bluuebunny/crossref_metadata_2025 huggingface dataset:
EVALUATION OF SULFONATED ALUMINUM PHTHALOCYANINES FOR USE IN PHOTOCHEMOTHERAPY. A STUDY ON THE RELATIVE EFFICIENCIES OF PHOTOINACTIVATION
Authors: BERG KRISTIAN , BOMMER JERRY C. , MOAN JOHAN
Published: January 2008

Abstract

The cellular photosensitivity caused by aluminum phthalocyanines sulfonated to different degrees (AlPcSn) has been investigated. The phototoxic effect increased with decreasing number of sulfonate groups on the macrocycle, with the exception of AlPcS, which was less phototoxic than AlPcS2 but more phototoxic than AlPcS, and AlPcS4. The tendency of the AlPcSns to aggregate in our cellular system increased with increasing lipophilicity of the sensitizers. The aggregates had little or no photosensitizing activity. The low efficiency of cell inactivation caused by AlPcS1 can be explained by the highly aggregated state of this sensitizer in the cells. AlPcS2 and AlPcS3 induced a lower degree of cell inactivation per fluorescing quantum and per quantum absorbed by monomeric species than did AlPcS, and AlPcS,. AlPcS4 and AlPcS3 are therefore suggested to be in different intracellular locations than AlPcS2 and AlPcS1.
UROCANIC ACID ANALOGUES AND THE SUPPRESSION OF THE DELAYED TYPE HYPERSENSITIVITY RESPONSE TO Herpes simplex VIRUS
Authors: NORVAL M. , SIMPSON T. J. , BARDSHIRI E. , HOWIE S. E. M.
Published: January 2008

Abstract

Ultraviolet irradiated urocanic acid (4‐imidazoleacrylic acid) containing a mixture of cis‐and trans‐isomers has been shown previously to induce suppression of the delayed type hypersensitivity (DTH) response to Herpes simplex virus type 1 (HSV‐1) in a murine model of infection. The cis‐isomer of urocanic acid was prepared and the cis‐ and trans‐isomers of 2‐methylurocanic acid, 2‐pyrroleacrylic acid, 2‐furanacrylic acid, 2‐thiopheneacrylic acid, 3‐thiopheneacrylic acid as well as dihydrourocanic acid and histamine. Each was applied at concentrations of 1 and 50 mUg per mouse to the shaved dorsal skin and the mice were infected subcutaneously with HSV 5 h later. After 8–10 days the DTH response to the virus was measured by an ear swelling test. It was found that cis‐urocanic acid was effective in suppressing the DTH response at levels of 1 mUg per mouse or less. The cis‐ and frww‐isomers of 2‐furanacrylic acid, 2‐pyrroleacrylic acid and 2‐thiopheneacrylic acid were also effective, with the cis‐ form generally being more active than trans, and 2‐pyrroleacrylic acid being particularly potent. Cis‐ and trans‐3‐thiopheneacrylic acid, on the other hand, were only marginally immunosuppressive while neither isomer of 2‐methylurocanic acid had any suppressive ability. Dihydrourocanic acid and histamine were also shown to suppress the DTH response. Thus the structural features necessary for urocanic acid and its analogues to act as mediators of UV‐induced immunosuppression could be deduced and implications for their mechanism of action discussed.
LUX C, D AND E GENES OF THE Vibrio fischeri LUMINESCENCE OPERON CODE FOR THE REDUCTASE, TRANSFERASE, AND SYNTHETASE ENZYMES INVOLVED IN ALDEHYDE BIOSYNTHESIS
Authors: BOYLAN M. , MIYAMOTO C. , WALL L. , GRAHAM A. , MEIGHEN E.
Published: January 2008

Abstract

The lux C, D, and E genes of the Vibrio fischeri luminescence operon code for three polypeptides of 54, 33, and 42 kDa, respectively, which are required for synthesis of the aldehyde substrate for the luminescent reaction. These polypeptides have been identified in V. fischeri and V. harveyi as well as in recombinant E. colt harboring the cloned genes by specific acylation with [3H]fatty acid, showing that they are components of a fatty acid reductase system with reductase, synthetase and transferase activities. By using glycerol in the assay and/or extraction buffer and decreasing the reducing agent, the levels of the acylation of the 54 and 42 kDa polypeptides have been greatly increased. As a consequence, it was possible to demonstrate that the 54 kDa polypeptide coded by the lux C gene has reductase activity. In a subclone missing the lux E gene, the 42 kDa polypeptide was missing and the 54 kDa polypeptide could not be acylated in vitro with tetradecanoic acid (+ATP) and only to a low level in vivo indicating that the synthetase enzyme, responsible for fatty acid activation, is coded by the lux E gene. In vitro acylation with tetradecanoyl CoA of the 33 kDa polypeptide coupled with the specific cleavage of acyl‐ACP only in E. coli extracts transformed with DNA containing the lux D gene, demonstrated that the lux D gene coded for the transferase enzyme.
NEAR‐UV ACTIVATION OF ENZYMATIC CONVERSION OF 5‐HYDROXYTRYPTOPHAN TO SEROTONIN
Authors: FRAIKIN GRIGORII YA. , STRAKHOVSKAYA MARINA G. , IVANOVA EMMA V. , RUBIN ANDREW B.
Published: January 2008

Abstract— Near‐UV (337 nm) photoactivation of the 5‐hydroxytryptophan decarboxylation reaction producing serotonin has been observed. The photoactivation effect was investigated as a function of fluence rate and fluence, and pH. Photoactivation of decarboxylase activity was found to occur at nearly neutral pH values (low activity of the enzyme in the dark). The findings indicate that the effect of light is similar to a pH shift toward the acid region, which causes the enzyme conversion from the inactive to active form. Pyridoxal phosphate, the decarboxylase cofactor, in the form of an adduct absorbing at 330–340 nm, is suggested as a candidate for the role of the photoactive chromophore of decarboxylase.
DOMAIN STRUCTURE OF PHYTOCHROME FROM Avena sativa VISUALIZED BY ELECTRON MICROSCOPY*,†
Authors: JONES ALAN M. , ERICKSON HAROLD P.
Published: January 2008

Abstract— Highly purified phytochrome from A vena sativa was visualized by electron microscopy after negative staining with uranyl acetate and after rotary shadowing with platinum. The particle shape was variable in both types of specimens, but tripartite structures resembling a ‘Y’ were consistently observed. The tripartite substructure is composed of three globular domains each having a diameter of 7 to 8 nm and equally spaced in an equilateral triangle. The dimensions of the tripartite particle measured 15 nm between the centers of any two of the three particles. When phytochrome was digested with trypsin in a manner which releases the amino‐terminal globular domain from the polypeptide, the tripartite structure was lost and only small globular particles were seen. We propose that the outer particles of this tripartite structure are the amino‐terminal domains of the phytochrome dimer, and the central particle comprises the carboxyl domains of the two subunits.
EQUILIBRIUM AMONG HEMATOPORPHYRIN DERIVATIVE COMPONENTSs—II. EFFECT OF ESTERASE ACTIVITY
Authors: Bottiroli Giovanni , Croce Anna Cleta , Vaghi Patrizia
Published: January 2008

Abstract— Photofrin II is the hematoporphyrin‐derivative fraction enriched in covalently‐linked oligomers, characterized by a high degree of folding. Interaction with hydrophobic structures, such as biomolecules and cell structures, results in a modification of the equilibria among the different species, as a consequence of an unfolding effect exerted towards the electrostatic aggregates. The effect of esterase activity was evaluated, taking into account the nature suggested for the covalent linkage of the oligomers (ether and/or ester). The study was performed in Photofrin II aqueous solution by means of absorption and fluorescence spectral analysis. The results showed that the esterase is active only towards the unfold oligomers: that is, in Photofrin II solution supplemented with albumin. In these conditions, spectral analysis revealed the presence of a monomerization process, which is clearly evident during the first four hours of incubation. The monomerization effect induced by the enzyme was also proven by both equilibrium‐dialysis measurements and zinc ion complexation. Zinc ion complexes with high affinity for monomeric species, giving rise to a very distinct emission band at 580 nm. The amount of ester linkage shown in the oligomers through enzyme hydrolysis appeared to be less than might have been expected, owing to the inhibiting effect of the monomer produced on the enzyme. The results are a step toward clarifying the intracellular and intratissue turnover of the drug observed after administration.
QUENCHING OF SINGLET OXYGEN BY HUMAN PLASMA
Authors: Kanofsky Jeffrey R.
Published: January 2008

Abstract— Direct measurements of the decay of singlet oxygen phosphorescence at 1270 nm were made in human plasma diluted with various amounts of deuterium oxide. The Stern‐Volmer plot of the singlet oxygen lifetimes was linear up to 15% plasma concentration (vol/vol). Extrapolation of these measurements to 100% plasma content gave a singlet oxygen lifetime of 1.04 ± 0.03 JJLS in human plasma. Biological molecules accounted for 77% of the total singlet oxygen quenching while water accounted for 23% of the quenching. The contributions of various types of biological molecules to the total singlet oxygen quenching were calculated from their plasma concentrations and their quenching constants. Plasma proteins quenched most of the singlet oxygen. Uric acid also quenched a significant amount of singlet oxygen (12%). Tocopherols, carotenoids, ascorbic acid and bilirubin made only small contributions to the total singlet oxygen quenching (=s 4%).
TUMORIGENESIS BY A LONG WAVELENGTH UV‐A SOURCE
Authors: Sterenborg H. J. C. M. , van der Leun J. C.
Published: January 2008

Abstract— Albino hairless mice (Skh‐hrl) were exposed daily to radiation from a high‐power long wavelength UV‐A source (wavelengths longer than 340 nm). The irradiations lasted 2 h per day. The daily dose was 220 kJ/m2. Heavy scratching marks were observed in 13 out of 48 animals. However during the experiment 31 of the animals developed tumors of 1 mm or larger before any scratching was observed. The median induction time was 265 days for 1 mm tumors.
PHTHALOCYANINE FLUORESCENCE IN TUMORS DURING PDT
Authors: Moan Johan , Anholt Helle
Published: January 2008

Abstract— Athymic nude mice with human tumors transplanted to one of the hind legs were given aluminium phthalocyanine disulfonate (AlPcS2) intraperitoneally. Twenty‐four hours after the injection the mice were placed with the tumor in the sample position in a fluorescence spectrometer with modulated excitation. Exposure of the tumors to laser light at a fluence rate of50–200 mW/cm2 led to a rapid transient reduction by up to 50% of the phthalocyanine fluorescence of the tumor. After the laser irradiation the fluence rate of the fluorescence increased almost up to the initial value within a few minutes. This finding should be taken into account when optimal fluence rates and dose fractionation schemes are sought for photodynamic therapy.
GLASS and PLASTIC PHOTOLUMINESCENCE: INTERACTION WITH AQUEOUS MEDIA and CULTURED MAMMALIAN CELLS
Authors: Black Homer S. , Rodgers Michael A. J.
Published: January 2008

Abstract— Several types of glass and plastic materials were shown to exhibit intense photoluminescence when irradiated with UV. Water or phosphate buffered saline (PBS) contained within vessels of the respective materials when irradiated, also demonstrated relatively long‐lived luminescence. A significant percentage (30%) of cultured mammalian cells were killed when exposed to UV‐irradiated glass beads. The nature of the luminescence of water or PBS, or whether this or the photoluminescence of glass is directly responsible for cell toxicity, is unknown. However, we call attention to this phenomenon as a potential complicating factor in photobiological studies.
INFLUENCE OF FLUOROCARBON EMULSIONS ON PORPHYRIN‐SENSITISED OXIDATION OF HISTIDINE
Authors: Chowdhary Rubinah K. , Cundall Robert B. , Morgan Christopher G.
Published: January 2008

Abstract— The influence of fluorocarbon emulsions on the efficiency of photosensitized oxidation of histidine in solution has been studied, using haematoporphyrin and dihaematoporphyrin derivatives as sensitisers. It is shown that the fluorocarbon emulsions at low concentrations efficiently disaggregate porphyrins, and thereby enhance photosensitised oxidation. The high solubility of oxygen in fluorocarbon emulsions maintains solution oxygen tension, optimising photooxidative damage. It is suggested that fluorocarbon emulsions might find a role in photodynamic therapy, both as carriers for sensitising dyes, and also to maintain tissue oxygenation in hypoxic regions of solid tumours.
PHOTOCHEMICAL and ENZYMATIC REDOX TRANSFORMATIONS OF REDUCED FORMS OF COENZYME NADP+
Authors: Czochralska B. , Bojarska E. , Pawlicki K. , Shugar D.
Published: January 2008

Abstract— The two reduced forms of NADP+, NADPH and its dimer (NADP), on irradiation in aqueous medium at 365 nm, are converted to enzymatically active NADP+, with accompanying formation of H2O2. The rate of photooxidation of NADPH is strongly dependent on the presence of oxygen, but that of (NADP)2 is similar under aerobic and anaerobic conditions. In the presence of oxygen, but not in its absence, O2 is an intermediate in the reaction. Generation of H2O2 under anaerobic conditions, confirmed by the fact that presence of peroxidase in irradiated solutions of (NADP)2 enhances photooxidation of the latter, is ascribed to attack on water of the excited dimer. Under anaerobic conditions at pH 9.5, Fe(EDTA)2+ and Fe(CN)4 increase the rate of photooxidation of NADP dimer two‐fold. γ ‐Irradiation of (NADP)2 at pH 9.5 in the presence of N2O results in 80% conversion to enzymatically active NADP + . A mechanism for photooxidation of (NADP)2 under anaerobic conditions is suggested, and some relevant biological implications are presented.
SUBCELLULAR LOCALIZATION OF HEMATOPORPHYRIN DERIVATIVE IN BLADDER TUMOR CELLS IN CULTURE
Authors: Shulok Janine R. , Wade Margaret H. , Lin Chi‐Wei
Published: January 2008

Abstract— Mitochondria have been implicated as a primary subcellular site of porphyrin localization and photodestruction. However, other organelles including the cell membrane, lysosomes and nucleus have been shown to be damaged by hematoporphyrin derivative (HpD) photosensitized destruction as well. In this study we attempted to follow the translocation of the fluorescent components of HpD in human bladder tumor cells (MGH‐U1) in culture to determine whether specific subcellular localization occurs over time. Following a 30 min exposure to HpD the cellular fluorescence was examined immediately and 1, 2, 4, and 24 h after HpD removal using fluorescence microscopy and an interactive laser cytometer. The in vitro translocation of dye appeared to be fairly rapid with fluorescence present at the cell membrane and later (1‐2 h) within a perinuclear area of the cytoplasm. To determine whether HpD had become concentrated into a specific subcellular organelle, these fluorescence distribution patterns were compared with fluorescent marker dyes specific for mitochondria, endoplasmic reticulum and other membranous organelles. The HpD fluorescence did not appear to be as discrete as the dyes specific for mitochondria or endoplasmic reticulum but appeared similar to the diffuse cytomembrane stain. Finally, the interaction between the fluorescent components of HpD and the cellular constituents was evaluated using a “fluorescence redistribution after photobleaching” technique. The results indicated that the mean lateral diffusion for HpD in MGH‐U1 cells was 1.05 times 10−8 cm2/s, a rate closer to that of lipid diffusion (10 K) than that of protein diffusion (10−10). Under our experimental conditions, these studies indicated that upon entering the cell the fluorescent components of HpD rapidly translocated to lipophilic cytomembranous structures but did not appear to partition into a specific subcellular site.
THE PHOTOREACTION OF THE DEIONIZED FORM OF THE PURPLE MEMBRANE INVESTIGATED BY FTIR DIFFERENCE SPECTROSCOPY
Authors: Fahmy Karim , Siebert Friedrich
Published: January 2008

Abstract— Deionization of the purple membrane of Halobacterium halobium shifts the visible absorption maximum from 570 to 605 nm and inhibits proton transport. FTIR‐difference‐spectra of this blue membrane at 280 K reveal that the retinal chromophore adopts a 13‐cis and all‐trans geometry in a light dependent ratio. In contrast to purple membrane the 13‐cu isomer forms much faster in the dark. The all‐trans component produces an L‐intermediate which can be stabilized at 170 K. Spectral characteristics are similar to normal L. including comparable changes of internal aspartic acids of the opsin. However, stronger changes in the amide‐I absorption are observed. IR bands of the chromo‐protein states are assigned to retinal normal modes by the use of bacteriorhodopsin regenerated with'C‐labeled retinals.
PHOTOPHYSIOLOGY OF TURION GERMINATION IN Spirodela polyrhiza (L.) SCHLEIDEN–V. DEMONSTRATION OF A CALCIUM‐REQUIRING PHASE DURING PHYTOCHROME‐MEDIATED GERMINATION
Authors: Appenroth K.‐J. , Augsten H.
Published: January 2008

Abstract— Etiolated turions of Spirodela polyrhiza are positively photoblastic and show a phytochrome‐mediated low fiuence germination response. The far‐red light (FR) reversibility decreased with the delay of FR irradiation (lag phase 1.06 ± 0.03 days after red light irradiation; half‐maximal response 1.9 days). The action of the far‐red‐absorbing form of phytochrome (Pfr) was only realized by a germination response if exogenously applied Ca2+ was present. Calcium step‐down (from 1 mM to 0.9 μM Ca2+) and Ca2+ step‐up (from 0.9 μM to 1 mM Ca2+) experiments were carried out to determine the Ca2+‐sensitive phase. There was no time gap between the two phases determined by the step‐down and step‐up experiments but a clear coincidence of both curves. Pulse treatments (24 h) with Ca2+ (1 mM) showed the upper part of this common curve to represent the most Ca2+‐sensitive phase. The Ca2+‐sensitive phase was within the Pfr‐requiring phase. After reversion of Pfr by FR pulses there was only a negligible response to the high Ca2+‐concentration, independent of the delay between the red light (R) and FR pulses. These results are compatible with the assumption of Ca2+ acting as a second messenger of Pfr. However, the Ca2+‐insensitivity in the first 12 h after the R pulse points against this hypothesis.
INDUCTION OF LEAF UNROLLING BY PHYTOCHROME and ACETYLCHOLINE IN ETIOLATED WHEAT SEEDLINGS
Authors: Tretyn Andrzej , Kendrick Richard E.
Published: January 2008

Abstract‐Phytochrome regulates the unrolling of primary leaf sections from 8‐day‐old dark‐grown wheat (Triticum aeslivum L. cv. Arminda) seedlings. Red light (R)‐stimulated unrolling of leaf sections pretreated in 1 mM ethylene‐bis‐(β‐aminoethylether)‐N,N,N',N'‐tetraacetic acid (EGTA) if 1 mM CaCl2 was added during a 30 min treatment period including and following irradiation. Nifedipine at 1 μM (a Ca2+‐channel antagonist) applied 10 min before R prevented the R stimulation of leaf unrolling. The Ca2+‐channel agonist Bay K‐8644 (1 μM) and acetylcholine (ACh, 1 mYM) stimulated unrolling of leaf sections prewashed in EGTA in darkness, if 1 mM CaCl2 was present in the medium during a 30 min treatment period. Acetylcholine also induced leaf unrolling in the absence of Ca2+ when 100 μM NaCl was present in the medium. Apart from ACh, only carbamylcholine out of the choline derivatives tested was active in induction of leaf unrolling in the presence of 1 mM Ca2+. The ACh receptor antagonists, atropine (10 μM) AND D‐tubocurarine (10 μM), nullified the ACh‐induced Ca2+‐ and Na+‐dependent leaf unrolling, respectively. Muscarine and nicotine, agonists of ACh, at 1 μM stimulated leaf unrolling in the presence of Ca2+ and Na+, respectively. The ACh‐induced Ca2+‐dependent leaf unrolling was reduced by 1 μM Nifedipine, 10 μM Li+ and 10 μM“calmodulin” inhibitor, trifluoperazine (TFP), whereas only TFP was active in the reduction of the Na+‐dependent ACh‐induced leaf unrolling response. It is proposed that leaf unrolling of dark‐grown primary wheat leaves can be regulated by phytochrome and by activation of two different types of ACh receptors.
RESPONSE OF LIGHT‐GROWN WILD‐TYPE and LONG HYPOCOTYL MUTANT CUCUMBER PLANTS TO END‐OF‐DAY FAR‐RED LIGHT
Authors: López‐Juez E. , Buurmeijer W. F. , Heeringa G. H. , Kendrick R. E. , Wesselius J. C.
Published: January 2008

Abstract— A long‐hypocotyl mutant (lh) of cucumber (Cucumis sativus L.) has been studied which has previously been shown to lack phytochrome control of growth in de‐etiolated seedlings and thought to be modified with respect to the light‐stable type of phytochrome. We have analyzed the response of lh mutant and isogenic wild‐type (WT) plants to daily treatment with end‐of‐day far‐red light (EODFR). Only the WT responded to this treatment resulting in a large increase in internode length; an increase in petiole length; changes in leaf development (increased area, decreased thickness and reduction in indentation); redistribution of dry matter from leaf blades to stem; increased apical dominance and promotion of tendril formation. There were only small or no significant effects on chlorophyll and total carotenoid content, chlorophyll alb ratio, soluble protein levels and net photosyn‐thetic rates. The lh mutant failed to respond to EODFR treatment, and had the appearance of a shade‐avoiding plant growing in extreme shade. The lh mutant appears to completely lack the phytochrome responses attributable to the type of phytochrome that is active in shade detection. A discussion of the possible roles of the stable and labile types of phytochrome in light grown plants follows.
LIGHT‐DRIVEN MOVEMENTS IN THE SOLAR TRACKING LEAF OF Lupinus palaestinus Boiss. (Fabaceae)
Authors: Roller Dov , Shak Tamar
Published: January 2008

Abstract— The palmatcly‐compound leaf lamina of Lupinus palaestinus Boiss. tracks the sun by independent diaphototropic movements of its individual leaflets, operated by the appropriate flexing of their pulvinules. The lamina also exhibits two additional, light‐dependent nastic movements, that can operate concurrently with the diaphototropic response: (1) a nyctinastic response to light/dark transitions bv which all the leaflets fold down simultaneously and at equal rates, and which is reversed by a photonastic response to dark/light transitions by which all the leaflets unfold into a co‐planar configuration; (2) a photonastic upward folding (“cupping”), which all the leaflets exhibit simultaneously and at equal rates in response to high irradiance. thereby modulating their diaphototropic response to reduce light interception and evade over‐exposure. Although the individual leaflets can sense all these tight‐signals and respond to them independently, they do so simultaneously, so that the entire lamina responds in a co‐ordinated manner, as a unit. The photoreceptors for the two nastic responses are localized in the individual pulvinules and may or may not be the same. The photoreceptors for the diaphototropic perception are localized in the proximal segment of the lamina of the individual leaflets, adjacent to but outside the pulvinule. The separation of the sites of perception for the tropic and nastic responses allows these responses to operate concurrently. The capacity of the diaphototropic response to occur concurrently with one or the other of the two nastic responses may be accounted for by its inductive nature.
POSSIBLE ROLES OF CALCIUM and CALMODULIN IN THE LIGHT‐STIMULATION OF WALL BIOSYNTHESIS IN Phycomyces
Authors: Ruiz‐Herrera J. , Martinez‐Cadena G. , Valenzuela C. , Reyna G.
Published: January 2008

Abstract— We studied the effect of light on the activity of chitin synthetase from Phycomyces blakeslee‐anus in vitro in order to gain information on the biochemical bases of the photostimulation of sporangiophore growth. We observed that chitin synthetase activity of cell‐free extracts prepared from both sporangiophores and vegetative mycelium was increased by illumination. The process was stimulated by calcium and was not affected by protease inhibitors. Iodoacetamide inhibited chitin synthetase activation by light, or by controlled proteolysis. Calcium activated chitin synthetase by two mechanisms, one independent of and one dependent on calmodulin, the latter being sensitive to trifluoperazine. Trifluoperazine also inhibits sporangiophore growth and more noticeably phototro‐pism. We suggest that illumination increases net wall growth through two light‐sensitive calcium and calcium‐calmodulin systems one of which stimulates the normal chitin synthetase activation mechanism, and another one probably involved in vesicle displacement to the growing zone of the cell.
LIGHT CONTROL OF ELONGATION OF FILAMENT IN SUNFLOWER (Helianthus annuus L.)
Authors: Baroncelli S. , Lercari B. , Cecconi F. , Pugliesi C.
Published: January 2008

Abstract— In sunflower (Helianthus annuus L.) it has been found that continuous white‐light during the flowering stage causes loss of protandry so that filaments do not elongate. Experiments have been carried out to test the nature of the pigment involved in the photoinhibition of elongation. The results suggest that the elongation of the filament is controlled by the phytochrome system and that a low photoequilibrium is required to obtain the response. Our results do not show light control of style elongation.
EFFECT OF POLYAMINE DEPLETION ON DNA DAMAGE and REPAIR FOLLOWING UV IRRADIATION OF HeLa CELLS
Authors: Snyder Ronald D. , Sunkara Prasad S.
Published: January 2008

Abstract— Treatment of HeLa cells with the polyamine biosynthesis inhibitors, methylglyoxal bis(guanylhydrazone) (MGBG), difluoromethylornithine (DFMO) or a combination of the two, resulted in reduction in cellular polyamine levels. Analysis of UV light‐induced DNA damage and repair in these polyamine depleted cells revealed distinct differences in the repair process relative to that seen in cells possessing a normal polyamine complement. Initial yield of thymine dimers and rate of removal of these lesions from cellular DNA appeared normal in pofyamine‐depleted cells. However, depleted cells exhibited retarded sealing of DNA strand breaks resulting from cellular repair processes, reduced repair synthesis and an increased sensitivity to UV killing. Incision at damaged sites was not affected since ara‐C repair‐dependent breaks accumulated in a normal fashion. Molecular analysis of inhibited repair sites by exonuclease III and T4 DNA ligase probes suggest that the strand interruptions consist of gaps rather than ligatable nicks, consistent with an interpretation of the repair defect being at the gap‐filling stage rather than the ligation step. Observed patterns of differential polyamine depletion by DFMO and MGBG, and partial reversal of repair inhibition by polyamine supplementation, suggests that polyamine depletion per se, rather than some secondary effect of inhibitor treatment, is responsible for the inhibition of repair.
SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS–XV. ANTHRALIN and ITS OXIDATION PRODUCT 1,8‐DIHYDROXYANTHRAQUINONE
Authors: Dabestani Reza , Hall Robert D. , Sik Robert H. , Chignell Colin F.
Published: January 2008

Abstract— The photochemistry (Type I and II) of anthralin and its photo‐oxidation product 1,8‐dihydroxyanthraquinone (1,8‐DHAQ) has been studied in ethanol, acetonitrile and dimethylsulfoxide using spin‐trapping and direct detection of singlet oxygen (1O2) luminescence techniques. In ethanol, where it exists in its neutral form (AN), anthralin does not undergo either Type I or II reactions upon UV‐irradiation. In contrast, irradiation of anthralin in acetonitrile, a solvent in which anthralin is partially converted to its corresponding mono‐anion (AN), generates both superoxide and singlet oxygen. Irradiation of anthralin in dimethylsulfoxide, where the AN− form is present in substantial quantity, generates superoxide and solvent derived radicals but no detectable singlet oxygen. UV‐irradiation of 1,8‐DHAQ in ethanol and acetonitrile produces both superoxide and singlet oxygen in significant yields. In dimethylsulfoxide, on the other hand, only superoxide and solvent derived radicals are observed. The 1O2 quantum yield for AN− and 1,8‐DHAQ in acetonitrile were determined to be 0.14 and 0.88 relative to rose bengal in the same solvent. These findings suggest that the AN photosensitization occurs via Type I and II pathways, is solvent dependent and involves AN− as well as its oxidation product 1,8‐DHAQ, which is a more potent generator of both singlet oxygen and superoxide.
A PORPHYRIN‐DNA EXCIPLEX: RESONANCE RAMAN SPECTRA OF ELECTRONICALLY EXCITED Cu(TMpy‐P4) BOUND TO POLY(dA‐dT)‐POLY(dA‐dT)
Authors: Turpin P. Y. , Chinsky L. , Laigle A. , Tsuboi M. , Kincaid J. R. , Nakamoto K.
Published: January 2008

The resonance Raman spectra of water‐soluble porphyrins, Cu(TMpy‐P4) and Ni(TMpy‐P4), and their mixtures with DNA, Poly(dG‐dC)‐Poly(dG‐dC), and Poly(dA‐dT)‐Poly(dA‐dT) were measured using 426 nm pulsed laser excitation (and 556 nm for some applications). At high laser power, the solution of Cu(TMpy‐P4) mixed with DNA or Poly(dA‐dT)‐Poly(dA‐dT) exhibits new bands at 1550 and 1349 cm−1 that are not observed for Cu(TMpy‐P4) alone or for Cu(TMpy‐P4) mixed with Poly(dG‐dC)‐Poly(dG‐dC). These extra bands do not appear when the resonance Raman spectra are measured by a cw laser or by a pulsed laser with low power. Similar mixtures of M(TMpy‐P4) (where M = Ni, Zn, Co, Mn, and H2) with these nucleic acids exhibit no such bands even by high power pulsed laser excitation. We attribute the new resonance Raman bands to an electronically excited Cu(TMpy‐P4), stabilized by forming an exciplex with the A‐T site of the nucleic acid. The minimum lifetime value of such an exciplex was estimated to be on the order of 10 ps.
DEPTH PROFILES FOR PERMEATION OF WATER and OXYGEN IN VESICLES and TUBULE PHASES BY FLUORESCENCE QUENCHING STUDIES*
Authors: Sonnenschein Mark F. , Weiss Richard G.
Published: January 2008

Static and dynamic fluorescence data from three structurally related probe molecules [(1‐pyrenyl)acetic acid, 4‐(l‐pyrenyl)butanoic acid, and 12‐(l‐pyrenyl)dodecanoic acid] were employed to determine the influence of phase structure on oxygen and water permeability in small unilamellar vesicles and microtubules of l,2‐bis(tricosa‐10,12‐diynoyl)‐in‐glycero‐3‐phosphocholine (DC23PC). Since the pyrenyl units of the three reporter molecules probe environments at different depths in DC23PC bilayers, the aggregated information provides a depth profile of both small‐molecule permeability and order. The results indicate that the probe sites are somewhat more available to water molecules immediately below the chain melting transition temperature than above it: singlet lifetimes of the pyrenyl groups undergo a clear increase as the temperature is raised in the region of the transition. This observation is consistent with melted chains being able to wrap themselves more efficiently around pyrenyl units (and thereby protect them better from water molecules) than stiff chains.

The gross picture that emerges is one in which pyrenyl groups experience water and oxygen quenching via opposing concentration gradients. The concentration of oxygen is greatest near the bilayer midplane and decreases toward the aqueous interface; the concentration of water increases from the midplane to the interface.
PHOTOPHYSICS AND PHOTOCHEMISTRY OF 4‐DIHYDROPYRIDINONES
Authors: Aeby D. , Eichenberger E. , Haselbach E. , Suppan P. , Guerry P. , Neier R.
Published: January 2008

Abstract—

Dihydropyridinones (DHP) react photochemically with olefins to form cycloaddition products. The reactions proceed through the lowest excited state T1 of the DHPs, with rate constants which depend on the olefin and can approach the diffusional limit in the most favourable cases. Intra‐and inter‐molecular sensitization and quenching have been investigated, as well as spectroscopic properties such as absorption and luminescence spectra, and in particular electron energy loss spectra which have established the energy of the reactive T1, state as 295 kj mol‐1 (3.07 eV).
ANTENNA EFFECT IN LUMINESCENT LANTHANIDE CRYPTATES: A PHOTOPHYSICAL STUDY
Authors: Alpha Beatrice , Ballardini Roberto , Balzani Vincenzo , Lehn Jean‐Marie , Perathoner Siglinda , Sabbatini Nanda
Published: January 2008

Abstract—

Excited state emission and absorption decay measurements have been made on the cage‐type cryptate complexes [M bpy.bpy.bpy]n+, where Mn+= Na+, La3+, Eu3+, Gd3+ or Tb3+ and [bpy.bpy.bpy] is a tris‐bipyridine macrobicyclic cryptand. Excitation has been performed in the high intensity 1π‐π* cryptand band with maximum at about 300 nm. Experiments have been carried out in H2O or D2O solutions and at 300 and 77 K to evaluate the rate constants of radiative and nonradiative decay processes. For Mn+= Na+, La3+ and Gd3+ the lowest excited state of the cryptate is a 3ππ* level of the cryptand which decays in the microsecond time scale at room temperature in H2O solution and in the second‐millisecond time scale at 77 K in MeOH‐EtOH. For Mn+= Eu3+, the lowest excited state is the luminescent 5D0 Eu3+ level which in H2O solution is populated with 10% efficiency and decays to the ground state with rate constants 2.9 × 103 s_1 at room temperature and 1.2 × 103 s−′ at 77 K. The relatively low efficiency of 5D0 population upon 1ππ* excitation is attributed to the presence of a ligand‐to‐metal charge transfer level through which 1ππ* decays directly to the ground state. For Mn+= Tb3+ the lowest excited state is the luminescent 5D4 Tb3+ level. The process of 5D4 population upon 1ππ* excitation is ˜100% efficient, but at room temperature it is followed by a high‐efficiency, activated back energy transfer from the 5D4 Tb3+ level to the 3ππ* ligand level because of the relatively small energy gap between the two levels (1200 cm_1) and the intrinsically long lifetime of 5D4. At 77 K back energy transfer cannot take place and the 5D4 Tb3* level deactivates to the ground state with rate constant 5.9 × 102 s‐′ (H2O solution). The relevance of these results toward the optimization of Eu3+ and Tb3+ cryptates as luminescent probes is discussed.
EFFICIENCY OF THE PHOTOPROCESSES LEADING TO SINGLET OXYGEN (1δg) GENERATION BY α‐TERTHIENYL: OPTICAL ABSORPTION, OPTOACOUSTIC CALORIMETRY AND INFRARED LUMINESCENCE STUDIES*
Authors: Scaiano J. C. , Redmond R. W. , Mehta B. , Arnason J. T.
Published: January 2008

Abstract— …The triplet energy of α‐terthienyl has been determined by heavy atom‐induced optical absorption; the value of 39.7 ±1.5 kcal/mol is consistent with earlier energy transfer work. Combining this result with calorimetric data from optoacoustic calorimetry indicates that intersystem crossing occurs with at least 90% efficiency in polar and non‐polar solvents. The quantum yields for singlet oxygen formation via energy transfer from triplet α‐terthienyl have been obtained from time‐resolved measurements of its IR phosphorescence; these yields are in the 0.6‐0.8 range in non‐polar and polar (hydroxylic and non‐hydroxylic) solvents.
PHOTOCHEMICAL MODIFICATION OF lac REPRESSOR–III. MUTANT 112X86 VERSUS WILD‐TYPE REPRESSOR
Authors: Spodheim‐Maurizot Mélanie , Culard Francoise , Grebert Philippe , Maurizot Jean‐Claude , Charlier Michel
Published: January 2008

Abstract— Photodestruction of the two tryptophan (TRP) residues of the core of the wild‐type Escherichia coli lac repressor has already been used as a probe in the study of interactions of the repressor with DNA and effectors. The good correlation between phenomena occurring in the core (photodestruction of TRP residues, effectors binding) and at the headpieces (DNA specific and nonspecific binding) can be understood in terms of allosteric behavior of the protein.

In the present study, the same approach is applied to a repressor with peculiar binding properties, the 112X86 mutant. The photodestruction of TRP residues of this tight binding repressor, bearing two different amino acids as compared to the wild‐type one (Ser 61 → Leu, Pro 3 → Tyr) indicates a probably subtle (since not detected by classical spectroscopic methods) difference of structure of the entire protein and confirms the similarity between specific and non‐specific binding of this mutant repressor to DNA, observed by other methods.
A COMPARISON OF THREE PHOTOSENSITIZERS WITH RESPECT TO EFFICIENCY OF CELL IN ACTIVATION, FLUORESCENCE QUANTUM YIELD AND DNA STRAND BREAKS
Authors: Kvam Egil , Moan Johan
Published: January 2008

Abstract— Intracellular properties of three photosensitizers relevant to photodynamic cancer therapy were compared using cultured human NHIK 3025 cells. When taken up in the cells, the hydrophilic photosensitizer aluminum phthalocyanine tetra sulfonate required about 10 times more quanta of light absorbed per cell to kill 90% of the cells than did the hydrophobic dyes Photofrin II and tetra(3‐hydroxyphenyl)porphryin. In spite of this, the phthalocyanine molecule was the most efficient dye per quantum of excitation light, since the extinction coefficient of the phthalocyanine is more than 10 times higher than that of the two hydrophobic photosensitizers at therapeutic wavelengths. The two hydrophobic dyes had significantly higher fluorescence quantum yields when taken up by cells than when bound to human plasma or human serum albumin, whereas the opposite was true for the hydrophilic phthalocyanine dye—suggesting intracellular aggregation. Finally, the potential genetic toxicities of the drugs in the form of DNA strand breaks were compared. The aluminum phthalocyanine tetra sulfonate photosensitized more DNA strand breaks than did Photofrin II and tetra(3‐hydroxyphenyl)porphyrin when compared at the same level of cell survival.
EPIDERMAL CELL‐CONTRA‐INTERLEUKIN 1 INHIBITS HUMAN ACCESSORY CELL FUNCTION BY SPECIFICALLY BLOCKING INTERLEUKIN 1 ACTIVITY
Authors: Krutmann Jean , Schwarz Thomas , Kirnbauer Reinhard , URBANSKI Agatha , Luger Thomas A.
Published: January 2008

Abstract— Ultraviolet B (UVB) radiation (280–320 nm) is capable of suppressing selected cell mediated immune responses by inhibiting the function of antigen presenting/accessory cells. Human keratinocytes and carcinoma cell lines (A431) upon UVB radiation or treatment with PMA secrete a suppressor factor, which blocks IL 1 activity (hEC‐contra‐IL 1). Therefore, the capacity of this UVB‐inducable cytokine to modulate human accessory cell function was tested. Human peripheral blood mononuclear cells were stimulated with the mitogenic anti‐CD3 monoclonal antibody OKT3 and thymidine incorporation into proliferating T‐cells was measured as an index for monocyte accessory cell activity. Addition of hEC‐contra‐IL 1 which was purified by HPLC chromatography partially decreased OKT3 induced T‐cell proliferation in a dose dependent manner. Human EC‐contra‐IL 1, however, failed to inhibit blastogenesis when T‐cells depleted of accessory cells were stimulated in an accessory cell independent fashion via OKT3 attached to the bottom of microtiter plates. Recombinant human (rh) IL 1, but not rhIL 6 was able to reconstitute hEC‐contra‐IL 1 suppressed blastogenesis in a dose dependent manner. Furthermore, the combined addition of h‐EC‐contra‐IL 1 and an antibody against rhIL 6 to cultures resulted in an additive inhibitory effect which could not be observed when hEC‐contra‐IL 1 was added together with a monoclonal antibody against rhIL la/p. These studies indicate that hEC‐contra‐IL 1 is capable of suppressing human accessory cell function by specifically blocking IL 1 activity. This property of hEC‐contra‐IL 1 points to a novel mechanism by which UVB radiation may modulate human accessory cell funtion in an indirect manner.
SOLVENT DEPENDENCE OF PYRIMIDINE DIMER SPLITTING IN A COVALENTLY LINKED DIMER‐INDOLE SYSTEM
Authors: Kim Sang‐Tae , Hartman Rosemarie F. , Rose Seth D.
Published: January 2008

Abstract— –Cyclobutadipyrimidines (pyrimidine dimers) undergo splitting that is photosensitized by indole derivatives. We have prepared a compound in which a two‐carbon linker connects a dimer to an indolyl group. Indolyl fluorescence quenching indicated that the two portions of the molecule interact in the excited state. Intramolecular photosensitization of dimer splitting was remarkably solvent dependent, ranging from φspl= 0.06 in water to a high value of φspl= 0.41 in the least polar solvent mixture examined, l,4‐dioxane‐isopentane(5: 95). A derivative with a 5‐methoxy substituent on the indolyl ring behaved similarly. These results have been interpreted in terms of electron transfer from the excited indolyl group to the dimer, which would produce a charge‐separated species. The dimer anion within such a species could split or undergo back electron transfer. The possibility that back electron transfer is in the Marcus inverted region can be used to rationalize the observed solvent dependence of splitting. In the inverted region, the high driving force of a charge recombination exceeds the reorganization energy of the solvent, which is less for solvents of low polarity than those of high polarity. If this theory is applicable to the hypothetical charge‐separated species, a slower back electron transfer, and consequently higher splitting efficiencies, would be expected in solvents of lower polarity. Photolyases may have evolved in which a low polarity active site retards back transfer of an electron and thereby contributes to the efficiency of the enzymatic dimer splitting.
TUMOR CELL SPECIFIC DARK CYTOTOXICITY OF LIGHT‐EXPOSED MEROCYANINE 540: IMPLICATIONS FOR SYSTEMIC THERAPY WITHOUT LIGHT
Authors: Gulliya Kirpal S. , Pervaiz Shazib , Dowben Robert M. , Matthews James L.
Published: January 2008

Abstract— ‐Merocyanine 540 (MC540) was activated by exposure to 514 nm laser light. The light‐exposed MC540 was then mixed (in the dark) with tumor cells and normal cells to determine the antiproliferative activity. Treatment with light‐exposed MC540 resulted in 70–90% tumor cell kill from different cell lines, while 85% of the normal human mononuclear cells and 41% of the granulocyte‐macrophage colony forming cells (CFU‐GM) survived the treatment. The observed cytotoxicity of light‐exposed MC540 to the tumor cells was significantly greater (P < 0.05) than the native MC540. Results show that tumor cell specificity and cytotoxicity in the light activated dye are retained for at least 30 days. Addition of catalase and mannitol decreased the cell kill by light‐exposed compound, indicating that the observed effects may be due to reactive oxygen species. The electron micrographs of treated cells show a progression towards apoptosis in a majority of the cells. The life span of L1210 leukemia‐bearing mice treated with light‐exposed MC540 was prolonged compared to the untreated and native MC540 treated mice. High pressure liquid chromatography (HPLC) analysis of light‐exposed material shows a completely different elution profile compared to the native compound. Results presented here show that light‐exposed photoactive compounds can be used without further illumination and may have significant clinical applications. Photoactive mechanisms dependent on events other than short‐lived transient elevations in energy or singlet oxygen must be invoked to explain the reported cytotoxicity.
LIGHT‐INDUCED INFRARED LIGHT SCATTERINGSIGNAL IN THE RETINA: EFFECT OF PHOSPHODIESTERASE INHIBITORS
Authors: Stein P. J. , Caretta A.
Published: January 2008

Abstract— –Visible light changes IR light scatter through a toad retina. This signal presents three components: at low light intensity (100–400 bleached rhodopsins/rod) an early decrease in IR light scatter, of small amplitude, with time to peak of 1–6 s; at intermediate light intensity (1200‐16 000 bleached rhodopsins/rod) a slow increase in IR light scatter, with time to peak of 10–30 s; at high light intensity (50 000–160 000 bleached rhodopsins/rod) a last increase in IR light scatter, with time to peak of 1 min. Light sensitivity, amplitude and time to peak of the last two components are increased by inhibitors (3‐isobutyl‐l‐methyl‐xanthine and papaverine) of the cyclic 3'5′guanosine monophosphate phosphodiesterase.
PHOTOCHEMICAL AND PHOTOPHYSICAL STUDIES ON HUMAN LENS CONSTITUENTS
Authors: Dillon James , Wang Ren‐Hong , Atherton Stephen J.
Published: January 2008

Abstract— –The young human lens contains species (3‐hydroxy kynurenine; 3‐HK and its glucoside; 3‐HKG) which absorb most light between 300 and 400 nm. Photochemical studies have indicated that these compounds are relatively inefficient sensitizers of lens proteins. An investigation of the fluorescent properties of 3‐HKG indicate that it contains a fast deactivation pathway (ps) which would be expected to have minimal photochemical effect on the integrity of the lens. Further photophysical studies on 3‐HK indicates that it has an even faster fluorescent lifetime (< 10 ps) with a much lower quantum yield of fluorescence (0.001 vs 0.03 for 3‐HKG).

With aging, the human lens proteins undergo numerous changes including a generalized yellowing. These chromophores exhibit a higher quantum yield of fluorescence, an increase in the fluorescent lifetime by 2 orders of magnitude and the formation of two long lived transient species (µs).

These species might be expected to drastically increase the susceptibility of the human lens to ambient radiation. Based upon quantitative experimental comparisons with 3‐HK this does not seem to be the case. Further time resolved studies on old lens proteins indicate that the two transient species are interconnected in that the first transient species is the precursor to the second. The implications of this mechanism on the integrity of the lens and origin of those chromophores is discussed.
RESEARCH NOTE
Authors: Zamansky Glen B. , Chou Iih‐Nan
Published: January 2008

Abstract— Fluorescence microscopy has been utilized to investigate the effects of UV irradiation on the organization of keratin intermediate filaments in normal human epidermal keratinocytes. Sun lamp irradiation induced the condensation of keratin intermediate filaments into the perinuclear region and inhibited the reorganization of keratin filaments normally induced by Ca2+. Exposure to UVC appeared to disrupt keratin filaments similarly, whereas UVA had no discernible effect.
ANTIVIRAL ACTIVITY OF THE PHOTOACTIVE PLANT PIGMENT HYPERICIN
Authors: Lopez‐Bazzocchi I. , Hudson J. B. , Towers G. H. N.
Published: January 2008

The polycyclic compound hypericin, a known photodynamic agent, was investigated for antiviral activity in the presence and absence of light. The three viruses tested: murine cytomegalovirus; Sindbis virus; and human immunodeficiency virus type 1, were all susceptible to hypericin; but these antiviral activities were considerably enhanced, in a dose‐dependent manner, by exposure to light.
THE BIPHOTONIC PHOTOIONIZATION OF CHLORPROMAZINE DURING CONVENTIONAL FLASH PHOTOLYSIS: SPIN TRAPPING RESULTS WITH 5,5‐DIMETHYL‐1‐PYRROLINE‐N‐OXIDE
Authors: Hall Robert D. , Buettner Garry R. , Chignell Colin F.
Published: January 2008

A novel combination of conventional flash photolysis and electron spin resonance (ESR) spin‐trapping has been used to demonstrate that photoionization of chlorpromazine (CPZ), and the concomitant production of hydrated electron, occurs through a stepwise biphotonic mechanism during conventional flash photolysis at wavelengths above 290 nm. The production of hydrated electron in the flash photolysis experiment has been monitored and quantified through the use of the spin trapping agent 5,5‐dimethyl‐1‐pyrroline‐A'‐oxide (DMPO). The effects of nitrous oxide, varying concentrations of CPZ and DMPO, and a range of flash intensities on the ESR spectra of the observed spin adducts of DMPO are discussed. The use of ESR spin trapping to monitor hydrated electron yields in flash photolysis experiments has the potential to permit the use of a much wider range of flash intensities than is typically possible with conventional optical experiments. Thus, there is a greater possibility of distinguishing between monophotonic and biphotonic processes.