Table 1. Energetics and structural parameters for the lowest-energy conformers of bradykinin protomers.

N-ter			C-ter			PA	GB	IR	SB	sHB	iHB	HB
= 0
0	+	0	−	0	380	409	368	2	1	2	5	1
0	0	+	−	10	380	409	368	2	1	2	4	3
+	0	0	−	49	542	535	540	2	1	1	5	0
0	0	0	0	57	0	0	0	0	0	0	0	4
= 1+
0	+	+	−	0	380	409	368	3	2	3	2	0
0	+	0	0	46	0	0	0	1	0	0	3	4
0	0	+	0	63	0	0	0	1	0	0	4	1
+	0	+	−	67	542	535	540	3	2	2	2	3
+	+	0	−	112	542	535	540	3	1	2	4	0
+	0	0	0	152	162	126	172	1	0	0	3	3
= 2+
+	+	+	−	0	542	535	540	4	3	4	3	1
0	+	+	0	77	0	0	0	2	0	0	6	1
+	+	0	0	85	162	126	172	2	0	0	5	1
+	0	+	0	93	162	126	172	2	0	0	5	2

In each row the following information is reported: protonation pattern (first column); energy difference with respect to the most stable protomer ( in kJ/mol); (intrinsic) internal energy variation (), proton affinity (PA) and gas-phase basicity (GPB) relative to the most favourable protomer (see text for a definition of these quantities; all values are in kJ/mol); ionized residues (IR); salt-bridges (SB); hydrogen bonds between salt-bridged residues (sHB); ionized hydrogen bonds where either the donor or the acceptor is ionized, A or D H-bonds (iHB); neutral hydrogen bonds (HB). Hydrogen bonds are identified according to the donor-acceptor () distance and the donor-acceptor H-bond angle (). The following geometric criterion was adopted: Å and . A salt-bridge is formed if the distance between any oxygen atom of the acidic residue and any protonable nitrogen atom of the basic residue is less than 4.0 Å.