Table 8. Type of H-bond, β-Bend, and Thermodynamic Properties of Local Minima for the Zwitterionic Leu-EnK Optimized from the Structures Obtained by X-ray Diffraction, MD Simulation, and Molecular Docking at the DSD-PBEP86-D3BJ/def2-TZVP//M06-2X/6-31+G(d) Level of Theory in Water^a.

conf.b	H-bond typec	β-bendd	ΔEwe	ΔHwf	ΔGwg
LENKPH11	1 → 4, 4 → 1	βI′23	5.75	5.22	4.55
GEWWAG	4 → 1, 5 → 2	βI23, βI34	4.61	4.25	4.57
BIXNIF10	ext		14.07	13.95	8.05
FABJEX	ext		14.67	14.25	8.75
MD-AA1	OH1 → 3, 2 → 5		4.58	5.11	5.91
MD-AA2	OH1 → 4		7.71	7.79	3.90
MD-AA3	OH1 → 4, 2 → 5, 3 → 5		3.47	4.08	3.60
Docking1	5 → 3		16.59	16.92	16.14
Docking2	ext		12.66	12.12	8.39
Docking2-c	ext		18.93	15.70	13.22

^aTorsion angles (°) are listed in Table 3.

^bThe definition of conformations are noted in footnotes b–e of Table 7.

^cEach 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.

^dβI₂₃ and βI′₂₃ stand for the type I and I′ β-bend at the Gly2–Gly3 sequence, which are stabilized by the 4 → 1 H-bond. βI₃₄ stands for the type I β-bend at the Gly3–Phe4 sequence, which is stabilized by the 5 → 2 H-bond.

^eRelative electronic energies in kcal mol^–1.

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

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