title: Tryptophan fluorescence quenching by alkaline earth metal cations in deionized bacteriorhodopsin.
abstract: Tryptophan quenching by the addition of alkaline earth metal cations to deionized bacteriorhodopsin suspensions was determined. The results show that the addition of cation primarily quenches fluorescence from surface tryptophan residues. The quenched intensity exhibits a 1/R dependence, where R is the ionic radius of the corresponding metal ion. This observation results from a stronger energy transfer coupling between the tryptophan and the retinal. The membrane curvature may be involved as a result of cations motion and correlated conformational changes.
authors.affiliation: Institute of Biophysics, Academia Sinica, Beijing, China.
authors.forename: G
authors.initials: G
authors.lastname: Wang
authors.forename: A J
authors.initials: AJ
authors.lastname: Wang
authors.forename: K S
authors.initials: KS
authors.lastname: Hu
mesh_terms: D001436:Bacteriorhodopsins / Q000737:chemistry*; D017609:Barium Compounds / Q000737:chemistry; D002122:Calcium Chloride / Q000737:chemistry; D002413:Cations, Divalent; D002712:Chlorides / Q000737:chemistry; D005453:Fluorescence; D019617:Halobacterium salinarum / Q000737:chemistry; D015636:Magnesium Chloride / Q000737:chemistry; D008673:Metals, Alkaline Earth / Q000737:chemistry*; D018717:Purple Membrane / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013324:Strontium / Q000737:chemistry; D014364:Tryptophan / Q000737:chemistry*
chemical_list: D017609:Barium Compounds; D002413:Cations, Divalent; D002712:Chlorides; D008673:Metals, Alkaline Earth; D015636:Magnesium Chloride; C024986:barium chloride; D001436:Bacteriorhodopsins; D014364:Tryptophan; C025700:strontium chloride; D002122:Calcium Chloride; D013324:Strontium