Trivalent actinides such as Cm(III) are able to occupy natural Ca(II) binding sites in biological systems. For this investigation, we studied the formation of aqueous Cm(III) complexes with S-layer proteins by time-resolved laser-induced fluorescence spectroscopy (TRLFS). S-layer proteins serve as protective biointerfaces in bacteria and archaea against the surrounding solution. Experimental assays were performed at a fixed total concentration of Cm(III) (0.88 μM) using an S-layer protein (5 g/L / 39.6 μM) at varying pH levels (2.0-9.0), as well as several types of S-layer proteins of L. sphaericus JG-A12. Based on resulting luminescence spectra and lifetime data, specific and unspecific binding sites could be distinguished. Notably, specific Cm(III) binding to S-layer proteins was confirmed by the appearance of a sharp emission band at 602.5 nm, combined with a long lifetime of 310 μs. The high affinity of these specific binding sites was also verified using competing EDTA, wherein only a high EDTA concentration (40 μM) could efficiently remove Cm(III) from S-layer proteins.

中文翻译：

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ium（III）与球形芽孢杆菌JG-A12的表面层蛋白的相互作用。

三价act系元素（例如Cm（III））能够占据生物系统中的天然Ca（II）结合位点。为了进行这项研究，我们研究了时间分辨的激光诱导荧光光谱法（TRLFS）与S层蛋白形成的Cm（III）水溶液的形成。S层蛋白可作为细菌和古细菌对抗周围溶液的保护性生物界面。使用固定在Cm（III）总浓度（0.88μM）下的S-层蛋白（5 g / L / 39.6μM）在不同的pH值（2.0-9.0）以及几种类型的S上进行实验分析球形乳杆菌JG-A12的层蛋白。基于所得的发光光谱和寿命数据，可以区分特异性和非特异性结合位点。值得注意的是，通过在602.5 nm处出现清晰的发射带，证实了与S层蛋白结合的特定Cm（III），结合了310μs的长寿命。还使用竞争性EDTA验证了这些特异性结合位点的高亲和力，其中只有高EDTA浓度（40μM）才能有效地从S层蛋白中去除Cm（III）。