Reduction In Viscosity Of Solutions Research Articles

O-glycans Expand Lubricin and Attenuate Its Viscosity and Shear Thinning.

Lubricin, an intrinsically disordered glycoprotein, plays a pivotal role in facilitating smooth movement and ensuring the enduring functionality of synovial joints. The central domain of this protein serves as a source of this excellent lubrication and is characterized by its highly glycosylated, negatively charged, and disordered structure. However, the influence of O-glycans on the viscosity of lubricin remains unclear. In this study, we employ molecular dynamics simulations in the absence and presence of shear, along with continuum simulations, to elucidate the intricate interplay between O-glycans and lubricin and the impact of O-glycans on lubricin's conformational properties and viscosity. We found the presence of O-glycans to induce a more extended conformation in fragments of the disordered region of lubricin. These O-glycans contribute to a reduction in solution viscosity but at the same time weaken shear thinning at high shear rates, compared to nonglycosylated systems with the same density. This effect is attributed to the steric and electrostatic repulsion between the fragments, which prevents their conglomeration and structuring. Our computational study yields a mechanistic mechanism underlying previous experimental observations of lubricin and paves the way to a more rational understanding of its function in the synovial fluid.

Activation functions of photodegraded carboxymethyl cellulose in solution: Viscosity measurements

Carboxymethyl cellulose (CMC) is used in several applications exposed to light and radiation, such as food and medical products. The exposure to photons could affect the CMC properties and behaviour therefore the products. Our main objective is to investigate the relative viscosity/temperature relationships of CMC fragments in a NaCl solution. The method of photodegradation technology has been used, and the data were attained viscometrically. The decrease in macromolecular mass and concentration brought down the reduction in solution viscosity, while the temperature had the opposite effect. Eyring's parameters as functions of concentration and molar mass were then illustrated. The enthalpy and Arrhenius factor have increased with increasing concentration and molar mass, while the entropy has decreased. The polyelectrolytic CMC fractions in salt solutions behaved like polymers in neutral solutions. The photodegraded solution of CMC had better solvation quality than the native one.

Impact assessment of the variables affecting the drug release and extraction of polyethylene oxide based tablets

The overall objective of this research is to investigate the impacts of the polymer's molecular weight and source on the abuse deterrent properties of the PEO-based promethazine hydrochloride (PMZ HCl) tablets. Formulations were manufactured by hot-melt extrusion and direct compression, followed by curing. Thermal and mechanical manipulation techniques were applied and compared to the intact tablets. The prime mechanism of the drug release was found to be represented by the diffusion-controlled mechanism and the first-order model for the direct compressed and the hot-melt extruded whole tablets, respectively. A robust Artificial Neural Network (ANN) model was built, and a significance testing analysis was performed to identify the criticality and the impact of the investigated variables on the % release of the active pharmaceutical ingredient (API). The results showed that the use of the polymer from different suppliers had the lowest impact on the % release per time point. Furthermore, we observed that the tablets produced by hot-melt extrusion had faster release rates than tablets produced by direct compression. Moreover, the extraction studies showed that the % API recovered from the hot-melt extruded tablets was significantly higher than the direct compressed tablets regardless of the polymer molecular weight. The findings were attributed to the polymer's thermal degradation during the hot-melt extrusion process, which caused a reduction in solution viscosity and crystallinity of the polymer. The syringeability studies showed that it was relatively harder to withdraw the solution from the DOW samples; however, the % recovered API was higher than samples containing the polymer from Sumitomo Seika.

Electrophoretic deposition of alginate coatings from different alcohol-water mixtures

ABSTRACT Alginate coatings were fabricated by electrophoretic deposition (EPD) using alcohol (methanol, ethanol and isopropanol)-water mixtures at different ratios. Water electrolysis and so current density increased with water content and EPD time leading to the more bubbles in coatings. EPD rate increased with water amount due to the increase in concentration of H+ and Alg− ions and reduction in solution viscosity. According to the results of kinetics, optical microscopy and corrosion analyses the coating deposited at 10 V for 1 min from the ethanolic solution with 60 vol.-% of water was selected as the optimum coating for in-vitro cell culture and antibacterial analyses. There was almost 30% rise in cell expansion for the sample with optimum coating after 7 days compared to the blank. Also, the coated sample showed antibacterial activity against Bacillus bacteria.

Effects of water and sodium dodecyl sulfate additives on Cr(III) ions electroreduction in a deep eutectic solvent

Kinetics of Cr(III) ions electroreduction in a deep eutectic solvent (ethaline) was studied by using electrochemical impedance spectroscopy. The influence of water and sodium dodecyl sulfate on the kinetic parameters was established. The developed equivalent circuit included polarization resistance of the electrochemical reaction, constant phase element and finite Warburg impedance. The respective parameters of the accepted equivalent circuit were calculated and discussed. The obtained results indicated that the charge transfer is a rate-determining step of an electrochemical reaction occurring on a heterogeneous electrode surface. An increase in content of water in electrolytes resulted in an increase in polarization resistance, indicating the deceleration of Cr(III) ions electroreduction due to the changes in Cr(III) speciation. In addition, the introduction of extra water caused an increase in the value of a capacitive component of electrochemical impedance because of a rearrangement of the double electrical layer. The polarization resistance of Cr(III) ion discharge was increased in the presence of sodium dodecylsulfate in electrolyte due to adsorption of dodecylsulfate anion on the electrode surface. A Warburg impedance component disappeared in electrolytes containing relatively high water content, which was associated with corresponding reduction of solution viscosity and acceleration of diffusion mass transfer.

Extending protein functionality: Microfluidization of heat denatured whey protein fibrils

The functional attributes of globular proteins can be extended by controlling the nature of the aggregates they form. In this study, the effect of thermal treatment (85°C/20 min) and high pressure microfluidization (20,000 psi, 1 pass) on the physical properties of whey protein isolate solutions (5–9%; pH 2) was investigated. Heating solutions of native whey protein isolate (8 wt%) under these acidic conditions led to the formation of highly viscous solutions (η = 306 mPa s) with low turbidity (τ = 0.04 cm−1), which was attributed to the formation of protein fibrils (effective d = 310 nm). Microfluidization of these protein fibrils decreased their length (effective d = 97 nm) leading to a substantial reduction in solution viscosity (η = 3.8 mPa s), and a slight reduction in turbidity (τ < 0.03 cm−1). The impact of solution pH (2–7) on the appearance and rheology of native, heated, and heated-microfluidized whey protein isolate solutions was then examined. For all systems, highly turbid solutions (τ > 1 cm−1) were formed at pH values close to the isoelectric point of the whey proteins (pH 4.5) due to protein self-association caused by reduction of the electrostatic repulsion between the protein molecules. Highly viscous or gelled solutions were formed for the heated and heated-microfluidized proteins across a wide pH range, which was attributed to the presence of fibrils. The study showed that the functional attributes of whey proteins can be modulated by thermal and high-pressure homogenization treatment.

Solvation by aqueous solutions of imidazole-based ionic liquids: 2- A comparison between alkyl and alkoxy side-chains

Binary mixtures of ionic liquids (ILs) and molecular solvents are employed for practical reasons, e.g., reduction of solution viscosity and overcoming solubility/miscibility problems. We obtain information on solvation in these media from solvent properties, e.g., empirical polarity ET(probe) calculated from the spectra of solvatochromic probes. To evaluate the effect on solvation of the IL cation side-chain we studied the solvatochromic response of the polarity probe WB (2,6-dichloro-4-(2,4,6-triphenylpyridinium-1-yl)phenolate) dissolved in the following aqueous ILs: 1-R-3-methylimidazoliumAcO, where R = 1-heptyl, C7MeImAcO; and 3,6-dioxa-(1-heptyl), C5O2MeImAcO; AcO = acetate; in the temperature range 15–60 °C. The relative acidity of the imidazolium ring hydrogens bears on solvation. Consequently, we extended our study to aqueous solutions of 1-R′-1,2-dimethylimidazoliumAcO, R' = 1-butyl (C4Me2ImAcO) and methoxyethyl (C3OMe2ImAcO). Our results showed that the expected effect of the side-chain ether oxygen on ET(WB) is impaired by formation of intramolecular hydrogen bonding, e.g., with hydrogens of the imidazolium ring. We corroborated this conclusion by 1H NMR data, and theoretical calculations (molecular dynamics simulations; quantum chemistry calculations). Introducing second ether oxygen (C5O2MeImAcO) and replacing C2-H by C2-CH3 in the imidazolium ring (C3OMe2ImAcO) increased the difference in polarity between ILs with alkoxy and alkyl side-chains. For C7MeImAcO and C5O2MeImAcO the dependence of ET(WB) on the water mole fraction was treated according to a model that includes solvation by the complex solvent (IL⋅⋅⋅water); the latter is the most efficient solvent species present because it forms more hydrogen-bonds with the phenolate oxygen of WB.

Molecular Dynamics Simulation of DNA Capture and Transport in Heated Nanopores.

The integration of local heat sources with solid-state nanopores offers new means for controlling the transmembrane transport of charged biomacromolecules. In the case of electrophoretic transport of DNA, recent experimental studies revealed unexpected temperature dependences of the DNA capture rate, the DNA translocation velocity, and the ionic current blockades produced by the presence of DNA in the nanopore. Here, we report the results of all-atom molecular dynamics simulations that elucidated the effect of temperature on the key microscopic processes governing electric field-driven transport of DNA through nanopores. Mimicking the experimental setup, we simulated the capture and subsequent translocation of short DNA duplexes through a locally heated nanopore at several temperatures and electrolyte conditions. The temperature dependence of ion mobility at the DNA surface was found to cause the dependence of the relative conductance blockades on temperature. To the first order, the effective force on DNA in the nanopore was found to be independent of temperature, despite a considerable reduction of solution viscosity. The temperature dependence of the solution viscosity was found to make DNA translocations faster for a uniformly heated system but not in the case of local heating that does not affect viscosity of solution surrounding the untranslocated part of the molecule. Increasing solution temperature was also found to reduce the lifetime of bonds formed between cations and DNA. Using a flow suppression algorithm, we were able to separate the effects of electro-osmotic flow and direct ion binding, finding the reduced durations of DNA–ion bonds to increase, albeit weakly, the effective force experienced by DNA in an electric field. Unexpectedly, our simulations revealed a considerable temperature dependence of solvent velocity at the DNA surface—slip velocity, an effect that can alter hydrodynamic coupling between the motion of DNA and the surrounding fluid.

Manipulation of hydrophobic interactions in associative polymers using cyclodextrin and enzyme

We examine a new approach to reversibly modulate hydrophobic interactions in associative polymers using cyclodextrins (CD) and enzymes that cause scission of the α-1, 4 linkages in cyclodextrins. The associative polymers have a comb-like structure with pendant hydrophobic groups randomly attached to the polymer backbone. The intermolecular interaction between hydrophobic groups forms a transient network resulting in thickening of solutions containing the polymer. The CDs, doughnut-shaped cyclic polysaccharides, encapsulate the hydrophobes within their hydrophobic cavity and eliminate hydrophobic interactions. This results in several orders of magnitude reduction in solution viscosity and other viscoelastic properties. Subsequent degradation of the CDs by enzymes restores the hydrophobic interactions and the original rheological properties. A rheokinetic model is developed to describe the kinetics of the enzymatic reactions. The model accounts for equilibrium between the CD bound to the hydrophobes and free CD in solution and assumes the enzyme hydrolyzes only the free CD in the solution, which causes the release of the bound CDs in order to maintain equilibrium. The reaction is assumed to follow Michaelis Menten kinetics and the kinetic parameters are determined by tracking the changes in the viscoelastic properties of the polymer solution during the enzymatic scission of CD. The effects of enzyme concentration, polymer concentration and temperature on the rate of recovery of the original rheological properties are experimentally determined, and used to validate the trends of the rheokinetic model.

Interfacial Slip Violations in Polymer Solutions: Role of Microscale Surface Roughness

Violations of the no-slip hydrodynamic boundary condition are investigated in polymer solutions using gap-dependent shear flow measurements between parallel plates. Solutions of high molar mass, 3.8 × 106 ≤ Mw ≤ 20.06 × 106, narrow molecular weight distribution polystyrene, PS, in diethyl phthalate, DEP (a good solvent of low volatility), are the main focus of the study. Violations of the no-slip condition in these systems are evident from an apparent reduction in solution viscosity as the plate separation is reduced. Viscosity measurements at multiple plate separations allow the slip velocity Vs and slip extrapolation length b to be quantified. This article reports b and Vs for polymer solutions over a wide range of shear stress and solution concentrations, 0.025 ≤ φ ≤ 0.079, that is, for polymer solutions spanning the range from marginally entangled to highly entangled liquids. For the most entangled solutions studied, extremely large extrapolation lengths, b > 200 μm, are observed. Extrapolation length...

Triggered enzymatic degradation of a water-soluble polymer solution using a novel inhibitor.

Controlled enzymatic degradation of solutions of guar galactomannan, a naturally occurring polysaccharide, offers a powerful tool to enhance its usage in a variety of applications. In this study, we use viscometry to investigate the use of tris(hydroxymethyl)aminomethane (Tris) as a reversible, pH-dependent inhibitor to control the degradation of guar galactomannan by Aspergillus niger beta-mannanase. Viscosity measurements of pH 9 guar solutions containing 25 mM Tris show no reduction in the viscosity when treated with beta-mannanase. In contrast, samples containing no Tris show significant reduction in viscosity within an hour. Samples maintained at a pH of 9 in the presence of Tris for several hours show no change in viscosity; however, reduction of the pH of the sample to 4 initiates enzymatic degradation of the guar solution resulting in a rapid reduction in solution viscosity. This reversible, pH-dependent inhibition is possibly a result of the protonation state of Tris as well as key amino acids in the active site.

Isolation and characterization of two endo-β-glucanases from solid-state cultures of the aerobic fungus Penicillium capsulatum

Two endo-β-glucanases from solid-state cultures of Penicillium capsulatum, have been purified to apparent homogeneity as judged by electrophoresis and isoelectric focusing. Each enzyme is a single subunit glycoprotein, containing 55–60 moles of carbohydrate per mole of glycoprotein. Enzyme A has an M r value of 38 kDa and a pI of 4.12, while form B has an M r of 36 kDa and a pI of 3.92. Both enzymes are similar with respect to pH and temperature optima (pH 5 and 65°C, respectively) and under these conditions have half-lives of 3.5 h. They are also similar with respect to substrate specificity and kinetic parameters. Comparison of the rates of reduction in viscosity of solutions of β-glucan with the rates of release of reducing equivalents therefrom showed each enzyme to be endoacting. This was confirmed by fractionation of the reaction products. On the basis of the above, each enzyme has been classified as an endo-β-1, 4-glucan 4 glucanohydrolase (EC 3.2.1.4).

Oxidation of cell wall polysaccharides by hydrogen peroxide: A potential mechanism for cell wall breakdown in plants

Incubation of cellulose, sodium carboxylcellulose, pectin, polygalacturonic acid, xylan and arabinogalactan with hydrogen peroxide (0.1-10 mM) resulted in rapid breakdown of the polysaccharides when measured by a reduction of solution viscosity or an increase in reducing groups. When the reaction mixtures were precipitated with ethanol or fractionated on G-25-300 Sephadex, low molecular weight reducing groups increased with incubation time indicating that polymer cleavage was occurring and not simply polymer modification. Oxidation was most rapid at pH 6.5 or 7.5, although secondary optima between pH 3.5 and 5.5 were also observed, depending on the polysaccharide. Purified cell walls isolated from various organs of tomato, cucumber and soybean were similarly degraded and the ethanol-soluble reaction products were partially characterized. The data support the hypothesis that hydrogen peroxide generated by peroxidase from NADH may play a role during cell wall breakdown in plants.

Structural changes in the molecular coils of polyisoprene in solution in the presence of iodine

In an earlier investigation it was shown that the action of iodine on polyisoprene (PI) in solution leads to a marked reduction in solution viscosity as a result of processes of cyclization and degradation [1]. In the present investigation our aim was to investigate structural changes in the macromolecular coils of PI in solution due to the action of iodine in the dark and in daylight.