Four Distances between Pairs of Amino Acids Provide a Precise Description of their Interaction
Figure 4
Asymmetry in 4-D distribution of His, Ile, Phe, Glu, Leu, and Pro residues.
Only cases with correct IUPAC atom name assignment protocol were considered. (A) The NE2–NE2 distance of the His-His pair has a higher occupancy around 3.5 Å compared to the ND1–ND1 distance. (B) The CD1–CG2 distance of the Ile-Ile pair has a higher occupancy around 4 Å compared to the CG2–CG2 distance. (C) The CE1–CE2 distance of the Phe-Phe pair has a higher occupancy at around 4 Å compared to the CE1–CE1 distance. The CD atom that makes the smaller torsion angle is named CD1 (see inset). (D) The OE1–CD distance between Glu and Pro has a higher occupancy at the 3–4 Å interval compared to the OE2–CD distance. (E) The CD1–CD1 distance of Leu-Leu has a higher occupancy at around 4 Å compared to the CD2–CD2 distance. (F) The CD1–CD1 distance of the Pro-Pro pair has a higher occupancy at around 4 Å compared to the CD2–CD2 distance.