Ultraviolet light

About: Ultraviolet light is a research topic. Over the lifetime, 49494 publications have been published within this topic receiving 843151 citations.

Fabrication of poly(ethylene glycol) hydrogel microstructures using photolithography

Abstract: The fabrication of hydrogel microstructures based upon poly(ethylene glycol) diacrylates, dimethacrylates, and tetraacrylates patterned photolithographically on silicon or glass substrates is described. A silicon/silicon dioxide surface was treated with 3-(trichlorosilyl)propyl methacrylate to form a self-assembled monolayer (SAM) with pendant acrylate groups. The SAM presence on the surface was verified using ellipsometry and time-of-flight secondary ion mass spectrometry. A solution containing an acrylated or methacrylated poly(ethylene glycol) derivative and a photoinitiator (2,2-dimethoxy-2-phenylacetophenone) was spin-coated onto the treated substrate, exposed to 365 nm ultraviolet light through a photomask, and developed with either toluene, water, or supercritical CO2. As a result of this process, three-dimensional, cross-linked PEG hydrogel microstructures were immobilized on the surface. Diameters of cylindrical array members were varied from 600 to 7 micrometers by the use of different photomasks, while height varied from 3 to 12 micrometers, depending on the molecular weight of the PEG macromer. In the case of 7 micrometers diameter elements, as many as 400 elements were reproducibly generated in a 1 mm2 square pattern. The resultant hydrogel patterns were hydrated for as long as 3 weeks without delamination from the substrate. In addition, micropatterning of different molecular weights of PEG was demonstrated. Arrays of hydrogel disks containing an immobilized protein conjugated to a pH sensitive fluorophore were also prepared. The pH sensitivity of the gel-immobilized dye was similar to that in an aqueous buffer, and no leaching of the dye-labeled protein from the hydrogel microstructure was observed over a 1 week period. Changes in fluorescence were also observed for immobilized fluorophore labeled acetylcholine esterase upon the addition of acetyl acholine.

ATM phosphorylation of Nijmegen breakage syndrome protein is required in a DNA damage response.

Abstract: Nijmegen breakage syndrome (NBS) is characterized by extreme radiation sensitivity, chromosomal instability and cancer1 The phenotypes are similar to those of ataxia telangiectasia mutated (ATM) disease, where there is a deficiency in a protein kinase that is activated by DNA damage, indicating that the Nbs and Atm proteins may participate in common pathways Here we report that Nbs is specifically phosphorylated in response to γ-radiation, ultraviolet light and exposure to hydroxyurea Phosphorylation of Nbs mediated by γ-radiation, but not that induced by hydroxyurea or ultraviolet light, was markedly reduced in ATM cells In vivo, Nbs was phosphorylated on many serine residues, of which S343, S397 and S615 were phosphorylated by Atm in vitro At least two of these sites were underphosphorylated in ATM cells Inactivation of these serines by mutation partially abrogated Atm-dependent phosphorylation Reconstituting NBS cells with a mutant form of Nbs that cannot be phosphorylated at selected, ATM-dependent serine residues led to a specific reduction in clonogenic survival after γ-radiation Thus, phosphorylation of Nbs by Atm is critical for certain responses of human cells to DNA damage

Visible-Light-Driven N−F−Codoped TiO2 Photocatalysts. 2. Optical Characterization, Photocatalysis, and Potential Application to Air Purification

Abstract: N−F−codoped TiO2 (NFT) powders, prepared by spray pyrolysis (SP), were further characterized by ultraviolet−visible (UV−Vis) absorption spectroscopy and photoluminescence (PL) spectra. The UV−Vis spectra indicated that the NFT powders could absorb not only ultraviolet light like pure TiO2 powder but also part of the visible-light spectrum (λ < 550 nm). The PL spectra provided confirmation that four electronic energy states exist between the valence band and conduction band of N−F−codoped TiO2 that were attributed to F center, F+ center, an origin-unidentified energy state, and an impurity energy state formed by doped N atoms. Acetaldehyde decomposition was used as a probe reaction to evaluate the photocatalytic properties of these NFT powders. As a result, we found that the photocatalytic activity of the NFT powder prepared at the SP temperature of 1173 K was superior to that of commercial P25 under both UV and Vis irradiation. Moreover, trichloroethylene and toluene were selected as the other two target ...

Rad23 links DNA repair to the ubiquitin/proteasome pathway

Abstract: Rad23 is an evolutionarily conserved protein that is important for nucleotide excision repair1,2,3. A regulatory role has been proposed for Rad23 because rad23 mutants are sensitive to ultraviolet light but are still capable of incising damaged DNA4,5. Here we show that Rad23 interacts with the 26S proteasome through an amino-terminal ubiquitin-like domain (UbLR23). The carboxy terminus of Rad23 binds to the Rad4 DNA repair protein and creates a link between the DNA repair and proteasome pathways. The ultraviolet sensitivity caused by deletion of the UbLR23 domain may therefore arise from its inability to interact with the proteasome. The fusion proteins glutathione S-transferase (GST)–Rad23 and Rad4–haemagglutinin (HA), and the proteasome subunits Cim3 and Cim5, cofractionate through consecutive chromatography steps. The ubiquitin-like domain of human Rad23 (UbLHRB) also interacts with the human proteasome. These results demonstrate that ubiquitin-like domains (UbLs) represent a new class of proteasome-interacting motifs.