Structural characterization of the outer core and the O‐chain linkage region of lipopolysaccharide from <i>Pseudomonas aeruginosa</i> serotype O5
Bibliographic record
Abstract
The point of attachment of the O-chain in the outer core region of Pseudomonas aeruginosa serotype O5 lipopolysaccharide (LPS) was determined following a detailed analysis of the extended core oligosaccharide, containing one trisaccharide O-chain repeating unit, present in both the wild-type strain PAO1 and O-chain deficient mutant strains AK1401 and PAO-rfc. The structure of the extended core oligosaccharide was determined by various mass spectrometric methods as well as one-dimensional and two-dimensional NMR spectroscopy. Furthermore, the one-dimensional analogues of NOESY and TOCSY experiments were applied to confirm the structure of the outer core region in the O-chain polysaccharide. In both the extended core oligosaccharide and the core of the smooth LPS, a loss of one of the beta-glucosyl residues and the translocation of the alpha-rhamnosyl residue, followed by the attachment of the first O-chain repeating unit was observed. This process is complicated and could involve two distinct rhamnosyltransferases, one with alpha-1, 6-linkage specificity and another with alpha-1,3-linkage specificity. It is also plausible that an alpha-1,3 rhamnosyltransferase facilitates the addition of the 'new' alpha-rhamnosyl residue that will act as a receptor for the attachment of the single O-antigen repeating unit in the LPS of the semi-rough mutant. The 2-amino-2-deoxy-fucosyl residue of the first O-chain repeating unit directly attached to the core was found to have a beta-anomeric configuration instead of an alpha configuration, characteristic for this residue as a component of the O-chain polysaccharide. The results of this study provide the first example of the mechanistic implications of the structure of the outer core region in a fully assembled O-chain containing LPS, differing from the O-chain deficient rough LPS.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".