Table 1.

Numbers of S(SSC)···X contacts in selected proteins [17] ^a.

X =	d b ≤ 0.0 Ǻ	0.0 < d ≤ 0.5 Ǻ
O	100	664
N	33	359
S	15	68
C	134	1478
Others	2	0
Total	284	2569

^a 604 heterogeneous proteins with high resolution (≤2 Ǻ) were selected. The total number of Cys residues was 790; ^b A relative nonbonded S···X distance defined as d = r_S···X − vdw_S − vdw_X.