The Salt-Induced Diffusiophoresis of Nonionic Micelles-Does the Salt-Induced Growth of Micelles Influence Diffusiophoresis?

Salt-induced diffusiophoresis is the migration of a colloidal particle in water due to a directional salt concentration gradient. An important example of colloidal particles is represented by micelles, generated by surfactant self-assembly in water. For non-ionic surfactants containing polyethylene glycol (PEG) groups, PEG preferential hydration at the micelle-water interface is expected to drive micelle diffusiophoresis from high to low salt concentration.

Diffusiophoresis of Macromolecules within the Framework of Multicomponent Diffusion.

Diffusiophoresis is the isothermal migration of a colloidal particle through a liquid caused by a cosolute concentration gradient. Although diffusiophoresis was originally introduced using hydrodynamics, it can also be described by employing the framework of multicomponent diffusion. This not only enables the extraction of diffusiophoresis coefficients from measured multicomponent-diffusion coefficients but also their theoretical interpretation using fundamental thermodynamic and transport parameters.

Proton Affinity and Conformational Integrity of a 24-Atom Triazine Macrocycle across Physiologically Relevant pH.

For 24-atom triazine macrocycles, protonation of the heterocycle leads to a rigid, folded structure presenting a network of hydrogen bonds. These molecules derive from dynamic covalent chemistry wherein triazine monomers bearing a protected hydrazine group and acetal tethered by the amino acid dimerize quantitatively in an acidic solution. Here, lysine is used, and the product is a tetracation.

Diffusiophoresis of a Nonionic Micelle in Salt Gradients; Roles of Preferential Hydration and Salt-Induced Surfactant Aggregation.

Diffusiophoresis is the migration of a colloidal particle in water driven by concentration gradients of cosolutes such as salts. We have experimentally characterized the diffusiophoresis of tyloxapol micelles in the presence of MgSO, a strong salting-out agent. Specifically, we determined the multicomponent-diffusion coefficients using Rayleigh interferometry, cloud points, and dynamic-light-scattering diffusion coefficients on the ternary tyloxapol-MgSO-water system at 25 °C.

Effect of a Good buffer on the fate of metastable protein-rich droplets near physiological composition.

Metastable protein-rich microdroplets are produced from liquid-liquid phase separation (LLPS) of protein aqueous solutions. These globules can be intermediates for the formation of other protein-rich phases. Lysozyme aqueous solutions undergo LLPS around 0 °C in the presence of NaCl near physiological conditions.

Determination of Critical Micelle Concentration from the Diffusion-Driven Dilution of Micellar Aqueous Mixtures.

Micellization is a phenomenon of central importance in surfactant solutions. Here, we demonstrate that the diffusion-based spreading of the free boundary between a micellar aqueous solution and pure water yields a one-dimensional spatial profile of surfactant concentration that can be used to identify the critical micelle concentration, here denoted as *. This can be achieved because dilution of micelles into water leads to their dissociation at a well-defined position along the concentration profile and an abrupt increase in the diffusion coefficient.

Amplification of Salt-Induced Protein Diffusiophoresis by Varying Salt from Potassium to Sodium to Magnesium Chloride in Water.

Salt-induced diffusiophoresis is the migration of a macromolecule or a colloidal particle induced by a concentration gradient of salt in water. Here, the effect of salt type on salt-induced diffusiophoresis of the protein lysozyme at pH 4.5 and 25 °C was examined as a function of salt concentration for three chloride salts: NaCl, KCl, and MgCl.

Hexadecyl-Containing Organic Salts as Novel Organogelators for Ionic, Eutectic, and Molecular Liquids.

The incorporation of a hexadecyl group on imidazolium, pyridinium, and pyrrolidinium scaffolds produces low-molecular-weight ionic organogelators that can gel several types of ionic liquids, deep eutectic solvents (DESs), and several molecular organic solvents. Minimum gelator concentrations fall in the 0.9-15.

Macromolecule Diffusiophoresis Induced by Concentration Gradients of Aqueous Osmolytes.

Diffusiophoresis is the migration of a particle in a fluid induced by the concentration gradient of another solute. We have experimentally investigated diffusiophoresis of a neutral macromolecule, poly(ethylene glycol) (PEG; molecular weight, 20 kg mol), in water induced by concentration gradients of osmolytes. Three osmolytes were examined: trimethylamine- N-oxide (TMAO), diethylene glycol (DEG), and urea.

Formation of Dendrimer Nanoassemblies by Oligomerization-Induced Liquid-Liquid Phase Separation.

Dendrimers are hyperbranched macromolecules with applications in host-guest chemistry, self-assembly, nanocatalysis, and nanomedicine. We show that dendrimer-based globular nanoparticles are formed by using dendrimer oligomerization to isothermally induce liquid-liquid phase separation (LLPS). We first determined that LLPS of aqueous mixtures of the fourth-generation amino-functionalized poly(amido amine) dendrimer is observed by lowering temperature in the presence of sodium sulfate.

Thermoregulated Coacervation, Metal-Encapsulation and Nanoparticle Synthesis in Novel Triazine Dendrimers.

The synthesis and solubility behaviors of four generation five (G5) triazine dendrimers are studied. While the underivatized cationic dendrimer is soluble in water, the acetylated and propanoylated derivatives undergo coacervation in water upon increasing temperature. Occurring around room temperature, this behavior is related to a liquid-liquid phase transition with a lower critical solution temperature (LCST) and is explained by differences in composition, notably, the hydrophobic nature of the terminal groups.

Interaction of BODIPY dyes with bovine serum albumin: a case study on the aggregation of a click-BODIPY dye.

The fluorescence of BODIPY and click-BODIPY dyes was found to substantially increase in the presence of bovine serum albumin (BSA). BSA acted as a solubilizer for dye aggregates, in addition to being a conventional binding scaffold for the click-BODIPY dyes, indicating that disaggregation of fluorophores should be considered when evaluating dye-protein interactions.

Unusual liquid-liquid phase transition in aqueous mixtures of a well-known dendrimer.

Liquid-liquid phase separation (LLPS) has been extensively investigated for polymer and protein solutions due to its importance in mixture thermodynamics, separation science and self-assembly processes. However, to date, no experimental studies have been reported on LLPS of dendrimer solutions. Here, it is shown that LLPS of aqueous solutions containing a hydroxyl-functionalized poly(amido amine) dendrimer of fourth generation is induced in the presence of sodium sulfate.

Effects of salting-in interactions on macromolecule diffusiophoresis and salt osmotic diffusion.

Macromolecule diffusiophoresis (i.e., macromolecule migration induced by a salt concentration gradient) in water and salt osmotic diffusion (i.

Amplification of salt-induced polymer diffusiophoresis by increasing salting-out strength.

The role of salting-out strength on (1) polymer diffusiophoresis from high to low salt concentration, and (2) salt osmotic diffusion from high to low polymer concentration was investigated. These two cross-diffusion phenomena were experimentally characterized by Rayleigh interferometry at 25 °C. Specifically, we report ternary diffusion coefficients for polyethylene glycol (molecular weight, 20 kg·mol(-1)) in aqueous solutions of several salts (NaCl, KCl, NH4Cl, CaCl2, and Na2SO4) as a function of salt concentration at low polymer concentration (0.

Bimodal-hybrid heterocyclic amine targeting oxidative pathways and copper mis-regulation in Alzheimer's disease.

Oxidative stress resulting from metal-ion misregulation plays a role in the development of Alzheimer's disease (AD). This process includes the production of tissue-damaging reactive oxygen species and amyloid aggregates. Herein we describe the synthesis, characterization and protective capacity of the small molecule, lipoic cyclen, which has been designed to target molecular features of AD.

Effect of particle size on salt-induced diffusiophoresis compared to Brownian mobility.

For ternary polymer-salt-water systems at low polymer concentration (0.5%, w/w), we have experimentally investigated the effect of polymer size on polymer diffusiophoresis (i.e.

Design, synthesis and biological assessment of a triazine dendrimer with approximately 16 Paclitaxel groups and 8 PEG groups.

The synthesis and characterization of a generation three triazine dendrimer that displays a phenolic group at the core for labeling, up to eight 5 kDa PEG chains for solubility, and 16 paclitaxel groups is described. Three different diamine linkers--dipiperidine trismethylene, piperazine, and aminomethylpiperidine--were used within the dendrimer. To generate the desired stoichiometric ratio of 8 PEG chains to 16 paclitaxel groups, a monochlorotriazine was prepared with two paclitaxel groups attached through their 2'-hydroxyls using a linker containing a labile disulfide.

Synthesis of large dendrimers with the dimensions of small viruses.

The dendrimer chemistry reported offers a route to synthetic target molecules with spherical shape, well-defined surface chemistries, and dimensions that match the size of virus particles. The largest target, a generation-13 dendrimer comprising triazines linked by diamines, is stable across ranges of concentration, pH, temperature, solvent polarity and in the presence of additives. This dendrimer theoretically presents 16,384 surface groups and has a molecular weight exceeding 8.

Protein diffusiophoresis and salt osmotic diffusion in aqueous solutions.

Diffusion of a solute can be induced by the concentration gradient of another solute in solution. This transport mechanism is known as cross-diffusion. We have investigated cross-diffusion in a ternary protein-salt-water system.

Rationally-designed fluorescent lysine riboswitch probes.

Two fluorescent lysine amide analogs, in which the carboxyl end of lysine was covalently attached to dansyl or NBD groups through an ethylene glycol-based linker, were rationally designed and synthesized. Both probes showed high binding affinity to the lysine riboswitch in vitro and their fluorescence intensities decreased by riboswitch binding.

Experimental and computational evidence for an inversion in guest capacity in high-generation triazine dendrimer hosts.

The synthesis, characterization, and host-guest chemistry of high-generation triazine dendrimers are described. With pyrene and camptothecin as guests, experiments revealed that the guest capacity of odd-generation triazine dendrimers increased until generation 7 but decreased at generation 9. Molecular dynamics simulations conducted in explicit solvent showed a useful fingerprint for this behavior in radial distribution functions of water molecules penetrating the interior of the dendrimers.

Macromolecular hydration compared with preferential hydration and their role on macromolecule-osmolyte coupled diffusion.

Hydration and preferential hydration of macromolecules are two distinct properties of their multicomponent aqueous solutions. We have experimentally investigated ternary diffusion in a macromolecule-osmolyte-water system in order to characterize and compare these two independent quantities and to experimentally establish their role on the phenomenon of coupled diffusion. Specifically, we report the four diffusion coefficients for the poly(ethylene glycol)-di(ethylene glycol)-water system at 25 degrees C using Rayleigh interferometry.

Quaternary diffusion coefficients in a protein-polymer-salt-water system determined by rayleigh interferometry.

We have experimentally investigated multicomponent diffusion in a protein-polymer-salt-water quaternary system. Specifically, we have measured the nine multicomponent diffusion coefficients, D(ij), for the lysozyme-poly(ethylene glycol)-NaCl-water system at pH 4.5 and 25 degrees C using precision Rayleigh interferometry.

Diffusion of an ionic drug in micellar aqueous solutions.

Supramolecular carriers such as micelles can be used to noncovalently bind drug molecules for pharmaceutical applications. However, these carriers can fundamentally affect diffusion-based drug transport due to host-guest coupled diffusion. We report a ternary interdiffusion study on an ionic drug in aqueous micellar solutions.