Chemosynthetic homologues of Mycoplasma pneumoniae ß-glycolipid antigens for the diagnosis of mycoplasma infectious diseases.

Mycoplasma pneumoniae expresses ß-glycolipids (ß-GGLs) in cytoplasmic membranes, which possess a unique ß(1 → 6)-linked disaccharide epitope, which has high potential in biochemical and medicinal applications. In the present study, a series of ß-GGLs homologues with different acyl chains (C12, C14, C16, and C18) were prepared from a common precursor. An ELISA assay using an anti-(ß-GGLs) monoclonal antibody indicated that the synthetic homologues with long acyl chains had greater diagnostic potential in the order C18 > C16 > C14 > C12. Toward a simultaneous detection of natural glycolipids by mass spectrometry (MS), a deuterium-labeled C16 homologue (ß-GGL-C16-d3) was prepared and applied as an internal standard for a high-resolution electrospray ionization MS (ESI-MS) analysis. The ESI-MS analysis was used to identify and quantify acyl homologues (C16/C16, C16/C18, and C18/C18) of ß-GGL-C16 in cultured M. pneumoniae. A ß-GGLs homologue with a 1,2-diacetyl group (C2) was also prepared as a "water soluble" glycolipid homologue and characterized by 1H NMR spectroscopy. We envisage that each of these chemosynthetic homologues will provide promising approaches to solve medical and biological problems associated with mycoplasma infectious diseases (MIDs).

An easy α-glycosylation methodology for the synthesis and stereochemistry of mycoplasma α-glycolipid antigens.

Mycoplasma fermentans possesses unique α-glycolipid antigens (GGPL-I and GGPL-III) at the cytoplasm membrane, which carry a phosphocholine group at the sugar primary (6-OH) position. This paper describes a practical synthetic pathway to a GGPL-I homologue (C(16:0)) and its diastereomer, in which our one-pot α-glycosylation method was effectively applied. The synthetic GGPL-I isomers were characterized with (1)H NMR spectroscopy to determine the equilibrium among the three conformers (gg, gt, tg) at the acyclic glycerol moiety. The natural GGPL-I isomer was found to prefer gt (54%) and gg (39%) conformers around the lipid tail, while adopting all of the three conformers with equal probability around the sugar position. This property was very close to what we have observed with respect to the conformation of phosphatidylcholine (DPPC), suggesting that the Mycoplasma glycolipids GGPLs may constitute the cytoplasm fluid membrane together with ubiquitous phospholipids, without inducing stereochemical stress.