Fluorescence Resonance Energy Transfer in Partially and Fully Labeled Pyrene Dendronized Porphyrins Studied with Model Free Analysis
Bibliographic record
Abstract
A series of dendronized porphyrins were synthesized and their photophysical properties were determined by UV–vis absorption, steady-state fluorescence, and time-resolved fluorescence. The constructs contained a porphyrin core connected to a first generation Fréchet-type dendron (Py 2 G1) with or without a C 4 -butanoate linker, and to a second generation dendron (Py 4 G2) with a C 4 -linker. Pyrene and porphyrin were selected as donor and acceptor, respectively, for fluorescence resonance energy transfer or FRET. FRET occurred efficiently within the dendronized porphyrins as determined from the extremely weak fluorescence of pyrene. The number of pyrene groups present in the constructs was varied from two to eight, but was found to have little effect on FRET as FRET took place efficiently from an excited pyrene to a ground-state porphyrin. The parameter that was found to affect FRET the most was the distance separating pyrene from porphyrin within a construct. This effect was probed successfully by fitting the pyrene and porphyrin fluorescence decays according to the model free analysis (MFA) which yielded the average rate constant ⟨ k ET ⟩ for FRET. ⟨ k ET ⟩ increased continuously with decreasing distance separating porphyrin and pyrene as determined by conducting molecular mechanics optimizations on the constructs. The ⟨ k ET ⟩ values were used to determine the through-space distance d Por–Py TS separating porphyrin from pyrene. d Por–Py TS was found to scale as ( d Por–Py EXT ) 0.5, where d Por–Py EXT represents the distance separating porphyrin and pyrene when the construct adopts its most extended conformation. This relationship suggests that FRET occurs intramolecularly inside the constructs between pyrene and porphyrin where both dyes are linked by a string of freely jointed Kuhn segments of length l K = 9 Å.
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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 | 0.001 |
| 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".