| Résumé | A substrate recycling assay for phenolic compounds was developed using tyrosinase in excess NADH. The reaction of various phenols with the enzyme produced an o-quinone, which was then detected by recycling between reactions with the enzyme and NADH. Absorbance measurements of the NADH consumption rate enhanced the assay sensitivity for catechol 100-fold compared to non-recycling o-quinone detection, giving a detection limit of 240 nM. Fluorescence NADH monitoring permitted a further tenfold improvement over absorbance, with a detection limit of 23 nM. The procedure was useful for assaying catechol, several derivatives of catechols, including chloro and amine derivatives, phenols, and 4-chlorophenol, with relative sensitivity being related to substrate activity of the enzyme.
α- β - γ-, and 2-hydroxypropyl-β-cyclodextrins were capable of forming water-soluble inclusion complexes with several polynuclear aromatic hydrocarbons (PAHs). The highest solubilities were noted for the βcyclodextrin and 2-hydroxypropyl-β-cyclodextrin (hpβCD). The solubility of PAHs in hpβCD compared with pure water was enhanced 224-fold and 7, 500-fold for naphthalene and benzo(a)pyrene, respectively, with other PAHs yielding values between these limits. The lignin peroxidase enzyme oxidized anthracene, pyrene, and benzo(a)pyrene and exhibited a preference to oxidize either anthracene or benzo(a)pyrene when mixed with pyrene. Based on fluorescence measurement, anthracene and benzo(a)pyrene were easily distinguished by exciting at 250 nm for anthracene and 295 nm for benzo(a)pyrene. |
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