Electrochemical immobilisation of enzymes. Part 4.—Co-immobilisation of glucose oxidase and ferro/ferricyanide in poly(N-methylpyrrole) films

Glucose oxidase and ferro/ferricyanide can be co-immobilised in poly(N-methylpyrrole) films. The two species compete for incorporation into the films so that on increasing the concentration of enzyme in the growth solution less ferro/ferricyanide is incorporated into the film, and vice versa. The ferro/ferricyanide entrapped within the film acts as a redox mediator for the oxidation of the enzyme at 0.45 V vs. SCE. Studies of the effect of variation of film thickness, glucose concentration, enzyme loading and ferro/ferricyanide loading are consistent with a model in which diffusion and enzyme-catalysed reaction within the film are coupled. Analysis of data from these experiments allows the rate parameters for these processes to be determined. These data are compared with previous results for oxygen mediation in poly(N-methylpyrrole) films

2,5-Di-O-acetyl-3-C-methyl-D-lyxono-1,4-lactone

The structures of both lactones derived from the Kiliani ascension of 2-C-methyl-D-threose were defined by the crystal structure of the title compound, C10H14O7. The structure consists of hydrogen-bonded ribbons of molecules. © 2006 International Union of Crystallography All rights reserved

Green aldose isomerisation: 2-C-methyl-1,4-lactones from the reaction of Amadori ketoses with calcium hydroxide

Saccharinic acids, branched 2-C-methyl-aldonic acids, may be accessed via a green procedure from aldoses by sequential conversion to an Amadori ketose and treatment with calcium hydroxide; d-galactose and d-glucose are converted to 2-C-methyl-d-lyxono-1,4-lactone (with a small amount of 2-C-methyl-d-xylono-1,4-lactone) and 2-C-methyl-d-ribono-1,4-lactone. Inversion of configuration at C-4 of the branched lactones allows access to 2-C-methyl-l-ribono-1,4-lactone and 2-C-methyl-l-lyxono-1,4-lactone, respectively. d-Xylose affords 2-C-methyl-d-threono-1,4-lactone and 2-C-methyl-d-erythrono-1,4-lactone, whereas l-arabinose, under similar conditions, gave the enantiomers 2-C-methyl-l-threono-1,4-lactone and 2-C-methyl-l-erythrono-1,4-lactone. © 2006