bluuebunny/crossref_metadata_2025 huggingface dataset:
THE SENSITISING EFFECT OF A SUNSCREENING AGENT, p‐AMINOBENZOIC ACID, ON NEAR UV INDUCED DAMAGE IN A REPAIR DEFICIENT STRAIN OF ESCHERICHIA COLI*
Authors: Hodges N. D. M. , Moss S. H. , Davies D. J. G.
Published: January 2008

Abstract. The use of repair deficient strains of bacteria for detecting mutagenic properties of chemical species is now an established technique. In this paper we present inactivation results obtained with Escherichia coli K12 AB2480 (uvr A rec A) which indicate that p‐aminobenzoic acid, a common component of sunscreening formulations, may increase the frequency of lethal damage induced in DNA when cell populations are exposed to near ultraviolet radiation.

Preliminary experiments, utilising the selective action of photoenzymatic repair, indicated that the sensitisation to near ultraviolet radiation is partially but not wholly due to increased formation of pyrimidine dimers.
FLUORESCENCE SPECTROSCOPY OF A P700‐CHLOROPHYLL‐PROTEIN COMPLEX*
Authors: Brown Jeanette S.
Published: January 2008

Abstract. Chlorophyll‐protein complexes enriched in the Photosystem I reaction center chlorophyll (P700) exhibit a fluorescence emission maximum at 696 nm at ‐ 196°C The height of this 696 nm emission relative to the emission at 683 nm from antenna chlorophyll a increases proportionally with the P700 concentration while the total fluorescence yield of the complex decreases. The 696 nm emission could possibly be from an absorbing form of antenna chlorophyll a that may be somewhat enriched along with P700 in Photosystem I fractions. However, evidence resulting from glycerol treatment which appears to decrease the rate of resonance energy transfer between antenna chlorophyll and P700 favors the hypothesis that the emission comes from a photooxidized P700 dimer (Chl+‐Chl) absorbing near 690 nm. In turn, this fluorescence evidence provides additional support for the model of a P700 dimer involving exciton interaction. Absorption in the wavelength region of 450 nm specifically excites emission at 696 nm from the P700‐chlorophyll complex.
UNSCHEDULED DNA SYNTHESIS IN FROG LENS AT 5°C
Authors: Jose Jule G. , Yielding K. L.
Published: January 2008

Abstract. Unscheduled DNA labeling occurs in the frog even at low temperatures. We conclude, tentatively, that the UV‐induced labeling observed in these cold incubated lenses represents repair synthesis of DNA.
THE ENHANCEMENT OF PHYTOCHROME ACTION ON BARLEY LEAF UNFOLDING BY INTERMITTENT LIGHT
Authors: Deutch Bente , Deutch Bernhard I. , Galston Arthur W.
Published: January 2008

Abstract. The phytochrome controlled unfolding of etiolated barley leaves proceeds best if orange light (0.6 J/m2/s; 625 ± 25 nm) is given as two appropriately timed short pulses rather than as a single longer light period.
THE SOLID STATE LUMINESCENCE OF ESTROGENS
Authors: Weinreb A. , Werner A. , Kalman Z. H.
Published: January 2008

Abstract. The luminescent behavior of certain estrogens in the solid state is discussed. Spectra of solid films of estradiol and estriol are red shifted compared to that in liquid solutions with estriol shifted to a lesser extent. The red shifts are attributed to intermolecular hydrogen bonding, this conclusion being based on IR spectra and X‐ray data. The calculated distance over which hydrogen bonding takes place is 2.755 Å in estradiol and 2.638 Å in estriol. The increased shift in the spectrum of estradiol is believed to be due to an additional hydrogen bond with a water molecule present in the solid film (O—O distance 2.793 Å). In estrone the weak fluorescence present in liquid solution is absent in solid film, in contrast to 3‐desoxyestrone where fluorescence is preserved. Out of three possible forms of crystalline estrone only two can form hydrogen bonds, based on O‐O distance calculations. In equilenin, which is highly fluorescent in liquid solution, no fluorescence is detected in solid film. This again is attributed to hydrogen bonding between the hydroxyl group of the β‐naphtholic chromophore and the carbonyl group in the C(17) position. Dihydroequilenin which lacks the carbonyl group and equilenin dissolved in a host crystal retain their fluorescence.
EFFECT OF PARAMAGNETIC SPECIES ON 8‐METHOXYPSORALEN‐SENSITIZED PHOTOINACTIVATION OF BACTERIOPHAGE LAMBDA
Authors: Fujita Hitoshi , Kitakami Masazo
Published: January 2008

Abstract. 8‐Methoxypsoralen‐sensitized photoinactivation of bacteriophage lambda (Λvir) was examined in the presence of various metallic ions. Paramagnetic ions, Co2+, Ni2+ or Mn2+, strongly repressed the reaction, whereas diamagnetic ions, Ca2+ or Zn2+, exerted no influence. Significant repression was also observed in the sample solution equilibrated with air.
PHOTODESTRUCTION OF PHAEOMELANIN
Authors: Chedekel M. R. , Post P. W. , Deibel R. M. , Kalus M.
Published: January 2008

Abstract. Phaeomelanin readily decomposes by the action of UV light and oxygen. This finding may explain many of the abnormal reactions of the skin of redheads and blondes to sunlight, including their high susceptibility to skin cancer. In aqueous solution, phaeomelanin displays an EPR signal rich in hyperfine splitting, consistent with structural information.

Phaeomelanin readily, decomposes by the action of UV light and oxygen. This finding may explain many of the abnormal reactions of the skin of redheads and blondes to sunlight, including their high susceptibility to skin cancer. We have yet to identify any of the fragmentation products. Chromatographic analysis of the photolysate indicates at least 17 different compounds. Work on the reactions of phaeomelanin with superoxide, and the identification, synthesis, and physiological evaluation of these photoproducts as etiological factors in sunburn and carcinogenesis is in progress. In aqueous solutions, phaeomelanin displays an air stable EPR signal rich in hyperfine splitting. Complete analysis of this signal will provide a better understanding of the structure of the pigment.
EXTRARETINAL PHOTORECEPTION IN CHICKENS: ENTRAINMENT OF THE CIRCADIAN LOCOMOTOR ACTIVITY RHYTHM
Authors: Nyce Jon , Binkley Sue
Published: January 2008

Abstract— The Circadian locomotor activity rhythm of blinded chickens entrained to, or was synchron ized by, light in light dark cycles.
A BLUE LIGHT REACTION INVOLVING FLAVTN NUCLEOTIDES AND PLASTOCYANIN FROM PROTOSIPHON BOTRYOIDES
Authors: O'Kelley Joseph C. , Hardman John K.
Published: January 2008

Abstract— A pigment that absorbs yellow light (580 nm) appears in a cell‐free preparation of Protosiphon when it is irradiated with blue light (430 nm) in the presence of flavoprotein from Photosiphon or flavin nucleotides. The pigment has been isolated and purified. It is a protein with a molecular weight of approximately 9000 daltons. An amino acid analysis reveals that it lacks arginine and tryptophan. It is colorless when reduced and blue (absorbs at 580 nm) when oxidized. Its normal oxidation–reduction potential is + 0.37 V. It contains one copper ion per molecule and has other properties that match those of plastocyanin isolated from green cells of other species.
THE SUBUNIT STRUCTURE OF YEAST DNA PHOTOLYASE AND THE PURIFICATION OF A FLUORESCENT ACTIVATOR OF THE ENZYME
Authors: Werbin Harold , Madden John J.
Published: January 2008

Abstract— Yeast DNA photolyase purified twice by affinity chromatography was analyzed by electrophoresis on polyacrylamide gradient gels or by sedimentation velocity through 5–200/, sucrose gradients containing 0.4MKC1. Its molecular weight estimated by both these methods was130,000 and136,000, respectively. However, the enzyme dissociated into two bands having molecular weights of60,000 and85,000 when it was examined by electrophoresis on SDS polyacrylamide gradient gels. The subunit structure of the enzyme was confirmed when two absorption maxima corresponding to polypeptides of54,000 and82,500 daltons were observed in sucrose gradients run in 1.0 M KCI. Upon mixing these two fractions, a time‐dependent increase in activity occurred, demonstrating that active enzyme could be reconstituted from these subunits.

The activity of photolyase purified by affinity chromatography is enhanced by a compound (activator III) obtained from yeast by acidification, neutralization, ion exchange chromatography and gel filtration. Activator III emits at 350 and 440 nm when excited at 290 nm, and emits at 440 nm when excited at 358 nm. After acid hydrolysis, emission at 440 nm is produced only by excitation at 358 nm, indicating that it contains two separate chromophoric moieties. The chromophore excited by 358 nm light has a pK of 9–11, while the other has a pK of 4–5. Enhancement of photolyase activity by activator III at a concentration equimolar with that of the enzyme and the similarity of the fluorescent spectra of the activator and heat‐denatured photolyase suggest that the activator may be the chromophore associated with the enzyme.
UV‐INDUCED ALKALINE LABILE DNA DAMAGE IN HUMAN ADENOVIRUS AND ITS REPAIR AFTER INFECTION OF HUMAN CELLS
Authors: Rainbow Andrew J.
Published: January 2008

Abstract— UV‐induced alkaline labile viral DNA damage was detected following irradiation of adenovirus type 2 and found to be repaired following the infection of human KB cells. Human adenovirus type 2 was irradiated with various doses of UV and subsequently used to infect human KB cells in tissue culture at approximately 2 × 103 particles per cell. Before, and at various times after infection, the viral DNA was examined on alkaline sucrose gradients. Irradiated free virus DNA showed a dose dependent decrease in molecular weight compared to unirradiated virus DNA, indicating the presence of UV‐induced alkaline labile lesions. Furthermore, an increase in the molecular weight of the irradiated virus DNA was found after infection indicating that alkaline labile lesions were removed from the viral DNA by a host mediated repair mechanism. After infection, the molecular weight of the irradiated virus DNA reached a value similar to that of unirradiated virus DNA for all the UV doses studied.
CHANGES IN ULTRAVIOLET RESISTANCE AND PHOTOPRODUCT FORMATION AS EARLY EVENTS IN SPORE GERMINATION OF BACILLUS CEREUS T
Authors: Irie R.
Published: January 2008

Abstract— In order to determine the timing of the change in the state of DNA in bacterial spores during the course of germination, L‐alanine‐induced germination of Bacillus cereus spores was interrupted by 0.3 M CaCl2 as an inhibitor, and the resulting semi‐refractile spores (spores at the end of the first phase of germination) were examined on the UV‐resistance and the photoproduct formation.

Upon UV‐irradiation, these spores, still having a semi‐refractile core as observed under a phase‐contrast microscope, gave rise to mainly the cyclobutane‐type thymine dimer. It was concluded that change in the state of the spore DNA occurs early in the process of germination, i.e. before the refractility of the core was lost.

It was also found that CaCl2 markedly prolonged the duration of the transient UV‐resistant stage.
USE OF THE FLUORESCENT LANTHANIDE Tb3+ AS A PROBE FOR CATION‐BINDING SITES ASSOCIATED WITH ISOLATED CHLOROPLAST THYLAKOID MEMBRANES
Authors: Mills John D. , Hind Geoffrey
Published: January 2008

Abstract— The fluorescent properties of the rare‐earth ion, Tb3+ have been utilized to probe the nature of cation‐binding sites associated with thylakoid membranes. At low concentrations (< 100μM), Tb3+ was observed to inhibit the increase in chlorophyll a fluorescence normally seen on adding 5 mM MgCl2 (or 100 mM NaCl) to isolated, broken chloroplasts. We also observed under these conditions, the appearance of a new band around 280 nm in the excitation spectrum of Tb3+ ion fluorescence. However, similar changes in Tb3+ fluorescence could be observed in the presence of a membrane‐free preparation of chloroplast coupling factor protein (CF1). From this and other results it is concluded that changes in Tb3+ fluorescence reflect an association of the ion with CF1 followed by intermolecular transfer of excitation energy from protein ligands (possibly un‐ionized tyrosine residues) to the lanthanide. The interaction of Tb3+ with sites which control chlorophyll a fluorescence does not seem to modify Tb3+ fluorescence, suggesting that in this case, simple membrane‐bound ligands such as carboxyl or phosphate groups are involved.
CHEMILUMINESCENCE IN THE PHOTOOXIDATION OF HUMIC ACIDS*
Authors: Slawinski Janusz , Puzyna Wlodzimierz , Slawinska Danuta
Published: January 2008

Abstract— Photo‐irradiation of aqueous basic solutions of soil humic acids and synthetic melanins with UV and visible light (Λ > 320 nm) under oxygen or nitrogen atmospheres generates electronic exicted states and radicals. These processes give rise to a long‐lived chemiluminescence with emission maxima at 480–500, 570 and 615–650 nm, as well as a paramagnetic resonance (EPR) signal with g‐value at 2.006 and ΔH∼ 3Gs. Chemiluminescence intensity and EPR signals follow multistep kinetics. An increase of the ratio of OD at 260/400 nm and 400/600 nm and a decrease of amplitude of an EPR signal after prolonged photo‐irradiation were observed. Long irradiation also causes a decrease of fluorescence intensity bands with maxima at 535 nm and 495 nm (Λex 480 and 400 nm, respectively), and an increase of the short wavelength band with a maximum at 450 nm (Λex 260 nm). The data indicate that a complex chain of reactions initiated by reactive species leads to the degradation of the aromatic core of the polymers. Oxygen efficiently enhances the chemiluminescence intensity and the rate of photodegradation. The mechanism of photodegradative oxidation and chemiluminescence probably involves an energy transfer process and singlet oxygen formation. The possibility of its occurrence in nature and its significance are discussed.
PHOTOOXIDATION OF EPINEPHRINE SENSITIZED BY METHYLENE BLUE—EVIDENCE FOR THE INVOLVEMENT OF SINGLET OXYGEN AND OF SUPEROXIDE
Authors: Jahnke Leland S. , Frenkel Albert W.
Published: January 2008

Abstract— The photooxidation of epinephrine, sensitized by methylene blue or by chlorophylls, excited with red light, involves the reduction of two molecules of oxygen to hydrogen peroxide per molecule of epinephrine oxidized to adrenochrome. The initial rates of these reactions are not affected by low concentrations of catalase. In 99 mol % D2O, rates of methylene blue sensitized photooxidations are accelerated as much as 5.2 times over rates in ordinary water. Azide anion is a more effective inhibitor of this reaction in D2O than in H2O. Half maximal inhibitions are obtained by 1.3 mM azide in H2O and by 0.1 mAf azide in D2O. Isotope effects and azide sensitivities point to photooxidation of epinephrine in D2O primarily by a singlet oxygen pathway; in H2O, non‐singlet oxygen pathways become more predominant. Superoxide dismutase (SOD) markedly inhibits rates of the photooxidations in H2O and in D2O; about 25% at 10‐9M SOD, and 50% at 10‐6M SOD in H2O. In the photooxidation in H2O, both by non‐singlet and singlet oxygen mechanisms, the amount of superoxide produced is equivalent to the amount of O2 consumed in the photooxidation of epinephrine; the superoxide thus formed participates in the oxidation of epinephrine.
PEROXIDIC INTERMEDIATES IN INDOLE–SINGLET OXYGEN REACTIONS: MECHANISM OF THE C2—C3 RING CLEAVAGE OF TRYPTOPHOL*
Authors: Saito Isao , Imuta Mitsuru , Nakada Akira , Matsugo Seichi , Matsuura Teruo
Published: January 2008

Abstract— Photosensitized oxygenation of tryptophol (1) at –70°C gives the corresponding 3‐hydroperoxyindoline 2 as a primary product. Chemical and photochemical behaviors of the hydroperoxide (2) have been investigated. Photolysis and redox reactions of 2 with ferrous ion give a C2—C3 ring cleavage product 5 together with 3‐hydroxyindoline 3. A mechanism involving O—O homolysis of the hydroperoxide has been proposed. Thermal decomposition of 2 leading to 3 and 5 is also suggested to proceed via the O—O homolysis.
SINGLET OXYGEN: A MAJOR REACTIVE SPECIES IN THE FUROCOUMARIN PHOTOSENSITIZED INACTIVATION OF E. COLI RIBOSOMES
Authors: Singh Harwant , Vadasz Joseph A.
Published: January 2008

Abstract— The skin photosensitizing furocoumarins, 8‐methoxypsoralen (MOP) and 4,5′,8‐trimethylpsoralen (TMP), inactivate E. coli ribosomes in vitro, on UV irradiation at 313 nm. Purging the solutions with N2 protects the ribosomes considerably against photoinactivation (75% with MOP and 80% with TMP). In air, the ribosome photoinactivation is mainly due to singlet oxygen (1O2), since the presence of NaN3 and other 1O2 quenchers protects the system and the inactivation is enhanced in D2O. Although 1O2 dominates as the inactivating species, the possibility of additional (∼15%) minor mechanisms involving free radicals exists. However, O‐2 does not appear to be the damaging species, since superoxide dismutase does not provide any protection.

Photosensitization of the partially purified enzyme, phe‐tRNA‐synthetase with MOP or TMP shows inactivation and protection curves similar to those seen with the ribosomes. On the other hand, unfrac‐tionated tRNAphc is not photosensitized under similar conditions, although it shows self‐photosensitization. It is likely that in the furocoumarin‐sensitized ribosomes, the primary events of photoinactivation are associated with the proteins.
THE GENERATION OF HYDROXYL RADICALS IN BIOLOGIC SYSTEMS: TOXICOLOGICAL ASPECTS
Authors: Cohen Gerald
Published: January 2008

Abstract— The formation of hydroxyl radicals in vitro was studied through their reaction with 2‐keto‐4‐thiomethylbutyric acid to form ethylene gas. The autoxidation reaction of 6‐aminodopamine served as a model source of hydroxyl radicals. Ethylene production was suppressed by catalase and by superoxide dismutase, indicating that both hydrogen peroxide and superoxide were involved in the reaction. Hydroxyl radical scavengers (thiourea > benzoate > ethanol) suppressed ethylene production in good agreement with their respective rate constants for reaction with hydroxyl radicals. Urea served as a negative control. Several substituted thiourea derivatives also suppressed ethylene production to a similar degree as thiourea itself. Biologic studies centered on several cytotoxic agents whose mechanisms of action are thought to involve hydroxyl radicals. These agents included alloxan, which destroys the beta cells of the pancreas, and 6‐hydroxy‐ and 6‐aminodopamine, which destroy sympathetic nerves. Damage to tissues in vivo was blocked to varying degrees by pretreatment of animals with hydroxyl radical scavengers such as ethanol or the thiourea derivatives. In addition, hydroxyl radical scavengers blocked the action of 5,7‐dihydroxytryptamine, a neurotoxin whose effects on noradrenaline neurons were previously shown to be blocked by inhibitors of monoamine oxidase. The data indicate that these cell toxins produce their damaging actions on specific target cells through the intracellular generation of hydroxyl radicals.
CHANGES IN SUPEROXIDE DISMUTASE, CATALASE AND GLUCOSE‐6‐PHOSPHATE DEHYDROGENASE ACTIVITIES OF RABBIT ALVEOLAR MACROPHAGES: INDUCED BY POSTNATAL MATURATION AND/OR IN VITRO HYPEROXIA
Authors: Nerurkar Lata S. , Zeligs Barbara J. , Bellanti Joseph A.
Published: January 2008

Abstract— The total superoxide dismutase activity of rabbit alveolar macrophages (AM) increased twofold during the first postnatal week. This increase in superoxide dismutase activity was primarily mitochondrial and paralleled the increase in the number of mitochondria in these cells which has been previously reported. The superoxide dismutase activity of AM in culture for 18 h was significantly increased by hyperoxia; catalase activity in hyperoxic conditions was slightly adversely affected; glucose‐6‐phosphate dehydrogenase activity was increased but not significantly over control values. Hyperoxic cultures beyond 42 h decreased the total number of viable cells and the superoxide dismutase activity expressed per viable cell; the disappearance of catalase and glucose‐6‐phosphate dehydrogenase activities in this period, however, was more rapid in control alveolar macrophages than those under hyperoxia.
ARACHIDONIC ACID PEROXIDATION, PROSTAGLANDIN SYNTHESIS AND PLATELET FUNCTION
Authors: Rao Gundu H. R. , Gerrard J. M. , Eaton J. W. , White J. G.
Published: January 2008

Abstract— The initial oxygenation or peroxidation of arachidonic acid seems to be an essential step for the synthesis of cyclic endoperoxides and prostaglandins. There has been some evidence and considerable interest in the role of superoxide anion, hydroxyl radicals or singlet oxygen as a source of oxygen in the formation of the active species (free radicals). A test capable of detecting active intermediates of lipid peroxidation and useful for studying the role of free radicals has been developed. The test resulted from the discovery that vitamin E markedly enhanced the reduction of nitroblue tetrazolium (NBT) during arachidonic acid peroxidation. Intact platelets, microsomes, sheep vesicular gland enzymes or peroxidases could provide essential enzyme activity. NBT and vitamin E when added to platelet microsomes inhibited the conversion of 14C arachidonic acid to HETE, HHT and thromboxanes. The combination also inhibited aggregation of platelets stimulated by collagen, thrombin, ADP and epinephrine. Prolonged incubation with these agents at the highest concentrations used in the study caused no change in morphology and had no deleterious effect on platelet levels of adenine nucleotides and serotonin. Results of our preliminary studies suggest that NBT and vitamin E can detect intermediates of lipid peroxidation, inhibit the conversion of arachidonic acid, prevent platelet aggregation and the release reaction without damaging the platelets morphologically or biochemically. As both the agents are scavengers of free radicals and in combination exert synergistic effects, the test system may serve as a probe in various free radical mediated events and may offer some degree of protection against free radical mediated pathological processes.
GAMMA AND PULSE RADIOLYSIS STUDIES OF THE REACTION BETWEEN SUPEROXIDE IONS AND OXYHEMOGLOBIN‐METHEMOGLOBIN SYSTEM
Authors: Ferradini Christiane , Foos Jacques , Gilles Lucien , Haristoy Didier , Pucheault Jacques
Published: January 2008

Abstract— The radiolytic studies of oxyhemoglobin or methemoglobin in neutral aerated aqueous solutions with formate ions, lead to three conclusions:

The oxidation of oxyhemoglobin by O‐2 is not important. The observed low oxidation yield is probably due to the slow reaction with hydrogen peroxide produced by O‐2 disproportionation.

The reduction of methemoglobin in γ radiolysis reaches a plateau which could be explained by structural considerations.

The reduction of methemoglobin by O‐2 ions, if it occurs, is relatively slow: k= 1.4 × 103M‐1 s‐1. But a problem remains concerning the spectral characteristics of the product.
PHOTOSENSITIZED CARCINOGEN DEGRADATION AND THE POSSIBLE ROLE OF SINGLET OXYGEN IN CARCINOGEN ACTIVATION
Authors: Greenstock Clive L. , Wiebe Richard H.
Published: January 2008

Abstract— Dye sensitized photo‐oxidation of various chemical carcinogens including 2‐acetylaminofluorene, benzo(a)pyrene, 9,10‐dimethyl‐1,2‐benzanthracene and 4‐nitroquinoline‐N‐oxide has been studied in the presence and absence of oxygen. Visible light from a filtered 150 W Xe arc was used for photolysis. and carcinogen destruction was monitored spectrophotometrically. The carcinogens were solubilized in aqueous solution within micelles of various lipid‐like surfactants. Photosensitized destruction of carcinogens by several triplet sensitizers has been observed. Enhanced damage in the presence of oxygen is also found. These results are consistent with photochemical oxidative damage to carcinogens being produced in aerated solutions via the sensitizer triplet state, possibly involving singlet oxygen. These manifold reactions are catalysed by micelles which concentrate polycyclic hydrocarbons in the non‐polar environment within the micelles where the exclusion of water probably increases reactive species lifetimes. This model photochemical system mimics the aerobic metabolic activation of chemical carcinogens, which in part is believed to be mediated by various forms of activated oxygen.
ON THE REACTION OF SINGLET MOLECULAR OXYGEN WITH N‐ALLYLTHIOUREA IN AQUEOUS SOLUTION
Authors: Kraljic I. , Kramer H. E. A.
Published: January 2008

Abstract— Experiments on the photooxidation of N‐allylthiourea, thiourea, and N‐allylurea sensitized by the dye phenosafranine show that in N‐allylthiourea the thiourea group is the site of singlet oxygen attack, while the allyl moiety neither reacts with nor quenches this metastable form of O2 (in neutral aqueous solutions). Low concentrations of N‐3 (a known quencher of singlet oxygen) strongly reduce the photooxidation of allylthiourea by a mechanism which apparently obeys simple competition kinetics. From these results the rate constant of the reaction between allylthiourea and singlet oxygen is obtained (k= 4 × 106M‐1 s‐1; pH = 7.1).
PHOTODEGRADATION OF THE IMIDAZOLE RING INDUCED BY INDOLE DERIVATIVES IN OXYGEN‐FREE AQUEOUS SOLUTIONS
Authors: Hasselmann C. , Pigault C. , Santus R. , Laustriat G.
Published: January 2008

Abstract— An imidazole ring photodegradation induced by indole derivatives in oxygen‐free aqueous solutions (Λexc= 254 nm) was demonstrated and studied in various systems at low concentration (0.2 mM). The degradation rate was maximal in the indole‐imidazole system and decreased when a substituent was present on either or both rings. The degradation rate also depended on pH (maximal at pH ˜ 6) and on imidazole concentration. Results obtained under N2O atmosphere, in the presence and absence of 1 M t‐butanol, indicate that the imidazole degradation is promoted by hydrated electrons photogenerated by the indole chromophore. Kinetic analysis of the data confirms this mechanism.
ANTIGENICITY OF DNA INDUCED BY PHOTOADDITION OF 8‐METHOXYPSORALEN
Authors: Zarebska Z. , Jarȩbek‐Arzelska M. , Rzȩsa G. , Chorzelski T.
Published: January 2008

Abstract— Rabbits immunized with sonicated DNA UV‐irradiated (365 nm) in the presence of 8‐methoxypsoralen (8‐MOP) produced a specific antiserum directed against DNA‐8‐MOP‐photoadduct. None of the long chain DNA preparations modified photochemically in the same way elicited an immunological response, although all of them gave a positive immunodiffusion test on agarose with the antiserum directed against DNA‐8‐MOP‐photoadduct. A positive reaction has also been demonstrated in the indirect immunofluorescence test, using as a source of cellular native DNA Crithidia luciliae cells treated with 8‐MOP and irradiated at 365 nm (UVA). A possible use of the specific antiserum for detecting the formation of DNA‐8‐MOP‐photoadduct, in the skin and/or lymphocytes of patients with psoriasis treated by combination of 8‐MOP and UVA irradiation, is suggested.
IN SlTU ESTIMATION OF SPATIAL DISTRIBUTION OF PHYTOCHROME ALONG THE AXIS OF THE ACTINIC BEAM
Authors: Fukshansky Leonid
Published: January 2008

Non‐stationary photoconversions of the two forms of the photochromic sensory plant pigment phytochrome are theoretically analyzed. It is shown that from actual in situ measurements of changes of absorbances caused by these photoconversions in a sequence of exposures to actinic light, one can calculate the spatial distribution of phytochrome along the path of the actinic beam.

The necessary condition of such a calculation is the existence of a screen with a known spatial distribution, which must be obtained in an independent experiment. Thus, the possibility is proved to measure, instead of phytochrome spatial distribution, that of the screen which is a much larger chemical and optical body inside the object.

Expressions to calculate the spatial distribution of phytochrome and to estimate the errors involved are presented in the present paper.
DIFFERENTIAL EFFECT OF CALCIUM ON CHLOROPLAST MOVEMENT IN MOUGEOTIA
Authors: Wagner Gottfred , Klein Karin
Published: January 2008

The flat, ribbon‐shaped chloroplast in the filamentous green alga Mougeotia sp. undergoes light‐induced orientational movement controlled by an intracellular tetrapolar gradient of the active form of phytochrome, Pfr. Some substructural and physiological aspects of this reaction were studied. An intracellular pattern of microfilaments (diameter: 5–10nm), presumably related to chloroplast movement, was identified in situ. In addition, it could be shown that chloroplast movement decreases parallel to a nitric acid soluble fraction of intracellular calcium. These results might indicate that phytochrome governs chloroplast movement in Mougeotia via control of the binding state of calcium.
SPECTRAL DEPENDENCE OF A SINGLE AND A SUBSEQUENT SECOND LIGHT PULSE INDUCING BARLEY LEAF UNFOLDING
Authors: Deutch Bente , Deutch Bernhard I.
Published: January 2008

The unfolding of etiolated barley leaves was induced by two short pulses of light separated by a dark interval. For certain wavelengths of light the effect of the “second light pulse was enhanced when the pulse was given after a 300–2000 s dark interval as compared with its effect when the two light pulses were given simultaneously. We investigated the spectral dependence of the effect of the first, inducing light flash and of the effect of the second Light flash given after a 500 s dark interval. The spectral actinity for the effect of the first flash showed phytochrome involvement. The spectral actinity for the effect of the second light flash, however, was shifted towards shorter wavelengths and the inductive action of red and far red light was attenuated.
LIGHT REQUIREMENTS FOR THE ENHANCED SYNTHESIS OF A PLASTID mRNA DURING SPIRODELA GREENING
Authors: Gressel Jonathan
Published: January 2008

A plastid mRNA (5 × 105 mol wt) appears as a burst 3 h after white light greening of steady state dark grown plants of Spirodela oligorrhiza. In this species, chlorophyll synthesis begins after 12 h. The light requirement is different from the pulse of far‐red reversible red light required to abolish the lag of chlorophyll synthesis in many species, including Spirodela. Continuous high energy far‐red is not stimulatory. When the illumination is not continued throughout the time of incorporation, the stimulation is minimal. Low energy blue and red light are stimulatory, and green and far‐red light are ineffectual. Blue light was > 5 times as effective as red light at many dose levels. Illumination with 3 × 1017 quanta/m2/s (50pEm/cm2/s) blue light at 476 nm gave about half maximum stimulation.
THE MODE OF INTERACTION BETWEEN BLUE (UV) LIGHT PHOTORECEPTOR AND PHYTOCHROME IN ANTHOCYANIN FORMATION OF THE SORGHUM SEEDLING
Authors: Drumm H. , Mohr H.
Published: January 2008

Two non‐photosynthetic photoreceptors (phytochrome and a blue light photoreceptor) are involved in light‐mediated anthocyanin synthesis in the mesocotyl of Sorghum seedlings. The present study was undertaken to investigate the kind of interaction between phytochrome and the blue light photoreceptor. The data show that phytochrome (Pfr) can only act once a blue light effect has occurred. On the other hand, the blue light effect cannot express itself without Pfr. It is concluded that there is an obligatory dependency (or sequential interaction) between the blue light effect and the light effect occurring through phytochrome, although the blue light photoreaction per se is not affected by the presence or absence of phytochrome. The latter statement is based on the results of dichromatic experiments, i.e. simultaneous, high fluence rate irradiation with two kinds of light. Blue light can be replaced by UV light. It is not clarified yet whether the effect of blue and UV light is due to the same photoreceptor.
PICOSECOND LASER PHOTOLYSIS OF SQUID RHODOPSIN AT ROOM AND LOW TEMPERATURES
Authors: Shichida Yoshtnori , Kobayashi Takayoshi , Ohtani Hiroyuki , Yoshizawa Tôru , Nagakura Saburo
Published: January 2008

Abstract. Squid rhodopsin extracted with 2% digitonin (pH 10.5 or 7.0) was excited with a 347 nm light pulse from a mode‐locked ruby laser at room temperature. Within 19 ps after the excitation, absorbance at 430 nm due to hypsorhodopsin increased and subsequently decreased with a decay time of 45 ± 10 ps. Absorbance at 550 nm due to bathorhodopsin increased with a rise time of 50 ± 10 ps. These results are the first observations of hypsorhodopsin at room temperature and clearly show that hypsorhodopsin is a precursor of bathorhodopsin which has been considered to be the earliest photoproduct in the photobleaching process of rhodopsin.

Hypsorhodopsin appeared with a rise time of 70 ± 10 ps at 421 nm at liquid nitrogen temperature without any bathorhodopsin being observed during the formation of hypsorhodopsin. An experiment using an N2 laser showed that squid bathorhodopsin converted to lumirhodopsin with a decay time of about 300 ns at room temperature.
THE CHEMISTRY AND BIOLOGY OF BACTERIAL LIGHT EMISSION
Authors: Hastings J. W.
Published: January 2008

Abstract—Bioluminescent bacteria may be isolated from sea water, and grown on a medium containing fish (or meat or yeast) extract. Cells harvested at the peak of luminescence can be lysed osmotically, releasing into the medium the soluble enzyme bacterial luciferase, which catalyzes the bioluminescent oxidation of reduced riboflavin 5′‐phosphate and long chain aldehyde by molecular oxygen. Luciferase is the simplest possible heterpolymeric protein, with an α (catalytic, 42,000 daltons)‐β (regulatory, 37,000 daltons) dimeric structure. Luciferase is not constitutive; it is induced by a substance produced by the bacteria themselves and excreted into the medium. Control also involves repression (glucose) and cyclic nucleotides.

Recent work has resulted in the characterization of an intermediate in the light emitting reaction postulated to be luciferase‐bound 4a‐peroxy‐dihydro FMN. The final steps in the in vitro light‐emitting reaction involve reaction of this peroxy intermediate with aldehyde in a mixed function oxidase‐type reaction, yielding an excited luciferase‐flavin and long chain acid. The excited state is postulated to be the luciferase‐bound 4a‐hydroxy‐dihydro‐FMN. Although the identity of the in vivo aldehyde, its localization and its metabolism is unknown, studies with mutants which fail to synthesize aldehyde suggest that the 14 carbon fatty acid is a precursor. Moreover, although bacterial luciferase is highly soluble (200 mg ml‐1 in aqueous solution) there is recent evidence from our laboratory and others that its function may involve the cytoplasmic membrane.

The function of light emission is of particular interest since a considerable amount of energy is involved; assuming a quantum yield of 10%, the cell foregoes the production of about 60 ATP molecules per photon. A fully induced cell emits about 104 quanta/s and about 20% (!) of the oxygen consumption of the cell has been estimated to go via the light emitting pathway. One function is in light organs of higher organisms, where they occur as symbionts. The inducible (and repressible) nature of the luminescent system may be appreciated in terms of ecological options; the bacteria may be biologically very versatile. Induction by an inducer produced by the bacteria themselves would occur only under conditions where it accumulates, as in a luminous organ of a host. In the open ocean such an accumulation does not occur; the luminous system would thus not be synthesized and energy loss via luminescence is averted, allowing the bacteria to compete in an alternate “life style”.
ON THE ROOM TEMPERATURE PHOSPHORESCENCE OF WOOL KERATIN
Authors: Leaver Ian H.
Published: January 2008

Abstract—A study has been made of the room‐temperature phosphorescence behaviour of wool keratin and its major constituent proteins. The 290 nm induced phosphorescence of wool, previously thought to decay by second‐order kinetics, is shown to consist of two separate components which decay exponentially with lifetimes of 0.18 × 0.03 and 1.45 × 0.25 s. Selective oxidation of the tryptophyl residues eliminates the long‐lived phosphorescence, but has no effect on the short‐lived component. The latter is variable in its intensity, and depends upon the history of the fibre. The origins of the different emissions are discussed, and the possible involvement of the phosphorescent species in the photochemical reactions leading to discoloration of the fibre are considered.
ABSENCE OF PHOTOREACTIVATION OF PYRIMIDINE DIMERS IN THE EPIDERMIS OF HAIRLESS MICE FOLLOWING EXPOSURES TO ULTRAVIOLET LIGHT*
Authors: Ley Ronald D. , Sedita B. Ann , Grube Donald D.
Published: January 2008

Abstract—The influence of photoreactivating light on the fate of UV‐induced DNA damage has been measured in the epidermis of hairless mice using damage‐specific endonuclease from Micrococcus luteus. Groups of mice were exposed to varying fluences of UV at 297nm or from an FS40 fluorescent sun lamp to induce UV photoproducts. The same fluence‐dependent DNA damage was observed in high molecular weight epidermal DNA regardless of whether the mice were killed immediately, or maintained in the dark or under photoreactivating light for 20 h after UV. Thus, no detectable photoreactivation of UV‐induced pyrimidine dimers could be demonstrated in mouse epithelial cells in vivo.
SENSITIZED PHOTOOXIDATION OF AMINO ACIDS: EFFECTS ON THE REACTIVITY OF THEIR PRIMARY AMINE GROUPS WITH FLUORESCAMINE AND O‐PHTHALALDEHYDE
Authors: Straight Richard , Spikes John D.
Published: January 2008

Abstract— The photooxidation of his, met, trp and tyr with methylene blue and eosin as sensitizers resulted in a loss of primary amine reactivity as measured with fluorescamine and o‐phthalaldehyde. The rates of oxygen uptake and of loss of primary amine reactivity with illumination was characteristic for each amino acid. Glycine did not photooxidize and showed no change in primary amine reactivity. Primary amine reactivity of the N‐acetyl derivatives of these amino acids was negligible and during photooxidation the reactivity increased slowly with N‐acetylhis and N‐acetyltrp while the reactivity of N‐acetylmet and N‐acetyltyr did not change. Imidazole and indole also showed a slow increase in primary amine reactivity during sensitized photooxidation. The rate of oxygen uptake and primary amine reactivity loss during the sensitized photooxidation of his and met was markedly increased in deuterium oxide. This indicated that singlet oxygen was involved. Radical scavengers did not affect the rates indicating that free radical intermediates were not involved. Primary amine reactivity loss is probably due to intra‐ and/or inter‐molecular secondary dark reactions between unknown initial oxygenation products and primary amino groups.
ALLOPHYCOCYANIN FORMS ISOLATED FROM NOSTOC SP. PHYCOBILISOMES*
Authors: Zilinskas B. A. , Zimmerman B. K. , Gantt E.
Published: January 2008

Abstract— Allophycocyanin from dissociated phycobilisomes of Nostoc sp. occurs in three spectrally identifiable forms that fractionate on calcium phosphate adsorption chromatography as: allophycocyanin (APC) I (15–20%), APC II (4&50%), and APC III (30–40%). APC I has a single absorption maximum at 654 nm, and a fluorescence emission peak at 678 nm. The absorption peaks of APC II and III are both at 650 nm, but the relative absorbance at 620/650 nm of APC III is less than that of APC II. The emission of both is maximum at 660 nm. On zone sedimentation in sucrose, their S20,w values of 6.0 ± 0.1 (APC I), 5.0 ± 0.1 (APC II), and 5.3 ± 0.2 (APC III) were comparable to the order of their elution from Sephadex G‐200. On SDS acrylamide gel electrophoresis two subunits were resolved with apparent molecular weights of 16,900 and 18,400 daltons. When stained by Coomassie blue, they were present in a ratio of 1α:1β in APC II and III, and a probable ratio of 2a:3β in APC I. The larger size of APC I may be accounted for by additional β subunits, by the presence of an additional polypeptide of 35,000 daltons, or both. Over several days, bleaching as noted by a decrease in absorbance at 650 nm, occurred in all three forms; in addition, the more pronounced bleaching at 650 nm, relative to 620 nm, results in APC III becoming spectrally identical to APC II. A trace of a fourth pigment, probably comparable to allophycocyanin‐B, was occasionally detected. The results suggest that several in vitro APC forms (sharing similar subunits) arise upon phycobilisome dissociation, and that APC I is the form most closely related to the final fluorescence emitter of intact phycobilisomes. In this form it probably serves as the bridging pigment in energy transfer from the phycobilisomes to chlorophyll.
LASER FLASH PHOTOLYSIS AND INACTIVATION OF CARBOXYPEPTIDASE A*
Authors: Lee Joon Y. , Grossweiner L. I.
Published: January 2008

Abstract— Laser photolysis of CPA at 265 nm photoionizes 3 to 4 Trp residues per molecule inactivated, leading to e‐aq and the disulfide bridge electron adduct. The electron adduct is formed by an internal process and is not involved in the activity loss. Based on this work and published photochemical and pulse radiolysis studies on CPA it is proposed that photolysis of a key Trp residue, possibly Trp 73 adjacent to zinc ligand Glu 72, mediates release of the zinc ion and consequent loss of peptidase activity.
“SUNLIGHT”‐INDUCED MAMMALIAN CELL KILLING: A COMPARATIVE STUDY OF ULTRAVIOLET AND NEAR‐ULTRAVIOLET INACTIVATION
Authors: Elkind M. M. , Han Antun , Chang‐Liu Chin‐Mei
Published: January 2008

Abstract— We have examined the relationship between the survival curves obtained with UV light (254 nm) and those obtained with a near‐UV sburce (Westinghouse Sun Lamps, FS20) simulating sunlight for cultured Chinese hamster cells, C3H mouse cells, and HeLa cells. In no case do the “sunlight” survival curves have the same shape as the UV survival curves. Also, the combined lethal effects of UV and near‐UV, sunlight‐like exposures are not entirely additive. Hence, we conclude that (1) the cell‐killing photolesions induced by these radiations are at most only partly the same, and (2) in view of (I), caution should be exercised in predicting near UV‐induced dose‐dependencies of other end points based upon observations with UV.
COMPLEX CHARGE RECOMBINATION KINETICS OF THE PHOTOTRAP IN RHODOSPIRILLUM RUBRUM*
Authors: Morrison Larry E. , Loach Paul A.
Published: January 2008

Abstract— The dark decay kinetics of excited phototraps in chromatophores prepared from Rhodospirillum rubrum have been quantitatively measured under two different conditions where a direct return of the electron(s) from ubiquinone to the primary donor bacteriochlorophyll cation radical is expected. One of these experimental conditions was with a frozen sample (whole cells, chromatophores, and extracted chromatophores) at 77 K, while the other was a room temperature measurement of a sample of chromatophores from which the loosely bound ubiquinone was first removed by extraction with organic solvents. Results with the latter system were also compared to those obtained with chromatophores plus 1 mM o‐phenanthroline. In all cases the kinetics of charge recombination were not pseudo‐first order but showed a biphasic pattern. The data at low temperature could be exactly fit by assuming that two major pseudo‐first order processes were occurring with half times of 6.5 and 19 ms, 22% decaying by the faster process and 78% by the slower process. Both types of experiments at room temperature could also be fit by assuming two major pseudo‐first order processes were occurring, but with somewhat slower half times, 22 and 59 ms. In this case, 20% decayed by the faster process and 80% by the slower process. An equation was developed to fit the data assuming that one ubiquinone molecule was the electron acceptor for two donor units (the duplex model), the dark decay thus taking place in two sequential steps with 50% of the oxidized donor units becoming reduced in each step. The experimental data could be exactly fit using this equation and the above parameters. The data are viewed as best supporting the duplex model for explaining primary photochemical events in these bacteria.
PHYTOCHROME VARIATION AND REVERSION IN LEMNA MINOR, L. GIBBA G3 AND L. PAUCICOSTATA 6746
Authors: Rombach J.
Published: January 2008

Abstract— Dual wavelength phot00ometry showed an increase of phytochrome in darkness in partially etiolated plants of three heterotrophically cultured Lemna species. In all three species, Pfr formed by a brief illumination decreased in subsequent darkness with half‐lives of 2–6 h. In L. minor and L. gibba, dark reversion was observed during the first 8h of darkness; in L. paucicostata, however, only when the plants were in a slightly anaerobic condition. Under continuous illumination, phytochrome decay was not influenced by light intensity. Actinic doses of far red resulted in non‐photoreversible changes of absorbance. In material exposed to red for longer than 12 h, these changes increased after preceding actinic doses of red light. This effect may result in erroneous phytochrome estimations.
MULTIPLE PATHWAYS OF DNA REPAIR IN BACTERIA AND THEIR ROLES IN MUTAGENESIS*
Authors: Smith Kendric C.
Published: January 2008

Abstract— In bacteria, three processes of DNA repair are known: photoreactivation, excision repair, and postreplication repair. Photoreactivation, the enzymatic splitting of cyclobutyl pyrimidine dimers in situ, is mediated by exposure of the enzyme‐dimer complex to near‐UV and visible light. This repair process appears to be error free. The excision repair of UV‐induced DNA base damage has been divided into two major pathways on the basis of both physiological requirements and genetic control. The major pathway requires a functional pol A gene, does not require complete growth medium. and appears to be largely error‐free and to produce short patches during repair. The second pathway requires complete growth medium and functional recA, recB, recC, lexA, uvrD, and polC genes, and appears to be mutagenic and to produce long patches during repair. There exists a second type of excision repair in which the modified base is removed by an N‐glycosidase, and the chain is then nicked by an apurinic (apyrimidinic) acid endonuclease. Subsequent events are presumed to be similar to the above excision repair process. The postreplication repair system has been divided into at least four separate pathways. Three of these are dependent upon functional recB, lexA, and uvrD genes, respectively, and appear to be error free. A fourth pathway depends upon the above gene products, but is blocked by postirradiation treatment with chloramphenicol, and may be the UV‐inducible, errorprone, mutagenic pathway of repair (“SOS repair”). A possible fifth pathway depends upon a functional recF gene, and is independent of the recB+‐dependent pathway. Mutagenesis appears to be the result of error‐prone DNA repair, and there is growing evidence that carcinogenesis is also the result of error‐prone DNA repair.
PHOTOLYSIS MECHANISM OF AQUEOUS TYROSINE AND TYROSYL PEPTIDES*
Authors: Baugher J. F. , Grossweiner L. I.
Published: January 2008

Abstract— Laser flash photolysis at 265 nm has been employed for measuring the initial hydrated electron (e‐aq) and p‐alanylphenoxyl radical (Tyr) in aqueous Tyr, small Tyr peptides and R Nase A. The results indicate that monophotonic photolysis not involving the fluorescent or triplet states is the principal initial process. Equivalent yields of e and Tyr were found in all cases except Tyr, where the Tyr yield was 60% higher than e‐aq attributed to splitting of the phenolic bond. Computer analysis of e‐aq and Tyr decays for Tyr indicates the importance of electron‐radical recombination in competition with electron scavenging and bimolecular radical‐radical reactions. Evidence for intramolecular electron migration has been obtained in cystinyl‐bis‐Tyr.