Temperature-responsive stationary phase utilizing a polymer of proline derivative for hydrophobic interaction chromatography using an aqueous mobile phase.

A new method of chromatography is proposed, utilizing a thermo-responsive polymer carrying an amino acid ester residue for the stationary phase of high-performance liquid chromatography (HPLC). We have been investigating the new concept of chromatography, a temperature-responsive chromatography, using temperature-responsive poly(N-isopropylacrylamide) (PNIPAAm)-modified surface for HPLC with a constant aqueous media as the mobile phase. In this study, we designed and synthesized thermo-responsive poly(acryloyl-L-proline methyl ester) and its copolymer with N-isopropylacrylamide (NIPAAm). Homopolymers of acryloyl-L-proline methyl ester and copolymer were prepared by the reaction of radical telomerization. These polymers underwent a reversible phase transition from water-soluble forms into aggregates by changing the temperature, similar to PNIPAAm. The surface properties and functions of stationary phases modified with poly(acryloyl-L-proline methyl ester) were controlled by the external temperature. In the chromatographic system, we separated steroids and amino acids with a variety of hydrophobicities using a sole aqueous mobile phase. In contrast to a PNIPAAm-modified surface, a poly(acryloyl-L-proline methyl ester)-modified surface showed a greater affinity for hydrophobic amino acids.

Effect of alachlor on hepatic cytochrome P450 enzymes in rats.

Alachlor ((2-chloro-N-methoxymethyl)-N-(2,6-diethylphenyl)acetamide) is a widely used preemergence herbicide which has been classified by the USEPA as a probable human carcinogen. The herbicide has been suggested to be metabolized by hepatic cytochrome P450 system. We examined the effects of alachlor on cytochrome P450 enzymes in rat liver microsomes. Rats were treated intraperitoneally with alachlor daily for 5 days, at doses of 25, 50 and 100 mg/kg. Among the cytochrome P450-dependent monooxygenase activities, 7-pentoxyresorufin O-depentylase, which is associated with CYP2B1, was dose-dependently increased by alachlor. The induction relative to control activity was 1.7-4.2-fold. The activities of CYP1A-dependent monooxygenases such as 7-ethoxy-resorufin O-deethylase and acetanilide 4-hydroxylase were also significantly increased by alachlor at doses of 50 and 100 mg/kg (1.7-2.1-fold). Furthermore, immunoblotting showed that alachlor significantly increased CYP2B1/2 and CYP1A1/2 protein levels by 4.2-6.3- and 1.8-fold, respectively. Although 7-ethoxycoumarin O-deethylase, bufuralol 1'-hydroxylase and 4-nitrophenol 2-hydroxylase activities were significantly increased by alachlor at higher doses (> or = 50 mg/kg), the induction ratios were less than 1.6-fold. The activities of other cytochrome P450-dependent monooxygenases, namely testosterone 7 alpha-hydroxylase, testosterone 2 alpha-hydroxylase, testosterone 6 beta-hydroxylase and lauric acid omega-hydroxylase, were not affected by alachlor at any dose. In addition, there was no significant change in the protein levels of CYP2C11/6, CYP2D1, CYP2E1, CYP3A2/1 and CYP4A1/2/3. These results suggest that alachlor selectively induces cytochrome P450 isoforms of the CYP1A and CYP2B subfamilies in rat liver microsomes, and that the expression of these isoforms is closely related to the toxicity of alachlor.