Pair correlations that link the hydrophobic and Hofmeister effects.

The Hofmeister effect describes how different ions make solutes more or less hydrophobic. The effect is thought to occur due to structural changes in the solvent induced by the ion's presence, particularly in water. In this study, the structural changes in water due to the presence of ions are investigated by molecular dynamics simulations of various monatomic ions in the SPC/E water model.

From atomic structure to excess entropy: a neutron diffraction and density functional theory study of CaO-Al₂O₃-SiO₂ melts.

Calcium aluminosilicate CaO-Al2O3-SiO2 (CAS) melts with compositions (CaO-SiO2)(x)(Al2O3)(1-x) for x  <  0.5 and (Al2O3)(x)(SiO2)(1-x) for x ≥ 0.5 are studied using neutron diffraction with aerodynamic levitation and density functional theory molecular dynamics modelling.

A numerical model for charge transport and energy conversion of perovskite solar cells.

Based on the continuity equations and Poisson's equation, we developed a numerical model for perovskite solar cells. Due to different working mechanisms, the model for perovskite solar cells differs from that of silicon solar cells and Dye Sensitized Solar Cells. The output voltage and current are calculated differently, and in a manner suited in particular to perovskite organohalides.

Liver glycogen in type 2 diabetic mice is randomly branched as enlarged aggregates with blunted glucose release.

Glycogen is a vital highly branched polymer of glucose that is essential for blood glucose homeostasis. In this article, the structure of liver glycogen from mice is investigated with respect to size distributions, degradation kinetics, and branching structure, complemented by a comparison of normal and diabetic liver glycogen. This is done to screen for differences that may result from disease.

Photovoltaic performance and the energy landscape of CH3NH3PbI3.

Photovoltaic cells with absorbing layers of certain perovskites have power conversion efficiencies up to 20%. Among these materials, CH3NH3PbI3 is widely used. Here we use density-functional theory to calculate the energies and rotational energy barriers of a methylammonium ion in the α or β phase of CH3NH3PbI3 with differently oriented neighbouring methylammonium ions.

The biological function of an insect antifreeze protein simulated by molecular dynamics.

Antifreeze proteins (AFPs) protect certain cold-adapted organisms from freezing to death by selectively adsorbing to internal ice crystals and inhibiting ice propagation. The molecular details of AFP adsorption-inhibition is uncertain but is proposed to involve the Gibbs-Thomson effect. Here we show by using unbiased molecular dynamics simulations a protein structure-function mechanism for the spruce budworm Choristoneura fumiferana AFP, including stereo-specific binding and consequential melting and freezing inhibition.

Ion-to-Neutral Ratios and Thermal Proton Transfer in Matrix-Assisted Laser Desorption/Ionization.

The ion-to-neutral ratios of four commonly used solid matrices, α-cyano-4-hydroxycinnamic acid (CHCA), 2,5-dihydroxybenzoic acid (2,5-DHB), sinapinic acid (SA), and ferulic acid (FA) in matrix-assisted laser desorption/ionization (MALDI) at 355 nm are reported. Ions are measured using a time-of-flight mass spectrometer combined with a time-sliced ion imaging detector. Neutrals are measured using a rotatable quadrupole mass spectrometer.

Order and correlation contributions to the entropy of hydrophobic solvation.

The entropy of hydrophobic solvation has been explained as the result of ordered solvation structures, of hydrogen bonds, of the small size of the water molecule, of dispersion forces, and of solvent density fluctuations. We report a new approach to the calculation of the entropy of hydrophobic solvation, along with tests of and comparisons to several other methods. The methods are assessed in the light of the available thermodynamic and spectroscopic information on the effects of temperature on hydrophobic solvation.

A fast deposition-crystallization procedure for highly efficient lead iodide perovskite thin-film solar cells.

Thin-film photovoltaics based on alkylammonium lead iodide perovskite light absorbers have recently emerged as a promising low-cost solar energy harvesting technology. To date, the perovskite layer in these efficient solar cells has generally been fabricated by either vapor deposition or a two-step sequential deposition process. We report that flat, uniform thin films of this material can be deposited by a one-step, solvent-induced, fast crystallization method involving spin-coating of a DMF solution of CH3NH3PbI3 followed immediately by exposure to chlorobenzene to induce crystallization.

pH and the surface tension of water.

Despite the strong adsorption of hydroxide ions, the surface tension of water is almost independent of pH between pH 1 and 13 when the pH is adjusted by addition of HCl or NaOH. This is consistent with the Gibbs adsorption isotherm which measures the surface excess of all species in the double layer, if hydronium ions and hydroxide ions are adsorbed and sodium and chloride ions are not. The surface tension becomes pH dependent around pH 7 in millimolar NaCl or KCl solutions, for now sodium ions can replace hydronium ions as counterions to the adsorbed hydroxide ions.

Oil/Water interface charged by hydroxide ions and deprotonated fatty acids: a comment.

The effect of fatty acid impurities on the electrophoretic mobility of hexadecane in water emulsions is reinterpreted, occasioned by an error in the surface charge attributed to the fatty acids. The results are consistent with a surface charge contributed by both hydroxide ions and deprotonated fatty acids.

The structure of cardiac glycogen in healthy mice.

Transmission electron micrographs of glycogen extracted from healthy mouse hearts reveal aggregate structures around 133 nm in diameter. These structures are similar to, but on average somewhat smaller than, the α-particles of glycogen found in mammalian liver. Like the larger liver glycogens, these new particles in cardiac tissue appear to be aggregates of β-particles.

The surface relaxation of water.

We examine three possible explanations for the millisecond relaxation time of the dynamic surface tension of water: the diffusion of surfactant contaminants from the aqueous phase to the surface, the reorientation of surface water molecules' dipole moments, and the buildup of a charged surface layer of hydroxide ions. The relaxation time expected for hydroxide is by far the closest to the measured time. Our model for the surface layer agrees with static equilibrium experiments and, as we show here, predicts the relaxation time.

Molecular structural differences between type-2-diabetic and healthy glycogen.

Glycogen is a highly branched glucose polymer functioning as a glucose buffer in animals. Multiple-detector size exclusion chromatography and fluorophore-assisted carbohydrate electrophoresis were used to examine the structure of undegraded native liver glycogen (both whole and enzymatically debranched) as a function of molecular size, isolated from the livers of healthy and db/db mice (the latter a type 2 diabetic model). Both the fully branched and debranched levels of glycogen structure showed fundamental differences between glycogen from healthy and db/db mice.

Microenvironment-switchable singlet oxygen generation by axially-coordinated hydrophilic ruthenium phthalocyanine dendrimers.

A series of new metallodendrimers built around a ruthenium phthalocyanine core has been prepared. Employing a convergent synthetic strategy, pyridine-containing ligands were prepared and then assembled onto the ruthenium phthalocyanine through axial ligand coordination. The growing shell of oligoethylene glycol chains surrounding the lipophilic core allows solubilisation in water.

Ab Initio Study of Water Polarization in the Hydration Shell of Aqueous Hydroxide: Comparison between Polarizable and Nonpolarizable Water Models.

Ab initio simulations of aqueous hydroxide are performed to study the structure and polarization of water molecules in the first solvation shell. Polarization is found to depend on the configuration of the hydrogen-bond (HB) donors. In the most common case of four HB donors, the dipole moment of water molecules is much larger than those in the first shell of monovalent ions.

Hyperbranched alternating block copolymers using thiol-yne chemistry: materials with tuneable properties.

Alternating-block hyperbranched polymers were synthesized using the highly versatile thiol-yne reaction. Dimethyl acrylamide-styrene and tert-butyl acrylate-styrene polymers were prepared, with subsequent hydrolysis of the tert-butyl ester to acrylic acid. The dimethyl acrylamide-styrene hyperbranched polymers self-assembled into large aggregates, as did the acrylic acid-styrene system at low pH.

A divergent synthesis of modular dendrimers via sequential C-C bond fragmentation thio-Michael addition.

The C-C bond fragmentation of carbocycles has been developed as a new method for the divergent synthesis of dendrimers. The scope of this reaction was examined with the preparation of six first generation dendrimers from structurally diverse and readily available fragmentation precursors. By pairing the fragmentation with a thio-Michael reaction, the preparation of a [G4]-ene(24) dendrimer has been achieved.

Nature of alpha and beta particles in glycogen using molecular size distributions.

Glycogen is a randomly hyperbranched glucose polymer. Complex branched polymers have two structural levels: individual branches and the way these branches are linked. Liver glycogen has a third level: supramolecular clusters of beta particles which form larger clusters of alpha particles.

Hyperbranched polymers by thiol-yne chemistry: from small molecules to functional polymers.

A new synthesis of hyperbranched polymers is outlined. This paper presents the synthesis of hyperbranched polymers by the recently highlighted thiol-yne reaction. In the thiol-yne reaction, a catalytic amount of photoinitiator and UV radiation are used to add two thiols across one alkyne bond at room temperature.

An explanation for the charge on water's surface.

Measurements with different techniques point to a strong affinity of hydroxide ions for interfaces between water and hydrophobes, but some spectroscopic experiments do not detect excess hydroxide at the interface, while others do. Hydroxide ions are unusual in that they reduce the relative permittivity of an electrolyte solution more than other monovalent, monatomic ions. This implies that they suppress the collective dipole-moment fluctuations of nearby waters.

Comparative structural analyses of purified glycogen particles from rat liver, human skeletal muscle and commercial preparations.

Glycogen is a cellular energy store that is crucial for whole body energy metabolism, metabolic regulation and exercise performance. To understand glycogen structure we have purified glycogen particles from rat liver and human skeletal muscle tissues and compared their biophysical properties with those found in commercial glycogen preparations. Ultrastructural analysis of commercial liver glycogens fails to reveal the classical alpha-rosette structure but small irregularly shaped particles.

Extracting physically useful information from multiple-detection size-separation data for starch.

A method for interpreting multiple-detection size separation data of complex branched homopolymers [Konkolewicz, D.; Gilbert, R. G.

Obtaining kinetic information from the chain-length distribution of polymers produced by RAFT.

We describe a simple model for the kinetics and chain-length distribution of polymers made by living radical techniques. Living radical methods give good control over the molecular weight of a linear polymer by capping the growing end and forming a dormant chain. The polymer is predominantly capped, and occasionally decaps to form a radical that propagates for a short period before recapping.