bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

ABSTRACTA 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

ABSTRACTPhotophysical 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

ABSTRACTPhotodynamic 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

ABSTRACTA 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

ABSTRACTMelanocytes 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

ABSTRACTThe 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

ABSTRACTSteady‐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

ABSTRACTChanges 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

ABSTRACTPhotobiological 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

ABSTRACTMelanosomes 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

ABSTRACTEarlier 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

ABSTRACTThe 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

ABSTRACTPhotodynamic 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.