The Functional Significance of Lipid Diversity: Orientation of Cholesterol in Bilayers Is Determined by Lipid Species
Bibliographic record
Abstract
The chemical diversity of lipids and their complex arrangements in supramolecular assemblies are in stark contrast to our previous notions of them as passive structural components. For example, in plasma membranes, sphingolipids are primarily located in the outer monolayer, whereas unsaturated phospholipids are more abundant in the inner leaflet. Our recent results offer a direct contribution to the importance of lipid diversity in biological membranes. We have studied the location of cholesterol within polyunsaturated fatty acid (PUFA) bilayers doped with different amounts of monounsaturated (POPC) or disaturated (DMPC) lipids. Using deuterium labeling and neutron diffraction, we have found that in PUFA bilayers, cholesterol can be flipped from its known position in the bilayer center to its commonly assumed upright orientation simply by varying the amount of POPC. Although it takes approximately 50 mol % POPC to flip cholesterol in PUFA bilayers, the same effect is achieved with only 5 mol % DMPC, elegantly emphasizing cholesterol's affinity for saturated chains. It also suggests that the presence of PUFA in the inner leaflet of a cellular bilayer may enhance the transfer of cholesterol to the outer layer, potentially modifying raft composition and the local function of a membrane.
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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".