A HPLC-based methylene blue/methylene green method for accurate measurement of hydrogen sulfide in plasma
Bibliographic record
Abstract
Hydrogen sulfide (H 2 S) is an endogenously produced gasotransmitter with important physiological roles in cardiovascular, neurological, and metabolic health. Accurate quantification of circulating H 2 S remains technically challenging due to its volatility, reactivity, and rapid oxidation. Here, we present a high-performance liquid chromatography (HPLC)-based methylene blue method using methylene green as an internal reference (MBMG) for plasma H 2 S quantification with improved sensitivity, reproducibility, and compatibility. Using this approach, a linear standard curve was generated for NaHS concentrations between 0.05–10 μM. The method successfully detected significantly higher plasma H 2 S levels in wild-type (WT) mice (∼0.5 μM) compared to CSE-knockout (KO) mice (∼0.15 μM), with both groups showing expected increases following NaHS intraperitoneal injection. Specificity testing revealed minimal interference from biologically relevant sulfur species; only cysteine at supraphysiological concentrations generated a negligible signal. Plasma cysteine levels remained unchanged following NaHS injection. Post-reaction samples remained stable for at least six months at −80 °C, facilitating remote analysis and long-term storage. Collectively, the MBMG method provides a practical and sensitive platform for reliable plasma H 2 S measurement, with broad applicability in basic, translational, and clinical research settings.
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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 | 0.002 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| 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".