Upon Ultraviolet Irradiation Research Articles

Molecular Design of Photocurable Liquid Biodegradable Copolymers. 2. Synthesis of Coumarin-Derivatized Oligo(methacrylate)s and Photocuring

Photocurable, biodegradable liquid copolymers, which undergo liquid-to-gel transformation upon ultraviolet (UV) light irradiation, may find versatile biomaterial applications. A multifunctionally derivatized liquid prepolymer that is oligo(2-hydroxyl methacrylate) grafted with oligo(e-caprolactone) and subsequently end-capped with a photodimerizable group, coumarin, at the terminal ends of the side chains, was prepared. UV irradiation produced a cross-linked solid.

Atomic force microscopy characterization and liquid crystal aligning effect of polymerizable diacetylene Langmuir Blodgett films

Abstract The surface topology of polymerizable diacetylenic lecithin Langmuir Blodgett (LB) films deposited on indium-tin oxide (ITO) coated glass substrates has been investigated using atomic force microscopic (AFM) techniques. The liquid crystal alignment effect of the LB films was compared to that of the random film formed by dipping the ITO glass into chloroform-lecithin solution. The orientation of a nematic monodomain based on these substrates was changed from homeotropic to tilted upon ultraviolet (UV) irradiation, and a planar alignment was achieved if the substrates were UV treated and buffed. AFM pictures reveal that the substrate surface corrugation is decreased by both random coating and LB film coating before photopolymerization. After UV irradiation, some unique star-like features were found on the monolayer LB film. These features provide evidence that the conformation of the diacetylene chains has been changed due to the photopolymerization, thus causing the liquid crystal orientation to undergo a transition from homeotropic to tilted alignment.

Ultraviolet action spectra for peroxide generation in human and pig epidermal keratinocytes loaded with dihydrorhodamine 123

We developed a new and simple method for measuring peroxides in a single living cell, and the generation of peroxides upon ultraviolet (UV) irradiation was measured in human and pig epidermal keratinocytes. The method was based on the fact that the non-fluorescent dye, dihydrorhodamine 123, reacts in the presence of peroxides, such as H2O2, and changes into the fluorescent rhodamine 123, and hence the fluorescence intensity is proportional to the amount of reacted peroxide. The epidermal keratinocytes were loaded with the dihydrorhodamine under a fluorescence microscope and exposed to UV radiation. Taking C as the content of peroxides generated within the cell and I as the increase in fluence (radiation intensity x time = photons/cm2), the following empirical relationship was established: C = Cs (1-exp(-kI)), where Cs is the content of peroxides at the saturation state, and k is a kinetic parameter. The dependence of the two parameters on wavelength in the range 280-400 nm was studied. In human keratinocytes Cs had a peak at 310 nm and a small peak (shoulder) at 380 nm, while k increased gradually toward shorter wavelengths. In pig keratinocytes, on the other hand, k had a peak around 380 nm and a shoulder at 330 nm, while Cs remained unchanged. Aminotriazole, an inhibitor of catalase, and low temperatures increased the stationary levels of peroxide generation in pig keratinocytes upon UV irradiation, indicating that the reaction used for measuring intracellular peroxides is competitive with the intrinsic reactions in scavenging peroxides.

Relative contribution of photo-addition, helper oligonucleotide and RNase H to the antisense effect of psoralen-oligonucleotide conjugates, on in vitro translation of Leishmania mRNAs

We investigated the properties of two antisense oligonucleotides, 11αPso and 14TMP, 11 and 14 nucleotides long, respectively, and conjugated to psoralen derivatives. These oligonucleotides were complementary to the mini-exon sequence of Leishmania amazonensis. Upon ultraviolet (UV) irradiation these oligomers were selectively cross-linked to DNA or RNA target sequences, either 14 or 35 nucleotides long. The yield of photo-addition was much lower on the longer targets than on the shorter ones, due to the presence of a hairpin structure. The co-addition of a helper oligonucleotide, whose binding site, on the 35-mer, was adjacent to that of the psoralen-derivatized antisense oligomer, improved the cross-linking efficiency. We then determined the effect of 14TMP on in vitro translation of Leishmania mRNA in cell-free extracts. Non-irradiated antisense oligonucleotide/mRNA complexes reduced the protein synthesis in wheat germ extract but not in rabbit reticulocyte lysate. Conversely, UV irradiation induced a 14TMP-dependent reduction of translation in reticulocyte lysate whereas the inhibition was not improved in the wheat germ extract. These results are discussed with respect to the involvement of RNase-H in the oligonucleotide-mediated effect on protein synthesis.

Inhibition of malonaldehyde formation from lipids by an isoflavonoid isolated from young green barley leaves

The inhibitory effect of 2″‐O‐glycosylisovitexin (2″‐O‐GIV), isolated from young green barley leaves, on malonaldehyde (MA) formation from lipids was determined by gas chromatography. Two μmol of 2″‐O‐GIV inhibited MA formation from 0.2 mmol of squalene by almost 100% upon ultraviolet (UV) irradiation. Only 1 μmol of 2″‐O‐GIV inhibited 90% of MA formation from 0.2 mmol of ethyl linoleate upon UV irradiation. The effective quantities of 2″‐O‐GIV were much lower than those of either butylated hydroxytoluene or α‐tocopherol. When ethyl linoleate, ethyl linolenate and ethyl arachidonate were oxidized by Fenton’s reagent in the presence of 2″‐O‐GIV or α‐tocopherol, both compounds showed similar activity toward MA formation. Both compounds gave maximum inhibition at doses of 0.1–0.3 μmol for ethyl linoleate, 0.1–0.5 μmol for ethyl linolenate and 0.1–0.5 μmol for ethyl arachidonate.

Photo Induced Surface Heparin Immobilization

This paper describes a novel method providing durable layering of heparin immobilized hydrogels on fabricated devices. The preparation method is based on photochemistry of a dithiocarbamate group that is dissociated into a highly reactive radical pair upon ultraviolet (UV) irradiation. By taking advantage of characteristics of the photo generated radicals, hydrogel formation and its fixation onto a substrate surface were attained. The immobilization of heparin onto poly(ethylene terephtalate) was demonstrated. First, a mixed aqueous solution containing a photoreactive water soluble poly(N,N-dimethylacrylamide-covinylbenzyl N,N-diethyldithiocarbamate) and heparin was coated on the substrate. Subsequent UV irradiation resulted in the simultaneous formation of a heparin immobilized hydrogel and its chemical fixation onto the substrate. No delamination was found after vigorous washing with water. Significant inhibition of platelet adhesion and markedly prolonged blood coagulation times were observed, which are apparently derived from the surface hydrogel, and from released and chemically fixed surface heparin. Thus, it is expected that the photochemical method developed here provides potent antithrombogenicity to artificial organs.