Anti-diabetic Properties of Calcium Channel Blockers: Inhibition Effects on Aldose Reductase Enzyme Activity

Applied Biochemistry and Biotechnology - Aldose reductase (AR) belongs to NADPH-dependent oxidoreductases and converts glucose to sorbitol in the polyol pathway. AR inhibition is essential to...     

A photoprogrammable electronic nose with switchable selectivity for VOCs using MOF films

Advanced analytical applications require smart materials and sensor systems that are able to adapt or be configured to specific tasks. Based on reversible photochemistry in nanoporous materials, we present a sensor array with a selectivity that is reversibly controlled by light irradiation. The active material of the sensor array, or electronic nose (e-nose), is based on metal–organic frameworks (MOFs) with photoresponsive fluorinated azobenzene groups that can be optically switched between their trans and cis state. By irradiation with light of different wavelengths, the trans–cis ratio can be modulated. Here we use four trans–cis values as defined states and employ a four-channel quartz-crystal microbalance for gravimetrically monitoring the molecular uptake by the MOF films. We apply the photoprogrammable e-nose to the sensing of different volatile organic compounds (VOCs) and analyze the sensor array data with simple machine-learning algorithms. When the sensor array is in a state with all sensors either in the same trans- or cis-rich state, cross-sensitivity between the analytes occurs and the classification accuracy is not ideal. Remarkably, the VOC molecules between which the sensor array shows cross-sensitivity vary by switching the entire sensor array from trans to cis. By selectively programming the e-nose with light of different colors, each sensor exhibits a different isomer ratio and thus a different VOC affinity, based on the polarity difference between the trans- and cis-azobenzenes. In such photoprogrammed state, the cross-sensitivity is reduced and the selectivity is enhanced, so that the e-nose can perfectly identify the tested VOCs. This work demonstrates for the first time the potential of photoswitchable and thus optically configurable materials as active sensing material in an e-nose for intelligent molecular sensing. The concept is not limited to QCM-based azobenzene-MOF sensors and can also be applied to diverse sensing materials and photoswitches.

A sensor array with four identical photoresponsive azobenzene-containing metal–organic framework films is selectively irradiated. By photoprogamming the array, the sensor selectivity is switched and optimized.     

Stabilization of horseradish peroxidase by covalent conjugation with dextran aldehyde against temperature and pH changes

Stabilization of Horseradish Peroxidase (HRP; EC 1.11.1.7) against temperature and pH via the formation of the conjugates obtained by multipoint covalent bonding of dextran aldehyde (DA) to the enzyme were studied. Hence, three different molar weighted dextrans (17.5 kD, 75 kD, 188 kD) were covalently bonded to purified enzyme with different molar ratios (n_HRP/n_DA 20/1, 10/1, 1/1, 1/5, 1/10, 1/15, 1/20). The thermal stabilities of the obtained conjugates were evaluated with the activities determined at different temperatures (25, 30, 35, 40, 50, 60, 70, 80°C) applying 60 minutes incubation time. Conjugates formed were characterized by gel-permeation chromatography (GPC) and fluorescence techniques. The conjugate synthesized using dextran 75 kDa with n_HRP/n_DA 1/10 molar ratio showed better thermal stability than other conjugates and purified enzyme at pH 7. This conjugate also has wider activity pH range than purified enzyme. In addition, mentioned conjugate at pH 7 had very long storage lifetime compared to purified enzyme at +4°C and room temperature; which is considered a favorable feature for usage in practice.      

Structural changes in Poly(lactic acid)–zeolite nanocomposites exposed to 60Co gamma rays

Poly(lactic acid) (PLA) nanocomposites containing 3%, 5% and 7% zeolite used in the present research study were prepared by solution casting. The PLA nanocomposites were structurally characterized by Scanning Electron Microscopy and Fourier-transform infrared spectroscopy. The effects of the gamma radiation at the absorbed doses of 10, 15 and 20?kGy on the structures and thermal properties of the nanocomposites were investigated in a tetrahydrofuran solvent. Thermodecomposition tests and analyses were carried within 30–500°C range at the rate of 10°C?min^?1 by thermogravimetric analysis (TG). The activation energies for thermal degradation of the nanocomposites were calculated from their TG data by Flynn–Wall–Ozawa method. The G values of the nanocomposites were calculated based on molecular weights which were measured by means of gel permeation chromatography before and after the gamma irradiation. The E_a and molecular weight results showed that addition of zeolite to the PLA affected the radiation resistance of the polymer.     

Cytotoxic effect,enzyme inhibition,and in silico studies of some novel N-substituted sulfonyl amides incorporating 1,3,4-oxadiazol structural motif

Molecular Diversity - The acetylcholinesterase and carbonic anhydrase inhibitors (AChEIs and hCAIs) remain key therapeutic agents for many bioactivities such as anti-Alzheimer and antiobesity...     

Inflation and inflation uncertainty: A dynamic framework

This paper aims to investigate the direct relationship between inflation and inflation uncertainty by employing a dynamic method for the monthly country–region–place United States data for the time period 1976–2007. While the bulk of previous studies has employed GARCH models in investigating the link between inflation and inflation uncertainty, in this study Stochastic Volatility in Mean models are used to capture the shocks to inflation uncertainty within a dynamic framework. These models allow researchers to assess the dynamic effects of innovations in inflation as well as inflation volatility on inflation and inflation volatility over time, by incorporating the unobserved volatility as an explanatory variable in the mean (inflation) equation. Empirical findings suggest that innovations in inflation volatility increases inflation. This evidence is robust across various definitions of inflation and different sub-periods.     

Comparative combustion study of some polymers with oil shale

In this study, the combustion kinetics of G?ynük oil shale, polyethylene, polyethylene glycol (PEG), polymethyl methacrylate (PMMA), polyvinyl chloride, and polymer?Coil shale blends were investigated by thermogravimetric analysis. Experiments were conducted at non-isothermal conditions with a heating rate of 5?K?min^?1 in the 298?C1173?K temperature interval under air atmosphere. An increase in the total conversion values with increasing mass percentage of polymers of the blends was observed. Differential thermogravimetric data were analyzed by an Arrhenius model. Effects of blending ratio of oil shale and polymer on the combustion kinetics were investigated. Kinetic parameters were determined and the results were discussed. An increase was observed in the frequency factor and activation energy values as the weight percentage of polymer in blends were increased. The minimum activation energy, 16.1?kJ?mol^?1, was calculated for PEG/oil shale with 2/3 blending ratio.     

Selective and periodic inventory routing problem for waste vegetable oil collection

We consider a biodiesel production company that collects waste vegetable oil from source points that generate waste in large amounts. The company uses the collected waste as raw material for biodiesel production. The manager of this company needs to decide which of the present source points to include in the collection program, which of them to visit on each day, which periodic routing schedule to repeat over an infinite horizon and how many vehicles to operate such that the total collection, inventory and purchasing costs are minimized while the production requirements and operational constraints are met. For this selective and periodic inventory routing problem, we propose two different formulations, compare them and apply the better performing one on a real-world problem with 36 scenarios. We generate lower bounds using a partial linear relaxation model, and observe that the solutions obtained through our model are within 3.28% of optimality on the average. Several insights regarding the customer selection, routing and purchasing decisions are acquired with sensitivity analysis.     

The determination of β-agonist residues in bovine tissues using liquid chromatography–tandem mass spectrometry

We aimed to develop a rapid, simple and reproducible method based on LC–tandem mass spectrometry (LC–MS/MS) to analyze β-agonist residues (clenbuterol, zilpaterol, ractopamine and isoxsuprine) in bovine tissues. The method was validated in accordance with the European Council Decision 2002/657/EC. The samples were homogenized, and then 10 mL of an acetate buffer was added to a 5-g sample. The sample was then centrifuged at 12,000 rpm and filtered. Sodium hydroxide (2 m ) was added to adjust pH of the sample that was centrifuged again. The extract was filtered through a solid-phase extraction column. The residue was re-dissolved in 250 μL acetonitrile and then subjected to LC–MS/MS. The separation was done on a C₁₈ column. The mobile phase consisted of 0.1% formic acid in deionized water and 0.1% formic acid in methanol. The mean recoveries of β-agonists were in the range of 84.3%–119.1% with relative standard deviations (%RSDs) of 0.683%–4.05%. Decision limits and detection capabilities of the analytes ranged from 0.0960 to 4.9349 μg/kg and from 0.0983 to 5.0715, respectively. This method was used to detect four β-agonists in 100 bovine muscle, 100 liver and 100 kidney tissues from a slaughterhouse. No residue was found above the maximum residue limit level.     

When some complement of a z-closed submodule is a summand

In this article we study modules with the condition that every z-closed submodule has a complement which is a direct summand. This new class of modules properly contains the class of extending modules. It is well known that the class of extending modules is closed under direct summands, but not under direct sums. In contrast to extending (or CS) modules, it is shown that the class of modules with former property is closed under direct sums. However we provide number of algebraic topological examples which show that this new class of modules is not closed under direct summands. To this end we obtain several results on the inheritance of the latter closure property.