Dittrich Maria, Sibler Sabine
Swiss Federal Institute of Aquatic Science and Technology, Eawag, Switzerland.
Langmuir. 2006 Jun 6;22(12):5435-42. doi: 10.1021/la0531143.
The chemistry of the surface functional groups of picocyanobacteria Synechococcus PCC 7942 cells was examined as a function of H+ and calcium concentrations. Titration experiments, infrared spectroscopy, biosorption experiments, and chemical modeling were used to gain insight into the mechanisms of biosorption. The pKa and concentration of active sites on the cell wall were clarified with the aid of potentiometric titration. Modeling calculations and infrared spectra are consistent with pKa's values of 4.3, 5.2, 6.9, 9.1, and 10.0 and a total concentration of 7.8 x 10(-4) mol g(-1). Spectral analysis of an aqueous cellular suspension revealed a presence of carboxyl, amide, phosphate, hydroxyl, and carbohydrate moieties. Correspondence between spectral data and potentiometric titration curves supported the hypothesis that carboxylate groups and phosphodiester groups mediate calcium adsorption to bacterial cells. This process is strongly pH dependent. In the second part of the experimental work, Synechococcus cells were suspended in the presence of different calcium concentrations. Mechanistic modeling demonstrated that the calcium adsorption phenomenon can be described taking into account only two mechanisms: ion exchange and complexation.
研究了聚球藻属蓝细菌聚球藻PCC 7942细胞表面官能团的化学性质随H⁺和钙浓度的变化情况。采用滴定实验、红外光谱、生物吸附实验和化学建模来深入了解生物吸附机制。借助电位滴定法明确了细胞壁上活性位点的pKa值和浓度。建模计算和红外光谱与pKa值4.3、5.2、6.9、9.1和10.0以及总浓度7.8×10⁻⁴ mol g⁻¹一致。对细胞水悬浮液的光谱分析表明存在羧基、酰胺基、磷酸基、羟基和碳水化合物部分。光谱数据与电位滴定曲线之间的对应关系支持了羧酸盐基团和磷酸二酯基团介导钙吸附到细菌细胞上的假设。这个过程强烈依赖于pH值。在实验工作的第二部分，将聚球藻细胞悬浮在不同钙浓度的环境中。机理建模表明，仅考虑离子交换和络合这两种机制就可以描述钙吸附现象。
