| 1. |
- Aucamp, Pieter J., et al.
(författare)
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Questions and answers about the environmental effects of ozone depletion and its interactions with climate change: 2010 assessment
- 2011
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Ingår i: Photochemical and Photobiological Sciences. - : Springer Science and Business Media LLC. - 1474-9092 .- 1474-905X. ; 10:2, s. 301-316
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Forskningsöversikt (refereegranskat)abstract
- In the mid-1970s it was discovered that some man-made products destroy ozone molecules in the stratosphere. This destruction leads to higher ultraviolet (UV) radiation levels at the surface of the Earth and can cause damage to ecosystems and to materials such as plastics. Itmay cause an increase in human diseases such as skin cancers and cataracts. The discovery of the role of the synthetic ozone-depleting chemicals, such as the chlorofluorocarbons (CFCs), stimulated increased research and monitoring in this field. Computer models predicted a disaster if nothing was done to protect the ozone layer. Based on this scientific information, the nations of the world took action in 1985 with the Vienna Convention for the Protection of theOzone Layer, followed by the Montreal Protocol on Substances that Deplete the Ozone Layer in 1987. The Convention and Protocol have been amended and adjusted several times since 1987 as new knowledge has become available. The Meetings of the Parties to the Montreal Protocol appointed three Assessment Panels to regularly review research findings and progress. These panels are the Scientific Assessment Panel, the Technological and Economic Assessment Panel and the Environmental Effects Assessment Panel. Each panel covers a designated area with a natural degree of overlap. Themain reports of the Panels are published every four years, as required by the Meeting of the Parties. All three reports have an executive summary that is distributed more widely than the entire reports. It has become customary to add a set of questions and answers – mainly for non-expert readers – to these executive summaries. This document contains the questions and answers prepared by the experts of the Environmental Effects Assessment Panel. They refer mainly to the environmental effects of ozone depletion and its interactions with climate change, based on the 2010 report of this Panel, but also on information from previous assessments and from the report of the Scientific Assessment Panel. Readers who need further details on any question should consult the full reports for a more complete scientific discussion. All these reports can be found on the UNEP website: http://ozone.unep.org.
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| 2. |
- Blake, Jessie A, et al.
(författare)
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Design of xanthone propionate photolabile protecting group releasing acyclovir for the treatment of ocular herpes simplex virus
- 2012
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Ingår i: Photochemical and Photobiological Sciences. - : Royal Society of Chemistry. - 1474-905X .- 1474-9092. ; 11:3, s. 539-547
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Tidskriftsartikel (refereegranskat)abstract
- We have attached the antiviral drug acyclovir (ACV) to a xanthone photolabile protecting group (or photocage) through the O6 position of acyclovir, a procedure designed for the treatment of ocular herpes simplex virus infections. Acyclovir is photoreleased from the photocage, under physiological conditions, with a quantum yield (Phi(ACV release)) of 0.1-0.3 and an uncaging cross section (Phi.epsilon) of 450-1350 M cm(-1). We demonstrate that this photorelease method outcompetes alternative reaction pathways, such as protonation. Furthermore, complete release of the drug is theoretically possible given a sufficient dose of light. Surprisingly the acyclovir photocage, also showed some antiviral activity towards HSV-1.
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| 3. |
- Friedli, Peter, et al.
(författare)
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Dye-injected electron trapping in TiO2 determined by broadband transient infrared spectroscopy.
- 2014
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Ingår i: Photochemical and Photobiological Sciences. - : Springer. - 1474-905X .- 1474-9092. ; 13:10, s. 1393-6
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Tidskriftsartikel (refereegranskat)abstract
- We report the dynamics of electrons injected into TiO2 due to the excitation of Ru-N719 dye at 532 nm. The synchrotron based broadband transient mid-IR spectroscopy revealed that the injected electrons are quickly confined to a trap state with an average energy of ca. 240 meV below the conduction band. The average energy of the trapping states did not change with the increase of the delay time, suggesting a singular electronic identity of the trap states.
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| 4. |
- Gonzalez, Helena, 1971
(författare)
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Percutaneous absorption with emphasis on sunscreens.
- 2010
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Ingår i: Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology. - : Springer Science and Business Media LLC. - 1474-9092. ; 9:4, s. 482-8
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Tidskriftsartikel (refereegranskat)abstract
- Sunscreens are widely used products. When recreationally used they are applied to large areas of the skin repeatedly. In moisturizers and foundation it is common to find sun protective ingredients, in these cases the product is usually applied to smaller areas but often done daily. Active ingredients in sunscreens can be absorbed by the skin. Percutaneous absorption is an important factor to take into consideration. There are several methods to measure the percutaneous absorption, both in vivo and/or in vitro. This paper will give an overview of the different methods.
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| 5. |
- Jesorka, Aldo, 1967, et al.
(författare)
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Water coordinated zinc dioxo-chlorin and porphyrin self-assemblies as chlorosomal mimics: Variability of supramolecular interactions
- 2012
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Ingår i: Photochemical and Photobiological Sciences. - : Springer Science and Business Media LLC. - 1474-9092 .- 1474-905X. ; 11:6, s. 1069-1080
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Tidskriftsartikel (refereegranskat)abstract
- Semisynthetic zinc chlorins are shown for the first time to self-assemble in the absence of an intrinsic hydroxy group, which is always present in the chlorosomal bacteriochlorophylls (BChl's) c, d and e. Instead, the presently studied compounds have carbonyl groups. These cannot function as hydrogen bond donating groups. However due to interspacing water molecules bound to the zinc ion, double hydrogen bonding can occur to adjacent tetrapyrrolic macrocycles equipped with carbonyl recognition groups. Solution studies comprising UV-Vis absorption, electronic circular dichroism (ECD) and FT-IR show that different aggregates are formed in hydrated solvents in comparison to dry nonpolar solvents. Single crystal X-ray studies show variable supramolecular interactions either with interspacing water molecules coordinating the Zn ion within a porphyrin or with the 17 2 carbonyl group of a chlorin ligating the Zn ion. Our findings have implications for a minimalistic design of self-assembling chromophores, which can act as efficient light-harvesting units.
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| 6. |
- Kirejev, Vladimir, 1984, et al.
(författare)
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Photophysics and ex vivo biodistribution of beta-cyclodextrin-meso-tetra(m-hydroxyphenyl)-porphyrin conjugate for biomedical applications
- 2014
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Ingår i: Photochemical & Photobiological Sciences. - : Springer Science and Business Media LLC. - 1474-905X .- 1474-9092. ; 13:8, s. 1185-1191
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Tidskriftsartikel (refereegranskat)abstract
- Low aqueous solubility of porphyrin-based photosensitizers hampers their clinical use in photodynamic therapy because of complex delivery. In this study, we explore meso-tetra(m-hydroxyphenyl)-21,23H-porphyrin (mTHPP), a potent photosensitizer, covalently attached to beta-cyclodextrin (CD-mTHPP) with a focus on topical delivery and cellular uptake. The photophysical properties of CD-mTHPP were examined using steady-state fluorescence and lifetime measurements verifying increased aqueous solubility. Confocal and fluorescence lifetime imaging microscopy on human squamous carcinoma cells (A431) evidenced a cytoplasmic uptake of CD-mTHPP in predominantly monomeric form. CD-mTHPP was also delivered to human skin ex vivo and the skin penetration was assessed using two-photon fluorescence microscopy. The results indicated that CD-mTHPP exhibits improved skin distribution compared to mTHPP alone using aqueous vehicles. Thus the CD-mTHPP conjugate demonstrates improved biodistribution ex vivo compared to mTHPP and is a promising multimodal system for photodynamic therapy.
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| 7. |
- Labet, Vanessa, et al.
(författare)
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UV-induced formation of the thymine–thymine pyrimidine (6-4) pyrimidone photoproduct – a DFT study of the oxetane intermediate ring opening.
- 2013
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Ingår i: Photochemical and Photobiological Sciences. - : Springer Science and Business Media LLC. - 1474-905X .- 1474-9092. ; 12:8, s. 1509-1516
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism by which the hypothetical oxetane/azetidine intermediate formed during the photochemical process leading to pyrimidine (6-4) pyrimidone photoproducts when DNA is submitted to UV radiation opens is investigated computationally by DFT using a 5’-TT-3’ dinucleoside monophosphate as a structural model. First, the feasibility of an intramolecular mechanism involving one proton transfer inducing opening of the oxetane ring is examined. It results in a very high Gibbs energy of activation (+166 kJ mol−1) and quite a low Gibbs energy of reaction (−35 kJ mol−1). The protonation state of the phosphate group is shown to have little effect while the bulk effect of an aqueous environment modeled by the Polarizable Continuum Model method lowers slightly the activation barrier (by about 10–20 kJ mol−1), not enough to explain the fact that the oxetane intermediate is not observed experimentally. Then the catalytic effect of water molecules on the reaction pathway is studied by including either 1 or 2 assisting water molecules in the chemical system. The resulting activation barrier is considerably lowered and in the most favorable situation – a phosphate group deprotonated and 2 assisting water molecules – the Gibbs energy activation is as low as +44 kJ mol−1 and the Gibbs energy of reaction is quite favorable: −79 kJ mol−1, suggesting that in biological systems the oxetane ring opening process proceeds with explicit intervention of water molecules from the environment.
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| 8. |
- Lindh, JD, et al.
(författare)
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Vitamin D and drug-metabolising enzymes
- 2012
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Ingår i: Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology. - : Springer Science and Business Media LLC. - 1474-9092. ; 11:12, s. 1797-1801
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Tidskriftsartikel (refereegranskat)
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| 9. |
- McKenzie, Richard L., et al.
(författare)
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Ozone depletion and climate change: Impacts on UV radiation.
- 2011
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Ingår i: Photochemical and Photobiological Sciences. - : Springer Science and Business Media LLC. - 1474-9092 .- 1474-905X. ; 10:2, s. 182-198
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Forskningsöversikt (refereegranskat)abstract
- The Montreal Protocol is working, but it will take several decades for ozone to return to 1980 levels. The atmospheric concentrations of ozone depleting substances are decreasing, and ozone column amounts are no longer decreasing. Mid-latitude ozone is expected to return to 1980 levels before mid-century, slightly earlier than predicted previously. However, the recovery rate will be slower at high latitudes. Springtime ozone depletion is expected to continue to occur at polar latitudes, especially in Antarctica, in the next few decades. Because of the success of the Protocol, increases in UV-B radiation have been small outside regions affected by the Antarctic ozone hole, and have been difficult to detect. There is a large variability in UV-B radiation due to factors other than ozone, such as clouds and aerosols. There are few long-term measurements available to confirm the increases that would have occurred as a result of ozone depletion. At mid-latitudes UV-B irradiances are currently only slightly greater than in 1980 (increases less than ~5%), but increases have been substantial at high and polar latitudes where ozone depletion has been larger. Without the Montreal Protocol, peak values of sunburning UV radiation could have been tripled by 2065 at mid-northern latitudes. This would have had serious consequences for the environment and for human health. There are strong interactions between ozone depletion and changes in climate induced by increasing greenhouse gases (GHGs). Ozone depletion affects climate, and climate change affects ozone. The successful implementation of the Montreal Protocol has had a marked effect on climate change. The calculated reduction in radiative forcing due to the phase-out of chlorofluorocarbons (CFCs) far exceeds that from the measures taken under the Kyoto protocol for the reduction of GHGs. Thus the phase-out of CFCs is currently tending to counteract the increases in surface temperature due to increased GHGs. The amount of stratospheric ozone can also be affected by the increases in the concentration of GHGs, which lead to decreased temperatures in the stratosphere and accelerated circulation patterns. These changes tend to decrease total ozone in the tropics and increase total ozone at mid and high latitudes. Changes in circulation induced by changes in ozone can also affect patterns of surface wind and rainfall. The projected changes in ozone and clouds may lead to large decreases in UV at high latitudes, where UV is already low; and to small increases at low latitudes, where it is already high. This could have important implications for health and ecosystems. Compared to 1980, UV-B irradiance towards the end of the 21st century is projected to be lower at mid to high latitudes by between 5 and 20% respectively, and higher by 2–3% in the low latitudes. However, these projections must be treated with caution because they also depend strongly on changes in cloud cover, air pollutants, and aerosols, all of which are influenced by climate change, and their future is uncertain. Strong interactions between ozone depletion and climate change and uncertainties in the measurements and models limit our confidence in predicting the future UV radiation. It is therefore important to improve our understanding of the processes involved, and to continue monitoring ozone and surface UV spectral irradiances both from the surface and from satellites so we can respond to unexpected changes in the future.
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| 10. |
- Norval, Mary, et al.
(författare)
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Is the action spectrum for the UV-induced production of previtamin D3 in human skin correct?
- 2010
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Ingår i: Photochemical and Photobiological Sciences. - : Springer Science and Business Media LLC. - 1474-9092 .- 1474-905X. ; 9:1, s. 11-17
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Tidskriftsartikel (refereegranskat)abstract
- The universally recognised action spectrum for the UV-induced conversion of 7-dehydrocholesterol to previtamin D3 in human skin was published in 1982, and indicates a maximum at about 297 nm with essentially no production above 315 nm. This work represents a milestone in research on vitamin D, but limitations in the original data should be recognised. Various findings have arisen in recent years which cast doubts on the accuracy of the action spectrum and its application for spectral weighting in calculations of effective UV doses. In conclusion, the construction of an entirely new computational model to predict previtamin D levels is recommended.
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