Table 1:

Statistics^a of pK_a databases PKAD-2 and PKAD-3

	PKAD-2b			PKAD-3			% incr.
	Res	pKa’s	PDBs	Res	pKa’s	PDBs	Res	pKa’s	PDBs
Asp	175	214	403	291	330	520	66.3%	54.2%	29.0%
Glu	218	258	447	342	382	580	56.9%	48.1%	29.8%
His	116	170	243	155	219	293	33.6%	28.8%	20.6%
Cys	20	20	20	57	60	62	185.0%	200%	210%
Tyr	19	20	22	38	39	41	100.0%	95.0%	86.4%
Lys	67	81	151	109	137	216	62.7%	69.1%	43.0%
Total	615	763		992	1167		61.3%	52.9%
Entries			1286			1712			33.1%
Proteins			113			247			118.6%

^aThe number of unique residues, the number of measured pK_a’s, the number of PDB entries (X-ray structures), and the number of unique wild-type or mutant proteins. The number of PDBs includes several modeled structures for mutant proteins.

^bA cleaned-up version of PKAD-2,²⁰ where pK_a’s given in ranges were removed and errors were corrected (see Methods).