bluuebunny/crossref_metadata_2025_split huggingface dataset:
PHOTOPHYSICAL AND PHOTOBIOLOGICAL PROPERTIES OF DIPORPHYRIN ETHERS
Authors: KESSEL DAVID , BYRNE CHRIS J. , WARD A. DAVID 
Published: January 2008

Abstract—Spectral properties of several diporphyrin ethers were assessed in different solvents and after accumulation by leukemia L1210 cells in vitro. To facilitate studies in a variety of solvents, both tetramethylesters of the diporphyrin ethers and free acids were employed. For comparison, studies on the corresponding porphyrin monomers were also carried out. The joining of two porphyrins by an ether linkage had several consequences. We observed a blue shift in the Soret band of the ethers, but not of the corresponding simple porphyrins, in protic solvents. This phenomenon is likely related to ether aggregation under conditions which promote H‐bonding. The presence of an ether linkage was associated with enhanced fluorescence at 630–640 nm and decreased fluorescence lifetimes and yields, especially in protic solvents. The ether linkage was unaffected by intracellular enzymes, but porphyrin esters were readily hydrolyzed upon accumulation by L1210 cells. The joining of two hematoporphyrin molecules by an ether linkage promoted dye accumulation by L1210 cells. In contrast, accumulation of mesoporphyrin and protoporphyrin was thereby retarded.
PHOTODYNAMIC ACTION OF MEROCYANINE 540 IN ARTIFICIAL BILAYERS AND NATURAL MEMBRANES: ACTION SPECTRA AND QUANTUM YIELDS
Authors: SINGH RAVINDER J. , FEIX JIM B. , PINTAR THOMAS J. , GIROTTI ALBERT W. , KALYANARAMAN B. 
Published: January 2008

Abstract—The action spectra and quantum yields for singlet oxygen (1O2) generation by merocyanine 540 (MC540) in liposomes and isolated erythrocyte membranes were obtained using electron spin resonance techniques. Oxygen consumption was measured by spin label oximetry in the presence of histidine for fully‐saturated dimyristoylphosphatidylcholine vesicles, mono‐unsaturated 1‐palmitoyl‐2‐oleoylphosphatidylcholine vesicles and erythrocyte membranes. The quantum yield for the photogeneration of 1O2 by membrane‐bound MC540 in aqueous buffer was determined to be 0.065 ± 0.005, which is approx. 1/10 of the value determined for Rose Bengal under similar conditions. Using unilamellar liposomes and isolated erythrocyte membranes containing MC540 at different monomer/dimer ratios, we have observed that the action spectra of 1O2 generation closely overlap the absorption spectra of the monomeric dye in these systems. It is likely that factors which affect the monomer‐dimer equilibrium of MC540 will influence the production of 1O2. These findings have important implications for the phototherapeutic efficacy of MC540.
PHOTOOXIDATION PRODUCTS OF MEROCYANINE 540 FORMED UNDER PREACTIVATION CONDITIONS FOR TUMOR THERAPY
Authors: Franck Burchard , Schneider Udo 
Published: January 2008

Abstract—In order to gain insight into the preactivation of merocyanine 540 (M'c540) 1 for the photodynamic therapy (Gulliya et al., 1990a, Photochem. Photobiol. 52, 831–838) its photo‐oxidation was investigated. After irradiation of MC540 1 on a preparative scale three main photodegradation products were isolated with 16–20% yields. They turned out to be derivatives of benzoxazole, thiouracil and thiohydantoin with the structures 4, 5 and 6, respectively. I! may be possible that they contribute to the cytostatic and antiviral activity of preactivated MC540 1.
GENERATION OF FREE RADICALS DURING PHOTOSENSITIZATION OF HYPOCRELLIN A AND THEIR EFFECTS ON CARDIAC MEMBRANES
Authors: Zang Lun‐Yi , Misra Bibhu R. , Misra Hara P. 
Published: January 2008

Abstract—Hypocrellin A (HA), a peryloquinone derivative, has recently been isolated from a fungus Hypocrella bambusae. This lipid soluble pigment, in combination with phototherapy, has been used to treat many skin diseases including the keloids caused by scalding and burns. We have studied the effects of photosensitized HA on biomembranes using pig heart microsomes. Photosensitization of HA was found to peroxidize the membrane lipids in the cardiac microsomes. The photodamage imposed by HA depended not only on the concentration of HA but also on the time of irradiation and pH of the system. Superoxide dismutase (SOD), ascorbic acid, β‐carotene and 5,5‐dimethyl‐1‐pyrroline‐N‐oxide (DMPO) inhibited the lipid peroxidation ˜50, ˜50, ˜30 and ˜97%. respectively. Spin trapping in combination with EPR spectroscopic techniques was used to identify the reactive free radicals during the photoreaction. Formation of superoxide anion radical, (O2), was identified by the SOD‐inhibitable DMPO‐O2‐‐ EPR spectrum. Both SOD and ascorbic acid inhibited the EPR signal intensity in a dose‐dependent manner with rate constants of 6.78 × 108M−1s−1 1.82 × 104M−1 S−1 respectively. The lifetime of O2, under these conditions, was found to be 1.1 s. Photoirradiation of HA yielded a HA free radical with a g= 2.002 which was not suppressed by SOD but in the presence of reductants such as ascorbic acid and catechol the spectrum was completely suppressed. The increase of the EPR signal intensity and malondialdehyde formation with increasing pH may be due, in part, to the production of predominant *HA− species at high pH which would be more reactive with oxygen to yield O2. These results indicate that the lipid peroxidation of the cardiac membranes observed during photooxidation of HA may arise, in part, from the interaction of membrane lipids with reactive species of oxygen and HA free radical produced during the photo‐irradiation
IMPORTANCE OF TYPE I AND TYPE II MECHANISMS IN THE PHOTODYNAMIC INACTIVATION OF VIRUSES IN BLOOD WITH ALUMINUM PHTHALOCYANINE DERIVATIVES
Authors: Rywkin S. , Lenny L. , Goldstein J. , Geacintov N. E. , Margolis‐Nunno H. , Horowitz B. 
Published: January 2008

Abstract—The relative importance of type I and type II mechanisms in the photodynamic treatment of red blood cell concentrates (RBCC) to inactivate viruses was studied using aluminum phthalocyanine tetrasulfonate (AlPcS4), visible light and quenching or enhancing agents of reactive forms of oxygen. Treatment of a human RBCC with 10–13 μM AlPcS4 and 25–26 rnW/cm2 visible light resulted in the rapid and complete inactivation of added vesicular stomatitis virus (VSV). The addition of mannitol, glycerol, reduced glutathione (GSH), or superoxide dismutase (SOD), known quenching agents of type I mechanisms, had little to no effect on the rate of inactivation of VSV. Significant inhibition of VSV kill was observed on addition of tryptophan or sodium aide, known quenchers of type II mechanisms. Additionally, the rate of VSV kill was enhanced in the presence of D2O. Taken together, these results indicate a predominant role of singlet oxygen in the inactivation of VSV on photodynamic treatment of RBCC.The relative importance of type I and type II mechanisms on cellular toxicity was also evaluated. Little, if any hemoglobin release was observed on treatment of human or rabbit RBCC with 10 μM AlPcS, and 44 J/cm2 of visible light in the presence or absence of the above mentioned quenchers. The effect of the addition of quenchers on the recovery and circulatory survival of treated, autologous rabbit RBCC, labeled with 51Cr, was also assessed. As compared to a circulatory half‐life (T50) of 10–12 days for the untreated controls, RBCC treated with 30 min light exposure and 5 or 10 μM AlPcS, or 5 μM AlPc had T50 values of 5 days or less. The addition of 1 mM GSH, 1 mM mannitol, or 1 mM tryptophan prior to treatment with 30 min light exposure and 10 μM AlPcS, resulted in T50 values of 7.9–8.5, 6.5 and 8.5 days, respectively. A similar T50 enhancement was observed on addition of 0.5 mM tryptophan to RBCC prior to treatment with 10 μM AlPc and 30 min light. We conclude that virus kill in the RBCC operates principally through a type II mechanism, whereas both type I and type II mechanisms contribute to red cell cytotoxicity, as measured by circulatory survival in a rabbit model. Consequently, the specificity of virus kill on treatment of a RBCC by photodynamic processes can be enhanced through the addition of quenchers of type I reactions.
PHOTON EMISSION DURING CLEAVAGE OF FROG EGGS
Authors: Oonuki Makoto , Ryuzaki Masashi 
Published: January 2008

Abstract—Emission of light was detected from the surface of embryos of the frog, Rana japonica, during early cleavage by a photon counting and an “analog separation (integrated photons) method”. The light‐emission from an egg was more than 5.6 times 10−‐19 W at the beginning of the first cleavage.
PHOTORESPONSES OF Arabidopsis SEEDLINGS EXPRESSING AN INTRODUCED OAT phyA cDNA: PERSISTENCE OF ETIOLATED PLANT TYPE RESPONSES IN LIGHT‐GROWN PLANTS
Authors: Whitelam Garry C. , McCormac Alex C. , Boylan Margaret T. , Quail Peter H. 
Published: January 2008

Abstract—The photocontrol of hypocotyl elongation has been studied in etiolated and light‐grown wild type (WT) Arabidopsis thaliana (L. Heynh) seedlings, and in two homozygous isogenic lines that have been transformed with the oat phy A gene coding sequence under the control of the cauliflower mosaic virus (CaMV) 35S promoter. For etiolated seedlings the inhibition of hypocotyl elongation by continuous broad band far‐red light (FR) is saturated at much lower photon fluence rates in the transgenic seedlings compared with WT seedlings. Furthermore, whereas de‐etiolation of WT seedlings leads to loss of responsiveness of the hypocotyls to prolonged FR, de‐etiolated transgenic seedlings continue to show a pronounced FR‐mediated inhibition of elongation. This may reflect the persistence of a FR‐high irradiance response (HIR) mediated by the introduced oat phytochrome A. Although the hypocotyls of light‐grown transgenic seedlings display a qualitatively normal end‐of‐day FR growth promotion, such seedlings display an aberrant shade‐avoidance response to reduced red:far‐red ratio (R:FR). These results are discussed in relation to the proposal that the constitutive expression of phytochrome A leads to the persistence of photoresponse modes normally restricted to etiolated plants.
INTRACELLULAR DICHROIC ORIENTATION OF THE BLUE LIGHT‐ABSORBING PIGMENT AND THE BLUE‐ABSORPTION BAND OF THE RED‐ABSORBING FORM OF PHYTOCHROME RESPONSIBLE FOR PHOTOTROPISM OF THE FERN Adiantum PROTONEMATA
Authors: Hayami Jun , Kadota Akeo , Wada Masamitsu 
Published: January 2008

Abstract—The intracellular localization and orientation of the receptors for the blue light‐induced phototropism in the fern Adianrum protonemata, phytochrome and the blue light‐absorbing pigment, were investigated by combining the techniques of cell centrifugation and of microbeam irradiation with linearly polarized light. The phototropic response was induced in the cells even after they had been centrifuged basipetally to spin down the endoplasm from the apical region. When a polarized blue microbeam was given to a flank of the apical region of the protonema, the phototropic response after compensation of phytochrome effect by far‐red light was most effectively induced when the polarization plane was parallel to the long axis of the cell. If protonemata were pre‐irradiated with blue and far‐red light, the phototropic response was mediated through phytochrome alone. If such pre‐irradiated protonemata were similarly irradiated with a polarized blue microbeam, polarized light vibrating parallel to the cell axis was again most effective in inducing the response. These results indicate that both the blue light‐absorbing pigment and the phytochrome responsible for the blue light‐induced phototropism in Adiantum are confined to the plasma membrane and/or the ectoplasm and that the transition moments of their blue‐absorption bands are nearly parallel to the cell surface.
PHYTOCHROME REGULATION OF STEM GROWTH AND INDOLE‐3‐ACETIC ACID LEVELS IN THE lv AND Lv GENOTYPES OF Pisum
Authors: Behringer Friedrich J. , Davies Peter J. , Reid James B. 
Published: January 2008

Abstract—Phytochrome influences stem elongation and the mechanism for this is not understood. The levels of indole‐3‐acetic acid (IAA) were analyzed in an leLv genotype of Pisum sativum L. which responded to end‐of‐day far‐red light by doubling growth rate. The IAA levels in epidermal peels increased 40% after far‐red light whereas IAA levels of the entire stem tissue changed insignificantly. This increase was reversible by red light. Under light‐grown conditions, the lv mutation increases stem elongation rates by 2–3‐fold and is thought to block the transduction of a phytochrome signal. Analysis of the short‐term stem elongation kinetics of dark‐ and light‐grown Lv and lv seedlings suggests that lv blocks the action of the light‐stable form of phytochrome. The higher growth rate of lv plants was found to be associated with abnormally high epidermal IAA levels typical of far‐red treated Lv plants. End‐of‐day far‐red treatments did not substantially increase epidermal IAA levels in lv plants. These observations support the view that phytochrome regulation of stem elongation may occur in part through modulation of epidermal IAA levels. The lv mutation may result in increased internode growth in part by blocking the ability of phytochrome to decrease epidermal IAA levels.
A STUDY OF MEMBRANE‐ASSOCIATED PHYTOCHROME: HYDROPHOBICITY TEST AND NATIVE SIZE DETERMINATION
Authors: Lamparter T. , Lutterbüse P. , Schneider‐Poetsch H. A. W. , Hertel R. 
Published: January 2008

Abstract—We confirmed that after extraction in the absence of added Mg2+, a small fraction of phytochrome was associated with pelletable, hydrophobic membranes. When microsomal material of several plant species was subjected to Triton X‐114 phase partitioning, a part of phytochrome migrated into the hydrophobic Triton phase in contrast to soluble phytochrome. The amount of bound phytochrome partitioning into the Triton phase varied from 6% for oats to 30% for zucchini and 50% for mustard and maize (0.5–10% of total phytochrome). Membrane‐associated phytochrome could be solubilized by the zwitterionic detergent CHAPS and with the nonionic detergent dodecylmaltoside. Subjected to gel filtration on Superose‐6/FPLC, oat phytochrome of the CHAPS solubilized sample was eluted in three different molecular weight ranges. There was a main fraction with the molecular weight of purified phytochrome, another fraction (approximately 20%) with a higher molecular weight, and a third small fraction appearing immediately after the void volume. Gel filtration after solubilization by dodecylmaltoside resulted in two distinct fractions: the one eluted at the position of the phytochrome dimer, and the other (approximately 15%) with an apparent molecular weight of 800 kDa. Phytochrome was detected, separated and quantified by SDS‐PAGE, and western blotting with the monoclonal antibody Z‐3B1. We assume that the distinct, phytochrome positive, high molecular weight fractions contain phytochrome associated with hydrophobic protein.
PARTIAL NUCLEOTIDE SEQUENCE OF PHYTOCHROME FROM THE ZYGNEMATOPHYCEAN GREEN ALGA Mougeotia*
Authors: Winands Armin , Wagner Gottfried , Marx Stefan , Schneider‐Poetsch Hansjörg A. W. 
Published: January 2008

Abstract—Following polymerase chain reaction, a fragment of about 800 bp was amplified from genomic Mougeotia DNA using oligonucleotides directed to conserved regions of known phytochrome genes. The nucleotide sequence points to a different exon/intron structure in the neighborhood of the chromophore attachment site of this Mougeotia phytochrome gene, as compared to other phytochromes. Alignment of the derived amino acid sequence to phytochromes of higher and lower plants shows highest homology (>60%) to type II (green type) phytochrome, while Northern blot analysis of total Mougeotia RNA indicates down‐regulation of the phytochrome transcription in light. Signal pattern of hybridized genomic DNA after digestion reveals the presence of probably only one phytochrome gene in Mougeotia.
MODULATION OF INTERFERON‐GAMMA‐INDUCED HLA‐DR EXPRESSION ON THE HUMAN KERATINOCYTE CELL LINE SCC‐13 BY ULTRAVIOLET RADIATION
Authors: Khan Islam U. , Boehm Keith D. , Elmets Craig A. 
Published: January 2008

AbstractCell surface expression of major histocompatibility determinants on epidermal keratinocytes is a characteristic feature of a number of inflammatory dermatoses and in all likelihood is caused by diffusion of human leukocyte antigen (HLA)‐DR‐inducing cytokines from cells present in the dermal mononuclear cell infiltrate. Many of these same disorders respond to ultraviolet(UV) radiation phototherapy. Using the human SCC‐13 keratinocyte cell line as a model, UV radiation was found to inhibit interferon‐gamma‐induced HLA‐DR expression. Inhibition correlated closely with decreased steady‐state levels of HLA‐DR mRNA. These findings provide evidence that the therapeutic effect of UV radiation phototherapy may be mediated by its capacity to down‐regulate cytokine‐induced keratinocyte HLA‐DR expression.
EXPOSURE TO LONG WAVELENGTH ULTRAVIOLET RADIATION DECREASES PROCESSING OF LOW DENSITY LIPOPROTEIN BY CULTURED HUMAN FIBROBLASTS
Authors: Djavaheri‐Mergny M. , Maziére J. C. , Santus R. , Mora L. , Maziere C. , Auclair M. , Dubertret L. 
Published: January 2008

AbstractExposure of MRC5 human fibroblasts to UVA radiation (365 nm) resulted in a dose‐dependent decrease in low density lipoprotein (LDL) uptake and degradation by cells. Following a 25 J/cm2 irradiation dose, about 45% and 70% reduction in 125I‐LDL uptake and degradation were observed, respectively. Under the same conditions, the 14C‐sucrose uptake was also decreased to about the same extent as LDL uptake. Cell pretreatment with the antioxidants vitamin E and vitamin C did not prevent the UVA‐induced fall in LDL degradation. These results point to the possible effects of UVA radiation on receptor‐mediated and nonspecific uptake of exogenous molecules. With special regard to the alterations in receptor‐mediated processing of exogenous ligands, such a phenomenon could be of importance in UVA‐induced skin degenerative processes.
VECTORIAL ELECTRON TRANSPORT ACROSS LIPID VESICLE MEMBRANES DRIVE BY TWO PHOTOREACTIONS. II. PHOTOCHEMICAL REGENERATION OF REDUCED CYTOCHROME c BY FLAVIN TRIPLET STATE AND ETHYLENEDIAMINETETRAACETIC ACID IN THE INNER COMPARTMENT AND REDUCTION OF FERREDOXIN BY CHLOROPHYLL TRIPLET STATE IN THE OUTER COMPARTMENT
Authors: Zhao Zhan‐Gong , Tollin Gordon 
Published: January 2008

AbstractWe have attempted to mimic natural photosynthesis with regard to the photogeneration of a powerful reductant, using a negatively charged lipid bilayer vesicle system incorporating two photoreactions sensitized by a flavin analog (flavin mononucleotide [FMN]) and chlorophyll (chl) in their respective triplet states. Ethylenediamine‐tetraacetic acid (EDTA) in the inner aqueous compartment was used as a sacrificial electron donor to the FMN triplet, and ferredoxin in the outer aqueous compartment served as the final electron acceptor (mediated via triplet electron transfer chain in this multicomponent system to be elucidated. By itself, EDTA does not function as an effective donor to membran‐bound oxidized chl (chl+.), which is formed by electron transfer from triplet chl to the viologen follwed by transbilayer electron migration. This is a consequence of electrostatic repulsive interactions with the negatively charged membrane. This limitation is avoided when FMN is used as a photomediator between EDTA and chl+.. The overall reaction is dramatically increased in rate by enclosing cytochrom c together with EDTA and FMN in the inner compartment. The rate constant of the key step in the reaction, i.e. elctron transfer from reduced cytochrome c, generated via photoreduction by the FMN/EDTA system, to chl+. is increased 20‐fold over that obtained with cytochrome c alone as the elctron donor. One of the important constraints that limited the net electron transfer across the bilayer to 50% of the added cytochrome, i.e. inhibition by oxidized cytochrome c formed in the inner compartment, is avoided by the inclusion of the second photoreaction in this system, thus allowing photoreduction of all of the added ferredoxin to be achieved. This system provides a model for a photochemical energy storage process that utilizes two photorections operating in series resulting in electron flow across a lipid bilayer membrane.
THE PEROXIDATIVE METABOLISM OF TENOXICAM PRODUCES EXCITED SPECIES
Authors: Nascimento Ana Lucia T. O. , Escobar Jorge A. , Cilento Giuseppe 
Published: January 2008

AbstractThe peroxidative metabolism of the nonsteroid anti‐inflammatory oxicams generates metabolites of the type expected from a dioxetane intermediae. Therefore, electronically excited metabolites may be expected. Consistent with this possibility, both direct and sensitized light emission are observed when tenoxicam is exposed to horseradish peroxidase or when added to leukocytes, where it undergoes a myeloperoxidase‐catalyzed aerobic oxidation.The similarity between peroxidative metabolism with concomitant oxygen uptake and photodegrdation brought about by singlet oxygen addition to the substrate is pointed out. As a whole, the results strengthen the view that electronically excited species should also be considered when analyzing the effect(s) of xenobiotics.
INTERACTION OF THE PEPTIDE HORMONE ADRENOCORTICOTROPIC ACTH(l‐24), WITH A MEMBRANE MODEL SYSTEM: A FLUORESCENCE STUDY*
Authors: Moreno M. J. , Prieto M. 
Published: January 2008

AbstractThe peptide hormone adrenocorticotropin and a related peptide were studied in solution and in interaction with a model system of membranes (small unilamellar vesicles of dipalmitoylphosphatidylcholine and 17% dimyristoylphosphatidylglycerol) via fluorescence spectroscopy. In aqueous solution, intramolecular distances between the fluorescent residues R(Tyr2‐Trp9) = 9.2 Å and R(Trp9‐Tyr23) 18 Å were obtained, in agreement with molecular models.Interaction of the peptide with the negatively charged membrane is evident from the alteration of the Trp photophysical parameters (quantum yield, fluorescence spectra and anisotropy), with a partition constant between the lipidic and aqueous phase of Kp =1–2 times 103.The existence of two populations of Trp in the membrane, which are distinctly accessed by acrylamide, was concluded from the tryptophan fluorescence quenching study; the two fractions are located near the membrane interface as inferred from its fluorescence quenching by the 5‐doxylstearate and 16‐doxylstearate lipophilic quenchers. This result is further supported by energy transfer experiments to the 3‐(9‐anthroyloxyl)stearic acid and 12‐(9‐anthroyloxyl)stearic acid probes.
ACTION SPECTRA FOR THE trans TO cis PHOTOISOMERISATION OF UROCANIC ACID in vitro and IN MOUSE SKIN
Authors: Gibbs Neil K. , Norval Mary , Traynor Nicola J. , Wolf Markus , Johnson Brian E. , Crosby John 
Published: January 2008

AbstractUrocanic acid (UCA) is a major UV chromophore in the upper layers of the skin where it is found predominantly as the trans isomer. UV irradiation induces photoisomerisation of trans‐UCA to cis‐UCA which has been shown to mimic some of the immunosuppressive properties of UV exposure. We examined the wavelength dependence for trans‐UCA to cis‐UCA photoisomerisation in vitro and in mouse skin in vivo over the spectral range270–340 nm. The resulting action spectra were very similar with maximal effectiveness at300–315 nm and equal activity at 270 nm and325–330 nm, demonstrating that UVA‐II radiation (320–340nm) is efficient at UCA photoisomerisation. These action spectra differed markedly from the trans‐UCA absorption spectrum in vitro and also the reported action spectrum for UV suppression of contact hypersensitivity in mice. These findings suggest that the relationship between cis‐UCA formation in skin and UV‐induced immunosuppression may be complex.