Evaluation of Lipopolysaccharide Aggregation by Light Scattering Spectroscopy

Abstract

Lipopolysaccharides (LPS) are cell wall components of Gram-negative bacteria. These molecules behave as bacterial endotoxins and their release into the bloodstream is a determinant of the development of a wide range of pathologies. These amphipathic molecules can self-aggregate into supramolecular structures with different shapes and sizes. The formation of these structures occurs when the LPS concentration is higher than the apparent critical micelle concentration (CMC(a)). Light scattering spectroscopy (both static and dynamic) was used to directly characterize the aggregation process of LPS from Escherichia coli serotype 026:B6. The results point to a CMC(a) value of 14 microg mL(-1) and the existence of premicelle LPS oligomers below this concentration. Both structures were characterized in terms of molecular weight (5.5 x 10(6) and 16 x 10(6) g mol(-1) below and above the CMC(a), respectively), interaction with the aqueous environment, gyration radius (56 and 105 nm), hydrodynamic radius, (60 and 95 nm) and geometry of the supramolecular structures (nearly spherical). Our data indicates that future in vitro experiments should be carried out both below and above the CMC(a). The search for drugs that interact with the aggregates, and thus change the CMC(a) and condition LPS interactions in the bloodstream, could be a new way to prevent certain bacterial-endotoxin-related pathologies.

A Phage Display Screen and Binding Studies with Acetylated Low Density Lipoprotein Provide Evidence for the Importance of the Scavenger Receptor Cysteine-rich (SRCR) Domain in the Ligand-binding Function of MARCO

“…Of these polyanionic compounds, LPS, LTA, and poly(I) are ligands of scavenger receptor A (19 -22). Both LPS and LTA have a tendency to form micelles in an aqueous environment (16,23,24). As mentioned in the Introduction, we have found previously that sMARCO interacts with LPS in a test tube assay (13).…”

Peptide hydrogel in vitro non‐inflammatory potential

“…LPS are amphipathic molecules (~10–20 kDa), which in solution aggregate to form large structures (spherical and/or cylindrical micelles) with large hydrodynamic radii (~60–100 nm). 43, 44 On the other hand, interleukins and TNFα are found in solution in mono, di and/or trimeric states (~10–50 kDa) 45 and adopt compact conformations resulting in small hydrodynamic radii (~2–10 nm). We therefore expected LPS to be unable to diffuse into the hydrogels, while interleukins and TNFα were expected to be able to diffuse out.…”

Esculentin-1a-Derived Peptides Promote Clearance of Pseudomonas aeruginosa Internalized in Bronchial Cells of Cystic Fibrosis Patients and Lung Cell Migration: Biochemical Properties and a Plausible Mode of Action

“…Note that LPS binds TLR-4 in its monomeric form (68). However, in aqueous environments, micellar assemblies of LPS are formed above its critical micellar concentrations (Ն14,000 ng/ml) (68,69). This may hamper the binding of LPS to TLR-4, thus explaining the inhibitory pseudo-wound-healing effect of LPS when used at high concentrations (i.e., Ն15,000 ng/ml) ( Fig.…”