bluuebunny/crossref_metadata_2025 huggingface dataset:
TRANS‐MEMBRANE LOCALIZATION OF REACTION CENTER PROTEINS IN RHODOPSEUDOMONAS SPHAEROIDES CHROMATOPHORES
Authors: Hall Robert L. , Doorley Peter F. , Niederman Robert A.
Published: January 2008

Abstract— Rhodopseudomonas sphaeroides NCIB 8253 chromatophores were treated with trypsin and pronase to determine which of the three reaction center subunits was exposed at the outer surface and susceptible to digestion. Trypsin (37°C, 60min) produced no detectable digestion of any subunit, based on SDS polyacrylamide gel electrophoresis analysis. Pronase (37°C, 60min) digested the H (28 kdalton) subunit but left the M (22 kdalton) and L (19 kdalton) subunits intact. We conclude that the H subunit is significantly exposed at the outer chromatophore surface but that the M and L subunits are probably not externally exposed. Chromatophores which had been pronase‐treated were fully photochemically active, as measured by light‐induced carotenoid bandshift at 522 nm. The H subunit is apparently unnecessary for primary photochemistry in situ.
MODELS RELATING ULTRAVIOLET LIGHT AND NON‐MELANOMA SKIN CANCER INCIDENCE*
Authors: Green Alex E. S. , Hedinger Robert A.
Published: January 2008

Abstract— The literature relating ultraviolet (UV) light to skin cancer (SC) has developed very rapidly recently. In this work we review and intercompare the various approaches of dose‐response relationships for nonmelanoma skin cancer. After defining a number of options for specifying dose, we describe several statistical epidemiological analyses. Then we discuss a number of models obtained by the inductive method. Finally, we illustrate the application of the mathematical machinery of Reliability Theory to this problem. We note that methodologies which have been used for the UV‐SC problem might also find application to broader environmental dose‐response problems.
EFFECTS OF CYCLOHEXIMIDE ON LIQUID‐HOLDING RECOVERY FROM ULTRAVIOLET RADIATION DAMAGE IN YEAST CELLS
Authors: Johnson R. G. , Morrison H. G. , Dawson P. C.
Published: January 2008

Abstract. The role of protein synthesis in liquid‐holding recovery from ultra‐violet radiation damage in synchronized Saccharomyces cerevisiae cells has been studied using cycloheximide as a specific inhibitor of cytoplasmic protein synthesis. Liquid‐holding recovery from UV‐induced budding delay is completed within a few hours and is not inhibited by the presence of cycloheximide. Liquid‐holding recovery from lethal UV damage is unaffected by cycloheximide for liquid‐holding times less than about 12 h. For longer times recovery is inhibited, with survival enhancement eliminated after about 48 h. Periods greater than 48 h of liquid‐holding in the presence of cycloheximide result in survival less than that obtained with immediate plating, but the same concentration of cycloheximide is not toxic to unirradiated cells.
ENERGY TRANSFER AND ENERGY LOSSES IN BILAYER MEMBRANE VESICLES (LIPOSOMES)
Authors: Mehreteab Ammanuel , Strauss George
Published: January 2008

Abstract. The efficiency of singlet‐singlet energy transfer was studied in bilayer lipid membrane vesicles (liposomes) for the following donor‐acceptor systems: (1) p‐terphenyl (TP) and diphenyloctatetraene (DPO); (2) DPO and chlorophyll a (Chl a); and (3) β‐carotene and Chl a. The energy transfer efficiency φDA was measured by sensitized fluorescence of the acceptor. Fractional quenching of the donor φQ was found from the donor fluorescence in absence and presence of the acceptor. For TP‐DPO and for DPO‐Chl a, the transfer efficiency increased with increasing acceptor concentration but was essentially independent of the donor concentration. No energy transfer from β‐carotene to Chl a could be detected. In liposomes, φDA differed only slightly from φQ at all donor and acceptor concentrations, thus demonstrating the absence of any appreciable energy losses. For solutions of the same donor‐acceptor pairs in cyclohexane φQ was considerably larger than φDA. The difference represents energy lost, principally by internal conversion, due to collisional quenching. The principal function of the lipid membrane appears to be the suppression of such losses. In addition, the rate of energy transfer in lipid membranes is about double that in solutions (at the same intermolecular distance) due to more favorable orientation.
LOCAL ELECTRIC FIELD EFFECT ON THE CHLOROPHYLL FLUORESCENCE
Authors: Frackowiak D.
Published: January 2008

Abstract. Polarized absorption and fluorescence of chlorophyll a and bacteriochlorophyll solutions in nematic liquid crystal mixtures have been studied in the presence of an external electric field.

The electric field caused a reorientation of the pigment molecules as concluded from changes in the polarized absorption. However, no correlation was found between the change in the polarized absorption and the change in the polarized fluorescence as a function of the field strength. The field influence was much stronger than expected only from the molecular orientation. The fluorescence polarized parallel to the direction of the liquid crystal was found to increase, whereas the similarly polarized absorption decreases. As a whole, the fluorescence yield significantly increased. It is suggested that the additional electric field is reinforced by a local field, most probably due to a protonation of the liquid crystal molecules.

Charged solvent molecules are reoriented in an external electric field which changes the local electric field acting on chlorophylls. Similar changes in CHI fluorescence yield due to local electric field can be created in vivo by the shift of charged molecules present in surrounding pigments. Such effects can be at least partially responsible for slow induction of fluorescence phenomena.
PHOSPHORESCENCE QUENCHING OF POLY rA IN GLUCOSE‐SODIUM ACETATE SOLUTION AT 77 K*
Authors: Nostrand F. Van , Pearlstein R. M.
Published: January 2008

Abstract. The phosphorescence of poly rA at 77 K in an aqueous medium containing glucose is half‐quenched by bound ethidium bromide at a fractional concentration, r1/2, of 0.005, and by bound proflavine at r1/2= 0.002: r1/2= 0.024 for Co2+ and r1/2= 0.039 for Mn2+. The decay of the dye‐quenched poly rA phosphorescence is markedly nonexponential and decays more rapidly with increasing dye concentration, while the decay of the metal‐ion quenched poly rA phosphorescence parallels that of the unquenched poly rA, independent of metal‐ion concentration. Förster overlap integrals and critical distances for transfer of both poly rA singlet and triplet excitation to dye singlet states are calculated, and used to explain a consistent interpretation of the experimental results in terms of one‐step direct excitation transfer from base to dye or metal ion in a highly folded polymer conformation.
3‐(α,α‐DIMETHYLALLYL)‐PSORALEN: A LINEAR FUROCOUMARIN FORMING MAINLY 4‘,5’‐MONOFUNCTIONAL ADDUCTS WITH DNA
Authors: Vedaldi D. , Dall'acqua F. , Caffieri S. , Rodighiero G.
Published: January 2008

Abstract— 3‐(α,αdimethylallyl)‐psoralen, a furocoumarin derivative recently isolated from Hortia arborea. has been studied with regard to its photoreacting (365 nm) capacity with native DNA. This compound photobinds to DNA to a much lower extent than psoralen, forming mainly 4.5′‐monofunc‐tional adducts, due to the presence in the 3‐position of α.α‐dimethylallyl group. which exerts a considerable hindrance both for the formation of a molecular complex with native DNA and for the photoreaction of the3,4‐double bond. This site of the molecule photoreacts, and, only 2.5% of the bound substance forms cross‐linkages. Therefore. 3‐(α,α‐dimethylallyl).psoralen behaves as a fairly pure mono‐functional reagent.
PENETRATION OF UV‐B AND BIOLOGICALLY EFFECTIVE DOSE‐RATES IN NATURAL WATERS*
Authors: Smith Raymond C. , Baker Karen S.
Published: January 2008

Abstract— Spectral irradiance measurements. from 310 to 650 nm. have been made in low and modcrately productive ocean waters. These new data and selected earlier clear ocean water data are used as a basis for extrapolating the diffuse attenuation coefficient for irradiance into the 280 nm region. This allows a quantitative calculation of the penetration of UV‐B (280–340 nm) and of biologically (DNA) effective dose‐rates as a function of depth into various ocean water types. The model of Green et al. (1974a) for various atmospheric ozone thicknesses has been used to obtain input surface irrddiancc for this calculation. Our purpose is to provide a basis for estimating the penetration of possible increased UV‐B into natural waters due to possible changes in the ozone concentration of the stratosphere. Given appropriate biological data, this method allows a quantitative evaluation of radiation effects on aquatic organisms as a function of depth. As a specific example, our results have been graphically compared with the dosage‐response results on anchovy larvae obtained by Hunter et al. (1978).
EFFECT OF ULTRAVIOLET IRRADIATION ON EGGS AND LARVAE OF THE NORTHERN ANCHOVY, ENGRAULIS MORDAX, AND THE PACIFIC MACKEREL, SCOMBER JAPONlCUS, DURING THE EMBRYONIC STAGE*
Authors: Hunter John R. , Taylor John H. , Moser H. Geoffrey
Published: January 2008

Abstract— Anchovy and mackerel eggs and yolk‐sac larvae were exposed to UV radiation in the bioactive band of wavelengths between 280 and 320 nm. the UV‐B region of the spectrum. Irradiation levels were based upon predicted UV‐B increases that would result from anthropogenic diminution of Earth's protective ozone shell. Dose‐response relationships for mortality and histological and morphological effects were determined for two different spectral energy compositions, using FS‐40 sunlamps and two filter combinations. Anchovy were more sensitive than mackerel to UV‐B. Data for anchovy were analyzed in terms of DNA‐effective doses, i.e. the integrated spectral thence (in J/m2/nm) with the energy at each nm weighted by its effectiveness relative to the Setlow generalized DNA action spectrum. Fifty per cent of anchovy survived a cumulative DNA effective dose of 1150J'm‐2 over a 4‐day period. In the surviving larvae. irradiation induced lesions in the brain and eye. caused marked dispersion of pigment within melanophores and retarded growth and development. At the lowest dosage used. 760 (J. m‐2)DNA, growth was retarded and brain lesions occurred in anchovy. Calculations of Smith and Baker (in this issue) indicate that in clear ocean water a significant incidence of lesions and retardation of growth in anchovy could occur at the surface at a 25%, reduction in ozone and down to 3.5 m at a 50% reduction. Eggs and larvae of anchovy occur at these depths.
SQUID HYPSORHODOPSIN
Authors: Shichida Yoshinori , Tokunaga Fumio , Yoshizawa Tóru
Published: January 2008

Abstract— Squid hypsorhodopsin is produced by irradiating rhodopsin or isorhodopsin with yellow light (>480nm) at liquid He temperature (4K). Compared with cattle rhodopsin, squid rhodopsin easily converts to a photosteady state mixture composed of rhodopsin, isorhodopsin, hypsorhodopsin and bathorhodopsin at this temperature and the amount of hypsorhodopsin in the mixture is high. Hypsorhodopsin has a main absorption peak at 446 nm, and its extinction coefficient is 1.16 times larger than that of rhodopsin. On warming above 35 K, squid hypsorhodopsin converts to bathorhodopsin. A kinetic analysis indicates that the hypsorhodopsin can be formed not only from rhodopsin but also from isorhodopsin. On absorption of light. both squid bathorhodopsin and hypsorhodopsin convert to a mixture of rhodopsin and isorhodopsin.
PROPERTIES OF CHLOROPH'YLL‐LECITHIN VESICLES: ULTRACENTRIFUGATION, ABSORBANCE, EMISSION AND PHOTOBLEACHING
Authors: Dijkmans H. , Leblanc R. M. , Cogniaux F. , Aghion J.
Published: January 2008

Abstract— Egg lecithin vesicles (liposomes) containing up to one Chl a per 11 lecithin molecules were prepared without sonication. Their absorbance and emission properties indicate that Chl is dispersed in the lecithin, that the vesicles are dispersed in the medium and that there is a strong quenching of fluorescence.

Their photobleaching and chemical bleaching show that there is a negligible amount of colloidal Chl present. In vesicles with a Chl:lecithin molar ratio higher than 0.05, there are probably some small aggregates of Chl a in the bilayer.

The ultracentrifugation of such vesicles shows that their sedimentation constant increases, though not regularly, with their relative Chl content
LETHAL INTERACTION BETWEEN ULTRAVIOLET‐VIOLET RADIATIONS AND METHYL METHANE SULPHONATE IN REPAIR PROFICIENT AND REPAIR DEFICIENT STRAINS OF ESCHERICHIA COLI
Authors: Correia Ivanosca S. , Tyrrell Rex M.
Published: January 2008

Abstract— The lethal interaction between monochromatic radiation at various wavelengths and methyl methane sulphonate was tested in strains of Escherichia coli proficient and deficient in DNA repair. In the repair proficient wild‐type strain K12 AB1157, the efficiency of sensitization to MMS as a function of dose (at 334 nm, 365 nm and 405 nm) was found to be directly correlated with the dose necessary to remove the shoulder from the survival curve at the wavelength employed. The 365 nm: MMS interaction was also observed in other repair proficient E. coli strains (W3110 and B/r) but was absent in a recA and a polA strain. Pre‐treatment of AB1157 with MMS leads to a much larger interaction than pre‐irradiation with 365 nm. It is concluded that dose‐dependent damage to DNA repair by the near‐UV radiation is involved in the interaction and possibly that MMS causes irreversible damage 10 repair enzymes.
EVIDENCE FOR DARK REPAIR OF FAR ULTRAVIOLET LIGHT DAMAGE IN THE BLUE‐GREEN ALGA, GLOEOCAPSA ALPICOLA
Authors: Williams Edwin , Lambert Joan , O'Brien Philip , Houghton James A.
Published: January 2008

Abstract— The inactivating effect of far UV light on the unicellular blue‐green alga Gloeocapsa alpicola could be totally reversed by exposure to blue light immediately after irradiation. However, if the irradiated cells were held in the dark before exposure to blue light, reversal became progressively less efficient and almost disappeared after 60–80 h holding. Caffeine and acriflavine inhibited loss of photoreversibility, suggesting an involvement of excision functions. Chloramphenicol and rifampicin slightly increased the rate of loss of photoreversibility, indicating that inducible functions play only a minor role. Split UV dose experiments indicated that light‐dependent repair remained operational during dark liquid holding. These results provide preliminary evidence for dark repair in G. alpicola.
A COMPARISON OF IN VIVO AND IN VITRO TESTING OF SUNSCREENING FORMULAS
Authors: Sayre Robert M. , Agin Patricia Poh , LeVee Gordon J. , Marlowe Edward
Published: January 2008

Abstract— Seven commercially available sunscreens were compared by three different methods. Absorbance spectra were measured for each product in isopropanol solution and also on hairless mouse epidermis. In vivo tests were performed on human volunteers using a Xe arc solar simulator. Sun Protection Factors (SPF) were calculated by each method for each product tested and the results compared. By all methods used, the combination of 7% octyl dimethyl para‐aminobenzoic acid and 3% oxybenzone provided the most protection from U.V. light. While estimates of the effectiveness of all products were much too high when calculated by the isopropanol solution method, the hairless mouse epidermis technique seems to be an accurate tool for predicting product efficacy in vivo.
A SEARCH FOR LUMINESCENT FREE RADICAL RECOMBINATION
Authors: Abuin Elsa , Lissi Eduardo
Published: January 2008

Abstract— Radical recombinations producing a single bond are potentially chemiluminescent reactions. The probability that a radical recombination leads to an excited state will depend on the relative shape of the ground and excited surfaces. This information can be obtained from the rate constants of the ground state and excited states dissociation, and the energy differences between the states. From the available data it was concluded that acyl radicals are among the most promising radicals regarding the probability of recombination leading to excited triplet states. Experimental efforts to detect luminescence following the recombination of acyl radicals will be discussed.
THE TRANSFORMATION OF PHYTOCHROME TO ITS PHYSIOLOGICALLY ACTIVE FORM
Authors: Song Pill‐Soon , Chae Quae
Published: January 2008

Abstract— The phototransformation of phytochrome (Pr) to its physiologically active form (Pfr) can be best described by a tautomeric proton shift in ring A without a substantial con formational change of the chromophore. The electronic aspect of this transformation is discussed.
DYE‐SENSITIZED PHOTOOXIDATION OF 1,4‐POLYDIENES
Authors: Rabek Jan F. , Ranby Bengt
Published: January 2008

Abstract— The reaction of singlet oxygen with polydiene polymers produces hydroperoxides by the typical ‘ene’ type reaction. The observed chain scission process cannot be explained by the photodecom‐position of hydroperoxide formed by visible light, because these hydroperoxides do not absorb light in this repion. Spectroscopic and EPR studies of the dye‐solvent systems show the formation of reactive free radicals. which are probably responsible for the abstraction of hydrogen from the polymer molecules. The next step is the well known free radical oxidation mechanism which is responsible for the chain scission reactions.
PEROXIDASE MEDIATED CHEMILUMINESCENCE WITH PHENOL DERIVATIVES. PHYSICO‐CHEMICAL PARAMETERS AND USES IN BIOLOGICAL ASSAYS
Authors: Halmann M. , Velan B. , Sery T. , Schupper H.
Published: January 2008

Abstract— The influence of pH and concentration of reagents on the chemiluminescence emitted during peroxidase mediated oxidation of phenol derivatives was studied. Maximal light emission was determined under conditions where chemiluminescence due to auto‐oxidation was negligible. With phloroglucinol and purpurogallin as substrates, a direct proportionality was obtained between the concentration of peroxidase and the maximal light emission. p‐Phenylenediamine enhances 8‐fold the light emitted with purpurogallin. With resorcinol as substrate the relation between concentration of enzyme and maximal light emission gives an S‐shaped curve. With pyrogallol the light emitted is proportional to the square of the concentration of peroxidase.
PHOTON COUNTING SPECTRAL ANALYZING SYSTEM OF EXTRA‐WEAK CHEMI‐ AND BIOLUMINESCENCE FOR BIOCHEMICAL APPLICATIONS
Authors: Inaba Humio , Shimizu Yoshiaki , Tsuji Yasuhiro , Yamacishi Akio
Published: January 2008

Abstract— The systematic study of the method for measuring the spectral distribution of extra‐weak light signals, such as from biochemical systems and living tissues involving chemi‐ and bio‐energized processes, led to the design and construction of a new type of spectrometer, called the filter spectral analyzer system, incorporated with the high‐sensitivity photon counting technique. Experimental tests to examine the operational characteristics of this filter spectral analyzer system and comparisons of the signal‐to‐noise ratio with a conventional grating spectrometer were made by accomplishing the spectral analysis of low‐level light sources. The measurement of the spectra of very weak chemilumines‐cence accompanying various kinds of chemical and biological processes, including autoxidation and enzymatic reaction were performed successfully.
PASSIVE AND ACTIVE ROLE OF FLUORESCERS IN THE CHEMILUMINESCENCE OF TETRAMETHOXYDIOXETANE
Authors: Wilson Thérèse
Published: January 2008

Abstract— Tests for the possible catalytic role of fluorescers in the chemiluminescent decomposition of dioxetanes are discussed and applied to the case of tetramethoxydioxetane. This dioxetane, which can undergo direct thermal decomposition yielding excited methyl carbonate with subsequent excitation of fluorescers (for example 9, 10‐dibromoanthracene. DBA), is shown to be sensitive also to catalysis by fluorescers such as rubrene. 9, 10‐diphenyl‐anthracene (DPA) and 9, IOdicyanoanthracene (DCNA). The possibility of a charge‐transfer mechanism of chemiluminescent catalysis is suggested.
OXIDATION OF ACETONE UNDER BAEYER‐VILLIGER CONDITIONS: EVIDENCE FOR FORMATION OF ACETONE CARBONYL OXIDE OR ITS ISOMERIC DIOXIRANE
Authors: Murray Robert W. , Ramachandran V.
Published: January 2008

Abstract— Oxidation of acetone under Baeyer‐Villager conditions produces a new species which is capable of epoxidizing olefins. It is suggested that this intermediate is acetone carbonyl oxide or its isomer dimethyldioxirane.
DARK EXCITATION OF CHLOROPHYLL
Authors: Augusto Ohara , Cilento Giuseppe
Published: January 2008

Abstract— Enzyme generated triplet acetone transfers its energy to Chl a to form the first excited singlet of the acceptor, as shown by the suppression of the acetone chemiphosphorescence and concomitant appearance of the Chl fluorescence.
KINETICS OF TRIPLET OXIDATION OF METALLO‐PORPHYRIN COMPOUNDS TO THEIR CORRESPONDING RADICAL CATIONS
Authors: Potter W. , Levin G.
Published: January 2008

Abstract— The kinetics of photooxidation of triplets of metalloporphyrin compounds to their corresponding radical cations was investigated. Zn‐tetraphenyl porphyrin (ZnTPP) and Mg‐tetraphenylpor‐phyrin (MgTPP) triplets were oxidized by europium salt with rate constants of 4.8 × 105M‐1s‐1 and 2.1 × 106M‐1s‐1, respectively. The high rate constant of oxidation of MgTPP triplet might be related to the ground state oxidation potential, being 0.54 V (SCE) for the Mg complex and 0.71 (SCE) for the Zn complex.

The rate constant of oxidation of ZnTPP excited singlet is in the order of diffusion control, i.e. ˜ 1010M ‐1 s‐1. Excitation of ferric, cupric, cobaltic, and vanadyl tetraphenylporphyrin did not result in a long‐lived triplet state that would allow oxidation studies using flash photolysis.
ANOMALOUS DOSE‐RESPONSE CHARACTERISTICS INDUCED BY CAFFEINE IN ULTRAVIOLET‐IRRADIATED V79–79 CHINESE HAMSTER CELLS
Authors: Schroy Carter B. , Todd Paul
Published: January 2008

Abstract— Cultured Chinese hamster cell line V79–79 exhibits an increase in survival with increasing UV fluence after a sharp decrease when exposed to 2.5 mM caffeine for 44 h after far‐UV irradiation resulting in an anomalous maximum in the survival curve. No survival maximum is evident when either 0 or 1 mM caffeine is administered under the same conditions. The UV survival curve for 2.5 mM caffeine crosses the corresponding 1 mM curve and apparently becomes asymptotic to the OmM curve as UV fluence is increased. Chinese hamster cell lines V79–753B (related to V79–79 by derivation from the same parental line) and M3–1F3 (unrelated) exhibit only potentiation of post‐UV lethality by the same concentration of caffeine and have no caffeine‐induced anomalies in their survival curves. Xanthine. used alone or in combination with caffeine, only potentiated a slight amount of lethality and appears not to be a major causative factor of the anomaly.
TRYPTOPHAN FLUORESCENCE LIFETIMES AS A FUNCTION OF EXCITATION WAVELENGTH*
Authors: Alpert Bernard , Jameson David M. , Lopez‐Delgado Ricardo , Schooley Ralph
Published: January 2008

Abstract— –Fluorescence decay times of aqueous dilute solutions (˜20 µM) of L‐tryptophan have been determined using the phase shift technique as well as single photon‐counting coupled with synchrotron radiation (ACO at Orsay and SPEAR at Stanford). Decay times were obtained as a function of the excitation wavelength (in the spectral region 220–320 nm) monitoring emission of λ> 320 nm (in certain specified cases, λ> 360 nm). We have found that, at neutral pH and 20°C. fluorescence decays are single exponentials and independent of the excitation wavelength; under these conditions we find τ= 3.1 ± 0.1 ns.
SPECTROSCOPIC PROPERTIES OF PSORALEN DERIVATIVES SUBSTITUTED BY CARBETHOXY GROUPS AT THE 3,4 AND/OR 4,5' REACTION SITE
Authors: Vigny P. , Gaboriau F. , Duquesne M. , Bisagni E. , Averbeck D.
Published: January 2008

Abstract— The newly synthesized linear psoralen derivative 3‐carbethoxypsoralen has been shown recently to behave as a monofunctional derivative and has attracted some interest in the psoriasis treatment. In a first attempt to understand, by the fluorescence technique, the molecular mechanism by which it interacts with DNA, a spectroscopic study of the molecule was undertaken. The fluorescence of 3‐carbethoxypsoralen at room temperature resembles that of 8‐methoxypsoralen with a ten times higher quantum yield. 365 nm irradiation of dilute solutions of 3‐carbethoxypsoralen rapidly leads to the formation of two types of highly fluorescent photoproducts. Type 1 photoproducts (λemmax= 425 nm, λexcmax= 360 nm) have been identified as the result of the addition of a solvent molecule to the 4,5' reaction site of the molecule. Their fluorescence intensity is a hundred times higher for 3‐carbethoxypsoralen than for 8‐methoxypsoralen. They become negligible when the 4',5' reaction site carries also a carbethoxy group. Type 2 photoproducts exhibit a somewhat different emission (λemmax = 443 nm, λexcmax= 413 nm). They are probably the result of an opening of the furocoumarin molecule. The implications of the peculiar photochemical properties of 3‐carbethoxypsoralen are discussed in view of its biological activity. In addition, the use of fluorescence in monitoring the photobinding of psoralens to DNA is also discussed
THE EFFECT OF CHANGES IN CELL GEOMETRY ON THE SENSITIVITY TO ULTRAVIOLET RADIATION OF MAMMALIAN CELLULAR CAPACITY
Authors: Coohill Thomas P. , Knauer Daniel J. , Fry Dennis G.
Published: January 2008

Abstract— We have measured a calcium and magnesium dependent change in cell shape when mammalian cell monolayers are being prepared for irradiation by replacing their growth medium with certain buffers. In some cases, flattened cells (umbonate) assumed a spherical configuration. In order to assume a centrally located target molecule, we used a DNA‐dependent cellular function–pacity for herpes viral growth–as the parameter to measure ultraviolet (UV) sensitivity of cells irradiated while in either of the two shapes. Umbonate cells were more sensitive to UV than were spherical cells. Exposures to the cell that lowered the cellular capacity of umbonate cells to the 10% survival level only lowered spherical cells to the 50% level. Twenty‐seven per cent additional UV exposure to spherical cells was required to get the same effect as with umbonate cells. Included in the text are photographs of both cell types, survival curves for cellular capacity, a measure of the absorbance of cell homogenates, and a calculation of the relative number of photons absorbed by each cell nucleus.
THE CONTROL BY PHYTOCHROME OF NITRATE REDUCTASE IN THE CURD OF LIGHT‐GROWN CAULIFLOWER
Authors: Whitelam G. C. , Johnson C. B. , Smith H.
Published: January 2008

Abstract— The activity of nitrate reductase from the curd of light‐grown cauliflower (Brassica oleracea (L) var botrytis (DC) ‘St. Hilary’) is modulated by nitrate and by light. Using broad‐band sources of equal photosynthetically active radiation but with different proportions of red and far‐red light, a linear relationship between nitrate reductase activity and ψ(Estimated phytochrome photoequilibrium) was obtained. This relationship, apparent after 8 h incubation, was maintained and little altered after 48 h incubation. The linearity was apparent between ψE 0.26 and ψE 0.69; ψE 0.26 being no more effective than a dark control. Far‐red reversibility confirmed the involvement of phytochrome. Brief pulses of red light were also used to establish a range of phytochrome photoequilibria within the tissue. Again a linear relationship between ψ and nitrate reductase activity was obtained with a threshold for the response at ψ 0.3. With both monochromatic and broad‐band sources it was seen that neither photon fluence rate nor duration of exposure affected the final activity of the enzyme and that phytochrome was acting solely through ψ (or [Pfr] since phytochrome is stable in this tissue) to bring about these responses.
SOME FUROCOUMARINS AND ANALOGS: COMPARISON OF TRIPLET PROPERTIES IN SOLUTION WITH PHOTOBIOLOGICAL ACTIVITIES IN YEAST
Authors: Melo M. T. Sa E , Averbeck D. , Bensasson R. V. , Land E. J. , Salet C.
Published: January 2008

Abstract— Some photophysical and photochemical properties of two furocoumarins, three furochro‐menes and one difurobenzene have been studied in ethanol by laser flash spectroscopy. Such properties included the triplet absorption spectra. extinction coefficients, quantum yields of formation and reactivities with the nucleic acid bases thymine and uracil, and the amino acid tryptophan. The effects the same compounds have on survival of the yeast, Saccharomyces cerevisiae, after 365 nm photosensitization were also investigated. These effects on survival differed markedly for the different compounds. Possible correlations between the photophysical, photochemical and photobiological data are discussed.
THE ASSOCIATION OF THE 5‐METHYLPHENAZINIUM CATION AND THE 5‐METHYL‐10‐HYDRO‐PHENAZINIUM RADICAL CATION WITH MICELLES*
Authors: Evans C. Anderson , Bolton Jms R.
Published: January 2008

Abstract— 5‐Methylphenazinium (MP+) cation salts are known to stimulate photophosphorylation in photosynthetic systems. The mechanism is thought to involve the translocation of protons across the thylakoid membrane although few details are known concerning the mechanism and the identity of the proton carrier. As there is some indication that the semireduced species, the 5‐methyl‐10‐hydro‐phenazinium (MPH+) cation radical, may be the proton carrier, we have studied the interaction of MPH+ with micelles as a model system for aqueouslipid interactions in a membrane. In this study we have used the techniques of NMR and EPR.

In the presence of sodium dodecyl sulfate (NaLS) micelles the EPR spectrum of MPH + is broadened indicating specific binding of MPH+ to the micelle. A binding constant of ‐105M‐1 was obtained. The 220 MHz NMR spectrum of a micellar solution with added MPH! shows specific broadening of the alkyl protons. The use of model paramagnetic adducts has allowed us to infer from the NMR results that the MPH+ ion penetrates the hydrocarbon part of the micelle to a considerable extent. This would indicate to us that MPH+ can indeed function as a proton carrier as it should be able to penetrate deeply into the lipid layer of the membrane.

From these results, we conclude that:

Both MP+ and MPH+ interact strongly with NaLS micelles. MPH+ interacts more weakly with neutral Triton X‐100 micelles while in this case, no evidence of interaction is seen for MP+. No binding of either MP+ or MPH+ is observed with cationic micelles from CTAB.

MP+ is adsorbed to NaLS micelles in a very hydrophilic region, probably In the Stern layer. MPH+, however, is much less hydrophilic than MP+ and appears to reside in the Palisade layer a few angstroms below the head groups.

On the basis of these results, we make the following proposals:

MPH+ is sufficiently hydrophobic to be a candidate for the reduced MP+ species which actually carries the proton across the thylakoid membrane.

The site at which MP+ is reduced by X must be anionic in nature in order for MP+ to be bound strongly.
THE PHOTOREDUCTION OF FLAVINS BY AMINO ACIDS AND EDTA. A CONTINUOUS AND FLASH PHOTOLYSIS STUDY
Authors: Heelis P. F. , Parsons B. J. , Phillips G. O. , McKellar J. F.
Published: January 2008

Abstract— Primary and secondary photochemical processes in oxygen‐free aqueous solution have been characterised for FMN alone and in the presence of EDTA and four amino acids using nanosecond and microsecond flash photolysis and continuous photolysis techniques. The relative contributions of oneelectron and two‐electron (group or hydride transfer) reactions to the deactivation of the triplet has been determined by comparing the radical concentration (560 nm) with the bleaching of the ground state (446 nm). It was concluded that one‐electron reactions (hydrogen atom or electron abstraction) are the major mode of reactivity of the flavin triplet state with all the suhstrates studied.

The nature of the reactions of the flavin semiquinone radical have been studied quantitatively by microsecond flash photolysis. These secondary reactions consist of either a ‘back reaction’ between the flavin and substrate radicals (tryptophan or glycyl‐tyrosine) or the transfer of a second electron (or hydrogen atom) from the substrate radical to the flavin radical (EDTA, methionine and possibly cysteine) to form reduced flavin and oxidised substrate. From a comparison of the quantum yields of formation of reduced flavin using ‘flash’ and continuous irradiation, an additional pathway for the decay of the flavin radical is suggested to occur at low light intensities in the presence of glycyl‐tyrosine or histidine.
EFFECTS OF ENVIRONMENTAL LIGHTING AND DIETARY VITAMIN A ON THE VULNERABILITY OF THE RETINA TO LIGHT DAMAGE*
Authors: Noell Werner K.
Published: January 2008

Abstract—The damaging effect of visible light on photoreceptors and pigment epithelium has been studied mainly in the albino rat with continuous or intermittent exposures to green light for up to several days. Similar damage as in the albino rat but with different doses of light and different times of exposures were observed in pigmented rats, hamster strains, mouse strains and in the nocturnal monkey. The damage is graded histologically mainly by the size of the area of the retina over which the photoreceptors have died. The damage is quantitatively assessed by the measurement of ERG and DNA content of the retina. The action spectrum for the irreversible damage agress with the absorption curve for rhodopsin. Threshold damage occurs with diffuse light that reduces acutely the rhodopsin of the whole retina by about 10%. Damage is a function of body and eye temperature during exposure. At a body temperature of 42°, 2–4 h of exposure produces the same damage as exposure for 30 h at normal temperature using 1500 lux. The damage is also very markedly dependent upon the light history of the animal prior to exposure. Cyclic environmental light of I to 10 ft‐cd for several days or weeks reduces very significantly the damaging effect compared to animals reared simultaneously in continuous darkness. Cyclic light rearing is associated with a reduction in opsin and rhodopsin of the whole retina, an increase in the molar phospholipid/opsin ratio and a reduction in the length of the outer segment. Protection is also produced by Vitamin A deficiency but significantly only when rhodopsin content is decreased by maintenance in very weak cyclic light. Thus Vitamin A deficiency and environmental light seem to use the same mechanism. Results do not support the possibility that damage is caused by a cytotoxic effect of retinol.
HORMONAL AND DIM LIGHT EFFECTS IN RETINAL PHOTODAMAGE*
Authors: O'Steen W. Keith
Published: January 2008

Abstract—Exposure of albino rats to continuous visible dim light results in the rapid. but graded. loss of photoreceptor cells. The age at which albino rats are exposed to light influences the degree of photoreceptor damage. The severity of cell destruction per unit exposure time gradually increases in rats exposed at different ages from postweaning to adulthood, and by 8 weeks of age, reduction in the thickness of the outer nuclear layer (photoreceptor cell nuclei) is highly significant. The period of increasing susceptibility to light damage is coincident with the occurrence of sexual maturation, which suggests a relationship between photoreceptor destruction and the maturation of the pituitary gland‐gonadal axis. To determine whether the absence of the pituitary gland and ovarian hormones influences photoreceptor damage, animals were either hypophysectomized or ovariectomized and exposed to continuous illumination for up to 45 days. The degree of photoreceptor destruction is significantly reduced in operated, as compared with sham‐operated control, rats exposed to an identical light regimen. Small, physiologic doses of estradiol reverse the protective effects of ovariectomy, but larger, pharmacologic doses do not. Retinal damage is significantly enhanced by injection of pituitary homogenates during the light‐exposure period and by transplantation of pituitary glands under the kidney capsule of rats in which the pituitary has been removed. Pituitary glands transplanted in this location produce high levels of prolactin, while other pituitary hormones are found at unusually low, and sometimes nonfunctional, levels. Prolactin administration to rats during the light exposure period effectively reverses the protection afforded by removal of the pituitary gland.

Pituitary gland hormones as well as hormones from some of the pituitary target organs, appear to have a regulatory influence on the severity of light‐induced photoreceptor damage in this species.
RATES OF REACTION OF SINGLET OXYGEN WITH SULFIDES
Authors: Monroe Bruce M.
Published: January 2008

Abstract—Reaction rate constants for the reaction of singlet oxygen with a series of 24 sulfides in chloroform have been measured by inhibition of the self‐sensitized photooxidation of rubrene. The reaction rate constant is sensitive to steric effects, decreasing as the carbons α‐ to sulfur become more highly substituted. Addition of a methyl group to each of the carbons α‐ to sulfur decreases the rate constant by about a factor of 10. From a series of p‐ and m‐substituted thioanisoles, a ρ of ‐1.67 ± 0.09 was found. A much better correlation was found with σ than with σ+ indicating there is no resonance interaction with the reaction center. Typical rate constants are: di‐n‐butyl sulfide, 2.3 × 107M‐1 s‐1; CBZ‐L‐methionine methyl ester, 1.4 × 107; di‐s‐butyl sulfide, 1.8 × 106; di‐t‐butyl sulfide, 1.3 × 105; and thioanisole, 2.3 × 106.
EFFECT OF PHOTOREACTIVATING LIGHT ON LETHAL AND PRE‐MUTATIONAL UV LESIONS IN ESCHERICHIA COLI WP2s CARRYING THE R46 MUTATOR PLASMID
Authors: Todd P. A. , Banfi E. , Eftimiadi C. , Monti‐Bragadin C.
Published: January 2008

Abstract—An excision‐deficient E. coli strain carrying the R46 mutator plasmid showed a different response towards photo‐reactivation after UV irradiation than the same strain without plasmid. While the photoreactivation of lethal lesions was comparable in both strains, the number of UV‐induced mutants per 106 survivors was slightly reduced for the plasmid bearing strain by photoreactivating light at UV fluences below 60 mJ/m2 but increased at higher fluences. To explain this it is proposed that some UV photoproduct(s) of DNA other than cyclobutane dipyrimidine dimers are pre‐mutational lesions for error‐prone DNA repair by the plasmid, P‐repair, but not for SOS‐repair.
HERPES VIRUS PRODUCTION IN MONKEY KIDNEY AND HUMAN SKIN CELLS TREATED WITH ANGELICIN OR 8‐METHOXYPSORALEN PLUS 365 nm LIGHT
Authors: Coppey J. , Averbeck D. , Moreno G.
Published: January 2008

Abstract—At an cquimolar concentration of 50 μM the bifunctional furocoumarin, 8‐methoxypsoralen (8‐MOP), is about 36 times more efficient in inhibiting the colony forming ability of CV‐I monkey kidney cells than the monofunctional furocoumarin angelicin. In contrast 8‐MOP is only 7.5 times more efficient than angelicin for the inhibition of herpes simplex virus (HSV) production in CV‐1 cells. This latter factor seems to reflect differences in photoreactivity of the two compounds with host cell DNA.

A substantial recovery of HSV production was seen when cells were infected at different time intervals after treatment with angelicin‐plus‐light, whereas recovery was very limited after 8‐MOP plus light treatment. The recovery process was slow as compared to that observed after UV (254 nm)‐irradiation.

The repair capacities of treated normal and xeroderma pigmentosum (group A) skin fibroblasts were estimated by measuring HSV production and unscheduled DNA synthesis. XP‐A cells repaired angelicin induced damage less efficiently than did normal cells. Neither cell type showed any repair activity after 8‐MOP plus light treatment.
PAIRWISE RECOMBINATION IN THE DECAY OF PHOTOCHEMICAL HYDRATED ELECTRONS*
Authors: Lee Joon Y. , Baugher J. F. , Grossweiner L. I.
Published: January 2008

Abstract— The decays of hydrated electrons generated by 265 nm laser flash photolysis of aqueous I‐, tyrosine, tryptophan, lysozyrne. and ribonuclease have been analyzed by numerical computing. Homogeneous reactions do not explain the data without e‐aq—radical back reactions significantly faster than diffusion limited. The results are explained by postulating pairwise recombination persists at times where conventional diffusion theory predicts randomization, particularly at low intensities and in the absence of effective e‐aq scavengers. The physical mechanisms responsible for these effects are considered.
CHEMICAL REACTION RATES OF AMINO ACIDS WITH SINGLET OXYGEN
Authors: Matheson I. B. C. , Lee John
Published: January 2008

Abstract— The chemical reactions of amino acids with singlet oxygen have been measured in D2O solution where the singlet oxygen was generated directly by irradiation of the oxygen 3∑g‐→1δg+ lv electronic transaction with the 1.06 μm output of an Nd‐Yag laser. Chemical reaction was measured as amino acid loss by an amino acid analyzer or by fluorescence in the cases of tryptophan and tyrosine.

The chemical rate constants, in units of 107M‐1s‐1, are histidine 10, tryptophan 3, methionine 1.7, tyrosine 0.8 and alanine 0.2, In the cases of histidine, methionine and alanine the interaction appears to be entirely chemical, i.e. there is no evidence for physical quenching in addition to the chemical reaction. The histidine chemical reaction rate constant shows an increase with pD with a pK of 6.9.
ISOLATION AND IDENTIFICATION OF TRYPTOPHAN PHOTOPRODUCTS FROM AQUEOUS SOLUTIONS OF TRYPTOPHAN EXPOSED TO NEAR‐UV LIGHT*
Authors: Sun Ming , Zigman Seymour
Published: January 2008

Abstract—One of the previously unidentified photoproducts isolated from the photolysate of aqueous tryptophan solutions was identified as 2‐carboxy‐3a‐hydroxy‐1,2,3,3a,8,8a‐hexahydropyrrolo(2,3b)‐indole by direct comparison with the authentic reference compound synthesized using the established procedure. This pyrroloindole alcohol has been shown to be the reduction product of the 3a‐hydroperoxy intermediate (structure 4 in Fig. 1) by Nakagawa et al. (1977). The isolation and identification of this derivative and the detection of the peroxy intermediate 3a‐hydroperoxypyrrolidinoindole (4). from irradiated aqueous tryptophan solutions suggests that the direct photooxidation of l‐tryptophan to fromylkynurenine may follow a pathway via a tricyclic intermediate instead of the energetically unfavorable dioxotane intermediate. This scheme is similar to the mechanistic model proposed by Nakagawa et al. (1977) for the rose bengal sensitized photooxidation of tryptophan.
THE FLUORESCENCE OF TRYPTOPHYL PEPTIDES
Authors: Werner T. C. , Forster Leslie S.
Published: January 2008

Abstract— Tryptophan lifetimes and relative quantum yields have been determined for a group of small (1–4 residues) peptides and peptide hormones [luteinizing releasing factor. mellitin, glucagon. glucagon 22–29, glucagon 1–26. glucagon 1–27 (homoserine)]. All of the larger peptides and most of the smaller peptide anions exhibit nonexponential decay. Peptide quenching in the small peptides is more effective when the bonding is at the amino rather than at the carboxyl end of tryptophan. With the exception of tryptophylglycine. quenching by NH+3 is thought not to involve proton transfer. The results suggest that a decay component of 3–4 ns is expected whenever large peptides and proteins contain a solvent exposed tryptophan.
FLUORESCENCE OF COMPLEXES OF QUINACRINE MUSTARD WITH DNA—II. DEPENDENCE ON THE STAINING CONDITIONS
Authors: Andreoni A. , Cova S. , Bottiroli G. , Prenna G.
Published: January 2008

Abstract—Measurements of time‐resolved fluorescence of Micrococcus lysodeikticus DNA stained with quinacrine mustard are presented in this paper. In particular, the dependence of the fluorescence decay law both on the degree of DNA saturation by the dye and on the ionic strength of the solutions is investigated. It is shown that the quinacrine mustard molecules intercalating the DNA base pairs exhibit two different fluorescence behaviors which make them either donors or acceptors in a Forster energy transfer mechanism. A mathematical formulation of this mechanism allows us to interpret all the experimental fluorescence decay curves. In addition, some new properties of the external binding mode are obtained.
VISIBLE LIGHT IRRADIATION OF HUMAN AND BOVINE SERUM ALBUMIN‐BILIRUBIN COMPLEX*
Authors: Rubaltelli Firmino F. , Jori Giulio
Published: January 2008

Abstract— The UV absorption and the fluorescence emission spectra of both bovine (BSA) and human (HSA) serum albumin underwent noticeable changes upon irradiation of their 1:1 complexes with bilirubin; both these phenomena are suggestive of the photosensitized modification of aromatic amino acid residues. Amino acid analysis showed that after relatively short irradiation times of both albumins, only histidyl and tryptophyl residues appeared to be affected to a significant extent. After 60min of irradiation, some decrease in the tyrosine content was also observed, especially for HSA.

Conformational studies, obtained by exposing unirradiated and irradiated BSA and HSA to denaturing agents, showed that the three‐dimensional organization of the 15 min irradiated samples was slightly different from that of the native proteins. On the other hand, after 15 min of irradiation, the association constant of the bilirubin‐albumin complexes decreased from 2.07 to 0.54×108M‐1 for HSA and from 2.16 to 0.87×107M‐1 for BSA.

These data indicate that the histidyl residues are relatively unimportant for maintaining the native tertiary structure of BSA and HSA, but they are critical for determining the binding capacity of the albumins. Our data also imply that the tertiary structure of the BSA molecule is more labile than that of HSA.
PHYTOCHROME MEDIATION OF UREDOSPORE GERMINATION IN THE FUNGUS PUCCINIA GRAMINIS
Authors: Schneider Michael J. , Murray Betty Jean
Published: January 2008

Abstract—Applying criteria used for higher plants, phytochrome mediation of uredospore germination in the stem‐rust fungus, Puccinia graminis f. sp. tritici (Eriks & Henn) Guyot is established. A 1 min red irradiation at 660 nm promotes uredospore germination and this potentiation of promotion is photoreversible by a 1 min far‐red irradiation at 730 nm.
pH DEPENDENCE OF SENSITIZED PHOTOOXIDATION IN MICELLAR ANIONIC AND CATIONIC SURFACTANTS, USING THIAZINES DYES
Authors: Bagno O. , Soulignac J. C. , Joussot‐Dubien J.
Published: January 2008

Abstract— Our study of the kinetics of sensitized photooxidation, as a function of pH in anionic micellar systems using cationic dyes as sensitizers, shows that adsorption of the dye slows the protonation step of his triplet state. This observation has important implicaticins in interpretation of results in the so‐called photodynamic effect in biological systems: using cationic dyes as sensitizers the rate of photooxidation for the same pH is different depending whether or not the medium allows adsorption of the dye.