Photocatalytic activity of silicon nanowires under UV and visible light irradiation

The communication reports on the high performance of hydrogen-terminated silicon nanowires and silicon nanowires coated with metal (Ag, Cu) nanostructures for the photodegradation of rhodamine B under UV and visible light irradiation.     

Solar UV irradiation and dermal photoaging.

The skin is increasingly exposed to ambient UV-irradiation thus increasing risks for photooxidative damage with long-term detrimental effects like photoaging, characterized by wrinkles, loss of skin tone and resilience. Photoaged skin displays alterations in the cellular component and extracellular matrix with accumulation of disorganized elastin and its microfibrillar component fibrillin in the deep dermis and a severe loss of interstitial collagens, the major structural proteins of the dermal connective tissue. The unifying pathogenic agents for these changes are UV-generated reactive oxygen species (ROS) which deplete and damage non-enzymatic and enzymatic antioxidant defense systems of the skin. As well as causing permanent genetic changes, ROS activate cytoplasmic signal transduction pathways in resident fibroblasts that are related to growth, differentiation, senescence and connective tissue degradation. This review focuses on the role of UV-induced ROS in the photodamage of the skin resulting in clinical and biochemical characteristics of photoaging. In addition, the relationship of photoaging to intrinsic aging of the skin will be briefly discussed. A decrease in the overall ROS load by efficient sunscreens or other protective agents may represent promising strategies to prevent or at least minimize ROS-induced photoaging.     

Characterization and determination of piperine and piperine isomers in eggs

A new analytical method for the determination of piperine and its isomers in egg yolk and albumen is described here. All four isomers were separated by HPLC and detected using UV, DAD and electrochemical detection. The absolute detection limit (UV detection, S/ N=3) of a standard solution of piperine was 370 pg piperine. The correlation coefficients for the linear calibration graphs (concentration range: c=100 ng-10 micro g piperine isomer/mL) are generally better than 0.996. The piperine isomers were characterized and identified by spectroscopy (MS, (1)H-NMR, FT-IR). The method was successfully applied to the determination of piperine deposits in eggs (egg yolk and albumen) after feeding hens with piperine-spiked feed. The detection limit for piperine (24.8(+/-0.2) ng/g egg yolk and 37.9(+/-4.9) ng/g albumen) and the recoveries (70.3(+/-7.7)% (egg yolk) and 75.7(+/-1.9)% (albumen)) of piperine were determined.     

胡椒碱的提取、纯化及其抗癌活性的研究

本文利用溶剂法提取胡椒果中的胡椒碱成分,通过重结晶法纯化活性胡椒碱,并对其纯度和抗癌活性进行表征。结果表明,经分离纯化得到的胡椒碱纯度高达99.94%,并具有良好的抗癌效果。此外,运用密度泛函理论中B3LYP方法对胡椒碱的几何结构、相对能、热力学分布进行优化计算,建立和分析了胡椒碱的理论模型。所建立的能量最低的稳定胡椒碱理论模型符合热力学分布结果。     

Ageing of butyl rubber against UV irradiation

The photodegradation and stabilisation of butyl rubber have been studied in air in the temperature range of 258 to 318 K using a monochromatic light of 366 nm with a constant intensity flux of 1·68×10⁻⁸ einstein s⁻¹ cm⁻² in the absence and presence of cuprous di-isopropyl dithiophosphate. Irradiations were carried out on films at 0, 2, 4, 6, 8, 10, 12 and 14 h. An investigation into the nature and molecular changes during the irradiation with ultra-violet light (366 nm) of butyl rubber has been conducted by light scattering technique. The quantum yields of the photolysis of the polymer have been determined using a potassium ferrioxalate actinometer. Light scattering data have been processed to yield the activation energies in the absence and presence of 0·1 wt. % stabiliser. The incorporation of 0·7 wt. % cuprous di-isopropyl dithiophosphate in the matrix of the rubber film exercises the maximum protective influence on the photolytic degradation of the rubber.     

Production of CO by UV irradiation of acetylacetone

Photochemistry of hexafluoroacetylacetone has been studied by photoproduct analysis using infrared spectroscopy. Hexafluoroacetylacetone was irradiated by KrF excimer laser with the oscillation wavelength of 248 nm during 100 s and the photoproducts were analyzed by transmittance measurement of FT-IR in the spectral region between 3500 and 1300 cm⁻¹. One of the photoproducts was CO. It was estimated that the formation efficiency of CO was approximately 0.6.     

Polymerization of micelles under irradiation with UV light

Micelle formation behavior of sodium salts of fatty acids containing double bond at the chain end, sodium 10-undecenoate (Na-10-U) and sodium 8-nonenoate (Na-8-N), was examined with measurement of electric conductivity of their aqueous solutions, and the plot of the electric conductivity against the concentration for each fatty acid was found to show two break points; at 0,044 and 0,12mol/1 for Na-10-U and at 0,16 and 0,44 mol/1 for Na-8-N. The similar behaviors of the aqueous solutions were also found with the measurements of the maximum amount of solubilized benzene into the aqueous solution and of the solution viscosity, and the concentrations corresponding to the break points were assumed to be first and second critical micelle concentrations (CMC's), respectively. Polymerization of the sodium salts under irradiation with UV light was investigated. For each fatty acid, the amount of the obtained polymer was very small at very low concentrations of the fatty acid, but it increased rapidly with increasing concentration of the monomer at concentrations higher than the first CMC and then mildly at the concentrations higher than the second CMC. Number-average degrees of polymerization of the polymers obtained were measured with a gel permeation chromatography technique and found to be up to 13 for Na-10-U and 8,5 for Na-8-N.     

Preparation and characterization of DNA films induced by UV irradiation

Large amounts of DNA-enriched materials, such as salmon milts and shellfish gonads, are discarded as industrial waste. We have been able to convert the discarded DNA to a useful material by preparing novel DNA films by UV irradiation. When DNA films were irradiated with UV light, the molecular weight of DNA was greatly increased. The reaction was inhibited by addition of the radical scavenger galvinoxyl suggesting that the DNA polymerization with UV irradiation proceeded by a radical reaction. Although this UV-irradiated DNA film was water-insoluble and resistant to hydrolysis by nuclease, the structure of the DNA film in water was similar to non-irradiated DNA and maintained B-form structure. In addition, the UV-irradiated DNA film could effectively accumulate and condense harmful DNA-intercalating compounds, such as ethidium bromide and acridine orange, from diluted aqueous solutions. The binding constant and exclusion number of ethidium bromide for UV-irradiated DNA were determined to be 6.8 +/- 0.3 x 10(4) M(-1) and 1.6 +/- 0.2, respectively; these values are consisted with reported results for non-irradiated DNA. The UV-irradiated DNA films have potential uses as a biomaterial filter for the removal of harmful DNA intercalating compounds.     

Preparation and characterization of RF aerogel on UV irradiation method

The UV irradiation method provides us a new way of preparing resorcinol–formaldehyde (RF) aerogel. In this paper, water soluble, neutral photo-initiator 659 was used to synthesize RF aerogel by using free radical UV initiator. Incorporation of the UV initiators during the sol–gel stage usually decreases the gel-time. On changing the performed time and initiators quantities in synthesizing RF aerogel, The results will be discussed that gel-time of the RF aerogel definitely depends on the polymerization time and initiators quantities. The paper will also be discussed the RF aerogel developed for UV irradiation method and Sol–gel method by IR spectrum, Scanning electron microscopy, N₂ adsorption/desorption to show that light initiator does not play any role in the formation of the aerogel skeleton; The RF aerogel using UV irradiation method still maintain a high pore structure, shorter gel-time and the three-dimensional size block.     

IR-change and yellowing of polyurethane as a result of UV irradiation

In this investigation IR-change and yellowing of polyurethane as a result of UV radiation were studied. In the presence of UV radiation (200 h, λ > 300 nm), the synthesized aromatic polyurethane undergoes photodegradation with gradual change of its colour. The photochemical degradation of the polyurethane is associated with the scission of the urethane group and photooxidation of the central CH₂ group between the aromatic rings. These reactions are combined with the yellowing of the polyurethane surface. Analysis of the colour changes in PU surface during photodegradation was carried out by measuring CIEL^∗a^∗b^∗ colour components (L^∗,a^∗,b^∗ and ΔE_a,b^∗). FT-IR spectroscopy was used to study the chemical changes caused by UV irradiation. The colour difference of yellowing Δ_a,b^∗ exhibits a systematic tendency to higher values with increasing irradiation time. Overall, ΔE_a,b^∗ colour change correlates well with photodegradation of polyurethane by relative increase of the concentration of carbonyl group. Our results are in agreement with the quinone (yellow colour) formation as the chromophoric reaction product of polyurethane degradation.     

Solar UV irradiation conditions on the surface of Mars

The UV radiation environment on planetary surfaces and within atmospheres is of importance in a wide range of scientific disciplines. Solar UV radiation is a driving force of chemical and organic evolution and serves also as a constraint in biological evolution. In this work we modeled the transmission of present and early solar UV radiation from 200 to 400 nm through the present-day and early (3.5 Gyr ago) Martian atmosphere for a variety of possible cases, including dust loading, observed and modeled O3 concentrations. The UV stress on microorganisms and/or molecules essential for life was estimated by using DNA damaging effects (specifically bacteriophage T7 killing and uracil dimerization) for various irradiation conditions on the present and ancient Martian surface. Our study suggests that the UV irradiance on the early Martian surface 3.5 Gyr ago may have been comparable with that of present-day Earth, and though the current Martian UV environment is still quite severe from a biological viewpoint, we show that substantial protection can still be afforded under dust and ice.     

Photochemistry of uridine on high intensity laser UV irradiation

The method of high performance liquid chromatography was applied to investigate the products of single-quantum and two-quantum photo-reactions which occur when an aqueous solution of uridine is irradiated with high intensity nanosecond and picosecond laser UV pulses. A comparison of the experimental results obtained with theoretical models enables a number of photophysical parameters of the highly excited electronic states of the uridine molecule to be determined.     

Photocatalytic degradation of trichloroethylene over BiOCl under UV irradiation

In this study, BiOCl samples were synthesized under different pH values and characterized by XRD, SEM, UV‐vis DRS, BET, photoelectrochemical measurement and PL. The photocatalytic performances of the as‐prepared samples were evaluated through the decomposition of trichloroethylene (TCE) under UV irradiation. The influences of several parameters such as solution pH and common inorganic anions on TCE removal were investigated. Results indicated that BiOCl‐0.6 exhibited better photocatalytic performance than BiOCl‐6.0 because of its higher migration ability of photo‐induced carrier. The photocatalytic degradation of TCE over BiOCl‐0.6 followed pseudo first‐order kinetics and appeared to be more efficient in acidic solution than in alkaline. TCE was almost completely dechlorinated in 120 minutes. The inhibiting effect of naturally occurring anions was in the order of HCO₃^‐ >SO₄^2‐ >NO₃^‐, while Cl^‐ exhibited a dual effect. Moreover, BiOCl‐0.6 exhibited superior reusability after three cycles of repetition tests.     

Effect of UV irradiation on epidermal cell cytokine production

Within the last decade it has been found that the keratinocyte is not only a mechanical barrier to the outside but is also a fully immunocompetent cell that can release immunomodulating cytokines such as interleukin (IL) 1, IL 3, IL 6 and colony-stimulating factors (CSF). The constitutive production of these mediators by keratinocytes both in vivo and in vitro is very low; however, it can be dramatically enhanced by various stimuli such as tumour promotors or endotoxin. In addition, UV light is one of the most potent inducers of cytokine release. Accordingly, UV exposure results in increased production of IL 1, IL 3, IL 6, tumour necrosis factor and granulocyte/macrophage-CSF by epidermal cells. The secretion of these cytokines causes local immunologic and inflammatory reactions following UV irradiation. These factors, however, may also enter the circulation and thus may be responsible for systemic effects. In addition, UV light causes keratinocytes to release immunosuppressive factors which block contact hypersensitivity reaction and IL 1 activity. The production of such immunoinhibitors may play an essential pathogenic role during systemic UV-induced immunosuppression. This review will focus on the biological effects of epidermal-cell-derived cytokines, whose release is induced by UV light, and their role in immunologic and inflammatory reactions following UV exposure will be discussed.     

Morphological and compositional evolution of polymeric colloidal monolayer during UV irradiation

In this study, we investigated the morphological and compositional evolution polymeric colloidal monolayer during UV irradiation. A PS colloidal monolayer with interparticle bridges was prepared and exposed to the UV light. As a consequence of photochemical reactions containing chain-scission, UV irradiation induced morphological changes in the monolayer surface including changes in the size, shape, and packing structure of PS particles. By manipulating the UV irradiation time, fine tuning of size and shape of the interstice in the monolayer was achieved. In these procedures, the interparticle bridges play an important role. The UV irradiation induced the formation of polar groups in the PS particle surface and thus the particle surface became highly hydrophilic.     

Lipid composition greatly affects the in vitro surface activity of lung surfactant protein mimics

A crucial aspect of developing a functional, biomimetic lung surfactant (LS) replacement is the selection of the synthetic lipid mixture and surfactant proteins (SPs) or suitable mimics thereof. Studies elucidating the roles of different lipids and surfactant proteins in natural LS have provided critical information necessary for the development of synthetic LS replacements that offer performance comparable to the natural material. In this study, the in vitro surface-active behaviors of peptide- and peptoid-based mimics of the lung surfactant proteins, SP-B and SP-C, were investigated using three different lipid formulations. The lipid mixtures were chosen from among those commonly used for the testing and characterization of SP mimics--(1) dipalmitoyl phosphatidylcholine:palmitoyloleoyl phosphatidylglycerol 7:3 (w/w) (PCPG), (2) dipalmitoyl phosphatidylcholine:palmitoyloleoyl phosphatidylglycerol:palmitic acid 68:22:9 (w/w) (TL), and (3) dipalmitoyl phosphatidylcholine:palmitoyloleoyl phosphatidylcholine:palmitoyloleoyl phosphatidylglycerol:palmitoyloleoyl phosphatidylethanolamine:palmitoyloleoyl phosphatidylserine:cholesterol 16:10:3:1:3:2 (w/w) (IL). The lipid mixtures and lipid/peptide or lipid/peptoid formulations were characterized in vitro using a Langmuir-Wilhelmy surface balance, fluorescent microscopic imaging of surface film morphology, and a pulsating bubble surfactometer. Results show that the three lipid formulations exhibit significantly different surface-active behaviors, both in the presence and absence of SP mimics, with desirable in vitro biomimetic behaviors being greatest for the TL formulation. Specifically, the TL formulation is able to reach low-surface tensions at physiological temperature as determined by dynamic PBS and LWSB studies, and dynamic PBS studies show this to occur with a minimal amount of compression, similar to natural LS.     

DOSY NMR and MALDI‐TOF evidence of covalent binding the DNA duplex by trimethylammonium salts of topotecan upon near UV irradiation

Using DOSY NMR and MALDI‐TOF MS techniques, we present evidence that quaternary trimethylammonium salts of topotecan, [TPT‐NMe₃]⁺ X^? (X = CF₃SO₃, HCOO), bind covalently the natural DNA oligomer upon near UV irradiation in water under physiological conditions. It is shown that formate salt is very reactive at pH 7 and requires short irradiation time. This weak irradiation at 365 nm paves the way for a new application of TPT derivatives in clinical use, which can dramatically increase the therapeutic effects of a medicine. Copyright © 2015 John Wiley & Sons, Ltd.     

Inhibition of gamma ray-induced apoptosis by stimulatory heterotrimeric GTP binding protein involves Bcl-xL down-regulation in SH-SY5Y human neuroblastoma cells

Heterotrimeric GTP-binding proteins (G proteins) transduce extracellular signals into intracellular signals by activating effector molecules including adenylate cyclases that catalyze cAMP formation, and thus regulate various cellular responses such as metabolism, proliferation, and apoptosis. cAMP signaling pathways have been reported to protect cells from ionizing radiation-induced apoptosis, but however, the protective mechanism is not clear. Therefore, this study aimed to investigate the signaling molecules and the mechanism mediating the anti-apoptotic action of cAMP signaling system in radiation-induced apoptosis. Stable expression of a constitutively active mutant of Gas (GalphasQL) protected gamma ray-induced apoptosis which was assessed by analysis of the cleavages of PARP, caspase-9, and caspase-3 and cytochrome C release in SH-SY5Y human neuroblastoma cells. GasQL repressed the gamma ray-induced down-regulation of Bcl-xL protein, but transfection of Bcl-xL siRNA increased the gamma ray-induced apoptosis and abolished the anti-apoptotic effect of GasQL. GasQL decreased the degradation rate of Bcl-xL protein, and it also restrained the decrease in Bcl-xL mRNA by increasing the stability following ionizing irradiation. Furthermore, prostaglandin E2 that activates Gas was found to protect gamma ray-induced apoptosis, and the protective effect was abolished by treatment with prostanoid receptor antagonist specific to EP2/4R subtype. Moreover, specific agonists for adenosine A1 receptor that inhibits cAMP signaling pathway augmented gamma ray-induced apoptosis. From this study, it is concluded that Galphas-cAMP signaling system can protect SH-SY5Y cells from gamma ray-induced apoptosis partly by restraining down-regulation of Bcl-xL expression, suggesting that radiation-induced apoptosis can be modulated by GPCR ligands to improve the efficiency of radiation therapy.     

Photodegradation of polyglycidol in aqueous solutions exposed to UV irradiation

The photodegradation of polyglycidol in aqueous solution with UV wavelength of 254 nm was investigated. The experiments were carried out in air at a constant temperature and the photodegradation of polyglycidol (PGl) was compared to that of poly(ethylene oxide) (PEO), the most widely studied polyether. Size exclusion chromatography with multiangle light scattering detection (SEC-MALLS) was used to measure the changes in the molar masses and molar mass dispersities of polymers during degradation. The molar mass of PGl decreased dramatically during the first period of UV irradiation and then gradually approached a limiting value of 17,000 g/mol, regardless of the initial polymer concentration. PEO was less sensitive to UV irradiation than polyglycidol however, both polymers degrade mainly via chain scission. The degradation of PGl and PEO leads to acidification of their water solution. The photooxidation products were analyzed by FTIR and NMR spectroscopy and the spectrophotometric results revealed that the irradiation of the polymers led to the formation of carbonyl groups in the macromolecular chains. A mechanism accounting for the main routes of PGl photooxidation is proposed.