A Calorimetric and Spectroscopic Comparison of the Effects of Lathosterol and Cholesterol on the Thermotropic Phase Behavior and Organization of Dipalmitoylphosphatidylcholine Bilayer Membranes
Bibliographic record
Abstract
We performed differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopic measurements to study the effects of lathosterol (Lath) on the thermotropic phase behavior and organization of dipalmitoylphosphatidylcholine (DPPC) bilayer membranes and compared our results with those previously reported for cholesterol (Chol)/DPPC binary mixtures. Lath is the penultimate intermediate in the biosynthesis of Chol in the Kandutsch-Russell pathway and differs from Chol only in the double bond position in ring B, which is between C7 and C8 in Lath and between C5 and C6 in Chol. Our DSC studies indicate that the incorporation of Lath is more effective than Chol in reducing the temperature and enthalpy of the DPPC pretransition. At lower sterol concentrations (≤10 mol %), incorporation of both Lath and Chol decreases the temperature, enthalpy, and cooperativity of the sharp component of the main phase transition of DPPC to a similar extent, but at higher sterol concentrations, Lath is more effective at decreasing the phase transition temperature, enthalpy, and cooperativity than Chol. These results indicate that at higher concentrations, Lath is more disruptive of DPPC gel-state bilayer packing than Chol is. Moreover, incorporation of Lath decreases the temperature of the broad component of the main phase transition of DPPC, whereas Chol increases it; this difference in the direction and magnitude of the temperature shift is accentuated at higher sterol concentrations. Although at sterol concentrations of ≤20 mol % Lath and Chol are almost equally effective at reducing the enthalpy and cooperativity of the broad component of the main phase transition, at higher sterol levels Lath is less effective than Chol in these regards and does not completely abolish the cooperative hydrocarbon chain melting phase transition at 50 mol %, as does Chol. These latter results indicate that Lath both is more disruptive with respect to the low-temperature state of the sterol-enriched domains of DPPC bilayers and has a lower lateral miscibility in DPPC bilayers than Chol. Our FTIR spectroscopic studies suggest that Lath incorporation produces a less tightly packed bilayer than does Chol at both low (gel state) and high (liquid-crystalline state) temperatures, which is characterized by increased H-bonding between water and the carbonyl groups of the fatty acyl chains in the DPPC bilayer. Overall, our studies indicate that Lath and Chol incorporation can have rather different effects on the thermotropic phase behavior and organization of DPPC bilayers and thus that the position of the double bond in ring B of a sterol molecule can have an appreciable effect on the physical properties of sterol molecules.
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 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".