bluuebunny/crossref_metadata_2025 huggingface dataset:
Intramolecular Quenching of Tryptophan Phosphorescence in Short Peptides and Proteins¶
Authors: Gonnelli Margherita , Strambini Giovanni B.
Published: July 2010

The 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

Adolescents 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

An 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

There 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

We 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

This 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

Free‐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

Fourier‐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

This 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

We 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

Hydroxy 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

Epidermal 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

The 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

Photoreactivation (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

Hydrogen 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%.
Prevention of Ultraviolet‐B Radiation Damage by Resveratrol in Mouse Skin Is Mediated via Modulation in Survivin¶
Authors: Aziz Moammir Hasan , Afaq Farrukh , Ahmad Nihal
Published: July 2010

Nonmelanoma skin cancer is the most frequently diagnosed malignancy in the United States, and multiple exposures to solar ultraviolet (UV) radiation (particularly its UV‐B component, 290–320 nm) is its major cause. “Chemoprevention”by naturally occurring agents is being appreciated as a newer dimension in the management of neoplasia including skin cancer. We recently demonstrated that resveratrol (trans‐3,5,4‐trihydroxystilbene), an antioxidant found in grapes, red wines and a variety of nuts and berries, imparts protection from acute UV‐B–mediated cutaneous damages in SKH‐1 hairless mice. Understanding the mechanism of resveratrol‐mediated protection of UV responses is important. We earlier demonstrated that resveratrol imparts chemopreventive effects against multiple UV‐exposure–mediated modulations in (1) cki‐cyclin‐cdk network and (2) mitogen activated protein kinase (MAPK)‐pathway. This study was conducted to assess the involvement of inhibitor of apoptosis protein family protein Survivin during resveratrol‐mediated protection from multiple exposures of UV‐B (180 mJ/cm2; on alternate days; for a total of seven exposures) radiations in the SKH‐1 hairless mouse skin. Our data demonstrated that topical pretreatment of resveratrol (10 μmol in 200 μL acetone/mouse) resulted in significant inhibition of UV‐B exposure‐mediated increases in (1) cellular proliferations (Ki‐67 immunostaining), (2) protein levels of epidermal cyclooxygenase‐2 and ornithine decarboxylase, established markers of tumor promotion, (3) protein and messenger RNA levels of Survivin, and (4) phosphorylation of survivin in the skin of SKH‐1 hairless mouse. Resveratrol pretreatment also resulted in (1) reversal of UV‐B–mediated decrease of Smac/DIABLO and (2) enhancement of UV‐B–mediated induction of apoptosis, in mouse skin. Taken together, our study suggested that resveratrol imparts chemopreventive effects against UV‐B exposure–mediated damages in SKH‐1 hairless mouse skin via inhibiting Survivin and the associated events.
Protective Effect of the Isoflavonoid Equol Against Hairless Mouse Skin Carcinogenesis Induced by UV Radiation Alone or with a Chemical Cocarcinogen¶
Authors: Widyarini Sitarina , Husband Alan J. , Reeve Vivienne E.
Published: July 2010

Isoflavones derived from many edible plants, such as genistein from the soybean, have well‐documented antioxidant and estrogenic activity but may also be anticarcinogenic. In this study, we examined the potential of the isoflavone equol [(S)‐4′,7‐dihydroxyisoflavane] to protect from skin carcinogenesis in the hairless mouse. Daily topical applications of equol lotions significantly protected against skin carcinogenesis induced by chronic exposure to solar‐simulated UV radiation (SSUV) or by topical treatment with the chemical carcinogen 7,12‐dimethylbenz(a)anthracene (DMBA) or by the combined cocarcinogenic treatment of DMBA followed by chronic SSUV. Monitoring of tumor development for 40 weeks showed significantly delayed tumor appearance and reduced tumor multiplicity in all equol‐treated groups. In mice treated with either SSUV or DMBA + SSUV, equol significantly reduced the proportion of tumors progressing from benign papillomas to malignant squamous cell carcinoma (SCC) by 33–58% and reduced the average diameter of SCC by 71–82%. In a short‐term study, equol dose dependently inhibited the SSUV induction of the tumor promotion biomarker enzyme, ornithine decarboxylase, in the skin, suggesting the anticarcinogenic activity of equol may be attributed to its inhibition of the tumor promotion phase of carcinogenesis.
Pomegranate Fruit Extract Modulates UV‐B–mediated Phosphorylation of Mitogen‐activated Protein Kinases and Activation of Nuclear Factor Kappa B in Normal Human Epidermal Keratinocytes¶
Authors: Afaq Farrukh , Malik Arshi , Syed Deeba , Maes Daniel , Matsui Mary S. , Mukhtar Hasan
Published: July 2010

Excessive exposure of solar ultraviolet (UV) radiation, particularly its UV‐B component, to humans causes many adverse effects that include erythema, hyperplasia, hyperpigmentation, immunosuppression, photoaging and skin cancer. In recent years, there is increasing use of botanical agents in skin care products. Pomegranate derived from the tree Punica granatum contains anthocyanins (such as delphinidin, cyanidin and pelargonidin) and hydrolyzable tannins (such as punicalin, pedunculagin, punicalagin, gallagic and ellagic acid esters of glucose) and possesses strong antioxidant and anti‐inflammatory properties. Recently, we have shown that pomegranate fruit extract (PFE) possesses antitumor promoting effects in a mouse model of chemical carcinogenesis. To begin to establish the effect of PFE for humans in this study, we determined its effect on UV‐B–induced adverse effects in normal human epidermal keratinocytes (NHEK). We first assessed the effect of PFE on UV‐B–mediated phosphorylation of mitogen‐activated protein kinases (MAPK) pathway in NHEK. Immunoblot analysis demonstrated that the treatment of NHEK with PFE (10–40 μg/mL) for 24 h before UV‐B (40 mJ/cm2) exposure dose dependently inhibited UV‐B–mediated phosphorylation of ERK1/2, JNK1/2 and p38 protein. We also observed that PFE (20 μg/mL) inhibited UV‐B–mediated phosphorylation of MAPK in a time‐dependent manner. Furthermore, in dose‐and time‐dependent studies, we evaluated the effect of PFE on UV‐B–mediated activation of nuclear factor kappa B (NF‐κB) pathway. Using Western blot analysis, we found that PFE treatment of NHEK resulted in a dose‐ and time‐dependent inhibition of UV‐B–mediated degradation and phosphorylation of IκBα and activation of IKKα. Using immunoblot analysis, enzyme‐linked immunosorbent assay and electrophoretic mobility shift assay, we found that PFE treatment to NHEK resulted in a dose‐ and time‐dependent inhibition of UV‐B–mediated nuclear translocation and phosphorylation of NF‐κB/p65 at Ser536. Taken together, our data shows that PFE protects against the adverse effects of UV‐B radiation by inhibiting UV‐B–induced modulations of NF‐κB and MAPK pathways and provides a molecular basis for the photochemopreventive effects of PFE.
Phioxine B Phototoxicity: A Mechanistic Study Using HaCaT Keratinocytes¶
Authors: Inbaraj Johnson J. , Kukielczak Barbara M. , Chignell Colin F.
Published: July 2010

Phloxine B (PhB) (2′,4′,5′,7′‐tetrabromo‐4,5,6,7‐tetrachloro‐fluorescein; D&C Red No. 28) is a red dye found in drugs, cosmetics and foods; it is also currently being evaluated as a phototoxin for the potential control of fruit flies. Previous studies have shown that PhB is an efficient photosensitizer of damage to cellular membranes; thus, exposure of the skin to the dye and sunlight or artificial light may result in phototoxicity. Therefore, we have studied the phototoxicity of PhB and its structural analogue 2′,7′‐dichlorofluorescein (DCF) to HaCaT keratinocytes. Anaerobic visible irradiation (>400 nm) of PhB generated a semiquinone type radical, as detected by direct electron paramagnetic resonance. Aerobic visible irradiation of a reaction mixture containing PhB, the spin trap 5,5‐di methyl‐1‐pyrroline N‐oxide (DMPO) and nicotinamide adenine dinucleotide (reduced) generated a superoxide dismutase–sensitive DMPO/O2•− adduct. Irradiation of PhB and DCF in D2O generated singlet oxygen with quantum yields of 0.59 and 0.06, respectively. PhB was much more phototoxic than DCF when cell viability was measured using the 3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxyphenyl)‐2‐(4‐sulfophenyl)‐2H‐tetrazolium assay. Visible irradiation of HaCaT keratinocytes in the presence of PhB (5 μM) resulted in a 90% decrease in cell viability. 3β‐Hydroxy‐5α‐cholest‐6‐ene‐5‐hydroperoxide, a singlet oxygen photoproduct of cholesterol, was isolated from HaCaT keratinocytes irradiated in the presence of PhB. Furthermore, PhB phototoxicity was inhibited by histidine and cysteine, quenchers of singlet oxygen. PhB (0.5 μM) and light irradiation also resulted in DNA damage, as measured by the Comet assay. The phototoxicity mechanism of PhB most probably initially involves a Type‐II reaction with free radicals playing a minor role. However, secondary oxidative species such as radicals generated as a result of lipid peroxidation may serve to further promote oxidative damage. Our findings suggest that concern is warranted about the use of this dye in cosmetic products, as a food additive and in insecticidal sprays.
Optical Properties of Human Prostate at 732 nm Measured In Vivo During Motexafin Lutetium–mediated Photodynamic Therapy¶
Authors: Zhu Timothy C. , Dimofte Andreea , Finlay Jarod C. , Stripp Diana , Busch Theresa , Miles Jeremy , Whittington Richard , Malkowicz S. Bruce , Tochner Zellg , Glatstein Eli , Hahn Stephen M.
Published: July 2010

Characterization of the tissue light penetration in prostate photodynamic therapy (PDT) is important to plan the arrangement and weighting of light sources so that sufficient light fluence is delivered to the treatment volume. The optical properties (absorption [μa], transport scattering [μ′s] and effective attenuation [μeff] coefficients) of 13 patients with locally recurrent prostate cancer were measured in situ using interstitial isotropic detectors. Measurements were made at 732 nm before and after motexafin lutetium (MLu)–mediated PDT in four quadrants. Optical properties were derived by applying the diffusion theory to the fluence rates measured at several distances (0.5–5 cm) from a point source. μa and μ′s varied between 0.07 and 1.62 cm−1 (mean 0.37 ± 0.24 cm−1) and 1.1 and 44 cm−1 (mean 14 ± 11 cm−1), respectively. μa was proportional to the concentration of MLu measured by an ex vivo fluorescence assay. We have observed, on average, a reduction of the MLu concentration after PDT, presumably due to the PDT consumption of MLu. μeff varied between 0.91 and 6.7 cm−1 (mean 2.9 ± 0.7 cm−1), corresponding to an optical penetration depth (δ= 1/μeff) of 0.1–1.1 cm (mean 0.4 ± 0.1 cm). The mean penetration depth at 732 nm in human prostate is at least two times smaller than that found in normal canine prostates, which can be explained by a four times increase of the mean value of μ′s in human prostates. The mean light fluence rate per unit source strength at 0.5 cm from a point source was 1.5 ± 1.1 cm−2, excluding situations when bleeding occurs. The total number of measurements was N= 121 for all mean quantities listed above. This study showed significant inter‐ and intraprostatic differences in the optical properties, suggesting that a real‐time dosimetry measurement and feedback system for monitoring light fluences during treatment should be considered for future PDT studies.
Endogenous Fluorescence Spectroscopy of Cell Suspensions for Chemopreventive Drug Monitoring¶
Authors: Kirkpatrick Nathaniel D. , Zou Changping , Brewer Molly A. , Brands William R. , Drezek Rebekah A. , Utzinger Urs
Published: July 2010

Cancer chemopreventive agents such asN‐4‐(hydroxyphenyl)‐retinamide (4HPR) are thought to prevent cancers by suppressing growth or inducing apoptosis in precancerous cells. Mechanisms by which these drugs affect cells are often not known, and the means to monitor their effects is not available. In this study endogenous fluorescence spectroscopy was used to measure metabolic changes in response to treatment with 4HPR in ovarian and bladder cancer cell lines. Fluorescence signals consistent with nicotinamide adenine dinucleotide (NADH), flavin adenine dinucleotide (FAD) and tryptophan were measured to monitor cellular activity through redox status and protein content. Cells were treated with varying concentrations of 4HPR and measured in a stable environment with a sensitive fluorescence spectrometer. Results suggest that redox signal of all cells changed in a similar dose‐dependant manner but started at different baseline levels. Redox signal changes depended primarily on changes consistent with NADH fluorescence, whereas the FAD fluorescence remained relatively constant. Similarly, tryptophan fluorescence decreased with increased drug treatment, suggesting a decrease in protein production. Given that each cell line has been shown to have a different apoptotic response to 4HPR, fluorescence redox values along with changes in tryptophan fluorescence may be a response as well as an endpoint marker for chemopreventive drugs.
Global Forecast Model to Predict the Daily Dose of the Solar Erythemally Effective UV Radiation¶
Authors: Schmalwieser Alois W. , Schauberger Günther , Janouch Michal , Nunez Manuel , Koskela Tapani , Berger Daniel , Karamanian Gabriel
Published: July 2010

A worldwide forecast of the erythemally effective ultraviolet (UV) radiation is presented. The forecast was established to inform the public about the expected amount of erythemally effective UV radiation for the next day. Besides the irradiance, the daily dose is forecasted to enable people to choose the appropriate sun protection tools. Following the UV Index as the measure of global erythemally effective irradiance, the daily dose is expressed in units of UV Index hours. In this study, we have validated the model and the forecast against measurements from broadband UV radiometers of the Robertson–Berger type. The measurements were made at four continents ranging from the northern polar circle (67.4°N) to the Antarctic coast (61.1°S). As additional quality criteria the frequency of underestimation was taken into account because the forecast is a tool of radiation protection and made to avoid overexposure. A value closer than one minimal erythemal dose for the most sensitive skin type 1 to the observed value was counted as hit and greater deviations as underestimation or overestimation. The Austrian forecast model underestimates the daily dose in 3.7% of all cases, whereas 1.7% results from the model and 2.0% from the assumed total ozone content. The hit rate could be found in the order of 40%.
Enhancement of Riboflavin‐mediated Photo‐Oxidation of Glucose 6‐phosphate Dehydrogenase by Urocanic Acid¶
Authors: Silva Eduardo , Herrera Leonardo , Edwards Ana María , de la Fuente Julio , Lissi Eduardo
Published: July 2010

We have investigated the riboflavin (RF)‐sensitized inactivation of glucose 6‐phosphate dehydrogenase (G6PD) in the presence and absence of trans‐urocanic acid (UCA). The inactivation of the enzyme results from its direct oxidation by the excited triplet RF in a Type‐I–photosensitized reaction whose efficiency increases at low oxygen concentration. The addition of histidine to the system produced no change in the inactivation rate, discarding the participation of singlet oxygen in the reaction. On the other hand, the presence of UCA results in its bleaching, with a significant enhancement of RF‐mediated inactivation of G6PD. Both the consumption of UCA and G6PD are faster at low oxygen concentrations. UCA also produced a decrease in the sensitizer photodecomposition yield. These results indicate that the enhancement of the RF‐mediated G6PD inactivation observed in the presence of UCA is not a singlet oxygen–mediated process. It is proposed that UCA consumption and its effect on G6PD inactivation are due to a complex reaction sequence initiated by a direct oxidation of UCA by the excited sensitizer triplet. The oxidation of the semireduced flavin gives rise to reactive oxygen species (ROS) responsible for the increased rate of the process. This is supported by the protection afforded by several additives with ROS removal capacity: benzoate, superoxide dismutase and catalase.
Synthesis, Photophysical Studies and Anticancer Activity of a New Halogenated Water‐Soluble Porphyrin
Authors: Dąbrowski Janusz M. , Pereira Mariette M. , Arnaut Luis G. , Monteiro Carlos J. P. , Peixoto Andreia F. , Karocki Andrzej , Urbańska Krystyna , Stochel Grażyna
Published: July 2010

A water‐soluble halogenated porphyrin, namely 5,10,15,20‐tetrakis(2‐chloro‐3‐sulfophenyl)porphyrin (TCPPSO3H), was prepared and evaluated as sensitizer for photodynamic therapy (PDT). Photophysical properties of TCPPSO3H, such as high photostability, long triplet lifetime and high singlet oxygen quantum yield suggest high effectiveness of this class of halogenated porphyrins in PDT. TCPPSO3H is non‐toxic in the dark and causes a significant photodynamic effect examined against MCF7 (human breast carcinoma), SKMEL 188 (human melanoma) and S91(mouse melanoma) cell lines upon red light irradiation (cutoff < 600 nm) at low light doses. Time‐dependent cellular uptake of TCPPSO3H reached plateau at 120 min and was the highest for S91, 20% lower for MCF7 and 70% lower for SKMEL 188. Our results show that this halogenated water‐soluble porphyrin is an efficient photosensitizer and reveal the potential of this class of compounds as PDT agents.
Chlorpromazine Binding to Na+, K+‐ATPase and Photolabeling: Involvement of the Ouabain Site Monitored by Fluorescence
Authors: Guevara Elmer A. C. , De Lourdes Barriviera Maria , Hassón‐Voloch Aída , Louro Sonia R. W.
Published: July 2010

This work reports the results of ultraviolet irradiation on the interaction of the phototoxic antipsychotic drug chlorpromazine (CPZ) with the sodium pump Na+, K+‐ATPase. The study was performed by monitoring the fluorescence modifications of CPZ itself and of the specific probe anthroylouabain (AO). CPZ association with Na+, K+‐ATPase was found to modify the kinetics of CPZ‐photodegradation. It was demonstrated that UV irradiation produces a stable fluorescent photoproduct of CPZ covalently bound to Na+, K+‐ATPase. The fluorescent probe AO, which specifically binds to the extracellular ouabain site of the pump, was used to localize the CPZ binding site. UV‐irradiation of AO‐labeled Na+, K+‐ATPase treated with CPZ at concentration about 20 μMproduced dose‐dependent modifications of the AO fluorescence,e.g.increased quantum yield and blue shift. The results demonstrated that CPZ binds near the ouabain site. The photo‐induced reaction of CPZ with AO‐labeled Na+, K+‐ATPase protected the ouabain site from the aqueous environment. It was also found that UV irradiation of CPZ‐treated enzyme obstructs the binding of AO, which suggested occlusion of the ouabain site. This effect can be evaluated for a potential use of CPZ in photochemotherapy.
Polymeric Photosensitizer Prodrugs for Photodynamic Therapy
Authors: Campo Marino A. , Gabriel Doris , Kucera Pavel , Gurny Robert , Lange Norbert
Published: July 2010

A targeting strategy based on the selective enzyme‐mediated activation of polymeric photosensitizer prodrugs (PPP) within pathological tissue has led to the development of agents with the dual ability to detect and treat cancer. Herein, a detailed study of a simple model system for these prodrugs is described. We prepared “first‐generation” PPP by directly tethering the photosensitizer (PS) pheophorbide a to poly‐(l)‐lysine via epsilon amide links and observed that by increasing the number of PS on a polymer chain, energy transfer between PS units improved leading to better quenching efficiency. Fragmentation of the PPP backbone by trypsin digestion gave rise to a pronounced fluorescence increase and to more efficient generation of reactive oxygen species upon light irradiation. In vitro tests using the T‐24 bladder carcinoma cell line and ex vivo experiments using mouse intestines illustrated the remarkable and selective ability of these PPP to fluoresce and induce phototoxicity upon enzymatic activation. This work elucidated the basic physicochemical parameters, such as water solubility and quenching/activation behavior, required for the future elaboration of more adaptable “second‐generation” PPP, in which the PS is tethered to a proteolytically stable polymer backbone via enzyme‐specific peptide linkers. This polymer architecture offers great flexibility to tailor make the PPP to target any pathological tissue known to over‐express a specific enzyme.
Interaction of Fusarium solani Lectin with Monosaccharides and Oligosaccharides: A Fluorometric Study
Authors: Khan Feroz , Ahmad Absar , Khan M. Islam
Published: July 2010

The intrinsic fluorescence intensity of Fusarium solani lectin was quenched upon binding to mono‐ and oligosaccharides without any change in the emission maximum and it was used to determine association constants for several sugars and glycans. The lectin interacted very poorly with monosaccharides but well with disaccharides (T‐antigen and LacNAc) with a distinction between β1→4 and β1→3 linkages. Among the monosaccharides, the interaction was observed only with Gal/GalNAc derivatives and not with Glc/Man derivatives. Thermodynamic studies revealed that the binding of the lectin with all the saccharides is enthalpically driven and exothermic in nature. Asialo‐triantennary N‐glycan and asialo‐biantennary N‐glycan showed higher affinity than monovalent LacNAc with significant increase in binding enthalpy, pointing towards the importance of multivalency in the lectin–ligand interactions. Time‐resolved fluorescence measurement indicated the lectin has two lifetimes for tryptophan and the shorter lifetime is affected on ligand binding.
Effects of Low Power Laser Irradiation on Intracellular Calcium and Histamine Release in RBL‐2H3 Mast Cells
Authors: Yang Wen‐Zhong , Chen Ji‐Yao , Yu Ji‐Tong , Zhou Lu‐Wei
Published: July 2010

Although laser irradiation has been reported to promote skin wound healing, the mechanism is still unclear. As mast cells are found to accumulate at the site of skin wounds we hypothesized that mast cells might be involved in the biological effects of laser irradiation. In this work the mast cells, RBL‐2H3, were usedin vitroto investigate the effects of laser irradiation on cellular responses. After laser irradiation, the amount of intracellular calcium ([Ca2+]i) was increased, followed by histamine release, as measured by confocal fluorescence microscopy with Fluo‐3/AM staining and a fluorescence spectrometer witho‐phthalaldehyde staining, respectively. The histamine release was mediated by the increment of [Ca2+]ifrom the influx of the extracellular buffer solution through the cation channel protein, transient receptor potential vanilloid 4 (TRPV4). The TRPV4 inhibitor, Ruthenium Red (RR) can effectively block such histamine release, indicating that TRPV4 was the key factor responding to laser irradiation. These induced responses of mast cells may provide an explanation for the biological effects of laser irradiation on promoting wound healing, as histamine is known to have multi‐functions on accelerating wound healing.
Coupling Short‐Term Changes in Ambient UV‐B levels with Induction of UV‐Screening Compounds†
Authors: Sullivan Joe H. , Gitz Dennis C. , Liu‐Gitz Lan , Xu Chenping , Gao Wei , Slusser James
Published: July 2010

A substantial number of studies have been conducted over the last several decades to assess the potential impacts of long‐term increases in ultraviolet‐B radiation (UV‐B between 280 and 320 nm) that will result from continued depletion of stratospheric ozone. However, seasonal changes, tropospheric chemistry and cloudiness are the dominant factors controlling ambient UV‐B levels on a short‐term or daily basis. The effects of short‐term changes in UV‐B on plant growth, phytochemistry and physiological processes have received relatively little attention. The USDA UV‐B Monitoring and Research Program provides an excellent network of stations that provide an opportunity to monitor long‐term changes in solar UV‐B radiation and evaluate the responses of plants to short‐term variation in UV‐B levels on a near‐real‐time basis. In this study barley (Hordeum vulgareL.) and soybean (Glycine max[L] Merr.) were used as model systems. Emerging seedlings of these species were grown under either near‐ambient levels of UV‐B or under reduced levels (ca90% reduction) in the field. Periodic measurements of foliar UV‐screening compounds were made on separate groups of seedlings planted at intervals over the growing season during contrasting periods of ambient levels of UV radiation. The levels of UV‐screening compounds correlated with UV‐B levels in both species and with UV‐A in soybean but the sensitivity of the response differed between the two species and among the soybean cultivars. Response differences among species may be related to unique secondary chemistry of each species, so one response estimate or action spectrum may not be appropriate for all species.