An Isocratic High-Performance Liquid Chromatographic Assay for CYP7Al-Catalyzed Cholesterol 7wHyciroxylation
Bibliographic record
Abstract
CYP7A1, which is the only CYP7A subfamily P450 tdentified to date ( 1 ), catalyzes cholesterol 7α-hydroxylation, the first, and rate-limiting, step in the converston of cholesterol to bile acids. CYP7Al has been Isolated from human liver and purified to apparent homogeneity ( 2 ). Rodent-model studies have established that CYP7A1 is highly regulated by physiological factors that influence hepatic-bile-acid biosynthesis, including cholesterol feedmg, dmrnal factors, and bile acids, whtch feedback-inhibit the overall btosynthetlc pathway in large part at the level of CYP7A1 gene expression ( 3 ). Relatrvely little is known about the regulation of human CYP7A1, although liver biopsy analyses have shown that hepatic CYP7A1 protem content is elevated in patients treated with the bile-acid sequesterant cholestyramme ( 4 ). Purified CYP7A1 is catalytically active in cholesterol 7α-hydroxylation ( 2 ) and immunoinhibition experiments with antihuman CYP7A1 antibodies have shown that CYP7A1 accounts for most of the cholesterol 7a-hydroxylase acttvtty in human liver microsomes ( 4 ). Thus, mlcrosomal cholesterol 7α-hydroxylase activity can be used as a marker for human liver CYP7A1. Several analytical methods have been developed to quantify hepatrc mrcrosomal cholesterol 7α-hydroxylation, including reversed-phase high-performance hquid chromatography (RPHPLC) ( 5 ), isotope dilution-mass spectrometry ( 6 ) and thin-layer chromatography (TLC) ( 7 ). This chapter describes a normal-phase, isocratic HPLC assay for the determination of cholesterol 7α-hydroxylase acttvity based on the conversion by cholesterol oxidase of the primary P450 metabohte 7α-hydroxycholesterol to 7α-hydroxy-4-cholesten-3-one, which can be detected at 254 nm. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.003 | 0.002 |
| Meta-epidemiology (narrow) | 0.004 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.007 | 0.004 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.003 | 0.002 |
| Research integrity | 0.002 | 0.004 |
| Insufficient payload (model declined to judge) | 0.005 | 0.007 |
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".