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Complexity in a Simple Self-Assembling System: Lecithin-Water-Ethanol Mixtures Exhibit a Re-Entrant Phase Transition and a Vesicle-Micelle Transition (VMT) on Heating.
Burni, Faraz A; Agrawal, Niti R; Walker, Maxwell; Ali, Hamna; Raghavan, Srinivasa R.
Afiliación
  • Burni FA; Department of Chemical & Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, United States.
  • Agrawal NR; Department of Chemical & Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, United States.
  • Walker M; Department of Chemical & Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, United States.
  • Ali H; Department of Chemical & Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, United States.
  • Raghavan SR; Department of Chemical & Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, United States.
Langmuir ; 2024 Aug 19.
Article en En | MEDLINE | ID: mdl-39158103
ABSTRACT
We report surprising results for the self-assembly of lecithin (a common phospholipid) in water-ethanol mixtures. Lecithin forms vesicles (∼100 nm diameter) in water. These vesicles are transformed into small micelles (∼5 nm diameter) by a variety of destabilizing agents such as single-tailed surfactants and alcohols. In a surfactant-induced vesicle-micelle transition (VMT), vesicles steadily convert to micelles upon adding the surfactant─thereby, the turbidity of the solution drops monotonically. Instead, when an alcohol like ethanol is added to lecithin vesicles, we find a new, distinctive pattern in phase behavior as the ethanol fraction feth in water is increased. The turbidity first decreases (from feth = 0 to 37%), then rises sharply (feth = 37 to 50%), and then eventually decreases again (feth > 55%). Concomitant with the turbidity rise, the vesicles separate into two phases around feth = 50% before a single phase reappears at higher feth─in other words, there is a "re-entrant" phase transition from 1-phase to 2-phase and back to 1-phase with increasing feth. Vesicles near the phase boundary (∼feth = 45%) also show a VMT upon heating. Similar patterns are seen with other alcohols such as methanol and propanol. We ascribe these complex trends to the dual role played by alcohols (a) first, alcohols reduce the propensity for flat lipid bilayers to bend and form closed spherical vesicles; and (b) second, alcohols diminish the tendency of lipids to self-assemble in the solvent mixture. At low alcohol fractions, (a) dominates, causing the initially unilamellar vesicles to grow into multilamellar vesicles (MLVs), which eventually phase-separate. Thereafter, (b) dominates, and the vesicles convert into micelles. Support for our hypothesis comes from scattering (SANS) and microscopy (cryo-TEM). Thus, we have uncovered a general paradigm for lipid self-assembly in solvent mixtures, and this may even have physiological relevance.
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Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Idioma: En Revista: Langmuir Asunto de la revista: QUIMICA Año: 2024 Tipo del documento: Article País de afiliación: Estados Unidos Pais de publicación: Estados Unidos
Texto completo
Añadir a Mi BVS
Imprimir
XML
PubMed Links
Buscar en Google

Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Idioma: En Revista: Langmuir Asunto de la revista: QUIMICA Año: 2024 Tipo del documento: Article País de afiliación: Estados Unidos Pais de publicación: Estados Unidos