Table I.

Structural Categories, Populations, and Motifs

Structural category	Populationa	Experimentalb	Exhaustivec	% Covered by top sixd
H2S	1402	7	28	99.4
H3S	2947	17	162	84.2
H4S	2343	26	913	74.3
H2H	709	9	32	91.0
H3H	1149	20	183	72.1
H4H	818	32	1053	59.5
S2H	1278	6	27	100.0
S3H	796	30	162	50.5
S4H	1008	37	894	52.9
S2S	2634	5	14	100.0
S3S	1021	17	99	66.2
S4S	2232	23	475	70.2

^aTotal turn population after eliminating those that contributed <0.5% to the population.

^bNumber of experimentally determined unique turns.

^cNumber of conceivable clash-free turns sampling the eight basins.

^dPercentage of the population in col. 2 covered by the top six categories from col. 3.