bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous Production of Superoxide Radical and Singlet Oxygen by Sulphonated Chloroaluminum Phthalocyanine Incorporated in Human Low‐density Lipoproteins: Implications for Photodynamic Therapy¶
Authors: Martins Joana , Almeida Leonor , Laranjinha João
Published: July 2010

Sulfonated chloroaluminum phthalocyanines have been studied for their use in the photodynamic therapy (PDT) of tumors. Plasma low‐density lipoproteins (LDL) are important carriers of phthalocyanines in the blood, but on exposure to visible light, phthalocyanine‐loaded LDL undergo an oxidation process that propagates to erythrocytes. We attempted to identify the reactive species involved in LDL and erythrocyte oxidation by means of electron paramagnetic resonance (EPR) spectroscopy in the presence of 2,2,6,6‐tetramethyl‐4‐piperidone (TEMP) and the spin trap 5,5′‐dimethyl‐1‐pyrroline‐N‐oxide (DMPO). Irradiation of phthalocyanine‐loaded LDL in the presence of DMPO resulted in the formation of a four‐line EPR spectrum with relative intensity of 1:2:2:1 (aN= aH= 14.8 G), characteristic of DMPO‐hydroxyl radical spin adduct. This signal was sensitive to superoxide dismutase and slightly sensitive to catalase, but a mixture of the two enzymatic activities was the most efficient in promoting a decrease in the intensity of the EPR signal. In the presence of erythrocytes, an increase in the quartet intensity for a hematocrit of 1% and 4% was observed, decreasing for higher erythrocyte concentrations. The irradiation of phthalocyanine‐loaded LDL in the presence of TEMP resulted in the formation of a nitroxide radical, 2,2,6,6‐tetramethyl‐4‐piperidone‐N‐oxyl radical, intensity of which was sensitive to histidine, a singlet oxygen (1O2) quencher. Under both incubation conditions, with DMPO and TEMP, the formation of the respective EPR signals required the sensitizer (phthalocyanine), light and oxygen. Overall, the results are compatible with the simultaneous formation of superoxide anion and1O2, implying that Type‐I and Type‐II mechanisms of photochemistry are simultaneously operative in phthalocyanine‐loaded LDL. However, for a constant LDL/phthalocyanine ratio, the formation of oxygen free radicals shows a biphasic behavior with the concentration of LDL increasing and reaching a plateau, whereas the formation of1O2increases linearly with LDL concentration. Erythrocytes at high (physiological) concentrations induced a decrease in the intensity of both EPR signals. The physiological relevance of these findings in the framework of PDT is briefly discussed.
Photodynamic Studies and Photoinactivation of Escherichia coli Using meso‐Substituted Cationic Porphyrin Derivatives with Asymmetric Charge Distribution¶
Authors: Lazzeri Débora , Rovera Marisa , Pascual Liliana , Durantini Edgardo N.
Published: July 2010

The photodynamic activities of novel asymmetrically meso substituted cationic porphyrins, 5,10‐di(4‐methylphenyl)‐ 15,20‐di(4‐trimethylammoniumphenyl)porphyrin iodide 1 and 5‐(4‐trifluorophenyl)‐10,15,20‐tris(4‐trimethylammoniumphenyl)porphyrin iodide 2 and its metal complex with Pd(II) 3, have been investigated in both homogeneous medium bearing photooxidizable substrates and in vitro on a typical gram‐negative bacterium Escherichia coli. The amphiphilic character of porphyrin 2 was increased by the presence of a high‐lipophilic trifluoromethyl group and its photophysical properties changed by forming a complex with Pd(II). Absorption and fluorescence spectroscopic studies were compared in different media. Fluorescence quantum yields (øF) of 0.16 for 1 in tetrahydrofuran and 0.08 for 2 in N, N‐dimethylformamide (DMF) were calculated, whereas no significant emission was detected for Pd(II) porphyrin 3. The singlet molecular oxygen, O2(1Δ(g), production was evaluated using 9,10‐dimethylanthracene in DMF yielding relative values of 1, 0.55 and 0.47 for porphyrins 3, 2 and 1, respectively. A faster decomposition of L‐tryptophan was obtained using Pd(II) porphyrin 3 as sensitizer with respect to the free‐base porphyrins 1 and 2. In biological medium, the behavior of cationic porphyrins 1‐3 were compared with that of 5‐(4‐carboxyphenyl)‐10,15,20‐tris(4‐methylphenyl)porphyrin 4, which was used as a noncationic sensitizer. These porphyrins are rapidly bound to E. coli cells in 5 min and the amount of cell‐bound sensitizer is not appreciably changed incubating the cultures for longer times. The recovered porphyrin 2 after one washing step reaches a value of ∼2.9 nmol/106 cells and this amount remains high even after three washes, indicating that this sensitizer is tightly bound to cells. Photosensitized inactivation of E. coli was analyzed using cells without and with one washing step. In both cases, a higher photoinactivation of cells was found for tricationic porphyrin 2 and 3, causing a ‐5.5 log (99.999%) decrease of cell survival, when treated with 10 μM of sensitizer. Under these conditions, a lower effect was found for porphyrin 1 (‐4 log) whereas sensitizer 4 did not produce appreciable photodamage. The results were also confirmed by growth delay experiments. These studies show that the amphiphilic tricationic porphyrin 2 and 3 bearing a trifluoromethyl group can be a promising model for phototherapeutic agents with potential applications in inactivation of bacteria by photodynamic therapy.
Measurements of the Solar UVR Protection Provided by Shade Structures in New Zealand Primary Schools¶
Authors: Gies Peter , Mackay Christina
Published: July 2010

To reduce ultraviolet radiation (UVR) exposure during childhood, shade structures are being erected in primary schools to provide areas where children can more safely undertake outdoor activities. This study to evaluate the effectiveness of existing and purpose built shade structures in providing solar UVR protection was carried out on 29 such structures in 10 schools in New Zealand. Measurements of the direct and scattered solar UVR doses within the central region of the shade structures were made during the school lunch break period using UVR‐sensitive polysulfone film badges. These measurements indicate that many of the structures had UVR protection factors (PF) of 4‐8, which was sufficient to provide protection during the school lunch hour. However, of the 29 structures examined, only six would meet the suggested requirements of UVR PF greater than 15 required to provide all‐day protection.
A Novel Mitochondrial Signaling Pathway Activated by Visible‐to‐near Infrared Radiation¶
Authors: Karu Tiina I. , Pyatibrat Ludmila V. , Afanasyeva Natalia I.
Published: July 2010

The number of cells attached to glass substratum increases if HeLa cell suspension is irradiated with monochromatic visible‐to‐near infrared radiation before plating (the action spectrum with maxima at 619, 657, 675, 700, 740, 760, 800, 820, 840 and 860 nm). Treating of cell suspension with sodium azide (2 × 10−5M), sodium nitroprusside (5 × 10−5M), ouabain (1 × 10−6M) or amiloride (1.7 × 10−5M) before irradiation significantly modifies the spectrum of cell attachment enhancement. A light‐induced mitochondrial signaling pathway can be regulated by small ligands directly binding to the catalytic center of cytochromecoxidase (N3, NO) as well as by chemicals specifically binding to plasma membrane enzymes (ouabain, amiloride). The comparative analysis of action spectra allows the conclusions that first, CuAand CuBchromophores of cytochromecoxidase could be involved as photoacceptors and second, various signaling pathways (reaction channels) between cytochromecoxidase and cell attachment regulation are at work.
The Topical Isoflavonoid NV‐07α Reduces Solar‐simulated UV‐induced Suppression of Mantoux Reactions in Humans¶
Authors: Friedmann Adam C. , Halliday Gary M. , Barnetson Ross StC. , Reeve Vivienne E. , Walker Catherine , Patterson Clare R. S. , Damian Diona L.
Published: July 2010

UV radiation suppresses delayed‐type hypersensitivity responses to intradermally injected tuberculin purified protein derivative in Mantoux‐positive individuals. The effect of the topically administered isoflavonoid NV‐07α, a synthetic derivative of the isoflavonoid equol, on UV‐induced suppression of Mantoux reactions was assessed in 18 healthy Mantoux‐positive volunteers. A single, fixed dose of solar‐simulated UV radiation was delivered to the volunteers'lower backs. Different concentrations of NV‐07α or its vehicle were applied to different sites within the irradiated field immediately after UV exposure and again 24 h later. Forty‐eight hours after irradiation, Mantoux testing was performed at both the irradiated sites and adjacent, unirradiated sites. The intensity of Mantoux reactions was measured 72 h later with a reflectance erythema meter and by measuring the diameter of each reaction. Although lower concentrations of NV‐07α (0.5 and 2 mM) did not prevent UV immunosuppression, 4 mM NV‐07α partially but significantly attenuated UV‐induced suppression of Mantoux‐induced erythema. Minimal erythema doses were also determined for sites treated with NV‐07α or its vehicle immediately after UV exposure. NV‐07α had no significant effects on UV erythema. We conclude that 4 mM NV‐07α prevented the suppressive effects of UV radiation on Mantoux responses in humans but did not affect UV‐induced erythema at the concentrations used.
Solar Ultraviolet‐B Radiation in Urban Environments: The Case of Baltimore, Maryland¶†
Authors: Heisler Gordon M. , Grant Richard H. , Gao Wei , Slusser James R.
Published: July 2010

Ultraviolet‐B radiation (UV‐B, 280–320 nm) has important effects in urban areas, including those on human health. Broadband UV‐B radiation is monitored in Baltimore, MD, as part of the Baltimore Ecosystem Study, a long‐term ecological research program. We compare broadband UV‐B irradiance in Baltimore with UV‐B at two nearby locations: a more rural station 64 km southeast and a suburban station 42 km southwest. The monitoring station in Baltimore is on the roof of a 33‐m‐tall building; there are no significant obstructions to sky view. The U.S. Department of Agriculture UV‐B Monitoring and Research Program provided all sensors, which were calibrated at the National Oceanic and Atmospheric Administration Central UV Calibration Facility. UV‐B irradiances at the three sites generally were similar. Over all conditions, Baltimore and the suburban site measured 3.4% less irradiance than the rural site. This difference is within the anticipated ±3% calibration uncertainty of the pyranometers. On 59 days with cloud‐free conditions at all three sites, average differences in measured UV‐B among the three sites were even smaller; Baltimore measured 1.2% less irradiance than the rural site. High aerosol optical thickness strongly reduced daily UV‐B dose, whereas [SO2] had no influence. Surface O3 increased with increasing UV‐B dose when [NO2] exceeded 10 ppb.
The Triplet‐state Lifetime of Indole Derivatives in Aqueous Solution¶
Authors: Strambini Giovanni B. , Kerwin Bruce A. , Mason Bruce D. , Gonnelli Margherita
Published: July 2010

An important feature of tryptophan phosphorescence, crucial for probing protein structure and dynamics, is the drastic reduction of the lifetime (τ) in fluid solutions. Initial reports of indole and derivatives showed that τ decreases from 6 s in rigid glasses to about 1 ms in aqueous solutions at ambient temperature. Recently a report by Fischer et al. questioned the validity of the millisecond lifetime, claiming that in millimolar electrolyte solutions τ is about 40 μs, similar to the 12–30 μs of earlier determinations based on flash photolysis. Longer lived phosphorescence was detected in pure water but because it exhibited an initial growing phase and an anomalously large triplet yield, the emission was attributed to an artifact arising from the slow, first‐order, geminate recombination of the radical cation and electron generated by photochemistry. In this study, we reexamine both the phosphorescence lifetime and the triplet quantum yield of indole, N‐acetyl tryptophanamide (NATA), N‐methyl tryptophan and the tryptophan‐glycine‐glycine tripeptide under the same conditions adopted by Fischer et al. as well as over a wider range of electrolyte and buffering salts concentrations, pH, solvent and temperture. Throughout, the results show that the phosphorescence decay is slow and uniform down to the 12 μs resolution of the instrument, with no evidence of short‐lived, 40 μs‐like components. Most compelling was the similarity between the fluorescence‐normalized triplet yield of indole derivatives in water and that of W59 in the protein ribonuclease T1 or of NATA in rigid glasses. Its invariance over experimental conditions that varied the production of photoproducts several fold and the characteristic susceptibility of the triplet lifetime to O2, proton and ground state quenching demonstrated that the triplet state was formed predominantly through normal intersystem crossing and that its unquenched lifetime was at least 9 ms.
High‐resolution Studies of Lung Surfactant Collapse¶
Authors: Aga Rachel Sibug , Dunn Robert C.
Published: July 2010

Survanta is a replacement lung surfactant (LS) used in the treatment of respiratory distress syndrome (RDS), the fourth leading cause of infant mortality in the United States. It consists of purified LS from bovine sources and retains the surfactant proteins (SP) SP‐B and SP‐C, both thought to be important in proper respiratory function. As such, it provides a useful and biologically relevant model system to probe the structure and function of natural LS. Here, we report results from high‐resolution studies on model monolayers formed from Survanta to probe the mechanism of collapse at high surface pressure. Our results show the formation of two different collapse structures. At 62 mN/m, slightly below the collapse pressure, monolayer collapse occurs through buckling. Confocal fluorescence measurements on supported films reveal regions of overlapping phase structure in the films that mark the transition from monolayer to multilayer. Simultaneous near‐field scanning optical microscopy fluorescence and force measurements show that the transition seen in the fluorescence measurements accompanies corresponding ∼4–5 nm changes in membrane topography. This change in height is consistent with bilayer formation on monolayer collapse. Analysis of the phase structure near the transitions also suggests that the buckling occurs from a continuous film. However, when the film is compressed to its collapse pressure of 65 mN/m, buckling is no longer evident in the collapsed region. In addition, multilayers and lipid‐protein aggregates that are up to 40 nm higher than the monolayer are observed in the collapsed film at this pressure.
Effects of Low‐power Laser Irradiation on Cell Locomotion in Protozoa¶
Authors: Koutna Marketa , Janisch Roman , Unucka Marek , Svobodnik Adam , Mornstein Vojtech
Published: July 2010

Low‐power lasers are commonly used in human medicine for treatment of various pathological conditions, but mechanisms of their healing effects are still poorly understood. The results of this study provide information related to these effects at the cellular level. Two different protozoan species, Euglena gracilis and Tetrahymena thermophila, were used to study changes in locomotion behavior in response to low‐power lasers. The cells were irradiated at 830 and 650 nm generated by a semiconductor laser (99 J/cm2, 360 mW) and a laser pointer (0.75 J/cm2, 5 mW), respectively, and their locomotion was recorded by a TV camera and analyzed using computer software. Exposure to laser light, regardless of the wavelength, resulted in increased cell velocity in both species (P < 0.001). Exposure to 650 nm produced an equal increase in median cell velocity in both E. gracilis (19.0%) and T. thermophila (18.2%), and some increase persisted in the postirradiation 30 s period. Irradiation by the 830 nm laser resulted in a markedly higher response in Tetrahymena (29.4%) than in Euglena (15.2%), and the two median values remained increased after irradiation was discontinued. Different reactions found in the species studied and some mechanisms underlying the response of cells to radiation are discussed.
Protective Effect of Superoxide Dismutase Against Hair Graying in a Mouse Model¶
Authors: Emerit I. , Filipe P. , Freitas J. , Vassy J.
Published: July 2010

Oxygen free radicals play a role in the aging process, and the protective effect of various antioxidants has been intensively studied, in particular for cutaneous aging. Besides hereditary factors, free radical‐mediated damage to melanocytes of the hair follicle has been considered as a mechanism for aging of the hair. It was the aim of this study to evaluate the role of photosensitization reactions for hair graying and to demonstrate potential protective effects of superoxide dismutase (SOD). Mice with black hair were depilated with the fingertips on a surface of 6 × 2.5 cm on both sides of the dorsum. The right side received five applications of a SOD‐containing gel before exposure to psoralen (concentration 0.5 mg/mL) plus UV‐A (365 nm, 4 J/cm2). The left side was pretreated in the same way with a gel free of SOD. When the hair started growing again, the SOD‐protected side was covered with black hair, whereas the hair on the vehicle‐treated side was gray or white in 27 of the 30 animals studied. The 0.01% SOD concentration was as protective as the 0.1% concentration. Heat‐inactivated SOD, applied in another five animals, was not protective. Using fluorescent labeling of the SOD with fluorescein isothiocyanate, epifluorescence microscopy and digital imaging processing, we show that SOD applied to the skin surface penetrates through the follicular appendages, as well as through the unbroken stratum corneum. Our findings suggest that superoxide radicals, generated by interaction of UV‐A light with the sensitizer, initiated the formation of secondary products with well‐known DNA‐damaging effects, such as lipid peroxidation products and tumor necrosis factor alpha. SOD prevented the damage to melanocyte DNA by dismutating superoxide. Photosensitization may be another mechanism for hair graying, which can be influenced by antioxidants. Given the large number of exogenous and endogenous sensitizers, this mechanism deserves further study for human hair graying.
pH‐Dependent modification of lipophilicity of porphyrin‐type photosensitizers
Authors: Čunderliková Beata , Kaalhus Olav , Čunderlik Róbert , Mateášik Anton , Moan Johan , Kongshaug Magne
Published: July 2010

Structural modifications of photosensitizers (changes in protonation, ionic state and aggregation state) under different environmental conditions should be precisely determined to understand the interaction of the photosensitizers with biological systems. In the present study partition coefficients of hematoporphyrin IX (HpIX), disulfonated meso‐tetraphenylporphine, meso‐tetra(3‐hydroxyphenyl) porphine (mTHPP) and meso‐tetra (3–hydroxyphenyl)chlorin in the 1‐octanol‐phosphate buffer system were determined in the pH region 4.0‐8.0. Only the partition coefficients of HpIX and mTHPP were found to be pH dependent. Computer processing of fluorimetric titration data was applied to estimate pKa values of the imino nitrogens of mTHPP. Monoprotonated species of mTHPP seem to be unstable or nonexistent. The possibility that both imino nitrogens of this dye are protonated according to a common pKa is proposed. The pKa value of the imino nitrogens of mTHPP was found to be 2.99 ± 0.04 after the application of a model taking aggregation of the drug into account. The contributions of various qqueous ionic species of mTHPP as functions of pH were calculated and compared with partition coefficients.
Preliminary study on photoproduction of hydroxyl radicals in aqueous solution with Aldrich humic acid, algae and Fe(III) under high‐pressure mercury lamp irradiation
Authors: Liu Xianli , Xu Dong , Wu Feng , Liao Zhenhuan , Liu Jiantong , Deng Nansheng
Published: July 2010

Under a high‐pressure mercury lamp (HPML) and using an exposure time of 4 h, the photoproduction of hydroxyl radicals (*OH) could be induced in an aqueous solution containing humic acid (HA). Hydroxyl radicals were determined by high performance liquid chromatography using benzene as a probe. The results showed that *OH photoproduction increased from 1.80 to 2.74 μM by increasing the HA concentration from 10 to 40 mg L−1 at an exposure time of 4 h (pH 6.5). Hydroxyl radical photoproduction in aqueous solutions of HA containing algae was greater than that in the aqueous solutions of HA without algae. The photoproduction of *OH in the HA solution with Fe(III) was greater than that of the solution without Fe(III) at pH ranging from 4.0 to 8.0. The photoproduction of *OH in HA solution with algae with or without Fe(III) under a 250 W HPML was greater than that under a 125 W HPML. The photoproduction of *OH in irradiated samples was influenced by the pH. The results showed that HPML exposure for 4 h in the 4‐8 pH range led to the highest *OH photoproduction at pH 4.0.
The role of the carotenoids in the photoadaptation of the brown‐colored sulfur bacterium Chlorobium phaerobacteroides
Authors: Hirabayashi Hiroki , Ishii Takasada , Takaichi Shinichi , Inoue Kazuhito , Uehara Kaku
Published: July 2010

The brown‐colored sulfur bacterium Chlorobium (Cb.) phaeobacteroides 1549 (new name, Chlorobaculum limnaeum 1549) contains many kinds of carotenoids as well as bacteriochlorophyll (BChl) e. These carotenoids were identified with C18‐high‐performance liquid chromatography, absorption, mass and proton nuclear magnetic resonance spectroscopies and were divided into two groups: the first is carotenoid with one or two φ‐end groups such as isorenieratene and β‐isorenieratene and the second is carotenoid with one or two β‐end groups such as β‐zeacarotene, β‐carotene and 7,8‐dihydro‐β‐carotene. The latter 7,8‐dihydro‐β‐carotene was found to be a novel carotenoid in nature. OH‐γ‐Carotene glucoside laurate and OH‐chlorobactene glucoside laurate were also found as minor components. The distribution of BChl e homologs in Cb. phaeobacteroides cultivated under various light intensities did not change, but the carotenoid to BChl e ratio changed markedly: carotenoid with the φ‐end group maintained the same ratio to BChl e, whereas that with the β‐end group increased with increasing light intensity. The cells cultured under low‐light intensity contained more φ‐end carotenoids than β‐end. In Cb. phaeobacteroides the wavelength of the Qy band of BChl e aggregates did not change. We suggested that Cb. phaeobacteroides photoadapts to light intensity by changing the carotenoid composition.
Cooperative Effects in the Photophysical Properties of Self‐associated Triguanosine Diphosphates¶
Authors: Markovitsi Dimitra , Gustavsson Thomas , Sharonov Alexei
Published: July 2010

The present study deals with the photophysical properties of triguanosine diphosphate in aqueous solutins, which are compared with those of the 2′‐deoxyguanosine monophosphate. They are studied by steady‐state absorption and fluorescence spectroscopy as well as by time‐resolved fluorescence spectroscopy with femtosecond resolution. The temperature, salt and concentration dependence of the absorption and fluorescence spectra reveal that association of the trimers takes place. The resulting aggregates could correspond to a tetraplex structure. The aggregate fluorescence quantum yield is higher and the fluorescence lifetime much longer than those of the monomer. These results show the interaction between guanosine residues that may manifest itself via self‐solvation, hydrogen bonding and / or delocalization of the excitation.
Optical Spectroscopy of Hydrophobic Sunscreen Molecules Adsorbed to Dielectric Nanospheres¶
Authors: Krishnan Rajagopal , Carr Aaron , Blair Elizabeth , Nordlund Thomas M.
Published: July 2010

Fluorescence and absorption spectra of hydrophobic sunscreens, weakly fluorescent octyl methoxycinnamate, moderately fluorescent octyl salicylate and highly fluorescent 2‐ethylhexyl‐4‐(dimethylamino) benzoate (padimate O) adsorbed to dielectric microspheres in aqueous suspension, have been compared with spectra in organic solution. The fluorescence of adsorbed salicylate and padimate is enhanced compared with fluorescence in methanol: about a factor of 6 and 30 in terms of fluorescence yield per molecule of salicylate and padimate, respectively, Cinnamate, which has a low fluorescence yield, does not show a comparable fluorescence enhancement. The fluorescence amplification is independent of sphere diameter from 30 to 1500 nm, at least for salicylate. The enhancement, as well as the location of absorption spectral peaks, is consistent with a low‐dielectric constant environment of the molecules, in spite of the presumed location near the interface between polystyrene (E = 2.4–3.8) and water (E = 78). The adsorbed state of these sunscreens represents a proposed improved in vitro model for the environment of sunscreens in vivo, as well as a general model for chromphores in heterogeneous environments.
Novel Methyl Helianthrones as Photosensitizers: Synthesis and Biological Evaluation¶
Authors: Rahimipour Shai , Litichever‐Coslovsky Naomi , Alaluf Moran , Freeman Dalia , Ehrenberg Benjamin , Weiner Lev , Mazur Yehuda , Fridkin Mati , Koch Yitzhak
Published: July 2010

A combination of light, oxygen and a photosensitizer is used to induce death of cancer cells by photodynamic therapy. In this study, we have synthesized several new methyl helianthrone derivatives and compared their phototoxicity with that of hypericin. In contrast to hypericin, methyl helianthrones are soluble in aqueous solutions and have a broad range of light absorbance, which allows the use of polychromatic light. Structural modifications of methyl helianthrone demonstrated that substitution of hydrogen atoms of methyl helianthrone at Positions 2 and 5 with Br atoms or methylation of its phenolic hydroxyls, significantly increases the corresponding singlet oxygen quantum yield and their phototoxicity toward αT3‐1, M2R and LNCaP cells. The phototoxicity of some of these compounds was similar to that of hypericin. Methyl helianthrones, like hypericin, accumulated mainly in the perinuclear region as evident by confocal microscopy. Irradiation of cells pretreated with methyl helianthrone derivatives generates intracellular reactive oxygen species and lipid free radicals, as shown by a fluorescentic probe and electron paramagnetic resonance methods, respectively. The phototoxicity of these methyl helianthrones as well as their ability to oxidize membrane lipids were significantly decreased on addition of specific Type‐II inhibitors, suggesting the involvement of singlet oxygen as the main oxidant.
Investigations of the Solvent Polarity Effect on the Photophysical Properties of Coumarin‐7 Dye¶
Authors: Satpati Ashish , Senthilkumar Sadasivam , Kumbhakar Manoj , Nath Sukhendu , Maity Dilip Kumar , Pal Haridas
Published: July 2010

Photophysical investigations of coumarin‐7 (C7) dye in different solvents using absorption, steady‐state fluorescence and time‐resolved fluorescence measurements reveal the behavioral changes of the dye in nonpolar and other solvents. In moderate to higher polarity solvents, the experimental parameters such as fluorescence quantum yield (φf), fluorescence lifetime (φf), radiative rate constant (kf), nonradiative rate constant (knr) and Stokes' shift (Δv̄) follow almost linear correlations with the Lippert‐Mataga solvent polarity parameter Δf but show unusual deviations in nonpolar solvents. From the observed results, it is inferred that the dye exists in a planar intramolecular charge transfer structure in moderate to higher polarity solvents, but in nonpolar solvents, the dye exists in a nonplanar structure with its 7‐NEt2 group adopting a pyramidal type of configuration. Unlike some of the other coumarin dyes, namely coumarin‐120 (C120) (4‐CH3‐7‐NH2‐1,2‐benzopyrone) and coumarin‐151 (C151) (4‐CF3‐7‐NH2‐1,2‐benzopyrone), which also show similar structural changes in nonpolar and other solvents, the C7 dye does not show any activation‐controlled deexcitation process in nonpolar solvents. This is attributed to the very slow flip‐flop motion of the 7‐NEt2 group of the C7 dye in comparison with the very fast flip‐flop motion of the 7‐NH2 group in the C120 and C151 dyes. Qualitative potential energy diagrams are presented to rationalize the observed results of C7 dye and to compare these with those of the other dyes such as C120 and C151. A support for the observed results and interpretation has also been obtained from quantum chemical calculations on the structures of the C7 dye.
Alterations in Mitochondrial and Apoptosis‐regulating Gene Expression in Photodynamic Therapy‐resistant Variants of HT29 Colon Carcinoma Cells¶
Authors: Shen Xiao Yun , Zacal Natalie , Singh Gurmit , Rainbow Andrew J.
Published: July 2010

Photodynamic therapy (PDT) is a novel cancer therapy inducing irreversible photodamage to tumor tissue via photosensitizer‐mediated oxidative cytotoxicity. The cellular and molecular responses associated with PDT are only partially understood. We have reported previously the generation of several photosensitizer‐specific PDT‐resistant cell variants of HT29 human colon adenocarcinoma cells by selecting cells from sequential PDT treatment using different photosensitizers. In this report, we describe the use of messenger RNA (mRNA) differential display to identify genes that were differentially expressed in the parental HT29 cells compared with their resistant variants. In comparison with parental HT29 cells, mRNA expression was increased in the PDT‐resistant cell variants for BNIP3, estrogen receptor‐binding fragmentassociated gene 9, Myh‐1c, cytoplasmic dynein light chain 1, small membrane protein I and differential dependent protein. In contrast, expression in the PDT‐resistant variants was downregulated for NNX3, human HepG2 3′region Mbol complementary DNA, glutamate dehydrogenase, hepatomaderived growth factor and the mitochondrial genes coding for 16S ribosomal RNA (rRNA) and nicotinamide adenine dinucleotide (NADH) dehydrogenase subunit 4. The reduction for mitochondrial 16S rRNA in the PDT‐resistant variants was confirmed by Northern blotting, and the elevated expression of the proapoptotic BNIP3 in the PDT‐resistant variants was confirmed by Northern and Western blotting analysis. We also examined the expression of some additional apoptosis‐regulating genes using Western blotting. We show an increased expression of Bcl‐2 and heat shock protein 27 and a downregulation of Bax in the PDT‐resistant variants. In addition, the mutant p53 levels in the parental HT29 cells were reduced substantially in the PDT‐resistant variants. We suggest that the altered expression in several mitochondria1 and apoptosisregulating genes contributes to PDT resistance.
Photocatalytic Degradation of Toluene Using a Novel Flow Reactor with Fe‐doped TiO2 Catalyst on Porous Nickel Sheets¶
Authors: Dezhi Sun , Sheng Chen , Chung Jong Shik , Xiaodong Duan , Zhibin Zhu
Published: July 2010

A novel continuous‐flow photocatalytic reactor was designed to decompose toluene by using porous nickel sheets that were coated with a Fe‐doped TiO2 catalyst. While locating the UV lamp at the central axis, the catalyst sheets were located along the inner wall and positioned vertically with an equal space of 50 mm along the reactor. This geometry ensures better use of UV light, and a zigzag flow pattern of gas between the vertically located sheets provides for better mass transfer. The X‐ray diffraction, scanning electron microscope and electric field‐induced surface photovoltage spectra characterizations showed that Fe3+ ions were embedded effectively and distributed evenly throughout the TiO2 crystal lattice and an optimum molar ratio of Fe:Ti was 0.007. The reactor was used to investigate the factors that affect toluene degradation. The results showed that inlet toluene concentration, relative humidity and gas flow rate significantly affect toluene decomposition. The conversion decreases as inlet concentration increases. Degradation efficiencies of more than 95 % can be achieved provided that the toluene concentration is kept below 3200 mg/m3. The conversion is affected little when oxygen content exceeds 21%. The optimal relative humidity is 25%. From the experimental data, a rate constant k of 131 mg/(m3.min) and Langmuir adsorption coefficient K of 0.0175 m3/mg were obtained.
Molecular Responses to Stress Induced in Normal Human Caucasian Melanocytes in Culture by Exposure to Simulated Solar UV¶
Authors: Marrot Laurent , Belaïdi Jean‐Philippe , Jones Christophe , Perez Philippe , Meunler Jean‐Roch
Published: July 2010

Melanocytes play a central role in the response of skin to sunlight exposure. They are directly involved in UV‐induced pigmentation as a defense mechanism. However, their alteration can lead to melanoma, a process where the role of sun overexposure is highly probable. The transformation process whereby UV damage may result in melanoma initiation is poorly understood, especially in terms of UV‐induced genotoxicity in pigmented cells, where melanin can act either as a sunscreen or as a photosensitizer. The aim of this study was to analyze the behavior of melanocytes from fair skin under irradiation mimicking environmental sunlight in terms of spectral power distribution. To do this, normal human Caucasian melanocytes in culture were exposed to simulated solar UV (SSUV, 300–400 nm). Even at relatively high doses (until 20 min exposure, corresponding to 12 kJ/m2 UV‐B and 110 kJ/m2 UV‐A), cell death was limited, as shown by cell viability and low occurrence of apoptosis (caspase‐3 activation). Moreover, p53 accumulation was three times lower in melanocytes than in unpigmented cells such as fibroblasts after SSUV exposure. However, an important fraction of melanocyte population was arrested in G2‐M phase, and this correlated well with a high induction level of the gene GADD45, 4 h after exposure. Among the genes involved in DNA repair, gene XPC was the most inducible because its expression increased more than two‐fold 15 h after a 20 min exposure, whereas expression of P48 was only slightly increased. In addition, an early induction of Heme Oxygenase 1 (HO1) gene, a typical response to oxidative stress, was also observed for the first time in melanocytes. Interestingly, this induction remained significant when melanocytes were exposed to UV‐A radiation only (320–400 nm), and stimulation of melanogenesis before irradiation further increased HO1 induction. These results were obtained with normal human cells after exposure to SSUV radiation, which mimicked natural sunlight. They provide new data related to gene expression and suggest that melanin in light skin could contribute to sunlight‐induced genotoxicity and maybe to melanocyte transformation.
Antioxidant Defenses and DNA Damage Induced by UV‐A and UV‐B Radiation in the Crab Chasmagnathus granulata (Decapoda, Brachyura)¶
Authors: Gouveia Glauce R. , Marques Daiane S. , Cruz Bruno P. , Geracitano Laura A. , Nery Luiz E. M. , Trindade Gilma S.
Published: July 2010

The photoprotector role of pigment dispersion in the melanophores of the crab, Chasmagnathus granulata, against DNA and oxidative damages caused by UV‐A and UV‐B was investigated. Intact and eyestalkaless crabs were used. In eyestalkless crabs, the dorsal epidermis of the cephalothorax (dispersed melanophores) and the epidermis of pereiopods (aggregated melanophores) were analyzed. Intact crabs showed only dispersed melanophores in the two epidermis. Antioxidant enzymes activity and lipoperoxidation content were analyzed after UV‐A (2.5 J/cm2) or UV‐B (8.6 J/sm2) irradiation. DNA damage was analyzed by single cell electrophoresis (comet) assay, after exposure to UV‐B (8.6 J/cm2). UV‐A radiation increased the glutatione‐S‐transferase activity in the pereiopods epidermis of eyestalkless crabs (P < 0.05). UV‐B radiation induced DNA damage in the dorsal epidermis of eyestalkless crabs (P < 0.005). In pereiopod epidermis of eyestalkless crabs, there was no significant difference between control and UV‐B‐exposed crabs. In the pereiopods epidermis of eyestalkless, the control group showed higher scores of DNA damage and ∼50% of cellular viability. Because in eyestalkless and irradiated crabs the cellular viability was ∼5%, it was not possible to observe nuclei for determination of DNA damage. The findings show that melanophores can play a role in the defense against harmful effects of a momentary exposure to UV radiation.
Photophysics in Motionally constrained Bioenvironment: Interactions of Norharmane with Bovine Serum Albumin¶
Authors: Mallick Arabinda , Chattopadhyay Nitin
Published: July 2010

Steady‐state photophysics of norharmane (NHM), a bioactive alkaloid, has been studied in the presence of a model transport protein, bovine serum albumin (BSA). The emission spectrum undergoes a remarkable change upon addition of BSA to the aqueous solution of NHM in buffer. Addition of BSA leads to a marked increase in the fluorescence anisotropy of the neutral species of NHM, although the fluorescence anisotropy for the cationic species is almost invariant to BSA addition, suggesting that the neutral species is located in a motionally restricted environment of BSA, whereas the cationic species remains in the bulk aqueous phase. The binding constant (K) and free energy change (ΔG) for the probe‐protein binding have been calculated from the fluorescence data. Light has been thrown on the action of urea on protein‐bound NHM. The denaturation study suggests that the protein, in its native form, binds with NHM. Polarity of the microenvironment around the probe has been determined from a comparison of the fluorescence properties of the two prototropic species of NHM in water‐dioxane mixture with varying composition.
Changes in the Room‐temperature Emission Spectrum of Chlorophyll During Fast and Slow Phases of the Kautsky Effect in Intact Leaves¶
Authors: Franck Fabrice , Dewez David , Popovic Radovan
Published: July 2010

Changes in the room‐temperature emission spectrum of chlorophyll (Chl) were analyzed using fast diode‐array recordings during the Kautsky effect in mature and in greening barley leaves. In mature leaves, the comparison of Fo (basal level of fluorescence yield at transient O) and FM (maximum level of fluorescence yield at transient M) spectra showed that the relative amplitude of total variable fluorescence was maximal for the 684 nm Photosystem II (PSII) band and minimal for the 725 nm Photosystem I band. During the increase from Fo to FM a progressive redshift of the spectrum of variable fluorescence occurred. This shift reflected the different fluorescence rise kinetics of different layers of chloroplasts inside the leaf. This was verified by simulating the effect of screening on the emission spectrum of isolated chloroplasts and by experiments on greening leaves with low Chl content. In addition, experiments performed at different greening stages showed that the presence of uncoupled Chl at early‐greening stages and lightharvesting complex II (LHCII) at later stages have detectable but minor effects on the shape of room‐temperature emission spectra. When strong actinic light was applied to mature green leaves, the slow fluorescence yield, which declined from FM to FT (steady‐state level of fluorescence yield at transient T), was accompanied by a slight redshift of the 684 nm PSII band because of nonphotochemical quenching of short‐wavelengthemitting Chl ascribed to LHCII.
Exposure Geometry and Spectral Environment Determine Photobiological Effects on the Human Eye¶†
Authors: Sliney David H.
Published: July 2010

Photobiological effects upon the human retina, cornea and lens are highly dependent on the optical exposure geometry as well as spectral characteristics of the exposure. The organ of sight is exquisitely sensitive to light because it performs well in very low nighttime illumination levels and yet it also must adapt to extremely bright environments where light exposures are greater by many orders of magnitude. The eye has evolved to protect itself reasonably well against excessive exposure in bright environments. The retina is minimally exposed in extremely bright environments and the cornea and lens are surprisingly well protected in harsh environments. Although these protective mechanisms are good, they are not perfect and adverse changes from both acute and chronic exposures to sunlight still exist. The geometrical protective factors must be understood and appreciated whenever assessing potential adverse effects of environmental UV radiation and light on ocular structures. These natural ocular protective factors also work with the ever‐changing spectrum of sunlight and the different spectral distribution of light and UV radiation across the eye's field of view. Spectral characteristics of the ocular media are also important. One can visualize a series of intraocular color filters that progressively filter shorter wavelengths and thereby aid in color vision, reduce the impact of chromatic aberrations and significantly reduce the optical radiation hazards to the lens and retina.
Comparisons of the Structural and Chemical Properties of Melanosomes Isolated from Retinal Pigment Epithelium, Iris and Choroid of Newborn and Mature Bovine Eyes¶
Authors: Liu Yan , Hong Lian , Wakamatsu Kazumasa , Ito Shosuke , Adhyaru Bhavin B. , Cheng Chl‐Yuan , Bowers Clifford R. , Simon John D.
Published: July 2010

Melanosomes were isolated from the retinal pigment epithelium (RPE), iris and choroid of mature (age >2 years) and newborn (age <1 week) bovine eyes. Scanning electron microscopy was utilized to analyze the morphology of the melanosomes, which were found to vary among different tissues and different ages. While the total content of amino acids differs slightly (ranging from 9% to 15% by mass), the distributions of the amino acids are similar. The pheomelanin content is low in the choroid and the RPE (0.1–0.5%), and moderate in the iris (<2%); therefore, the major melanin component of bovine eye melanosomes is eumelanin, independent of the shape of the melanosomes. The yields of pyrrole‐2,3,5‐tricarboxylic acid from melanosomes decrease in the following order: choroid > iris > RPE, and exhibit decreasing yields with age. 13C solid‐state nuclear magnetic resonance (NMR) spectroscopic analysis of iris and choroid melanosomes indicates the same trends. These observations suggest that the 5,6‐dihydroxyindole‐2‐carboxylic acid contents decrease in the following order: choroid > iris > RPE, and decrease with age. Moreover, the 13C solid‐state NMR spectra show (1) for the same age samples, the CH:Cq ratio for choroid is larger than that for iris melanosomes; and (2) an increase in the concentration of carbonyl groups with age within each type of melanosome.
Photochemistry of Naphthalene Diimides: EPR Study of Free Radical Formation via Photoredox Process¶
Authors: Reszka Krzysztof J. , Takayama Masami , Slk Robert H. , Chignell Colin F. , Salto Isao
Published: July 2010

Earlier studies have shown that on exposure to UVA, hydroperoxynaphthalene diimide (IA) generates hydroxyl radicals, induces DNA strand scission, and kills cells. Here we employed electron paramagnetic resonance (EPR) and spin trapping to investigate the free radical photochemistry of IA and that of related naphthalene diimides, which are devoid of the hydroperoxyl moiety (N,N′‐bis[2‐methyl]‐1,4,5,8‐naphthaldiimide [IB], N,N′‐bis[2‐thiomethyl‐2‐methoxyethyl]‐1,4,5,8‐naphthaldiimide [IC]) and therefore are unable to generate hydroxyl radicals. It is shown that on UV irradiation (>300 nm) in air‐free methanol or ethanol solutions all these naphthalene diimides undergo one‐electron reduction to corresponding anion radicals, positively identified by EPR. With EPR and a spin trap 5,5‐dimethyl‐1‐pyrroline N‐oxide (DMPO), we found that the photogeneration of the naphthalene diimide radicals is concomitant with the formation of radicals from the solvents, presumably through electron/hydrogen atom abstraction by photoactivated diimides. Irradiation of IA, IB or IC in the presence of oxygen generates superoxide, which was detected as a DMPO adduct. The high photoreactivity of IB and IC supports the notion that hydroperoxide IA can induce oxidative damage via photoprocesses that are independent of *OH generation. These observations could be pertinent to the application of naphthalene diimides as selective photonucleases, PDT anticancer agents or both.
Temperature Effect on the Fluroescence Anisotropy Decay Dynamics of Coumarin‐153 Dye in Triton‐X‐100 and Brij‐35 Miscellar Solutions¶
Authors: Kumbhakar Manoj , Mukerjee Tulsi , Pal Haridas
Published: July 2010

The fluorescence anisotropy decay dynamics of the fluorescent probe Coumarin‐153 (C153) have been investigated in two neutral micelles, Triton‐X‐100 (TX‐100) and Brij‐35 (BJ‐39, at different temperatures and analyzed on the basis of the wellknown two‐step model. Because steady‐state fluorescence spectra of the above probe do not show any noticeable changes with respect to temperature, for either of the studied micelles, suggests a similar polarity in the microenvironment around the probe at all the temperatures studied. The anisotropy results indicated that, for both the micelles, the fluidity inside the Palisade layer increases with temperature. However, the temperature effect on the anisotropy decay is relatively more pronounced in TX‐100 than in BJ‐35. It is inferred that the temperature effect on the anisotropy decay in the BJ‐35 micelle is mainly due to the thermal effect on the microviscosity in the micellar phase. In the case of TX‐100, the results indicate that, along with the above thermal effect, an additional effect is observed due to the increased size and hydration of the micelle with temperature, with the result being that the fluorescence anisotropy decay in TX‐100 is more sensitive to temperature than in BJ‐35. In the TX‐100 micelle, our studies show that with an increase in temperature, even though the micellar size increases substantially, the distance of the probe from the micellar core does not increase that significantly. Thus, with increasing temperature, the probe undergoes a relative migration toward the micellar core to avoid the increased hydration in the micellar Palisade layer.
Photodynamic Treatment with Fractionated Light Decreases Production of Reactive Oxygen Species and Cytotoxicity In Vitro via Regeneration of Glutathione¶
Authors: Oberdanner Cristian Benno , Plaetzer Kristjan , Kiesslich Tobias , Krammer Barbara
Published: July 2010

Photodynamic therapy removes unwated or harmful cells by overproduction of reactive oxygen species (ROS). Fractionated light delivery in photodynamic therapy may enhance the photodynamic effect in tumor areas with insufficient blood supply by enabling the reoxygenation of the treated area. This study addresses the outcome of fractionated irradiation in an in vitro photodynamic treatment (PDT) system, where deoxygenation can be neglected. Our results show that fractionated irradiation with light/dark intervals of 45/60 s decrease ROS production and cytotoxicity of PDT. This effect can be reversed by addition of 1,3‐bis‐(2‐chlorethyl)‐1‐nitrosurea (BCNU), an inhibitor of the glutathione allow the glutathione reductase to regenerate reduced glutathione (GSH), thereby rendering cells less susceptible to ROS produced by PDT compared with continnous irradiation. Our results could be of particular clinical importance for photodynamic therapy applied to well‐oxygenated tumors.