High-Pressure Transition of a Poly(ethylene glycol)-Grafted Phospholipid Monolayer at the Air/Water Interface
Bibliographic record
Abstract
Monolayer behavior of a poly(ethylene glycol)-grafted distearoylphosphatidylethanolamine with PEG molecular weight 5000 (DSPE−PEG5000) was studied by a variety of experimental methods. Slope changes in the surface pressure−molecular area (π− A ) isotherm suggest two transitions in the DSPE−PEG5000 monolayer upon compression which were previously attributed to conformational changes in the polymeric moiety. However, comparative analysis of our experimental data implies that the second slope change in the isotherm at π ≈ 18 mN/m originates from the monolayer collapse. As visualized by Brewster angle and atomic force (AFM) microscopy, the fluid homogeneous DSPE−PEG5000 monolayer is unable to sustain high pressures and collapses through vesicular structures formed as a result of 2D to 3D relaxation of an overcompressed film. AFM topographic images provided a height value of 9 nm for the collapsed structures on top of the monolayer, which can be referred to as the height of DSPE−PEG5000 lamellar structures. Thus, the collapse at a surprisingly low surface pressure implies that a distinct region where the PEG5000 moiety would adopt a brush conformation is probably never achieved for the DSPE−PEG5000 monolayer. Ellipsometric measurements of monolayer thickness confirm that although an elongated conformation is developed prior to the monolayer collapse, this conformation is better described as an “extended mushroom” rather than a “brush”.
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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 | 0.000 |
| 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".