Table 3.

¹H chemical shifts of histidines calculated using Case software^aand coordinates from X-ray crystal structure 2ST1.pdb^b

Histidine	pH	Cɛ1H (ppm)c	Cδ2H (ppm)c	Cɛ1H-Cδ2H (Δ ppm)c
His 17	5.5	7.77	7.20	0.57
His 39	5.5	7.61	6.87	0.74
His 67	5.5	7.68	6.38	1.30
His 226	5.5	7.61	6.83	0.78
His 238	5.5	8.37	6.38	1.99
	10.5	7.53	6.04	1.49
His 64 (active site)	5.5	8.93	7.07	1.86
	10.5	8.09	6.72	1.37

^a FORTRAN program called SHIFTS available from the David A. Case Web site (Osapay and Case 1991).

^bBott et al. (1988).

^c Haigh-Mallion ring current model.