Fig. (3) Interatomic distances (D) between different atoms of Glu181 and the PSB nitrogen (a), Ser186 and the PSB nitrogen (b), Glu181 and Ser186 (c), Glu113 and Ser186 (d), Glu113 and Glu181 (e), Glu113 and the PSB nitrogen (f) in wild rhodopsin.