Macromolecular Conformation of Low-Generation PAMAM Dendrimers Probed by Pyrene Excimer Formation
Bibliographic record
Abstract
A series of pyrene-labeled PAMAM dendrimers (PyCX-PAMAM-GY, where X (=4, 8, or 12) and Y (=0, 1, or 2) represent the number of atoms in the pyrenyl linker and the dendrimer generation, respectively) were studied by acquiring their time-resolved fluorescence decays in N, N -dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The fluorescence decays were fitted globally according to the model-free analysis (MFA), which yielded the average rate constant ⟨ k ⟩ for pyrene excimer formation (PEF). ⟨ k ⟩ was compared with the local pyrene concentration [Py] loc inside the dendrimers, which was calculated by assuming that the segments constituting the dendrimer interior obey Gaussian statistics. ⟨ k ⟩ was found to increase linearly with [Py] loc in both solvents, but the straight lines had different slopes due to differences in solvent viscosity and polarity. These differences were accounted for by dividing ⟨ k ⟩ by k diff, which is the bimolecular rate constant for PEF generated by n -hexyl-1-pyrenebutyramide used as a model compound. The ⟨ k ⟩/ k diff ratios obtained for all the PyCX-PAMAM-GY samples in DMF and DMSO collapsed onto a single master line where ⟨ k ⟩/ k diff increased linearly with [Py] loc . The strong correlation found between ⟨ k ⟩ and [Py] loc suggested that the oligomeric segments constituting the interior of the low-generation ( Y = 0, 1, and 2) PAMAM dendrimers obeyed Gaussian statistics. This fact was further supported by using the Gaussian approximation to calculate the radius of gyration ( R g ) of PAMAM dendrimers and compare them to the R g values obtained by molecular dynamics simulations. The excellent agreement obtained between the two sets of R g values validated the assumption. Furthermore, the direct relationship between ⟨ k ⟩ and [Py] loc established in this study demonstrates that ⟨ k ⟩ provides a quantitative measure of the internal density of the dendrimers, an observation with considerable implications for the quantitative conformational characterization of macromolecules with a complex architecture in solution.
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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 | 0.000 |
| 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".