Mass Spectrometric Analysis of Intact Lipooligosaccharide: Direct Evidence for <i>O</i>-Acetylated Sialic Acids and Discovery of <i>O</i>-Linked Glycine Expressed by <i>Campylobacter jejuni</i>
Bibliographic record
Abstract
The lipooligosaccharides (LOS) of Campylobacter jejuni is an important virulence factor. Its core oligosaccharide component is frequently sialylated and bears a close resemblance with host gangliosides. The display of ganglioside mimics by this bacterium is believed to trigger the onset of the autoimmune condition Guillain-Barré syndrome (GBS) in some individuals. Considerable effort has been directed toward the structural characterization of the glycan component of the LOS of C. jejuni strains isolated from GBS patients. Capillary electrophoresis-mass spectrometry (CE-MS) has been a particularly useful analytical technique applied toward this task. Conventional analysis of bacterial LOS by CE-MS has generally involved the prior removal of O-acyl lipid chains, which is necessary for the effective solubilization and separation of the heterogeneous ensemble of LOS species. Unfortunately, O-deacylation causes the undesired removal of important glycan-associated O-linked modifications, such as O-acetate and O-linked amino acids. In this report, we describe a CE-MS technique developed for the rapid analysis of fully intact LOS from C. jejuni. Using this method, we report the structural characterization of the glycan from 10 GBS-associated strains and two enteritis strains, using material isolated from as little as one colony. The application of this technique has enabled us to unambiguously identify LOS-bound O-acetylated sialic acid in a number of strains and has revealed for the first time that C. jejuni frequently modifies its core with O-linked glycine. Our studies demonstrate that MS-based structural analysis of bacterial LOS can be optimized to the level where only a single-colony quantity of material is required and time-consuming chemical treatments can be avoided.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".