Structural elucidation of lipopolysaccharide core oligosaccharides from <i>lic1</i> and <i>lic1</i>/<i>lic2</i> mutants of Haemophilus influenzae type b strain Eagan
Bibliographic record
Abstract
The structures of lipopolysaccharides (LPSs) of lic1 and lic1/lic2 mutants from Haemophilus influenzae type b strain Eagan (RM153) were investigated using methylation analysis, electrospray ionization - mass spectrometry, and nuclear magnetic resonance spectroscopy on O-deacylated, O- and N-deacylated core oligosaccharide (OS); and deacylated, dephosphorylated, and terminally reduced samples. The backbone OS derived from the major LPS glycoforms were determined to consist of the inner-core triheptosyl unit, L-alpha-D-Hepp-(1-2)-L-alpha-D-Hepp-(1-3)-L-alpha-D-Hepp-(1-, common to all H. influenzae strains investigated to date that is linked to the lipid A region of the molecule via a Kdo residue to which beta-D-Glcp and beta-D-Galp residues are attached in 1,4 and 1,2 linkages to the proximal (HepI) and distal (HepIII) heptose residues, respectively. It was found that the lic1 mutant predominately elaborates the Hex4 LPS glycoforms previously identified in the parent strain where a beta-D-Glcp-(1-4)-alpha-D-Glcp unit is linked in a 1,3 linkage to the central heptose (HepII) of the triheptosyl moiety. The lic1 locus consists of 4 genes (lic1A to lic1D) in a single transcriptional unit that directs phase variable expression of phosphocholine. The lic1A gene is phased off in the RM153 isolate of strain Eagan. LPS from the double mutant, lic1/lic2 had a similar structure to that of lic1 mutant except that there was no chain extension from the central heptose in the inner core (HepII). The lic2 locus consists of 4 genes (lic2A to lic2D). Our structural data were consistent with the proposed function of lic2C, providing the first definitive evidence for its role as the glycosyltransferase required for chain initiation from HepII. The presence of an O-acetyl group at O-3 of the distal heptose (HepIII) was elucidated by 1H NMR on the mild acid liberated core OS samples.
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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) | 0.000 | 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".