Table 1. Summary of structural properties and relative free energies for selected calculated structures.

	m/z	His tautomer	Radical	Rel. ΔG (kJ mol−1)
[AAHAR+2H+]2+	263
I		—	—	+10.8*
II		—	—	0.0
z1·+	159
I		—	α	+5.4*
II		—	δ (Arg)	0.0
III		—	β (Arg)	+10.1
IV		—	γ (Arg)	+14.7
z2·+	230
I		—	α	0.0*
II		—	α	+10.2
III		—	δ (Arg)	+26.5
z3·+	367
I		N3	α	+22.4*
II		N1	α	0.0
III		N3	β (His)	0.0
z4·+	438
I		N3	α	0.0*
II		N3	α	+62.5
III		N3	—	+54.4
IV		N3	β (His)	+5.7
z3+	368
I		N1	—	+28.5*
c4_I		—	—	—
II		N3	—	0.0

Rel., relative.

An asterisk (*) indicates the structure assigned spectroscopically.