3 research outputs found
Mercury pollution for marine environment at Farwa Island, Libya
Coimmobilization of pyranose dehydrogenase
as an enzyme catalyst,
osmium redox polymers [OsĀ(4,4ā²-dimethoxy-2,2ā²-bipyridine)<sub>2</sub>(polyĀ(vinylimidazole))<sub>10</sub>Cl]<sup>+</sup> or [OsĀ(4,4ā²-dimethyl-2,2ā²-bipyridine)<sub>2</sub>(polyĀ(vinylimidazole))<sub>10</sub>Cl]<sup>+</sup> as mediators,
and carbon nanotube conductive scaffolds in films on graphite electrodes
provides enzyme electrodes for glucose oxidation. The recombinant
enzyme and a deglycosylated form, both expressed in Pichia pastoris, are investigated and compared as
biocatalysts for glucose oxidation using flow injection amperometry
and voltammetry. In the presence of 5 mM glucose in phosphate-buffered
saline (PBS) (50 mM phosphate buffer solution, pH 7.4, with 150 mM
NaCl), higher glucose oxidation current densities, 0.41 mA cm<sup>ā2</sup>, are obtained from enzyme electrodes containing the
deglycosylated form of the enzyme. The optimized glucose-oxidizing
anode, prepared using deglycosylated enzyme coimmobilized with [OsĀ(4,4ā²-dimethyl-2,2ā²-bipyridine)<sub>2</sub>(polyĀ(vinylimidazole))<sub>10</sub>Cl]<sup>+</sup> and carbon
nanotubes, was coupled with an oxygen-reducing bilirubin oxidase on
gold nanoparticle dispersed on gold electrode as a biocathode to provide
a membraneless fully enzymatic fuel cell. A maximum power density
of 275 Ī¼W cm<sup>ā2</sup> is obtained in 5 mM glucose
in PBS, the highest to date under these conditions, providing sufficient
power to enable wireless transmission of a signal to a data logger.
When tested in whole human blood and unstimulated human saliva maximum
power densities of 73 and 6 Ī¼W cm<sup>ā2</sup> are obtained
for the same fuel cell configuration, respectively
Anthropometric characteristics separated by soccer players, ski racers and comparison group.
<p>Anthropometric characteristics separated by soccer players, ski racers and comparison group.</p
Further Insights into the Catalytical Properties of Deglycosylated Pyranose Dehydrogenase from Agaricus meleagris Recombinantly Expressed in Pichia pastoris
The
present study focuses on fragmented deglycosylated pyranose
dehydrogenase (fdgPDH) from Agaricus meleagris recombinantly expressed in Pichia pastoris. Fragmented deglycosylated PDH is formed from the deglycosylated
enzyme (dgPDH) when it spontaneously loses a C-terminal fragment when
stored in a buffer solution at 4 Ā°C. The remaining larger fragment
has a molecular weight of ā¼46 kDa and exhibits higher volumetric
activity for glucose oxidation compared with the deglycosylated and
glycosylated (gPDH) forms of PDH. Flow injection amperometry and cyclic
voltammetry were used to assess and compare the catalytic activity
of the three investigated forms of PDH, āwiredā to graphite
electrodes with two different osmium redox polymers: [OsĀ(4,4ā²-dimethyl-2,2ā²-bipyridine)<sub>2</sub>(polyĀ(vinylimidazole))<sub>10</sub>Cl]<sup>+</sup> [OsĀ(dmbpy)ĀPVI]
and [OsĀ(4,4ā²-dimethoxy-2,2ā²-bipyridine)<sub>2</sub>(poly-(vinylimidazole))<sub>10</sub>Cl]<sup>+</sup> [OsĀ(dmobpy)ĀPVI]. When āwiredā
with OsĀ(dmbpy)ĀPVI, the graphite electrodes modified with fdgPDH showed
a pronounced increase in the current density with <i>J</i><sub>max</sub> 13- and 6-fold higher than that observed for gPDH-
and dgPDH-modified electrodes, making the fragmented enzyme extraordinarily
attractive for further biotechnological applications. An easier access
of the substrate to the active site and improved communication between
the enzyme and mediator matrix are suggested as the two main reasons
for the excellent performance of the fdgPDH when compared with that
of gPDH and dgPDH. Three of the four glycosites in PDH: N<sup>75</sup>, N<sup>175</sup>, and N<sup>252</sup> were assigned using mass spectrometry
in conjunction with endoglycosidase treatment and tryptic digestion.
Determination of the asparagine residues carrying carbohydrate moieties
in PDH can serve as a solid background for production of recombinant
enzyme lacking glycosylation