Table 1. Medians of the B factors scaled by the unity-based algorithm (1) and the numbers of amino acids, nucleotides and water residues in various environments.

The residues were extracted from the structures of nonredundant protein–DNA complexes with data-collection temperature lower than 180 K sorted into three resolution bins. Bin R1 contains 165 structures with a crystallographic resolution of 1.9 Å or better, bin R2 contains 357 structures with resolution 1.9–2.5 Å and bin R3 contains 187 structures with resolution 2.5–3.0 Å. The median values listed in this table were calculated for the backbone (BB) atoms of the residues. More complete statistics can be found in Supplementary Table S1.

	Resolution ≤1.9 Å		Resolution 1.9–2.5 Å		Resolution 2.5–3.0 Å
Type of residue†	Median‡	Residues§	Median‡	Residues§	Median‡	Residues§
buried aa	14	19085	20	46934	26	33693
exposed aa	32	6531	39	18687	45	15025
partially buried aa	—	26107	—	70042	—	53510
protein–protein aa	21	2202	23	7258	29	5240
protein–symprotein aa	—	2693	—	5799	—	3744
protein–DNA aa	19	2625	23	8147	29	5685
DNA–protein nt	31	1737	35	5726	36	4146
exposed nt	51	2120	54	7676	54	5240
bridge w	28	3370	27	6285	27	1109
surface w	52	10878	44	16360	33	3267

^†Definitions of the residue classes are given in §2.

^‡Median values are listed for the backbone atoms; the medians for the side-chain atoms can be found in Supplementary Table S1.

^§Numbers of residues in the listed classes.