title: Quenching of the fluorescence of actin modified at lysine-61.
abstract: The fluorescence of actin modified with fluorescein isothiocyanate at Lys-61 is quenched in the presence of iodide. The approximate second order rate constant for quenching is 9 X 10(-8) M-1 s-1, which approaches that for a diffusion-limited process. However, a measurable degree of protection is provided to the fluorescein group by the protein structure around it. A tryptic digest of the modified actin is more susceptible to quenching than is the native protein. Free fluorescein is even more vulnerable. The addition of deoxyribonuclease I to the modified actin reduces the susceptibility of the fluorescence to quenching by only a small degree.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D016650:Fluorescein-5-isothiocyanate; D005452:Fluoresceins / Q000494:pharmacology*; D005456:Fluorescent Dyes / Q000494:pharmacology*; D007700:Kinetics; D008239:Lysine; D009132:Muscles / Q000378:metabolism; D011817:Rabbits; D013050:Spectrometry, Fluorescence; D013861:Thiocyanates / Q000494:pharmacology*
chemical_list: D000199:Actins; D005452:Fluoresceins; D005456:Fluorescent Dyes; D013861:Thiocyanates; D016650:Fluorescein-5-isothiocyanate; D008239:Lysine