Parikh Sanjai J, Chorover Jon
Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716, United States.
Colloids Surf B Biointerfaces. 2008 Apr 1;62(2):188-98. doi: 10.1016/j.colsurfb.2007.10.002. Epub 2007 Oct 5.
Lipopolysaccharides (LPS) are ubiquitous in natural aqueous systems because of bacterial cell turnover and lysis. LPS sorption and conformation at the mineral/water interface are strongly influenced by both solution and surface chemistry. In this study, the interaction of LPS with various surfaces (ZnSe, GeO(2), alpha-Fe(2)O(3), alpha-Al(2)O(3)) that vary in surface charge and hydrophobicity was investigated using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The presence of Ca(2+) (versus Na(+)) in LPS solutions resulted in aggregate reorientation and increased sorptive retention. ATR-FTIR spectra of Na-LPS systems are consistent with reduced surface affinity and are similar to those of solution phase LPS. Ca-LPS spectra reveal hydrophobic interactions of the lipid A region at the ZnSe internal reflection element (IRE). However, pH-dependent charge controls Ca-LPS sorption to hydrophilic surfaces (GeO(2), alpha-Fe(2)O(3), and alpha-Al(2)O(3)), where bonding occurs principally via O-antigen functional groups. As a result of accumulation at the solid-liquid interface, spectra of Ca-LPS represent primarily surface-bound LPS. Variable-angle ATR-FTIR spectra of Ca-LPS systems show depth-dependent trends that occur at the spatial scale of LPS aggregates, consistent with the formation of vesicular structures.
由于细菌细胞的更新和裂解，脂多糖（LPS）在天然水系统中普遍存在。LPS在矿物/水界面的吸附和构象受到溶液和表面化学的强烈影响。在本研究中，使用衰减全反射傅里叶变换红外（ATR-FTIR）光谱研究了LPS与各种表面电荷和疏水性不同的表面（ZnSe、GeO₂、α-Fe₂O₃、α-Al₂O₃）之间的相互作用。LPS溶液中Ca²⁺（相对于Na⁺）的存在导致聚集体重新定向并增加吸附保留。Na-LPS系统的ATR-FTIR光谱与表面亲和力降低一致，并且与溶液相LPS的光谱相似。Ca-LPS光谱揭示了脂质A区域在ZnSe内反射元件（IRE）处的疏水相互作用。然而，pH依赖性电荷控制Ca-LPS对亲水性表面（GeO₂、α-Fe₂O₃和α-Al₂O₃）的吸附，其中键合主要通过O抗原官能团发生。由于在固液界面处的积累，Ca-LPS的光谱主要代表表面结合的LPS。Ca-LPS系统的可变角度ATR-FTIR光谱显示出在LPS聚集体的空间尺度上发生的深度依赖性趋势，这与囊泡结构的形成一致。
