bluuebunny/crossref_metadata_2025 huggingface dataset:
THE ROLE OF GROUND STATE COMPLEXATION IN THE ELECTRON TRANSFER QUENCHING OF METHYLENE BLUE FLUORESCENCE BY PURINE NUCLEOTIDES
Authors: DUNN DAVID A. , LIN VIVIAN H. , KOCHEVAR IRENE E.
Published: January 2008

Abstract— The effect of three purine nucleotides on the fluorescence of methylene blue in aqueous buffer has been investigated. Guanosine‐5′‐monophosphate (GMP) and xanthosine‐5′‐monophosphate cause fluorescence quenching while adenosine‐5′‐monophosphate causes a red shift in the fluorescence maximum. All three nucleotides form ground state complexes with the nucleotides as indicated by absorption spectroscopy. The fluorescence changes at nucleotide concentrations <30 mM are best described by a static mechanism involving the formation of non‐fluorescent binary and ternary complexes in competition with dimerization of the dye. Quenching of the fluorescence decay (τ= 368 ps) at high GMP concentrations (10‐100 mM) occurs at the rate of diffusion. The mechanism of fluorescence quenching may involve electron transfer within the singlet excited dye‐nucleotide complex although published values of the oxidation potentials of various purine derivatives would suggest that all three nucleotides should cause quenching. Evidence for electron transfer was obtained from flash photolysis experiments in which 100 mM GMP was found to cause the appearance of a long lived transient species absorbing in the region expected for semimethylene blue.
PHOTOOXYGENATION OF 3‐HYDROXYFLAVONE IN A 12 K O2 MATRIX
Authors: CHOU PI‐TAI , STUDER SHANNON L. , MARTINEZ MARTY L. , ORTON EDWARD , YOUNG MARK
Published: January 2008

Abstract— We present an infrared study of 3‐hydroxyflavone in 12 K Ar and O2 matrices. Although it is extremely photostable in an Ar matrix, a remarkable oxygenation reaction for 3‐hydroxyflavone takes place upon photoexcitation in an O2 matrix. The primary photoproduct is concluded to be a keto‐hydroperoxide. On further photolysis the keto‐hydroperoxide affords the photostable secondary product 2‐(benzoyloxyl)benzoic acid, as well as CO and CO2 through two independent pathways.
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.
DISCREPANCIES IN THE MEASUREMENT OF SPECTRAL SOURCES
Authors: Sayre Robert M. , Kligman Lorraine H.
Published: January 2008

Abstract— Comparison of spectroradiometric and meter measurements of a series of ultraviolet radiation sources indicates that a wide divergence between readings can occur. We found that with a xenon are filtered as a solar simulator producing UV‐A (320–400 nm) and UV‐B (290–320 nm) radiation, the meter can either over‐or underestimate the emission of the source when different cutoff filters are used. The most severe discrepancy appears with the UV‐B meter reading, although the UV‐A reading can also be problematic. Meters should be calibrated against the specific sources they will be used to measure.
ELECTRONIC ABSORPTION PROPERTIES OF SYMMETRICAL DIALKOXYANTHRACENES. LINEAR DICHROISM AND MAGNETIC CIRCULAR DICHROISM*
Authors: Brotin Thierry , Waluk Jacek , Desvergne Jean‐Pierre , Bouas‐Laurent Henri , Michl Josef
Published: January 2008

Abstract—Linear dichroism (LD) and magnetic circular dichroism (MCD) of symmetrical dialkoxy‐anthracenes and some related compounds were recorded in an attempt to elucidate electronic absorption properties and assign the nature of the lowest singlet excited state, recognized to control both the fluorescence and the photodimerization of anthracenes. The spectroscopic measurements proved that the lowest electronic transition is of the1Latype in all the compounds. The peculiar photoreactivity pattern is therefore governed by factors other than an inversion of the order of the1Laand1Lbstates and may be related to electronic density repartition on the different positions of the anthracene nucleus dictated by the position of the electron‐donating substituents.
THE PHOTOBIOLOGICAL ACTIVITY OF 5‐GERANOXYPSORALEN AND ITS PHOTOPRODUCTS
Authors: Ashwood‐Smith M. J. , Ceska O. , Warrington P. J. , Morris T. F. , Altamirano M.
Published: January 2008

Abstract— 5‐geranoxypsoralen (Bergamottin) does not photosensitize bacteria or a bacterial virus. It does, however, photosensitize mammalian cells in tissue culture. Irradiation with either black light (300–400 nm) or fluorescent ceiling lights produced at least four photobiologically active degradation products, the chemical nature of which still remains to be elucidated. Prolonged exposure to black light resulted in the formation of inactive molecule(s).
A FLAVOPROTEIN MAY MEDIATE THE BLUE LIGHT‐ACTIVATED BINDING OF GUANOSINE 5'‐TRIPHOSPHATE TO ISOLATED PLASMA MEMBRANES OFPisum sativumL.*
Authors: Warpeha Katherine M. F. , Kaufman Lon S. , Briggs Winslow R.
Published: January 2008

Abstract—A blue light photoreceptor has not been identified in higher plants. Most proposals for a blue light‐absorbing chromophore lack evidence for a direct connection between the putative chromophdre and a biological effect. Fluorescence data for the plasma membrane from etiolated buds ofPisum sativumL. suggest that we are measuring fluorescence emission of flavin species, and probably not pterin species. Fluorescence data indicate that a putative flavin exists associated with a protein or protein complex in the plasma membrane. Excitation of plasma membranes that were boiled in the presence of 0.1% sodium dodecyl sulfate and treated with blue light yields a fluorescence band with a maximum of approximately 552 nm. This fluorescence emission can be rapidly quenched by the flavin antagonists phenylacetic acid (PAA) and KI. Blue light‐enhanced binding of guanosine 5'‐[Γ‐thio]triphosphate (GTPγS) to a protein in the plasma membrane is strongly inhibited by PAA, KI, and NaN3, all quenchers of flavin excited states, indicating that a chromophore for this photoreaction may be a flavin associated with a plasma membrane protein. The above evidence is consistent with the participation of a flavin as the chromophore for the light‐induced GTP‐binding reaction in pea plasma membrane.
PHTHALOCYANINE AND NAPHTHALOCYANINE PHOTOSENSITIZED OXIDATION OF 2′‐DEOXYGUANOSINE
Authors: Ravanat J.‐L. , Berger M. , Benard F. , Langlois R. , Ouellet R. , Lier J. E. van , Cadet J.
Published: January 2008

Abstract— The photodynamic properties of the di‐and tetrasulfonated zinc and aluminium phthalocyanines and a tetrasulfonated aluminium napththalocyanine were studied using 2′‐deoxyguanosine as a DNA model compound. The major photooxidation products of this nucleoside were identified and classified according to their formation through a radical mechanism (type I) or a singlet oxygen mediated mechanism (type II). The major type I product was obtained and identified as 2,2‐diamino [(2‐deoxy‐β‐d‐erythropentofuranosyl)‐4‐amino]‐5(2H)‐oxazolone. Two major type II products were characterized as the 4R* and 4S* diastereomers of 9‐(2‐deoxy‐β‐d‐erythropentofuranosyl)‐7,8‐dihydro‐4‐hydroxy‐8‐oxoguanine. In addition a third product, also resulting from a type II photooxidation, was identified as 8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine. Quantification of these products provided a means to estimate the contribution of type I and type II pathways during the phthalocyanine and naphthalocyanine mediated photooxidation of 2′‐deoxyguanosine, confirming the major role of singlet oxygen in these processes.
KINETICS OF DYNAMIC HOLOGRAM RECORDING IN POLYMER FILMS WITH IMMOBILIZED BACTERIORHODOPSIN
Authors: Zaitsev S. Yu. , Kozhevnikov N. M. , Barmenkov Yu. O. , Lipovskaya M. Yu.
Published: January 2008

Abstract— Polymer films with immobilized photosensitive membrane protein, bacteriorhodopsin (BR), were prepared and investigated. A sensitive holographic interferometer with phase modulated optical beams was used for investigation of kinetics of dynamic hologram recording in BR polymer films. It was found that phase hologram formation consisted of two quasi‐exponential stages demonstrating existence of a diffusive process in obtained films. It was shown that the kinetics of a phase hologram recording by high intensity beams do not correlate with the exponential law. The applicability of BR polymer films as reversible photorefractive materials for dynamic holography and real‐time interferometry was discussed.
AN EXAMINATION OF THE SPECTRAL RESPONSE CHARACTERISTICS OF SEVEN ROBERTSON‐BERGER METERS AFTER LONG‐TERM FIELD USE
Authors: DeLuisi John , Wendell James , Kreiner Fred
Published: January 2008

Abstract— Seven Robertson‐Berger ultraviolet meters located at National Weather Service stations were subjected to a laboratory analysis of their spectral response functions. The analysis revealed that all spectral response functions were similar in shape in the important erythematogenic wavelength region of 300–330 nm; however, a few of the spectral response function wavelength positions varied slightly. The average of the spectral response functions was compared to Robertson‐Berger meter spectral response functions published in the 1970s. and they agreed within experimental error. This finding suggests that the shapes of the spectral response functions did not change or changed only slightly during the meters' long‐term exposure in the network. To provide insight into the problems associated with measurement of ultraviolet radiation in the UV‐B region (295–320 nm), examples of errors caused by wavelength band shifts and calibration procedures are given.
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

Cell 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

Exposure 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

We 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

The 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

The 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

Urocanic 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.
PHOTOINACTIVATION OF INFLUENZA VIRUS FUSION AND INFECTIVITY BY ROSE BENGAL
Authors: Lenard John , Vanderoef Roger
Published: January 2008

Rose bengal inactivated influenza virus upon exposure to light. Infectivity and fusion were inactivated with the same dose dependence, supporting the suggestion that the virucidal activity of photodynamic agents against enveloped viruses may be generally due to inactivation of their fusion protein(s). Concentrations required for inac‐ti vation were found to depend upon the ratio of rose bengal to virus, rather than on the nominal aqueous concentration. Fusion‐competent virosomes were inactivated similarly to intact virus particles. The HAZ portion of the influenza fusion protein HA underwent two different, apparently mutually exclusive modifications upon illumination with rose bengal: cross‐linking, and conversion to a form that moved slightly more slowly on sodium dodecyl sulfate poly‐acrylamide gel electrophoresis. Inactivation of viral fusion was inhibited by oxygen removal or addition of azide or β‐carotene, and was enhanced by D2O, consistent with partial involvement of singlet oxygen. The possibility of a second mechanism of viral photoinactivation, by direct interaction between the viral fusion protein and the pho‐toactivated dye, is also discussed.
THE EFFECT OF DIFFERENTIATION ON PHOTOSENSITIZER UPTAKE BY HL60 CELLS
Authors: Korbelik Mladen , Krosl Gorazd , Adomat Hans , Skov Kristen A.
Published: January 2008

The capability of human promyelocytic leukemia cells HL60 to be induced to differentiate to various stages along the monocytic or myelocytic pathway was exploited for investigation of the uptake of selected photo‐sensitizers by diverse types of cells of the same origin. The results showed that there was no substantial difference in photofrin uptake between noninduced HL60 cells, immature monocytes, immature neutrophils and cells differentiated along the eosinophilic pathway. In contrast, HL60 cells differentiated into macrophages (HL609) exhibited markedly increased photofrin uptake, which was further enhanced by their pretreatment with bacterial lipopolysaccharide. Similar results were obtained with other photosensitizers tested: di‐and tetrasulfonated aluminum phthalocyanines (AIPcS2 and AIPcS4), tetrasulfonated zinc phthalocyanine (ZnPcS4), tetraphenylporphine tetrasulfonate (TPPS4) and benzoporphyrin derivative monoacid (BPD). Despite marked differences in the state of self‐aggregation and other chemical properties of these compounds, the degree of their preferential uptake by HL60 PH cells showed very little variation. In a typical experiment, the uptake of these photosensitizers by HL60 PH cells was four to five times higher than the uptake by noninduced HL60 cells. In addition to the fluorometric assay employed in most of the experiments, cellular concentration of AlPcS4 was determined by measurement of elementary aluminum using atomic absorption spectroscopy.
CHLOROPHYLL a AGGREGATES IN HYDROCARBON SOLUTION, A PICOSECOND SPECTROSCOPY AND MOLECULAR MODELING STUDY
Authors: Helenius V. M. , Hynninen P. H. , Korppi‐Tommola J. E. I.
Published: January 2008

Abstract Chlorophyll a aggregates in 3‐methylpentane solution have been studied by using picosecond absorption and fluorescence spectroscopy and molecular modeling. Chlorophyll a aggregates give rise to reversible temperature changes in the absorption and fluorescence spectra. Time‐dependent anisotropies were used to estimate rotational correlation times of the aggregates. These were indicative of the sizes of the aggregates. The rotational diffusion of the monomer and the two identified aggregates was hydrodynamic over the viscosity range studied (0.29–1.8 cP). Molecular mechanics calculations were used to predict the minimum energy structures of several chlorophyll a dimers suggested earlier in the literature. These structures were used to estimate exciton splitting of the Qy,0–0 transition and compared to the experimentally observed spectral shifts.
PHOTOSENSORY TRANSDUCTION IN CILIATES. III. THE TEMPORAL RELATION BETWEEN MEMBRANE POTENTIALS AND PHOTOMOTILE RESPONSES IN Blepharisma japonic urn
Authors: Fabczak Stanislaw , Fabczak Hanna , Song Pill‐Soon
Published: January 2008

Abstract— Blepharisma japonicum exhibits a step‐up photophobic response when subjected to an increase in light stimulus intensity. This response is characterized by the stop reaction after a period of delay followed by backward swimming (lateral rotation). The latency of the stop response decreased and duration of the lateral rotation increased as the intensity of light stimuli was raised. A step‐increase in light intensity elicited a graded membrane depolarization (photic receptor potential), as measured by intracellular microelectrode. When the amplitude of receptor potential exceeded a threshold depolarization for membrane excitation (15–25 mV), an all‐or‐none action potential of 50–65 mV in amplitude was evoked which also occurred with some latency. Light stimuli of higher intensity (suprathreshold) elicited action potential which was followed by a membrane after‐depolarization. Increasing the intensity of stimuli caused generation of an action potential with shorter lag period and prolonged after‐depolarization. The action spectra for the latency of stop reaction, receptor potential amplitude and cell photoresponsiveness showed maxima at 460, 530 and 580 nm. The analysis of temporal relationships between the electrophysiological responses and the motile events showed that latency of an action potential, induced by the receptor potential, correlates well with the latency of a cell stop response. Also the duration of membrane after‐depolarization resembled the time period of the cell's backward swimming (cell rotation). The data obtained indicate that the primary reaction initiated by light absorption in the photoreceptor pigment (blepharismin) is converted into the observed electrical potential changes, which in turn results in the photomotile response of Blepharisma cells.
In vivo REPAIR OF CYTOSINE HYDRATES IN DNA OF CULTURED HUMAN LYMPHOBLASTS
Authors: Weiss Randi B. , Gallagher Patricia E.
Published: January 2008

Abstract— Ultraviolet irradiation of DNA in vitro results in the production of a wide variety of pyrimidine base alterations, including cytosine hydrates. Enzymes that initiate the repair of monomeric pyrimidine damage have been identified in both bacterial and mammalian systems; however, the in vivo formation and repair of cytosine photohydrates has not been demonstrated in cellular DNA. Using Escherichia coli endonuclease III as a damage‐specific probe, we have shown that ring‐saturated pyrimidines are formed in cultured human cells by irradiation with broadspectrum UV light. In addition, these types of base damage are removed from the DNA of human lymphoblasts within 5 h following the irradiation. Analysis of the action spectrum for the formation of cytosine hydrates in DNA reveals that these photoproducts are formed most efficiently by irradiation in the range of 255–265 nm light, coinciding with the wavelengths that are maximally absorbed by the DNA bases.
ACTION SPECTRUM FOR SUBLIMINAL LIGHT CONTROL OF ADAPTATION IN Phycomyces PHOTOTROPISM
Authors: Chen Xi‐yin , Xiong Yu‐qing , Lipson Edward D.
Published: January 2008

Abstract ‐Adaptation processes enable phototropism and other blue light responses of Phycomyces to operate over a 10‐decade range of Ruencc rate. Phototropic latency, used routinely to monitor the kinetics of sensitivity recovery after a step down in fluence rate, can be shortened by application of dim light for 35 min during the early part of the latency period. This light is termed subliminal, because it does not elicit phototropism under these experimental conditions; rather, it exerts its influence on the underlying adaptation kinetics. Fluence rate‐response data for this latency reduction, obtained at 17 wavelengths of subliminal light from 347 to 742 nm, showed a variety of shapes that could be fit by zero, one, or two sigmoidal components, plus a constant term. At most wavelengths, the fluence‐rate threshold for latency reduction by subliminal light tended to be well below the absolute threshold for phototropism, indicating that this effect is highly sensitive. An action spectrum for the sensitivity of the subliminal light effect, derived from the fluence rate‐response curves, shows major peaks around 400 and 500 nm and a broad band from 570 to 670 nm, followed by a steep absorption edge. The sensitivity in the near ultraviolet region is relatively very low. The magnitude of the latency reduction also depends strongly on wavelength with a maximum at about 450 nm. The Huence‐rate response data and the action spectrum–which is markedly different from that for phototropism and other blue‐light responses of Phycornyces –indicate the participation of multiple pigments, or pigment states, in the photocontrol of adaptation.
SITE‐TO‐SITE DIFFUSION IN PROTEINS AS OBSERVED BY ENERGY TRANSFER AND FREQUENCY‐DOMAIN FLUOROMETRY *
Authors: Lakowicz Joseph R. , Gryczynski Ignacy , Kuśba Józef , Wiczk Wieslaw , Szmacinski Henryk , Johnson Michael L.
Published: January 2008

Abstract We report measurements of the site‐to‐site diffusion coefficients in proteins and model compounds, which were measured using time‐dependent energy transfer and frequency‐domain fluorometry. The possibility of measuring these diffusion coefficients were shown from simulations, which demonstrate that donor (D)‐to‐acceptor (A) diffusion alters the donor frequency response, and that this effect is observable in the presence of a distribution of donor‐to‐acceptor distances. For decay times typical of tryptophan fluorescence, the simulations indicate that D‐A diffusion coefficients can be measured ranging from −7 to −5 cm2/s. This possibility was verified by studies of a methylenechain linked D‐A pair in solutions of varying viscosity. The D‐A diffusion was also measured for two labeled peptides and two proteins, melittin and troponin I. In most cases we used global analysis of data sets obtained with varying amounts of collisional quenchers to vary the donor decay time. Unfolding of troponin I results in more rapid D‐A diffusion, whereas for melittin more rapid diffusion was observed in the α‐helical state but over a limited range of distances.
MEASUREMENT OF THE RATE OF UPTAKE AND SUBCELLULAR LOCALIZATION OF PORPHYRINS IN CELLS USING FLUORESCENCE DIGITAL IMAGING MICROSCOPY
Authors: Georgiou G. N. , Ahmet M. T. , Houlton A. , Silver J. , Cherry R. J.
Published: January 2008

Abstract A fluorescence imaging system incorporating a cooled slow‐scan charge‐coupled device camera was used to study the rate of uptake and subcellular localization of porphyrins in living cells. Measurements were carried out on human dermal fibroblasts (D532) using two different porphyrins meso‐tetra(4‐N‐methylpyridyl)porphine (TMPP) and meso‐tetra(4‐N‐hexylpyridyl)porphine (THPP). It was observed that TMPP was rapidly taken up by cells and principally located in the nucleus. The THPP, on the other hand, internalized more slowly and exhibited a particulate distribution in the cytoplasm.
ArF EXCIMER LASER‐INDUCED BUBBLE FORMATION DURING IRRADIATION OF NaCl SOLUTIONS
Authors: Turovets Igor , Palanker Daniel , Lewis Aaron
Published: January 2008

Abstract During application of the 193 nm excimer laser to vitreoretinal surgery, very deep cutting of the retina of about 100 μm/pulse was detected at the energy fluence in the range of 0.25–0.35 J/cm2/pulse. At the surface of the ablating tip insoluble bubbles were observed during the irradiation. In this paper we study production of these bubbles in aqueous solutions of sodium chloride. The yield of gaseous photoproducts was measured as a function of NaCl concentration and energy fluence. At concentrations of 100 g/L powerful water vapor bubbles and shock waves were observed. A mechanism of soft tissue cutting by the 193 nm laser in highly absorbing liquid media is suggested that explains the features of vitreoretinal ablation with this system: (1) the high cutting depth when the tip touches the tissue and (2) the absence of cutting when the tip is not in contact with the tissue. The advantages of the ArF laser for microsurgery of internal organs are discussed.
PHOTOLUMINESCENT PROPERTIES OF OCTADECYLRHODAMINE B IN WATER, IN ALCOHOLS AND IN MIXED WATER‐ALCOHOL SOLUTIONS
Authors: Nakashima Kenichi , Fujimoto Yoshinori
Published: January 2008

Abstract Fluorescence, excitation and absorption spectra of octadecylrhodamine B (ORB) have been observed in solutions of water, methanol, ethanol and other simple alcohols. A remarkable increase in the ORB fluorescence intensity occurs when the probe is transferred from water to the alcohols. This effect is ascribed to the release of ORB fluorescent monomers from nonfluorescent multimers, which exist predominantly in water. The dependence of the fluorescence intensity on the composition of water‐alcohol binary solvent systems shows that hydrophobic interactions play an important role in the monomer = multimer equilibrium of ORB in these solutions. The fluorescence lifetimes of ORB in the alcohols are also reported.
ISOLATION OF MUTANTS OF THE FUNGUS Cercospora nicotianae ALTERED IN THEIR RESPONSE TO SINGLET‐OXYGEN‐GENERATING PHOTOSENSITIZERS
Authors: Jenns Anne E. , Scott Donna L. , Bowden Edmond F. , Daub Margaret E.
Published: January 2008

Fungi in the genus Cercospora produce a singlet‐oxygen‐generating photosensitizing toxin cercosporin, which plays an important role in the ability of these fungi to parasitize plants. Previous studies demonstrated that resistance to cercosporin was associated with the ability of the fungus to reduce and detoxify cercosporin transiently. In order to characterize the mechanism of cercosporin resistance further, two types of mutants were isolated. One set of mutants was selected directly for sensitivity to cercosporin. Six cercosporin‐sensitive mutants were isolated. Five of the mutants were totally inhibited by cercosporin as well as by five other photosensitizers, methylene blue, toluidine blue, eosin Y, rose bengal and hematoporphyrin. These five mutants were also deficient in cercosporin‐reducing ability. The sixth cercosporin‐sensitive mutant was only partially inhibited by cercosporin. This mutant was unaltered in cercosporin‐reducing ability and in its response to the other photosensitizers. In order to test hypotheses concerning the mechanism of cercosporin reduction, a second set of mutants was selected for general deficiency in cell surface‐reducing capability by screening for the inability to reduce two tetrazolium dyes (p‐tolyltetrazolium red and 2,3,5‐triphenyltetrazolium chloride) of similar redox potential to cercosporin. Dye‐reduction‐deficient mutants were unaltered in their resistance to cercosporin and in cercosporin‐reducing ability. We conclude that cercosporin resistance of these fungi is strongly correlated with the ability to reduce cercosporin. However, cercosporin‐reducing ability is separable from the general ability to reduce external electron acceptors.
LOCAL NEUROTOXICITY OF HEMATOPORPHYRIN DERIVATIVE FOLLOWING INTRACEREBRAL INJECTION
Authors: Noske David P. , Kamphorst Wouter , Wolbers John G. , Sterenborg Henricus J. C. M.
Published: January 2008

The present study reports on toxicity of hematoporphyrin derivative (HpD) for normal brain tissue in vivo without the addition of light. Hematoporphyrin derivative was injected by slow infusion in rat brains. Histological examination was carried out for intervals after HpD administration, ranging from 0 h to 15 days. Ultrastructural changes were examinated with transmission electron microscopy. The extent of the necrosis was determined for different HpD concentrations and compared with control animals infused with 0.9% saline. Leukocytic infiltration was observed at day 5. Transmission electron microscopy showed that nuclei of neurons were completely disintegrated 4 h after HpD administration. Furthermore disruption of myelin sheaths was observed. The extent of the necrosis decreased with lower HpD doses. Injection of 2 μg HpD in a volume of 4 μL (0.5 mg/mL) resulted in a virtually equal extension of the tissue damage, as compared to the mechanical damage in the control animals caused by the infusion procedure.
ON THE SOURCE OF THE OSCILLATIONS OBSERVED DURING in vivo ZINC PHTHALOCYANINE FLUORESCENCE PHARMACOKINETIC MEASUREMENTS IN MICE
Authors: Dickson Eva F. Gudgin , Holmes Hugh , Jori Giulio , Kennedy James C. , Nadeau Pierre , Pottier Roy H. , Rossi Francesca , Russell David A. , Weagle Glenn E.
Published: January 2008

Surface‐detected fluorescence spectroscopy can be used to monitor the pharmacokinetics of uptake and clearance of red‐absorbing fluorophores such as zinc(II) phthalocyanine (ZnPc) in vivo. When this technique is applied to mice that have been fed on a normal chlorophyll‐based diet, and particularly when measurements are performed in the abdominal region, oscillations are sometimes observed superimposed on the pharmacokinetic curve of the ZnPc. An oscillatory signal has also been observed arising from the abdominal region of control mice fed a normal diet but not injected with the ZnPc photosensitizer; this oscillatory component to the signal is reduced when mice are fed a chlorophyll‐free diet. The oscillatory signal component has been attributed to fluorescence arising from chlorophyll derivatives (pheophorbide/pheophytin) contained in the rodent food, whose concentration in the measured abdominal region changes substantially with time, presumably due to digestive processes. Thus it is important to be aware of the possibility of such artifactual contributions to in vivo fluorescence pharmacokinetic measurements.