An official website of the United States government
Charge densities of cationic polymers adsorbed to lipid bilayers are estimated from second harmonic generation (SHG) spectroscopy and quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. The systems surveyed included poly(vinylamine hydrochloride) (PVAm), poly(diallyldimethylammonium chloride) (PDADMAC), poly- l -lysine (PLL), and poly- l -arginine (PLR), as well as polyalcohol controls. Upon accounting for the number of positive charges associated with each polyelectrolyte, the binding constants and apparent free energies of adsorption as estimated from SHG data are comparable despite differences in molecular masses and molecular structure, with Δ G ads values of −61 ± 2, −58 ± 2, −57 ± 1, −52 ± 2, −52 ± 1 kJ mol −1 for PDADMAC 400 , PDADMAC 100 , PVAm, PLL, and PLR, respectively. Moreover, we find charge densities for polymer adlayers of approximately 0.3 C m −2 for poly(diallyldimethylammonium chloride) while those of poly(vinylamine) hydrochloride, poly- l -lysine, and poly- l -arginine are approximately 0.2 C m −2 . Time-dependent studies indicate that polycation adsorption to supported lipid bilayers is only partially reversible for most of the polymers explored. Poly(diallyldimethylammonium chloride) does not demonstrate reversible binding even over long timescales (>8 hours).
more »
« less
This content will become publicly available on September 17, 2026
Shape Transformation of Poly( l -methionine sulfoxide)- b -poly(dehydroalanine) Vesicles
- Award ID(s):
- 2202743
- PAR ID:
- 10636327
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- ACS Macro Letters
- ISSN:
- 2161-1653
- Page Range / eLocation ID:
- 1408 to 1411
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The effect of vortex‐induced mechanical stresses on the fluorescent properties of dye‐containing poly(ethylene glycol)‐block‐poly(lactic acid) (PEG‐b‐PLA) block copolymer micelles has been investigated. PEG‐b‐PLA block copolymer micelles containing fluorescent dyes, 3,3′‐dioctadecyloxacarbocyanine perchlorate (DiO) and/or 1,1′‐dioctadecyl‐3,3,3′,3′‐tetramethylindocarbocyanine perchlorate (DiI), are prepared by a simple one‐step procedure that involves the self‐assembly of block copolymers and spontaneous incorporation of hydrophobic dyes into the core of the micelles. Upon vortexing, the micelle dispersion samples showed a decrease in fluorescence intensity in a rotational speed‐ and time‐dependent manner. The results demonstrated that the vortexing can alter the fluorescent properties of the dye‐containing PEG‐b‐PLA block copolymer micelle dispersion samples, suggesting the potential utility of block copolymer micelles as a mechanical stress‐responsive nanomaterial.more » « less
-
ABSTRACT Crystals of poly(ethylene glycol) grown in thin films of the room temperature ionic liquid (IL) 1‐ethyl‐3‐methylimidazolium ethyl sulfate were examined by electron microscopy as a first step toward exploiting nonvolatile liquids for nanoscale imaging of solvated/dissolved polymeric materials. The crystals were generated by cooling supported (over surfaces of varied polarity) and freestanding solution films to room temperature. This “open,” that is, without liquid cell, microscopy was performed on unstained, as‐grown crystals in the presence of the IL. A variety of nearly two‐dimensional crystal morphologies were observed, including rods, fibers, spherulites, compact faceted single crystals, and interconnected networks, with characteristic sizes ranging from tens of nanometers to tens of microns. Electron diffraction patterns for the rods and fibers revealed single crystal‐like long‐range order. The nature of the IL support little affected the morphology, but film thickness and cooling rate proved important. To assess the role of solvent polarity, crystals were also grown from 1‐ethyl‐3‐methylimidazolium ethyl sulfate mixed with the second IL, the less polar ethyl‐tributyl‐phosphonium diethyl phosphate; here, although the morphologies were similar to those made with pure IL, fibrillar morphologies were more prevalent. © 2020 Wiley Periodicals, Inc. J. Polym. Sci.2020,58, 478–486more » « less
-
We show by extensive experimental characterization combined with molecular simulations that pH has a major impact on the assembly mechanism and properties of poly( l -lysine) (PLL) and poly( l -glutamic acid) (PGA) complexes. A combination of dynamic light scattering (DLS) and laser Doppler velocimetry (LDV) is used to assess the complexation, charge state, and other physical characteristics of the complexes, isothermal titration calorimetry (ITC) is used to examine the complexation thermodynamics, and circular dichroism (CD) is used to extract the polypeptides’ secondary structure. For enhanced analysis and interpretation of the data, analytical ultracentrifugation (AUC) is used to define the precise molecular weights and solution association of the peptides. Molecular dynamics simulations reveal the associated intra- and intermolecular binding changes in terms of intrinsic vs. extrinsic charge compensation, the role of hydrogen bonding, and secondary structure changes, aiding in the interpretation of the experimental data. We combine the data to reveal the pH dependency of PLL/PGA complexation and the associated molecular level mechanisms. This work shows that not only pH provides a means to control complex formation but also that the associated changes in the secondary structure and binding conformation can be systematically used to control materials assembly. This gives access to rational design of peptide materials via pH control.more » « less
