Combining liquid chromatography with ozone-induced dissociation for the separation and identification of phosphatidylcholine double bond isomers
Bibliographic record
Abstract
Revealing the inherent molecular diversity of lipid biology requires advanced analytical technologies. Distinguishing phospholipids that differ in the position(s) of carbon-carbon double bonds within their acyl chains presents a particular challenge because of their similar chromatographic and mass spectral behaviours. Here-for the first time-we combine reversed-phase liquid chromatography for separation of isomeric phospholipids with on-line mass spectral analysis by ozone-induced dissociation (OzID) for unambiguous double bond position assignment. The customised tandem linear ion-trap mass spectrometer used in our study is capable of acquiring OzID scans on a chromatographic timescale. Resolving the contributions of isomeric lipids that are indistinguishable based on conventional mass spectral analysis is achieved using the combination of liquid chromatography and OzID. Application of this method to the analysis of simple (egg yolk) and more complex (sheep brain) extracts reveals significant populations of the phosphatidylcholine PC 16:0_18:1(n−7) alongside the expected PC 16:0_18:1(n−9) isomer.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| 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".