β-Cyclodextrin Host−Guest Complexes Probed under Thermodynamic Equilibrium: Thermodynamics and AFM Force Spectroscopy
Bibliographic record
Abstract
The rupture forces of individual host-guest complexes between beta-cyclodextrin (beta-CD) heptathioether monolayers on Au(111) and several surface-confined guests were measured in aqueous medium by single molecule force spectroscopy using an atomic force microscope. Anilyl, toluidyl, tert-butylphenyl, and adamantylthiols (0.2-1%) were immobilized in mixed monolayers with 2-mercaptoethanol on gold-coated AFM tips. For all guests and for all surface coverages, the force-displacement curves measured between the functionalized tips and monolayers of beta-CD exhibited single, as well as multiple, pull-off events. The histograms of the pull-off forces showed several maxima at equidistant forces, with force quanta characteristic for each guest of 39 +/- 15, 45 +/- 15, 89 +/- 15, and 102 +/- 15 pN, respectively. These force quanta were independent of the loading rate, indicating that, because of the fast complexation/decomplexation kinetics, the rupture forces were probed under thermodynamic equilibrium. The force values followed the same trend as the free binding energy Delta G degrees measured for model guest compounds in solution or on beta-CD monolayers, as determined by microcalorimetry and surface plasmon resonance measurements, respectively. A descriptive model was developed to correlate quantitatively the pull-off force values with the Delta G degrees of the complexes, based on the evaluation of the energy potential landscape of tip-surface interaction.
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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 | 0.001 |
| 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 | 0.001 |
| 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".