Impact of water and oleic acid on glycerol monooleate phase transition and bi-continuous structure formation in white oil.

Production of biofuels from biological feedstocks, such as soybean oil, is an important piece of the transition to renewable energy sources. Processes have been developed to co-refine these feedstocks with traditional feedstocks, however, the high concentration of polar functional groups in biofeedstocks can cause a wide range of intermediate chemical reactions and interactions. An improved understanding of the interactions of biofeedstocks and their degradation products is needed to continue to expand the usage of biofeedstocks in fuel production.

Polyaspartic Acid Concentration Controls the Rate of Calcium Phosphate Nanorod Formation in High Concentration Systems.

Polyelectrolytes are known to greatly affect calcium phosphate (CaP) mineralization. The reaction kinetics as well as the CaP phase, morphology and aggregation state depend on the relative concentrations of the polyelectrolyte and the inorganic ions in a complex, nonlinear manner. This study examines the structural evolution and kinetics of polyaspartic acid (pAsp) directed CaP mineralization at high concentrations of polyelectrolytes, calcium, and total phosphate (19-30 mg/mL pAsp, 50-100 mM Ca, Ca/P = 2).

Kinetics of aggregation and crystallization of polyaspartic Acid stabilized calcium phosphate particles at high concentrations.

Bone is an important material to study due to its exceptional mechanical properties and relevance with respect to hard tissue regeneration and repair. A significant effort has been directed toward understanding the bone formation process and the production of synthetic bone mimicking materials. Here, the formation and structural evolution of calcium phosphate (CaP) was investigated in the presence of relatively high concentrations of calcium, phosphate, and polyaspartic acid (pAsp) using dynamic light scattering (DLS) and cryo-transmission electron microscopy (cryo-TEM).

Phase behavior of electrostatically complexed polyelectrolyte gels using an embedded fluctuation model.

Nanostructured, responsive hydrogels formed due to electrostatic interactions have promise for applications such as drug delivery and tissue mimics. These physically cross-linked hydrogels are composed of an aqueous solution of oppositely charged triblocks with charged end-blocks and neutral, hydrophilic mid-blocks. Due to their electrostatic interactions, the end-blocks microphase separate and form physical cross-links that are bridged by the mid-blocks.

Small angle neutron scattering study of complex coacervate micelles and hydrogels formed from ionic diblock and triblock copolymers.

A complex coacervate is a fluid phase that results from the electrostatic interactions between two oppositely charged macromolecules. The nature of the coacervate core structure of hydrogels and micelles formed from complexation between pairs of diblock or triblock copolymers containing oppositely charged end-blocks as a function of polymer and salt concentration was investigated. Both ABA triblock copolymers of poly[(allyl glycidyl ether)-b-(ethylene oxide)-b-(allyl glycidyl ether)] and analogous poly[(allyl glycidyl ether)-b-(ethylene oxide)] diblock copolymers, which were synthesized to be nearly one-half of the symmetrical triblock copolymers, were studied.

Membrane invaginations facilitate reversible water flux driving tunable iridescence in a dynamic biophotonic system.

Squids have used their tunable iridescence for camouflage and communication for millions of years; materials scientists have more recently looked to them for inspiration to develop new "biologically inspired" adaptive optics. Iridocyte cells produce iridescence through constructive interference of light with intracellular Bragg reflectors. The cell's dynamic control over the apparent lattice constant and dielectric contrast of these multilayer stacks yields the corresponding optical control of brightness and color across the visible spectrum.

pH-triggered self-assembly of biocompatible histamine-functionalized triblock copolymers.

Histamine functionalized poly(allyl glycidyl ether)--poly(ethylene glycol)--poly(allyl glycidyl ether) (PAGE-PEO-PAGE) triblock copolymers represent a new class of physically cross-linked, pH-responsive hydrogels with significant potential for biomedical applications. These telechelic triblock copolymers exhibited abrupt and reversible hydrogelation above pH 7.0 due to a hudrophilic/hydrophobic transition of the histamine units to form a network of hydrophobic domains bridged by a hydrophilic PEO matrix.

Structural effects and lipid membrane interactions of the pH-responsive GALA peptide with fatty acid acylation.

GALA is a pH-responsive, membrane-perturbing peptide designed to fold from a random coil at physiological pH to an amphipathic α-helix under mildly acidic conditions. Because of its pH-activated function, GALA has been sought-after as a component of intracellular drug delivery systems that could actively propel endosomal escape. In this study, we conjugated GALA with lauryl and palmitoyl fatty acid tails as model hydrophobic moieties and examined the physicochemical characteristics and activities of the resulting peptide amphiphiles (PAs).

De novo design of bioactive protein-resembling nanospheres via dendrimer-templated peptide amphiphile assembly.

Self-assembling peptide amphiphiles (PAs) have been extensively used in the development of novel biomaterials. Because of their propensity to form cylindrical micelles, their use is limited in applications where small spherical micelles are desired. Here we present a platform method for controlling the self-assembly of biofunctional PAs into spherical 50 nm particles using dendrimers as shape-directing scaffolds.

Viscosity and interfacial properties in a mussel-inspired adhesive coacervate.

The chemistry of mussel adhesion has commanded the focus of much recent research activity on wet adhesion. By comparison, the equally critical adhesive processing by marine organisms has been little examined. Using a mussel-inspired coacervate formed by mixing a recombinant mussel adhesive protein (fp-151-RGD) with hyaluronic acid (HA), we have examined the nanostructure, viscosity, friction, and interfacial energy of fluid-fluid phase-separated coacervates using the surface forces apparatus and microscopic techniques.

Manipulating micellar environments for enhancing transition metal-catalyzed cross-couplings in water at room temperature.

The remarkable effects of added salts on the properties of aqueous micelles derived from the amphiphile PTS are described. Most notably, Heck reactions run in the presence of NaCl lead to couplings on aryl bromides in water at room temperature. Olefin cross- and ring-closing metathesis reactions run in the presence of small amounts of pH-lowering KHSO(4) are also accelerated, another phenomenon that does not apply to typical processes in organic media.

Effect of the peptide secondary structure on the peptide amphiphile supramolecular structure and interactions.

Bottom-up fabrication of self-assembled nanomaterials requires control over forces and interactions between building blocks. We report here on the formation and architecture of supramolecular structures constructed from two different peptide amphiphiles. Inclusion of four alanines between a 16-mer peptide and a 16 carbon long aliphatic tail resulted in a secondary structure shift of the peptide headgroups from α helices to β sheets.

Internalization of p53(14-29) peptide amphiphiles and subsequent endosomal disruption results in SJSA-1 cell death.

In vivo peptide inhibition of tumor suppressor p53 binding to the protein MDM2 is hampered by inefficient delivery of the peptide. Our approach to couple a hydrophobic lipid-like tail on the inhibitory peptide p53(14-29) allowed its intracellular delivery in vitro, in a panel of different cell lines. The constructed chimeric molecules, termed peptide amphiphiles, further self-assembled into supramolecular structures, identified as elongated wormlike micelles.