Effect of chain unsaturation on bilayer response to pressure
Bibliographic record
Abstract
Using wide-line deuterium NMR, the effects of pressure on saturated-chain orientational order and gel--to--liquid-crystal phase transition temperature were observed in bilayers of 16:0-18:1 PC-${d}_{31}$ (POPC-${d}_{31}$) and 16:0-18:2 PC-${d}_{31}$ (PLPC-${d}_{31}$). Spectra were recorded for a range of pressures at selected temperatures and for a range of temperatures at selected pressures up to $193\phantom{\rule{0.3em}{0ex}}\mathrm{MPa}$. For 16:0-18:1 PC-${d}_{31}$, the main transition temperature increased by $\ensuremath{\sim}0.18\phantom{\rule{0.3em}{0ex}}\mathrm{K}∕\mathrm{MPa}$, a rate that is similar to what is found for bilayers of disaturated PC's. For 16:0-18:2 PC-${d}_{31}$, the increase in transition temperature with pressure was slightly smaller at $\ensuremath{\sim}0.13\phantom{\rule{0.3em}{0ex}}\mathrm{K}∕\mathrm{MPa}$. To investigate the isothermal response of chain orientational order to pressure, spectra for each lipid were obtained for three pressures (ambient, $55\phantom{\rule{0.3em}{0ex}}\mathrm{MPa}$, and $110\phantom{\rule{0.3em}{0ex}}\mathrm{MPa}$) near room temperature $(\ensuremath{\sim}25\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$ and for three pressures (ambient, $110\phantom{\rule{0.3em}{0ex}}\mathrm{MPa}$, and $193\phantom{\rule{0.3em}{0ex}}\mathrm{MPa}$) at higher temperature $(\ensuremath{\sim}40\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$. These temperatures were chosen such that the difference between the higher observation temperature and the main transition of 16:0-18:1 PC-${d}_{31}$ would be similar to the difference between the lower observation temperature and the main transition of 16:0-18:2 PC-${d}_{31}$. Application of a given pressure was found to raise the orientational order for all methylene groups on the saturated chain of a particular lipid by roughly similar amounts. For comparable pressure differences, the pressure-induced ordering of the 16:0-18:1 PC-${d}_{31}$ saturated chain at $\ensuremath{\sim}40\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ was greater than that of the corresponding chain in 16:0-18:2 PC-${d}_{31}$ at $\ensuremath{\sim}25\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. These observations suggest that increasing levels of chain unsaturation may reduce the sensitivity of bilayer order to variations in pressure at corresponding temperatures relative to their ambient pressure transitions.
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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".