Table 1 Values and meanings of block function parameters for identification of protein–ligand interaction features
Term | Meaning | Value | ||
|---|---|---|---|---|
Hydrogen bond | Interaction with heme–iron | |||
C19–OH or = O | Azaheterocycle | |||
H···A distance parameters (Å) | ||||
r | The ideal H···A distance | 2.00 | 2.40 | 2.25 |
Δr ideal | The tolerance window around r, with in which the hydrogen bond is regarded as ideal | 0.50 | 0.25 | 0.25 |
Δr max | The maximum possible deviation from r; above this, the interaction is not regarded as a hydrogen bond | 0.65 | 0.65 | 0.65 |
D–H···A angle parameters (°) | ||||
α | The ideal D–H···A angle | 180 | 180 | 180 |
Δα ideal | The tolerance window around α, with in which the hydrogen bond is regarded as ideal | 45 | 10 | 20 |
Δα max | The maximum possible deviation from α; above this, the interaction is not regarded as a hydrogen bond | 80 | 40 | 40 |
DH···A–X angle parameters (°) | ||||
β | The ideal DH···A–X angle | 180 | 180 | 180 |
Δβ ideal | The tolerance window around β, with in which the hydrogen bond is regarded as ideal | 80 | 80 | 60 |
Δβ max | The maximum possible deviation from β; above this, the interaction is not regarded as a hydrogen bond | 100 | 100 | 100 |