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 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 | 0.000 | 0.001 |
| 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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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 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".