Dietary constituents (e.g., in grapefruit juice; NaCl) and phytochemicals (e.g., St. John's wort) are important agents modifying drug metabolism and transport and thereby contribute to interindividual variability in drug disposition. Most of these drug-food interactions are due to induction or inhibition of P-glycoprotein and/or CYP3A4. Preliminary data indicate that piperine, a major component of black pepper, inhibits drugmetabolizing enzymes in rodents and increases plasma concentrations of several drugs, including P-glycoprotein substrates (phenytoin and rifampin) in humans. However, there are no direct data whether piperine is an inhibitor of human Pglycoprotein and/or CYP3A4. We therefore investigated the influence of piperine on P-glycoprotein-mediated, polarized transport of digoxin and cyclosporine in monolayers of Caco-2 cells. Moreover, by using human liver microsomes we determined the effect of piperine on CYP3A4-mediated formation of the verapamil metabolites D-617 and norverapamil. Piperine inhibited digoxin and cyclosporine A transport in Caco-2 cells with IC 50 values of 15.5 and 74.1 M, respectively. CYP3A4-catalyzed formation of D-617 and norverapamil was inhibited in a mixed fashion, with K i values of 36 Ϯ 8 (liver 1)/49 Ϯ 6 (liver 2) and 44 Ϯ 10 (liver 1)/77 Ϯ 10 M (liver 2), respectively. In summary, we showed that piperine inhibits both the drug transporter P-glycoprotein and the major drug-metabolizing enzyme CYP3A4. Because both proteins are expressed in enterocytes and hepatocytes and contribute to a major extent to first-pass elimination of many drugs, our data indicate that dietary piperine could affect plasma concentrations of P-glycoprotein and CYP3A4 substrates in humans, in particular if these drugs are administered orally.Several dietary constituents and phytochemicals are now identified as important factors affecting drug disposition

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The viral RNA segments in influenza virions were shown to be circular in conformation by using psoralen crosslinking methods. Electron microscopy of purified RNA following treatment of virus with the psoralen reagent 4'-aminomethyltrioxsalen (AMT) revealed circles with lengths corresponding to the individual segments. RNA blot analysis using polyacrylamide gels demonstrated that RNA from AMTtreated virus had a slowed migration, consistent with it being a single-stranded circle. Furthermore, nuclease S1 protection assays indicated that the termini of the RNA segments form an approximately 15-base-pair-long panhandle. This structure is consistent with the partial sequence complementarity that has been observed for the termini of all influenza virus RNAs. By RNA blot analysis, circular structures of viral sense RNA were also found in influenza virus-infected cells at early and late time points. The circular RNA was the predominant species at the time when the major transcription product is message RNA. This finding and the observation that the termination signal for mRNA synthesis directly abuts the panhandle suggest that a panhandle in the template viral RNA is a cis regulatory signal promoting the synthesis of mRNA instead of plus-sense template. Also, since the panhandle is present in high concentration in virions, we suggest that it is required for packaging and that the input RNA after infection is in the proper conformation for synthesis of primary transcripts.Influenza A virus contains eight negatively stranded RNA segments that encode at least 10 distinct proteins (for review, see ref. 1). The core of the virus consists of eight individual nucleocapsids, which are made up of the RNA segments, the three polymerase (P) proteins, and nucleoprotein molecules (NP). Early analyses revealed that these nucleocapsids have different molecular weights (2) and that they appear as strands (3) that show loops at one end. The tertiary structure is formed by folding back on itself and coiling, which results in a large double helix (3, 4). The lengths of the nucleocapsid strands can be correlated with the molecular weights of the viral RNA segments. Also, the presence of multiple nucleocapsid segments correlates with the finding that the mRNAs are transcribed independently (5, 6). Each of the nucleocapsids directs the synthesis of complementary RNA starting from the 3' ends of the virion RNAs (7). Although sequencing studies of the 3' and 5' termini of influenza A, B, and C virus RNAs revealed the presence of inverted complementary sequences (8-10), it was not known whether the termini actually basepair in ribonucleoprotein complexes.In the present study, we show that UV crosslinking of virion RNAs in the presence of 4'-substituted psoralen leads to circular RNA structures. This finding supports the proposition that stable hairpin structures involving the RNA termini are present in infectious influenza virus particles. In addition, we find that the viral RNA in infected cells is predominantly circular during the pha...

Poly(ethylene oxide)-covered CdSe nanorods were prepared and assembled in diblock copolymer templates by floating the block copolymer templates onto aqueous nanorod solutions. The assembly was enabled by consideration of the surface ligand coverage of the nanorods. Alkane-covered CdSe nanorods prepared by state-of-the-art techniques are not compatible with this assembly process. However, poly(ethylene oxide) (PEO)-functionalized CdSe nanorods were successfully used to assemble the nanorods into the channels and pores of diblock copolymer templates. Other water-dispersible CdSe nanorods, such as those covered with 11-mercaptoundecanoic acid (MUA), did not give the desired assemblies. These results are understood by considering the surface energies of the PEO-covered CdSe nanorods in this interfacial assembly process.

Producing densely packed arrays of nanoscopic anisotropic objects, while necessary for applications in photovoltaic and field emission devices, presents considerable challenges. Here, we present findings on the phase separation of ligand-functionalized nanorods in a polymer matrix under an applied electric field. Densely packed hexagonal arrays of nanorods are produced by this method, where the rods are oriented in the direction of the applied field. Minimization of interfacial energy between the array of nanorods and the surrounding polymer serves to corral the nanorods into the densely packed arrays observed. These findings carry implications toward advancing organic-inorganic heterojunction photovoltaic devices that are expected to benefit from the oriented, densely packed ordered arrays of nanorods produced here.