Updated FTP location. Targeted analysis of retinal-cysteine adduct in Opsin 5 like-1 (Opn5L1) protein Chicken Opn5L1 E177K/Q192K mutant was expressed in HEK293T, regenerated by all-trans-retinal, solubilized by dodecyl maltoside, and purified using Rho1D4 antibody-conjugated Sephalose. Semi-quantitative targeted analyses of trypsinized Opn5L1 with or without light irradiation were carried out using reverse phase LC-ESI-MSn to detect light-dependent formation of retinal-cysteine adduct. The results were analyzed by Mass++, mMass and Igor Pro softwares.