铽(Ⅲ)与PvdA作用的光谱研究

Pyoverdine A(PvdA)是荧光假单胞菌分泌的一种水溶性较高的黄绿色荧光铁载体。在50 mmol·L-1Tris-HCl,pH 8.0条件下,使用紫外-可见吸收差光谱、荧光光谱研究了铽(Ⅲ)与荧光铁载体PvdA的结合。结果表明铽(Ⅲ)可与PvdA结合形成1:1的配合物,条件结合常数为(4.44±0.82)×1014mol-1·L。在生理条件下,PvdA可竞争伴清蛋白N-,C-端结合的铽(Ⅲ)形成Tb-PvdA配合物;Tb-PvdA与荧光假单胞菌细胞表面受体FpvA结合形成Tb-PvdA-FpvA复合物。

Spectroscopic Studies on the Binding of Terbium to PvdA

PvdAis a siderophore, secreted by Pseudomonas aeruginosa in order to get access to iron. PvdA in₅₀ mmol·L^-1 Tris-HCl, pH8.0 was titrated with acidic solutions of Tb³⁺ and the binding of Tb³⁺ to PvdA was followed from changes both in the difference UV-Vis spectra at 380 nm and in fluorescence at 457 nm. The 1:1 stable complex of Tb-PvdA can be confirmed from spectral titration curves. Using EDTAas a competitor the conditional binding constant of the complex was measured to be (4.44±0.82)×10¹⁴ mol^-1·L. The formed Tb-PvdA from the reaction between PvdA and Tb³⁺ saturated ovotansferrin can be followed by measuring the fluorescence emission of Tb³⁺ at 548 nm, demonstrating that the binding of PvdA for Tb³⁺ is stronger than that of apoovotransferrin. Furthermore, Tb-PvdA interaction with the PvdA-Fe outer membrane transporter, FpvA, of Pseudomonas aeruginosa could be followed by fluorescence resonance energy transfer between the tryptophans of FpvA (donor) and PvdA (acceptor).