bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE INWARD H+ PATHWAY IN BACTERIORHODOPSIN: THE ROLE OF M412 AND P(N)560 INTERMEDIATES
Authors: Danshina S. V. , Drachev L. A. , Kaulen A. D. , Skulachev V. P. 
Published: January 2008

AbstractIn purple bacteriorhodopsin sheets adsorbed onto the phospholipid‐impregnated collodion film, electrogenic stages are identified correlating with decays of the M and N(P)‐type intermediates. It is concluded that both M N and N bR transitions are electrogenic.The M decay is shown to be of a complex kinetics. In purple sheets, the lower the light intensity, the higher the rate of “slow M” decay. Such a dependence, which is absent from monomeric bacteriorhodopsin in proteoliposomes and from Triton X‐100‐solubilized protein, may be explained by the inhibiting effect of a light‐induced conformation change in a bacteriorhodopsin molecule upon the M decay in some other bacteriorhodopsin molecules within the same sheet.The light intensity‐independent “slow M” decay in solubilized bacteriorhodopsin is shown to correlate with the decay of the N intermediate and H+ uptake after the flash. In contrast to “fast M”, “slow M” is pH dependent, closely resembling in this respect the N intermediate. It is suggested that there is a fast light‐independent equilibration between M and N so that “slow M” represents the portion of the M pool that monitors the N concentration. The M N equilibrium is assumed to be involved in the effect of the light‐induced electric field on the M decay. No direct effect of light on the equilibrium was found.
EFFECT OF PSORALEN + ULTRAVIOLET‐A ON THE CHEMOTACTIC ACTIVITY OF POLYMORPHONUCLEAR NEUTROPHILS TOWARDS ANAPHYLATOXIN C5a DES ARG
Authors: Esaki Kenji , Mizuno Nobuyuki 
Published: January 2008

AbstractIt was shown that psoralen + UV‐A inhibits the chemotactic activity of polymorphonuclear neutrophils towards anaphylatoxin C5a des Arg. This reaction required oxygen and there is a high possibility that the active oxygen species was in a singlet state. Oxygen did not act directly on C5a des Arg, but rather produced oxidized psoralen which inhibited C5a des Arg activity. The effect was dependent on the concentration and types of psoralen and on the UV‐A dose. Among the psoralens, the inhibitory effect of 4,5′,8‐trimethylpsoralen was the strongest, followed by 8‐methoxypsoralen and 3‐carbethoxypsoralen and finally 4,4′,6‐trimethylangelicin. Psoralen + UV‐A failed to inhibit the chemotactic activity towards chemotactants other than anaphylatoxin C5a such as casein, the cultured filtrate of E. coli, platelet‐activating factor, leukotriene B4, 5‐hydroxy‐6,8,11,14‐eicosatetraenoic acid and 12‐L‐hydroxy‐5,8,10,14‐eicosatetraenoic acid.
QUANTUM YIELDS AND KINETICS OF THE PHOTOBLEACHING OF HEMATOPORPHYRIN, PHOTOFRIN II, TETRA(4‐SULFONATOPHENYL)‐PORPHINE AND UROPORPHYRIN
Authors: Spikes John D. 
Published: January 2008

AbstractPorphyrins used as sensitizers for the photodynamic therapy (PDT) of tumors are progressively destroyed (photobleached) during illumination. If the porphyrin bleaches too rapidly, tumor destruction will not be complete. However, with appropriate sensitizer dosages and bleaching rates, irreversible photodynamic injury to the normal tissues surrounding the tumor, which retain less sensitizer, may be significantly decreased. This paper surveys the quantum yields and kinetics of the photobleaching of four porphyrins: hematoporphyrin (HP), Photofrin II (PF II), tetra(4‐sulfonatophenyOporphine (TSPP) and uroporphyrin I (URO). The initial quantum yields of photobleaching, as measured in pH 7.4 phosphate buffer in air, were: 4.7 × 10‐5, 5.4 × 10‐5, 9.8 × 10‐5, and 2.8 × 10‐5for HP, PF II, TSPP and URO respectively; thus, the rates of photobleaching are rather slow. Low oxygen concentration (2 μM) significantly reduced the photobleaching yields. However, D2O increased the yields only slightly, and the singlet oxygen quencher, azide, had no effect, even at 0.1M.Photosensitizing porphyrins in body fluids, cells and tissues may be closely associated with various photooxidizable molecules and electron acceptors and donors. Therefore, selected model compounds in these categories were examined for their effects on porphyrin photobleaching. A number inhibited and/or accelerated photobleaching, depending on the compound, the porphyrin and the reaction conditions. For example, 1.0 mMfurfuryl alcohol increased the photobleaching yields of HP and URO more than 5‐fold, with little effect on PF II or TSPP. In contrast, the electron acceptor, methyl viologen, increased the photobleaching yield of TSPP more than 10‐fold, with little accelerating effect on the other porphyrins. These results suggest that the mechanism(s) of the photobleaching of porphyrin photosensitizers in cells and tissues during PDT may be complex.
COMPARATIVE STUDY OF ERYTHEMA RESPONSE TO UVA RADIATION IN GUINEA PIGS and HUMANS*,†
Authors: Whitman Gail B. , Leach Eileen Enny , DeLeo Vincent A. , Fleiss Joseph L. , Conetta Barbara , Harber Leonard C. 
Published: January 2008

Abstract— Cutaneous erythema resulting from UVB radiation has been extensively studied in both humans and experimental animals; however, although there have been several investigations defining UVA erythema in humans, there have been no comprehensive reports using an animal model. Accordingly, studies were designed to assess UVA erythema in terms of time of onset; time of maximum reaction; and fluence‐response relationships in albino guinea pigs and to compare these with similar studies in humans.Two high intensity Hg vapor lamps containing iron and gallium halides were used as UVA light sources. Both have sufficient fiuence rates (190 to 260 W m−2) so as to allow convenient exposure times for delivery of UVA erythemogenic fluences. UVA fluences of 20 times 104, 40 times 104 and 60 times 104 J m−2 were administered to 58 humans and 51 Hartley‐strain albino guinea pigs.Data obtained in humans indicate that UVA erythema develops immediately after irradiance with a maximum erythema peak occurring in 6 to 12 h and markedly diminishing by 24 h. The minimal fiuence required to elicit erythema responses in Type I and Type II individuals was found to be approximately 40 times 104 J m−2 of UVA when observed at 6 h, a fiuence about 1000 times greater than that used to elicit UVB erythema.Studies in 51 guinea pigs demonstrated erythema immediately after irradiance, with a peak between 8 to 12 h, and a marked decrease in 48 h. The fiuence of UVA required to elicit erythema was similar to that required in humans. The two different light sources provided comparable data per unit exposure and were essentially similar to a Xe lamp.These data from both humans and guinea pigs strongly support the concept that UVA erythema can be assayed in guinea pigs and correlated with humans.
THE EFFECT OF DEUTERIUM OXIDE ON THE FLUORESCENCE AND PHOTOTRANSFORMATION OF 124 kDALTON PHYTOCHROME*
Authors: Moon Doo‐Khil , Jeen Gwang‐Soo , Song Pill‐Soon 
Published: January 2008

Abstract— To probe the nature of primary photoprocess and the mechanism of the phototransformation of undegraded 124 kDa oat phytochrome, solvent deuterium isotope effects on the fluorescence and phototransformation of phytochrome have been investigated. The fluorescence intensity and lifetime of phytochrome (Pr form) are greater in D20‐buffer than in H2O‐buffer, suggesting a possible involvement of proton transfer in the primary photoprocess of phytochrome. Although the photostationary equilibrium (Pr to Pfr ratio) was not altered by deuterium oxide, in contrast to degraded phytochrome, the rate constants of both transformations, Pr→ Pfr and Pfr→ Pr were enhanced by up to 24%. The Pr to Pfr phototransformation of degraded phytochrome, however, was retarded by about the same percentage in D2O. These opposite effects of D2O with degraded and undegraded phytochromes underscore the fact that the Pr form from the former reverts to the Pr form in the dark, apparently catalyzed by deuterated general and/or conjugate acidic group(s). With the degraded phytochrome the deuterium oxide enhancement of the rate of dark reversion was approximately 2‐fold (Sarkar and Song, 1981).Both the fluorescence intensity and the rates of phototransformation of phytochrome were enhanced in D2O with successive photocyclings (Pr→ Pfr→ Pr→ Pfr→ Pr etc.) with alternating red and far‐red irradiation. It has been proposed that successive photocycling of phytochrome in D2O results in proton‐deuteron exchange in the partially exposed Ptr chromophore and/or its surrounding amino acid residues.
THE PHOTOMOVEMENT OF Caenorhabditis elegans, A NEMATODE WHICH LACKS OCELLI. PROOF THAT THE RESPONSE IS TO LIGHT NOT RADIANT HEATING
Authors: Burr A. H. 
Published: January 2008

Abstract— Caenorhabditis elegans adults were tested at constant temperature with 10 s periods of monochromatic light alternated with 20 s dark periods. Stimuli at effective intensities and wavelengths caused an increase in the frequency of ecclitic (phobic, avoidance) responses, which was measured as an increase in the probability of a temporary reversal in direction of movement. For monochromatic stimuli ranging from 420 to 680 nm at a constant 56 picoeinsteins s‐1 cm‐2, only those at520–600 nm elicited significant responses. At 540 nm the threshold fluence rate was approximately 30 pE s‐1 cm‐2. At saturating intensities the mean reversal probability was increased to 0.20 in 10 s from a background level of 0.12. approximately.Because C. elegans lacks ocelli and is very sensitive to temperature, possible sources of radiant heating were considered in detail, including (a) infrared present in the stimuli, (b) absorption of light by the arena, and (c) absorption of light by a nematode pigment. All possible sources were found to cause a negligible temperature rise, on the order of or less than the natural temperature fluctuations inside the worm, 1.5 times 10‐6°C. A 2 times 10‐4°C temperature rise produced by a 1230 nm infrared stimulus had no significant effect on reversal frequency. It was concluded that the response to illumination must have been to light, and not to temperature changes.Large, + or ‐ 2 °C changes from the acclimation temperature caused significant increases in the background frequency of ecclitic responses (a thermoecclisis or thermoklinokinesis). However, neither the threshold nor the saturation level of light‐induced responses was affected by the ± 2°C changes.
DARK INTERACTION AND OXYGEN DEPENDENT PHOTOBINDING BETWEEN AN AROMATIC TETRAPEPTIDE AND DNA MODIFIED BY 5‐ METHOXYPSORALEN MONOADDUCTS
Authors: Morliere P. , Cremer J. , Toulme J. J. , Santus R. , Dubertret L. 
Published: January 2008

AbstractThe binding of the tetrapeptide lysyl‐tryptophyl‐glycyl‐lysinet‐butyl ester to native DNA and DNA photochemically modified by 5‐methoxypsoralen has been investigated by fluorescence spectroscopy. The peptide exhibits a higher affinity for the modified DNA than for the undamaged DNA. This is due to the presence of strong stacking sites in the vicinity of 5‐methoxypsoralen monoadducts. Upon irradiation at 365 nm of the peptide‐modified DNA complexes, a cross‐linking of the peptide to the nucleic acid is observed. This photochemical addition requires the presence of oxygen and involves, in part, singlet oxygen.
PHOTOCHEMISTRY OF THE BOTANICAL PHOTOTOXIN, α‐TERTHIENYL AND SOME RELATED COMPOUNDS*
Authors: Evans C. , Weir D. , Scaiano J. C. , Eachern A. Mac , Arnason J. T. , Morand P. , Hollebone B. , Leitch L. C. , Philogegne B. J. R. 
Published: January 2008

AbstractThe photochemistry of α‐terthienyl (αT) and its mono‐ and dodo derivatives has been examined using nanosecond laser Hash photolysis techniques. The triplet states of these intermediates have been characterized, and show strong triplet‐triplet absorptions with maxima in the 450 to 490 nm region. The triplet lifetimes are normally reduced by efficient triplet‐triplet annihilation and self‐quenching both of which approach diffusion control. Triplet lifetimes in methanol obtained by extrapolation to zero laser dose and zero concentration are 30, 12.5 and 9.4 μs for αT and its mono‐ and dodo derivatives, respectively; the effect of iodo substitution on the lifetimes is attributed to heavy atom effects. The triplet states are efficiently quenched by oxygen and the electron acceptor methyl viologen, while amines tire very poor triplet quenchers. The iodo derivatives are photolabile. undergoing C‐I bond cleavage from the singlet state, a process that was studied in benzene solvent, where the complex between iodine atoms and benzene can be readily characterized.Modification of αT by replacement of the central thiophene ring by an aromatic ring (i.e. DTB) causes drastic changes in the triplet and singlet state kinetic and spectroscopic characteristics.
A MICROSPECTROFLUOROMETRIC STUDY OF PORPHYRIN‐PHOTOSENSITIZED SINGLE LIVING CELLS— I. MEMBRANE ALTERATIONS
Authors: Reyftmann J. P. , Kohen E. , Morliere P. , Santus R. , Kohen C. , Mangel W. F. , Dubertret L. , Hirschberg J. G. 
Published: January 2008

AbstractMicrospectrofluorometry on single living cells reveals that the primary effects of porphyrin‐photosensitization on membranes results in the production of fluorescent lipofuscin‐like pigments implying important lipid photoperoxidation. These fluorescent products (max450 nm) can also be formed in the dark after the irradiation of the cell. Their formation is abolished not only by crocetin and Tigason, two long‐chain polyenes, but also by chloroquine. The latter, although a lysosomotropic drug, cannot inhibit the photosensitized permeation of lysosomal membranes which occurs at the beginning of the irradiation as shown by the splitting of fluorogenic substrates by lysosomal proteinases or by β‐galactosidase when added before or after irradiation.
FURTHER STUDIES ON THE ANTIVIRAL ACTIVITY OF HARMINE, A PHOTOACTIVE β‐CARBOLINE ALKALOID
Authors: Hudson J. B. , Graham E. A. , Fong R. , Hudson L. L. , Towers G. H. N. 
Published: January 2008

AbstractThe UV‐A mediated antiviral effect of harmine was investigated using murine cytomegalovirus (MCMV) as the target. Virus, which had been inactivated by harmine + UVA, was used to infect cultured mouse cells, and various stages in the viral replication cycle were examined. No viral protein synthesis or RNA synthesis (as measured by polyacrylamide gel electrophoresis or DNA‐RNA hybridization) could be detected, and the viral DNA did not replicate (measured by DNA‐DNA hybridization). In contrast virus which had been treated with harmine in the dark promoted a complete growth cycle in mouse cells.An attempt was made to identify the primary target of harmine + UVA activity by examining the bacteriophages T4 and M13, which unlike MCMV do not possess membranes. Both bacteriophages were sensitive, but the single‐stranded DNA phage M13 was considerably more so. These results, together with others discussed in the text, suggest that DNA and possibly other macromolecules can serve as targets for harmine photoactivity.
SITES OF PHOTOSENSITIZATION BY DERIVATIVES OF HEMATOPORPHYRIN
Authors: Kessel David 
Published: January 2008

AbstractLeukemia L1210 cells were incubatedin vitrowith the tumor‐localizing product HPD (hem‐atoporphyrin derivative) for 0.5. 4 and 18 h. Effects of subsequent irradiation on viability, membrane transport and integrity, DNA synthesis and intracellular ATP concentration were assessed. Intracellular porphyrin pools were analyzed by HPLC. A 30 min incubation led to concentration of a readily‐exchangeable pool of monomeric HPD components at plasma membrane loci; irradiation resulted in photodamage to membrane transport and a loss in capacity for dye exclusion. In contrast, increasing the incubation time led to a corresponding increase in the size of a non‐exchangeable intracellular pool of other HPD components. Subsequent irradiation led to depletion of intracellular ATP and loss of capacity for biosynthesis of DNA, but little plasma membrane damage.
THE PHOTOPHYSICAL PROPERTIES OF PORPHYCENES: POTENTIAL PHOTODYNAMIC THERAPY AGENTS*
Authors: Aramendia Pedro F. , Redmond Robert W. , Nonell Santiago , Schuster Wolfang , Braslavsky Silvia E. , Schaffner Kurt , Vogel Emanuel 
Published: January 2008

AbstractPorphycene and a tetra‐n‐propyl derivative remained unaltered on irradiation in toluene at room temperature. Quantum yields of fluorescence, S T intersystem crossing, and singlet molecular oxygen sensitization, as well as lifetimes of the singlet and triplet excited states were measured. In view of their structural relationship to porphyrin, their high absorption above 620 nm, their stability towards photooxidation, and their high quantum yields of fluorescence and singlet oxygen sensitization, these compounds qualify as potential agents for tumor marking and photodynamic therapy.
PHOTODYNAMIC GENERATION OF HYDROXYL RADICALS BY HEMATOPORPHYRIN DERIVATIVE AND LIGHT
Authors: Steveninck J. Van , Tijssen K. , Boegheim J. P. J. , Der Zee J. Van , Dubbelman T. M. A. R. 
Published: January 2008

AbstractIn a reaction mixture containing hematoporphyrin derivative, deoxyribose, Fe3+‐EDTA and either methionine or tryptophan, hydroxyl radicals were formed during illumination with visible light. When either hematoporphyrin derivative, Fe3+‐EDTA or the amino acid was omitted from the reaction mixture, the generation of hydroxyl radicals ceased. These observations suggest an iron‐catalyzed Haber‐Weiss reaction, involving superoxide and hydrogen peroxide in the generation of hydroxyl radicals. It could be shown that with methionine H2O2 was indeed an essential intermediate in the reaction sequence. With tryptophan, however, H2O2, was not generated. Apparently a photooxidation product of tryptophan could replace H2O2 in the OH‐generating reaction with Fe2+‐EDTA. Although superoxide was generated in the reaction mixture, it was not an indispensable intermediate. Apparently a porphyrin radical, formed via photoexcitation of hematoporphyrin derivative, could replace superoxide in the Haber‐Weiss reaction.
ARE THERE SEVERAL PHOTORECEPTORS INVOLVED IN PHOTOTROPISM OF Phycomyces blakesleeunus? KINETIC STUDIES OF DICHROMATIC IRRADIATION*
Authors: Löser Georg , Schäfer Eberhard 
Published: January 2008

Abstract— Photogeotropic equilibrium angles were measured for Phycomyces blakesleeanus wild type firstly by means of dichromatic fluence rate response curves using simultaneous irradiation with near threshold 450 nm reference light (constant at 1.2 × 10−8 W m−2) and variable fluence rates of test light (498–630 nm) from the same side. These curves showed minima for test light fluence rates that were close to the photogeotropic threshold for these wavelengths. Secondly, the time course of this inhibitory effect was studied with both the inductive reference 450 nm light (2 × 10−‐7 W m−2) and the test light (606 or 450 nm) given as light pulses of 2 s duration (2 s light/48 s dark periods for 6 h). The dark period between the onset of the inductive reference light and test light pulses was varied between 0 and 48 s. No inhibitory effects were observed for simultaneous pulses; however, inhibitory effects were demonstrated for delay times of 2 s and 20 s for 606 nm as well as 450 nm test light. If the test light pulses were given immediately before the inductive reference light, only 606 nm test light was effective in producing a significant inhibitory effect.The results are discussed with regard to a multichromophoric photoreceptor system and to the wavelength dependence of the effects observed. The data and conclusions favor a photoreceptor system with at least two separate chromophoric absorptions of the blue light receptor type, one acting positively, the other acting inhibitorily, and at least one other photoreceptor of presumably minor influence.
POTENTIALLY USEFUL ANTIMICROBIAL and ANTIVIRAL PHOTOTOXINS FROM PLANTS*
Authors: Towers G. H. N. , Hudson J. B. 
Published: January 2008

AbstractThe wide range of naturally occurring compounds from microorganisms and plants which are phototoxic in UV‐A light (320‐400 nm) includes cinnamyl esters, coumarins and furanocoumarins, furanochromones, benzofurans, alkaloids, based on tryptophan or phenylalanine, extended naptho‐and anthraquinones, polyacetylenes and their thiophene derivatives. The cellular targets are cell membranes, e.g. acetylenes, or the nucleus, e.g. furanocoumarins. Compounds reacting with cell membranes in light either generate singlet oxygen, e.g. a‐terthienyl, or react by a free radical mechanism, e.g. phenylheptatriyne, or do both. Those that react with nucleic acids intercalate with these macromolecules forming photoadducts, e.g. furanocoumarins, furanochromones and furan‐oquinolines. With others, such as the β‐carbolines, the explanation for their photogenotoxicity is unknown.A number of these natural photosensitizers have been examined with bacteria, yeasts, and viruses and the mechanisms of phototoxicity have been elucidated. Some of the sulfur‐containing acetylenes may be useful in photochemotherapy.
MENADIONE SENSITIZED PHOTOOXIDATION OF NUCLEIC ACID and PROTEIN CONSTITUENTS. AN ESR and SPIN‐TRAPPING STUDY
Authors: Krishna C. Murali , Decarroz C. , Wagner J. R. , Cadet J. , Riesz P. 
Published: January 2008

AbstractThe menadione photosensitized reactions of nucleic acid and protein constituents were studied by ESR and spin trapping. Thymine, thymidine, cytosine, 2′‐deoxycytidine,5′‐dCMP, uracil and several N‐acetyl amino acids and dipeptides were investigated. Photolysis at 335 nm was carried out in air‐saturated or Ar saturated DMSO : H2O (1 : 1, vol/vol) containing 10 3M menadione and 10‐2M 2‐methyl‐2‐nitrosopropane as the spin trap. The observed spin adducts were explained in terms of electron transfer from the substrate to the excited triplet state of menadione to form the radical cation of the substrate and the anion radical of menadione which was also detected by ESR.
PHOTOSENSITIZATION BY PORPHYRINS DELIVERED TO L CELL FIBROBLASTS BY HUMAN SERUM LOW DENSITY LIPOPROTEINS. A MICROSPECTROFLUOROMETRIC STUDY
Authors: MORLIERE P. , KOHEN E. , REYFTMANN J. P. , Santus R. , KOHEN C. , Maziere J. C. , Goldstein S. , Mangel W. F. , Dubertret L. 
Published: January 2008

AbstractHuman serum LDL were used as vehicles to deliver protoporphyrin and hematoporphyrin dimer to L cell mouse fibroblasts. Topographic analysis by microspectrofluorometry on single living cells shows that after digestion of LDL, protoporphyrin is localized in cytoplasmic areas. Protoporphyrin and hematoporphyrin dimer are readily bleached by 420 ± 60 nm radiations at the high fluence rate used. Complex bleaching kinetics are observed. Spectral studies using the same technique demonstrate that an intense fluorescent emission (λmax= 450 nm) is produced immediately after the onset of irradiation with 365 ± 2 nm or 420 ± 60 nm radiations using LDL loaded with protoporphyrin or Photofrin II. These fluorescent products have been previously identified as lipofuscin‐like pigments formed by reaction of lipid photoperoxides with amino groups. The permeation of lysosomal membranes is also induced after delivery of the porphyrins by LDL. This permeation can be strongly inhibited not only by the lysosomal inhibitors chloroquine and monensin but also by a‐tocopherol. On the other hand, neither α‐tocopherol nor chloroquine or monensin inhibit the lipofuscin‐like pigment formation.
Monodelphis domestica: A NEW ANIMAL MODEL FOR STUDIES IN PHOTODERMATOLOGY*
Authors: Ley Ronald D. 
Published: January 2008

AbstractThe ability to photoreverse pyrimidine dimers in DNA of the South American opossum Monodelphis domestica provides a powerful tool with which to probe the role of pyrimidine dimers in ultraviolet radiation (UVR)‐induced histopathologic changes of the skin of this mammal. We have observed that post‐UVR exposure to photoreactivation light not only reversed pyrimidine dimers in epidermal DNA, but also suppressed the capacity of UVR to induce macroscopic and microscopic changes in the skin of M. domestica.