Table 1. Statistics of hydrogen bonds in proteins.

mc: main chain; sc: side chain; aa: amino acid; ×2: two molecules in asymmetric unit. Values in parenthesis are standard deviations.

	DsrD	Other 16 proteins
Number of hydrogen bonds
mc–mc	92
mc–sc	15
sc–sc	4
Ratio of hydrogen bonds (%)
mc–mc	82.9	68.3 (6.9)
mc–sc	13.5	23.5 (6.1)
sc–sc	3.6	8.2 (4.1)
Hydrogen bonds per aa	0.84†	1.05 (0.15)

^†25 residues missing in the neutron structure were excluded from the calculation.