An assay for the enzyme N-acetyl-beta-D-glucosaminidase (NAGase) based on electrochemical detection using screen-printed carbon electrodes (SPCEs).

An electrochemical assay for the enzyme N-acetyl-beta-D-glucosaminidase (NAGase) is described, using bare screen-printed carbon electrodes (SPCEs). The enzyme substrate, 1-naphthyl-N-acetyl-beta-D-glucosaminide, was added to the NAGase-containing sample under hydrodynamic conditions and was hydrolysed to 1-naphthol, which was monitored amperometrically at an Eapp of +650 mV versus SCE. A pH study revealed the apparent Vmax for the assay to occur at pH 4.5. corresponding to an apparent substrate Km of 0.28 mM. In order to be compatible with the analysis of biological fluids, a final operating pH of 5.4 was selected, and, using a data recording time of 100 s post-substrate addition, the assay gave a linear response (r2 = 0.988) over the range 3.1 to 108 mU ml(-1) NAGase (RSD = 15.4%). This assay has the potential to monitor NAGase levels in a number of application areas.     

Synthesis of multi ring-fused 2-pyridones via an acyl-ketene imine cyclocondensation

[STRUCTURE: SEE TEXT] Polycyclic ring-fused 2-pyridones (5a-e and 9a-e) have been prepared via a microwave-assisted acyl-ketene imine cyclocondensation. Starting from 3,4-dihydroisoquinolines (4a-b) or 3,4-dihydroharman (8), fused 2-pyridones could be prepared in a one-step procedure. By using either Meldrum's acid derivatives (1a-d) or 1,3-dioxine-4-ones (7a-b) as acyl-ketene sources, mono- or disubstitution of the fused 2-pyridone ring could be accomplished. As an application of the method, a formal synthesis of the indole alkaloid sempervilam was performed.     

A calcium-sensitive microelectrode suitable for intracellular measurement of calcium(II) activity

A calcium-selective microelectrode with a l-μm diameter tip suitable for impaling single neurons has been developed. The electroactive material is di[p-(1,1,3,3-tetramethyl-butyl) phenyl] phosphoric acid (t-HDOPP). The selectivity coefficients are about 5 · 10^-7 for k_Ca,K, 1–4·10^-7 for k_Ca,Na, and 10^-3 for k_Ca,Mg. Values reported previously for other calcium-selective electrodes based on long-chain phenylphosphoric acids are given for comparison. The calcium-selective microelectrodes have a linear response in 0.2 M KCl solutions over the range 10^-2–10^-XXX M CaCl₂; 10^-7 and 10^-8 M CaCl₂ solutions containing 0.2 M KCl can be detected but the response is not linear.     

From Containers to Catalysts: Supramolecular Catalysis within Cucurbiturils

Cucurbiturils are a family of molecular container compounds with superior molecular recognition properties. The use of cucurbiturils for supramolecular catalysis is highlighted in this concept. Both photochemical reactions as well as thermal transformations are reviewed with an eye towards tailoring substrates for supramolecular catalysis mediated by cucurbiturils.