Coordination of uranium(VI) with functional groups of bacterial lipopolysaccharide studied by EXAFS and FT-IR spectroscopy
Coordination of uranium(VI) with functional groups of bacterial lipopolysaccharide studied by EXAFS and FT-IR spectroscopy
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DOI：
10.1039/c1dt10546a
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发表时间：
2011-01-01
影响因子：
4
通讯作者：
Bernhard, Gert
中科院分区：
文献类型：
--
作者：
Barkleit, Astrid;Foerstendorf, Harald;Bernhard, Gert
利用扩展X射线吸收精细结构（EXAFS）和衰减全反射傅里叶变换红外光谱（ATR-FT-IR）技术，在较宽的pH范围内（2.6 ~ 7.0），从分子水平上研究了铀酰离子与革兰氏阴性菌细胞壁主要成分脂多糖（LPS）的络合作用。第一次，与细胞壁化合物的铀酰配合物的结构测定从酸性扩展到中性pH值。负责铀酰结合的主要功能是磷酰基和羧基。在过量的LPS，有关的环境条件下，铀酰离子主要是络合的磷酰基四倍单齿协调在赤道平面的铀酰二氧阳离子UO 22+表现出很大的同源性的铀酰矿物相偏钙铀石的EXAFS光谱。在铀酰和LPS官能团的等摩尔比下，根据磷酰基的轻微缺乏，如红外光谱所示，以双齿方式进行额外的羧基配位变得重要。从振动光谱，一个混合的协调UO 22+与磷酰基和羧基的衍生。铀酰离子与LPS分子的配位主要受U/LPS浓度比的控制，pH值的影响在研究范围内并不显著。
The complexation of uranyl ions with lipopolysaccharide (LPS), the main component of the cell wall of Gram-negative bacteria, was investigated on a molecular level with U L-III-edge extended X-ray absorption fine structure (EXAFS) and attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopy over a wide pH range (2.6 to 7.0). For the first time, structural determinations of uranyl complexes with cell wall compounds were extended from acidic up to neutral pH. The main functionalities responsible for uranyl binding are phosphoryl and carboxyl groups. At an excess of LPS, related to environmental conditions, the uranyl ion is mainly complexed by phosphoryl groups four-fold monodentately coordinated in the equatorial plane of the uranyl dioxo cation UO22+ showing great homologies to the uranyl mineral phase meta-autunite in the EXAFS spectra. At equimolar ratios of uranyl and functional groups of LPS, according to a slight deficit of phosphoryl groups, additional carboxyl coordination in a bidentate manner becomes important as it is shown by IR spectroscopy. From the vibrational spectra, a mixed coordination of UO22+ with both phosphoryl and carboxyl groups is derived. The coordination of uranyl ions to the LPS molecule is obviously mainly controlled by the U/LPS concentration ratio, and the influence of pH is only of minor significance at the investigated range.