Dissociation Kinetics of the Streptavidin–Biotin Interaction Measured Using Direct Electrospray Ionization Mass Spectrometry Analysis
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Bibliographic record
Abstract
Dissociation rate constants (k (off)) for the model high affinity interaction between biotin (B) and the homotetramer of natural core streptavidin (S(4)) were measured at pH 7 and temperatures ranging from 15 to 45 °C using electrospray ionization mass spectrometry (ESI-MS). Two different approaches to data analysis were employed, one based on the initial rate of dissociation of the (S(4) + 4B) complex, the other involving nonlinear fitting of the time-dependent relative abundances of the (S(4) + iB) species. The two methods were found to yield k (off) values that are in good agreement, within a factor of two. The Arrhenius parameters for the dissociation of the biotin-streptavidin interaction in solution were established from the k (off) values determined by ESI-MS and compared with values measured using a radiolabeled biotin assay. Importantly, the dissociation activation energies determined by ESI-MS agree, within 1 kcal mol(-1), with the reported value. In addition to providing a quantitative measure of k (off), the results of the ESI-MS measurements revealed that the apparent cooperative distribution of (S(4) + iB) species observed at short reaction times is of kinetic origin and that sequential binding of B to S(4) occurs in a noncooperative fashion with the four ligand binding sites being kinetically and thermodynamically equivalent and independent.
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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 | 0.002 |
| Bibliometrics | 0.000 | 0.002 |
| 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