-It is important for toxicological assessment of nanoparticles to determine the penetration of nanoparticle in skin qualitatively and quantitatively. Skin penetration of four different types of rutile titanium dioxide (TiO 2 ) (T-35, 35 nm, non-coating; TC-35, 35 nm, with almina/silica/silicon coating; Tdisp, 10 x 100 nm, mixture of almina coated and silicon coated particles, dispersed in cyclopentasiloxan; T-250, 250 nm, non-coating) was determined with in vitro intact, stripped, and hair-removed skin of Yucatan micropigs to study the effect of dispersion and skin conditions. The TiO 2 was suspended in a volaapplied at a dose 2 μl/cm 2 for 24 hr, followed by cyanoacrylate stripping. The Ti concentration in skin was determined by ICP-MS. T-35 and T-250 easily aggregated in suspension with a mean diameter greater than 1 μm. TC-35 and T-disp showed good dispersion properties with a mean diameter in suspension of approximately 100 nm. No penetration was observed regardless of TiO 2 type in intact and stripped skin.SEM-EDS observation showed that Ti penetrated into vacant hair follicles (greater than 1 mm below the skin surface), however, it did not penetrate into dermis or viable epidermis.

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The cullin-containing ubiquitin-protein isopeptide ligases (E3s) play an important role in regulating the abundance of key proteins involved in cellular processes such as cell cycle and cytokine signaling. They have multisubunit modular structures in which substrate recognition and the catalysis of ubiquitination are carried out by distinct polypeptides. In a search for proteins involved in regulation of cullin-containing E3 ubiquitin ligases we immunopurified CUL4B-containing complex from HeLa cells and identified TIP120A as an associated protein by mass spectrometry. Immunoprecipitation of cullins revealed that all cullins tested specifically interacted with TIP120A. Reciprocal immunoaffinity purification of TIP120A confirmed the stable interaction of TIP120A with cullin family proteins. TIP120A formed a complex with CUL1 and Rbx1, but interfered with the binding of Skp1 and F-box proteins to CUL1. TIP120A greatly reduced the ubiquitination of phosphorylated I B␣ by SCF ␤-TrCP ubiquitin ligase. These results suggest that TIP120A functions as a negative regulator of SCF E3 ubiquitin ligases and may modulate other cullin ligases in a similar fashion.The ubiquitin-dependent proteolysis provides a fundamental mechanism for regulating protein activity in various processes ranging from cell cycle and developmental switches to signal transduction (1). This process begins with the attachment of a multiubiquitin chain to a target protein and involves several enzymatic activities. A ubiquitin-activating enzyme (E1) 1 activates ubiquitin in an ATP-dependent reaction by forming a thioester bond with the C-terminal glycine of ubiquitin. The ubiquitin is then transferred to a specific sulfhydryl group on a ubiquitin-conjugating enzyme (E2). A ubiquitin-protein ligase (E3) transfers the activated ubiquitin from E2 to a lysine residue of a bound substrate, forming an isopeptide bond. Substrate specificity is determined mainly by E3s which bind both the protein substrate and the cognate E2. Once the multiubiquitin chain is assembled on a protein substrate by the cooperation of E1, E2, and E3 enzymes, the target protein is recognized and degraded by the 26 S proteasome (1-3).In mammalian cells, a wide variety of E3s are found. The cullin family proteins play an important role in a group of multisubunit E3 ubiquitin ligases by associating with an Rbx1 (also known as ROC1 and Hrt1) family member of RING finger proteins to form the integral core (4). The SCF complexes are the best characterized ones of this class (5). They consist of CUL1, Rbx1, Skp1, and an F-box protein. Rbx1 contains the RING-H2 finger domain, forms a catalytic core with CUL1, and recruits the cognate E2 (6 -8). Skp1 functions as an adaptor that links an F-box protein to CUL1 (9). Substrates of the SCF complexes are bound by F-box proteins, which contain the Skp1-binding F-box motif and a variable protein-protein interaction domain that directly interacts with substrates (9, 10). Since a large number of F-box proteins are encoded by eukaryotic genomes (11-13), ...

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A graded-index polymer optical fiber containing rhodamine 6G in poly(methyl methacrylate-co-2-hydroxyethyl methacrylate) has been fabricated. Lasing behavior of the fiber was observed by pumping with a frequency-doubled Q-switched Nd: yttrium–aluminum–garnet laser. A slope efficiency of 43% and a lifetime of 110 000 shots at a repetition rate of 10 Hz have been observed. With a 1.5 mJ pump energy, an output energy of 640 μJ was produced.

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