bluuebunny/crossref_metadata_2025 huggingface dataset:
QUANTITATION OF THE PHOTOMUTAGENIC RESPONSE OF Salmonella TO AN EASTERN SHALE OIL AND FLUORESCENT LIGHT
Authors: Selby Christopher , Calkins John , Enoch Harry G.
Published: January 2008

The dose‐response relationship for photomutation (i.e. photosensitized mutation) by a shale‐derived oil was examined. The Ames’Salmonella typhimurium tester strain TA98 was exposed to several concentrations of an Eastern shale oil and UV‐visible radiation from illumination‐type fluorescent lamps. Reversion to histidine prototrophy and survival were assayed following various radiation doses. Reciprocity of shale oil concentration and radiation exposure over approximately 10‐fold ranges of oil concentrations and radiation doses was observed with revertant numbers per plate, percent survival, and the induced frequency of revertants (revertants per survivor). The relationship between mutation frequency and the product (shale oil concentration times radiation exposure) fit well with either a linear model or a power law model in which the frequency of induced mutations was described by the product dose raised to the 1.26th power. Similar dose‐response relationships provide potential criteria for comparing potency of photomutagenic substances, comparisons that may be valuable towards assessing, and perhaps modifying, risks imposed by human exposure to synthetic fuels.
ANTIBODIES TO UV IRRADIATED DNA: THE MONITORING OF DNA DAMAGE BY ELISA AND INDIRECT IMMUNOFLUORESCENCE
Authors: Wani Altaf A. , Gibson‐D'Ambrosio Ruth E. , D'Ambrosio Steven M.
Published: January 2008

Abstract The enzyme‐linked immunosorbant assay (ELISA) was modified to (1) characterize antibodies raised in rabbits against UV‐irradiated single‐stranded DNA (UVssDNA) complexed with methylated BSA and (2) directly detect pyrimidine dimers in irradiated DNA. The antisera specifically bound to UVssDNA, UVpoly(dT) and to a limited extent to UVdsDNA and UVpoly(dC) immobilized on protamine sulfate coated microliter wells. Fifty percent of the maximum antibody binding was observed at a 1‐5000 dilution against UVssDNA. Binding to ssDNA and poly(dT) was observed only at much higher concentrations of antibody (1:500 dilution), whereas no binding to double stranded DNA (dsDNA) was observed. The extent of binding of the antibody was dependent on the dose of UV radiation to DNA, as well as, to the concentration of antigen immobilized on the plate. Specific binding to DNA irradiated with 5.0 J/m2 was detected with as little as 10 ng of DNA. The sensitivity was further extended to less than 1 J/m2 by using higher concentrations (100 ng) of UVssDNA. The ability of various irradiated molecules, DNA, homopolymers and linkers to act as inhibitors of antibody binding establish that the antigenic determinants are mainly thymine homodimers with lower affinity for cytosine dimers. Potential usefulness of the antibodies to directly quantitate pyrimidine dimers in cells exposed to UV radiation was determined by indirect immunofluorescence. Flow cytometric analysis of immunostained human lymphocytes irradiated with 254 nm radiation indicated that greater than 50% of the population had significantly higher fluorescent intensity than unirradiated control cells.
ENHANCED REPLICATION OF DAMAGED SV40 DNA IN CARCINOGEN‐TREATED MONKEY CELLS
Authors: Maga Janet A. , Dixon Kathleen
Published: January 2008

Abstract Treatment of mammalian cells with certain chemical or physical carcinogens prior to infection with ultraviolet‐irradiated virus results in enhanced survival or reactivation of the damaged virus. To investigate the molecular basis of this enhanced reactivation (ER), we have examined Simian virus 40 DNA replication in carcinogen‐treated cells. We find that treatment of monkey kidney cells with N‐acetoxy‐2‐acetylamino‐fluorene or UV radiation 24 h prior to infection with ultraviolet‐irradiated Simian virus 40 leads to enhancement of viral DNA replication measured at 36 h after infection by [3H]thymidine incorporation or hybridization. The enhancement of DNA replication is observed when cells are treated from 1 to 60 h before infection or 1 to 16 h after infection. The fact that enhancement is observed also when cells are treated after infection rules out the possibility that enhancement occurs at the level of adsorption or penetration of the virus. Measurements of the time course of viral DNA replication indicate that pretreatment of cells does not alter the time of onset of viral DNA replication. We conclude from these studies that ER of Simian virus 40 occurs at the level of viral DNA replication.
EXCITON TRANSFER OUT OF OPEN PHOTOSYSTEM II REACTION CENTERS
Authors: Butler Warren L.
Published: January 2008

Abstract A simple photochemical model of photosystem II consisting of antenna chlorophyll and a reaction center was used to examine the phenomenon of exciton detrapping, i.e. the transfer of excitation energy from open reaction centers back to the antenna. η, the ratio of the probability of detrapping when the reaction centers are all open, Ψt(o) to the probability when the centers are closed, Ψt(x) was used as a variable parameter to examine the various pathways of energy dissipation in a system in which P, the yield of photochemistry, and R, the ratio of the maximum to the minimum yields of fluorescence, were assumed to be known (e.g. R= 4.0 and P= 0.90). It is shown that η must fall within a range of values between 0 and R (1 –P) and that, for given values of R and P, Ψt(o) and the ratio of the rate constant for photochemistry at the reaction center, kp, to the rate constant for energy transfer back to the antenna, kt, can be determined for any assumed value of η. Even though detrapping occurs at open reaction centers, it is the magnitude of the yield of nonradiative decay at closed reaction centers, Ψa(x) which sets the upper limit on η. Equations for the overall yields of fluorescence and nonradiative decay in the antenna chlorophyll and of nonradiative decay at the reaction center chlorophyll, under conditions of both open and closed reaction centers, were derived in conventional probability terms and in terms of R, P and η. As η increases within its range of permissible values, energy dissipation in the antenna decreases and nonradiative decay at the reaction center increases. The determination of a specific value of η or of the ratio kpkt would require additional information such as the value of the maximum yield of fluorescence and the ratio of the rate constants for fluorescence and nonradiative decay in the antenna chlorophyll. The characteristics of a system in which there is no nonradiative decay in the reaction center (i.e. kd= 0), in which case R (1 –P) = 1.0, were also examined. In this case the yield of detrapping has no influence on energy dissipation in the system. Finally, the question of heterogeneity in PSII was considered. It is suggested that Ψd(x) may be greater in PSIIβ than in PSIIα so that the probability of detrapping could be greater in the PSIIα fraction.
UTILIZATION OF HEAVY‐ATOM EFFECT QUENCHING OF PYRENE FLUORESCENCE TO DETERMINE THE INTRAMEMBRANE DISTRIBUTION OF HALOTHANE
Authors: Washington Kay , Sarasua Martha M. , Koehler Lynda S. , Koehler Karl A. , Schultz John A. , Pedersen Lee G. , Hiskey Richard G.
Published: January 2008

The interaction of halothane (CF3CHBrCl) with dipalmitoylphosphatidylcholine (DPPC) membranes containing varying amounts of dipalmitoylphosphatidylglycerol (DPPG) was examined via heavy atom effect quenching of pyrene fluorescence by halothane. The effect of halothane on pyrene fluorescence is consistent with a kinetic model based upon the assumption of the existence of two populations of pyrene in the membrane: one accessible to interactions with halothane; the second inaccessible to halothane on the time scale of the pyrene fluorescence excited state. Both populations of pyrene are affected by the presence of halothane in the membrane. The rate of halothane quenching of pyrene fluorescence is increased significantly for all DPPG/DPPC membranes compared to pure DPPC membranes indicating that any DPPG in the membrane facilitates interaction between halothane and pyrene even though the measured partition coefficients indicate that little change in total halothane concentration in the membrane as a whole occurs as a function of percent DPPG in DPPG/DPPC mixtures.

It is speculated that phase boundaries play an important role in determining the behavior of this model system by determining the location of the pyrene probe. The heavy atom effect quenching of pyrene by halothane provides a useful probe of phase boundaries in membranes.
AN ACTION SPECTRUM OF PHOTOREACTIVATING ENZYME FROM SEA URCHIN EGGS
Authors: Shiroya Tsugio , McElroy Douglas E. , Sutherland Betsy M.
Published: January 2008

An action spectrum for photoreactivating enzyme activity from unfertilized eggs of the sea urchin Hemicentrotus pulcherrimus was determined. The range of the spectrum is 313 to 500 nm, with a maximum at 365 nm. Comparison of this spectrum with that for photorecovery of developmental damage in the sea urchin embryo indicates the general similarity of the two processes.
ROSEOFLAVIN INHIBITION OF PHOTOCONIDIATION IN A Trichoderma RIBOFLAVIN AUXOTROPH: INDIRECT EVIDENCE FOR FLAVIN REQUIREMENT for PHOTOREACTIONS
Authors: Horwitz Benjamin A. , Malkin Shmuel , Gressel Jonathan
Published: January 2008

Roseoflavin, an analog known to compete with riboflavin in Lactobacillus casei, riboflavin‐deficient rats, and fungi, was used to ascertain whether a flavin plays a role as a sensitizing pigment for photomorphogenesis in the fungus Trichoderma. Roseoflavin inhibited blue light induced conidiation of a riboflavin‐requiring auxotroph of Trichoderma. Colonies pre‐incubated with roseoflavin needed six times more light to saturate conidiation. Roseoflavin did not change the dark rate of conidial development indicating that it interfered only with the photoact. A revertant from the riboflavin auxotroph strain was not inhibited by roseoflavin. Simultaneous addition of 10 μM riboflavin prevented inhibition by 6.4 μM roseoflavin. Thus, roseoflavin inhibition is probably specific, possibly replacing riboflavin or one of its metabolites in the light reactions. There was no detectable shift in the action spectrum towards the green where roseoflavin absorbs; thus it did not replace a flavin as an efficient photoreceptor.
FLUORESCENCE OF HOUSEFLY VISUAL PIGMENT
Authors: Stavenga D. G. , Franceschini N. , Kirschfeld K.
Published: January 2008

Abstract —The fluorescence of housefly photoreceptors was studied in vivo by using the deep pseudopupil technique. Whereas the rhodopsin R490 of the peripheral retinular cells fluoresces negligibly the metarhodopsin M580 fluoresces distinctly in the red. The newly discovered metarhodopsin M’is produced by intense blue light and can be reconverted into rhodopsin by intense long wavelength light. M’also fluoresces in the red; its excitation spectrum and emission spectrum peak at max= 570 and 660 nm respectively.

Intense ultraviolet light irreversibly reduces the visual pigment fluorescence as well as the broad band autofluorescence (kmnx 470 nm) originating from non‐visual pigments in the fly's eye.
PRIMARY PHOTOCHEMISTRY OF BACTERIORHODOPSIN: COMPARISON OF FOURIER TRANSFORM INFRARED DIFFERENCE SPECTRA WITH RESONANCE RAMAN SPECTRA
Authors: Rothschild Kenneth J. , Marrero Hector , Braiman Mark , Mathies Richard
Published: January 2008

Abstract —Fourier transform infrared (FTIR) difference spectra of the BR→rK transition in bacteriorhodopsin at 77→K are compared with analogous resonance Raman difference spectra obtained using a spinning sample cell at 77→K. The vibrational frequencies observed in the FTIR spectra of native purple membrane and of purple membrane regenerated with 15‐deuterioretinal are in good agreement with the frequencies observed in the Raman spectra, indicating that the lines in the FTIR difference spectra arise predominantly from retinal chromophore vibrations. This agreement confirms that the spinning cell method for obtaining resonance Raman spectra of K minimizes potential contributions from unwanted photoproducts. The unexpected similarity between the resonance Raman scattering intensities and the FTIR absorption intensities for BR and K is discussed in terms of the delocalized electronic structure of the chromophore. Finally, comparison of the Schiff base regions of the K Raman and FTIR spectra provide additional information on the assignment of its Schiff base vibration.
INDUCTION OF DNA–PROTEIN CROSS‐LINKING IN CHINESE HAMSTER CELLS BY MONOCHROMATIC 365 AND 405 NM ULTRAVIOLET LIGHT
Authors: HAN A. , PEAK M. J. , PEAK J. G.
Published: January 2008

Abstract— The survival, the induction of DNA‐protein cross‐linking, and the number of T4‐endonuclease sensitive sites were measured in Chinese hamster cells that had been irradiated with 365 and 405 nm monochromatic light. The survival measurements show that cells are somewhat less sensitive to 405 nm light than to 365 nm light. The difference is expressed predominantly in the shoulder widths of the survival curves, whereas the slopes of the two curves are about the same. Induction of pyrimidine dimers, as indicated by the number of endonuclease‐sensitive sites, after exposures that produce about 10% survival is very low at 365 nm (˜ 4 endonuclease sites per 2 × 108 daltons), while no dimers are detected at 405 nm. In contrast, DNA‐protein cross‐links are induced rather effectively at either wavelength even after exposures that result in a relatively high survival (60‐20%). Our measurements support the conclusion that lethality in mammalian cells after irradiations with 365 or 405 nm light is caused by a nondimer damage, possibly DNA‐protein cross‐links.
PHOTOELECTRON AND ULTRAVIOLET ABSORPTION SPECTRA OF THE ENAMINES OF A SERIES OF SIMPLE POLYENES
Authors: DUPUIS P. , SANDORFY C. , VOCELLE D.
Published: January 2008

Abstract— The photoelectron and ultraviolet absorption spectra of a series of enamines containing one, two or three double bonds have been determined. In all cases. the ionízation potential and lowest frequency absorption bands are at considerably lower energies than for the corresponding imines (Schiff bases). It is suggested that these facts should be taken into account when the structures of the various intermediates in the cycles of rhodopsin and bacteriorhodopsin are assessed.
FIBER‐OPTIC PLANT TISSUES: SPECTRAL DEPENDENCE IN DARK‐GROWN AND GREEN TISSUES*
Authors: MANDOLI DINA F. , BRIGGS WINSLOW R.
Published: January 2008

Abstract— The fiber‐optic properties of etiolated plant tissues can be used to detect and characterize pigment absorption in vivo. Transmission spectra of light guided through several monocot and dicot etiolated tissues show a decreasing red/far red ratio with increasing tissue length. Absorption bands attributable both to vacuolar pigments such as anthocyanins and to chloroplast pigments lead to the conclusion that the guided light passes through both vacuole and cytoplasm. As etiolated tissue becomes green under white light treatment, the red/far red ratio also changes, the nature of the change depending upon the tissue involved. The blue/red ratio also changes both with increasing length of etiolated tissue and during the greening process, with the changes again dependent on the tissue involved. The spectral dependence of the light‐guiding phenomenon in dark grown and green plants may have implications for physiological responses mediated by phytochrome.
THE INDUCTION OF ERYTHEMA, EDEMA, and THE POLY AMINE SYNTHESIS ENZYMES ORNITHINE DECARBOXYLASE and S‐ADENOSYL‐L‐METHIONINE DECARBOXYLASE IN HAIRLESS MOUSE SKIN BY PSORALENS and LONGWAVE ULTRAVIOLET LIGHT
Authors: Connor Michael J. , Lowe Nicholas J.
Published: January 2008

Abstract— The cutaneous toxicities of the furocoumarins 8‐methoxypsoralen (8‐MOP), 5‐methoxypsoralen (5‐MOP), 3‐carbethoxypsoralen (3‐CP), and 5‐methylisopsoralen (5‐MI) administered topically (2 or 4 mg) or orally (25 mg/kg) followed by irradiation with longwave ultraviolet light (UVA) (50 kJ/ m) were compared in hairless mice. Parameters measured were the induction of ornithine decarboxylase (ODC) activity, a potential marker for skin‐carcinogens, S‐adenosyl‐L‐methionine decarboxylase, (SAMDC) activity, and the induction of skin edema (increase in dorsal skin fold thickness) and erythema, both indicators of acute phototoxicity.

Edema and erythema, and epidermal ODC activity were induced by topical and oral 5‐MOP, 8‐MOP and 5‐MI when given with UVA. The erythema found after topical 5‐MI + UVA was less than after 8‐MOP + UVA or 5‐MOP + UVA. and first occurred at 48 h. Edema and epidermal ODC activity were also induced at later times, being maximal at 48 h or more. 3‐Carbethoxypsoralen given orally (25 mg/kg) or topically (4 mg) with UVA did not have a consistent effect on the parameters measured, and appeared to be non‐toxic under these conditions.

These results of these studies suggest that the low toxicity of 3‐CP + UVA is not necessarily related to its ability to form only monoadducts with DNA. The ability to crosslink with DNA is not a prerequisite for ODC induction and the induction of skin edema since 5‐MI, which can only form monoadducts with DNA, gave a similar response to 8‐MOP and 5‐MOP.
PHOTOINDUCED OXYGEN CONSUMPTION IN MELANIN SYSTEMS–II. ACTION SPECTRA and QUANTUM YIELDS FOR PHEOMELANINS
Authors: Sarna T. , Menon I. A. , Sealy R. C.
Published: January 2008

Abstract— Photoinduced oxygen consumption in systems containing synthetic and natural pheomelanins has been studied by ESR spectroscopy using a nitroxide spin probe to monitor oxygen concentration. Action spectra and quantum yields have been determined for melanin from 5‐S‐cysteinyldopa and for pheomelanins extracted from red human hair and red chicken feathers. For comparison, data also were obtained for eumelanins from black hair and black feathers. The action spectrum for oxygen consumption by cysteinyldopa melanin is closely related to that previously obtained for eumelanins except that it shows slightly less efficiency at intermediate wavelengths (ca. 300–400 nm). Action spectra for the natural pheomelanins resemble either that for cysteinyldopa melanin or that for eumelanin. In general pheomelanins are no more effective than eumelanins in promoting oxygen consumption, i.e. they are no more susceptible to net photooxidation.
PHOTOBIOLOGICAL ACTIVITY OF 4‐METHYLPSORALEN and 4‐METHYL‐4‘,5’‐DIHYDROPSORALEN WITH RESPECT TO LETHAL and MUTAGENIC EFFECTS ON E. coli, and PROPHAGE INDUCTION
Authors: Fujita Hitoshi
Published: January 2008

Abstract— The lethal and mutagenic effects on E. coli as well as the induction of prophage lambda were determined after treatment with 4‐methylpsoralen, 8‐methoxypsoralen, psoralen or 4‐methyl‐4′,5′‐dihydropsoralen and UV‐A irradiation. All psoralens used caused photokilling and photomutagenesis of strains H/r30R and Hs30R. 4‐Methylpsoralen was more efficient for killing and for the induced mutation than 8‐methoxypsoralen or psoralen in view of the dose modification factor. This finding can be explained by the methylation effect of psoralen. 4‐Methylpsoralen induced more mutation in Hs30R than in H/r30R. Monofunctional 4‐methyl‐4′,5′‐dihydropsoralen required much higher fluence than bifunctional psoralens to kill cells and to induce the mutation. When the induced mutation frequency was expressed as a function of survival, mutagenic efficiency ranked in the following order: 8‐methoxypsoralen > psoralen > 4‐methylpsoralen > 4‐methyl‐4′,5′‐dihydropsoralen. 4‐Methylpsoralen was 3–4‐fold less mutagenic than 8‐methoxypsoralen in this plot. Lytic growth of prophage in E. coli AB1157 (ñ) was induced by the treatment. When the bifunctional psoralens were used, the maximum induced fraction was larger than 20%. However, it was only 2% when 4‐methyl‐4′,5′‐dihydropsoralen was used.
SODIUM AZIDE AFFECTS METHYLENE BLUE CONCENTRATION IN Salmonella typhimurium and Saccharomyces cerevisiae
Authors: Koch Walter H. , Bass GEorge E.
Published: January 2008

Abstract— Since 1974, the quenching effect of azide (N3‐) has been widely used to infer participation of excited singlet oxygen (1O2) as a major reactive species in microbial photodynamic action studies. We report herein that N3‐ causes a rapid, concentration‐dependent release of at least one heterocyclic aromatic photosensitizer, methylene blue, from Salmonella typhimurium. A similar phenomenon of lesser magnitude was also observed in Saccharomyces cerevisiae. This process may account in part for the azide photoprotective effects in vivo.
OXYGEN‐DEPENDENT PHOTOSENSITIVITY and MITOTIC RECOMBINATION IN THE SMUT FUNGUS Ustilago violacea
Authors: Will Oscar H.
Published: January 2008

Abstract— The effect of high intensity incandescent radiation on survival and mitotic recombination in the phlph+ diploid strain of Ustilago violacea was studied with and without atmospheric O2. In the presence of atmospheric O2, strain phlph+ was characterized by photokilling to approximately 50% survival, and induction of mitotic recombination to about 60% by 90 min of light exposure. No photokilling and little induction of mitotic recombination were observed when light exposure was carried out in an 02 depleted environment. Photokilling and photo‐induced mitotic recombination in U. violacea may be due to DNA damage or repair in response to a photosensitized reaction, involving an endogeneous photosensitizer.
LASER DOPPLER VELOCIMETRY TO QUANTIFY UV‐B INDUCED INCREASE IN HUMAN SKIN BLOOD FLOW
Authors: Young A. R. , Guy R. H. , Maibach H. I.
Published: January 2008

Abstract—A laser Doppler velocimeter was used to quantify changes in cutaneous blood flow, in human subjects, after exposure to UV‐B radiation. Studies with three subjects showed a peak increase in flow at 6 h post‐irradiation. Dose‐response studies, on 8 subjects, at 24 h post‐irradiation showed that blood flow increased linearly with log UV‐B dose over a range of about 0.5 to 5 MED. Comparative studies with pigmented and non‐pigmented skins gave a quantitative measure of the photoprotective effect of melanin. The main advantage of the laser Doppler technique is that it allows easy quantification of a vascular response. However, there was no advantage when compared with detection of a visually determined threshold response,viz.a barely perceptible erythema.
FUNCTIONAL PROPERTIES OF CATTLE RHODOPSIN IN SOLUBLE COMPLEX WITH PHOSPHOLIPIDS and DEOXYCHOLATE
Authors: Okada Daisuke , Tsukida Kiyoshi , Ikai Atsushi
Published: January 2008

Abstract— The necessary conditions of bleached rhodopsin to activate GTPase and to regenerate α‐band were studied by changing the number of bound phospholipids to rhodopsin using gel filtration procedure. The number of bound phospholipids per mole of rhodopsin (bPL/rho) in the eluants was reproducibly controlled by the concentration of sodium deoxycholate (DOC) in the elution buffer. The eluants were soluble complexes composed of rhodopsin with original a‐band, disk phospholipids and DOC. The regenerability of α‐band depended on bPL/rho but neither on the concentration of DOC nor on state of aggregation of rhodopsin. The lowest number of bPL/rho for this activity under our experimental conditions was estimated to be30–50 in bPL/rho. GTPase was activated only by such complexes that had a nearly original quantity of bPL/rho in disk membranes. Other complexes with less bPL/rho showed aggregation upon bleaching and did not activate GTPase. The amount of phospholipids present in the disk membranes is sufficient to prevent aggregation of rhodopsin upon bleaching.
CONFORMATIONS OF DEOXYDODECANUCLEOTIDES WITH PYRIMIDINE (6‐4) PYRIMIDONE PHOTOADDUCTS
Authors: Rao Shashidhar N. , Kollman Peter A.
Published: January 2008

Abstract— We have carried out molecular mechanical simulations of dodecanucleotide d(CGCGAAXYCGCG).d(CGCGX'Y'TTCGCG) with XY being CC, TC, TT and CT and X'Y'being their corresponding base paired dinucleotides on the complementary strand. Simulations were also carried out with the corresponding pyrimidine (6‐4)‐pyrimidone photoadducts incorporated in these dodecanucleotides. As in the case of the cyclobutane dimer incorporated dodecanucleotide structures (Rao et al., 1984), those regions of the DNA modified by6–4 pyrimidine adducts are found to undergo little conformational changes except in the dimer region. The conformational characteristics of the6–4 pyrimidine adduct incorporated structures seem to be influenced by the nature of the base at the 3' end of the dimer. Specifically, favorable hydrogen bonding interactions between the 5' end base and its preceding phosphate group are present in structures which have cytosine at the 3' end of the photodimer. The energetics of these structures relative to those without incorporated dimers have been discussed and the results have been analysed in the light of the currently prevalent ideas on the role of the6–4 photoadducts in mutagenesis in various organisms.
SINGLET OXYGEN PRODUCTION BY SOME FUROCOUMARIN DERIVATIVES IN THE PRESENCE OF DNA: TIME RESOLVED LUMINESCENCE MEASUREMENTS
Authors: Beaumont Paul C. , Rodgers Michael A. J. , Parsons Barry J. , Phillips Glyn O.
Published: January 2008

Abstract—The yield of singlet oxygen (1Δg) from some furocoumarins in the presence of DNA has been measured using time resolved techniques. For both psoralen and 4'‐aminomethyl‐4,5',8‐trimethylpsoralen, increasing DNA concentration leads to a decrease in the yield of singlet oxygen. In addition, there is a linear dependence between the yield of singlet oxygen and the observed triplet yield determined by laser flash photolysis. In view of this observation it seems unlikely that singlet oxygen production occurs from these two furocoumarins when they are complexed with DNA. Preliminary, albeit inconclusive, results for 8‐methoxypsoralen are also presented.
A DIMERIC MECHANISM FOR THE ACTION OF PHYTOCHROME: EVIDENCE FROM PHOTOTHERMAL INTERACTIONS IN LETTUCE SEED GERMINATION*
Authors: VanDerWoude William J.
Published: January 2008

Abstract— Sensitization of the phytochrome‐mediated germination at 20°C of lettuce seeds (Lactuca sativa L. cv. Grand Rapids) by pretreatment at 4°C, 28°C, or on 1% ethanol, was studied. The 660 nm fiuence‐response characteristics were similarly biphasic for all sensitizing treatments and displayed responses at very low fluences (VLFR) as well as responses characteristic of non‐sensitized seeds at 10000‐fold higher, low fluences (LFR). Maximum VLFR increased with the duration of sensitizing treatments. However, the fluence ranges required for the two types of responses remained relatively constant. These and additonal responses of sensitized seeds to 730 nm fluences were compared to simulations of a mechanism involving a receptor, X, and based on the dimeric structure of phytochrome in which each monomer is independently phototransformed from the inactive (Pr) to the active (Pfr) form. The fluence requirements for phytochrome photoconversion in seeds were determined to be similar to those of purified Avena phytochrome in vitro, on which photochemical parameters for the simulations were based. The analyses suggest that Pr:Pfr‐Xand Pfr:Pfr‐X are responsible, respectively, for the VLFR and the LFR, and that sensitization involves membrane influences on the activity of Pr:Pr‐X. They also suggest the concentration of X to be about 0.001 that of total phytochrome dimer in this system.
KINETIC SEPARATION OF PHOTOTROPISM FROM BLUE‐LIGHT INHIBITION OF STEM ELONGATION*
Authors: Cosgrove Daniel J.
Published: January 2008

Abstract— These experiments tested the hypothesis that phototropic bending arises when a light gradient across the stem differentially inhibits cell elongation because of direct inhibition of cell elongation by light (the Blaauw hypothesis). Continuous irradiation of dark‐grown cucumber seedlings (Cucumis sativus L.) with unilateral blue light inhibited hypocotyl elongation within 30 s, but did not induce phototropic curvature until 4.5 h after the start of irradiation. Marking experiments showed that curvature began simultaneously at the top and bottom of the growing region. In situ measurements of the light gradient across the stem with a glass fiber optic indicated that a 5‐ to 6‐fold difference in fluence rate was established on the two sides of the stem. The light gradient established at the start of irradiation was the same as that after 6 h of irradiation. Changes in gravitropic responsiveness during this period were also ruled out. Calculations show that the light gradient should have caused curvature which would be detectable within 30 to 60 min and which would extrapolate to the start of irradiation–if the Blaauw hypothesis were correct. The long lag for phototropism in this case indicates that rapid inhibition of cell elongation by blue light does not cause the asymmetrical growth of phototropism. Rather, phototropism is superimposed upon this separate light growth response.
PHOTOPHYSICAL STUDIES OF PYRENE INCORPORATED IN NAFION MEMBRANES*
Authors: Lee Plato C. , Meisel Dan
Published: January 2008

Abstract— High concentrations of organic chromophores, in particular pyrene, were found to incorporate into the cluster network of water swollen Nation. The vibrational structure of the fluorescent molecule and its fluorescence lifetime were used to probe the location of pyrene in this structure. Strong heavy‐atom induced room temperature phosphorescence was observed from the chromophore in the water swollen membrane. Excimer formation in tm‐butanol swollen Nation was observed and was utilized to estimate the micro viscosity in this system.
SINGLET OXYGEN GENERATION BY HEMATOPORPHYRIN IX, UROPORPHYRIN I and HEMATOPORPHYRIN DERIVATIVE AT 546 nm IN PHOSPHATE BUFFER and IN THE PRESENCE OF EGG PHOSPHATIDYLCHOLINE LIPOSOMES
Authors: Blum Aleksander , Grossweiner Leonard I.
Published: January 2008

Abstract— The quantum yield of singlet oxygen generation (φ) was measured at 546 nm with the p‐nitrosodimethylaniline (RNO) method. The results obtained in pH 7.4 phosphate buffer (PB) were: φ(HP) = 0.44 ± 0.05: φ= 0.71 ± 0.07: φ(HpD‐A) = 0.06 ± 0.02. The value of φ was constant from 3 to 67 μM, attributed to the dominance of HP dimers; φ (HP) increased to 0.77 ± 0.13 in the presence of small egg phosphatidylcholine liposomes (SUV), attributed to solubilization and monomerization: φ (HpD‐A) increased to 0.87 ± 0.17 in the presence of SUV. attributed to monomerization of the impurity porphyrins and unfolding of the covalent dimer constituents. The quantum efficiency of the RNO system (100 μM RNO plus 10 mM histidine) was approximately 0.015 at pH 7.4 and increased significantly at lower pH.
CONFORMATIONAL FLUCTUATIONS IN ∝aL‐CHYMOTRYPSINOGEN A POWDERS
Authors: Fucaloro Anthony F. , Forster Leslie S.
Published: January 2008

Abstract— The average fluorescence lifetime for the tryptophan excited state decay in a‐chymotrypsinogen A is independent of hydration up to 0.15 g H2O/g protein. A sharp decrease in lifetime occurs between 0.15 and 0.18 g H2O/g protein, followed by a gradual decrease toward the solution value. This behavior, in a protein where the exposure of the tryptophans to solvent is minimal, is in marked contrast to that observed in bovine serum albumin where at least one of the two tryptophans can interact directly with water.
THE PHOTODYNAMIC EFFECTS ONV–79 CHINESE HAMSTER CELLS
Authors: Bhattacharjee Sukhendu B. , Ganguly Tapan , Bhaumik Gayaram
Published: January 2008

Abstract— Holding of acriflavine sensitizedV–79 cells in growth medium before visible light exposure decreases inactivation by visible light. The decrease depended upon the period of holding, indicating that there was release of cellular dye during this period. Exposures to visible light were done in two conditions: (a) with no dye in the medium during visible light exposure (washed) and (b) with dye in the medium during exposure (unwashed). Caffeine was found to slightly increase the sensitivity of the cells to visible light in the washed condition, whereas, in the unwashed condition no such effect was observed. Interaction studies with far UV did not reveal any correlation between photodynamic damage and UV damage. Visible light exposure of acriflavine sensitized cells was found to be mutagenic, as studied from the induction of 8‐azaguanine resistant mutants. Inhibition of singlet oxygen production by sodium azide suppressed the induction of mutants. All these, taken together, have been discussed with respect to the relative importance of DNA and non‐DNA damage in the photodynamic action of acriflavine.
RELATIONSHIP BETWEEN LIGHT‐INDUCED STATE I/II‐TRANSITIONS and Mg2+‐EFFECT ON FLUORESCENCE, TESTED IN SYNCHRONOUS CULTURES OF Scenedesmus obliquus
Authors: Krupinska Karin , Akoyunoglou George , Senger Horst
Published: January 2008

Abstract—Light induced transition of the photosynthetic apparatus from state II to state I by preillumination with PS I lightin vivoand the addition of cations to chloroplasts or chloroplast particles prepared in low‐salt buffer have rather similar effects on the fluorescence properties at room temperature and at 77 K. Using synchronous cultures ofScenedesmus obliquus,we were able to study both phenomena in parallel in different developmental stages under well defined conditions. Both phenomena show an inverse course during ontogenetic development ofS. obliquus.This result suggests that Mg2+ions and PS I light don't necessarily act in the same way. Hence, changes in the ionic environment cannot be the unique basis of light induced state changes within the photosynthetic apparatusin vivo.
CHROMOPHORE ROTATION IN 124‐kD ALTON A vena sativa PHYTOCHROME AS MEASURED BY LIGHT‐INDUCED CHANGES IN LINEAR DICHROISM
Authors: Ekelund Nils G. A. , Sundqvist Christer , Quail Peter H. , Vierstra Richard D.
Published: January 2008

Abstract— From light‐induced changes in linear dichroism, we have calculated the rotation of the long‐wavelength‐absorbing transition moment that occurs during phototransformation of 124‐kilodalton Avena sativa phytochrome. Phytochrome was purified to homogeneity and immobilized onto Sepharose beads covalently coated with antibodies against A. sativa phytochrome. Changes in linear dichroism were induced by plane‐polarized red or far‐red light and measured by the absorbance differences at 660 and 730 nm using a dual‐wavelength spectrophotometer equipped with polarizing filters in the measuring beams. From such measurements, we calculate a rotation angle of 31o (or 149o) during photoconversion of Pr to Pfr and 30o (or 150o) during photoconversion of Pfr to Pr. These values are similar to the value of 32o (or 148o) reported earlier for the rotation of the transition moment of “large”A. sativa phytochrome (? 120 kilodalton) isolated under conditions that did not preclude post homogenization proteolysis of the 124 kilodalton molecule.
PHYTOCHROME MODELS, PART 9. CONFORMATION SELECTIVITY OF THE PHOTOCYCLIZATION OF THE BILIVERDIN IX γ and IX δ DIMETHYL ESTERS*
Authors: Braslavsky Silvia E. , Al‐Ekabi Hussain , Petrier Christian , Schaffner Kurt
Published: January 2008

Abstract— The photocyclization of the biliverdin IX γ and IX δ dimethyl esters to phorcabilin and neobiliverdin IX δ dimethyl ester, respectively, markedly depends on the irradiation wavelength within the first electronic absorption band. The quantum yields of reaction are highest on irradiation at575–600 nm. As judged from fluorescence excitation studies, absorption by the stretched conformations of the biliverdins is relatively important at these wavelengths. At longer wavelengths, where the reaction efficiency sharply declines, absorption by the coiled form predominates. Based on these findings and on supporting evidence from the solvent and temperature influence on the reaction, the photocyclization is proposed to occur selectively from a stretched conformation (an example of the principle of nonequilibration of excited rotamers), competing with E‐Z isomerization of the centralC–10 double bond. A kinetic hydrogen isotope effect on the photochemical reaction rate of N,N,N‐trideuteriated biliverdin IX δ dimethyl ester indicates that the primary photoproduct in the cyclization reaction is labile and reacts via two competing processes: reopening to the starting material and a solvent‐mediated proton shift. The latter process leads to the phorcabilin and neobiliverdin IX δ esters. The results suggest, as a general rule, that the stretching of coiled biliverdins is confined to thermal and photochemical transformations within the B/C partial structure, while the Z‐syn geometry of the A/B and C/D moieties is retained.
A FLAVOPROTEIN IN Phycomyces blakesleeanus WITH SHORT FLUORESCENCE LIFETIME
Authors: Pollock John A. , Lipson Edward D.
Published: January 2008

Abstract— The photoreceptor system for the blue‐light‐induced phototropism in the fungus Phycomyces blakesleeanus includes one or more flavin chromophores, probably located in the plasma membrane of the sporangiophore. From a plasma‐membrane fraction of short synchronous sporangiophores, we have enriched, by column chromatography, specific proteins with covalently bound flavins. These flavoproteins were analyzed by a fluorescence lifetime assay. Flavoproteins with fluorescence lifetimes significantly less than 5 ns have been predicted to be involved in blue‐light reception. We studied samples from a wild type strain and from the night‐blind mutant LI. (genotype madC). For the enriched flavoprotein samples, we found predominant fluorescent components with lifetimes of 1.5 ns (74%) for wild type and 1.8 ns (83%) for LI. According to this assay, one or both of these flavoproteins are likely components of the blue‐light photoreceptor system in P. blakesleeanus.
ENHANCEMENT OF INTRINSIC ANTITUMOR ACTIVITY IN SPORE‐ENDOTOXIN MIXTURES OF Bacillus thuringiensis BY EXPOSURE TO ULTRAVIOLET RADIATION
Authors: Zamola B. , Karminski‐Zamola G. , Fuks Zê. , Kubovicê M. , Wrischer M.
Published: January 2008

Abstract— Irradiation of spore‐endotoxin mixtures from Bacillus thuringiensis cultures at 254 nm (60 μW cm‐2) enhances their intrinsic antitumor potency as well as that of either component. The extent of enhancement depends on the length of exposure (optimum: 35 min) and may thus be due to photochemical changes of the endotoxin protein or/and to photoproduction of additional compounds with antitumor activity. Antitumor effects, expressed as survival rates of C57BL/6 mice inoculated with Lewis' mouse lung carcinoma and subjected to treatments 24 h later, depended on the number of doses of preparations administered (mixture, separated components).
A PHOTOACOUSTIC STUDY OF MORPHOLOGICAL CHANGES OCCURRING IN PLANT TISSUE CULTURES ACCOMPANYING DIFFERENTIATION
Authors: Farringer Eric L. , O'Hara Ellen P. , Moore Thomas A.
Published: January 2008

Abstract— Melampodium leucanthum (Torr. and Gray) leaves were disinfested and explanted upon a callus inducing medium. Changes accompanying the process of differentiating into callus were monitored photoacoustically and included decreases in cuticular depth and pigmentation in the mesophyll layer.
PHOTOPHYSICS IN LIQUID CRYSTALS. FLUORESCENCE BEHAVIOR OF CHLOROPHYLL‐a IN DODECYLCYANOBIPHENYL
Authors: Subramanian R. , Patterson L. K. , Levanon H.
Published: January 2008

Abstract—Fluorescence behaviour of chlorophyll‐ain a liquid crystalline medium, dodecyl cyanobiphenyl, has been investigated as a function of temperature and concentration. At concentrations of 6 times 10‐4M, emission in the Q‐band region exhibited peaks in the crystal at 650,695 and 735 nm as well as the monomer band at 675 nm. Dilution studies indicate that these additional bands probably arise from aggregation of the chlorophyll.
PHOTOELECTRIC EFFECTS FROM CHLOROPHYLL a IN BILAYER MEMBRANES
Authors: Arrieta Rodolfo T. , Arrieta Iris C. , Pachori Pappi M. , Popp Ann E. , Huebner Jay S.
Published: January 2008

Abstract—Light flashes generated voltage transients across bilayer membranes in air‐saturated solutions which had chlorophylla(Chia) incorporated from one side. No other membrane or solution asymmetry was required. Symmetrical membranes containing Chiaalso produced photovoltages after transmembrane NaCl gradients were established, and large membrane conductance changes when irradiated in the presence of Nal. The latter two effects were reduced when the oxygen tension was reduced, and are consistent with photoionization of Chiaproducing porphyrin radicals and superoxide. Other oxidizing agents, CuS04, FeCl3, K3Fe(CN)6, (NH4)2Ce(N03)6and S‐(2‐methyl‐l,4‐naphthquinonyl‐3)‐gutathione, increased the photoelectric effect's amplitudes when they came into contact with Chia.The quantum efficiency with 5 mMK3Fe(CN)6was estimated by the dual flash method to be 0.2 ± 0.1.
SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS–VIII. A SPIN‐TRAPPING STUDY OF LIGHT INDUCED FREE RADICALS FROM CHLORPROMAZINE and PROMAZINE
Authors: Motten Ann G. , Buettner Garry R. , Chignell Colin F.
Published: January 2008

Abstract— The clinically important phenothiazine drugs, particularly chlorpromazine, often elicit phototoxic and photoallergic reactions. We have used the spin traps 2‐methyl‐2‐nitrosopropane (MNP) and 5,5‐dimethyl‐pyrroline‐N‐oxide (DMPO) to define the radical photolysis pathways of chlorpromazine and promazine. In the absence of oxygen the dechlorination product of chlorpromazine is trapped by MNP. The reactivity of the dechlorination product is similar to that of the phenyl radical as shown by its ability to extract hydrogen atoms from donors. Our results suggest that the dechlorination product is sufficiently reactive to account for the observation that chlorpromazine is more phototoxic than its parent promazine. In the presence of oxygen both chlorpromazine and promazine form a superoxide‐dismutase‐insensitive oxygen‐centered intermediate which, when trapped by DMPO, rapidly decays to DMPO‐OOH and subsequently to DMPO‐OH. In addition, chlorpromazine readily undergoes photoelectron ejection only when it is excited into the second excited singlet state (Δ < 280 nra). This previously unknown wavelength dependence of photoionization should be considered in establishing the mechanism of chlorpromazine photosensitization.
FAILURE OF UVR DOSE RECIPROCITY FOR SKIN TUMORIGENESIS IN HAIRLESS MICE TREATED WITH 8‐METHOXYPSORALEN
Authors: Gibbs N. K. , Young A. R. , Magnus I. A.
Published: January 2008

Abstract— 8‐Methoxypsoralen (8‐MOP) phototumorigenesis was studied in hairless albino mice irradiated with solar simulated radiation (SSR). Animals were exposed to three different daily doses of SSR after application of an oily vehicle with or without 8‐MOP. Tumor production was dependent on daily SSR dose irrespective of topical treatment. The phototumorigenic potency of SSR was increased by the vehicle and to a much greater extent by inclusion of 8‐MOP. Irrespective of topical treatment, a failure in dose reciprocity for tumorigenesis was demonstrated; in terms of cumulative SSR dose, the lower daily doses were more tumorigenic than the higher doses. This reciprocity failure in 8‐MOP photosensitized mice is similar to that previously observed for UV‐B phototumorigenesis. The relevance of these findings to therapeutic use of psoralens is discussed.
KINETIC MODELING OF TIME‐RESOLVED FLUORESCENCE IN SPINACH CHLOROPLASTS
Authors: Berens Sylvia J. , Scheele Jurgen , Butler Warren L. , Magde Douglas
Published: January 2008

Abstract—Time‐resolved fluorescence decay profiles following picosecond excitation of plant chloro‐plasts or algae are now being measured with high precision and reproducibility. A number of suggestions have been put forward to explain the complex decay kinetics which are observed. In this paper three models are defined explicitly, solved rigorously, and compared in detail with experimental data. The complete description of energy transport in chloroplasts is no doubt very complicated, and only such quantitative comparisons will make it possible to decide which models are consistent with experiments. Of the three models examined, only the heterogeneous bipartite model has solutions which agree with commonly agreed upon features of the data. It offers, therefore, one starting point for more elaborate models and a guide to the design of further experiments.
REMOVAL OF PYRIMIDINE DIMERS IN UV‐IRRADIATED SPORES OF Dictyostelium discoideum DURING GERMINATION
Authors: Okaichi Kumio , Tano Keizo , Ohnishi Takeo , Nozu Keiichi
Published: January 2008

Abstract—

The spores of Dictyostelium discoideum TW‐8 (radC) are about twice as sensitive to UV than the parental strain NC‐4 spores at a 10% survival level. Ultraviolet irradiation apparently suppressed the emergence of amoebae from swollen TW‐8 spores as compared with NC‐4 spores, though the conversion of spores into swollen spores was not affected by UV irradiation in either strain. About 85% removal of pyrimidine dimers was detected in UV‐irradiated NC‐4 spores at 200 J/m2 during spore germination for 9 h, but no removal of pyrimidine dimers was detected in TW‐8 spores under the same conditions. The removal of pyrimidine dimers from the NC‐4 spores began at around 2 h germination when the spores have become swollen. The number of enzyme‐sensitive sites (ESS) detected by Micrococcus luteus endonuclease in the DNA of UV‐irradiated NC‐4 spores also began to decrease at about 2 h into germination. The decrease in ESS, however, was hardly detectable in UV‐irradiated TW‐8 spores at any step during germination.

Cycloheximide inhibited both decrease in the number of pyrimidine dimers, and decrease in the number of ESS of UV‐irradiated NC‐4 spores. It is suggested that UV‐specific endonuclease is newly synthesized in swollen spores of NC‐4.
NOVEL PHOTOCLEAVABLE PROTEIN CROSSLINKING REAGENTS AND THEIR USE IN THE PREPARATION OF ANTIBODY‐TOXIN CONJUGATES
Authors: Senter Peter D. , Tansey Marilyn J. , Lambert John M. , Blattler Walter A.
Published: January 2008

Abstract— Two photolabile heterobifunctional protein crosslinking reagents have been synthesized and used for the conjugation of a protein toxin to an antibody. o‐Nitrobenzyl alcohol derivatives containing protected sulfhydryl groups were converted to o‐nitrobenzyloxycarbonyl chlorides and covalently attached to pokeweed antiviral protein (PAP‐S) obtained from the seeds of Phytolacca americana. The sulfhydryl groups were deprotected and the modified toxins were reacted with J5 antibody (specific for the common acute lymphoblastic leukemia antigen, CALLA) that had been functionalized with maleimido groups. Antibody‐toxin conjugates were formed predominantly in the ratio of 1:1, and were purified from unconjugated antibody and PAP‐S. Irradiation of the conjugates with light having a peak intensity at 365 nm effected photolytic fragmentation, and PAP‐S was released in fully active form. The methods described here may prove useful for the release of drugs or toxins at sites accessible to light.
SPECIFIC SOLVATION OF CHLOROPHYLL a: SOLVENT NUCLEOPHILITY, HYDROGEN BONDING AND STERIC EFFECTS ON ABSORPTION SPECTRA
Authors: Renge I. , Avarmaa R.
Published: January 2008

Abstract— The characteristics of chlorophyll a visible absorption spectra have been analyzed in terms of empirical solvent scales of Lewis basicity (B) and acidity (E) as well as steric constants (Es) (after Koppel and Palm, 1972; Palm, 1977). The presence or absence of the specific four‐band structure in the long‐wavelength region depends only on the solvent electron‐pair donating capability. In protic solvents the Soret band intensity is suppressed, but, in contrast, the extinction coefficient of its first satellite remains practically constant. This allows us to group spectra into four types according to the Soret‐band intensity and the structure of the red‐band system and assign them to chlorophyll‐solvent complexes formed via 1 or 2 donor‐acceptor bonds to central Mg and with and without hydrogen bond(s) to some nucleophilic center of the solute molecule.