bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intramolecular Quenching of Tryptophan Phosphorescence in Short Peptides and Proteins¶
Authors: Gonnelli Margherita , Strambini Giovanni B. 
Published: July 2010

ABSTRACTThe phosphorescence lifetime (τ) of tryptophan (Trp) residues in proteins in aqueous solutions at ambient temperature can vary several orders of magnitude depending on the flexibility of the local structure and the rate of intramolecular quenching reactions. For a more quantitative interpretation of τ in terms of the local protein structure, knowledge of all potential quenching moieties in proteins and of their reaction rates is required. The quenching effectiveness of each amino acid (X) side chain and of the peptide backbone was investigated by monitoring their intramolecular quenching rate (kobs) in tripeptides of the form acetyl‐Trp‐Gly‐X‐CONH2 (WGX), where Trp is joined to × by a flexible Gly link. The results indicate that among the various groups present in proteins only the side chains of Cys, His, Tyr and Phe are able to quench Trp phosphorescence at a detectable rate (kobs > 40 s−1), with the quenching effectiveness for rotationally unrestricted side chains ranking in the order Cys >> His+ > Tyr >> Phe ∼ His. For the aromatic side chains the corresponding contact rate at 20°C is estimated to be between 3‐4 × 109 s−1 for Cys (as determined by Lapidus et al.), 0.8‐8 × 106 s−1 for His+, 0.37‐3.7 × 106 s−1 for Tyr and 0.2‐2 × 105 s−1 for Phe and His. In the cases of His and Tyr, kobs drops sharply with increasing pH, with midpoint transitions about 1 pH unit above the pKa, indicating that quenching is almost exclusive to the protonated form. From the temperature dependence of the rate, obtained in 50/50 propylene glycol/water between −20°C and 20°C, the reaction is characterized by activation energies of about 5 kcal·M−1 for His+ and Tyr and 8 kcal ·M−1 for Phe. An analysis of the groups in contact with Trp residues in proteins that exhibit long phosphorescence lifetimes at ambient temperature leads to the conclusion that the contact rate of the peptide group and of the remaining side chains is lower than 0.1 s−1, showing that these moieties are practically inert with respect to the triplet‐state lifetime. It shows further that the immobilization of the aromatic side chains within the globular fold cuts their quenching effectiveness drastically to contact rates < 2 s−1, a phenomenon attributed to the low probability of forming a stacked exciplex with the indole ring. All evidence suggests that, except in the case of nearby Cys or Trp residues, whose interaction with the triplet state reaches beyond van der Waals contact, the emission of buried Trp residues is unlikely to be quenched by surrounding protein groups.
Sun Exposure and Sun Protection Habits Among High‐school Adolescents in Porto Alegre, Brazil¶
Authors: Benvenuto‐Andrade Cristiane , Zen Barbara , Fonseca Gisele , De Villa Damiê , Cestari Tania 
Published: July 2010

ABSTRACTAdolescents constitute an important audience for photoprotection programs. Sun exposure and sun protection habits acquired during adolescence have a significant impact on skin cancer incidence. We administered a questionnaire to 724 students about ultraviolet radiation effects, opinions about tanning, total time of sun exposure per day, photoprotection and activities in the sun. About 90% were aware of the association between sun exposure and skin cancer, and mass media was the main source of information. However, the great majority believed that tanning improved their appearance, and that it was worth taking the risk. The most prevalent outdoor activity among boys was sports; girls preferred walks and sunbathing. Sun exposure was significantly longer in summer, when 90% of the students went to the beach. About 47% reported sunscreen use in summer and only 3% reported using sunscreen during winter. These results emphasize the need for the promotion of photoprotective habits in our population and the importance of engaging physicians and schoolteachers in developing campaigns directed at this issue to achieve effective, long‐lasting results. Adolescents are aware of the effects of ultraviolet radiation on the skin but campaigns have not successfully changed their sun exposure habits.
The UV Index on the Spanish Mediterranean Coast¶
Authors: Marín M. J. , Sola Y. , Tena F. , Utrillas M. P. , Campmany E. , de Cabo X. , Lorente J. , Martínez‐Lozano J. A. 
Published: July 2010

ABSTRACTAn analysis is made of measured ultraviolet erythemal solar radiation (UVER) data recorded during the year 2003 by the networks of the Catalan Weather Service and the Environment Department of Valencia (both on the Spanish Mediterranean coast). Results show a latitudinal variation at sea level, of 3‐4% per degree and an increase with altitude of 10% per km. Based on these data the UV Index has been evaluated for the measuring stations. The maximum experimental value of the UV Index was around 9 during the summer, although higher values were recorded at two stations, one at the highest elevation and the other at the lowest latitude. The annual accumulated doses of irradiation on a horizontal plane have been presented as well as the evolution through the year in units of energy, Standard Erythemal Doses and Minimum Erythemal Doses according to different phototypes. Lastly, the UV Index forecast, determined with a multiple scattering radiative transfer model, has been analyzed. Total agreement or only one unit of difference between measured and modelled values was found in 94% of cloud‐free cases.
Different Susceptibility of Cells of Porcine Skin and Internal Organs to Ultraviolet A‐Induced Breaking of Nuclear DNA¶
Authors: Brożyna Anna , Chwirot Barbara W. 
Published: July 2010

ABSTRACTThere is a continuously growing interest in medical applications of ultraviolet radiation (UV‐A and long‐wavelength UV‐B) especially for laser surgery, phototherapy and photodiagnostics of human internal organs. UV‐B and UV‐A radiation is potentially mutagenic, however, there has been very little information published to date concerning the significance of possible deleterious action of such photons on cells of internal tissues. The aim of this study is to compare the sensitivities of skin cells to those of internal organs upon exposure to UV‐A. To assess this sensitivity we have determined the UV‐A dose‐dependent frequency of nuclear DNA breaks detected with the terminal deoxynucleotidyl transferase‐mediated deoxyuridine triphosphate‐biotin nick end‐labeling (TUNEL) technique. The materials for the study were macroscopic samples of porcine skin, colon and esophagus. The UV‐A dose ranged from 0.1 to 1000 mJ/cm2, which is similar to doses received by cells in regions examined with laser‐induced fluorescence or by cells surrounding areas subject to a laser ablation. To reduce the influence of DNA repair processes the tissue samples were kept at a low temperature during the irradiation and were deep frozen immediately after completing the irradiation procedure. The cells of the internal organs are much more susceptible to UV‐A‐induced breaking of DNA than the skin cells. The percentage fractions and the spatial distributions of the damaged cells and the characteristics of the UV‐A dose dependence seem to vary by type of internal organ.
Fluorescence Properties of Fluorescein, Tetramethylrhodamine and Texas Red Linked to a DNA Aptamer¶
Authors: Unruh Jay R. , Gokulrangan Giridharan , Wilson George S. , Johnson Carey K. 
Published: July 2010

ABSTRACTWe report the picosecond time‐scale fluorescence dynamics of a dye‐labeled DNA oligonucleotide or “aptamer” designed to bind specifically to Immunoglobulin E. Comparison of the photophysics of Texas Red (TR), fluorescein and 5′‐carboxytetramethylrhodamine (TAMRA)‐labeled aptamers reveals surprising differences with significant implications for measurements of oligonucleotide structure and dynamics. The fluorescence decay of the TR‐aptamer is a simple single exponential with a weak temperature dependence. The fluorescence decay of the fluorescein‐aptamer (fl‐aptamer) is pH dependent and displays a complex temperature dependence with significant changes on melting of the aptamer tertiary structure. Despite its similarities to TR, TAMRA is strongly quenched when conjugated to the aptamer and displays complex fluorescence kinetics best described by a distributed rate model. Using the maximum entropy method, we have discovered two highly temperature‐dependent fluorescence lifetimes for the TAMRA‐aptamer. One of these lifetimes is similar to that of free TAMRA and displays the same temperature dependence. The other lifetime is quenched and displays a temperature dependence characteristic of a charge transfer reaction. These data set TR apart as an attractive alternative to TAMRA and fluorescein for studies such as fluorescence polarization and fluorescence resonance energy transfer, where environmental sensitivity of the probe is not desired.
Characterization of Photoproducts of m‐THPP in Aqueous Solution¶
Authors: Lourette Natacha , Maunlt Benoît , Bezdetnaya Lina , Lassalle Henri‐Pierre , Guillemin Françols , Muller Jean‐François 
Published: July 2010

ABSTRACTThis study examined the nature of photoproducts after pulse laser irradiation (647.5 nm) of 5,10,15,20‐tetrakis(meso‐hydroxyphenyl)porphyrin (m‐THPP) (10 μmol/L) in ethanol‐water (1/99, vol/vol) solution. Spectroscopic measurements (UV‐visible absorption and fluorescence) and mass spectrometry techniques (matrix‐assisted laser desorption‐ionization [MALDI] coupled with time‐of‐flight mass spectrometer [TOF‐MS] or tandem time of flight mass spectrometer [TOF/TOF‐MS]) were used to follow photomodifications. Spectroscopic measurements evidenced photomodification as the main process after m‐THPP irradiation. Three oxidized photoproducts at m/z 693.25, 695.24 and 713.25 were characterized by MS. After prolonged irradiation new isotopic distributions were registered at m/z 1355.41, 2031.57, 2707.80 and 3383.98 with MALDI‐TOF‐MS and TOF/TOF‐MS. These new photoproducts were attributed to covalent oligomeric structures as dimer, trimer, tetramer and pentamer of m‐THPP.
Applications of Free‐Electron Lasers in the Biological and Material Sciences¶
Authors: Edwards G. S. , Allen S. J. , Haglund R. F. , Nemanich R. J. , Redlich B. , Simon J. D. , Yang W.‐C. 
Published: July 2010

ABSTRACTFree‐Electron Lasers (FELs) collectively operate from the terahertz through the ultraviolet range and via intracavity Compton backscattering into the X‐ray and gamma‐ray regimes. FELs are continuously tunable and can provide optical powers, pulse structures and polarizations that are not matched by conventional lasers. Representative research in the biological and biomedical sciences and condensed matter and material research are described to illustrate the breadth and impact of FEL applications. These include terahertz dynamics in materials far from equilibrium, infrared nonlinear vibrational spectroscopy to investigate dynamical processes in condensed‐phase systems, infrared resonant‐enhanced multiphoton ionization for gas‐phase spectroscopy and spectrometry, infrared matrix‐assisted laser‐desorption‐ionization and infrared matrix‐assisted pulsed laser evaporation for analysis and processing of organic materials, human neurosurgery and ophthalmic surgery using a medical infrared FEL and ultraviolet photoemission electron microscopy for nanoscale characterization of materials and nanoscale phenomena. The ongoing development of ultraviolet and X‐ray FELs are discussed in terms of future opportunities for applications research.
Vacuum‐ultraviolet Photochemically Initiated Modification of Polystyrene Surfaces: Chemical Changes¶,‡
Authors: López‐Gejo Juan , Gliemann Hartmut , Schimmel Thomas , Braun André M. 
Published: July 2010

ABSTRACTFourier‐Transform infrared (FTIR) spectroscopy and surface energy analysis (contact angle measurements) have been performed as a means of identification and quantification of the functionalization of polystyrene surfaces upon vacuum ultraviolet‐ (VUV‐) photochemically initiated oxidation. Photochemical oxidation was performed in the presence of water vapor and molecular oxygen using a pulsed Xe2‐excimer radiation source (λexc: 172 nm). Surface oxidation was studied as a function of two parameters: irradiation time and distance between sample and radiation source. During the first 1–2 min of irradiation, an increase of the concentrations of hydroxyl (OH) and carbonyl (C=O) groups on the surface was observed, both reaching limiting values. As expected, the rate of oxidation diminished exponentially with increasing distance between the radiation source and the surface of the polystyrene film. Changes in the surface energy due to the introduction of these polar (i.e. OH and C=O) groups were also determined. The densities of the functional groups decreased upon washing with acetonitrile, and analysis of the washing solution by means of gas chromatography‐mass spectrometry (GC‐MS) revealed the presence of a large number of products. The application of pulsed Xe2‐excimer radiation sources as a valuable alternative to conventional means (i.e. laser and plasma) for the photochemical oxidation and surface modification of polystyrene is discussed.
An Improved Outdoor Calibration Procedure for Broadband Ultraviolet Radiometers¶
Authors: Cancillo M. L. , Serrano A. , Antón M. , García J. A. , Vilaplana J. M. , de la Morena B. 
Published: July 2010

ABSTRACTThis article aims at improving the broadband ultraviolet radiometer's calibration methodology. For this goal, three broadband radiometers are calibrated against a spectrophotometer of reference. Three different one‐step calibration models are tested: ratio, first order and second order. The latter is proposed in order to adequately reproduce the high dependence on the solar zenith angle shown by the other two models and, therefore, to improve the calibration performance at high solar elevations. The proposed new second‐order model requires no additional information and, thus, keeps the operational character of the one‐step methodology. The models are compared in terms of their root mean square error and the most qualified is subsequently validated by comparing its predictions with the spectrophotometer measurements within an independent validation data subset. Results show that the best calibration is achieved by the second‐order model, with a mean bias error and mean absolute bias error lower than 2.2 and 6.7%, respectively.
Topical Application of a Novel, Water‐soluble γ‐Tocopherol Derivative Prevents UV‐induced Skin Damage in Mice¶
Authors: Yasuoka Shingo , Takata Jiro , Karube Yoshiharu , Katoh Eiko , Tsuzuki Toshi , Kizu Junko , Tsuchiya Masao , Kobayashi Shizuko 
Published: July 2010

ABSTRACTWe investigated whether the topical application of a novel, water‐soluble γ‐tocopherol (γ‐Toc) derivative, γ‐tocopherol‐N,N‐dimethylglycinate hydrochloride (γ‐TDMG), could protect against UV‐induced skin damage in hairless mice. Topical pre‐or post‐application of a 5% (93 mM) γ‐TDMG solution in water/propylene glycol/ethanol (2:1:2) significantly prevented sunburn cell formation, lipid peroxidation and edema/inflammation that were induced by exposure to a single dose of UV irradiation of 5 kJ/m2(290–380 nm, maximum 312 nm). This effect was greater than that seen with two α‐Toc derivatives, α‐tocopherol acetate (α‐TA) and α‐tocopherol‐N,N‐dimethylglycinate (α‐TDMG). When a 5% solution of γ‐TDMG was applied to mouse skin for 1 h, cutaneous γ‐Toc increased by 25‐fold after 24 h; levels of cutaneous α‐Toc increased by only two‐and eight‐fold in α‐TDMG and α‐TA treated skins, respectively. These findings indicated that γ‐TDMG immediately converted to γ‐Toc in the skin and suggest that ability of γ‐TDMG to protect the skin from the damaging effects of irradiation was due to its conversion to γ‐Toc. When a 5% solution of γ‐Toc was applied to mouse skin for 1 h, cutaneous γ‐Toc rapidly increased by 25‐fold, but fell to baseline levels by 24 h. In contrast, the concentration of γ‐Toc in skin that was treated with γ‐TDMG similarly increased, but these high levels were maintained after 24 h. These results suggest that γ‐TDMG may be a more effective source of γ‐Toc in skin. Thus, the topical application of γ‐TDMG may be efficacious for the prevention of UV‐B‐induced skin damage.
Synthesis of Hydroxy and Methoxy Perylene Quinones, Their Spectroscopic and Computational Characterization, and Their Antiviral Activity¶
Authors: Krishnamoorthy G. , Webb S. P. , Nguyen T. , Chowdhury P. K. , Halder M. , Wills N. J. , Carpenter S. , Kraus G. A. , Gordon M. S. , Petrich J. W. 
Published: July 2010

ABSTRACTHydroxy and methoxy perylene quinones are synthesized in an attempt to isolate the essential spectroscopic and biological features of light‐induced antiviral agents such as hypericin and hypocrellin. Unlike their naturally occurring counterparts, these synthetic quinones bear the carbonyl, hydroxyl, and methoxy groups in the “bay region.” The hydroxy and methoxy compounds have rich absorption spectra with broad features in the visible (∼450–800 nm) and relatively more intense and narrow features at wavelengths ≤350 nm. High‐levelab initioquantum mechanical calculations assign the features in the absorption spectra to electronic transitions from Soto S2and to higher‐lying electronic states. The calculations indicate that in the ground state the trans dihydroxy isomer is 12.5 kcal/mol lower in energy than the cis dihydroxy isomer and is thus the only species present. The lowest‐energy trans methoxy ground state isomer and the lowest‐energy cis methoxy ground state isomer are found to be degenerate. An additional cis methoxy isomer 6.3 kcal/mol higher in energy than the global minimum is assumed to contribute to the spectrum and is also considered. Finally, the synthetic compounds exhibit similar light‐induced antiviral activity to each other, but significantly less than that of hypericin.
Ultraviolet‐B Radiation Upregulates Expression of Dectin‐2 on Epidermal Langerhans Cells by Activating the Gene Promoter¶
Authors: Bonkobara Makoto , Yagihara Hiroko , Yudate Tatsuo , Chung Jin‐Sung , Washizu Tsukimi , Ariizumi Kiyoshi , Cruz Ponciano D. 
Published: July 2010

ABSTRACTEpidermal Langerhans cells (LC) belong to the antigen‐presenting cell (APC) family of dendritic cells that can initiate antigen‐specific immunogenic or tolerogenic responses. In mice, we have shown ultraviolet‐B (UV‐B) irradiation to induce long‐lasting suppression (tolerance) of contact hyper‐sensitivity responses by converting LC from immunogenic to tolerogenic APC. The C‐type lectin receptor, dectin‐2, expressed preferentially by LC and dendritic cells, has also been shown to be involved in inducing this form of UV‐B‐induced immunosuppression. These observations led us to question whether UV‐B can modulate dectin‐2 expression by LC. In ICR mice engineered to express the dectin‐2 gene promoter linked to a luciferase reporter gene, we found broadband UV‐B treatment in vivo to activate the promoter in LC. In wild‐type C3H/HeN mice, we found such treatment in vivo to yield LC with increased dectin‐2 expression at both mRNA and protein levels. Broadband UV‐B treatment in vitro of bone marrow‐derived dendritic cells from these mice also showed upregulated expression of dectin‐2 mRNA. These findings lead us to conclude that broadband UV‐B upregulates dectin‐2 expression in LC by activating the dectin‐2 gene promoter. Such amplification suggests that UV‐B‐induced immunosuppression may be due (at least in part) to augmented dectin‐2 expression in LC.
The Contribution of Calpains in the Down‐regulation of Mdm2 and p53 Proteolysis in Reconstructed Human Epidermis in Response to Solar Irradiation¶
Authors: Gélis Christelle , Mavon Alain , Vicendo Patricia 
Published: July 2010

ABSTRACTThe p53 protein accumulates in human skin cells in vitro and in vivo when UV‐irradiated. The transient stability of p53 requires a decrease in the activity of the ubiquitin ligase murine double minute 2 (Mdm2). Solar light irradiation (52.5, 105 and 405 mJ/cm2) of reconstructed human epidermis caused cutaneous damage. Specifically, UV‐B induced the formation of sunburn cells and at first, an increase in the accumulation of p53 protein. Unexpectedly, 24 h after irradiation, a specific proteolytic cleavage of p53 resulted in the formation of a 40 kDa fragment. Both the accumulation of p53 and the proteolytic cleavage increased, commensurate with the UV dose. In contrast to p53, the level of expression of Mdm2 decreased drastically with the UV dose. It is important to note that calpastatin (20 μM), a specific inhibitor of calpains, decreased the formation of sunburn cells, inhibited the cleavage of p53 and induced an accumulation of Mdm2. The apoptotic process is strongly repressed. This demonstrates for the first time that calpains can participate in the downregulation of Mdm2 in the epidermis very rapidly after UV irradiation, and that they contribute to a specific cleavage of p53 protein. All of these processes may be involved in the apoptotic response of the skin to UV stimulation.
Photoreactivation in Paramecium tetraurelia under Conditions of Various Degrees of Ozone Layer Depletion¶
Authors: Takahashi Akihisa , Kumatani Toshihiro , Usui Saori , Tsujimura Ryoko , Seki Takaharu , Morimoto Kouichi , Ohnishi Takeo 
Published: July 2010

ABSTRACTPhotoreactivation (PR) is an efficient survival mechanism that helps protect cells against the harmful effects of solar‐ultraviolet (UV) radiation. The PR mechanism involves photolyase, just one enzyme, and can repair DNA damage, such as cyclobutane‐pyrimidine dimers (CPD) induced by near‐UV/blue light, a component of sunlight. Although the balance of near‐UV/blue light and far‐UV light reaching the Earth's surface could be altered by the atmospheric ozone layer's depletion, experiments simulating this environmental change and its possible effects on life have not yet been performed. To quantify the strength of UVB in sunlight reaching the Earth's surface, we measured the number of CPD generated in plasmid DNA after UVB irradiation or exposure to sunlight. To simulate the increase of solar‐UV radiation resulting from the ozone layer depletion, Paramecium tetraurelia was exposed to UVB and/or sunlight in clear summer weather. PR recovery after exposure to sunlight was complete at a low dose rate of 0.2 J/m2·s, but was less efficient when the dose rate was increased by a factor of 2.5 to 0.5 J/m2·s. It is suggested that solar‐UV radiation would not influence the cell growth of P. tetraurelia for the reason of high PR activity even when the ozone concentration was decreased 30% from the present levels.
Enzyme‐assisted Reforming of Glucose to Hydrogen in a Photoelectrochemical Cell¶
Authors: Hambourger Michael , Brune Alicia , Gust Devens , Moore Ana L. , Moore Thomas A. 
Published: July 2010

ABSTRACTHydrogen gas has been produced by reforming glucose in a hybrid photoelectrochemical cell that couples a dye‐sensitized nanoparticulate wide band gap semiconductor photoanode to the enzyme‐based oxidation of glucose. A layer of porphyrin sensitizer is adsorbed to a TiO2 nanoparticulate aggregate sintered to a conducting glass substrate to form the photoanode. Excitation of the porphyrin results in electron injection into the TiO2, and migration to a microporous platinum cathode where hydrogen is produced by hydrogen ion reduction. The oxidized sensitizer dye is reduced by NADH, regenerating the dye and poising the NAD+/NADH redox couple oxidizing. The NAD+ is recycled to NADH by the enzyme glucose dehydrogenase, which obtains the necessary electrons from oxidation of glucose. The reforming of glucose produces gluconolactone, which hydrolyzes to gluconate; the electrochemical potential necessary to overcome thermodynamic and kinetic barriers to hydrogen production by NADH is provided by light. The quantum yield of hydrogen is ∼2.5%.