bluuebunny/crossref_metadata_2025 huggingface dataset:
LIQUID CRYSTALLINE SOLVENTS AS MECHANISTIC PROBES‐V. AN INVESTIGATION OF THE EFFECT OF CHOLESTERIC ORDER ON THE FORMATION RATES OF VITAMIN D3 FROM PRE‐VITAMIN D3 AND OF PRE‐VITAMIN D3 FROM VITAMIN D3*
Authors: Jr Eugene G. Cassis , Weiss Richard G.
Published: January 2008

Abstract— The rates for conversion of pre‐vitamin D3 (pre‐D) to vitamin D, (D) and of D to pre‐D in the cholesteric liquid‐crystalline and isotropic phases of a 60/26/14 (wt/wt/wt) mixture of cholesteryl oleate/cholesteryl nonanoate/cholesteryl chloride and in hydrocarbon solvents (hexane and 2,2,4‐tri‐methylpentane) have been measured. The rate constants for the forward and reverse reactions in the cholesteric mixture are greater than those measured in the hydrocarbon solvent. The pre‐D D rate in the liquid‐crystalline phase is independent of whether pre‐D is generated in situ from 7‐dehydrocholes‐terol or from lumisterol3. Eyring plots of data from the cholesteric mixture show no perceptible differences between the liquid‐crystalline and isotropic phases: ΔH=83.85 3.0 kJ/mol and ΔS=‐64.3 9.7 J/mol‐degree for pre‐D D; ΔH=104.22.7 kJ/mol and ΔS = ‐13.7 8.4 J/ mol‐degree for D pre‐D. It is concluded that macro‐solvent order does not play an important role in the rates and equilibria for the pre‐D D intcrconversion. Solvent‐solute spatial interactions may be responsible for the high rates obtained in the cholesteric mixture.
IN VITRO SYNTHESIS OF PHYTOCHROME APOPROTEIN DIRECTED BY mRNA FROM LIGHT AND DARK GROWN AVENA SEEDLINGS*
Authors: Gorrmann Klaus , Schaefer Eberhard
Published: January 2008

Abstract—The aim of this work was to compare the translatability of poly‐A‐RNA from light‐ and dark‐grownArenaseedlings, the product of which should be phytochrome.

Polysomal poly‐A‐RNA was isolated from 4‐day‐old dark‐grownAvenaseedlings(Avena sativaL. cv. Garry) and translated in a rabbit reticulocyte lysate system. Immunoprecipitation by anti‐phytochrome serum was used for measurements of specific phytochrome translation. Characterization of the translated and immunoprectpitated protein was performed by comparison with [35S]‐methioninein vivo‐labelled phytochrome. The specificity of the precipitation was shown by parallel use of non‐specific serum and by competitive inhibition of precipitation by exogenous unlabelled phytochrome isolated by affinity chromatography.
SPECTRAL FEATURES OF THE BOUND ELECTRON ACCEPTOR A2 OF PHOTOSYSTEM I
Authors: Koike Hiroyuki , Katoh Sakae
Published: January 2008

Abstract— Difference spectrum for the reduction of A2, a bound secondary electron acceptor of photo‐system I, in the thylakoid membranes of a thermophilic blue‐green alga, Synechococcus sp., was determined by subtracting the difference spectrum of P700 photooxidation from the difference spectrum for flash‐induced absorption changes due to oxidation of P700 and reduction of A2, or by measuring light‐induced absorption changes under reducing conditions where reduced A2 accumulates. The spectrum showing a broad bleaching with two maxima at 420 and 440 nm indicates that A2 is an iron‐sulfur center different from P430.
WEIGLE REACTIVATION IN ACINETOBACTER CALCOACETICUS
Authors: Berenstein Dvora
Published: January 2008

Abstract— Weigle (W)‐reactivation was demonstrated in Acinetobacter calcoaceticus for the UV‐irra‐diated lysogenic phage P78. The reactivation factor (survival of irradiated phage on irradiated bacteria/ survival on unirradiated bacteria) reached a maximum value of 20. This was obtained at UV‐doses giving phage and host survivals of about 5 times 10‐6 and 1 times 10‐1, respectively. Intracellular development of W‐reactivated P78 was followed by one‐step growth experiments. Conditions which allowed maximal W‐reactivation also extended the period of phage production and yielded a somewhat reduced burst size.
A FLUORESCENCE LIFETIME ASSAY OF A MEMBRANE‐BOUND FLAVIN FROM CORN COLEOPTILES
Authors: Sarkar Hemanta K. , Song Pill‐Soon , Leong Ta‐Yan , Briggs Winslow R.
Published: January 2008

Abstract— The fluorescence lifetime of a partially‐purified membrane fraction containing flavin and b‐type cytochrome, presumably on the same protein, has been described. Possible implications of the blue light photoreactivity of the flavin as an assay, on the basis of its short fluorescence lifetime (about 1.37 ns), has been discussed.
DETERMINATION OF PARAMETERS OF EXCITED STATES OF DNA and RNA BASES BY LASER UV PHOTOLYSIS
Authors: Nikogosyan D. N. , Angelov D. A. , Oraevsky A. A.
Published: January 2008

Abstract— The mechanism of photodecomposition of nucleic acid bases in a neutral aqueous solution upon two‐step excitation of high‐lying electronic states by a powerful laser UV radiation is discussed. Experimental dependences of photodecomposition efficiency versus UV radiation intensity are measured both under picosecond and nanosecond laser UV irradiations. By comparison of experimental dependences with a theoretical model, we obtain some characteristics of excited states, such as lifetime t1 of the first electronic excited state S1 intersystem crossing yield φ, photosensitivity from an intermediate excited state and others for all five nucleic acid bases.
ESTIMATION OF PHOTOPRODUCT FORMATION IN GERMINATING SPORES OF BACILLUS SUBTILIS
Authors: Irie R. , Okamoto T. , Fujita Y.
Published: January 2008

Abstract— Changes in UV sensitivity during spore germination of Bacillus subtilis mutants possessing various defects in DNA repair capacities were analysed in order to estimate the yield of the DNA photoproducts at the transient, UV resistant stage which occurs in the process of germination. It was concluded that the yield of the spore‐specific photoproduct (5‐thyminyl‐5,6‐dihydrothymine, TDHT) at the transient stage was only about 3% of that in dormant spores and the yield of the cyclobutane‐type pyrimidine dimers at this stage was about 10% (or less) of that in germinated spores.
PHYCOBILIPROTEINS: COMPARISON OF SOLUTION AND SINGLE CRYSTAL FLUORESCENCE FOR C‐PHYCOCYANIN AND B‐PHYCOERYTHRIN*
Authors: Jr John P. Priestle , Jr Richard H. Rhyne , Salmon Jessie B. , Hackerit Marvin L.
Published: January 2008

Abstract— Trimeric and hexameric solution forms of C‐phycocyanin (CPC) from the cyanophyte Agme‐nellum quadruplicatum have been isolated and their spectral properties compared to those obtained from single crystals. Although the absorbance peak of a suspension of small C‐phycocyanin crystals is red‐shifted only 7 nm relative to the solution forms, the single crystal fluorescence is red‐shifted 60 nm relative to the solution forms. The crystal fluorescence spectrum exhibits a single peak at LDmax= 708 nm when excited at 514.5 or 530.9 nm and two peaks (LDmax= 661 and 708 nm) when excitation occurs at 568.2 nm. Fluorescence depolarization measurements indicate that extensive energy transfer could occur for both solution and crystal forms with the latter being dependent upon the relative orientation of the crystal with respect to the excitation dipole. Similar results were obtained with B‐phycoerythrin (BPE) from the red alga Porphyridium cruentum where the single crystal fluorescence is red‐shifted =50nm relative to the solution spectra with two peaks (LDmax= 583 and 617 nm) observed whose relative intensities are dependent on the excitation wavelength (LDmax– 514.5 and 530.9 nm). Single crystal fluorescent lifetimes exhibited considerable shortening relative to that observed for the solution forms. The implications of these results are discussed with respect to the possible relationships of the crystalline structures to the assembly forms present within phycobilisomes.
EXCITON MIGRATION AND TRAPPING IN PHOTOSYNTHESIS
Authors: Pearlstein Robert M.
Published: January 2008

Abstract— Mobile electronic excited states, excitons, undergo random walks through the antenna chlorophyll arrays of photosynthetic organisms. The time interval from exciton creation, by photon absorption, until its first arrival at a reaction center (RC) is called the “first passage time” (FPT) of the random walk. A theory of exciton migration and trapping presented here predicts that the exciton lifetime, as measured from chlorophyll fluorescence decay in chromatophores or P700 complexes, is a linear function of the fractional number of quanta absorbed directly by the antenna, not by the RC. The slope of this line is the FPT, and its intercept is the exciton's lifetime as limited only by photoconversion at the RC. This photoconversion‐limited lifetime is simply related to the in situ photoconversion rate constant via two parameters, each of which is experimentally accessible. It is also possible to obtain values of individual FoUrster rate constants, at least approximately, from measurements of exciton lifetime as functions of temperature and excitation wavelength. This new theory, based on lattice random walk models, receives some support from fluorescence measurements done on Rhodopseudomonas sphaeroides R26 chromatophores. In its present form the theory is only applicable to one‐antenna‐component systems, like Rp. sphaeroides R26 or Rhodospirillum rubrum chromatophores or P700 complexes, but should be readily extendible to multi‐antenna‐component systems including whole chloroplasts.
BLUE LIGHT RESPONSES IN NITRATE REDUCTASE MUTANTS OF NEUROSPORA CRASSA
Authors: Paietta John , Sargent Malcolm L.
Published: January 2008

Abstract— The role of nitrate reductase in the blue light responses of photosuppression and phase shifting of circadian conidiation was studied in Neurospora crassa. The photoresponses, as assayed in three nitrate reductase mutants (nit‐1,nit–2 and nit‐3), showed no significant differences as compared to the responses in a strain which could utilize nitrate. In addition, the responses occur on a medium which (i) represses nitrate reductase activity due to the presence of ammonium ion and arginine or (ii) results in the production of an inactive enzyme due to the presence of tungsten. Nitrate reductase appears to be of no or secondary importance as a photoreceptor in the responses studied.
DETERMINANTS OF PORPHYRIN‐SENSITIZED PHOTOOXIDATION CHARACTERIZED BY FLUORESCENCE AND ABSORPTION SPECTRA
Authors: Kessel David , Rossi Eliana
Published: January 2008

Abstract— As a model for studies involving biologic systems, rates of hematoporphyrin and protopor‐phyrin‐sensitized photooxidation of tryptophan were measured in water‐methanol mixtures. Absorption and fluorescence‐emission spectra associated with solutions of porphyrins in different water‐methano! mixtures were also examined. The optimal rate of photooxidation by hematoporphyrin occurred in 30% methanol; by protoporphyrin, in 60% methanol. Absorption spectra were examined to characterize dispersion of hematoporphyrin into monomeric form in 90% methanol, and the dimer formation which predominates in 30% methanol. With the more hydrophobic protoporphyrin, an absorption spectrum characteristic of drug monomer was seen in 100% methanol, a dimer spectrum was observed in 60% methanol. At methanol concentrations < 60%, we observed impaired photooxidation and another alteration in the absorption pattern apparently reflecting drug aggregation beyond the dimer stage. Fluorescence emission maxima of both porphyrins were blue‐shifted with increasing solvent dielectric constant, but an additional blue shift was detected in an aqueous environment which was apparently related to porphyrin aggregation. Absorption and fluorescence‐emission spectra appear helpful for characterizing environmental determinants of porphyrin‐sensitized photooxidation.
RECOVERY FROM DAMAGE INDUCED BY ACRIDINE PLUS NEAR‐ULTRAVIOLET LIGHT IN ESCHERICHIA COLI
Authors: Wagner Stephen , Feldman Abbe , Snipes Wallace
Published: January 2008

Abstract— Escherichia coli cells treated with sublethal doses of acridine plus near‐UV light exhibit an effective split‐dose recovery response that requires an incubation period of about 30–45 min. Studies of the metabolic requirements for split‐dose recovery revealed the following: (a) DNA synthesis is not required for split‐dose recovery; (b) inhibition of electron transport or protein synthesis reduces the efficiency of split‐dose recovery by about one‐half; (c) inhibition of phospholipid synthesis or cell wall synthesis completely eliminates the split‐dose recovery response. These results suggest an involvement of membrane repair mechanisms in response to damage by acridine plus near‐UV light. Additional evidence for such a process was provided by more direct assays for membrane recovery. It was found that cells treated with sublethal doses of acridine plus near‐UV light are sensitive to low concentrations of detergents, and lose that sensitivity upon incubation. Likewise, treated cells are susceptible to lethal osmotic shock, but can recover from this susceptibility if incubated after treatment but prior to exposure to low osmotic conditions. Based on accumulating evidence, we propose that E. coli cells are capable of repairing membrane damage resulting from exposure to acridine plus near‐UV light.
ANALYTICAL CHARACTERIZATION OF SPECTRAL ACTINIC FLUX and SPECTRAL IRRADIANCE IN THE MIDDLE ULTRAVIOLET
Authors: Schippnick P. F. , Green A. E. S.
Published: January 2008

Abstract— We present an analytic characterization of upward and downward diffuse spectral irradiance for the wavelength range 280–380 nm, solar zenith angle range from 0 to 86, altitude range from 0 to 5 km and for non‐zero surface albedo. This work is a modification and extension of the previous work of Green, Cross and Smith based upon the radiative transfer calculations of Braslau, Dave and Halpern. Guided by these irradiance systematics we develop an analytic characterization of diffuse spectral scalar irradiance or actinic flux also broken down into upward and downward components for the above wavelengths, solar zenith angles and altitudes, for non‐zero surface albedo utilizing the actinic flux calculations of Peterson.
THE QUANTUM EFFICIENCY OF DYE‐INDUCED PHOTOELECTRIC EFFECTS IN BILAYER MEMBRANES
Authors: Huebner Jay S. , Jr W. E. Varnadore
Published: January 2008

Abstract— Voltage transients are generated across lipid bilayer membranes by light flashes as a result of photophysical processes in sorbed dyes which displace electrical charges. A theory is presented which indicates that: (i) the fraction of sorbed dye which displaces charge from one flash can be determined by the fractional reduction in the photovoltage amplitude resulting from a second and identical flash, providing the second flash occurs before dye excited by the first flash returns to its equilibrium condition. (ii) The photoeffect quantum efficiency can be determined from the fraction of dye displacing charge, the light intensity and the dyes' optical absorption cross section. Apparatus constraints required different experimental procedures for dyes with different excited state life times, which are discussed. Experimental results are presented for an azo dye, 3,3'‐bis(α‐(trimethyiammonium)methyl)azobenzenebromide (Bis‐Q), three carbocyanine dyes in the series 3,3'‐dimethyl‐2,2'‐oxacarbocyanine‐iodide (diO‐C1‐3), an amino‐pyridinium dye, 4‐(p‐(dimethyl‐amino)styryl)‐1‐rnethyl‐pyridinium‐iodide (di‐1‐ASP), and a xanthene dye, 2',4',5',7'‐tetraiodofluorescein (erythrosin), the sodium salt of which is known as F, D and C red number 3. The dyes' optical absorption cross section values are uncertain owing to solvent and orientational effects in membranes. Photoeffect quantum efficiency values obtained by calculating optical absorption cross sections from the dyes' molar extinction coefficients in aqueous solutions are: Bis‐Q (0.08), diO‐C1‐3 (0.31), diO‐C2‐3 (0.22), diO‐C5‐3 (0.08), di‐l‐ASP (0.3) and erythrosin (0.39).
PHOTOREACTIVATION ASSOCIATED WITH MORPHOLOGICAL ABNORMALITY IN SEA URCHIN EMBRYOS INDUCED BY ULTRAVIOLET‐IRRADIATED SPERM
Authors: Ejima Yosuke , Shiroya Tsugio
Published: January 2008

Abstract— Morphological abnormality due to the UV irradiation of sperm and its modification by photoreactivation (PR) were studied in the sea urchin, Hemicentrotus pukherrimus. When sperm was UV‐irradiated and allowed to fertilize unirradiated eggs, the effect of the UV was manifested as an abnormal morphology of embryos in the gastrula or later stages. The UV‐induced morphological abnormality was prevented by photoreactivation when the fertilized eggs were illuminated with visible light. In the experiments on a stage‐dependent change of PR effectiveness, it was found that an illumination sufficed to effect a nearly complete PR when applied up to the onset of the first DNA synthetic phase, while the PR effectiveness declined thereafter. Illumination after the completion of DNA synthesis had little effect for PR.
LIGHT‐INDUCED ELECTRON TRANSPORT ACROSS SEMICONDUCTOR ELECTRODE/REACTION‐CENTER FILM/ELECTROLYTE INTERFACES
Authors: Seibert Michael , Janzen A. Frederick , Kendall‐Tobias M.
Published: January 2008

Abstract— Reaction center (RC) complexes isolated from the photosynthetic bacterium Rhodopseudomonas sphaeroides R‐26 were dried as a film onto platinum and semiconductor (SnO2) electrodes. The light‐induced primary charge separation which occurs across the biological complex couples electrically with the SnO2 but not with the metal electrode on the time scale of observation. As the working electrode in a two‐electrode photoelectrochemical cell, RC‐coated SnO2 generated photovoltages as high as 80 mV and photocurrents as high as 0.5µA·cm2 when exposed to light of λ >600nm. The number of quinone molecules per RC strongly influences the photovoltage and photocurrent observed. Photo‐effects generated by RC electrodes persist after several days of storage; however, the kinetics and polarity of the effects are subject to change. The potential use of RC electrodes lies more as a new probe of photosynthetic electron transport rather than as a solar energy conversion device because modification to the RCs and their environment affect the electrical properties of the cell. An energy‐level model is proposed to explain how the photoelectrochemical cell functions.
THE EFFECT OF PROLONGED LIGHT EXPOSURE ON THE EFFECTIVENESS OF PHYTOCHROME IN ANTHOCYANIN SYNTHESIS IN TOMATO SEEDLINGS*
Authors: Drumm‐Herrel H. , Mohr H.
Published: January 2008

Abstract— The hypocotyl of the tomato (Lycopersicon esculentum) seedling synthesizes large amounts of anthocyanin if exposed to prolonged light. Single light pulses are totally ineffective. The involvement of phytochrome can be shown by light pulse treatments following a prolonged light exposure. It is predominantly the action of blue/UV light which leads to a high responsiveness of anthocyanin synthesis towards phytochrome. Moreover, the data suggest a phytochrome‐independent action of blue/UV light, in particular of UV‐B, on anthocyanin synthesis.
PHOTOREACTIVATING ENZYME INDUCTION IN HUMAN LYMPHOCYTES
Authors: Sutherland Betsy M. , Castellani Amleto
Published: January 2008

Abstract— Photoreactivating enzyme (PRE) activity was determined in human lymphocytes cultured in the presence or absence of the mitogen phytohemagglutinin (PHA). Photoreactivating enzyme activity increased from 0 to 12pmol/mg/h in about 40 h in cells cultured in the presence of PHA; enzyme activity was unchanged in the absence of PHA. The kinetics of induction of PRE and of lactate dehydrogenase, a marker of mitogenic stimulation, were indistinguishable, indicating that PRE induction results from stimulation of transcription and translation by the mitogen, rather than a specific effect of the PHA on PRE production. The level of PRE was also higher in mouse lymphoblasts growing rapidly in RPMI 1640 medium than in the same cells growing more slowly in Dulbecco's medium.
CROCETIN, A WATER SOLUBLE CAROTENOID MONITOR FOR SINGLET MOLECULAR OXYGEN
Authors: Matheson I. B. C. , Rodgers M. A. J.
Published: January 2008

Abstract The water soluble carotenoid crocetin has been studied as a singlet molecular oxygen monitor in D2O solution, pD 8.4. Crocetin reacts chemically with singlet molecular oxygen with a rate constant of 4 x 108M‐1 s‐1. The rate constant for total quenching, chemical and physical, is 2.5 x 109M‐1 s‐1. Crocetin shows evidence for a reversible reaction with singlet molecular oxygen, as demonstrated by a fairly rapid absorption recovery after bleaching.
DECONVOLUTION OF THE RED P700 DIFFERENCE SPECTRUM BASED ON A SET OF THREE GAUSSIAN COMPONENTS: FURTHER EVIDENCE FROM LITERATURE SPECTRA
Authors: Schaffernicht H. , Junge W.
Published: January 2008

Abstract Literature data on the light induced difference spectrum of the photosynthetic reaction centre complex P700 were analysed in the spectral region from 670‐700 nm. In accordance to our previous Gaussian deconvolution of the flash induced difference spectrum and the linear dichroism spectrum of photosystem I particles from green plants, we present here fits of three representative difference spectra that were recorded at room temperature and at low temperature conditions, respectively. These fits are generated by using the same set of only three Gaussian components that we specified previously: (1) a disappearing wide band around 695 nm representing the absorption of the reduced special‐pair of chlorophyll‐a; (2) an appearing narrower band at slightly shorter wavelength (In agreement with our previous results, this band shows half the oscillatory strength of the former band. It is therefore attributed to the non‐oxidized chlorophyll‐a in the special pair); and (3) a bathochromic bandshift centered around 688 nm, which indicates the local electrochromic response of chlorophyll‐a antennae molecule(s) close to the site of the primary donor. Among the reports by several authors we attribute the variation of the difference spectra of P700 in the region from 670‐720 nm mainly to a variation in the magnitude of the third component, the local electrochromic one. We can also account for the peculiar shape of the low temperature spectra, mainly by alteration of the extent of the electrochromic component. It seems reasonable that the electrochromic component reacts most sensitively against structural changes of the reaction centre protein complex (brought forth by different degrees of depletion from antennae or by variation of the temperature).
PRIMARY INTERMEDIATES IN THE PULSED IRRADIATION OF RETINOIDS
Authors: Lo K. K. N. , Land E. J. , TRUSCOTT T. G.
Published: January 2008

Abstract Laser flash photolysis and pulse radiolysis have led to the characterisation of several shortlived intermediates formed after irradiation of retinoic acid and retinyl acetate in hexane or methanol.

For retinoic acid, the triplet state, wavelength maximum 440 nm, extinction coefficient 7.3 × 104 dm3 mol−1 cm−1, decay constant 6.2 × 105 s−1, is formed with a quantum yield of 0.012 for 347 nm excitation. The radical cation, absorption maximum 590 nm, extinction coefficient ∼7 × 104 dm3mol−1 cm−1, is formed in a biphotonic process. The radical anion, absorption maximum 510nm in hexane, 480 nm in methanol where its extinction coefficient is 1.2 × 105 dm3mol−1 cm−1, appears to decay partially in methanol into another longer‐lived neutral radical, wavelength maximum 420 nm, by loss of OH−.

For retinyl acetate, the triplet state, absorption maximum 395 nm, extinction coefficient 7.9 × 104dm3mol−1 cm−1, decay constant 1.2 × 106s−1 is formed with a quantum yield of 0.025 for 347 nm excitation. Monophotonic photoelimination of OCOCH3− in methanol produces the retinylic carbenium ion, wavelength maximum 590 nm, whose decay is enhanced by ammonia, k ∼ 2 × 106 dm3 mol−1 s−1 and retarded by water. The radical cation also has a wavelength maximum at 590 nm, its extinction coefficient being ∼ 1.0 × 105 dm3mol1 cm−1. The long‐lived transient absorption with maximum at 385 nm, extinction coefficient 1.0 × 105 dm3mol−1 cm−1, obtained from the reaction of the solvated electron with retinyl acetate in methanol may be due to either the radical anion itself or more likely the radical resulting from elimination of OCOCH3− from this anion.

These results suggest that skin photosensitivity caused by retinyl acetate might be greater than that due to retinoic acid.
ON THE ROLE OF TYROSINE IN THE PHOTOCYCLE OF BACTERIORHODOPSIN
Authors: Rosenbach V. , Goldberg R. , Gilon C. , Ottolenghi M.
Published: January 2008

Abstract ‐The rate of formation of the M intermediate (kM) in the photocycles of bacteriorhodopsin (bR570) and of nitrated bacteriorhodopsin (bR532n), is measured over the range between pH 6.5 and 11.5. In the case of bR570, kM is markedly pH dependent, exhibiting a titration‐like curve with pK? 10.3. The pH dependency is completely eliminated by nitration. On the basis of previous work by Lemke and Oesterhelt (1981), the effect is attributed to the specific modification of the Tyr 26 residue. The data are rationalized by a mechanism in which deprotonation of Tyr 26 at the stage of the L intermediate constitutes a prerequisite for deprotonation of the retinal‐lysine SchifT base. Both reactions are intimately associated with the photo‐induced proton pump mechanism.
INHIBITORY EFFECT OF CONTINUOUS FAR‐RED PREIRRADIATION ON CHLOROPHYLL ACCUMULATION OF PHARBITIS NIL COTYLEDONS
Authors: Yoshida Kazuichi , Konishi Michio
Published: January 2008

Abstract The effect of continuous far‐red (FR) preirradiation on the accumulation of chlorophyll (Chi) during a white light (WL; 500 lx) period was examined using Pharbitis nil cotyledons. The saturation level of accumulated Chi attained after prolonged exposure to WL was always lowered by continuous FR irradiation preceding the WL. The rate of Chi accumulation during the rapid increase phase (operationally defined as the amount of Chi accumulated during a 24‐h WL period) was enhanced by preirradiation with up to 36 h of FR. However, when the FR preirradiation lasted longer, the rate was reduced below the dark control level. Even FR preirradiation of up to 36 h fully reduced the rate of Chi accumulation under WL when 36 h or longer darkness was spaced between the FR and the WL period.
PHEOMELANIN PHOTOCHEMISTRY. PHOTOLYSIS OF MODEL COMPOUNDS
Authors: Liu Chung‐Tsing , Chedekel Miles R.
Published: January 2008

Abstract Two pheomelanin model compounds were prepared and their photochemistries examined. Upon irradiation, an oxygen‐mediated photopolymerization reaction was observed. The photopolymers obtained were characterized by their apparent molecular weights, UV and fluorescence spectra. The implications of these findings with respect to the structure and photobiology of pheomelanin are discussed.
EFFECTS OF ACRIDINE PLUS NEAR‐ULTRAVIOLET LIGHT ON THE OUTER MEMBRANE OF ESCHERICHIA COLI
Authors: Wagner Stephen , Snipes Wallace
Published: January 2008

Abstract The hydrophobic photosensitizer acridine plus near‐ultraviolet light damages both plasma membranes and outer membranes in Escherichia coli. Two lines of evidence are presented that outer membrane proteins are affected by acridine plus near‐ultraviolet light treatment and that the effect is selective for certain proteins. First, analysis of outer membrane proteins on sodium dodecylsulfate polyacrylamide gels revealed that some protein bands are diminished upon treatment while others remain unaltered. New bands also appear, suggesting degradation or crosslinking reactions. Second, bacteriophage adsorption studies showed that treatment of E. coli F cells with acridine plus near‐ultraviolet light causes a loss in functionality of the receptor for phage T5. Treatment of E. coli ABU57 cells under comparable conditions has no discernable effect on the functionality of the receptor for phage BF23.
IN VIVO EXCISION OF PYRIMIDINE DIMERS IS MEDIATED BY A DNA N‐GLYCOSYLASE IN MICROCOCCUS LUTEUS BUT NOT IN HUMAN FIBROBLASTS
Authors: La Belle Michael , Linn Stuart
Published: January 2008

Abstract It has been previously shown that Micrococcus luteus possesses a pyrimidine dimer‐specific endonuclease which in vitro, functions as both an endonuclease and DNA‐glycosylase. To determine if these combined activities function in vivo, we have isolated and examined the excision products of UV‐irradiated M. luteus. In addition, we have devised a procedure to isolate and examine the excision products from UV‐irradiated human fibroblasts to determine if an endonuclease/glycosylase activity functions in the excision of UV‐induced pyrimidine dimers in human fibroblasts. We find that, in vivo, an endonuclease/glycosylase mechanism is utilized extensively in the repair of pyrimidine dimers by M. luteus, but that human fibroblasts do not appear to use this mechanism.
FORMATION BY HYDROGEN PEROXIDE OR 254 nm RADIATION OF A NEAR‐UV CHROMOPHORE FROM PEPTIDE‐BOUND CYSTEINE
Authors: McCormick J. P. , Klita Stefan , Terry Joan , Schrodt Mary , Eisenstark A.
Published: January 2008

Abstract Treatment of glutathione or N‐acetylcysteinamide in water with hydrogen peroxide, or with 254 nm radiation together with molecular oxygen, results in the formation of a near‐UV chromophore having maximal absorption at 305 nm. From examination of related compounds, it is apparent that the N‐acylcysteinamide residue is the key element required for generation of the 305 nm chromophore. The structure of this near‐UV chromophore is stable to base but unstable in aqueous acid, is relatively sensitive to oxidation by hydrogen peroxide but is only very slowly reduced by sodium borohydride and displays good thermal stability at 50°C.
DESIGN AND PERFORMANCE OF THE OKAZAKI LARGE SPECTROGRAPH FOR PHOTOBIOLOGICAL RESEARCH
Authors: Watanabe Masakatsu , Furuya Masaki , Miyoshi Yasuhiro , Inoue Yasunori , Iwahashi Isao , Matsumoto Koichi
Published: January 2008

A computer‐operated spectrograph was recently built at Okazaki, Japan. Different specimens can be placed on a horseshoe‐shaped focal curve (10 m long) covering a wavelength range of 250 to 1000 nm so they can be irradiated simultaneously. The linear dispersion is about 0.8 nm/cm. The photon fluence rate on the focal curve is 5 x 1015. photons x cm‐2 x s‐1 at 300nm and 1 x 1016 photons x cm‐2 x s‐1 at 600 and at 900 nm. The spectral half width is 5.5 nm or less on the focal curve. The stray light content is about 10‐5 of the main peak at the peak wavelength ± 100 nm. Specimens are set in microcomputer‐controlled threshold boxes so that wavelengths, photon fluence rates, photon fluences and timing of irradiations are controlled automatically according to a pre‐programmed schedule. An optical fiber system is also provided for remote irradiations.
PICOSECOND FLUORESCENCE KINETICS OF N‐ALL‐TRANS‐RETINYLIDENE‐AT‐BUTYLAMINE
Authors: Everaert J. , Rentzepis P. M.
Published: January 2008

Fluorescence lifetimes are reported for N‐all‐trans‐retinylidene‐n‐butylamine in hexane. Picosecond resolution was obtained by excitation with a single 355‐nm pulse, 25 ps FWHM, from a passive mode‐locked YAG‐laser and detection with a high speed streak camera. The lifetime dependence on temperature and the spectral characteristics support a vibrational‐torsional deactivation model of the singlet excited state of two different conformers. Additional data in decalin are consistent with this model, while the quenching in alcoholic solutions may be supported by the solvent reorientation.
THE COLORS OF FIREFLY BIOLUMINESCENCE—II EXPERIMENTAL EVIDENCE FOR THE OPTIMIZATION MODEL*
Authors: Seliger H. H. , Lall A. B. , Lloyd J. E. , Biggley W. H.
Published: January 2008

Abstract— The shapes, the peak wavelengths and the close matching of bioluminescence colors to visual spectral sensitivities in North American firefly species are consistent with the predictions of a spectral optimization model for selection in evolution (Seliger et al., 1982). A screening pigment found by microspectrophotometry in the rhabomeres of Photinus pyralis has the absorbancc characteristics predicted by the model. The biologically effective adaptation, a dimensionless ratio proportional to the relative advantage of a species to detect bioluminescence during twilight. has been calculated from experimentally determined distributions of ambient spectral radiances, visual spectral sensitivities and bioluminescence emissions and is shown to correlate both with color of bioluminescence and with the timing of initiation of flashing activity. The colors of firefly bioluminescence are therefore species‐specific adaptations to optimize the detection of bioluminescence in the different photic environments in which the species have evolved.
GENOTOXICITY OF THE NATURAL FUROCHROMONES, KHELLIN AND VISNAGIN AND THE IDENTIFICATION OF A KHELLIN‐THYMINE PHOTOADDUCT
Authors: Abeysekera B. F. , Abramowski Z. , Towers G. H. N.
Published: January 2008

Abstract— Longwave UV irradiation of a frozen aqueous solution of khellin and thymine resulted in the formation of a 2+2 photoadduct between the 2,3 double bond of khellin and the 5′, 6′ double bond of thymine. This behaviour is analogous to that of the furocoumarins and serves as a mechanism to describe the genotoxicity of the furochromones khellin and visnagin. These two compounds are phototoxic towards bacteria and fungi and inhibit mitosis and cause gross chromosomal changes in Chinese hamster ovary (CHO) cells in near UV light. For comparative purposes, 8‐methoxypsoralen was also tested and was found to be more active than visnagin which, in turn, was more active than khellin.
REACTIONS OF PHOTOEXCITED METHYLENE BLUE
Authors: Harmatz D. , Blauer G.
Published: January 2008

Abstract—Some reactions of methylene blue (oxidized form) excited by visible light, were investigated at 25°C in dilute and deaerated aqueous solutions. Under these conditions, methylene blue causes oxidation of sodium ascorbate, ferrocytochromecand ethylenediamine tetraacetate (in air), as determined spectrophotometrically. Most of these reactions showed measurable reversibility in the dark. Chelation with divalent ions inhibited the photoxidation of ethylenediamine tetraacetate. Ferricytochromecwas reduced by excited methylene blue. The buffers used in the above reactions (Tris‐HCl or sodium phosphate) appeared to participate in these photoexcited systems. Inhibitors are described for the methylene blue‐ascorbate photoreaction.
TRIFLUOPERAZINE: CORNEAL ENDOTHELIAL PHOTOTOXICITY
Authors: Hull David S. , Csukas Steve , Green Keith
Published: January 2008

Abstract— Trifluoperazine is a commonly used agent for the treatment of psychiatric disorders. Perfusion of corneal endothelial cells with trifluoperazine‐HCI concurrent with 3 min of exposure to long wavelength ultraviolet light resulted in a corneal swelling rate which was greater than that found in corneas where endothelial cells were perfused with trifluoperazine‐HCI and not exposed to ultraviolet light. Exposure of endothelial cells to 25 W incandescent light for 5 min during perfusion with trifluoperazine‐HCI did not result in a corneal swelling rate in excess of that found during perfusion with trifluoperazine in the dark. The increased corneal swelling rate could be produced by pre‐exposure of the trifluoperazine‐HCI perfusing solution to ultraviolet light suggesting the production of toxic photo‐products during exposure of trifluoperazine HCI to ultraviolet light. Perfusion of corneal endothelial cells with non‐ultraviolet illuminated trifluoperazine HCI had no effect on endothelial cell membranes or ultra‐structure. This is in contrast to cells perfused with trifluoperazine HCI that had been exposed to ultraviolet light in which there was an alteration of mitochondria and a loss of cytoplasmic homogeneity. The data imply that the trifluoperazine HCI photoproduct had an adverse effect on cellular transport mechanisms. The study also further demonstrates that value of the corneal endothelial cell model for identifying the physiological and anatomical changes occurring in photo‐induced toxic reactions.
PHOTOCONVERSION OF PHYTOCHROME IN VIVO STUDIED BY DOUBLE FLASH IRRADIATION IN Mougeotia AND Avena
Authors: Kraml Manfred , Schäfer Eberhard
Published: January 2008

Abstract— The kinetics of phytochrome phototransformation from the red‐absorbing form (Pr) to the far‐red‐absorbing form (Pfr) in vivo at 22°C were studied using a double flash apparatus with 1‐ms flashes. Photoconversion by simultaneous flashes of red light saturates at a low Pfr level, indicating the possible attainment of a photoequilibrium between the excitation of Pr and the photoreversion of intermediates in the course of the I‐ms flashes. At saturation energy, simultaneous flashes resulted in about 50% as much Pfr as was produced by saturating irradiation with 5 s red light. Intermediates of the phototransformation pathway were analysed by separating two red or a red and a far‐red flash by variable dark intervals. In both plants phototransformation intermediates with half‐lives < 1 ms occur, but they are too short‐lived to characterize by our method. The subsequent intermediates have half‐lives of about 7 ms and 150 ms in A vena, 2 ms and 10 ms in Mougeotia. The conversion from Pr to Pfr seems to be completed 1 s after the red flash in Avena. In the alga Mougeotia, Pfr formation seems to be finished within only 50 ms after the inducing red flash. The kinetics obtained from physiological and spectrophotometric experiments with Avena mesocotyls are almost identical. These observations indicate that the physiological response corresponds directly to the amount of Pfr produced and not to phototransformation intermediates or “cycling” between Pr and Pfr.
PHOTOCONTROL OF HYPOCOTYL ELONGATION IN DE‐ETIOLATED Cucumis sativus L. RAPID RESPONSES TO BLUE LIGHT
Authors: Gaba V. , Black M.
Published: January 2008

Abstract— Rapid inhibition of hypocotyl extension of de‐etiolated Cucumis sativus L. by blue light is described, and compared with responses to white fluorescent light. Rapid inhibition of hypocotyl growth by blue light via the specific blue light photoreceptor requires a minimum Buence rate. Above this minimum value rapid modulations of growth rate accompany changes in blue light fluence rate. An initial response to blue light, or to a step‐up in blue fluence rate takes less than 5 min. A drop from high to low fluence rate blue light (or to darkness) is followed by a recovery of the growth rate after about 20 min. A change from a low fluence rate to darkness elicits a more rapid recovery of growth rate (within 7 min). Similar responses were obtained in seedlings de‐etiolated for a few hours and for several days.
PROJECTIONS OF INCREASED NON‐MELANOMA SKIN CANCER INCIDENCE DUE TO OZONE DEPLETION
Authors: Rundel R. D. , Nachtwey D. S.
Published: January 2008

Abstract— Projections of increase in non‐melanoma skin cancer incidence due to ozone layer depletion by chlorofluorocarbons are presented. Projections have been made for five different ozone depletion scenarios, based on US. Environmental Protection Agency estimates of potential worldwide industrial production and commercial applications of chlorofluorocarbons, and their eventual release into the atmosphere. The least favorable scenario, a regulatory cap on production at estimated 1990 levels, would lead to an eventual 30% ozone depletion and to an eventual doubling of skin cancer incidence by the year 2300. The most favorable scenario, a reduction in production commencing now and reaching a low production target by 1990, would limit ozone depletion to an eventual 2.8%, and increase in skin cancer to about 5%. Compared to the least favorable scenario, the most favorable one would prevent an average of about 100,000 cases of skin cancer per year in the United States between now and the year 2100.
LIGHT‐INDUCED QUENCHING OF PHOTOSYSTEM II FLUORESCENCE AT 77 K
Authors: Kyle David J. , Arntzen Charles J. , Franck Fabrice , Inoue Y.
Published: January 2008

Abstract— Light‐induced quenching of the low temperature fluorescence emission from photosystem II (PS II) at 695 nm (F695) has been observed in chloroplasts and whole leaves of spinach. Photosystem I (PS I) fluorescence emission at 735 nm (F735) is quenched to a lesser degree but this quenching is thought to originate from PS II and is manifest in a reduced amount of excitation energy available for spillover to PS I. Differential quenching of these two fluorescence emissions leads to an increase in the F735/F685 ratio on exposure to light at 77 K. Rewarming the sample from ‐196°C discharges the thermoluminescence Z‐band and much of the original unquenched fluorescence is recovered. The relationship between the thermoluminescence Z‐band and the quenching of the low temperature fluorescence emission (F695) is discussed with respect to the formation of reduced pheophytin in the PS II reaction center at 77 K.
FLASH PHOTOLYSIS STUDIES OF HEMATO‐AND COPRO‐PORPHYRINS IN HOMOGENEOUS AND MICROHETEROGENEOUS AQUEOUS DISPERSIONS
Authors: Reddi E. , Jori G. , Rodgers M. A. J. , Spikes J. D.
Published: January 2008

Abstract—

This paper describes an experimental study of the photo properties of the triplet (T,) states of hematoporphyrin (HP) and coproporphyrin (CP), particularly in relation to their medium dependence and reactivity towards oxygen. Triplet‐triplet absorption spectra of HP and CP have been determined in aqueous buffer at pH = 7.4 and in water‐methanol and water‐formamide mixtures. The spectra corrected for ground state contributions show major absorption peaks near 400 nm and lesser peaks near 500 nm. Extinction coefficient measurements have been made and their dependences on solvent composition investigated. Natural lifetimes of the T1 states of HP and CP and the bimolecular quenching constants with oxygen have been determined. The quantum yields of T1 formation are ca. 0.6 in buffer rising to 0.8 and higher in predominantly organic media. Incorporation of the porphyrins into micellar phases similarly causes φT, to increase. Quantum efficiencies of O−2 and O2(lΔg) formation have been determined for HP in buffer, some binary mixtures and micellar dispersions. Superoxide yields are low and may result from photo‐ionization processes. O2(lΔg) yields are large but appear to have an unexpected dependence on the medium.
A LASER FLASH PHOTOLYSIS STUDY OF PYRENE‐1‐ALDEHYDE. INTERSYSTEM CROSSING EFFICIENCY, PHOTOREACTIVITY AND TRIPLET STATE PROPERTIES IN VARIOUS SOLVENTS
Authors: Kumar Ch. V. , Chattopadhyay S. K. , Das P. K.
Published: January 2008

Abstract— Triplet‐and singlet‐related photoprocesses of pyrene‐1‐aldehyde (PA) in various solvents have been investigated in detail using 337.1 and 355 nm laser flash photolysis in conjunction with time‐correlated determination of fluorescence lifetimes (τF) and steady‐state photochemical and absorption‐emission spectral measurements. In benzene, the lowest triplet of PA (43 < ET < 46 kcal/mol) has a lifetime of about 50 µs (τT) and displays the absorption maximum at 443 nm with a maximum extinction coefficient (εmax) of 21000 M‐1cm‐1; the corresponding ketyl radical has a sharp absorption maximum at 428 nm (εmax≥ 25000 M‐1cm‐1). The quantum yields (φT) of lowest triplet occupation are high in nonprotic solvents (0.6–0.8), decrease in protic solvents (alcohols) as the polarity of the latter is increased, and maintain a complementary relationship with the quantum yields (φF) of fluorescence. Quantum yields (φPC) of loss of PA due to photoreactions in some solvents have also been determined under conditions of steady irradiation at 366 nm; φPC is in the range 0.1–0.2 in electron‐rich olefinic solvents such as cyclohexene and tetramethylethylene. These results concerning τF, τT, φF. φT and φPC as well as the effects of 1,2,4‐trimethoxybenzene and 2,5‐dimethyl‐2,4‐hexadiene as quenchers for fluorescence, triplet yield, and photochemistry are discussed in the light of possible state orders for PA in polar and nonpolar environments.
LASER SPECTROSCOPY OF MODEL PHOTOSYNTHETIC SYSTEMS
Authors: Rubin L. B. , Braginskaja O. V. , Bartenev V. Ja. , Paschenko V. Z. , Pshezsheckii V. S.
Published: January 2008

Abstract— The goal of the present work was to create and investigate a model system, using a dye imbedded into polymer structure, and to examine characteristics which would provide low heat dissipation and excitation diffusion characteristics approaching those seen in the “antenna” of the photosynthetic apparatus. Zinc tetraphenoxyphtalocyanine served as a dye, and different types of polyvinyl pyridine polymers and polystyrene were used as polymer matricies. Measurements of the absorption, fluorescence and Raman spectra of the polymeric films with dye molecules show that along with Van der Waals interactions of the dye molecules with the side aromatic groups of the polymer there is a coordination interaction between the metal atoms of Zinc phtalocyanine and the nitrogen atoms of the pyridine group of the polymer. A model system shows low heat losses of excitation energy, when the dye concentration does not exceed 10‐2M (mean distances between molecules of about 34 Å). Electronic excitation diffusion characteristics appeared to be close to those of the light harvesting antenna of the photosynthetic apparatus, indicating high efficiency of the energy migration in it.
LIGHT‐INDUCED LINEAR DICHROISM IN PHOTOREVERSIBLY PHOTOCHROMIC SENSOR PIGMENTS–II. CHROMOPHORE ROTATION IN IMMOBILIZED PHYTOCHROME
Authors: Sundqvist Christer , Björn Lars Olof
Published: January 2008

‐Large phytochrome immobilized via anti‐phytochrome immunoglobulin bound to Sepharose beads was irradiated to saturation with unpolarized far‐red light. The apparent absorbance level was recorded in a dual wavelength spectrophotometer with both measuring beams set to either 660 or 730 nm and polarized perpendicular to each other. The sample was then irradiated with red polarized light. The apparent change in absorbance obtained after this irradiation indicated that purified phytochrome could show linear dichroism. From the absorbance values obtained it was computed that the direction of the long‐wavelength transition moment changes by either 32 or 148o, when phytochrome is transformed from Pr to Pfr. Considering the model of Hahn and Song (1981) the latter value appears more likely. In light of these results, the conclusions drawn from in vivo experiments on action dichroism in Dryopteris (Etzold, 1965), Adiantum (Kadota et al., 1982) and Mougeoutia (Haupt. 1970), which point to a 90o rotation. should be reconsidered.
A COMMENT ON SPECTRAL TRANSMITTANCE IN MAMMALIAN SKELETAL MUSCLE
Authors: Preuss L. E. , Bolin F. P. , Cain B.W.
Published: January 2008

Spectral transmittance studies, related to photoradiation therapy light dosage, were carried out in vitro on mammalian skeletal muscle with expanded beam, broad band, white light (420‐1100 nm). Spectra were collected by an EG&G 550/555 spectroradiometer with a 550‐2A silicon detector. Bovine striated muscle imposes heavy absorption and distinct spectral structure, reflecting tissue absorption maxima at short wavelengths. Transmission above 650 nm is improved by a 10' factor, relative to blue light, in 1 cm of muscle. Half value layers were 0.82 mm in the 630 nm region, and were sensitive to tissue composition. Bovine muscle exhibited spectral effects related to the cadaver studies done by Wan et at. (1981b) but show singular differences, due primarily to complex tissue composition encountered in cadaver wall measurements, as contrasted with simple muscle. Spectral transmittance is a function of wavelength, tissue type and thickness.