Table 1. Selection criteria for isoleucines.

Selection parameter	Criterion
Experimental method	X-ray
Structure	Not N-terminal or C-terminal, not next to a terminus and not next to Gly, Pro or a noncanonical residue
Side-chain and backbone atoms	Not mentioned in the WHAT_CHECK (Hooft, Vriend et al., 1996 ▶) quality report calculated with the WHAT IF web service (Hekkelman et al., 2010 ▶)†
B factor, Cβ and backbone atoms	<60.0 Å2 or <2.5 × the average B factor over Cα
DSSP secondary structure	H, E or loop

^†This extensive list of criteria is briefly explained at http://swift.cmbi.ru.nl/gv/isoleucine/. The criteria include, for example, atomic clashes, spurious covalent bonds, missing atoms etc.