Surfactant-Mediated Structural Modulations to Planar, Amphiphilic Multilamellar Stacks

Abstract

The hydrophobic effect, a ubiquitous process in biology, is a primary thermodynamic driver of amphiphilic selfassembly. It leads to the formation of unique morphologies including two highly important classes of lamellar and micellar mesophases. The interactions between these two types of structures and their involved components have garnered significant interest because of their importance in key biochemical technologies related to the isolation, purification, and reconstitution of membrane proteins. This work investigates the structural organization of mixtures of the lamellar-forming phospholipid 1palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and two zwitterionic micelle-forming surfactants, being n-dodecyl-N,Ndimethyl-3-ammonio-1-propanesulfonate (Zwittergent 3-12 or DDAPS) and 1-oleoyl-2-hydroxy-sn-glycero-3-phosphocholine (O-Lyso-PC), when assembled by water vapor hydration with X-ray diffraction measurements, brightfield optical microscopy, wide-field fluorescence microscopy, and atomic force microscopy. The results reveal that multilamellar mesophases of these mixtures can be assembled across a wide range of POPC to surfactant (POPC:surfactant) concentration ratios, including ratios far surpassing the classical detergent-saturation limit of POPC bilayers without significant morphological disruptions to the lamellar motif. The mixed mesophases generally decreased in lamellar spacing (D) and headgroup-to-headgroup distance (D hh ) with a higher concentration of the doped surfactant, but trends in water layer thickness (D w ) between each bilayer in the stack are highly variable. Further structural characteristics including mesophase topography, bilayer thickness, and lamellar rupture force were revealed by atomic force microscopy (AFM), exhibiting homogeneous multilamellar stacks with no significant physical differences with changes in the surfactant concentration within the mesophases. Taken together, the outcomes present the assembly of unanticipated and highly unique mixed mesophases with varied structural trends from the involved surfactant and lipidic components. Modulations in their structural properties can be attributed to the surfactant's chemical specificity in relation to POPC, such as the headgroup hydration and the hydrophobic chain tail mismatch. Taken together, our results illustrate how specific chemical complexities of surfactant− lipid interactions can alter the morphologies of mixed mesophases and thereby alter the kinetic pathways by which surfactants dissolve lipid mesophases in bulk aqueous solutions.

Ecologically viable carbon nano-onions for the efficient removal of methyl orange azo dye and its environmental assessment

“…Initially, the Langmuir isotherm was employed to describe gas–solid interactions, but it has since been adapted for use with various adsorbents. 54 It is an empirical model rooted in kinetic principles, wherein the rates of adsorption and desorption on the surface reach an equilibrium where no net accumulation occurs. As per the provided assumptions, the Langmuir process exhibits certain characteristics: (a) adsorption occurs in a single layer, (b) adsorption sites are uniform, (c) the adsorption energy remains constant, and (d) there is no interaction between adjacent adsorbed molecules.…”

The effect of water in THF/water mixtures on CMC, aggregation sizes, and fluorescence quenching of a new calix[4]resorcinarene macrocycle

“…1–7 They act as excipients in pharmaceutical and cosmetic formulations, stabilize dispersed systems, increase drug solubility, and can be used as drug permeability enhancers. 8–12 Their self-assembling properties lead to the formation of micelles, and the critical micelle concentration (CMC) is a crucial parameter for these molecules. 13 When the concentration of the surfactants falls below the CMC, they form a coating on interfacial surfaces, reducing surface tension across gas, liquid, and solid interfaces.…”

“…However, when the concentration exceeds the CMC, the surfactants organize themselves into distinct spherical and cylindrical micellar mesostructures, which disperse throughout the bulk aqueous environment as a colloidal solution. 9 Resorcinarenes and calixarenes are macrocyclic blocks that are easily available and can act as supramolecular hosts. They are made up of aromatic rings derived from resorcinol or phenol, which are connected by carbon bridges.…”