Synthesis of three tethered trisaccharides to probe entropy contributions in carbohydrate—protein interactions
Bibliographic record
Abstract
Abstract Crystal structure data show that the branched trisaccharide 1 constitutes the complete antigenic determinant of the Salmonella serogroup B antigen that is recognized by monoclonal antibody SE155.4. In an effort to characterize the entropic costs associated with immobilization of glycosidic torsional angles in the bound state, three distinct intramolecularly tethered analogues of this trisaccharide 2‐4 have been synthesized. Two trisaccharides are tethered by a methylene acetal via the O‐2 position of the 3,6‐dideoxy‐hexose, abequose to either O‐2 of galactose (2) or O‐4 of mannose (3). The third tether, α,α′‐di‐thio‐p‐xylene, spans the C‐6 atoms of the mannose and galactose residues to create trisaccharide 4. The acetal tethers of 2 and 3 span hydroxyl centers that are known to be involved in intramolecular sugar‐sugar hydrogens bonds, but both trisaccharides are biologically inactive due to distorted conformations that cannot be accommodated in the antibody binding site. Trisaccharide 4 is active since both hydroxymethyl groups of galactose and mannose are solvent exposed in the bound state and the constrained conformation of 4 is virtually superimposable on the bound conformation of 1. Despite the retained complimentary and significant reduction of torsional flexibility, trisaccharide 4 exhibits a ΔG° = ‐7.6 kcal mol−1 compared to ΔG° = ‐7.1 kcal mol−1 for 1. The modest free energy gain for the tethered trisaccharide 4 arises from a small entropy gain (TΔΔS = 0.3 kcal mol−1) and an even smaller enthalpic change (ΔΔH = ‐0.2 kcal mol−1).
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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".