Catechol hydroxylation

The CL enhancement of the lucigenin reaction with catecholamines in the presence of HTAH micelles was used for determination of dopamine, norepinephrine, and epinephrine [42], However, the presence of an anionic surfactant, SDS, inhibits the CL of the system. The aforementioned CL enhancement in the presence of HTAH can be explained in the following way the deprotonated forms of the catecholamines are expected to be the principal species present in aqueous alkaline solution due to the dissociation of the catechol hydroxyl groups, and to react with lucigenin to produce CL. The anionic form of the catecholamines and the hydroxide ion interact electrostatically with and bond to the cationic micelle, to which the lucigenin also bonds. Therefore, the effective concentration of the... 

The pKa of the catecholic hydroxyl is about 9.8. The role of the Mg2+ ion bound to the enzyme is to make the hydroxyl groups more easily ionizable. It has been shown by quantum mechanical calculations that the hydroxyl protons can be transferred to Lysl44 and Glul99 [24]. The proton transfer OH... 

From quantitative structure activity relationship studies (QSAR) of COMT inhibitors it became evident that the acidity of the catechol hydroxyl group is the most important factor that influences the inhibitory activity of catechol... 

Aspll33 32 in TM3 (Strader et al, 1989a), the catechol hydroxyls interact with serines in TM5 (Liapakis et al, 2000 Strader et al., 1989b Wieland et al, 1996). Interactions with the aromatic ring and the chiral /Mrydroxyl both have been mapped to TM6 (Wieland et al, 1996). 

The first blocker was not reported until I9S8, when Powell and Slater described the activity of dichloroisoprotcrcnol (DCI). The structure of DCI is like that of isoproterenol, except that the catechol hydroxyl groups have been replaced by two chloFO groups. This simple structural modification, involving the replacement of the aromatic hydroxyl groups. 

In the 1950s, dichloroisoproterenol (DCI, 100), a derivative of isoproterenol, in which the catechol hydroxyls had been replaced by... 

The conversion of hydroxyanthranilic acid to nicotinic acid in the rat has been shown unambiguously in isotopic experiments (344). Conversion to either quinolinic or nicotinic acids must involve open-chain intermediates such as A and B of diagram 21. Japanese workers (572) suggested that these were formed by scission between the catechol hydroxyls of the ring... 

When the B-ring possesses a catechol type structure, this nucleus acts mostly as a reducing agent. Once oxidized, it can undergo either coupled oxidation or Michael addition as a powerful electrophile, both mechanisms restore the catechol structure. The main grape anthocyanins, as their B-ring lacks the catechol hydroxylation pattern. 

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