bluuebunny/crossref_metadata_2025 huggingface dataset:
PHOTODYNAMIC INACTIVATION OF CHINESE HAMSTER CELLS
Authors: Ganguly Tapan , Bhattacharjee Sukhendu B.
Published: January 2008

Abstract— Visible light exposures have been shown to kill acriflavine bound Chinese hamster cells. Such killing was enhanced when (a) dye was present in the medium during irradiation and (b) the pH of the medium was 8.5, instead of the normal 7.5 during the exposure. The induced killing could be suppressed by the presence of sodium azide during exposure. The results were taken to indicate that both DNA and non‐DNA sites were involved in the cellular inactivation by visible light and that singlet oxygen was involved in the process.
A DIURNAL RHYTHM IN THE RATE OF LIGHT‐INDUCED ELECTRON FLOW IN MAIZE BUNDLE SHEATH STRIPS
Authors: LONERGAN THOMAS A.
Published: January 2008

Abstract— A technique for the rapid mechanical isolation of bundle sheath strips from Zea mays was used to study the rate of light‐induced electron flow as a function of time of day. Seedlings were raised for 10 days in light/dark cycles and then exposed to various intensities of light. The rate of light‐induced electron flow was measured five times during the 24‐h cycle using a whole cell, H2O to methyl viologen assay in the presence of gramicidin. The uncoupled rate of electron flow reached a maximum at midday and then decreased for the remainder of the cycle.

If at the end of the 14‐h dark period plants were either maintained in darkness, or exposed to very low irradiance white light. then no rhythmicity was observed. If continuous light at higher irradiance was used, then only one additional peak of activity was observed. The minimal light irradiance necessary to allow the continued expression of the rhythm in light/dark cycles is in the range between 11 to 54 W m‐2. A 15‐min bright‐light (54 W m‐2) pulse administered at dawn is not sufficient to stimulate the expression of the rhythm indicating that the light during the light/dark cycle is doing more than just acting as a “light‐on” synchronizing signal. An imposed dark period is also necessary if the rhythm is to be expressed for more than one cycle.
RED/FAR‐RED PHOTOREVERSIBILITY: NOT AN APPROPRIATE PHYTOCHROME ASSAY FOR RED‐LIGHT PREIRRADIATED CORN COLEOPTILES
Authors: SCHMIDT WERNER
Published: January 2008

Abstract— Based on measurements with a single beam spectrophotometer, it has been found that subsequent red/far red irradiation cycles, which are usually given to monitor phytochrome content by dual wavelength spectroscopy, induce chlorophyll‐related absorption changes in maize coleoptiles. Therefore, the difference signal, usually measured between 730 and 800 nm or 660 and 730 nm after saturating red and far red irradiations, does not represent solely the phytochrome content of preirradiated samples.
UV‐LYSOGENIC INDUCTION OF Λ PHAGE IN lexA1 MUTANTS OF Escherichia coli: KINETICS OF THE PROCESS
Authors: Carvalho R. E. S. , Leitāo A. C.
Published: January 2008

Abstract— Although the lex gene has been described until recently as being required for lysogenic induction, both our work and the work of others have reported Λ prophage induction in some lexA mutants. However, the characteristics of the process were not defined. We describe UV induction of prophage in a lexA1 mutant at a slightly lower level and requiring 2 times longer than the wild type. As demonstrated in some work, in cells treated with low levels of rifampicin (RIF) no new synthesis of RecA protein is needed for the prophage induction although the onset of lysis is delayed. We suggest that the lysogenic induction in lexA cells is due to the same mechanism that induces prophage in the wild type cells treated with RIF. That is, the induction is due to the cleavage of Λ represser by the basal RecA protease in the DNA‐single‐strand gap, since RecA protease and monomer represser both have high affinity for this type of DNA. So, LexA protein need not be cleaved for the prophage induction.

No Weigle‐reactivation (WR) was detected in the lex mutant even after a long post‐irradiation incubation, suggesting that unlike prophage induction, WR requires LexA protein cleavage.
TEMPERATURE DEPENDENCE OF PHOTOSENSITIZED ELECTRON TRANSPORT ACROSS LIPID VESICLE WALLS
Authors: Mettee Howard D. , Ford William E. , Sakai Tetsuya , Calvin Maelvin
Published: January 2008

Abstract— An overall Arrhenius activation energy of 117 plusmn; 19 kJ/mol (28.0 plusmn; 4.5 kcal/mol) has been measured for photosensitized electron transport across phospholipid vesicle walls in the temperature range 18–38°C. A dynamic model for the overall process is proposed which accounts for the parabolic growth curves of the kinetically probed species, heptyl viologen radical. The temperature dependence of the initial quantum yield derived from these curves, and of fluorescence quenching behavior of the ruthenium tris‐bipyridyl photosensitizer, is used to estimate an activation energy of 67 plusmn; 21 kJ/mol(16 plusmn; 5 kcal/mol) for the electron transport step itself. The activation energy for the co‐transport of charge compensating ions is estimated to contribute no more than 4.6 kJ/mol to this energy.
GENETIC VARIATIONS AND LINOLENIC ACID INDUCED CHANGES IN THE ORIENTATION PATTERN OF CHLOROPHYLL a IN THYLAKOID MEMBRANES
Authors: Szitó T. , Kiss J. G. , Garab GY. I. , Mustárdy L. A. , Faludi‐Dániel Á.
Published: January 2008

Abstract Orientation pattern of the Qy absorption and emission dipoles of chlorophyll a were studied in wild type Scenedesmus obliquus and in mutants deficient in chlorophyll b and carotenoids. Fluorescence polarization ratio at –140°C and linear dichroism at 25°C were measured in whole cells and thylakoids aligned in polyacrylamide gel. Unlike normal thylakoids, mutants displayed fluorescence polarization ratios significantly lower than 1.0 and showed a negative LD signal around 672 nm, indicating the tendency of the Qy dipoles to tilt out from the membrane plane. Such an orientation pattern can also be artificially induced by treating normal thylakoids with linolenic acid.
THE RATE OF REMOVAL OF SUNLIGHT‐INDUCED PYRIMIDINE DIMERS FROM THE DNA OF CULTURED HUMAN DIPLOID FIBROBLASTS
Authors: Kantor G. J. , Ritter C.
Published: January 2008

Abstract The rate of excision of sunlight‐induced pyrimidine dimers in DNA of exposed human cells was determined. Two normal excision repair‐proficient human diploid fibroblast strains (WS‐1 and KD) and a repair‐deficient strain (XP12BE, group A) maintained in a nondividing state were exposed to summer noon‐time sunlight for times (5 and 20 min) that induced numbers of dimers equivalent to far UV (254 nm) exposures of 1 and 4 J/m2. Pyrimidine dimers were quantified in extracted DNA using a U V‐endonuclease‐alkaline sedimentation assay. The excision rates of these dimers were similar to those observed for the excision of UV‐induced pyrimidine dimers. No sunlight‐induced inhibition or stimulation of DNA repair was observed in either strain at these low exposures.
METHYL SALICYLATE FLUORESCENCE AS A PROBE OF THE GEOMETRY OF COMPLEXATION TO CYCLODEXTRINS
Authors: Cox G. Sidney , Turro Nicholas J.
Published: January 2008

Abstract Methyl salicylate (MS) is found to form complexes with α‐, β‐ and γ‐cyclodextrins in aqueous solution. The fluorescence of the complexes differ dramatically from that of MS in pure aqueous solution in the case of α‐ and γ‐cyclodextrin, but is similar to that of MS in pure aqueous solution in the case of β‐cyclodextrin. The binding constants for the complexes have been evaluated and the fluorescence of the complexes has been employed to infer the geometry of the complexes.
MODIFYING FACTORS OF THE CELLULAR CONCENTRATION OF PHOTOLYASE MOLECULES IN Saccharomyces cerevisiae—II. EFFECTS OF PREILLUMINATION WITH LIGHT FLASHES
Authors: Fukui Atsushi , Laskowski Wolfgang
Published: January 2008

Abstract The effects of preillumination with photoreactivating light flashes before UV‐irradiation on the number of photoreactivable complexes consisting of UV‐induced DNA‐damages and active photolyase molecules (NPREact), on the fluence decrements, ΔDPRE, that are obtained from two UV‐survival curves without and with 1 flash photoreactivation and proportional to NPREact were determined in haploid Saccharomyces cerevisiae cells. ΔDPRE increased by preillumination from 0.115 Jm–2 to 0.460 Jm–2 and from 0.376 Jm–2 to 0.494 Jm–2 in cells in logarithmic growth phase and in stationary growth phase, respectively. ΔPRF in log‐cells that were preilluminated before and after resuspension in buffer at 40°C for 60 min was larger than ΔDPRE in log‐cells preilluminated only after resuspension in buffer.
MODE OF COACTION OF PHYTOCHROME AND BLUE LIGHT PHOTORECEPTOR IN CONTROL OF HYPOCOTYL ELONGATION
Authors: Drumm‐Herrel Helga , Mohr Hans
Published: January 2008

AbstractThe rate of hypocotyl longitudinal growth in seedlings ofSesamum indicumL. is strongly inhibited by continuous blue light (cBL)† and slightly by continuous far‐red light while continuous red light (cRL) or red light pulses are hardly effective from 60 h after sowing onwards. Between 36 and 60 h after sowing the growth rate responds to red light pulses the effect of which is fully reversible by long wavelength far‐red light. When seedlings are kept in cBL for 3 days and then treated with red light hypocotyl growth rate responds strongly. However, RL effectiveness decreases with time after transfer from BL to RL. BL → darkness transfer experiments with different levels of Pfrestablished at the beginning of darkness show that after a BL pretreatment phytochrome (Pfr) alone is capable of fully controlling growth rate. When white light (WL) is given no BL effect is detectable in weak WL. Only high light fluxes maintain a typical BL growth rate. At medium WL fluxes elongation rate returns gradually to the dark rate. The simplest explanation of the data is that light absorbed by a separate BL photoreceptor is necessary to maintain responsivity to Pfr. With increasing age of the seedlings the requirement for BL increases strongly. On the other hand, brief light pulses—given to demonstrate photoreversibility of phytochrome—remain equally effective provided that responsivity to Pfrexists.
P‐AMINOBENZOIC ACID CAN SENSITIZE THE FORMATION OF PYRIMIDINE DIMERS IN DNA: DIRECT CHEMICAL EVIDENCE
Authors: Sutherland John Clark , Griffin Kathleen Pietruszka
Published: January 2008

Thymine‐containing photoproducts with chromatographic properties similar to those of cyclobutyl pyrimidine dimers can be formed in [3H]‐thymine‐labeled DNA in solution by 313 nm ultraviolet radiation in the presence of para‐aminobenzoic acid (PABA), a compound used in sunscreen preparations. In the absence of PABA, similar fluences of 313 nm radiation do not produce significant numbers of these photoproducts. The thymine‐containing photoproducts can be reversed by 254 nm radiation so that the tritium label migrates with the mobility of thymine monomer, a behavior characteristic of thymine‐containing cyclobutyl pyrimidine dimers. This result supports previous, but less direct, data from other laboratories indicating that PABA can sensitize dimer formation in the DNA of bacterial and mammalian cells.
EVIDENCE AGAINST THE PRODUCTION OF SUPEROXIDE BY PHOTOIRRADIATION OF HEMATOPORPHYRIN DERIVATIVE
Authors: Gibson Scott L. , Cohen Harvey J. , Hilf Russell
Published: January 2008

Abstract Experiments were performed to ascertain whether superoxide anion (O2−) was produced by the photodynamic activation of hematoporphyrin derivative (HPD). Three different systems were utilized to detect formation of O2−, oxidation of epinephrine to adrenochrome, reduction of cytochrome c and reduction of nitro blue tetrazolium (NBT). The effects on these detectors under identical conditions for HPD + hν were compared to those obtained with two O2− generating systems, riboflavin + by and xanthine‐xanthine oxidase, and to a singlet oxygen generating system, photoradiation of methylene blue. The results indicated that HPD + hv differed from the two O2− generating systems in failing to reduce cytochrome c or NET, and that HPD + hν was similar to the behavior of methylene blue + hν. In addition, HPD + hν but not the O2− generating systems could inhibit mitochondrial cytochrome c oxidase activity. We conclude that the photodynamic activation of HPD does not produce O2− as a major oxygen radical and that the effects of HPD + hν on mitochondrial cytochrome c oxidase are not caused by O2−.
EFFECTS OF QUENCHING AGENTS ON THE PHOTODYNAMICALLY‐INDUCED CHEMOTACTIC RESPONSE OF THE COLORLESS FLAGELLATE Polytomella magna
Authors: Nultsch Wilhelm , Kumar Har Darshan
Published: January 2008

Abstract In the presence of the photosensitizer riboflavin at high fluence rates a photoproduct, most probably H2O2, is formed which causes negative phototaxis in the colorless flagellate Polytomella magna. The aim of this study was to find out whether H2O2 is produced in a type I or II reaction. As has been shown, 1O2 quenchers either do not influence the photodynamic action of riboflavin (furfuryl ethanol, DPBF, l‐histidine, crocetin) or show slight quenching effects only at very high concentrations ≧ 10−2M (DABCO, DMF, imidazole). D2O is toxic to P. magna even in 1:1 and 1:2 mixtures with H2O. On the other hand, the quenching effect of 1,4‐benzoquinone, highly indicative for the type I pathway, is more than two orders of magnitude stronger than the one of the above mentioned 1O2 quenchers. The results suggest that H2O2 is produced in a type I reaction. Superoxide does not seem to be involved since superoxide dismutase does not diminish the photodynamic effect of riboflavin.
INTERACTION OF HUMAN SERUM LOW DENSITY LIPOPROTEINS WITH PORPHYRINS: A SPECTROSCOPIC AND PHOTOCHEMICAL STUDY
Authors: REYFTMANN J. P. , MORLIERE P. , GOLDSTEIN S. , SANTUS R. , DUBERTRET L. , LAGRANGE D.
Published: January 2008

The incorporation of proto‐, uro‐ and hematoporphyrin in low density lipoproteins (LDL) of human blood has been studied by equilibrium dialysis, fluorescence and absorption spectroscopy. The lipoproteins may efficiently compete with albumin in the binding of protoporphyrin to human blood proteins in patients suffering from protoporphyria. It can be concluded that hydrophobic porphyrins bind to blood proteins.

The complexation of hydrophobic porphyrins in LDL is responsible not only for efficient photodynamic effect at the lipoprotein level, but also for photoinduced lipid peroxidation and for consumption of β‐carotene incorporated into LDL which are one of their natural carriers. The water‐soluble uroporphyrin, although an efficient photosensitizer for the LDL apoprotein photoinactivation, is much less efficient for lipid peroxidation and β‐carotene bleaching. The 353 nm laser flash photolysis shows that porphyrin triplet states are not affected by the physiological β‐carotene content of LDL but are fully accessible to oxygen.
ROTATIONAL DIFFUSION OF RHODAMINE 6G IN HUMAN BLOOD SERUM
Authors: Klein Uwe K. A. , Hönes Gertrud , Hafner Friedrich W.
Published: January 2008

Abstract —The time‐dependent rotational relaxation of Rhodamine 6G in fresh and dried human blood serum was investigated using picosecond phasefluorometry. Measurements were also carried out in aqueous solutions of amino acids, glucose, urea, and bovine serum albumin to evaluate our model for the interactions. It is shown that the distribution of Rhodamine 6G between the aqueous and the protein phase of the blood serum strongly depends on protein concentration and temperature.
SENSITIZED PHOTOOXIDATION OF PINENES BY 9,10‐DICYANOANTHRACENE
Authors: Zhang Bao‐wen , Ming Yang‐fu , Cao Yi
Published: January 2008

Abstract —The products of 9,10‐dicyanoanthracene sensitized photooxidation of α‐ and β‐pinene were separated and identified. The mechanism of this reaction was investigated by fluorescence spectroscopy, solvent dependence and determination of oxidation potentials of olefins. The formation of an exciplex between excited dicyanoanthracene and pinenes was observed in non‐polar solvents. On the bases of these observations, an electron transfer mechanism is proposed for the initial step of this reaction.
THE RADIOLYTIC REDUCTION OF THE SCHIFF BASE IN BACTERIORHODOPSIN
Authors: Druckmann S. , Renthal R. , Ottolenghi M. , Stoeckenius W.
Published: January 2008

Abstract —Nanosecond electron beam pulses cause radiolytic reduction of the retinal Schiff base in bacteriorhodopsin. The effects of different scavengers show that both H atoms and the formate radical anion can act as the reducing species. Model system studies on the radiolysis of retinal indicate transient formation of a retinal radical anion and suggest an analogous two‐step reaction in bR. Delocalization of the radical in the polyene system and reaction with surrounding groups would account for the relatively low yield of reduced Schiff base and the appearance of intra‐ and intermolecular crosslinks in irradiated bacteriorhodopsin.
PHOTOCHEMICAL BINDING OF PHENOTHIAZINES ON BIOLOGICAL MEMBRANE PROTEINS
Authors: TESTYLIER GUY , DAVELOOSE DENIS , LETERRIER FRANÇOIS , BUCHMANN OURI , SHIMONI MICHAEL
Published: January 2008

Abstract— The photobinding of phenothiazine derivatives (chlorpromazine, fluphenazine, promazine and promethazine) was studied on four different types of biological membranes (microsomes, myelin and synaptosomes from rat brain as well as human erythrocytes). The photoreaction was performed by ultraviolet irradiation of the tritiated compounds in their long wavelength absorption band (313 nm) and bound photoproducts were analysed by autoradiography of the proteins separated by polyacrylamide gel electrophoresis. The specificity of binding is low, however, a 34000 dalton band is intensely labeled on synaptic membranes with chlorpromazine and fluphenazine. All the phenothiazines bind on erythrocyte membrane proteins and specially on band 4.2 and on a peptide located before actin on the electrophoresis gel. These results show the generality of the phenothiazine photobinding on membrane proteins. These photobinding properties can be used for the identification and localization of some of these proteins.
DIFFERENT EFFECTS OF RAD GENES OF SACCHAROMYCES CEREVISIAE ON INCISIONS OF INTERSTRAND CROSSLINKS AND MONOADDUCTS IN DNA INDUCED BY PSORALEN PLUS NEAR UV LIGHT TREATMENT
Authors: MILLER RAYMOND D. , PRAKASH SATYA , PRAKASH LOUISE
Published: January 2008

Abstract— The RAD1, RAD2, RAD3 and RAD4 genes of Saccharomyces cerevisiae are required for incising DNA containing UV induced pyrimidine dimers or psoralen plus 360 nm light induced interstrand crosslinks. We have now determined if these genes are also required for incising DNA at psoralen plus 360 nm light induced monoadducts. For distinguishing between incision breaks occurring at crosslinks and at monoadducts. we have used the cdc9‐2 mutant, defective in DNA ligase activity at the restrictive temperature, and the radl‐2 cdc9‐2, rad2‐5 cdc9‐2, rad3‐2 cdc9‐2 and rad4‐4 cdc9‐2 double mutant combinations. We conclude that the radl, rad2, and rad4 mutants are defective in incising DNA both at crosslinks and monoadducts, whereas the rad3 mutant is proficient in incising DNA at monoadducts but not at crosslinks.
CLEARANCE TIMES OF PORPHYRIN DERIVATIVES FROM MICE AS MEASURED BY in vivo FLUORESCENCE SPECTROSCOPY
Authors: Kennedy J. C. , Nadeau P. , Petryka Z. J. , Porrier R. H. , Weagle G.
Published: January 2008

Abstract

The clearance times of 17 different porphyrin derivatives from SKH:HR‐1 mice have been measured using the technique of in vivo fluorescence spectroscopy. This technique monitors the in vivo porphyrin fluorescence observed from the external skin surface. Most hydrophilic porphyrin derivatives show relatively short clearance times, in the order of 2.5–6 h. The dicarboxylic acid porphyrins, proto‐, hydroxyethylvinyldeutero‐and hematoporphyrin IX have clearance times of 7.8, 12.2 and 14.7 h respectively. The mixture hematoporphyrin derivative has an intermediate clearance time of 12.6 h. N‐methylated porphyrins show clearance times in the vicinity of 15–22 h. Monoaspartyl chlorin e6 shows the longest clearance time of all porphyrin derivatives measured (30.3 h).
STUDIES ON HUMAN LENSES: II. DISTRIBUTION AND SOLUBILITY OF FLUORESCENT PIGMENTS IN CATARACTOUS AND NON‐CATARACTOUS LENSES OF INDIAN ORIGIN
Authors: Bandyopadhyay S. , Chattopadhyay D. , Ghosh S. K. , Chakrabarti B.
Published: January 2008

Abstract— Fluorometric studies of cataractous and non‐cataractous human lenses were carried out to study the emission characteristics and the distribution and solubility of lenticular pigments. Most of the detected fluorophores were well distributed over the cortical and nuclear portion of the lens. The decrease in solubility of proteins with aging and cataract formation is concomitant with increasing photolysis of tryptophan. However, this is likely a phenomenon independent of the photochemical transformations of the lens proteins. The number of emitting species in the diseased lenses are higher than in the normal mature lenses. A species emitting around 375 or 388 nm is of particular interest (λcx, 330 nm) in that the emission characteristics of this fluorophore resemble kynurenic acid which has a high photosensitizing efficiency. The concentration of fluorescent pigments in the lenses of Indian origin is significantly high. The intense pigmentation could be attributed largely to the formation of photoproducts in the absence of normal endogenous antioxidant accumulation that is dependent on nutrition standard. If, indeed, any of these fluorescent pigments, because of their photosensitizing ability, are responsible for lenticular opacity, it is not the abundance of sunlight alone but also malnutrition that could account for the high incidence of cataract in India.
OXYGEN DEPENDENCE OF HYPERICIN‐INDUCED PHOTOTOXICITY TO EMT6 MOUSE MAMMARY CARCINOMA CELLS
Authors: Thomas Carin , Pardini Ronald S.
Published: January 2008

Abstract

The photodynamic effect of hypericin on EMT6 mouse mammary carcinoma cells was investigated in vitro under aerobic and hypoxic conditions. Under aerobic conditions, hypericin‐induced photocytotoxicity was dose dependent within a 1–50 μM range. Under hypoxic conditions, cells were resistant to hypericin‐induced phototoxicity. In the dark, no cytotoxicity was observed at any hypericin concentration tested either aerobically or hypoxically. Cellular accumulation of hypericin, examined by chemical extraction and spectroscopy, occurred under both hypoxic and aerobic conditions. Fluorescence photomicrographs of cells exposed to hypericin corroborate drug uptake in the plasma membrane and subcellular regions. Our results demonstrate that hypericin cytotoxicity to EMT6 mouse mammary carcinoma cells in vitro is both light and oxygen‐dependent. These results suggest that EMT6 cell kill caused by photoactivated hypericin is mediated by an oxygen‐dependent mechanism, rather than by a type I oxygen‐independent mechanism.
INHIBITION OF PHOTOTAXIS IN Volvox aureus BY NATURAL AND SIMULATED SOLAR ULTRAVIOLET LIGHT
Authors: Blakefield Mary K. , Calkins John
Published: January 2008

Abstract

Exposure to artificial UV wavelengths and the UV component of sunlight delays positive phototaxis in the green alga Volvox aureus. Broad band wavelength filters were used to modify the output from UV‐B sources (280–320 nm) and natural sunlight. The delay in phototaxis by artificial UV is increased with exposure to shorter UV‐B wavelengths. Natural sunlight experiments were performed with exposure to full sunlight and to its UV component only. The UV component present in summer sunlight produced long periods of inhibition in phototaxis and even lethality, while exposure to the total spectrum of sunlight had no significant effects on movement or survival. The data indicate that although this species of alga is well equipped to deal with present levels of UV exposure, increases in the short UV‐B wavelengths in sunlight may force an alteration in patterns of photomovement.
SYNTHESES AND PHOTOREDOX PROPERTIES OF POLYELECTROLYTES FUNCTIONALIZED WITH 5‐DEAZAFLAVIN
Authors: Morishima Yotaro , Kitani Toru , Kobayashi Takaomi , Saeki Yasuhiro , Nozakura Shun‐ichi , Ohno Takeshi , Kato Shunji
Published: January 2008

Abstract— Anionic polyelectrolytes functionalized with the 5‐deazaflavin group (dFl) were synthesized. The lifetime of the triplet excited dFl in the polyelectrolytes with a 2‐mol% dFl content (AdFl‐2) was about 10 times longer than that of a low molecular weight analog (AdFl‐M). 2‐Mercaptoethanol (RSH) reduced the triplet dFl with the rate constant of kred= 2.01 × 108M−1 s−1 for AdFl‐M and kred= 4.4 × 107M−1 s−1 for AdFl‐2. A zwitterionic viologen (SPV) oxidized the triplet dFl with the rate constant of kred= 3.69 × 109M−1 s−1 for AdFl‐M and kox= 7.4 × 108 M−1 s−1 for AdFl‐2. The smaller rate constants for the polymer system were discussed in terms of the hindering effect of the macromolecular microenvironment. The back electron transfer was shown to be drastically slowed in the AdFl‐2‐SPV system as a result of the intensive electrostatic effect of the polyelectrolytes. The buildup of the viologen radicals was studied under the steady‐state illumination of the three component systems including viologen and RSH. The dFl group was demonstrated to serve as a very efficient photosensitizer in the oxidative cycle in case back electron transfer was retarded. This is the case of the AdFl‐2‐SPV system which gave the quantum yield of about 0.4 for the SPV− buildup. By comparison, the AdFl‐2‐MV2+ system resulted in a much slower buildup of MV +radicals.
PHOTOPHYSICAL and PHOTOCHEMICAL PROPERTIES OF COUMARIN DYES IN AMPHIPHILIC MEDIA
Authors: Jones Guilford , Jackson William R. , Kanoktanaporn Santhi , Bergmark William R.
Published: January 2008

Abstract— Photophysical properties of coumarin dyes solubilized in aqueous detergent solutions have been investigated including measurement of absorption and fluorescence emission maxima, and fluorescence quantum yields. Use of coumarin 4 as a fluorescence probe of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) solutions led to the conclusion that the sites for dye incorporation in micelles are significantly hydrogen‐bonded (hydrated). The inhibition of photochemical decomposition for detergent‐solubilizcd dyes has also been observed. Electron transfer from micelle‐bound dye to a water soluble acceptor, methyl viologen, has been investigated by flash photolysis.
IMMUNOBLOT ANALYSIS OF CROSS‐REACTIVITY OF MONOCLONAL ANTIBODIES AGAINST OAT PHYTOCHROME WITH PHYTOCHROME FROM SEVERAL PLANT SPECIES*
Authors: Whitelam Garry C. , Anderson Mary L. , Billett E. Ellen , Smith Harry
Published: January 2008

Abstract— Eighteen monoclonal antibodies (mAbs) have been produced against partially degraded phytochrome from A vena sativa cv. Trafalgar. Several of the mAbs are capable of recognising the antigen on immunoblots following sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS‐PAGE) and protein electroblotting. Six of these mAbs were screened for the ability to recognise electroblotted phytochrome from eight plant species. Particularly amongst the monocot species tested, but also amongst the dicots, the mAbs showed extensive cross‐reactivity. The results suggest that there are perhaps several conserved antigenic sites on the phytochrome molecule.
A FLASH PHOTOLYSIS STUDY OF 5‐METHOXYINDOLE
Authors: Kuntz Robert R. , Ponder Morgan , Ghiron Camillo A.
Published: January 2008

Abstract— The microsecond flash photolysis of 5‐methoxyindole in aqueous solutions has been studied at γexc≥ 290 nm. Transients identified in this time realm in neutral solutions are: eaq‐, the 5‐methoxyindole radical cation (γmax≅ 440 nm), the neutral transient with γmax≅ 530 nm) and an unidentified oxygen sensitive transient with γmax≅ 435 nm. Radical cations and e‐aq are shown to be produced in equal amounts consistent with a photoionization process as the only source of both transients. H+ quenching of fluorescence and radical cation production gives equivalent Stern‐Volmer constants indicating that photoionization occurs from the fluorescent state. The unidentified oxygen sensitive transient exhibits a pKa of2–2.5 and is quenched at lower pH values indicating that it also has a fluorescent state precursor.
ABSORBANCE and CIRCULAR DICHROISM SPECTRA OF 1‐C1S PHOTOPRODUCT FORMED BY IRRADIATING FROG RHODOPSIN
Authors: Azuma Katsu , Azuma Masami
Published: January 2008

Abstract— We showed by spectrophotometry and HPLC that a photoproduct having 7‐cis retinal (1‐cis photoproduct) can be derived from the photoisomerization of frog lumirhodopsin (L) and metarhodopsin I (M I). The efficiency of the isomerization was higher in M I than in L. The absorption maximum of the 1‐cis photoproduct at ‐20°C is at 455 nm, and its maximum absorbance 1.1 times as large as that of rhodopsin. The photoproduct exhibited two positive CD bands at 450 nm α‐band) and 320 nm (β‐band); the molecular ellipticity at a‐band ([θ] = 73000) being larger than that of rhodopsin ([θ] = 61000). Re‐examination of the absorption spectra of rhodopsin intermediates gave the absorption maxima of L. M 1 and M 111 to be 522, 482 and 475 nm, respectively.
A RAPID PROCEDURE FOR THE PURIFICATION OF 124 kDALTON PHYTOCHROME FROM AVENA
Authors: Datta Neeraj , Roux Stanley J.
Published: January 2008

Abstract— A modification of previously published procedures is described which permits the preparation of high‐purity 124 kDa phytochrome within 14 h. The last 5 h are used for chromatography on a molecular sieve column, so all the handling steps are completed within 9 h. The procedure is simpler and faster than previously published methods.
FREE RADICALS FROM THE PHOTODECOMPOSITION OF BLEOMYCIN
Authors: Antholine William E. , Sarna Tadeusz , Sealy Roger C. , Kalyanaraman Balaraman , Shields Glen D. , Petering David H.
Published: January 2008

Abstract— Irradiation of bleomycin with light (λ > 320 nm) leads to a decrease in absorbance at 290 nm, which is suppressed by metal ions and by oxygen. Light‐induced oxygen consumption is diminished by the enzymes superoxide dismutase and catalase, implying that toxic reduced species of oxygen (O2 and H2O2) are formed during irradiation. Spin‐trapping measurements with 5,5‐dimethyl‐1‐pyrroline‐1‐oxide and 2‐methyl‐2‐nitrosopropane demonstrated that hydroxyl radical and methyl radical adducts also are generated in the system. In addition, direct ESR measurements have shown that methyl radicals are produced during irradiation of bleomycin solutions at low temperatures, together with radicals probably derived from the bithiazole moiety of the bleomycin. The latter are also produced from irradiation of the model compound bithia. Radical production is diminished by complexation of bleomycin with metal ions.
ANALYSIS OF LIGHT‐CONTROLLED ANTHOCYANIN FORMATION IN COLEOPTILES OF Zea mays L.: THE ROLE OF UV‐B, BLUE, RED AND FAR‐RED LIGHT
Authors: Beggs Christopher J. , Wellmann Eckard
Published: January 2008

Abstract— Light‐induced anthocyanin formation in Zea mays L. coleoptiles was investigated in seven different varieties of this species. Under the test conditions, four varieties showed practically no response to any waveband used (UV, continuous red and continuous far‐red), two responded strongly to both UV and far‐red, and one showed a strong response only to far‐red. The radiation‐sensitive varieties showed, however, only a very weak response to continuous red light. In those varieties sensitive to far‐red light, a pretreatment with continuous red light led to a greatly enhanced response to UV or in one case the manifestation of a response to UV that was previously lacking. Further investigations in one radiation‐sensitive variety (INRA) showed that the UV response was to UV‐B radiation below 350 nm. The UV response, as well as the far‐red and blue responses in this variety, showed fluence‐rate dependency. Red light was almost ineffective and showed only a very weak fluence‐rate dependency.
RESONANCE RAMAN STUDIES OF BACTERIORHODOPSIN ANALOGUES
Authors: Schiffmiller R. , Callender R. H. , Waddell W. H. , Govindjee R. , Ebrey T. G. , Kakitani H. , Honig B. , Nakanishi K.
Published: January 2008

Abstract— We present the results of resonance Raman measurements on a series of bacteriorhodopsin (bR) analogues formed from synthetic retinals which have replaced the native chromophore in the active site. Specifically, 5,6‐dihydro‐bR, 13‐desmethyl‐bR, 10‐methyl‐bR, 14‐methyl‐bR, and 10.14‐dimethyl‐bR have been studied. All five analogues bind and form Schiff base retinal‐apoprotein linkages. While the Schiff base linkages of 5,6‐dihydro‐bR, 13‐desmethyl‐bR, and 10‐methyl‐bR are protonated, like the native chromophore, the 14‐methyl‐bR, and 10,14‐dimethyl‐bR Schiff bases are unprotonated. These results suggest that the binding site of bacteriorhodopsin near the Schiff base moiety is different from that of rhodopsin. The protonated Schiff base ‐C=NH‐ stretching frequency of 5.6‐dihydro‐bR lies at 1660 cm‐1 which is unusually high for a bacteriorhodopsin based pigment. The downward shift upon deuteration is 16 cm‐1, essentially identical to that measured for bacteriorhodopsin. This and the other analogue results strongly reinforce our previous arguments that the Schiff base stretching frequency is determined in large part by two factors, the C=N force constant and the stretch interaction with C=N‐H bend. On the other hand, the deuterium isotope effect is determined primarily by the stretch‐bend interaction.
IN VIVO PROTECTIVE EFFECT OF β‐CAROTENE AGAINST PSORALEN PHOTOTOXICITY
Authors: Giles Albert , Wamer Wayne , Kornhauser Andrija
Published: January 2008

Abstract—

The protective effect of β‐carotene against PUVA‐ and UVB‐induced erythema was determined in groups of albino female Osborne Mendel rats fed standard, placebo or β‐carotene‐fortified diets. After 13 weeks, the backs of selected animals were clipped and the animals received 8MOP orally, 20 mg/kg in corn oil, followed by 5 J/cm2 UVA irradiation 2 h after dose. A significant β‐carotene protective effect was observed against phototoxicity induced by 8MOP, as measured by erythema production. A correlation was noted between the observed protective effect and β‐carotene serum and skin levels, determined by HPLC. No protective effect against erythema induced by UVB (0.7 J/cm2) was observed in animals fed the β‐carotene‐fortified diet. This report represents the first in vivo demonstration of a protective effect of dietary p‐carotene against psoraten‐induced phototoxicity. Possible mechanisms for the observed β‐carotene‐protective effect are discussed.
DISTORTION OF ACTION SPECTRA IN PHOTOMORPHOGENESIS BY LIGHT GRADIENTS WITHIN THE PLANT TISSUE
Authors: Kazarinova‐Fukshansky Nina , Seyfried Max , Schäfer Eberhard
Published: January 2008

Abstract—

Recently a method for measuring optical properties of light scattering and absorbing tissues was discussed (Seyfried et al., 1983). Based on measurements of transmittance and reflectance of cotyledons of dark‐ and light‐grown Cucurbita pepo L, seedlings a method to compute and correct apparent photoconversion cross sections for various distributions of a sensory pigment is described. The distortion function may be used to calculate expected apparent (distorted) action spectra for a pigment in vivo when the spectral properties of the pigment in vitro are known. With phytochrome as an example for a sensory pigment of low concentration within the tissue it is shown that the low apparent photoconversion cross section in blue light observed in etiolated seedlings can be explained solely by optical distortions caused by light gradients. In green tissue on the other hand the ratio of the apparent photo conversion cross sections in red and blue light is almost identical with that observed in vitro, but the ratio in red and far‐red light depends strongly on the distribution of the relevant sensory pigment. An analysis of the rate of phytochrome cycling shows an additional peak in the far‐red if the pigment is localized in the lower part of the tissue only.
INHIBITION OF DNA REPAIR SYNTHESIS BY SUNLIGHT
Authors: Parsons P. G. , Hayward I. P.
Published: January 2008

Abstract— DNA repair synthesis as determined by thymidine incorporation in the presence of hydroxyurea reached a much lower maximum level after solar compared with UVC exposure in five human melanoma cell lines, in HeLa cells, and in two human fibroblast strains. This finding was confirmed by determination of unscheduled DNA synthesis where both the number of labelled nuclei and grain count per nucleus were lower in sun‐exposed cells. In a cloned human melanoma line (MM253cl), glass‐filtered sunlight inhibited UVC repair synthesis, and solar UVB alone induced a higher level of repair synthesis than either complete sun or solar UVA plus solar UVB. The fluence response of filtered sunlight for inhibition of UVB (sunlamp) and UVC showed that most inhibition was obtained at low fluences (5‐10 min), further exposure giving a plateau at 40% of the original level. Ultraviolet C and sunlight inactivated adenovirus 5 giving F0 values for virus survival 40‐fold higher than for cell survival. Replication of either UVC‐ or solar‐irradiated virus was not affected by prior irradiation of cells with glass‐filtered sunlight. Stathmokinetic analysis of cell cycle progression by DNA flow cytometry showed that UVC and sunlamp UVB retarded cell movement from the G1 and S phases whereas equitoxic sunlight and glass‐filtered sunlight (nontoxic) had no effect. These results indicate that solar UVA at low environmental fluences partially inhibits UVB repair synthesis in a range of human cell types but does not affect the replication of a UVB‐ or UVC‐damaged virus when applied to the genome alone or to the host cell.
ACTION SPECTRA OF PHYTOCHROME IN VIVO*
Authors: Seyfried Max , Schäfer Eberhard
Published: January 2008

Abstract—A method is described to determine spectral properties of phytochromein vivo.For photochrome in 7‐day‐old dark‐grownCucurbita pepoL. seedlings the mole fraction of the far‐red‐absorbing form (Pfr) present at photoequilibrium at 664 nm was found to be 0.76 ± 0.02in vivo. Based on reflectance measurements, the photon fluence rate just below the surface of the cotyledons was calculated. Local rates of photoconversion for known local fluence rates were measured across cotyledons after non‐saturating irradiations with wavelengths between 544 and 781 nm andin situmolar photoconversion coefficients were obtained. In contrast to purified oat phytochrome, thein situmolar photoconversion coefficients for Pfrshow a strong shoulder between 660 and 700 nm. The maximum of Pfrabsorption is at 726 nm. An isosbestic point of phytochrome is found at 686 nm. The mole fraction of Pfrpresent at photoequilibrium with 686 nm light is 0.58. The ratio of photoconversion quantum yields (that for Pr→ Pfrdivided by that for Pfr→ Pr) is 1.38 ± 0.06.
BLEACHING OF BACTERIORHODOPSIN IN PURPLE MEMBRANE, BROWN HOLO‐MEMBRANE ANDL–1690‐SOLUBILIZED MONOMERS WITH HYDROXYLAMINE IN LIGHT AND THE DARK
Authors: Hamanaka Toshiaki , Hiraki Kenji , Kito Yuji
Published: January 2008

Abstract— The reactions of hydroxylamine with bacteriorhodopsin in the states of the purple membrane, the brown holo‐membrane andL–1690‐solubilized monomers were studied in light and the dark. The bleaching rate was strongly dependent on the state of the bacteriorhodopsin and largely enhanced by light. Analysis of the isomeric composition of the resultant retinaloximes by high performance liquid chromatography (HPLC) showed that more all‐trans retinaloximes were present in the dark than 13‐cis retinaloximes. However, under illumination, the relative amounts of 13‐cis retinaloximes increased greatly, indicating the occurrence of trans to cis isomerization during the photochemical cycle of bacteriorhodopsin. Molar extinction coefficients of 13‐cis retinaloximes were determined to estimate the isomeric composition of retinaloximes by HPLC analysis.
IRREVERSIBLE BINDING OF CHLORDIAZEPOXIDE TO HUMAN PLASMA PROTEIN INDUCED BY UV‐A RADIATION
Authors: Bakri A. , van Henegouwen G. M. J. Beijersbergen , Sedee A. G. J.
Published: January 2008

Abstract— In view of the phototoxicity of chlordiazepoxide (Librium®) the kinetics of the reaction in the presence of plasma proteins was studied for chlordiazepoxide upon UV‐A irradiation and for its oxaziridine in the dark. Two different methods were used to determine the extent of irreversible binding to protein (up to ∼ 50% was found for both situations). Kinetic data support the conclusion that the formation of oxaziridine from photoexcited chlordiazepoxide is the basic event making chlordiazepoxide phototoxic. The half life of oxaziridine is about 30 min even in the presence of a high concentration of plasma proteins, is in agreement with previous in vivo results, showing covalent binding not only to biomolecules of the UV‐A irradiated skin but also to those of inner organs, e.g. liver and kidneys.
EXTENDING CIRCULAR DICHROISM SPECTRA INTO THE VACUUM UV AND ITS APPLICATION TO PROTEINS
Authors: Johnson W. Curtis
Published: January 2008

Circular dichroism (CD) spectra measured into the vacuum UV region provide information necessary for this technique to fulfill its potential. In the case of proteins, CD spectra measured to 184 nm or below can be analyzed for secondary structure: generalized inverses make such analyses particularly simple. Generalized inverses for α‐helix, anti‐parallel β‐sheet, parallel β‐sheet, β‐turn, and “other” structures are given in tabular form. When the dot product of each inverse is taken with the digitized spectrum of a protein, the amount of corresponding secondary structure is predicted. However, protein CD spectra truncated above 184 nm give too little information to give reliable analyses. Furthermore, adding constraints only complicates this problem because unreliable analyses now appear good.
ON THE PRIMARY PHOTOPROCESS OF 124‐kdalton PHYTOCHROME
Authors: Eilfeld Peter , Eilfeld Petra , Rüdiger Wolfhart
Published: January 2008

The photoreaction between Pτ and the first detectable intermediate, lumi‐R, of 124‐kdalton oat phytochrome has been investigated at low temperatures. The temperature dependence of the quantum yields of the photoreactions, Pτ to lumi‐R and lumi‐R to Pτ, has been determined. From measurements over a temperature range from 119 to 155 K, an activation barrier of 3.6 ± 0.5 kJ mol 1 is found for the photoreaction of Pτ with 661‐nm actinic light. A higher value (5.7 ± 0.7 kJ mol ‐1) is found for the photoreaction of lumi‐R to Pτ. with 698‐nm actinic light. Increased quantum yields are found in deuterated buffer solutions at low temperatures. The activation energies for deuterated phytochrome (3.2 ± 0.7 kJ mol–1 for Pτ with 661‐nm irradiation and 6.2 ± 1.2 kJ mol‐1 for lumi‐R at 698‐nm irradiation) are identical within the limits of error with those of protonated phytochrome. The lack of a deuterium effect for the activation energies favors the Z,E‐isomerization rather than proton transfer or tautomerization for the chromophore photochemistry during Pτ⇄lumi‐R conversion.
CHLOROPHYLL PHOTOSENSITIZED ELECTRON TRANSFER IN PHOSPHOLIPID BILAYER VESICLE SYSTEMS: SECONDARY OXIDATION OF REDUCED VIOLOGEN ACCEPTORS BY Ru(NH3)63+
Authors: Ford William E. , Tollin G.
Published: January 2008

Abstract— The kinetics of the oxidation of a homologous series of 4,4′‐di(n‐alkyl)‐bipyridinium (viologen) radicals by Ru(NH3)63+ in vesicle suspensions was studied using laser flash photolysis. The viologen radicals were produced photochemically in the bilayer membrane phase of the vesicles by electron transfer from the triplet state of chlorophyll‐α. At high concentrations of Ru(NH3)63+, the rate of oxidation of the viologen radicals in the aqueous phase was limited by the rate at which the radicals diffused from the membrane to the aqueous phase. The exit rate constant decreased from 2 × 105 s−1 for the methyl viologen radical to 4 × 103 s−1 for the pentyl viologen radical. Both the exit rate constants and the calculated values for the equilibrium association constants of the viologen radicals were unexpectedly insensitive to the length of their alkyl substituents. This, as well as other data, suggests that the radicals that diffused into the aqueous phase tended to remain associated with the membrane‐water interface.
LIGHT INDUCED INTERACTION BETWEEN RHODOPSIN AND GTP DEPENDENT PROCESSES IN ROD OUTER SEGMENTS—I. KINETIC ANALYSES OF LIGHT SCATTERING TRANSIENTS
Authors: Gupta B. D. , Deshpande S. , Jones R. E. , Borys T. J. , Abrahamson E. W.
Published: January 2008

Abstract— A fast light‐induced light scattering transient in the presence of Mg2+ and GTP is observed from bovine rod outer segment suspension. This transient is studied at various temperatures, degrees of photo‐bleaching and GTP concentration. The kinetic analysis of this signal at low photo‐bleaching (∼ 5%) reveals two different processes which are consecutive rather than simultaneous. The rate of both processes depends upon the extent of photo‐bleaching and indicates that each process requires a photolyzed rhodopsin intermediate. At low temperature, the rate constant of both the processes increases with the extent of photo‐bleaching while at higher temperatures it decreases. The calculated activation energy of both processes decreases with increasing photo‐bleaching. It has also been observed that with decreasing GTP concentration, the rates of both processes decrease indicating that the two processes though first order are most likely bimolecular, first order in both GTP and the photolytic rhodopsin intermediate (metarhodopsin II)
THE MEASUREMENT OF DIHEMATOPORPHYRIN ETHER CONCENTRATION IN TISSUE BY REFLECTANCE SPECTROPHOTOMETRY
Authors: Patterson M. S. , Wilson B. C. , Feather J. W. , Burns D. M. , Pushka W.
Published: January 2008

The in vivo quantitation of local photosensitizer concentration is an important problem in photodynamic therapy because tumor response depends on this parameter. This paper describes a new method for measuring dihematoporphyrin ether (DHE) concentration by reflectance spectrophotometry—a technique which could be applied to other photosensitizers. The absorbance due to the 630 nm absorption peak of DHE was determined by obtaining diffuse reflectance spectra before and after the addition of DHE in the form of Photofrin II. Spectra were obtained by placing an optical fiber bundle source and single fiber detectors in contact with the tissue surface. The sensitivity of the technique was measured for three tissues in vitro with a range of optical properties as well as for Nutralipid—a liquid with a very high scattering to absorption ratio. The results were in qualitative agreement with the predictions of a diffusion model of light propagation although a systematic discrepancy was observed. The technique was also successfully demonstrated in vivo for VX‐2 carcinomas implanted in rabbit ears by correlating simultaneous absorbance measurements with gamma counting of radiolabeled 6‐4Cu Photofrin II. Our results suggest that reflectance spectrophotometry may be a useful clinical and research tool for the in vivo quantitation of DHE and other photosensitizers.
DIFFERENT PHOTOINACTIVATION MECHANISMS IN Propionibacterium acnes FOR NEAR‐ULTRAVIOLET and VISIBLE LIGHT
Authors: Kjeldstad Berit
Published: January 2008

The light sensitivity of Propionibacterium acnes was investigated when the cells were exposed to anoxia, sodium azide, D2O or superoxide dismutase in combination with visible light (broad band red light and 415 nm) and near‐ultraviolet irradiation (360 and 320 nm). During anoxia the cells became less sensitive when the irradiation wavelength increased. Oxygen increased the photodamage to a greater extent in the case of visible light than of near‐UV light. The photosensitization effects were, however, more or less oxygen dependent at all wavelengths used. An effect of azide and D2O on the light sensitivity was observed for visible light, while superoxide dismutase was effective only at 320 nm.

The results support the hypothesis that inactivation of P. acnes with near‐UV and visible light is based on different mechanisms. Porphyrin photosensitization, accomplished by singlet oxygen, is the most important mechanism when visible light is used. At shorter wavelengths (320 and 360 nm) singlet oxygen is not involved and for 320 nm the destruction might occur via superoxide anion formation.