TABLE 2.

Comparison of S₀ energy and the excitation energy (kcal/mol) of the chromophore in conformations of the native protein and the triple mutant, M118A/S141A/A215T of HsBR (M126A/S149A/A223T of HwBR), calculated at the MRMP2 level of theory in the isolated condition

	Native	Triple mutant	ΔEexa
S0 energy	0.0	−0.4
Excitation energy (Eex)b	46.9	51.3	4.4

^a Difference in the excitation energy between the triple mutant and the native protein.

^b The absolute energy is −949.60270 au.