On-Cell MAS NMR: Physiological Clues from Living Cells

While structural information on biomolecules is mainly obtained from purified in vitro samples, NMR can also be applied in the context of entire cells or organisms. The present study describes maturation processes in living <i>Salmonella enterica</i> serovar Typhimurium, a prevalent cause for human gastroenteritis. In our physiological study, we follow the composition of the O-antigen on the outer bacterial membrane with high-resolution MAS NMR spectroscopy. We detect and characterize an evolution of the O-antigen composition, in particular of the O-acetylation state of the O-antigen, a factor that can play an important role in vaccine development

Supported Lipopolysaccharide Bilayers

In this report, the formation of supported lipopolysaccharide bilayers (LPS-SLBs) is studied with extracted native and glycoengineered LPS from Escherichia coli (E. coli) and Salmonella enterica sv typhimurium (S. typhimurium) to assemble a platform that allows measurement of LPS membrane structure and the detection of membrane tethered saccharide-protein interactions. We present quartz crystal microbalance with dissipation monitoring (QCM-D) and fluorescence recovery after photobleaching (FRAP) characterization of LPS-SLBs with different LPS species, having, for example, different molecular weights, that show successful formation of SLBs through vesicle fusion on SiO₂ surfaces with LPS fractions up to 50 wt %. The thickness of the LPS bilayers were investigated with AFM force–distance measurements which showed only a slight thickness increase compared to pure POPC SLBs. The E. coli LPS were chosen to study the saccharide–protein interaction between the Htype II glycan epitope and the Ralstonia solanacearum lectin (RSL). RSL specifically recognizes fucose sugars, which are present in the used Htype II glycan epitope and absent in the epitopes LPS1 and EY2. We show via fluorescence microscopy that the specific, but weak and multivalent interaction can be detected and discriminated on the LPS-SLB platform