Search

The c-Jun N-terminal kinases (JNKs), with its members JNK1, JNK2, and JNK3, is a subfamily of (MAPK) mitogen-activated protein kinases. JNK signaling regulates a wide range of cellular processes, including cell proliferation, differentiation, survival, apoptosis, and inflammation. Dysregulation of JNK pathway is associated with a wide range of immune disorders and cancer. Our objective is to provide a review of JNK proteins and their upstream regulators and downstream effector molecules in common skin disorders, including psoriasis, dermal fibrosis, scleroderma, basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma.

Melanoma, the most threatening form of skin cancer, has a very poor prognosis and is characterized by its very invasive and chemoresistant properties. Despite the recent promising news from the field of immunotherapy, there is an urgent need for new therapeutic approaches that are free of resistance mechanisms and side effects. Anti-neoplasic properties have been highlighted for different disintegrins from snake venom including Lebein; however, the exact effect of Lebein on melanoma has not yet been defined. In this study, we showed that Lebein blocks melanoma cell proliferation and induces a more differentiated phenotype with inhibition of extracellular signal-regulated kinase (ERK) phosphorylation and microphthalmia-associated transcription factor (MITF) overexpression. Melanoma cells became detached but were less invasive with upregulation of E-cadherin after Lebein exposure. Lebein induced a caspase-independent apoptotic program with apoptosis inducing factor (AIF), BCL-2-associated X protein (BAX) and Bim overexpression together with downregulation of B-cell lymphoma-2 (BCL-2). It generated a distinct response in reactive oxygen species (ROS) generation and p53 levels depending on the p53 cell line status (wild type or mutant). Therefore, we propose Lebein as a new candidate for development of potential therapies for melanoma.

Personal care products commonly contain perfume mixtures, consisting of numerous perfume raw materials (PRMs), and cosolvents. The lipophilicity and structure of an individual PRM is known to affect its localization within the surfactant self-assembly as well as the micellar geometry. However, because multiple PRMs are used in formulations, significant intermolecular interactions between the PRMs and between the PRMs and the surfactant tail may also influence the location of the PRMs and their effects on the self-assembly. Herein, two anionic/zwitterionic mixed-surfactant systems (sodium trideceth-2 sulfate (ST2S)/cocamidopropyl betaine (CAPB) and sodium laureth-3 sulfate/CAPB) were formulated with a cosolvent (dipropylene glycol (DPG)) and 12 PRMs of varying structures and lipophilicities. This 12 PRM accord is simpler than a fully formulated perfume but more complex than a single perfume molecule. The geometric variations in the self-assemblies were evaluated using small-angle neutron scattering, perfume head space concentrations were determined using gas chromatography-mass spectrometry, and perfume localization was identified using NMR spectroscopy. The addition of the perfume accord caused enlargement of the micelles in both surfactant systems, with a greater change observed for ST2S/CAPB formulations. Furthermore, the addition of DPG to ST2S/CAPB resulted in micelle shrinkage. The micelle geometries and PRM localization in the micelles were affected by the degree of branching in the surfactant tail., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Perfume mixtures contain perfume raw materials (PRMs) with varying structures and hydrophobicities, which influence PRM localization within a surfactant-based formulation and thereby affect the phase behavior. In rinse-off products, the addition of water can further affect the phase behavior. In this study, a mixture of 12 PRMs was used as the oil phase in an aqueous system consisting of sodium trideceth-2 sulfate as a primary surfactant, cocamidopropyl betaine as a cosurfactant, and dipropylene glycol as a cosolvent. A series of phase diagrams were constructed with increasing water content, simulating the use conditions for rinse-off products, to determine how the phase boundaries shift with dilution. Using these phase diagrams, the compositions of interest in the micelle without perfume, micelle with perfume, microemulsion, and micelle-microemulsion transition regions were identified at each dilution level. The structural changes were probed through combined small-angle neutron scattering (SANS) and cryo-transmission electron microscopy analyses. The SANS results showed that ellipsoidal micelles were maintained as the perfume content and the dilution level increased. With ≥50 wt % water, increasing the perfume content increased the micelle volume. Interestingly, a higher rate of volume increase was observed at ≥70 wt % water. Notably, the volumes of the micelles with and without perfume increased steadily with dilution, whereas the volumes of the assemblies in the transition region and the microemulsion region increased more rapidly once diluted to 70 and 80 wt % water, respectively.

Hydrogels are of intense recent interest in connection with biomedical applications ranging from 3-D cell cultures and stem cell differentiation to regenerative medicine, controlled drug delivery and tissue engineering. This prototypical form of soft matter has many emerging material science applications outside the medical field. The physical processes underlying this type of solidification are incompletely understood and this limits design efforts aimed at optimizing these materials for applications. We address this general problem by applying multiple techniques (e.g., NMR, dynamic light scattering, small angle neutron scattering, rheological measurements) to the case of a peptide derivative hydrogelator (molecule 1 , NapFFKYp) over a broad range of concentration and temperature to characterize both the formation of individual nanofibers and the fiber network. We believe that a better understanding of the hierarchical self-assembly process and control over the final morphology of this kind of material should have broad significance for biological and medicinal applications utilizing hydrogels.

The form factors for star-branched polymers with linear branches or with looping branches are calculated. The effect of chain swelling excluded volume is incorporated through an excluded volume parameter approach. The form factor for ring polymers is also included, since it is nicely derived as a special case. Furthermore, the form factor for dendrimers with excluded volume is also calculated. In order to evaluate the form factor for stars with looping branches, the multivariate Gaussian function is used to close the looping branches. Analytical results are possible in the Gaussian chain case (i.e., with no excluded volume), but the calculations are left in a form involving summations over monomers when the general case incorporates excluded volume.

Surfactant solutions typically feature tunable nanoscale, internal structures. Although rarely utilized, they can be a powerful platform for probing thermal transport in nanoscale domains and across interfaces with nanometer-size radius. Here, we examine the structure and thermal transport in solution of AOT (Dioctyl sodium sulfosuccinate) in n-octane liquids using small-angle neutron scattering, thermal conductivity measurements, and molecular dynamics simulations. We report the first experimental observation of a minimum thermal conductivity occurring at the critical micelle concentration (CMC): the thermal conductivity of the surfactant solution decreases as AOT is added till the onset of micellization but increases as more AOT is added. The decrease of thermal conductivity with AOT loading in solutions in which AOT molecules are dispersed as monomers suggests that even the interfaces between individual oleophobic headgroup of AOT molecules and their surrounding non-polar octane molecules can hinder heat transfer. The increase of thermal conductivity with AOT loading after the onset of micellization indicates that the thermal transport in the core of AOT micelles and across the surfactant-oil interfaces, both of which span only a few nanometers, are efficient.

The structure and size of ligands attached to the surfaces of gold nanorods, such as adsorbed surfactants or grafted polymers, are important considerations that facilitate the use of such nanoparticles in the human body, in advanced materials for energy harvesting, or in devices for single molecule detection. Here, we report small-angle neutron scattering (SANS) measurements from surfactant or poly(ethylene glycol) (PEG) coated gold nanorods in solution, which quantitatively determine the location, structure, and composition of these surface layers. In addition, by synthesizing gold nanorods using seed crystals which are coated with deuterated cetyltrimethylammonium bromide (dCTAB), we are able to exploit the isotopic sensitivity of SANS to study, for the first time, the retention of surfactant from the seed crystals to the final gold nanorod product, finding that very little exchange of the deuterated with hydrogenated surfactant occurs. Finally, we demonstrate that, when Au NRs are PEGylated using standard techniques, the surfactant bilayer remains intact, and while mass spectrometry detects the presence of both surfactant and PEG, the composition as measured from SANS is predominantly that of the surfactant. These measurements not only provide new insight into the synthesis and functionalization of gold nanorods but provide a quantitative picture of the structure of grafted polymer and surfactant layers on gold nanorod surfaces which has implications for the fabrication of plasmonic and biomedical materials.

Our recent investigation of the three regions of the phase diagram of 17R4 in D2O (Huff et al., 2011) has led us to study the copolymer structure in this system by small-angle neutron scattering, rheometry, and dynamic light scattering. In region I at low temperatures and copolymer concentrations (0-30°C, 0.1-0.2 mass fraction ω), the cloudy solution contains the copolymer in large clusters made of hydrophobic PPO-rich "knots" bridged by dissolved hydrophilic PEO chains. These clusters vanish in region I at the lower temperatures and concentrations (below 39°C and ω=0.01). In region I over long times (weeks) at 25°C, a white liquid/gel film forms at the air-D2O interface. In region II at temperatures above the micellization line (above about 35°C, at ω=0.22) the large clusters dissipate and unimers coexist with "flower micelles," where the PPO blocks are the centers of the micelles and the PEO blocks loop into the solvent. In region III at still higher temperatures (above about 40°C at ω=0.2), the solution separates into coexisting liquid phases, where the upper phase of higher copolymer concentration is in region II, and the lower phase is in region I. The concentrated upper phase may contain micelles so crowded as to form a network., (Copyright © 2014 Elsevier Inc. All rights reserved.)

We explore the phase behaviour, solution conformation, and interfacial properties of bottlebrush polymers with side-chains comprised of poly(N-isopropylacrylamide) (PNIPAAM), a thermally responsive polymer that exhibits a lower critical solution temperature (LCST) in water. PNIPAAM bottlebrush polymers with controlled side-chain length and side-chain end-group structure are prepared using a "grafting-through" technique. Due to reduced flexibility of bottlebrush polymer side-chains, side-chain end-groups have a disproportionate effect on bottlebrush polymer solubility and phase behaviour. Bottlebrush polymers with a hydrophobic end-group have poor water solubilities and depressed LCSTs, whereas bottlebrush polymers with thiol-terminated side-chains are fully water-soluble and exhibit an LCST greater than that of PNIPAAM homopolymers. The temperature-dependent solution conformation of PNIPAAM bottlebrush polymers in D2O is analyzed by small-angle neutron scattering (SANS), and data analysis using the Guinier-Porod model shows that the bottlebrush polymer radius decreases as the temperature increases towards the LCST for PNIPAAM bottlebrush polymers with relatively long 9 kg mol(-1) side-chains. Above the LCST, PNIPAAM bottlebrush polymers can form a lyotropic liquid crystal phase in water. Interfacial tension measurements show that bottlebrush polymers reduce the interfacial tension between chloroform and water to levels comparable to PNIPAAM homopolymers without the formation of microemulsions, suggesting that bottlebrush polymers are unable to stabilize highly curved interfaces. These results demonstrate that bottlebrush polymer side-chain length and flexibility impact phase behavior, solubility, and interfacial properties.

It is common practice to assume that Bragg scattering peaks have Gaussian shape. The Gaussian shape function is used to perform most instrumental smearing corrections. Using Monte Carlo ray tracing simulation, the resolution of a realistic small-angle neutron scattering (SANS) instrument is generated reliably. Including a single-crystal sample with large d-spacing, Bragg peaks are produced. Bragg peaks contain contributions from the resolution function and from spread in the sample structure. Results show that Bragg peaks are Gaussian in the resolution-limited condition (with negligible sample spread) while this is not the case when spread in the sample structure is non-negligible. When sample spread contributes, the exponentially modified Gaussian function is a better account of the Bragg peak shape. This function is characterized by a non-zero third moment (skewness) which makes Bragg peaks asymmetric for broad neutron wavelength spreads.

The effect of nanoparticles (NP) on chain dimensions in polymer melts has been the source of considerable theoretical and experimental controversy. We exploit our ability to ensure a spatially uniform dispersion of 13 nm silica NPs miscible in polystyrene melts, together with neutron scattering, x-ray scattering, and transmission electron microscopy, to show that there is no measurable change in the polymer size in miscible mixtures, regardless of the relative sizes of the chains and the nanoparticles, and for NP loadings as high as 32.7 vol%. Our results provide a firm basis from which to understand the properties of polymer nanocomposites.

Sodium dodecyl sulfate (SDS) surfactants form micelles when dissolved in water. These are formed of a hydrocarbon core and hydrophilic ionic surface. The small-angle neutron scattering (SANS) technique was used with deuterated water (D2O) in order to characterize the micelle structure. Micelles were found to be slightly compressed (oblate ellipsoids) and their sizes shrink with increasing temperature. Fits of SANS data to the Mean Spherical Approximation (MSA) model yielded a calculated micelle volume fraction which was lower than the SDS surfactant (sample mixing) volume fraction; this suggests that part of the SDS molecules do not participate in micelle formation and remain homogeneously mixed in the solvent. A set of material balance equations allowed the estimation of the SDS fraction in the micelles. This fraction was found to be high (close to one) except for samples around 1 % SDS fraction. The micelle aggregation number was found to decrease with increasing temperature and/or decreasing SDS fraction.

Small amphiphilic molecules, also known as hydrotropes, are too small to form micelles in aqueous solutions. However, aqueous solutions of nonionic hydrotropes show the presence of a dynamic, loose, non-covalent clustering in the water-rich region, This clustering can be viewed as "micelle-like structural fluctuations". Although these fluctuations are short ranged (approximately 1 nm) and short lived (10 ps-50 ps), they may lead to thermodynamic anomalies. In addition, many experiments on aqueous solutions of hydrotropes show the occasional presence of mesoscale (approximately 100 nm) inhomogeneities. We have combined results obtained from molecular dynamics simulations, small-angle neutron scattering, and dynamic light-scattering experiments carried out on tertiary butyl alcohol (hydrotrope)-water solutions and on tertiary butyl alcohol-water-cyclohexane (hydrophobe) solutions to elucidate the nature and structure of these inhomogeneities. We have shown that stable mesoscale inhomogeneities occur in aqueous solutions of nonionic hydrotropes only when the solution contains a third, more hydrophobic, component. Moreover, these inhomogeneities exist in ternary systems only in the concentration range where structural fluctuations and thermodynamic anomalies are observed in the binary water-hydrotrope solutions. Addition of a hydrophobe seems to stabilize the water-hydrotrope structural fluctuations, and leads to the formation of larger (mesoscopic) droplets. The structure of these mesoscopic droplets is such that they have a hydrophobe-rich core, surrounded by a hydrogen-bonded shell of water and hydrotrope molecules. These droplets can be extremely long-lived, being stable for over a year. We refer to the phenomenon of formation of mesoscopic droplets in aqueous solutions of nonionic hydrotropes containing hydrophobes, as mesoscale solubilization. This phenomenon may represent a ubiquitous feature of nonionic hydrotropes that exhibit clustering in water, and may have important practical applications in areas, such as drug delivery, where the replacement of traditional surfactants may be necessary.

The origin and the effects of homochirality in the biological world continuously stimulate numerous hypotheses and much debate. This work attempts to look at the biohomochirality issue from a different angle-the mechanical properties of the bulk biomaterial and their relation to nanoscale structures. Using a pair of oppositely charged peptides that co-assemble into hydrogels, we systematically investigated the effect of chirality on the mechanical properties of these hydrogels through different combinations of syndiotactic and isotactic peptides. It was found that homochirality confers mechanical advantage, resulting in higher elastic modulus and strain yield value. Yet, heterochirality confer kinetic advantage, resulting in faster gelation. Structurally, both homochiral and heterochiral hydrogels are made of fibers interconnected by lappet-like webs, but the homochiral peptide fibers are thicker and denser. The result highlights the possible role of biohomochirality in the evolution and/or natural selection of biomaterials.

Biocompatible and biodegradable peptide hydrogels are drawing increasing attention as prospective materials for human soft tissue repair and replacement. To improve the rather unfavorable mechanical properties of our pure peptide hydrogels, in this work we examined the possibility of creating a double hydrogel network. This network was created by means of the coassembly of mutually attractive, but self-repulsive oligopeptides within an already-existing fibrous network formed by the charged, biocompatible polysaccharides chitosan, alginate, and chondroitin. Using dynamic oscillatory rheology experiments, it was found that the coassembly of the peptides within the existing polysaccharide network resulted in a less stiff material as compared to the pure peptide networks (the elastic modulus G' decreased from 90 to 10 kPa). However, these composite oligopeptide-polysaccharide hydrogels were characterized by a greater resistance to deformation (the yield strain γ grew from 4 to 100%). Small-angle neutron scattering (SANS) was used to study the 2D cross-sectional shapes of the fibers, their dimensional characteristics, and the mesh sizes of the fibrous networks. Differences in material structures found with SANS experiments confirmed rheology data, showing that incorporation of the peptides dramatically changed the morphology of the polysaccharide network. The resulting fibers were structurally very similar to those forming the pure peptide networks, but formed less stiff gels because of their markedly greater mesh sizes. Together, these findings suggest an approach for the development of highly deformation-resistant biomaterials., (Copyright © 2011 Wiley Periodicals, Inc.)

Networks made from chitosan and alginate have been utilized as prospective tissue engineering scaffolds due to material biocompatibility and degradability. Calcium (Ca(2+) ) is often added to these networks as a modifier for mechanical strength enhancement. In this work, we examined changes in the bulk material properties of different concentrations of chitosan/alginate mixtures (2, 3, or 5% w/w) upon adding another modifier, chondroitin. We further examined how material properties depend on the order the modifiers, Ca(2+) and chondroitin, were added. It was found that the addition of chondroitin significantly increased the mechanical strength of chitosan/alginate networks. Highest elastic moduli were obtained from samples made with mass fractions of 5% chitosan and alginate, modified by chondroitin first and then Ca(2+) . The elastic moduli in dry and hydrated states were (4.41 ± 0.52) MPa and (0.11 ± 0.01) MPa, respectively. Network porosity and density were slightly dependent on total polysaccharide concentration. Average pore size was slightly larger in samples modified by Ca(2+) first and then chondroitin and in samples made with 3% starting mass fractions. Here, small-angle neutron scattering (SANS) was utilized to examine mesh size of the fibrous networks, mass-fractal parameters and average dimensions of the fiber cross-sections prior to freeze-drying. These studies revealed that addition of Ca(2+) and chondroitin modifiers increased fiber compactness and thickness, respectively. Together these findings are consistent with improved network mechanical properties of the freeze-dried materials., (2011 Wiley Periodicals, Inc.)

Covalent conjugation of poly(ethylene glycol) or "PEGylation" has proven an effective strategy to improve pharmaceutical protein efficacy by hindering recognition by proteases, inhibitors, and antibodies and by retarding renal clearance. Because it determines the strength and range of intermolecular steric forces and the hydrodynamic properties of the conjugates, the configuration of protein-conjugated PEG chains is the key factor determining how PEGylation alters protein in vivo circulation time. Mono-PEGylated proteins are typically described as having a protective PEG shroud wrapped around the protein, but recent dynamic light scattering studies suggested that conjugates adopt a dumbbell configuration, with a relatively unperturbed PEG random coil adjacent to the globular protein. We used small-angle neutron scattering (SANS) to distinguish between the dumbbell model and the shroud model for chicken-egg lysozyme and human growth hormone covalently conjugated to a single 20 kDa PEG chain. The SANS contrast variation technique was used to isolate the PEG portion of the conjugate. Scattering intensity profiles were well described by the dumbbell model and inconsistent with the shroud model.

Author: Because of the closed-loop phase diagram of tetrahydrofuran (THF)-water mixture, THF aqueous solution naturally exhibits concentration fluctuations near the phase boundary. Besides the fast mode induced by concentration fluctuations, the 4.5% mole fraction THF aqueous solution is also characterized by a slow mode. The existence of a trace amount of butylhydroxytoluene (BHT) antioxidant in commercial THF strongly influences the slow mode in 4.5% mole fraction THF aqueous solution. A core-shell structure with a BHT core and a shell made from THF-rich THF-D(2)O mixture was identified by the combination of dynamic laser light scattering (DLS) and small-angle neutron scattering (SANS). BHT is hydrophobic, stabilized by a THF-rich domain in THF aqueous solution and acts as a tracer to make the large-scale structure (slow mode) "visible" through SANS because of its larger contrast with the solvent. In contrast, this large-scale structure was almost not detectable by SANS when BHT was removed from the THF-D(2)O mixture. Combined UV-vis, DLS, and static light scattering (SLS) indicated that slow-moving objects do exist and that their sizes almost do not change, but their concentration decreases to a small but nonzero value at the infinite dilution limit. The origin of the elusive large-scale structure at zero BHT concentration is still not clear, but it might be associated with some hydrophobic impurities or nanobubbles. However, a polydisperse sphere model of ∼8.5% mole fraction THF-D(2)O mixture can fit the structure with a radius of ∼100 nm, which gives the temperature-dependent low-q SANS profiles of 4.5% mole fraction THF aqueous solution at zero BHT concentration.

Very large thermal conductivity enhancement had been reported earlier in colloidal suspensions of solid nanoparticles (i.e., nanofluids) and more recently also in oil-in-water emulsions. In this study, nanoemulsions of alcohol and polyalphaolefin (PAO) are spontaneously generated by self-assembly, and their thermal conductivity and viscosity are investigated experimentally. Alcohol and PAO have similar thermal conductivity values, so that the abnormal effects, such as particle Brownian motion, on thermal transport could be deducted in these alcohol/PAO nanoemulsion fluids. Small angle neutron-scattering measurement shows that the alcohol droplets are spheres of 0.8-nm radius in these nanoemulsion fluids. Both thermal conductivity and dynamic viscosity of the fluids are found to increase with alcohol droplet loading, as expected from classical theories. However, the measured conductivity increase is very moderate, e.g., a 2.3% increase for 9 vol%, in these fluids. This suggests that no anomalous enhancement of thermal conductivity is observed in the alcohol/PAO nanoemulsion fluids tested in this study.

Small-angle neutron scattering was used to examine the effects of molecular crowding on an intrinsically disordered protein, the N protein of bacteriophage λ, in the presence of high concentrations of a small globular protein, bovine pancreatic trypsin inhibitor (BPTI). The N protein was labeled with deuterium, and the D(2)O concentration of the solvent was adjusted to eliminate the scattering contrast between the solvent and unlabeled BPTI, leaving only the scattering signal from the unfolded protein. The scattering profile observed in the absence of BPTI closely matched that predicted for an ensemble of random conformations. With BPTI added to a concentration of 65 mg/mL, there was a clear change in the scattering profile representing an increase in the mass fractal dimension of the unfolded protein, from 1.7 to 1.9, as expected if crowding favors more compact conformations. The crowding protein also inhibited aggregation of the unfolded protein. At 130 mg/mL BPTI, however, the fractal dimension was not significantly different from that measured at the lower concentration, contrary to the predictions of models that treat the unfolded conformations as convex particles. These results are reminiscent of the behavior of polymers in concentrated melts, suggesting that these synthetic mixtures may provide useful insights into the properties of unfolded proteins under crowding conditions., (Copyright © 2011 Biophysical Society. Published by Elsevier Inc. All rights reserved.)

Clustering prevails in water-soluble polymers and biological macromolecules. It has also been observed in polar solvent mixtures. The possible causes of clustering are discussed. A systematic investigation of clustering in poly(ethylene oxide)/d-water solutions has been undertaken using the small-angle neutron scattering method. The poly(ethylene oxide) monomer is formed of an oxygen atom and an ethylene group. Using the random phase approximation, partial Flory-Huggins interaction parameters for the three pairs (oxygen/d-water, ethylene/d-water, and oxygen/ethylene) are derived. Results show that the first two (oxygen/d-water and ethylene/d-water) are characterized by a lower critical solution temperature phase behavior (whereby phase separation occurs upon heating), while the third one (oxygen/ethylene) is characterized by an upper critical solution temperature phase diagram (whereby phase separation occurs upon cooling). It is argued that clustering is caused by the increasing repulsive interaction between oxygen and ethylene for decreasing temperature and increasing polymer volume fraction. This leads to increasing attractive interactions between ethylene groups that stick together.

Pluronics are triblock copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide). Pluronic P85 forms a rich phase behavior when dissolved in water. Unimers are observed at low temperature while micelles form at higher temperatures. Spherical, cylindrical, and lamellar micelles are observed sequentially upon heating. The effect of hydrostatic pressure on the phase boundaries is investigated here using small-angle neutron scattering from a dilute P85 solution in deuterated water. The transition temperatures between these micelle phases are found to rise with increasing pressure. A new phase corresponding to demixed lamellae was observed at high temperature. The effect of pressure was seen to decrease the onset formation line of that new phase.

DNA undergoes a helix-to-coil transition (also called denaturation transition) upon heating. This transition can also be facilitated by using solvent mixtures (for example water-alcohol). An increase in the hydrophobic tail of the second solvent molecule first decreases then increases the melting temperature appreciably. Measurement on 4% DNA in a series of water-alcohol mixtures shows that the helix-to-coil melting transition is driven by the solvent ability to cross the hydrophobic sugar-rich region. DNA is behaving like a cylindrical micelle.

Small-angle neutron scattering and pulsed-field gradient stimulated-echo nuclear magnetic resonance (NMR) have been used to study the structural characteristics of aqueous Pluronic solutions. In particular, changes in the micellar structure upon addition of ibuprofen to the solutions and altering the temperature have been investigated. Increases in temperature and ibuprofen concentration both appear to favor micellization, with increases observed in the aggregation number, fraction of polymer micellized, and core radius of the micelle, along with a decrease in the volume fraction of the solvent in the core. At high drug concentrations and/or temperatures, micelles of the more hydrophobic Pluronics scatter neutrons strongly at low Q, indicating attractive interactions between micelles or a change in the shape of the aggregates. The addition of ibuprofen to Pluronic P104 has also been found to reduce the critical micellization temperature from approximately 20 degrees C to below 13 degrees C. The hydrophobicity of the Pluronic, quantity of ibuprofen present, and temperature of the solution all seem to have a strong influence on the extent and nature of aggregation observed.

Physically cross-linked, fibrillar hydrogel networks are formed by the self-assembly of β-hairpin peptide molecules with varying degrees of strand asymmetry. The peptide registry in the self-assembled state can be used as a design element to generate fibrils with twisting, nontwisting, or laminated morphology. The mass density of the networks varies significantly, and can be directly related to the local fibrillar morphology as evidenced by small angle neutron scattering (SANS) and in situ substantiation using cryogenic transmission electron microscopy (cryo-TEM) under identical concentrations and conditions. Similarly, the density of the network is dependent on changes in the peptide concentration. Bulk rheological properties of the hydrogels can be correlated to the fibrillar nanostructure, with the stiffer, laminated fibrils forming networks with a higher G' as compared to the flexible, singular fibrillar networks.

Small-angle neutron scattering (SANS), cryogenic transmission electron microscopy (cryo-TEM), and dynamic light scattering (DLS) were used to study the metal-dependent phase behavior of microbially produced surfactants-marinobactins B, D, and E (MB, MD, and ME). Marinobactins A-E are siderophores that facilitate Fe(III) acquisition by the source bacterium through the coordination of Fe(III) by the peptidic headgroup. All of the marinobactins have the same six amino acid headgroup but differ in the length and saturation of the monoalkyl fatty acid tail. Fe(III) coordinated to ME (Fe(III)-ME) was found to form micelles with a diameter of approximately 3.5 nm that underwent a supramolecular transformation to produce a monodisperse population of vesicles with an average diameter ranging from approximately 90 to 190 nm upon addition of Cd(II), Zn(II), or La(III). SANS profiles of the transition-metal-induced phase exhibit a Bragg peak at QB approximately 0.11-0.12 A-1 and were fit to a SANS model for multilamellar vesicles that have an interbilayer repeat distance of 2pi/QB approximately 5.6-5.0 nm. Cryo-TEM images of the Zn(II)-induced phase reveals the presence of approximately 100 nm diameter approximately spherical aggregates of uniform electron density. The temperature dependence of the Zn(II)-induced transformation was also investigated as a function of the length and degree of unsaturation of the Fe(III)-marinobactin fatty acid tail. The Cd(II)-, Zn(II)-, and La(III)-induced phase changes have features that are similar to those of the previously reported Fe(III)-induced micelle-to-vesicle transition, and this observation has opened questions regarding the role that Cd(II) and Zn(II) may play in bacterial iron uptake.