 (15) | 1.383 (22) | 1.380 (10) |
| ND1CE1 | 1.338 (8) | 1.320 (8) | 1.325 (8) | 1.343 (25) | 1.323 (15) | 1.326 (10) |
| CE1NE2 | 1.316 (9) | 1.335 (14) | 1.316 (9) | 1.322 (23) | 1.333 (19) | 1.317 (11) |
| NE2CD2 | 1.377 (7) | 1.367 (9) | 1.373 (7) | 1.415 (21)† | 1.375 (22) | 1.373 (11) |
| CD2CG | 1.356 (9) | 1.359 (10) | 1.353 (7) | 1.353 (17) | 1.353 (14) | 1.354 (9) |
| CBCG | 1.477 (19) | 1.481 (22) | 1.490 (11) | 1.492 (16) | 1.495 (18) | 1.492 (10) |
| Angles () | ||||||
| ND1CGCD2 | 105.1 (5) | 109.1 (8) | 105.9 (5) | 106.0 (14) | 109.2 (7) | 106.1 (8) |
| CGND1CE1 | 108.1 (5) | 105.3 (9) | 109.3 (5) | 108.2 (14) | 105.7 (13) | 109.0 (10) |
| ND1CE1NE2 | 111.3 (6) | 111.9 (10) | 108.4 (5) | 109.9 (22) | 111.5 (13) | 108.5 (11) |
| CE1NE2CD2 | 105.3 (6) | 107.2 (8) | 108.9 (6) | 106.6 (25) | 107.1 (11) | 109.0 (7) |
| NE2CD2CG | 110.3 (6) | 106.5 (7) | 107.4 (5) | 109.2 (19) | 106.7 (12) | 107.3 (7) |
| CBCGND1 | 123.4 (16) | 121.6 (13) | 122.7 (12) | 123.2 (25) | 121.4 (13) | 122.5 (13) |
| CBCGCD2 | 131.5 (16) | 129.3 (14) | 131.3 (13) | 130.8 (31) | 129.7 (16) | 131.4 (13) |
†
This value seems to be in error. The corrected value for the EH99 NE2CD2 bond length is 1.372.