Table 6. Type of H-bond, β-Bend, Thermodynamic Properties, and Population of 16 Local Minima for the Zwitterionic Leu-EnK Calculated at the DSD-PBEP86-D3BJ/def2-TZVP//SMD M06-2X/6-31+G(d) Level of Theory in Water^a.

conf.	H-bond typeb	β-bendc	ΔEwd	ΔHwe	ΔGwf	wg
zw01	1 → 5, 4 → 1, 5 → 2	βII′23, βI34	0.84	0.61	0.00	48.1
zw02	1 → 4, 1 → 5, 4 → 1	βII′23	1.15	1.39	0.69	15.0
zw03	1 → 4, 1 → 5, 4 → 1	βII′23	1.78	1.74	0.69	15.0
zw04	1 → 5, 4 → 1, 5 → 2	βII′23, βI34	3.66	3.50	1.54	3.6
zw05	OH1 → 5, 5 → 2	βI34	0.00	0.00	1.70	2.8
zw06	OH1 → 5, 5 → 2	βI34	1.16	1.46	1.77	2.4
zw07	1 → 5, 2 → 5, 5 → 2	βII′34	3.49	3.38	1.94	1.8
zw08	OH1 → 3, 2 → 5, 4 → 2		1.65	1.69	1.96	1.8
zw09	OH1 → 3, 2 → 5, 4 → 2		1.71	1.67	2.12	1.4
zw10	OH1 → 3, 2 → 5, 4 → 2		3.34	3.26	2.15	1.3
zw11	OH1 → 5, 5 → 2	βI34	1.25	1.44	2.27	1.1
zw12	OH1 → 3, 2 → 5, 4 → 2		1.75	2.02	2.27	1.0
zw13	OH1 → 5, 2 → 4, 3 → 1		1.55	1.52	2.50	0.7
zw14	OH1 → 3, 2 → 5, 4 → 2		3.05	3.20	2.77	0.5
zw15	OH1 → 3, 2 → 5, 4 → 2		3.35	3.70	2.97	0.3
zw16	OH1 → 5, 5 → 2	βI34	2.37	2.15	2.98	0.3

^aTorsion angles (°) are listed in Table 5. Only 16 local minima with the relative Gibbs free energy (ΔG_w) < 3 kcal mol^–1 are listed.

^bEach H-bond type n → m stands for the H-bond between the H donor (e.g., the amide H atom for backbone) of the residue n and the H acceptor (e.g., the carbonyl O atom for backbone) of the residue m. In addition, OH1 represents the hydroxyl H atom of the side chain of the Tyr1 residue.

^cβII′₂₃ stands for the type II′ β-bend at the Gly2–Gly3 sequence, which are stabilized by the 4 → 1 H-bond. βI₃₄ and βII′₃₄ stand for the type I and II′ β-bend at the Gly3–Phe4 sequence, respectively, which are stabilized by the 5 → 2 H-bond.

^dRelative electronic energies in kcal mol^–1.

^eRelative enthalpies in kcal mol^–1 at 25 °C.

^fRelative Gibbs free energies in kcal mol^–1 at 25 °C and 1 atm.

^gThe population of each conformer was calculated by its ΔG_w at 25 °C.