Polyelectrolyte-lipid vesicle interactions: solid state deuterium and phosphorus nuclear magnetic resonance studies
Bibliographic record
Abstract
Interactions between charged vesicles and polyelectrolytes were investigated by solid state nuclear magnetic resonance (NMR). It was shown with deuterium (2H) NMR that anionic giant unilamellar vesicles (GUVs), containing headgroup-deuterated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), fused with cationic small unilamellar vesicles (SUVs) upon mixing. The extent of fusion was quantitatively deduced from the quadrupolar splittings. The interaction of polylysine of different lengths (Lysn) with phosphatidylserine/POPC multilamellar vesicles (MLVs) was investigated using 2H NMR of headgroup-deuterated POPC. It was discovered that Lys 30 (N = 30) and Lys100 (but not Lys5) added to the MLVs were able to produce two resolvable 2H NMR spectral components consistent with the co-existence of polylysine-bound and polylysine-free domains. At physiological salt concentrations, however, only Lys100 yielded 2H NMR resolvable domains. The effect of binding a copolymer of N-isopropylacrylamide, N-[4-(1-pyrenyl)butyl]- N-n-octadecylacrylamide and N-glycydylacrylamide (PNIPAM-PyC18-Gly) on membrane stability in cationic MLVs was also examined using phosphorus (31P) and 2H NMR of headgroup-deuterated POPC. For n-octadecyldiethylene oxide (ODEO) MLVs, PNIPAM-PyC18-Gly induced a complete conversion from a bilayer-type 31P NMR spectrum to one characteristic of lipids undergoing isotropic motional averaging. This response was sustained at high temperatures. For POPC MLVs, only at high levels of cationic lipid and ionic strength did PNIPAM-PyC18-Gly induce even a partial conversion to an isotropic-type 31P NMR spectrum. Raising the temperature eliminated this isotropic spectral component. We conclude that the binding of PNIPAM-PyC18-Gly to POPC MLVs is dominated by electrostatic attraction, while for ODEO MLVs there is the additional contribution of hydrogen bonding. Interactions between POPC-containing cationic GUVs and polystyrene sulfonate (PSSS) (of different molecular weights) were investigated with 2H NMR of headgroup-deuterated POPC. It was discovered that PSSS segregates 1,2-dioleoyl-3-(trimethyl-ammonio) propane (DOTAP) on the GUV membrane, leading to GUV disruption. It was proposed that this disruption occurs following the membrane stress created from PSSS-induced transbilayer flip-flop of DOTAP. When PSSS was complexed with cationic SUVs to form PSSS lipoplexes and added to POPC-containing anionic GUVs, 2H NMR results indicated that PE-containing PSSS lipoplexes bind and fuse with GUVs. When PE is omitted from the PSSS lipoplexes, there is much less fusion observed. What is evident is the importance of the presence of PE in the lipoplexes, which were created to mimic the DNA lipoplexes used in gene transfection. The results of all these studies provide insight into the consequences of vesicle-vesicle and vesicle-polyelectrolyte interactions.
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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 | 0.000 |
| 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".