Table 1

Definition of ionic and polar interactions utilized in PIADA. Protein interaction partners used in the PIADA algorithm for the definition of ionic and polar interactions. The hydrogen bonds are included in the latter, but due to the lack of information about directionality they are not explicitly specified.

Interaction type
Defined distance
Proton donors
Proton acceptors

Ionic
< 6Å
Lys N(NH3+)
Arg N(NH2+)
terminal N(NH3+)
Asp O(COO-)
Glu O(COO-), terminal O (COO-)
Polar Group I
< 4.7Å
Asn N(H2)
Cys S(H)
Gln N(H2)
His N(H)
Ser O(H)
Thr O(H)
Trp N(H)
Tyr O(H)
N backbone
Asp O(COO-)
Glu O(COO-)
Polar Group II
< 4.7Å
Lys N(NH3+)
Arg N(NH2+)
Asn O (C=O)
Cys S(H)
Gln O(C=O)
His N
Ser O(H)
Thr O(H)
Tyr O(H)
O backbone
Polar Group III
< 4.7Å
Asn N(H2)
Cys S(H)
Gln N(H2)
His N(H)
Ser O(H)
Thr O(H)
Trp N(H)
Tyr O(H)
N backbone
Asn O(C=O)
Cys S(H)
Gln O(C=O)
His N
Ser O(H)
Thr O(H)
Tyr O(H)
O backbone

Mihel et al. BMC Structural Biology 2008 8:21   doi:10.1186/1472-6807-8-21