The observation of multivalent complexes of Shiga-like toxin with globotriaoside and the determination of their stoichiometry by nanoelectrospray Fourier-transform ion cyclotron resonance mass spectrometry
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Bibliographic record
Abstract
We show by nanoelectrospray ionization (nanoES) Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) that it is possible to observe oligosaccharide-protein complexes with dissociation constants in the millimolar range, such as P(k) trisaccharide (globotriaoside) complexed with the Shiga-like toxin (SLT) of pathogenic E. coli. It is further demonstrated that nanoES/FT-ICR MS is an exquisite method to study quantitative aspects of the association of mono- and polyvalent oligosaccharide ligands with multimeric proteins, such as the SLTs. At increasing trisaccharide:protein ratios it was shown that the B(5 )toxin subunit complexes with 5 P(k) trisaccharides and only after all 5 copies of site 2 are essentially filled do any of the remaining 10 receptor sites become occupied. From the distribution of bound P(k)'s at the five binding sites, it was possible to establish association constants for each of the five sites and to confirm that binding occurs noncooperatively, the association constants for each site are identical and that compared to site 1, site 2 exhibits a tenfold higher affinity for the globotriaoside synthetic ligand 1. The facile identification of the occupancy of binding sites represents information that is not readily available by other techniques. This sensitive and rapid estimation of association constants for protein-ligand complexes, which are free of unpredictable secondary effects that plague enzyme linked assays, is likely to find wide application.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 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 | 0.001 |
| 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 it