PubMed · 4033430
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G Britton. 1985. General carotenoid methods.. https://doi.org/10.1016/s0076-6879(85)11007-4
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Lithographically patterned grids of photoresist, aluminum oxide, or gold on oxidized silicon substrates were used to partition supported lipid bilayers into micrometer-scale arrays of isolated fluid membrane corrals. Fluorescently labeled lipids were observed to diffuse freely within each membrane corral but were confined by the micropatterned barriers. The concentrations of fluorescent probe molecules in individual corrals were altered by selective photobleaching to create arrays of fluid membrane patches with differing compositions. Application of an electric field parallel to the surface induced steady-state concentration gradients of charged membrane components in the corrals. In addition to producing patches of membrane with continuously varying composition, these gradients provide an intrinsically parallel means of acquiring information about molecular properties such as the diffusion coefficient in individual corrals.
Ferric oxide (Fe2O3) and aluminum oxide (Al2O3) particles are widely encountered in occupational settings. Benzo[a]pyrene (B[a]P), a well-characterized environmental carcinogen, is frequently adsorbed onto particles. It has been shown that B[a]P-coated Fe2O3 particles (B[a]P-Fe2O3) significantly increased lung tumors in the hamster in contrast to B[a]P-coated Al2O3 (B[a]P-Al2O3) or B[a]P alone. In order to determine the genotoxic effects of these particles on the metabolism of B[a]P, pulmonary alveolar macrophages (AM) from male Syrian golden hamsters were incubated with 5 microg (19.8 nmol) B[a]P-coated respirable size (99% < 5 microm) Fe2O3 and Al2O3 particles with loads from 0.5 to 2.0 mg. Intracellular uptake of B[a]P by AM at 24 h was higher with B[a]P-Fe2O3 than that of B[a]P alone (P < 0.05) or B[a]P-Al2O3 (P < 0.05). Total B[a]P metabolism was significantly greater in AM exposed to B[a]P-coated Fe2O3 at 1.0 and 1.5 mg than in the AM exposed to B[a]p-al2O3 (0.5, 1.0 and 1.5 mg) (P < 0.05) or B[a]P alone (P < 0.05). Similar significant differences for Fe2O3 relative to Al2O3 and B[a]P alone were also apparent for total dihydrodiols, quinones and phenolic metabolites. Co-administration of 5 microg alpha-naphthoflavone (alpha-NF, an inhibitor of cytochrome P-4501A1 and P-4501A2) and 10(-3) M cyclohexene oxide (CO, an inhibitor of epoxide hydrolase) significantly reduced B[a]P metabolism in B[a]P-Fe2O3 (P < 0.05) and B[a]P-Al2O3 (P < 0.05) treated groups relative to B[a]P alone. AM were co-cultured with hamster tracheal epithelial cells (HTE) and treated as described above for metabolism studies to assess the DNA binding of B[a]P metabolites in the target cells, using 32P-postlabeling techniques. Two adducts were observed that had chromatographic behavior similar to 7R,8S,9S-trihydroxy-10R-(N2-deoxyguanosyl-3'-phosphate)-7,8,9,10-t etrahydrobenzo[a]pyrene [(+)-anti-BPDE-dG, adduct 1, major adduct representing 70-80% of total adducts] and 7S,8R,9R-trihydroxy-10S-(N2-deoxyguanosyl-3'-phosphate)-7,8,9,10-t etrahydrobenzo[a]pyrene [(-)-anti-BPDE-dG, adduct 2, representing 20-30% of total adducts]. B[a]P-Fe2O3 treatment enhanced the levels of the two B[a]P-DNA adducts in the HTE compared with B[a]P-Al2O3 (P < 0.05) or B[a]P alone. The inhibitors alphaNF and CO significantly reduced total adduct levels in the HTE (P < 0.05) in the B[a]P and B[a]P-Fe2O3 treatments as well as adduct 1 and adduct 2 levels. Our data suggest that the cocarcinogenic effect of B[a]P-Fe2O3 relative to B[a]P-coated Al2O3 can be due to: (i) the enhancement of B[a]P metabolism in AM by Fe2O3 associated with the increased uptake of B[a]P; and (ii) augmentation of DNA adduct formation in epithelial cells.
Psoralens are a class of pharmaceutical agents commonly used to treat several cutaneous disorders. When irradiated with a mode-locked titanium: sapphire (Ti:sapphire) laser tuned to 730 nm, an aqueous solution of 4'-hydroxymethyl-4,5',8-trimethylpsoralen (HMT) emits blue light. The emission spectrum is centered at 452 nm and is identical to that obtained by one-photon excitation with UVA excitation, and its magnitude depends quadratically on the intensity of laser excitation. These results suggest that two-photon excitation occurs to a potentially photochemically active state. To estimate the two-photon absorption cross section, it was first necessary to measure the emission quantum yield of HMT using 365 nm excitation at room temperature that resulted in a value of 0.045 +/- 0.007. The two-photon absorption cross section of HMT at 730 nm is therefore estimated to be 20 x 10(-50) cm4 s (20 Göppert-Mayer). The excited-state photophysics and photochemistry of psoralens suggest potential applications to cutaneous phototherapy in diseases such as psoriasis and dystrophic epidermolysis bullosa.