Table 4. Percentage frequencies (with normalized propensity values in parentheses) of apolar, polar and other atomic contacts of PP complexes from the ABC and PIBASE datasets.

		PP complexes
		ABC dataset	PIBASE dataset
Apolar contacts:	C…C	44.08 (1.10)	44.20 (1.10)
	C…S	0.85 (2.53)	0.57 (1.91)
	S…C	0.56 (1.82)	0.47 (1.63)
	S…S (not in Cys-Cys bridge)	0.03 (10.94)	0.01 (6.60)
	Total	45.52	45.25
Polar contacts:	N…O	2.85 (0.91)	2.83 (0.90)
	O…N	4.48 (1.40)	4.40 (1.40)
	O…O	3.37 (0.70)	3.45 (0.73)
	N…N	2.76 (1.31)	2.70 (1.29)
	O…S	0.16 (1.40)	0.14 (1.38)
	S…O	0.11 (1.05)	0.12 (1.24)
	N…S (from Cys)	0.05 (0.68)	0.02 (0.35)
	S…N (from Cys)	0.07 (0.93)	0.03 (0.50)
	Total	13.85	13.70
Other contacts:	C…N	10.83 (1.19)	10.95 (1.20)
	N…C	8.28 (0.91)	8.12 (0.88)
	C…O	10.42 (0.76)	10.68 (0.78)
	O…C	10.93 (0.78)	11.17 (0.81)
	N…S (S not from Cys)	0.09 (1.14)	0.06 (0.86)
	S…N (S not from Cys)	0.08 (1.08)	0.07 (1.05)
	S…S (in Cys-Cys bridge)	0.002 (0.84)	0.003 (1.39)
	C…P/P…C	0.00 (0.00)	0.00 (0.00)
	C…F/F…C	0.00 (0.00)	0.00 (0.00)
	N…P/P…N	0.00 (0.00)	0.00 (0.00)
	N…F/F…N	0.00 (0.00)	0.00 (0.00)
	O…P/P…O	0.00 (0.00)	0.00 (0.00)
	O…F/F…O	0.00 (0.00)	0.00 (0.00)
	S…P/P…S	0.00 (0.00)	0.00 (0.00)
	S…F/F…S	0.00 (0.00)	0.00 (0.00)
	P…P	0.00 (0.00)	0.00 (0.00)
	P…F/F…P	0.00 (0.00)	0.00 (0.00)
	F…F	0.00 (0.00)	0.00 (0.00)
	Total	40.63	41.05
	Grand Total	100	100

PP, protein-protein.