Strong Hydrophobic Interaction of High Molecular Weight Chitosan in Aqueous Solution.

Chitosan is a versatile bioactive polysaccharide in various industries, such as pharmaceuticals and environmental applications, owing to its abundance, biodegradability, biocompatibility, and antibacterial properties. To effectively harness its potential for various purposes, it is crucial to understand the mechanisms of its interaction in water. This study investigates the interactions between high molecular weight (HMW, >150 kDa) chitosan and four different functionalized self-assembled monolayers (SAMs) at three different pHs (3.

Influence of the backbone chemistry and ionic functional groups of five pairs of oppositely charged polyelectrolytes on complex coacervation.

Complex coacervation plays an important role in various fields. Here, the influences of the backbone chemistry and ionic functional groups of five pairs of oppositely charged polyelectrolytes on complex coacervation were investigated. These pairs include synthetic polymers with aliphatic hydrocarbon backbones, peptides with amide bonds, and carbohydrates with glycosidic linkages.

Anomalous diffusion of lithium-anion clusters in ionic liquids.

Lithium-ion transport is significantly retarded in ionic liquids (ILs). In this work, we performed extensive molecular dynamics simulations to mimic the kinetics of lithium ions in ILs using [N-methyl-N-propylpyrrolidium (pyr[Formula: see text])][bis(trifluoromethanesulfonyl)imide (Ntf[Formula: see text])] with added LiNtf[Formula: see text] salt. And we analyzed their transport, developing a two-state model and comparing it to the machine learning-identified states.

Cation-π Interactions Contribute to Hydrophobic Humic Acid Removal for the Control of Hydraulically Irreversible Membrane Fouling.

Hydraulically irreversible membrane fouling is a major problem encountered during membrane-based water purification. Membrane foulants present large hydrophobic fractions, with humic acid (HA) being a prevalent example of hydrophobic natural organic matter. Furthermore, HA contains numerous aromatic rings (π electrons), and its hydrophobic interactions are a major cause of irreversible membrane fouling.

Terahertz radiation from propagating acoustic phonons based on deformation potential coupling.

We report on new THz electromagnetic emission mechanism from deformational coupling of acoustic (AC) phonons with electrons in the propagation medium of non-polar Si. The epicenters of the AC phonon pulses are the surface and interface of a GaP transducer layer whose thickness (d) is varied in nanoscale from 16 to 45 nm. The propagating AC pulses locally modulate the bandgap, which in turn generates a train of electric field pulses, inducing an abrupt drift motion at the depletion edge of Si.

Nanoscale mapping of surface strain in tapered nanorods using confocal photoluminescence spectroscopy.

The strain occurs spontaneously at the heterogeneous interfaces of virtually all crystalline materials. Consequently, the analysis across multiple interfaces requires a complementary characterization scheme with a resolution that fits the deformation scale. By implementing two-photon confocal laser scanning nanoscopy with an axial resolution of 10 nm, we extract the surface strain from the photoluminescence (PL) spectra, epitomized by a 2-fold enhancement at the tapered tips in comparison to the substrate of ZnO nanorods.

The Role of the Graphene Oxide (GO) and Reduced Graphene Oxide (RGO) Intermediate Layer in CZTSSe Thin-Film Solar Cells.

CuZnSn(S,Se) (CZTSSe) solar cells with low cost and eco-friendly characteristics are attractive as future sources of electricity generation, but low conversion efficiency remains an issue. To improve conversion efficiency, a method of inserting intermediate layers between the CZTSSe absorber film and the Mo back contact is used to suppress the formation of MoSe and decomposition of CZTSSe. Among the candidates for the intermediate layer, graphene oxide (GO) and reduced GO have excellent properties, including high-charge mobility and low processing cost.

High frequency atomic tunneling yields ultralow and glass-like thermal conductivity in chalcogenide single crystals.

Crystalline solids exhibiting glass-like thermal conductivity have attracted substantial attention both for fundamental interest and applications such as thermoelectrics. In most crystals, the competition of phonon scattering by anharmonic interactions and crystalline imperfections leads to a non-monotonic trend of thermal conductivity with temperature. Defect-free crystals that exhibit the glassy trend of low thermal conductivity with a monotonic increase with temperature are desirable because they are intrinsically thermally insulating while retaining useful properties of perfect crystals.

Martini Coarse-Grained Model of Hyaluronic Acid for the Structural Change of Its Gel in the Presence of Monovalent and Divalent Salts.

Hyaluronic acid (HA) has a wide range of biomedical applications including the formation of hydrogels, microspheres, sponges, and films. The modeling of HA to understand its behavior and interaction with other biomolecules at the atomic level is of considerable interest. The atomistic representation of long HA polymers for the study of the macroscopic structural formation and its interactions with other polyelectrolytes is computationally demanding.

Universality, Scaling, and Collapse in Supercritical Fluids.

Supercritical fluid (SCF) is known to exhibit salient dynamic and thermodynamic crossovers and an inhomogeneous molecular distribution. However, the question as to what basic physics underlies these microscopic and macroscopic anomalies remains open. Here, using an order parameter extracted by machine learning, the fraction of gas-like (or liquid-like) molecules, we find simplicity and universality in SCF: First, all isotherms of a given fluid collapse onto a single master curve described by a scaling relation.

Cation-π Interactions and Their Contribution to Mussel Underwater Adhesion Studied Using a Surface Forces Apparatus: A Mini-Review.

Mussel underwater adhesion is a model phenomenon important for the understanding of broader biological adhesion and the development of biomimetic wet adhesives. The catechol moiety of 3,4-dihydroxyphenyl-l-alanine (DOPA) is known to be actively involved in the mechanism of mussel underwater adhesion; however, other underwater adhesion mechanisms are also crucial. The surface forces apparatus (SFA) has often been used to explore the contributions of other mechanisms to mussel underwater adhesion; e.

Two-Step Energy Transfer Dynamics in Conjugated Polymer and Dye-Labeled Aptamer-Based Potassium Ion Detection Assay.

We recently implemented highly sensitive detection systems for photo-sensitizing potassium ions (K) based on two-step Förster resonance energy transfer (FRET). As a successive study for quantitative understanding of energy transfer processes in terms of the exciton population, we investigated the fluorescence decay dynamics in conjugated polymers and an aptamer-based 6-carboxyfluorescein (6-FAM)/6-carboxytetramethylrhodamine (TAMRA) complex. In the presence of K ions, the Guanine-rich aptamer enabled efficient two-step resonance energy transfer from conjugated polymers to dyed pairs of 6-FAM and TAMRA through the G-quadruplex phase.

Broadband tuning of ring-type cavity-dumped femtosecond optical parametric oscillator in the near-infrared.

We report a cavity-dumped optical parametric oscillator (OPO) with a ring-type cavity configuration, which is based on periodically poled lithium niobate gain synchronously pumped by a mode-locked Ti:sapphire laser. Because of reduced cavity loss and group velocity dispersion inherent to ring-cavity employment, a wide wavelength tuning capability from 1.02 to 1.

Upper Critical Solution Temperature (UCST) Behavior of Coacervate of Cationic Protamine and Multivalent Anions.

Complex coacervation is an emerging liquid/liquid phase separation (LLPS) phenomenon that behaves as a membrane-less organelle in living cells. Yet while one of the critical factors for complex coacervation is temperature, little analysis and research has been devoted to the temperature effect on complex coacervation. Here, we performed a complex coacervation of cationic protamine and multivalent anions (citrate and tripolyphosphate (TPP)).

Coherent control of thermal phonon transport in van der Waals superlattices.

van der Waals (vdW) heterostructures are a central focus of materials science and condensed matter physics due to the novel physical phenomena and properties obtained by precisely stacking heterogeneous atomically thin layers. vdW heterostructures are expected to allow for the coherent manipulation of THz lattice vibrations and hence heat conduction due to the ability to precisely control chemical composition at the atomic scale, but little work has focused on thermal transport in these materials. Here, we report an ab initio study of thermal transport in vdW superlattices consisting of alternating transition metal dichalcogenide atomic layers.

Widom Delta of Supercritical Gas-Liquid Coexistence.

Density fluctuations and the Widom line are of great importance in understanding the critical phenomena and the behaviors of supercritical fluids (SCFs). We report on the direct classification of liquid-like and gas-like molecules coexisting in the SCF, identified by machine learning analysis on simulation data. The deltoid coexistence region encloses the Widom line and may therefore be termed the Widom delta.

Detection and phylogenetic analysis of a new adenoviral polymerase gene in reptiles in Korea.

Over a period of 7 years (2004-2011), samples from 34 diseased reptiles provided by local governments, zoos, and pet shops were tested for viral infection. Animals were diagnosed based on clinical signs, including loss of appetite, diarrhea, rhinorrhea, and unexpected sudden death. Most of the exotic animals had gastrointestinal problems, such as mucosal redness and ulcers, while the native animals had no clinical symptoms.

Emission analysis of Tb -and Sm -ion-doped (Li O/Na O/K O) and (Li O + Na O/Li O + K O/K O + Na O)-modified borosilicate glasses.

Four series of borosilicate glasses modified by alkali oxides and doped with Tb and Sm ions were prepared using the conventional melt quenching technique, with the chemical composition 74.5B O + 10SiO + 5MgO + R + 0.5(Tb O /Sm O ) [where R = 10(Li O /Na O/K O) for series A and C, and R = 5(Li O + Na O/Li O + K O/K O + Na O) for series B and D].

Salt Triggers the Simple Coacervation of an Underwater Adhesive When Cations Meet Aromatic π Electrons in Seawater.

Adhesive systems in many marine organisms are postulated to form complex coacervates (liquid-liquid phase separation) through a process involving oppositely charged polyelectrolytes. Despite this ubiquitous speculation, most well-characterized mussel adhesive proteins are cationic and polyphenolic, and the pursuit of the negatively charged proteins required for bulk complex coacervation formation internally remains elusive. In this study, we provide a clue for unraveling this paradox by showing the bulky fluid/fluid separation of a single cationic recombinant mussel foot protein, rmfp-1, with no additional anionic proteins or artificial molecules, that is triggered by a strong cation-π interaction in natural seawater conditions.

III-nitride core-shell nanorod array on quartz substrates.

We report the fabrication of near-vertically elongated GaN nanorods on quartz substrates. To control the preferred orientation and length of individual GaN nanorods, we combined molecular beam epitaxy (MBE) with pulsed-mode metal-organic chemical vapor deposition (MOCVD). The MBE-grown buffer layer was composed of GaN nanograins exhibiting an ordered surface and preferred orientation along the surface normal direction.

Molecular and structural basis of low interfacial energy of complex coacervates in water.

Complex coacervate refers to a phase-separated fluid, typically of two oppositely charged polyelectrolytes in solution, representing a complex fluid system that has been shown to be of essential interest to biological systems, as well as for soft materials processing owing to the expectation of superior underwater coating or adhesion properties. The significance and interest in complex coacervate fluids critically rely on its low interfacial tension with respect to water that, in turn, facilitates the wetting of macromolecular or material surfaces under aqueous conditions, provided there is attractive interaction between the polyelectrolyte constituents and the surface. However, the molecular and structural bases of these properties remain unclear.

Inositol pyrophosphates inhibit synaptotagmin-dependent exocytosis.

Inositol pyrophosphates such as 5-diphosphoinositol pentakisphosphate (5-IP7) are highly energetic inositol metabolites containing phosphoanhydride bonds. Although inositol pyrophosphates are known to regulate various biological events, including growth, survival, and metabolism, the molecular sites of 5-IP7 action in vesicle trafficking have remained largely elusive. We report here that elevated 5-IP7 levels, caused by overexpression of inositol hexakisphosphate (IP6) kinase 1 (IP6K1), suppressed depolarization-induced neurotransmitter release from PC12 cells.

Bicontinuous Fluid Structure with Low Cohesive Energy: Molecular Basis for Exceptionally Low Interfacial Tension of Complex Coacervate Fluids.

An exceptionally low interfacial tension of a dense fluid of concentrated polyelectrolyte complexes, phase-separated from a biphasic fluid known as complex coacervates, represents a unique and highly sought-after materials property that inspires novel applications from superior coating to wet adhesion. Despite extensive studies and broad interest, the molecular and structural bases for the unique properties of complex coacervates are unclear. Here, a microphase-separated complex coacervate fluid generated by mixing a recombinant mussel foot protein-1 (mfp-1) as the polycation and hyaluronic acid (HA) as the polyanion at stoichiometric ratios was macroscopically phase-separated into a dense complex coacervate and a dilute supernatant phase to enable separate characterization of the two fluid phases.

Chiral nematic self-assembly of minimally surface damaged chitin nanofibrils and its load bearing functions.

Chitin is one of the most abundant biomaterials in nature, with 10(10) tons produced annually as hierarchically organized nanofibril fillers to reinforce the exoskeletons of arthropods. This green and cheap biomaterial has attracted great attention due to its potential application to reinforce biomedical materials. Despite that, its practical use is limited since the extraction of chitin nanofibrils requires surface modification involving harsh chemical treatments, leading to difficulties in reproducing their natural prototypal hierarchical structure, i.

Adsorption of highly charged Gaussian polyelectrolytes onto oppositely charged surfaces.

In many biological processes highly charged biopolymers are adsorbed onto oppositely charged surfaces of macroions and membranes. They form strongly correlated structures close to the surface which cannot be explained by the conventional Poisson-Boltzmann theory. In this work strong coupling theory is used to study the adsorption of highly charged Gaussian polyelectrolytes.