bluuebunny/crossref_metadata_2025 huggingface dataset:
PHOTOINHIBITION OF PHOTOSYNTHESIS IN NATURAL WATERS*
Authors: Smith Raymond C. , Baker Karen S. , Holm‐Hansen Osmund , Olson Robert
Published: January 2008

Abstract— A quantitative analysis of the wavelength‐dependent influence of solar irradiance on natural phytoplankton photosynthesis has been made. The effect on productivity due to several different UV radiation regimes has been measured. In the course of this analysis, it has been shown that the biological weighting function for photoinhibition of chloroplasts (Jones and Kok, 1966) allows the calculation of a biologically effective dose which is consistent with the measured photoinhibition in natural phytoplankton populations. The ecological implications of a change in available UV radiation, possibly due to anthropogenic altering of the ozone layer, are explored and it is found that the present static bottle l4C technique of measuring in situ phytoplankton productivity does not lend itself to assessing accurately the potential ecological consequences of possible increased MUV (middle ultraviolet radiation in the 280–340 nm region) on phytoplankton populations. A small change in MUV has a relatively minor effect on photoinhibition dose rates whereas it has a large potential effect on DNA dose rates.
DIFFERENT CHROMATOGRAPHIC BEHAVIOR OF A THYMINE‐CONTAINING NEW ULTRAVIOLET PHOTOPRODUCT AND SPORE PHOTOPRODUCT
Authors: Cabrera‐Juarez Emiliano , Setlow Jane K.
Published: January 2008

Abstract— One‐ and two‐dimensional cochromatography in five different solvents of a near UV photo‐product induced by 365 nm irradiation of DNA in aqueous solution and the ‘spore photoproduct’, 5‐thyminyl‐5,6‐dihydrothymine, produced by 254 nm irradiation of dry DNA, indicate that the two photoproducts seem to have related structures but are different.
PHOTOREACTIVATION OF ICR 2A FROG CELLS AFTER EXPOSURE TO MONOCHROMATIC ULTRAVIOLET RADIATION IN THE 252–313 nm RANGE
Authors: Rosenstein Barry S. , Setlow R. B.
Published: January 2008

Abstract— Exposure of ICR 2A frog cells to photoreactivating light after treatment with monochromatic ultraviolet (UV) radiation in the 252–313 nm range resulted in an increase in survival with similar photoreactivable sectors for each of the wavelengths tested. As photoreactivating enzyme is specific for the repair of pyrimidine dimers in DNA, these findings support the hypothesis that these are critical lesions responsible for killing of cells exposed to UV radiation in this wavelength range. The action spectra for cell killing and production of UV‐endonuclease sensitive sites were similar to the DNA absorption spectrum though not identical. Because the number of endonuclease sensitive sites is a reflection of the yield of pyrimidine dimers, these data also suggest that the induction of dimers in DNA by UV radiation in the 252–313 nm range is the principal event leading to cell death.
GRAPHICAL ESTIMATION OF CROSS SECTIONS FROM FLUENCE‐RESPONSE DATA
Authors: Lipson Edward D. , Presti David
Published: January 2008

Abstract— Light‐induced absorbance changes have been studied by several investigators as a potential assay for the blue‐light receptor pigments in numerous organisms. These studies involve a flavin‐mediated photoreduction of a cytochrome. Here we consider several alternative models for the photochemical kinetics linking the flavin excitation to the cytochrome absorbance change. Straightforward approximations from these models form the basis of a simple graphical procedure which, when applied to fluence‐response data, leads to an estimate of the quantum efficiency for the production of the absorbance change. Such estimates are helpful in evaluating the relevance of this spectrophotometric effect to the physiological responses. Efficiencies of order unity are indicated for results on Neurospora and corn compared to a much lower efficiency for a mycelial preparation of Phycomyces.
MULTIPLE EFFECTS OF UV RADIATION (265–330 NM) ON FUNGAL SPORE EMERGENCE
Authors: Owens Olga v. H. , Krizek Donald T.
Published: January 2008

Abstract—

We have investigated the influence of narrow‐band UV radiation, 265–330 nm. on germination of spores of the fungus Cladosporium cucumerinum Ellis and Arth., using a Xe arc lamp and filters. Reciprocity of time and dose rate was demonstrated when fungal spores were subjected to UV radiation at 325 nm but failed to hold at 265 nm. Based on these findings, data on fluence response, and partial action spectra, we propose that there are two biologically active sites in this organism that are affected by radiation between 265 and 330 nm and that might be influenced by changes in the stratospheric ozone layer: a short‐wave‐sensitive site (265–295 nm) and a long‐wave‐sensitive site (300–330 nm). Data obtained with narrow‐band interference filters confirmed previous reports of damage to nucleic acid from UV at 265–295 nm and in addition demonstrated significant inhibition by UV at 300–320 nm. Further studies of the 300 330 nm portion of the spectrum, using combinations of plastic and glass filters, showed that the influence of UV radiation in this region was primarily to produce a non‐photoreactivable delay in germ‐tube emergence.
POLAROGRAPHIC DETECTION OF AN ENDOGENOUS REDUCTANT GENERATED DURING FLASH ILLUMINATION OF CHLOROPLASTS
Authors: Jursinic Paul
Published: January 2008

Abstract—

A Joliot‐type polarographic electrode with the platinum surface biased 200 mV positive with respect to the Ag/AgCl junction was found to give a signal upon flash illumination of chloroplasts. The presence of either methyl viologen or ferricyanide as electron acceptors greatly enhanced the positivebias signal. By varying the electrode bias, a polarogram is obtained of this positive‐bias signal. A half‐wave reduction potential of 340 mV indicates that this signal is not due directly to superoxide (O‐2) nor the direct interaction of reduced methyl viologen or ferrocyanide with the electrode. Instead, the reduced exogenous acceptors act as intermediates in the generation of superoxide, and superoxide reduces an unidentified acceptor which is endogenous to chloroplasts, has a 340 mV redox potential, and gives rise to the positive bias polarographic signal. The extent of intersystem electron carrier oxidation can be changed by varying electrode bias with ferricyanide present. As the platinum is made more positive than 250 mV with respect to the Ag/AgCl junction, P700 becomes largely oxidized during 5 min dark adaptation.
INTERMEDIATES IN THE ROOM TEMPERATURE FLASH PHOTOLYSIS AND LOW TEMPERATURE PHOTOLYSIS OF PURINE SOLUTIONS
Authors: Arce R. , Jimenez L. A. , Rivera V. , Torres C.
Published: January 2008

Abstract—

The flash photolysis of purine in acetonitrile and in water at different pH was studied. The transients produced on flash excitation of degassed aqueous solutions have been identified as the triplet excited state, the hydrated electron, a purine radical cation and radical anion on the basis of quenching experiments and comparison to transients observed in low temperature photolysis.
ON THE MECHANISM OF PHAUSIS SPLENDIDULA BIOLUMINESCENCE
Authors: Pagel Roswitha , Wulff Karl
Published: January 2008

Abstract—

Evidence is presented for cross reactivity between the luciferases and luciferins of Phausis splendidula and Photinus pyralis.
PHOTOREVERSIBLE Ca2+‐DEPENDENT AGGREGATION OF PURIFIED PHYTOCHROME FROM ETIOLATED PEA AND RYE SEEDLINGS
Authors: Yamamoto Kotaro T. , Jr William O. Smith , Furuya Masaki
Published: January 2008

Abstract—

The aggregation of phytochrome purified from etiolated pea (Pisum satirum cv. Alaska) and rye (Secale cereale cv. Cougar) tissues was investigated by centrifugation and turbidimetry. Purified pea phytochrome (A669/A280= 0.88), if irradiated with red light, became precipitable in the presence of CaCl2. The precipitation upon red‐light irradiation was optimal at a Ca2‐ or Mg2+ concentration of 10–20 mM, was greater at increased phytochrome concentration or lower pH values, and was inhibited by 0.1 M KG. The precipitated phytochrome slowly became soluble after far‐red light exposure.

Turbidity of pea phytochrome solutions after red‐light irradiation also increased rapidly in the presence of either Ca2+ or Mg2+. Far‐red light exposure after the red light cancelled the turbidity increase. Rye phytochrome showed less turbidity increase than pea phytochrome and occurred only in the presence of Ca2+. Partially degraded pea phytochrome produced by endogenous proteases in the extract did not show the turbidity increase. Undegraded pea phytochrome also associated with microsomal fractions under conditions similar to those described above, but the partially degraded phytochrome did not.
SPECTRAL CHARACTERISTICS AND MECHANISM OF CHEMILUMINESCENCE FROM TRYPTOPHAN SOLUTIONS INDUCED BY UV‐IRRADIATION
Authors: Slawiński Janusz , Elbanowski Marian , Slawińska Danuta
Published: January 2008

Abstract—

The spectral distribution of the chemiluminescence, fluorescence and phosphorescence of tryptophan aqueous solutions irradiated with high and low pressure mercury lamps has been measured. The blue emission bands in the region of 380–520 nm observed both in the chemi‐ and photoluminescence, as well as an absorbance increase at 230 and 330 nm, indicate oxidative degradation of tryptophan leading to the formation of derivatives of N‐formylkynurenine, xanthurenic and anthranilic acids. Red emission bands at 630 and 705 nm in the spectrum of the chemiluminescence, an enhancement of light intensity by D2O and its decrease by NaN3 and DABCO suggest a partial contribution of O2(1Δg) to the photooxidation and chemiluminescence of tryptophan. The enthalpy of the exergonic reactions, leading to the formation of luminescing products, was calculated to average ‐270 kJ‐mol.
VIABILITY OF THE SPORES FORMED AFTER UV IRRADIATION IN DICTYOSTELIUM DISCOIDEUM
Authors: Nozu Kliichi , Ohnishi Takeo , Okaichi Kumio
Published: January 2008

Abstract—

Both abilities of germination of spores formed after UV irradiation and of growth of amoeboid cells emerged from the spores were studied on two kinds of Dictyostelium discoideum strains, NC‐4 and ys‐13.

An inhibition of germination was observed on the spores of ys‐13 when formed after UV irradiation, while no inhibition was detected on the ability of germination of spores of NC‐4. The amoeboid cells of ys‐13 emerged from the spores showed a heavy delay of growth, although no delay of growth was detected even on the amoeboid cells of NC‐4 emerged from the spores formed after UV irradiation. The strain of NC‐4 must repair UV lesions fully before spore formation, while the spores of ys‐13 must keep some UV lesions unrepaired and send them to the next generation of amoeboid cells. The characters of UV lesion inheritable through the spores to the next amoeboid cells in ys‐13 were discussed.
PHOTOREACTIVATING ENZYME FROM STREPTOMYCES GRISEUS—III. EVIDENCE FOR THE PRESENCE OF AN INTRINSIC CHROMOPHORE
Authors: Eker A. P. M.
Published: January 2008

Abstract—

Evidence is presented that DNA photoreactivating enzyme from Streptomyces griseus consists of a high molecular protein part and a low molecular chromophore which is released by denaturation. The free chromophore is highly fluorescent and has an absorption maximum at 420 nm. In native photoreactivating enzyme the chromophore fluorescence is almost completely quenched and there is an additional absorption band at 445 nm. Native photoreactivating enzyme spontaneously looses its chromophore following first order kinetics as measured by the increase of fluorescence intensity. A good correlation was found between the increase of fluorescence intensity and the decrease of biological activity, stressing the importance of the chromophore‐protein bond. The presence of DNA greatly retards the spontaneous release of chromophore, and with UV‐irradiated DNA the photoreactivating enzyme is almost completely stable. In five different chromatographic systems, cochromatography of biological activity and enzyme‐bound chromophore was found, thus ruling out the possibility that the observed chromophore belongs to a contamination in the enzyme preparation. Photoreactivating enzyme binds very strongly to Blue‐Sepharose indicating the presence of a positive charge in the polynucleotide binding site.
DNA EXCISION REPAIR IN LYMPHOCYTES FOLLOWING PHOTOAFFINITY LABELING WITH ETHIDIUM MONOAZIDE
Authors: Cantrell Charles E. , Yielding K. Lemone
Published: January 2008

Abstract—

Irradiation of ethidium monoazide by fluorescent light promotes a chemical decomposition of the azide into a highly reactive nitrene intermediate. Covalent bonding of this electrophile to the DNA in the cell provokes repair of damage which can be monitored by incorporation of [3H]‐thymidine. Human lymphocytes were labeled with [14C]‐ethidium azide and then allowed to undergo DNA repair. Repair incorporation of [3H]‐thymidine showed saturation at 5 µM ethidium azide, but excision of the labeled drug failed to saturate at 20 µM, suggesting that excision and resynthesis are two separate events. Cells were also labeled with the photosensitive drug and/or exposed to UV radiation, and then allowed to undergo a period of DNA repair. The tritium incorporation for the combined insults was less than the sum of the two insults. Quinacrine, progesterone and chloroquine inhibited repair incorporation of [3H]‐thymidine, but had no effect on the excision of the drug from the DNA. After damage by ethidium azide, chromatin was isolated from lymphocytes which had been allowed to repair label with [3H]‐thymidine. Partial digestion of the chromatin with micrococcal nuclease released 80% of the tritium when approximately 40% of the DNA had been hydrolyzed by the enzyme.
PHOTOCHEMICAL ADDITION OF L‐LYSINE TO 1,3‐DIMETHYL‐4‐THIOURACIL*
Authors: Ito Satoru , Saito Isao , Nakata Akira , Matsuura Teruo
Published: January 2008

Abstract—

Irradiation of an aqueous solution of 1,3‐dimethyl‐4‐thiouracil (1) in the presence of l‐lysine (2) with a high‐presure mercury lamp through a Pyrex filter gave a 1:1 mixture of two photoproducts. One of the products was isolated in a pure form, which on treatment with acetic anhydride‐pyridine yielded the starting material 1. Based on the spectral data (1H and 13C NMR) and the chemical reaction, the structure of the photoproduct was assigned to 3. The photochemical reaction is considered as a nucleophilic addition of l‐lysine to photoexcited 1.
THE EFFECT OF DARK COMPLEXING ON THE PHOTOSENSITIZED FORMATION OF 8‐METHOXYPSORALEN CROSS‐LINKS WITH DNA*
Authors: Grossweiner L. I. , Sherman W. V.
Published: January 2008

Abstract—

The near‐UV dose at 365 nm required for the formation of 8‐methoxypsoralen (8‐MOP) cross‐links with calf thymus DNA was found to be insensitive to the concentration ratio of nucleotides to 8‐MOP over the range 100:1 to 5:1. The proposed explanation is that only the dark‐complexed 8‐MOP contributes to the photosensitized formation of monoadducts and cross‐links. A kinetics analysis indicates that the fluence required for cross‐linking should be inversely proportional to the square root of the fraction of dark‐complexed 8‐MOP per nucleotide (the binding ratio), a quantity that is insensitive to the ratio of nucleotides to 8‐MOP. These findings predict a small dependence of photosensitivity on the total 8‐MOP concentration in cellular systems in which cross‐links are the major lethal lesion.
GENETIC CONTROL OF NEAR‐UV SENSITIVITY INDEPENDENT OF EXCISION DEFICIENCY (uvrA6) IN ESCHERICHIA COLI K12
Authors: Tuveson R. W.
Published: January 2008

Abstract—

By appropriate matings, recombinant strains carrying all four possible combinations of genes controlling near‐UV (nur vs nur+) and far‐UV (uvrA6 vs uvrA+, excision repair function) sensitivity have been constructed. Near and far‐UV inactivation experiments with the four recombinant strains reveal that inactivating events induced by near and far‐UV do not appear to overlap. These results are analogous to our previously reported experiments (Tuveson and Jonas, 1979) with recombinant strains carrying all four possible combinations of genes controlling near‐UV sensitivity (nur vs nur+) and recombination proficiency (far‐UV sensitivity, recA1 vs recA+). The results of these two sets of experiments taken together may mean that any recA+ or uvrA+ repairable lesions induced by near‐UV are repaired equally well by either system and do not require the simultaneous participation of both repair systems.
PHOTOTACTIC ORIENTATION BY THE CILIATE, STENTOR COERULEUS
Authors: Song Pill‐Soon , Häder Donat‐P. , Poff Kenneth L.
Published: January 2008

Abstract—

Stentor coeruleus exhibits negative phototaxis to visible light, in addition to a step‐up photophobic response. The negative phototaxis was established by demonstrating the swimming of Stentor toward a focused beam away from the light source. The action spectrum showed a maximum at 610–620 nm and is essentially identical to that of the step‐up photophobic response. Proton uncouplers such as micromolar concentrations of FCCP and TPMP+ inhibited the negative phototaxis.
BOOK REVIEW
Authors: Song Pill‐Soon
Published: January 2008

Physiology of Movements. Encyclopedia of Plant Physiology, New Series, Volume 7, Edited by W. Haupt and M. E. Feinleib.
PROTEIN ENHANCED INACTIVATION OF VIRAL DNA BY UV RADIATION
Authors: Larcom L. L. , Dodds and Ellen G. , McNeill William F.
Published: January 2008

Abstract Viral DNA was irradiated in the presence of proteins and assayed for loss of biological activity. Several proteins were found to enhance the inactivation of transfecting ability by UV radiation. The sensitization caused by a particular protein depends upon its amino acid composition. Experiments done at low molar ratios of protein to DNA indicate that a protein‐induced lesion could be a highly efficient means of inactivation.
INACTIVATION OF BACTERIOPHAGE LAMBDA BY NEAR–ULTRAVIOLET IRRADIATION IN THE PRESENCE OF CHLORPROMAZINE
Authors: Fujita Hitoshi , Endo Akira , Suzuki Kenshi
Published: January 2008

Abstract Bacteriophage λvir was inactivated when it was irradiated with near‐UV light in the presence of chlorpromazine. DNA strand breakage in the treated phage was indicated by alkaline sucrose gradient centrifugation. The number of the breaks was increased with increasing fluence. Although the inactivation rate was enhanced with a decreasing salt concentration in the reaction mixture and under a nitrogen atmosphere, the number of the strand breaks was not altered in either case. Therefore, the DNA strand breakage is not a sole lethal damage in the treated phage. The addition of NaN3 repressed the inactivation and the reaction in a D2O medium enhanced the inactivation even if the reaction mixture was irradiated under anaerobic conditions. Under anaerobic conditions, the inactivation occurs presumably via a radical mechanism.
SENSITIVITY OF MARINE PHYTOPLANKTON TO UV‐B RADIATION: IMPACT UPON A MODEL ECOSYSTEM
Authors: Worrest Robert C. , Wolniakowski Krystyna U. , Scott James D. , Brooker Deborah L. , Thomson Bruce E. , Dyke Henry Van
Published: January 2008

Abstract Human activities may cause a 16% reduction of stratospheric ozone. The concomitant increase in solar UV‐B radiation reaching the surface of the earth could detrimentally affect the phytoplankton that form the base of the food web in oceanic and estuarine ecosystems. In the current study acute exposure of seven species of marine phytoplankton to UV–B radiation depressed the radiocarbon estimate of primary production. A model of a marine ecosystem was constructed based on the differential sensitivities of the seven species of phytoplankton. Increasing the UV–B exposure within the model from 100 EffDNAJ/m2/day to 150 EffDNAJ/m2/day significantly altered the community composition of the ecosystem. In nature, alteration of the phytoplanktonic community structure could result in a significant impact upon successional patterns and primary producer–consumer trophodynamics.
MONOFUNCTIONAL 4′,5′‐PHOTOCYCLOADDUCT BETWEEN 4,5′‐DIMETHYLANGELICIN AND THYMINE
Authors: DallAcqua F. , Caffieri S. , Vedaldi D. , Guiotto A. , Rodighiero G.
Published: January 2008

Abstract A new fluorescent compound has been isolated from the products of hydrolysis of DNA irradiated in the presence of 4,5′‐dimethylangelicin, a monofunctional photosensitizing furocoumarin. The marked similarity of the UV absorption and fluorescence spectra of this photoproduct to those of 4′,5′‐dihydro‐4,5′‐dimethylangelicin, as well as its behaviour on photodissociation (254 nm) yielding thymine and 4,5′‐dimethylangelicin in equimolecular amounts, are consistent with a cycloadduct between one molecule of 4,5′‐dimethylangelicin and one of thymine, and the C4‐cycloaddition occurs through 4′,5′–double bond of the furocoumarin and the 5,6‐double bond of the pyrimidine.
ALTERATION OF GUANINE RESIDUES DURING PROFLAVINE MEDIATED PHOTOSENSITIZATION OF DNA
Authors: Piette J. , Calberg‐Bacq C.‐M. , Van de Vorst A.
Published: January 2008

Abstract— Mild photodynamic treatments of proflavine‐calf thymus DNA complexes induce a unique and quantitatively important alteration of the guanine residues which can be related to the lethal lesions due to the combined action of proflavine and light on phages. The ‘altered guanine’ is destroyed by HClO4 but is recovered after partial DNA depurination under the form of two photoproducts. The first product, Gox, elutes as guanine on a Sephadex column but has a modified UV absorbance spectrum. It gives rise by further irradiation to another product, X, which elutes at pH 9.7 as a pyrimidine compound and presented a maximal UV absorbance at 246 nm. Product X is also selectively released by piperidine fixation onto the photo‐damaged DNA. The guanine degradation process is markedly decreased in the presence of the singlet oxygen quencher, NaN3. The photodynamic lesion inhibits the enzymatic degradation of the DNA but generates locally denatured regions that are sensitive to S1 endonuclease.
PHOTOTAXIS IN DICTYOSTELIUM DISCOIDEUM AMOEBAE
Authors: Hong Choo Bong , Häder Maria A. , Häder Donat‐P. , Poff Kenneth L.
Published: January 2008

Abstract— An apparatus has been developed to measure phototactic movement in a population of amoebae of Dictyostelium discoideum. Fluence–response curves in white light show a positive phototaxis to light below 100mW/m2. Higher intensities cause a negative phototaxis. An action spectrum, based on the zero‐crossing points in fluence–response curves for monochromatic light, shows a major peak at about 405nm and secondary maxima at about 450, 520, 580 and 640nm. This action spectrum resembles the action spectra for accumulations of amoebae in and dispersal from light traps and that of inhibition of aggregation by light, but is distinctly different from the action spectrum for phototaxis by D. discoideum pseudoplasmodia.
THERMAL DECAY OF THE BATHOPRODUCT OF BACTERIORHODOPSIN
Authors: Mao Boryeu
Published: January 2008

Abstract— The photoproduct of bacteriorhodopsin at 77 K is a stable, bathochromically shifted species, K. K begins decaying exclusively to the next bacteriorhodopsin photocycle intermediate, L, near 90 K. The thermal transformation from K to L is estimated to have a low barrier height with an upper limit of 3.8 kcal/mol.
A SPIN LABELED RETINAL PIGMENT ANALOGUE OF THE PURPLE MEMBRANE
Authors: Renk G. , Grover T. , Crouch R. , Mao B. , Ebrey T. G.
Published: January 2008

Abstract— A spin labeled derivative of retinal (4‐[2, 2, 5,5‐tetramethyl‐l‐pyrrolidinyloxy‐3‐carboxyl]‐retinal) has been synthesized. The all‐trans‐isomer combined with the apoprotein of the purple membrane Halobacterium halobium to form a pigment which absorbs at 480 nm and which is unstable to hydroxyl‐amine. The electron paramagnetic resonance (EPR) spectrum of the pigment showed an anisotropic signal indicating immobilization of the nitroxide on the chromophore. The ester linkage on the chromo‐phore hydrolyzed in situ yielding the 4‐hydroxypigment analogue, absorbing at 540 nm, and the free 2, 2, 5,5‐tetramethyl‐l‐pyrrolidinyloxy‐3‐carboxylic acid.
LIGHT INDUCED ISOMERISATION, AT ACIDIC pH, INITIATES HYDROLYSIS OF BACTERIORHODOPSIN TO BACTERIO‐OPSIN AND 9‐CIS‐RETINAL
Authors: Fischer Ulrich Ch. , Towner Paul , Oesterhelt Dieter
Published: January 2008

Abstract— Bacteriorhodopsin (BR) from the purple membrane of Haiobacterium halobium contains covalently bound retinal in the 13‐cis and all‐trans configurations. Several forms of bacteriorhodopsin are known, with different absorption maxima which are designated as BRλmax (nm). At acidic pH, BR605 is formed from BR560. The following sequence of reactions was found, which is initiated by irradiation of BR605 with red light:

An all‐trans/13‐cis to 9‐cis isomerisation occurs in the light induced reaction BR605 ∼ BR500. BR500 seems to contain covalently bound retinal, whereas BR390 contains free retinal. By irradiation with light, BR500, BR450 and BR390 can be reconverted to BR560.
PHOTODYNAMIC DAMAGE TO EGG LECITHIN LIPOSOMES*
Authors: Muller‐Runkel R. , Blais J. , Grossweiner L. I.
Published: January 2008

Abstract— Egg lecithin liposomes were lysed by singlet oxygen (1O*2) generated by red light irradiation of oxygenated methylene blue (MB+) and by superoxide (O−2) generated by blue‐green irradiation of oxygenated riboflavin (RF) in the presence of ethylenediaminetetraacetic acid (EDTA) or reduced nicotinamide adenine dinucleotide (NADH). The MB+/O2 sensitized process is more efficient in alkaline solutions, attributed to the stabilization of the triplet state di‐cation. The small increase of the lysis efficiency from pH4 to pH9 for the RF/EDTA/O2 system suggests that HO−2 may be more damaging than O−2. Estimates based on large‐target reaction kinetics indicate that 1O*2 is about 200 times more effective than superoxide for inducing liposome lysis. Similar experiments with saturated 1‐α‐phosphatidylcholine dipalmitoyl liposomes showed no photosensitized lysis for either system.
INFLUENCE OF ELECTRIC FIELDS ON FLUORESCENCE QUENCHING OF CHLOROPHYLL a IN NEMATIC LIQUID CRYSTAL MATRIX
Authors: Fr°Ckowiak Danuta , Bauman Danuta , Betkowska Izabela
Published: January 2008

Abstract— An electric field enhances the yield of fluorescence of chlorophyll in a liquid crystal solvent. The presented data suggest that the electric field effect is caused by the decrease in the efficiency of fluorescence quenching by ions. Quenching of each polarized component of fluorescence of chlorophyll molecules oriented by the liquid crystal matrix is different. The relative increase in fluorescence yield due to the applied electric field is stronger for a fluorescence component polarized parallel to the direction of liquid crystal orientation than for the perpendicular component.
FLAVIN‐PHOTOREDUCTION BY CYANIDE: NUCLEOPHILIC ADDITION IN THE EXCITED TRIPLET STATE
Authors: Traber Rainer , Kramer Horst E. A. , Knappe Wolfgang R. , Hemmerich Peter
Published: January 2008

Abstract— Flavin photochemistry as well as biochemistry consists of competitive 1e− ‐ and 2e− ‐reduction pathways, depending on the nature of the substrate. We show that cyanide ion is a photosubstrate which suppresses 1e−‐oxidoreduction and leads to exclusive formation of 6‐ and 9‐cyano‐1,5‐dihydroflavin. The photoreduction mechanism is thus revealed as a nucleophilic addition of cyanide ion at the excited flavin triplet. Preparative photochemistry and isolation and characterization of cyanoflavins have been done, as well as thorough mechanistic studies by conventional flash photolysis. In contrast, nitrite ion is shown to be a normal photosubstrate for flavins leading to exclusive 1e− ‐transfer followed by back donation.
THE INTERACTION OF A GENE (nur) CONTROLLING NEAR‐UV SENSITIVITY AND THE polA1 GENE IN STRAINS OF E. COLI K12
Authors: Tuveson R. W.
Published: January 2008

Abstract— When stationary cell populations of the Escherichia coli W3110 strain and the polA1 mutant (p3478) derived directly from it were compared for their sensitivity to near‐UV (NUV, 300–400 nm) inactivation, the polA1 strain proved to be more sensitive. By appropriate matings and transductions, four essentially isogenic strains have been developed which carry all four possible combinations of genes conferring far‐UV (FUV, 200‐300 nm) sensitivity (polA1 vs. polA+) and NUV sensitivity (nur vs. nur+). Stationary cells of strains carrying either the polA1 or polA+ allele in combination with the nur allele are indistinguishable in their sensitivity to NUV inactivation and are equivalent in their NUV sensitivity to the original polA1 mutant strain (p3478). With the two strains carrying the nur+ allele, stationary cell populations of the polA1 strain are clearly more sensitive to NUV inactivation than is the polA+ strain. The NUV sensitizing effect of the polA1 mutation in a nur+ genetic background is about the same as that of the nur mutation at the 0.37 survival level. This may mean that the polA1 and nur mutations sensitize E. coli stationary cell populations to NUV inactivation by a common mechanism.
MUTAGENICITY OF MONOADDUCTS AND CROSS‐LINKS INDUCED IN ASPERGILLUS NIDULANS BY 8‐METHOXYPSORALEN PLUS 365 NM RADIATION
Authors: Scott Barry R. , Maley Mary Ann
Published: January 2008

Abstract— 8‐Methoxypsoralen plus 365 nm radiation induces mutation at the methionine supressor loci of Aspergillus inhibitor‐deficient conidia at low doses of near‐UV radiation with one‐hit kinetics and at higher near‐UV radiation doses with two‐hit kinetics. These results and others suggest that both monoadducts and cross‐links, formed by 8‐methoxypsoralen and DNA upon exposure to UV radiation, are capable of inducing mutation. Evidence is also presented that induced furocoumarin cross‐links are responsible for the inactivation of the Aspergillus conidium.
SPECTROFLUOROMETRIC STUDY ON PHOTOCHEMICAL INTERACTION BETWEEN CHLORPROMAZINE AND NUCLEIC ACIDS
Authors: Fujita Hitoshi , Hayashi Hiroyuki , Suzuki Kenshi
Published: January 2008

Abstract— Near‐UV irradiation of a mixture of chlorpromazine and single‐stranded nucleic acids produced a non‐dialyzable photoproduct which emitted characteristic fluorescence at around 520 nm. The same fluorescent species was also formed by the photoreaction with purine nucleotides but not with pyrimidine nucleotides. The highest photoreactivity was observed with GMP. Smaller amounts of the species were formed in a solution with a high salt concentration than in that with a low salt concentration. A higher rate was observed under anaerobic conditions than under aerobic conditions.
PHYCOBILISOMES AND ISOLATED PHYCOBILIPROTEINS. EFFECT OF GLUTARDIALDEHYDE AND BENZOQUINONE ON FLUORESCENCE
Authors: Köst H.‐P. , Rath K. , Wanner G. , Scheer H.
Published: January 2008

Abstract— The fluorescence of the biliproteins C‐phycocyanin from Spirulina platensis, B‐phycoerythrin from Porphyridium cruentum and of isolated whole P. cruentum phycobilisomes is quenched in the presence of glutardialdehyde (GA) or benzoquinone (BQ). The kinetics of fluorescence decrease thus induced is biphasic. If GA is used as a quencher, the fluorescence can be recovered at 77 K. Contrary to the GA‐effect, only a minor recovery takes place with BQ at 77 K, thus demonstrating a different mechanism of action of GA and BQ on biliproteins.
PHYSIOLOGICAL EFFECTS OF ULTRAVIOLET LIGHTON DICTYOSTELIUM DISCOIDEUM SPORE GERMINATION
Authors: Demsar Irene H. , Cotter David A.
Published: January 2008

Abstract— The spore germination in Dictyostelium discoideum consists of four stages: activation, postactivation lag, swelling and emergence. Ultraviolet irradiation (total fluence of 250 J/m2) of spores at any time prior to late spore swelling allows full swelling, but inhibits the emergence of myxamoebae. In the case of freshly activated spores, a UV exposure time of 30 s (total fluence of 50 J/m2) is sufficient to reduce emergence to about 6% when measured after 24 h of incubation. This same fluence results in about 10% viability as measured by plaque forming ability. Experiments utilizing ‘fractionated exposures’ result in the same percentage inhibition of emergence as that found for ‘single exposures’ provided the total fluence is equivalent. The higher fluences (250 J/m2) which completely prevent emergence, do not affect the endogenous oxygen uptake of spores during swelling. Ultraviolet light irradiated spores respond to the same activation and deactivation treatments as control unirradiated spores. Ultraviolet irradiation after late spore swelling allows emergence to occur in only a small fraction of the population. This fraction of cells which can emerge after UV treatment is said to have passed a ‘competence point’, which is believed to be the time when all the events necessary for emergence have been completed. Though the sites of UV inactivation in spores can only be postulated at present, it is apparent that the initial stages of germination (activation, postactivation lag and spore swelling) occur independently of the UV sensitive sites. The final stage of germination (emergence), however, is dependent on UV sensitive functions.
A CLIMATOLOGY OF SUNBURNING ULTRAVIOLET RADIATION
Authors: Berger Daniel S. , Urbach Frederick
Published: January 2008

Abstract— Data are presented from 14 sites where continuous measurements of the sun's shortest ultraviolet radiation reaching the earth's surface have been made for four or more years. Average daily dose per month and its variability from year to year is shown for each station. Some of the many influences affecting these measurements can be discerned by station intercomparisons. No consistent long term change in solar UV‐B radiation reaching the ground is evident.
KINETICS OF SIMIAN VIRUS 40 AND LAMBDA INACTIVATION BY PHOTOADDITION OF PSORALEN DERIVATIVES
Authors: Kondoleon Sophia K. , Walter Mary A. , Hallick Lesley M.
Published: January 2008

Abstract The kinetics of psora/en photoinactivation of two distinct DNA viruses, bacteriophage λ and the papovavirus SV40 were investigated. When λ is treated with near ultraviolet light (UVA, 320‐400 nm) and 4,5′,8‐trimethylpsoralen (TMP) at 1 μg/m/, the phage is rapidly inactivated. The survival curve exhibits a distinct shoulder indicating second or higher‐order kinetics. SV40, on the other hand, is much more resistant to psoralen photoinactivation and the survival curve is linear, reflecting first order or‘pseudo‐first order’kinetics. Two TMP derivatives with increased solubility in aqueous solutions, 4′‐aminomethyl‐TMP and 4′‐hydroxymethyl‐TMP, were similarly tested. In both virus systems, TMP was much more effective. In experiments designed to examine the role of psoralen cross‐link formation in virus inactivation, treated samples were irradiated a second time in the absence of drug. Since reirradiation causes a decline in λ infectivity as great as that observed in continuously irradiated samples, cross‐links are implicated as the primary lethal event. In the case of SV40, the results of such a protocol suggest that both monoadducts and cross‐links may be lethal or that monoadduct formation may be rate‐limiting.
EFFECTS OF FLUENCE FRACTIONATION ON UV‐INDUCED MALIGNANT TRANSFORMATION AND CELL KILLING IN NON‐CYCLING PLATEAU PHASE MOUSE CELLS
Authors: Chan Gerald L. , Little John B.
Published: January 2008

Plateau phase C3H 10T 1/2 mouse cells were used to measure the response to split fluence UV light irradiation in the absence of any cell cycle effects. It was found that fluence fractionation with up to 24 h between the fluences resulted in no survival enhancement. The frequency of malignant transformation was potentiated 2.5‐fold when the time interval between the fluences was greater than 4h. This potentiation of transformation was attributed to plateau phase holding rather than to fluence fractionation per se.
INTRAMOLECULAR DONOR‐ACCEPTOR SEPARATIONS IN METHIONINE‐ AND LEUCINE‐ENKEPHALIN ESTIMATED BY LONG‐RANGE RADIATIONLESS TRANSFER OF SINGLET EXCITATION ENERGY*
Authors: Kupryszewska M. , Gryczyński I. , Kawski A.
Published: January 2008

The Förster theory of radiationless electronic excitation energy transfer was used to determine the intramolecular separation between the tyrosine and phenylalanine residues in leucine‐ and methionine‐enkephalin. The spectral overlap integrals and the Förster critical distances were evaluated. Transfer efficiencies were determined by observing sensitized fluorescence of the acceptor and quenching of the donor fluorescence. The results were compared with theoretical estimations, better agreement being obtained with the first method.
PHOTOSENSITIZATION BY METHOTREXATE PHOTOPRODUCTS
Authors: Chahidi C. , Morliere P. , Aubailly M. , Dubertrei L. , Santus R.
Published: January 2008

Abstract— Photoproducts induced upon excitation of methotrexate by UV light have been separated by ion exchange chromatography. They include 2,4‐diamino‐6‐pteridinecarboxylic acid, 2,4‐diamino‐6‐pteridine‐carboxaldehyde and other unidentified pteridine derivatives. The same photoproducts can be also formed upon photodynamic reaction using hematoporphyrin as photosensitizer. In oxygen saturated aqueous solutions (pH∼7), methotrexate photoproducts sensitize the oxidation of histidine and tryptophan by UV light by a process involving singlet oxygen. In aqueous solutions containing albumin or in human serum, the same photoproducts are formed from free methotrexate but not from albumin‐bound methotrexate. In the latter case the results may suggest that methotrexate covalently binds to albumin upon excitation with UV light either in absence or in presence of oxygen. These results could explain the photosensitization accompanying cancer chemotherapy with high dose methotrexate and also the synergistic effects of PUVA + low dose methotrexate in psoriasis therapy.
INTERMEDIATES IN THE ROOM TEMPERATURE FLASH PHOTOLYSIS OF ADENINE AND SOME OF ITS DERIVATIVES
Authors: Arce R. , Rodriaguez G. , Singmaster K.
Published: January 2008

Abstract—

The transient absorption spectra of aqueous solutions of adenine, 2′‐deoxyadenosine, 2′‐deoxyadenosine‐5′‐phosphate and 2′‐deoxyadenylyl‐(3′‐5′)‐2′‐deoxyadenosine have been determinated at different pH values using conventional flash photolysis. Reactives intermediates produced in the flash photolysis of these adenine derivatives present similar absorption regions: two higher intensity bands in the UV and 560–720 nm wavelength region and a third weaker band at 420–560 nm. On the basis of the effects produced by triplet quenchers and/or electron scavengers the bands have been assigned to hydrated electrons, radical cations, radical anions and/or neutral radicals resulting from neutralization reactions of the charged radicals. The results indicate that the bases photoionize via a triplet state under these conditions.
PHOTOCHEMICAL STUDIES OF ARTIFICIAL BACTERIORHODOPSINS
Authors: Umadevi P. , SHEVES M. , Rosenbach V. , Ottolenghi M.
Published: January 2008

Abstract— Three artificial bacteriorhodopsins are prepared [from synthetic aromatic and bicyclic analogues of retinal and exposed to spectroscopic and pulsed lader photolysis studies. The spectra of the pigments, all perturbed in the ring region of the molecule, are markedly blue shifted in respect to natural bacteriorhodopsin. The shift is attributed to a decreased effect of a protein charge in the vicinity of the ring, in agreement with the point‐charge model of Nakanishi et al., 1980. The photocycles of the synthetic pigments exhibit a primary red‐shifted (K) intermediate and a blue shifted (M) transient, analogous to those observed for the natural pigment. Such observations impose considerable limitations, both on the possible chromophore conformational changes and on the effects of neighbouring protein charges associated with the photocycle.

It is concluded that only the Schiff base counter‐ion, but not the ring charge, may be associated with the generation of the primary red shifted K species. Moreover, the rigidity imposed on the polyene by the additional ring in the bicyclic analogue shows that the photocycle can not be initiated by conformational changes in the retinyl moiety up to the C9 carbon in the polyene chain. It is also observed that the K→L process in the photocycle is considerably slower in the case of the synthetic pigments. The observation is rationalized by attributing the process to a conformational change in the polyene moiety catalyzed by the ring protein charge.
FLUORESCENCE QUENCHING OF 5,10,15,20‐TETRA(p‐TOLYL)PORPHINE and ITS ZINC COMPLEX BY QUINONES. CHARGE‐TRANSFER INTERACTION and TRANSIENT EFFECT
Authors: Yamada Sunao , Sato Toshinori , Kano Koji , Ogawa Teiichiro
Published: January 2008

The fluorescent states of tetratolylporphyrin and its zinc complex in acetone were quenched by various kinds of quinones. The transient effect for the collisional quenching caused the upward deviation of the plots of the inversed fluorescence intensities of the porphyrins vs the quinone concentrations. A charge‐transfer interaction between the porphyrins in the singlet excited states and the quinones was suggested from the dependence of the quenching rate constants on the electron affinities of the quinones.
PHOTOCHEMICAL ADDITION OF AMINO ACIDS AND PEPTIDES TO POLYURIDYLIC ACID
Authors: SHETLAR MARTIN D. , CARBONE JOHN , STEADY ELAINE , HOM KELLIE
Published: January 2008

Abstract— The quantum yields for photochemical addition of glycine and the L‐amino acids commonly occurring in proteins (excluding proline) to polyuridylic acid have been determined in deoxygenated phosphate buffer at pH 7, using a fluorescamine assay technique. All twenty amino acids were found to be reactive, with cysteine, tryptophan, phenylalanine, tyrosine, arginine, lysine and methionine being the most reactive. The analogous quantum yields for a series of eighteen dipeptides of the form glycyl X (X being one of the commonly occurring amino acids, including proline), of L‐alanyl‐L‐tryptophan, of the tripeptides L‐seryl‐L‐seryl‐L‐serine and L‐threonyl‐L‐threonyl‐L‐threonine, of the tetrapeptide L‐cystine‐bis‐glycine, and of the lysine derivative Nα‐acetyllysine were also measured. All were found to be reactive toward photoaddition to poly U.
SPECTRA OF FLUORESCENCE LIFETIME AND INTENSITY OF Rhodopseudomonas sphaeroides AT ROOM AND LOW TEMPERATURE. COMPARISON BETWEEN THE WILD TYPE, THE C 71 REACTION CENTER‐LESS MUTANT AND THE B800–850 PIGMENT‐PROTEIN COMPLEX
Authors: SEBBAN PIERRE , JOLCHINE GENEVIEVE , MOYA ISMAEL
Published: January 2008

Abstract— Spectra of the fluorescence lifetime and intensity of chromatophores from the wild type Rhodopseudomonas sphaeroides, from the C 71 reaction center‐less mutant and of the B800–850 light harvesting pigment‐protein complex have been studied by phase fluorimetry techniques at different light modulation frequencies at room and low temperature.

As already known, closed reaction centers (saturating light) are still quenchers of antenna fluorescence although with a lower efficiency than when they are opened. The fluorescence yields and lifetimes of both the C 71 mutant strain and the B800–850complex are found to increase by about 30% between room and low temperature.

The fluorescence lifetimes obtained for the C 71 strain (0.65 ns at 20C; 0.85 ns at 77 K) and for the B850 complex (1 ns at 20C; 1.3 ns at 77 K) indicate that the non‐radiative deactivation pathways, in the antenna, remain important in the absence of the reaction centers even at low temperature. We suggest that these data arise from the presence of special antenna molecules which act as intrinsic quenchers of the B875 antenna fluorescence. Between room and low temperature, the fluorescence yield and lifetime of the wild type are found roughly constant. This result suggests that the energy trapping by the reaction centers is independent of the temperature. The mechanism governing the energy transfer from the antenna to the reaction centers may differ from the mechanism leading to the energy transfer within the antenna. We suggest that a partially irreversible trapping of the excitation energy, on its way to the reaction center, takes place in the vicinity of the reaction center.
CIRCADIAN RHYTHM OF LOCOMOTOR BEHAVIOR IN A POPULATION OF Paramecium multimicronucleatum: ITS CHARACTERISTICS AS DERIVED FROM CIRCADIAN CHANGES IN THE SWIMMING SPEEDS AND THE FREQUENCIES OF AVOIDING RESPONSE AMONG INDIVIDUAL CELLS
Authors: Hasegawa Kenji , Tanakadate Akihiro
Published: January 2008

Abstract The locomotor behavior of Paramecium is determined by two components: swimming speed and the frequency of avoiding responses. The circadian oscillations of these two components were examined in order to interpret characteristics of the circadian locomotor rhythm, previously found in a Paramecium population using an originally defined parameter, “traverse frequency” (Hasegawa et al., 1978, 1982). In our present study, a modified version of the previously developed, fully computerized, close‐up video/photoamplifier system was used. Results indicate that individual specimens swam fast and unidirectionally during the day, while at night, in a light–dark cycle, they swam slowly and frequently turned. This oscillatory pattern was sustained in continuous darkness, where fluctuation in the frequency of avoiding responses was a dominant characteristic. The time structure of the “random walk” of Paramecium behavior was also examined by constructing and stochastically testing histograms of the interval times between specimens consecutively traversing beneath an observation point. Statistical analyses of observation data indicated that the circadian organization of the two components by individual specimens resulted in a circadian accumulation/dispersal rhythm of the entire population. It was concluded that the circadian “traverse frequency” rhythm principally represented this circadian accumulation/dispersal rhythm.
POLARIZED ABSORPTION SPECTRA OF MONOCRYSTALLINE ALL‐trans. AND 11‐cis., 12‐s‐cis. RETINAL AT 4.2 K
Authors: Drikos G. , Morys P. , Rüppel H.
Published: January 2008

Abstract Polarized absorption spectra of very thin crystal platelets of all‐trans. retinal and both forms of 11‐cis., 12‐s‐cis. retinal were measured at liquid Helium temperature. Even at 4.2 K the spectra remain vibronically unresolved. They show, however, a distinct shoulder at 23.9 kK for all‐trans. and at 22.7 kK for 11‐cis., 12‐s‐cis. retinal on the low energy side of the main band. An assignment of this transition to the lowest‐lying ππ*‐state 1Ag‐* is proposed.
PHOTOTOXIC POTENTIALITIES OF TARTRAZINE: SCREENING TESTS
Authors: Merville M. P. , Decuyper J. , Lopez M. , Piette J. , Van De Vorst A.
Published: January 2008

Abstract Tartrazine (TRT) a cosmetics, food and drug additive, was tested with respect to phototoxic potentialities. Although, using the cholesterol technique, TRT did not appear to produce any 1O2 upon visible light irradiation, the EPR spin trapping experiments with 5,5‐dimethyl‐1‐pyrroline‐N‐oxide, as spin trap, were in favour of activated oxygen species (O2˙, OH˙) and hydrated electron production by photoexcited TRT.

Irradiation of TRT with complementary biological systems (nucleic acids, bacteria, biological membranes) showed that few of them can be damaged by this photosensitizer. Tartrazine could induce a weak deoxyribose degradation but did not produce any DNA strand breaks on isolated φXRFI DNA. Tartrazine was detected as mutagen in the Salmonella microsome (Ames) assay, only in conjunction with visible light. In the presence of photoexcited TRT, erythrocyte membranes were damaged by covalently cross‐linking proteins.

The tests developed here seem thus to be suitable for detecting any unwanted phototoxic activity associated with potential photosensitizers.