Stabilization of the base-off forms of vitamin B12 and coenzyme B12 by encapsulation of the α-axial 5,6-dimethylbenzimidazole ligand with cucurbit[7]uril
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Bibliographic record
Abstract
Cucurbit[7]uril (CB[7]) forms very stable complexes with the alpha-axial 5,6-dimethylbenzimidazole (alpha-DMB) nucleotide base when dissociated from the Co(III) center in vitamin B(12) (CNCbl, K(CB[7]) = (7.5 +/- 0.5) x 10(4) dm(3) mol(-1)) and coenzyme B(12) (AdoCbl, K(CB[7]) = (3.02 +/- 0.35) x 10(6) dm(3) mol(-1)). The inclusion of alpha-DMB ligand facilitates its release from the metal center and its subsequent protonation, with significantly higher pK(base-off) values of 3.77 and 6.61, than determined for the free CNCbl (0.11) and AdoCbl (2.67), respectively. Addition of CB[7] to the base-on form of CNCbl at pH 2 provides for a direct measurement of the rate constant for the dissociation of the alpha-DMB ligand from the Co center (k = (4.6 +/- 0.2) x 10(-2) s(-1), DeltaH = 93 +/- 2 kJ mol(-1), DeltaS = +41 +/- 6 J K(-1) mol(-1)). The beta-axial 5'-deoxyadenosyl ligand (beta-Ado) on coenzyme B(12) is bound more weakly by a second CB[7] host (K(CB[7]) = (1.1 +/- 0.2) x 10(3) dm(3) mol(-1)), however inclusion of the beta-Ado ligand has no effect on the kinetics of its heterolytic photodissociation from the Co(III) center.
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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 | 0.000 | 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 it