Table 6. Gain or loss of specific contacts of three different types in all simulations.

Hydrogen bonds (or salt bridges) and hydrophobic interactions between separate monomers (essential to lattice contacts) formed and lost during each simulation were tallied and split into three general categories. First column: salt bridges or hydrogen bonds involving two side chain groups. Second column: salt bridges or hydrogen bonds involving at least one backbone group. Third column: hydrophobic interactions, including the cation-π interaction between Arg62 and Tyr35. All specific contacts originally present in the X-ray structure are listed in Table 5.

Force Field	Water Model	Salt Bridge/Hydrogen Bond (Side Chain)	Salt Bridge/Hydrogen Bond (Backbone)	Hydrophobic
FF99SB	SPC/E	1.6	2.1	−0.4
	TIP3P	2.1	1.5	−0.4
	TIP3P-Ew	2.1	1.7	−0.3
	TIP4P-2005	1.8	2.2	0.0
FF03	SPC/E	1.2	3.5	−0.6
	TIP3P	1.7	3.0	−0.6
	TIP3P-Ew	1.5	3.2	−0.5
	TIP4P-2005	1.0	3.0	−0.4
CHARMM	SPC/E	0.3	0.9	−0.6
	TIP3P	1.0	0.7	−1.3
	TIP3P-Ew	0.8	1.7	−0.9
	TIP4P-2005	0.7	0.1	−1.0
OPLS	SPC/E	2.5	2.6	−1.2
	TIP3P	3.9	3.1	−1.3
	TIP3P-Ew	3.4	4.0	−1.1
	TIP4P-2005	2.6	2.8	−1.1