Table 2.

Calculated SORCI+Q Vertical Excitation Energies (λ) in nm, Oscillator (f) and Rotatory (R) Strengths in au of the WT, DM, SBR^cip, and SBR^cidp Chromophores in Gas-Phase (gp) and Protein Environments^a,^b

structure	excited states	Excited-State Properties of Squid Rhodopsin
		gas phase			protein
		λ	f	R	λ	f	R
WT	S1	604	0.93	0.16	490	1.14	0.32
	S2	429	0.30	0.48	393	0.14	0.16
N87‡	S1				510	1.10	0.32
	S2				397	0.17	0.20
Y111‡	S1				501	1.12	0.31
	S2				395	0.15	0.18
E180‡	S1				591	0.98	0.17
	S2				422	0.29	0.42
DM	S1	577	1.06	-0.08	471	1.22	0.07
	S2	425	0.16	0.16	392	0.05	0.04
N87┴	S1				504	1.15	0.00
	S2				402	0.11	0.09
Y111┴	S1				478	1.19	0.03
	S2				394	0.09	0.07
E180┴	S1				551	1.10	-0.01
	S2				419	0.14	0.11
SBRcip	S1	318	1.50	0.22	335	0.00	0.00
	S2	326	0.05	0.02	314	1.59	0.31
N87¶	S1				335	0.02	0.01
	S2				319	1.56	0.32
Y111¶	S1				334	0.01	0.01
	S2				315	1.58	0.32
E180¶	S1				323	1.51	0.29
	S2				334	0.05	0.02
SBRcidp	S1	322	1.52	0.32	333	0.00	0.00
	S2	333	0.05	0.03	313	1.58	0.34
N87#	S1				332	0.00	0.01
	S2				313	1.53	0.28
Y111#	S1				333	0.02	0.00
	S2				313	1.57	0.32
E180#	S1				327	1.47	0.29
	S2				332	0.07	0.03

^aCharges of N87, Y111, and E180 are turned off, one at a time, in the corresponding ^‡WT, ^┴DM, ^¶SBR^cip, and ^#SBR^cidp QM/MM calculations.

^bcipCounterion Glu180 is protonated (charge = 0). ^cidpCounterion Glu180 is deprotonated (charge = −1). The properties of the optically allowed transition are given in bold.