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An efficient molecularly imprinted solid-phase extraction protocol was developed for the separation of dopamine (DA) from human urine. After successful validation of the analytical method using high-performance liquid chromatography coupled with fluorescence detection, a new strategy for the selective determination of DA in the presence of norepinephrine and epinephrine in human urine was presented. In the proposed protocol, the LODs and quantification for DA were 166 ± 36 and 500 ± 110 nmol/L, respectively, and the total recoveries of DA in the range of 1-15 μmol/L varied between 98.3 and 101.1%. DA was detected in the real urine samples at the level of 47-167 μg/L (0.250-0.895 μmol/L). The superiority of the novel analytical strategy was shown by comparison with the results obtained for a commercially available imprinted sorbent.

Modeling, mutagenesis, and kinetic studies have demonstrated that the substrate-binding site of cytochrome P450 is composed of multiple interactive regions that are capable of simultaneously binding two or more xenobiotics. Substrate molecules can interact with each other after docking. Thus, substrates can compete for the activated oxygen–ferrous complex or alter the spatial orientation of other molecules. Cytochrome P450 is a unique enzyme that produces n-heptane metabolites of different oxidation states. Metabolism of n-heptane was investigated with rat liver microsomes and a reconstituted rat liver system. Ethanol, n-propanol, and n-butanol molecules interacted with the n-heptane molecule and resulted in cytochrome P450 spectral changes as well as alterations in the n-heptane metabolic profile. The observed modifications in the biotransformation of n-heptane indicated that there are three distinct pathways for oxidation of n-heptane to heptanols, heptanones, and one-side oxygen-oriented heptanediones. © 2009 Wiley Periodicals, Inc. J Biochem Mol Toxicol 23:287–294, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20291