Table 2. MM-PBSA Results Using iAPBS^a.

iAPBS/MM-PBSA results	H72Q-r	std error of mean	A52V S54N K66E	std error of mean	wild type	std error of mean
experimental Kd	5.5 E(−9) M		1.1 E(−8) M		7.6 E(−6) M
no water molecules included	−47.7	3.1	−47.2	0.8	−44.1	1.2
interfacial water molecules (200)	−146.3	4.7	−143.8	14.7	−148.2	3.0
intercalating water molecules	−55.3	2.8	−54.3	0.8	−46.2	1.4

^aAll results are in kcal/mol, except for the experimental K_d data. The internal entropy contributions are not included in these estimates since it was nearly the same for the three cases.