Graphene Quantum Dots Incorporated into β-cyclodextrin: a Novel Polymeric Nanocomposite for Non-Enzymatic Sensing of L-Tyrosine at Physiological pH

Graphene quantum dot-β-cyclodextrin modified glassy carbon electrode was used as a new nanosensor for determination of L-tyrosine (L-Tyr). It was found that graphene quantum dot-β-cyclodextrin has been stably electrodeposited on glassy carbon electrode modified by simple technique. The cyclic voltammograms of the modified electrode in an aqueous solution displayed a pair of well-defined, stable and irreversible reductive/oxidation redox systems. The apparent electron transfer rate constant (k_s) and transfer coefficient (α) determined by cyclic voltammetry were approximately equal to 8.0 s^–1 and 0.7, respectively. The modified electrode showed excellent catalytic activity towards the oxidation of L-Tyr at positive potential in buffer solution. The nanosensor also displayed fast response time, high sensitivity, low detection limit and a remarkably positive potential oxidation of L-Tyr that decreased the effect of interferences in analysis.     

4-(4′-Diamino-di-phenyl)-sulfone supported on hollow magnetic mesoporous Fe3O4@SiO2 NPs: As a reusable and efficient catalyst for the synthesis of ethyl 2-amino-5,10-dihydro-5,10-dioxo-4-phenyl-4H benzo[g]chromene-3-carboxylates

4-(4′-diamino-di-phenyl)-sulfone supported on hollow magnetic mesoporous (HMMS) Fe₃O₄@SiO₂ NPs has been used as a novel and efficient catalyst in the preparation of ethyl 2-amino-5,10-dihydro-5,10-dioxo-4-phenyl-4H benzo[g]chromene-3-carboxylates by a simple one-pot three-component reaction of aldehydes, ethyl cyanoacetate and 2-hydroxynaphthalene-1,4-dione under reflux conditions in ethanol. Wide range of products, excellent yields in short times, reusability of the catalyst, low catalyst loading and environmental benignity are some of the important features of this protocol.     

Simultaneous voltammetric sensing of acetaminophen,epinephrine and melatonin using a carbon paste electrode modified with zinc ferrite nanoparticles

A highly selective electrochemical sensor was fabricated based on a modified carbon paste electrode with zinc ferrite nanoparticles (ZnFe₂O₄ NPs). The nanocomposite has attractive properties such as high surface-to-volume ratio and good electrocatalytic activity towards the drugs acetaminophen (AC), epinephrine (EP), and melatonin (MT), best at working voltages of 0.35, 0.09 and 0.55 V (vs. Ag/AgCl), respectively. The linear ranges (and detection limits) are 6.5–135 (0.4) μmol L^?1 for AC, 5–100 (0.7) μmol L^?1 for EP, and 6.5–145 (3) μmol L^?1 for MT.

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Graphical abstract A novel electrochemical sensor based on a modified carbon paste electrode with zinc ferrite nanoparticles (ZnFe₂O₄) for the simultaneous detection of the acetaminophen, epinephrine and melatonin was fabricated

     

Electrochemical determination of naproxen in the presence of acetaminophen using a carbon paste electrode modified with activated carbon nanoparticles

In this study, cyclic voltammetry and differential pulse voltammetry were used to determine the electrochemical properties and concentration of naproxen in pharmaceutical formulation and human serum samples by using a carbon paste electrode modified with activated carbon nanoparticles. Optimum conditions were obtained at an electrode with 0.005 g activated carbon nanoparticles in a phosphate buffer solution of pH 6 as a supporting electrolyte. Linear calibration curves were obtained in the range of 0.1–120 μM, and the detection limit of naproxen determined was 0.0234 μM. The modified electrode shows good selectivity for naproxen in the presence of some organic and inorganic interferences and very good precision in real samples. Finally, naproxen was measured in the presence of acetaminophen.     

Sintokamides A to E, chlorinated peptides from the sponge Dysidea sp. that inhibit transactivation of the N-terminus of the androgen receptor in prostate cancer cells

The new chlorinated peptides sintokamides A to E (1-5) have been isolated from specimens of the marine sponge Dysidea sp. collected in Indonesia. Their structures were elucidated by a combination of spectroscopic and single-crystal X-ray diffraction analyses. Sintokamide A (1) is an inhibitor of N-terminus transactivation of the androgen receptor in prostate cancer cells.     

A New Approach for Titration Calorimetric Data Analysis on the Binding of Magnesium Ion with Myelin Basic Protein

The interaction of the myelin basic protein (MBP) from the bovine central nervous system with divalent magnesium ion was studied by isothermal titration calorimetry at 27 °C in aqueous solution. A simple rapid method for determination of the dissociation binding constants for Mg²⁺-MBP interaction was introduced using the isothermal titration calometric data. The binding isotherm for Mg²⁺-MBP interaction is easily obtained by carrying out a titration calorimetric experiment using only one set of concentrations of MBP. There are two identical independent intrinsic association constants equal to 0.021 μmol⋅L⁻¹ in the first- and second-binding sites, respectively.     

On the Stability of a k-Cubic Functional Equation in Intuitionistic Fuzzy n-Normed Spaces

In this paper, we investigate some stability results concerning the k-cubic functional equation f(kx + y) + f(kx?y) = kf(x + y) + kf(x?y) + 2k(k²?1)f(x) in the intuitionistic fuzzy n-normed spaces.     

Guanidine Hydrochloride: A Highly Efficient Organocatalyst for the Synthesis of 12‐Aryl‐8,9,10,12‐tetrahydrobenzo[a]xanthene‐11‐ones Under Solvent‐Free Conditions

A new green protocol has been developed for the synthesis of 12‐aryl‐8,9,10,12‐tetrahydrobenzo[a]xanthen‐11‐ones using guanidine hydrochloride as an organocatalyst under solvent‐free conditions. Operational simplicity, mild reaction conditions, enhanced rates, high isolated yields of the pure products, and purification of products by nonchromatographic methods are significant advantages of the protocol presented here.