Table 1.

Tautomers, torsion angles, and isotropic chemical shifts of the His37 tetrad in D1–D4^a

	D1	D2	D2′	D3	D4
Tauto-	τ/τ	Im+/Im+	π/π	Im+/Im+	Im+/Im+
mer	Im+/Im+	τ/τ	Im+/Im+	τ/Im+	τ/Im+
χ1 (°)	−170/−165	−173/−170	−167/−168	−165/−178	−166/−179
	−168/−161	−164/−165	−164/−166	−163/179	−164/−177
χ2	−178/−165	−7/−8	−10/−9	−11/64	−9/56
	175/170	−100/−93	−95/−93	−91/−135	−88/−158
Cα (ppm)64/64		64/63	64/63	64/69	64/67
	63/64	74/74	74/74	75/66	74/64
Cγ	40/40	39/35	40/37	36/33	36/32
	39/36	39/39	36/37	40/38	40/38
Cβ	146/146	136/139	134/135	140/141	140/139
	139/142	148/148	143/141	148/140	147/139
Cδ2	125/125	125/128	131/128	130/125	129/120
	123/127	119/121	120/120	123/132	124/132
Cε1	139/139	144/137	140/138	136/148	138/145
	140/138	143/141	144/140	143/130	143/132
Nδ1b	−/−	146/146	144/145	149/148	149/149
	159/157	−/−	169/170	−/157	−/154
Nε2	149/148	167/168	−/−	162/156	167/159
	157/149	151/152	153/153	154/153	153/158

^aIn each entry, the first two tautomers or numbers refer to those for chains A and C, and the last two refer to those for chains B and D.

^bThe linear scaling relation for nitrogen chemical shifts were obtained using only nuclei covalently bonded to a hydrogen. For N not covalently bonded to a hydrogen, no reliable results were available.