Burtnick L D
Biochem Int. 1987 Mar;14(3):547-51.
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.
异硫氰酸荧光素修饰的肌动蛋白在赖氨酸-61处的荧光在碘化物存在下会被淬灭。淬灭的近似二级速率常数为9×10⁻⁸ M⁻¹ s⁻¹，这接近扩散限制过程的速率常数。然而，其周围的蛋白质结构为荧光素基团提供了一定程度的保护。修饰后的肌动蛋白经胰蛋白酶消化后比天然蛋白质更容易被淬灭。游离的荧光素甚至更易被淬灭。向修饰后的肌动蛋白中添加脱氧核糖核酸酶I只会使荧光对淬灭的敏感性略有降低。
