Hypothesis: A well-defined discoidal bicelle composed of three lipids, specifically zwitterionic long-chain
1,2 dipalmitoyl phosphocholine (DPPC) and short-chain 1,2 dihexanoyl phosphocholine (DHPC) doped
with anionic 1,2 dipalmitoyl phosphoglycerol (DPPG) provides a generalized template for the synthesis
of hydrophobic polymer nano-rings. The lipid molar ratio of DPPC/DHPC/DPPG is 0.71/0.25/0.04. The
detailed investigation and discussion were based on styrene but tested on three other vinyl monomers.
Experiments: The structure of nano-rings is identified through the detailed analysis of small angle X-ray/
neutron scattering (SAXS and SANS) data and transmission electron micrographs (TEM), supported by the
differential scanning calorimetric (DSC) data before and after polymerization. The investigation covers
samples with a styrene-to-lipid ratio ranged varied from 1:50 to 1:10.
Findings: The styrene monomers are initially located at both the discoidal planar (long-chain lipid rich)
and rim (short-chain lipid rich) regions. During polymerization, they migrate to the more fluid rim
regionsection. The formation mechanism involves the interplay of hydrophobic interaction, mismatched
miscibility of polystyrene between the ordered and disordered phases, and crystallinity of the long lipid
acyl chains. This facile synthesis is proven applicable for several hydrophobic monomers. The welldefined
nano-rings greatly enhance the interfacial area and have the potential to be the building blocks
for functional materials, if monomers are incorporated with desirable functions, for future applications.
more »
« less
Synthesis of Polymer Nanoweb via a Lipid Template
We report a generalized platform for synthesizing a polymer nanoweb with a high specific surface area via a bicellar template, composed of 1,2-dipalmitoyl phosphocholine (DPPC), 1,2-dihexanoyl phosphocholine
(DHPC), and 1,2-dipalmitoyl phosphoglycerol (DPPG). The pristine bicelle (in the absence of monomer or polymer) yields a variety of well-defined structures, including disc, vesicle, and perforated lamella. The addition of styrene monomers in the mixture causes bicelles to transform into lamellae. Monomers are miscible with DPPC and DPPG initially, while polymerization drives polymers to the DHPC-rich domain, resulting in a polymer nanoweb supported by the outcomes of small angle neutron scattering, differential scanning calorimetry, and transmission electron microscopy.
more »
« less
- Award ID(s):
- 1930906
- PAR ID:
- 10481570
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- ACS Macro Letters
- Volume:
- 12
- Issue:
- 7
- ISSN:
- 2161-1653
- Page Range / eLocation ID:
- 993 to 998
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Membranes serve diverse functions in biological systems. Variations in their molecular compositions impact their physical properties and lead to rich phase behavior such as switching from the gel to fluid phase and/or separation to micro- and macrodomains with different molecular compositions. We present a combined computational and experimental study of the phase behavior of a mixed membrane of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) molecules. This heterogeneous membrane changes from gel to fluid and shows separate domains as a function of temperature. Atomically detailed simulations provide microscopic information about these molecular assemblies. However, these systems are challenging for computations since approaching equilibrium necessitates exceptionally long molecular dynamics trajectories. We use the simulation method of MDAS (Molecular Dynamics with Alchemical Steps) to generate adequate statistics. Isotope-edited IR spectroscopy of the lipids was used to benchmark the simulations. Together, simulations and experiments provide insight into the structural and dynamical features of the phase diagram.more » « less
-
null (Ed.)Antimicrobial pentatopic 2,2′:6′,2′′-terpyridines that form 3-D supramolecular hexagonal prisms with Cd 2+ through coordination driven self-assembly can be entrapped by lipid discoidal bicelles, composed of 1,2-dipalmitoyl- sn-glycero -3-phosphocholine, 1,2-dihexanoyl- sn-glycero -3-phosphocholine and 1,2-dipalmitoyl- sn-glycero -3-phospho-(1′-rac-glycerol) lipid, forming a well-defined nanocomplex. Structural characterization performed by very small angle neutron scattering, small angle X-ray scattering and transmission electron microscopy suggests that the hexagonal prisms are preferably located at the rim of bicellar discs with the hexagonal face in parallel with the bilayers, instead of face-to-face stacking. Such a configuration reduces the π−π interaction and consequently enhances the fluorescence emission. Since novel supramolecules were reported to have antibiotic functions, this study provides insight into the interactions of antimicrobial supermolecules with lipid membranes, leading to potential theranostic applications.more » « less
-
Techniques that can probe nanometer length scales, such as small-angle neutron scattering (SANS), have become increasingly popular to detect phase separation in membranes. But to extract the phase composition and domain structure from the SANS traces, complementary information is needed. Here, we present a SANS, calorimetry and densitometry study of a mixture of two saturated lipids that exhibits solidus–liquidus phase coexistence: 1,2-dipalmitoyl-d62-sn-glycero-3-phosphocholine (dDPPC, tail-deuterated DPPC) and 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC). With calorimetry, we investigated the phase diagram for this system and found that the boundary traces for both multilamellar vesicles (MLVs) as well as 50 nm unilamellar vesicles overlap. Because the solidus boundary was mostly inaccessible by calorimetry, we investigated it by both SANS and molecular volume measurements for a 1:1 dDPPC:DLPC lipid mixture. From the temperature behavior of the molecular volume for the 1:1 dDPPC:DLPC mixture, as well as the individual molecular volume of each lipid species, we inferred that the liquidus phase consists of only fluid-state lipids while the solidus phase consists of lipids that are in gel-like states. Using this solidus–liquidus phase model, the SANS data were analyzed with an unrestricted shape model analysis software: MONSA. The resulting fits show irregular domains with dendrite-like features as those previously observed on giant unilamellar vesicles (GUVs). The surface pair correlation function describes a characteristic domain size for the minority phase that decreases with temperature, a behavior found to be consistent with a concomitant decrease in membrane mismatch between the liquidus and solidus phases.more » « less
-
The intrinsic overexpression of secretory phospholipase A2 (sPLA 2 ) in various pro-inflammatory diseases and cancers has the potential to be exploited as a therapeutic strategy for diagnostics and treatment. To explore this potential and advance our knowledge of the role of sPLA 2 in related diseases, it is necessary to systematically investigate the molecular interaction of the enzyme with lipids. By employing a Langmuir trough integrated with X-ray reflectivity and grazing incidence X-ray diffraction techniques, this study examined the molecular packing structure of 1,2-palmitoyl- sn-glycero -3-phosphocholine (DPPC) films before and after enzyme adsorption and enzyme-catalyzed degradation. Molecular interaction of sPLA 2 (from bee venom) with the DPPC monolayer exhibited Ca 2+ dependence. DPPC molecules at the interface without Ca 2+ retained a monolayer organization; upon adsorption of sPLA 2 to the monolayer the packing became tighter. In contrast, sPLA 2 -catalyzed degradation of DPPC occurred in the presence of Ca 2+ , leading to disruption of the ordered monolayer structure of DPPC. The interfacial film became a mixture of highly ordered multilayer domains of palmitic acid (PA) and loosely packed monolayer phase of 1-palmitoyl-2-hydroxy- sn-glycero -3-phosphocholine (lysoPC) that potentially contained the remaining un-degraded DPPC. The redistribution of lipid degradation products into the third dimension, which produced multilayer PA domains, damaged the structural integrity of the original lipid layer and may explain the bursting of liposomes observed in other studies after a latency period of mixing liposomes with sPLA 2 . A quantitative understanding of the lipid packing and lipid-enzyme interaction provides an intuitive means of designing and optimizing lipid-related drug delivery systems.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acsmacrolett.3c00255
