Herein, we describe the first catalytic asymmetric intramolecular [4+2] cycloaddition of in situ generated ortho-quinone methides. In the presence of a confined chiral imidodiphosphoric acid catalyst, various salicylaldehydes react with dienyl alcohols to give transient ortho-quinone methide intermediates, which undergo an intramolecular [4+2] cycloaddition to provide highly functionalized fura...

UNLABELLED BACKGROUND Pyrroloquinoline quinone (PQQ), a tricarboxylic acid, has attracted attention as a growth factor, and its application to supplements and cosmetics is underway. The product used for these purposes is a water-soluble salt of PQQ disodium. Although in the past, PQQ disodiumpentahydrates with a high water concentration were used, currently, low hydration crystals of PQQ dis...

On the basis of crystal structures of the pyrroloquinoline quinone (PQQ) dependent enzymes methanol dehydrogenase (MDH) and soluble glucose dehydrogenase (s-GDH), different catalytic mechanisms have been proposed. However, several lines of biochemical and kinetic evidence are strikingly similar for both enzymes. To resolve this discrepancy, we have compared the structures of these enzymes in co...

Pyrroloquinoline quinone (PQQ) was immobilized on glassy-carbon electrodes (GCE) modified with single-walled carbon nanotubes (SWCNT), few-walled carbon nanotubes (FWCNT) and carbon black (Vulcan XC72R). Modified electrodes were prepared by drop-casting. Immobilization was achieved with an extremely simple dipping procedure and without any further modification to the electrodes. Electrochemical...

A large number of methanol-utilizing bacteria were screened for extracellular production of pyrroloquinoline quinone (PQQ) by using methanol as the carbon and energy sources. Of the bacteria selected, Hyphomicrobium sp. strain TK 0441 was examined for PQQ production by using a jar fermentor. The amount of PQQ in the broth and the level of methanol dehydrogenase activity in the cells were increa...

One electron reduction of Pyrroloquinoline quinone (PQQ) was studied using pulse radiolysis technique. Reactions of hydrated electron, H atom, radical and superoxide radicals produced very similar transient species. The radicals did not show decay in few milliseconds. The one-electron reduction potential of PQQ was determined at pH 7 using both methyl viologen and benzyl viologen couples and wa...

Transgenic Escherichia coli expressing pyrroloquinoline-quinone (PQQ) synthase gene from Deinococcus radiodurans showed superior survival during Rose Bengal induced oxidative stress. Such cells showed significantly low levels of protein carbonylation as compared to non-transgenic control. In vitro, PQQ reacted with reactive oxygen species with rate constants comparable to other well known antio...