Chemiluminescent reaction of lucigenin with reducing sugars.
The chemiluminescent reaction, in alkaline solution, of lucigenin with the reducing sugars sorbose, fructose, lactose, glucose, xylose, galactose, arabinose and mannose has been studied. There is a linear relationship (correlation coefficient = 0.996) between the emission intensity and the second-order rate constant for the alkaline oxidation of these sugars. The emission intensity is linearly related to the sugar concentration; at high sugar concentrations (5mM) it is independent of the lucigenin concentration, but at low concentrations (<0.05mM) is linearly related to the lucigenin concentration. These facts support the view that the rate-limiting step is the tautomerization of the sugars to the 1,2-enediol form; the enediol then undergoes reaction with lucigenin.
Mechanism of alcohol-enhanced lucigenin chemiluminescence in alkaline solution.
The chemiluminescence (CL) of lucigenin (Luc(2+)) can be enhanced by different alcohols in alkaline solution. The effect of different fatty alcohols on the CL of lucigenin was related to the carbon chain length and the number of hydroxyl groups. Glycerol provides the greatest enhancement. UV/Vis absorption spectra and fluorescence spectra showed that N-methylacridone (NMA) was produced in the CL reaction in the presence of different alcohols. The peak of the CL spectrum was located at 470 nm in all cases, indicating that the luminophore was always the excited-state NMA. The quenching of lucigenin CL by superoxide dismutase (SOD) and the electron spin resonance (ESR) results with the spin trap of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) demonstrated that superoxide anions (O2 (•-)) were generated from dissolved oxygen in the CL reaction and that glycerol and dihydroxyacetone (DHA) can promote O2 (•-) production by the reduction of dissolved oxygen in alkaline solution. It was assumed that the enhancement provided by different alcohols was related to the solvent effect and reducing capacity. Glycerol and DHA can also reduce Luc(2+) into lucigenin cation radicals (Luc(•+) ), which react with O2 (•-) to produce CL, and glycerol can slowly transform into DHA, which is oxidized quickly in alkaline solution.
Catalytic removal of tert-butyldimethylsilyl (TBS) ether by PVP-I
Abstract A mild, efficient and rapid protocol the deprotection of alcoholic TBDMS ethers using PVP-1 as catalyst in methanol, the procedure of deprotection of various TBDMS ethers were found to be very convenient, easy work-up, high yielding.