Selective determination of mitochondrial chelatable iron in viable cells with a new fluorescent sensor
Bibliographic record
Abstract
Mitochondrial chelatable ("redox-active") iron is considered to contribute to several human diseases, but has not yet been characterized in viable cells. In order to determine this iron pool, we synthesized a new fluorescent indicator, rhodamine B-[(1,10-phenanthrolin-5-yl)aminocarbonyl]benzyl ester (RPA). In a cell-free system, RPA fluorescence was strongly and stoichiometrically quenched by Fe(2+). RPA selectively accumulated in the mitochondria of cultured rat hepatocytes. The intramitochondrial RPA fluorescence was quenched when iron was added to the cells in a membrane-permeant form. It increased when the mitochondrial chelatable iron available to the probe was experimentally decreased by the membrane-permeant transition metal chelators pyridoxal isonicotinoyl hydrazone and 1,10-phenanthroline. The concentration of mitochondrial chelatable iron in cultured rat hepatocytes, quantified from the increase in RPA fluorescence after addition of pyridoxal isonicotinoyl hydrazone, was found to be 12.2 +/- 4.9 microM. Inhibition of haem synthesis with succinylacetone did not alter the signal obtained in hepatocytes, but a rapid increase in the concentration of mitochondrial chelatable iron was observed in human erythroleukaemia K562 cells. In conclusion, RPA enables the selective determination of the highly physiologically and pathophysiologically interesting mitochondrial pool of chelatable iron in intact cells and to record the time course of alterations of this pool.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".