Ions induce changes in the H-bond network of water that extend by >20 nm, vary for H 2 O and D O, lead to surface tension anomalies.

Ion-specific effects on salting-in and salting-out of proteins, protein denaturation, as well enzymatic activity are typically rationalized in terms the Hofmeister series. Here, we demonstrate by means NMR spectroscopy molecular dynamics simulations that traditional explanation ordering ions their bulk hydration properties is inadequate. Using triglycine a model system, show series for anions changes from direct to reversed upon uncapping N-terminus. Weakly hydrated anions, such iodide...

We investigated salt interactions with butyramide as a simple mimic of cation protein backbones. The experiments were performed in aqueous metal chloride solutions using two spectroscopic techniques. In the first, which provided information about contact pair formation, response amide I band to nature and concentration was monitored bulk via attenuated total reflection Fourier transform infrared spectroscopy. It found that molar concentrations well-hydrated cations (Ca(2+), Mg(2+), Li(+))...

Imaging surfaces with water The of real materials are often highly chemically heterogeneous, and the reported values even simple properties such as surface acidity can vary widely in many cases. Macias-Romero et al. developed a microscope that images on basis second-harmonic generation from orientation interfacial (see Perspective by Hunger Parekh). They followed deprotonation silica along glass micropipettes changing solution pH found regions where deviated strongly average for entire...

Ion identity and concentration influence the solubility of macromolecules. To date, substantial effort has been focused on obtaining a molecular level understanding specific effects for anions. By contrast, role cations received significantly less attention underlying mechanisms by which interact with macromolecules remain more elusive. address this issue, poly(N-isopropylacrylamide), thermoresponsive polymer an amide moiety its side chain, was studied in aqueous solutions series nine...

A combination of Fourier transform infrared and phase transition measurements as well molecular computer simulations, thermodynamic modeling were performed to probe the mechanisms by which guanidinium (Gnd+) salts influence stability collapsed versus uncollapsed state an elastin-like polypeptide (ELP), uncharged thermoresponsive polymer. We found that cation's action was highly dependent upon counteranion with it paired. Specifically, Gnd+ depleted from ELP/water interface stabilize...

Herein, we use a combination of thermodynamic and spectroscopic measurements to investigate the interactions Hofmeister anions with thermoresponsive polymer, poly(N,N-diethylacrylamide) (PDEA). This amide-based polymer does not contain an NH moiety in its chemical structure and, thus, can serve as model test if bind amides absence site. The lower critical solution temperature (LCST) PDEA was measured function concentration for 11 sodium salts aqueous solutions, followed direct series ability...

Mixtures of nano- and microscopic oil droplets in water have recently been rediscovered as miniature reaction vessels microfluidic environments are important constituents many environmental systems, food, personal care, medical products. The nanodroplet/water interface stabilized by surfactants determines the physicochemical properties droplets. Surfactants thought to stabilize nanodroplets forming densely packed monolayers that shield phase from water. This idea has inferred droplet...

Variations between the inner and outer leaflets of cell membranes are crucial for functioning signaling, drug-membrane interactions, formation lipid domains. Transmembrane asymmetry can in principle be comprised an asymmetric charge distribution, differences hydration, specific headgroup/H-bonding or a difference number lipids per leaflet. Here, we characterize transmembrane small unilamellar liposomes consisting zwitterionic charged aqueous solution using vibrational sum frequency...

The specific ion effect (SIE), the control of polymer solubility in aqueous solutions by added ions, has been a phenomenon known for more than century. seemingly simple nature ion–polymer–water interactions can lead to complex behaviors, which have also exploited many applications biochemistry, electrochemistry, and energy harvesting. Here, we show an emerging diversification actuation behaviors "salty" hydrogel hydrogel-paper actuators. SIE controls not only dehydration speeds but water...

The surface tension of electrolyte solutions exhibits a minimum at millimolar concentrations and then rises with increasing concentration. This minimum, known as the Jones-Ray effect, has been hotly debated over past ∼80 years. If not considered an artifact, it is typically ascribed to phenomenological rare binding site for ions or ion pairs. Here, we propose alternative underlying mechanism, namely that hydrogen bond network water responds collective electrostatic field by its orientational...

A three-dimensional-phospholipid monolayer with tunable molecular structure was created on the surface of oil nanodroplets from a mixture phospholipids, oil, and water. This simple nanoemulsion preparation technique generates an in situ prepared membrane model system controllable properties that resembles lipid droplet. The interfacial such nanoscopic composed hexadecane, 1,2-dihexadecanoyl-sn-glycero-3-phosphocholine (DPPC), water determined using vibrational sum frequency scattering second...

Specific ion effects in aqueous solutions are investigated at the molecular, nanoscopic and macroscopic levels. Femtosecond elastic second harmonic scattering (fs-ESHS) is used here to assess chemical of ions on molecular length scales water, probing changes charge distribution around as well structural orientational order water molecules extended hydration shells. We measured >0.05 M electrolyte with a series chloride salts (LiCl, NaCl, KCl, CsCl, RbCl, NH4Cl, MgCl2, CaCl2, SrCl2). Ion...

Cell membranes are composed of a hydrated lipid bilayer that is molecularly complex and diverse, the link between molecular hydration structure membrane macroscopic properties not well understood, due to lack technology can probe relate level information micro- properties. Here, we demonstrate direct dynamic curvature fluctuations. Using high-throughput wide-field second harmonic (SH) microscopy, observe formation transient domains ordered water at interface freestanding membranes. These...

Hydrophobic oil droplets, particles, and air bubbles can be dispersed in water as kinetically stabilized dispersions. It has been established since the 19th century that such objects harbor a negative electrostatic potential roughly twice larger than thermal energy. The source of this charge continues to one core observations relation hydrophobicity, its molecular explanation is still debated. What clear though stabilizing interaction these systems understood terms repulsion via Derjaguin,...

Polyelectrolytes induce long-range order in water that correlates with viscosity changes.

The molecular structure of zwitterionic and charged monolayers on small oil droplets in aqueous solutions is determined using a combined second harmonic sum frequency study. From the interfacial vibrational signature acyl chains phosphate headgroups as well response hydrating water, we find that lipids with identical form remarkably different monolayers. Zwitterionic phospholipids closely packed monolayer highly ordered tails. In contrast, low number density disordered are oriented...

The interaction of ions with interfaces influences numerous processes in chemistry, physics, and biology, while different ion species behave differently at hydrophobic or hydrophilic interfaces. Despite its importance, specificity relation to stability such are not understood on the molecular interfacial level, particular when dimension approaches submicron length scale. To study mechanism involved nanoscale specificity, we use a hexadecane nanodroplet system stabilized dilute monolayer...

Significance Concentrated liquid formulations of therapeutic antibodies are susceptible to colloidal instability, including liquid–liquid phase separation (LLPS). Herein, we measure the kinetics aqueous two-phase system (ATPS) formation, macroscopic stage LLPS, along a linear temperature gradient device. These studies indicate that ATPS formation proceeds by growth protein-rich droplets and their subsequent coalescence. Droplet accelerates as solution is cooled because protein–protein...

Hyaluronan enhances the orientational order of water over up to 475 nm in its extended hydration shells.

Ions influence the solution properties of macromolecules. Although much is known about anions, cationic effects are considered mostly in terms weak interactions or exclusion from neutral interfaces. Herein, we have systematically studied effect quaternary tetraalkylammonium cations (NH4+, NMe4+, NEt4+, NPr4+, NBu4+) on phase transition poly(N-isopropylacrylamide) (PNIPAM) aqueous solution. Solubility measurements were coupled to 1H NMR and ATR-FTIR spectroscopic measurements. The solubility...