DNA Adducts With Chlorophyll and Chlorophyllin As Antimutagenic Agents: Synthesis, Stability, and Structural Features
Bibliographic record
Abstract
Porphyrins and their metal derivatives are strong DNA binders with association constants of 105 M −1 to 107 M −1. Some of these compounds have been used for radiation sensitization therapy of cancer and are targeted to interact with cellular DNA. Chlorophyll (CHL) and chlorophyllin (CHLN), a food-grade derivative of chlorophyll, the ubiquitous green plant pigment widely consumed by humans, are potent inhibitors of experimental carcinogenesis. The aim of this report was to examine the interaction of calf-thymus DNA with CHL and CHLN in aqueous solution at physiological pH, with pigment/DNA(phosphate) molar ratios (r) of 1/80 to 1/2. Fourier transform infrared (FTIR) difference spectroscopic method was used to determine the pigment binding mode, binding constant, sequence selectivity, DNA secondary structure and structural variations of the pigment-DNA complexes in aqueous solution. Spectroscopic evidence showed that chlorophyll is an external DNA binder with no affinity toward DNA intercalation. CHL bindings are through the backbone PO2 group and the guanine N-7 site of the G-C base pair (major groove) with overall binding constant of K=1.13×104 M −1 CHLN binds DNA via intercalative mode into the G-C and A-T-rich regions with a minor perturbation of the backbone PO2 group with overall binding constant K=3.56×103 M −1. However, The CHL distributions are 60% with the backbone PO2 group and 20% with the G-C base pairs, whereas CHLN intercalation is 25% with A-T and 15% with G-C base pairs. A partial reduction of B-DNA structure in favor of A-DNA occurs upon CHL and CHLN complexation.
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How this classification was reachedexpand
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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".