title: Unprotonated chromophore-protein bond in visual pigments from 13C-NMR spectra.
mesh_terms: D000818:Animals; D002247:Carbon Isotopes; D002417:Cattle; D009682:Magnetic Resonance Spectroscopy; D011522:Protons; D012168:Retinal Pigments; D012172:Retinaldehyde; D012243:Rhodopsin; D012545:Schiff Bases; D013329:Structure-Activity Relationship
chemical_list: D002247:Carbon Isotopes; D011522:Protons; D012168:Retinal Pigments; D012545:Schiff Bases; D012243:Rhodopsin; D012172:Retinaldehyde