Table 4.

A summary of residue–base contact features.

Type
Residue	Base	Context len.	# of Features
Residues	Bases	3	${20}^3\times 4^3$
		5	${20}^5\times 4^5$
Secondary structures	Secondary structures	3	$8^3\times 6^3$
		5	$8^5\times 6^5$
Simplified alphabets (10 groups)	Bases	3	${10}^3\times 4^3$
		5	${10}^5\times 4^5$
Simplified alphabets (10 groups)	Secondary structures	3	${10}^3\times 6^3$
		5	${10}^5\times 6^5$
Simplified alphabets (4 groups)	Bases	3	$4^3\times 4^3$
		5	$4^5\times 4^5$
Simplified alphabets (4 groups)	Secondary structures	3	$4^3\times 6^3$
		5	$4^5\times 6^5$