Tyrosinases (sometimes referred to as polyphenol oxidases, monophenol monoxygenases, catechol
oxidases, cre-solases, or catecholases) are well known for their role in producing melanin in vertebrates.
The first step in aniline conversion to catechol
is a multistep reaction catalyzed by three enzymes, a glutamine synthetase (GS)-like enzyme, aniline dioxygenases and glutamine amidotransferase like enzyme (Liang et al., 2005; Murakami et al., 1998).
(CT), hydroquinone (HQ), and KCl were purchased from Sigma-Aldrich, and graphite (G) (>99%) was purchase from Fluka.
First, commercially available 3,4-dihydroxybenzaldehyde was converted to the corresponding catechol
aldehyde (2) by reacting it with compound 1.
Laccase from Trametes versicolor (EC 18.104.22.168), with an activity of 13.6 U/mg, was obtained from Sigma; sodium acetate trihydrate was from JT Baker; acetic acid glacial was from Laboratorios Lutz, Mexico, 60.05%; caffeic acid, gallic acid, and catechol
were from Fluka; ethanol was from Sigma-Aldrich (HPLC degree); Hg[(N[O.sub.3]).sub.2] was from Sigma-Aldrich; and deionized water was from a MilliQ Millipore equipment.
(Sigma-Aldrich, Germany) as substrate in concentrations of 0.0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11 and 0.120M was prepared, and 3ml of each concentration was placed into a quartz cell along with 75[micro]l of each inhibitor or their combinations.
The researchers applied polyphenol coatings to the surface of chitosan-grafted polypropylene by using the laccase-assisted oxidative polymerization of catechol
For it, 0.5 mL phosphate buffer (0.1 M, PH7) was added to 200 uL enzyme solution and 200 uL catechol
Alternatively, reactive oxygen species (ROS) generated from redox cycling of both stilbene and catechol
estrogens can act as signaling messengers also that are also involved in cell growth [7, 12, 13].
The chemical features were combined as follows: catechol
(ring B: 3,,4,-diOH), pyrogallol (ring B: 3',4',5'-triOH), C2=C3 + C4-C=O (double bond between C2-C3 and the presence of carbonyl on the carbon 4), C4-C=O + C5-OH (carbonyl on the carbon 4 and the presence of -OH on the carbon 5), C7-OH + C8-OH (presence of -OH group on the carbons 7 and 8), C3-OH + C4=O + C5-OH (presence of a carbonyl group and -OH groups on the carbon 3 and 5), catechol
+ C2=C3 + C4-C=O, catechol
+ C4-C=O + C5-OH, pyrogallol + C2=C3 + C4-C=O, and pyrogallol + C4-C=O + C5-OH.
By using catechol
as the enzymatic substrate, the amperometric response was linear of 1.3 x [10.sup.-8] to 1.5 x [10.sup.-4] mol [L.sup.-1], with a limit of detection of 6.0 x [10.sup.-9] mol [L.sup.-1].
Multidentates [beta]-diketonates biscatecholamide ligands  have six binding sites due to the O-donor of catechol
aromatic ring and [beta]-diketonates [7, 8].