bluuebunny/crossref_metadata_2025 huggingface dataset:
EXCITATION and DE‐EXCITATION PROCESSES IN LANTHANIDE CHELATES BEARING AROMATIC SIDECHAINS
Authors: Abusaleh Adnan , Mearest Claude F.
Published: January 2008

Abstract— Chelating agents comprised of an ethylenediaminetetraacetate group covalently attached to an aromatic sidechain (indole, benzyl, p‐methoxybenzyl, or p‐cyanobenzyl) have been used to investigate interactions between each sidechain and a lanthanide ion chelated by the ethylenediaminetetraacetate group. Lanthanum, samarium, europium, gadolinium, terbium, dysprosium, and ytterbium were studied. Results from measurements of fluorescence, phosphorescence, and lanthanide luminescence indicate the importance of electron transfer, as well as energy transfer, processes in these chelates. Because of the structure of the chelates studied, the sidechains and bound metals do not interact strongly enough to perturb their energy levels; however, large effects on quantum yields, including quenching or enhancement of aromatic phosphorescence, quenching or enhancement of lanthanide luminescence, and quenching of aromatic fluorescence are observed. Applications to studies of proteins are discussed.
TRANSITORY UV RESISTANCE DURING GERMINATION OF UV‐SENSITIVE SPORES PRODUCED BY A MUTANT OF Bacillus cereus 569
Authors: Weinberger Sarah , Evenchik Zigmund , Hertman Israel
Published: January 2008

Abstract— A mutant of Bacillus cereus 569, isolated by us and designated 2422 is unable to excise cyclobutane‐type dimers and spore‐specific photoproducts from the DNA of UV‐irradiated vegetative cells and dormant spores. The deficiency in the excision repair mechanism was found to be at the post‐incision step in the exonuclease‐mediated removal of the photoproducts. During germination, the mutant B. cereus 2422 exhibits UV‐resistance and an efficient photoproduct removal which is followed by DNA repair synthesis. The data presented indicate the existence of germinative excision repair in B. cereus 569.
QUENCHING OF CHEMIEXCITED TRIPLET ACETONE BY BIOLOGICALLY IMPORTANT COMPOUNDS IN AQUEOUS MEDIUM
Authors: Catalani Luiz H. , Bechara Etelvino J. H.
Published: January 2008

Abstract— Thermolysis of tetramethyl‐l,2‐dioxetane is a convenient source of triplet acetone, which can be monitored in aerated solutions by the sensitized fluorescence of 9,10‐dibromoanthracene. We have investigated the quenching of chemiexcited triplet acetone in air‐equilibrated aqueous solutions containing the 9,10‐dibromoanthracene‐2‐sulfonate ion by five classes of compounds: indoles, tyrosine derivatives, quinones, riboflavin, and xanthene dyes. Quenching rates for indoles, tyrosine and its 3,5‐dihalogenoderivatives, and xanthene dyes (kq= 108‐109M‐1 s‐1) are considerably smaller than the diffusion controlled rate, whereas those for quenchers with high electroaffinities, such as quinones (IP = 10–11 eV), approach the diffusion controlled rate (kq= 1010 M‐1 s‐1). Energy transfer for riboflavin probably occurs by a triplet‐singlet Förster type process.

A comparison of the present data with previous studies of quenching of enzymically generated triplet acetone (isobutanal/O2/horseradish peroxidase) by the same classes of quenchers (except riboflavin) reveals that, independent of the nature of the quencher and the deactivation mechanism, the Stern‐Volmer quenching constants (kq t0) are systematically about one order of magnitude higher in the enzymatic system. The difference is attributed to a longer lifetime of triplet acetone in the latter case, “protected” in an enzyme cavity against collisions with dissolved oxygen.
EFFECTS OF 8‐METHOXYPSORALEN PLUS NEAR‐ULTRAVIOLET LIGHT ON THE NEMATODE
Authors: Fujita Hitoshi , Ishii Naoaki , Suzuki Kenshi
Published: January 2008

Abstract— Effects of 8‐methoxypsoralen plus near‐UV light on the nematode Caenorhabditis elegans were studied as a novel example of photosensitized actions at the individual level. Either the eggs or the worms were illuminated with near‐UV light in the presence of 8‐methoxypsoralen. The treatment decreased hatchability of the eggs depending on light fluence and concentration of the sensitizer. Inhibition of growth and premature death were observed when the larvae in the second stage were illuminated in the presence of 8‐methoxypsoralen. When young adults were treated before the beginning of egg‐laying, they grew to lay eggs, but the total number of eggs deposited per hermaphrodite was decreased and the life span was shortened.
INDUCTION OF UMUC+ GENE EXPRESSION IN Escherichia coli IRRADIATED BY NEAR ULTRAVIOLET LIGHT
Authors: Sato Noriko , Ohnishi Takeo , Tano Keizo , Yamamoto Kazuo , Nozu Kehchi
Published: January 2008

Abstract— The induction of umu+ gene expression caused by irradiation with near ultraviolet light (BLB; black light blue) was studied in Escherichia coli K‐12 strains with special reference to the effects of SOS repair deficiencies. The umuC+ gene expression was measured as the enzymic activity of (J‐galactosidase which is regulated by the promoter of the umuC+ operon carried in a plasmid DNA carrying a promoter of umuC* operon, a umuD+ gene and a umuC+‐lacZ+ gene fusion. A high induction of the umuC+ gene expression was observed in the uvrA cells in the case of BLB or UV irradiation as compared with the parental wild‐type cells. Caffeine inhibited the induction of the umuC* gene expression due to BLB or UV irradiation in both strains. There was very little induction in lexA and recA mutants. In contrast with UV irradiation, there was no killing of cells by BLB irradiation in any strain (wild, uvrA, lexA and recA). Possible implications of the present experimental results were discussed.
CONTROL BY PHYTOCHROME OF EXTENSION GROWTH and POLAROTROPISM IN CHLORONEMATA OF Funaria hygrometrica
Authors: Bittisnich D. , Williamson R. E.
Published: January 2008

Abstract— The photocontrol of extension growth and polarotropism has been investigated in chloronemata of the moss Funaria hygrometrica Hedw. When grown on a 12/12 h light/dark cycle, chloronemata show light‐stimulated diurnal variations in elongation rate with no evidence of a circadian rhythm. Regulation of elongation by a low energy, photoreversible phytochrome mechanism was demonstrated by brief red (R) and far red (FR) irradiations given either at the end of the day (EOD) or 6 h later as a night break (NB). Night break irradiation with polarised R caused polarotropic reorientations of chloronemal growth also through a FR‐reversible, low energy phytochrome mechanism. Such transformations of Pr to Pfr were accompanied by a 90° shift in the orientation of the phytochrome chromophore. Microbeam irradiation indicated that the phytochrome chromophores involved in both responses were predominantly, if not entirely, located in the tip of the apical chloronemal cell.
TRIPLET EXCITED STATES OF 4',5'‐PHOTOMONOADDUCTS OF 3‐ CARBETHOXYPSORALEN and 8‐METHOXYPSORALEN WITH DNA NUCLEOSIDES
Authors: Blais J. , Ronfard‐Haret J. C. , Vigny P. , Cadet J. , Voituriez L.
Published: January 2008

Abstract— Triplet absorption spectra, triplet extinction coefficient and intersystem crossing for 4',5'‐monocycloadducts of 3‐carbethoxypsoralen (3‐CPs) with thymidine (dThd) and uridine (dUrd) in ethanol have been investigated in order to elucidate whether their triplet state properties could be the limitating step for a further photoreaction of 3‐CPs monoadducts with DNA nucleosides. The comparison between the triplet characteristics of 4',5'‐monoadducts of 3‐CPs and those of 8‐methoxypsoralen (8‐MOP) shows that the quantum yield is much higher in the case of 3‐CPs than for 8‐MOP. The monofunctionality of 3‐CPs cannot therefore be ascribed to the triplet excited states properties of its monoadducts. It is likely that steric hindrance introduced by the bulky carbethoxy group remains a reasonable explanation.
CIRCULAR DICHROISM OF LIGHT‐HARVESTING COMPLEXES FROM PURPLE PHOTOSYNTHETIC BACTERIA*
Authors: Cogdell Richard J. , Scheer Hugo
Published: January 2008

Abstract— The CD spectra of a range of antenna complexes from several different species of purple photosynthetic bacteria were recorded in the wavelength range of 190 to 930 nm. Analysis of the far UV CD (190 to 250 nm) showed that in each case except for the B800‐850 from Chr. vinosum the secondary structure of the light‐harvesting complexes contains a large amount of α‐helix (˜50%) and very little 0‐pleated sheet. This confirms the predictions of the group of Zuber of a high a‐helical content based upon consideration of the primary structures of several antenna apoproteins. The CD spectra from the carotenoids and the bacteriochlorophylls show considerable variations depending upon the type of antenna complex. The different amplitude ratios in the CD spectrum for the bacteriochlorophyll Qy, Qx and Soret bands indicate not only different degrees of exciton coupling, but also a strong and variable hyperchromism (Scherz and Parson, 1984a, b).
FLUENCE RATE COMPENSATION OF THE PERCEPTION OF RED: FAR‐RED RATIO BY PHYTOCHROME IN LIGHT‐GROWN SEEDLINGS*
Authors: Smith Harry , Hayward Peter
Published: January 2008

Abstract— The hypothesis that phytochrome functions as a sensor of vegetational shade through the perception of the red: far‐red photon fluence rate ratio requires that the mechanism of perception be compensated for wavelength‐independent fluctuations in fluence rate (Smith, 1982). This paper seeks to establish the lower limit of fluence‐rate compensation and to assess whether or not compensation is effective at the total fluence rates typical of herbaceous canopies. Using specially‐designed cabinets, Sinapis alba L. (white mustard) seedlings were grown from germination under a range of total photosynthetically‐active radiation (PAR = 400 to 700 nm) values and a range of red: far‐red ratios. The data indicate that fluence‐rate compensation is effective above a PAR value of ca. 60 μ.mol m2 s'. Pretreating seedlings at high red: far‐red ratio and a PAR level of 300 (μmol m2S‐1for increasing periods of time led to an extension of fluence rate compensation to lower fluence rates. The results are discussed in relation to the photosynthetic competence of the seedlings grown under these conditions.
PHOTOREGULATION OF NITRATE UTILIZATION IN GREEN ALGAE AND HIGHER PLANTS*
Authors: APARICIOH Pedro J. , Balandin Teresa , Maurino Sofía G. , Maldonado José M.
Published: January 2008

Abstract— Nitrate reductase from eukaryotes can be reversibly inactivated, blue light being an effective activating agent both in vitro and in vivo. Hydroxylamine proved to be a powerful inactivating agent of Ankistrodesmus braunii nitrate reductase. Irradiation with blue light of NH2OH‐inactivated nitrate reductase, specially in the presence of μM amounts of FAD, promoted the recovery of the enzyme activity. Similarly, photoexcited methylene blue reactivated spinach nitrate reductase. On the other hand, in vitro nitrate reductase is highly susceptible to photodynamic inactivation caused by singlet O2. Aerobic incubation of the active spinach enzyme with either FMN or methylene blue under either blue or red light respectively led to its irreversible inactivation. Irradiation of frozen and thawed spinach leaf discs also promoted, in situ, an irreversible inactivation of nitrate reductase, provided that 62 was present in the incubation mixture. Thus, either in vitro or in situ, light can cause two quite different responses of nitrate reductase, its blue light‐dependent photoactivation in a flavin sensitized reaction and its photodynamic inactivation in a singlet O2‐dependent process.
KINETICS OF Pfr APPEARANCE IN Amaranthus caudatus‡
Authors: Kendrick R.E. , Kome J. , Jaspers P. A. P. M.
Published: January 2008

Abstract— The kinetics of the far‐red absorbing form of phytochrome (Pfr) appearance from intermediates in the pathway from the red absorbing form of phytochrome (Pr) to Pfr that accumulate under high fluence rate white light have been investigated in 3‐day old dark grown Amaranthus caudatus seedlings. The appearance of P(r after a 5 s white light pulse was measured over the temperature range ‐8 to 25°C in samples flushed with O2 or N2. Over the whole temperature range under anaerobic conditions the kinetics of the slowest component of Pfr appearance are faster than in the presence of O2. Arrhenius plots are linear over this temperature range and indicate the activation energy for the slowest component of Pfr appearance is 44.05 ± 1.97 kJ mol−1 for O2 and 53.69 ± 4.86 kJ mol−1 for N2.
EXCITED STATE PROPERTIES OF ∝aL‐TERTHIENYL and RELATED MOLECULES
Authors: Reyftmann J. P. , Kagan J. , Santus R. , Morliere P.
Published: January 2008

Abstract— The photophysical and photochemical properties of thiophene derivatives have been studied by fluorescence and by 353 nm laser flash spectroscopy. α‐Terthienyl and its derivatives show a moderate fluorescence quantum yield (less than 0.1) in cyclohexane, ethanol, or TritonX–100 micelles. An additional thiophene ring increases this value to 0.2 in ethanol or micelles. The transient triplet state of the six thiophenes is characterized by strong absorptions (ε⋍ 50000 M‐1 cm‐1) in the visible region. These triplet states are very long lived. They react with oxygen, producing singlet oxygen very efficiently because of their high quantum yield of triplet formation (0.1 to 0.3). They do not react with excellent hydrogen or electron donors such as indole, N‐acetyl tryptophanamide or cysteine. The hydrophobic thiophenes investigated are, therefore, Type II photodynamic agents almost exclusively.
DOES THE AEROBIC XANTHINE OXIDASE REACTION GENERATE SINGLET OXYGEN?*
Authors: Nagano Tetsuo , Fridovich Irwin
Published: January 2008

Abstract— The aerobic xanthine oxidase reaction causes the co‐oxidation of 2,5‐dimethylfuran to cis‐diacetylethylene and the bleaching of rubrene tetracarboxylate. These actions were suppressed by superoxide dismutase, catalase, desferoxamine and by benzoate and other hydroxyl radical scavengers. The bleaching of rubrene tetracarboxylate was not enhanced in D20. These results suggest that OHv, generated from O2‐ plus H2O2 by an iron‐catalyzed Haber Weiss reaction, was the responsible agent and that singlet oxygen was not detectably involved. Control experiments, in which singlet oxygen was generated photochemically, demonstrated that replacement of H2O by D2O caused the expected enhancement of the chemical reactivity of singlet oxygen under the conditions of these experiments and that O2‐, at concentrations achieved by the xanthine oxidase reaction, did not detectably quench singlet oxygen. We conclude that singlet oxygen, if produced at all during the aerobic xanthine oxidase reaction, cannot exceed 0.1% of the production of O2‐.
OPTICAL PENETRATION IN HUMAN INTRACRANIAL TUMORS
Authors: Svaasand Lars O. , Eixingsen Reinold
Published: January 2008

Abstract— The optical penetration depth has been measured in human intracranial tumors. The penetration depth in highly malignant gliomas is typically twice as large as the penetration depth in the surrounding normal brain tissue. Typical values for different wavelengths are: 1 mm for blue/green, 2.5 mm for red and 6 mm for near infrared. The penetration depth in a metastasis (from lung) is about the same as in the surrounding tissue.
IN VIVO ROLE OF SULFITE IN PHOTOCONTROL OF UROCANASE FROM Pseudomonas putida*
Authors: Venema Richard C. , Hunter John K. , Hug Daniel H.
Published: January 2008

Abstract— Urocanase from Pseudomonas putida becomes inactive in growing and resting cells and is activated by UV radiation. Sulfite addition to the bound nicotinamide adenine dinucleotide coenzyme has previously been shown to inactivate the enzyme in vitro. The enzyme released sulfite upon photoactivation. Whether sulfite addition and dissociation is involved in the in vivo photoregulation of urocanase was examined in this study. The dark reversion (inactivation) in cultures was markedly enhanced by growth at 32°C rather than at 24°C; cells grown at 32°C and resting cells were used to obtain in Wvo‐inactivated urocanase. We purified the in vivo‐inactivated enzyme and quantitated the amount of sulfite released through photodissociation. One mole of sulfite was released per mole of urocanase. This is based on a molecular weight of 110000 confirmed by gel electrophoresis and a protein estimation method validated by our data. Our previous report of sulfide inactivation of urocanase in vitro is now shown to have been mistaken; the inactivation resulted from the oxidation of sulfide to sulfite, which occurred in solution.
ISOMERS OF 3,7,11‐TRIMETHYLDODECA‐2,4,6,8,10‐ PENTAENAL (A LINEAR ANALOGUE OF RETINAL) and LOWER HOMOLOGUES IN THEIR INTERACTION WITH BOVINE OPSIN and BACTERIOOPSIN
Authors: Rao V. Jayathirtha , Zingoni Jesmael P. , Crouch Rosalie , Denny M. , Liu R. S. H.
Published: January 2008

Abstract— The all‐trans and 3 mono‐cir isomers of the title linear pentaenal have been prepared. Results of their interaction with bovine opsin and bacterioopsin are presented. Likewise, the negative results on two lower member homologs are described. Implications on the specificity of the binding sites are discussed.
ENERGY TRANSFER FROM ENZYME‐GENERATED TRIPLET CARBONYLS TO THYLAKOID MEMBRANE FRACTIONS ENRICHED IN PHOTOSYSTEMS I and II
Authors: Nassi Lilian , Cilento Giuseppe
Published: January 2008

Abstract— Enzyme‐generated triplet species transfer energy very efficiently to thylakoid membrane fractions enriched in either photosystem‐I or photosystem‐II. Independent of the nature of the triplet donor, the emission is always more intense with photosystem‐I. Since the fluorescence quantum yield of chlorophyll in PS‐I is lower and the rate of energy transfer usually smaller than to chlorophyll in PS‐II, the yield of 1S chlorophylls in PS‐I is substantially higher. This is tentatively attributed to more favorable reverse intersystem crossing from an upper triplet state in PS‐I.
PROOXIDANT and ANTIOXIDANT EFFECTS OF ASCORBATE ON PHOTOSENSITIZED PEROXIDATION OF LIPIDS IN ERYTHROCYTE MEMBRANES
Authors: Girotti Albert W. , Thomas James P. , Jordan John E.
Published: January 2008

Abstract— Continuous blue light irradiation of resealed erythrocyte ghosts at 37°C in the presence of uroporphyrin or protoporphyrin results in 1O2‐mediated (azide inhibitable) lipid peroxidation and membrane lysis. Lipid peroxidation was assessed by thiobarbituric acid reactivity and by quantitation of total hydroperoxides, while lysis was measured in terms of trappedglucose–6‐P release. Low concentrations of ascorbate, AH‐ (e.g. 0.5 mM). present at the start of irradiation, significantly enhanced the rates of lysis and peroxidation, whereas relatively high concentrations of AH‐ (e.g. 15 mM) inhibited both processes. By way of contrast. AH‐ produced only a dose‐dependent inhibition of the photoinactivation of lysozyme, added as an extramembranous target. No significant AH‐induced lipid peroxidation was observed in dark or light controls, plus porphyrin or minus porphyrin, respectively. Stimulation of peroxidation and lysis by low levels of AH‐ was enhanced by added Fe(III), abolished by EDTA. but unaffected by catalase or superoxide dismutase. A plausible explanation for these results is as follows. At low concentrations of AH‐ prooxidant activity is favored. Redox metal‐mediated breakdown of photoperoxides occurs, which tends to amplify lipid peroxidation. Neither O2‐ nor H2O2 appears to be involved. At significantly high concentrations, AH‐ acts predominantly as an antioxidant by intercepting 1O2 and/or sensitizer triplet, or by scavenging free radical intermediates of lipid peroxidation.
LASER FLASH AND STEADY‐STATE PHOTOLYSIS OF BENOXAPROFEN IN AQUEOUS SOLUTION*
Authors: Navaratnam Suppiah , Hughes John L. , Parsons Barry J. , Phillips Glyn O.
Published: January 2008

Abstract— On laser flash photolysis of aqueous solutions of benoxaprofen (BP), the BP triplet state is produced with a quantum yield of 0.19. One other unidentified species is also formed probably in a yield less than 0.02. Identical observations were made in alcoholic solution. The effect of potential hydrogen donors, isopropanol and histidine, on the kinetic reactivity of the BP triplet state, showed that for isopropanol the rate constant is slow (< 8 × 103 dm3 mol‐1 s‐1) if it occurs at all, whilst no reactivity with histidine could be seen. In oxygen uptake experiments, it was deduced that singlet oxygen is produced via the BP triplet state with a quantum yield of 0.18. There was no evidence for superoxide anion radical production. In other steady‐state photolysis experiments using high performance liquid chromatography, the quantum yield for loss of BP was determined to be 0.20, while the quantum yield for the only observed product, decarboxylated benoxaprofen, was estimated as 0.18. The involvement of the two major processes, i.e. singlet oxygen formation and BP decarboxylation, in BP phototoxicity is discussed.
ENERGY STORAGE IN THE PRIMARY PHOTOREACTION OF BOVINE RHODOPSIN. A PHOTOACOUSTIC STUDY
Authors: Boucher François , Leblanc Roger M.
Published: January 2008

Abstract— Photoacoustic spectroscopy is used to investigate the uptake of energy in the primary photoreaction of bovine visual pigment (Rhodopsin → Bathorhodopsin). It is shown that very concentrated dried rod outer segment membranes have a sufficient thermal diffusivity to be analyzed by this technique. From the photoacoustic and absorption spectra of these membranes, the low temperature dissipation spectrum has been obtained and the results are consistent with the storage of 145 kJ mol‐1 in the primary event of vision having a quantum yield of 0.67. By photoacoustic spectroscopy, this process is continuously monitored from 350 to 550 nm and its efficiency is found to vary by less than 10%, even in the spectral region of the β‐band of rhodopsin.
INHIBITION OF DNA SYNTHESIS BY PSORALEN‐INDUCED LESIONS IN XERODERMA PIGMENTOSUM AND FANCONI'S ANEMIA FIBROBLASTS
Authors: Gruenert D. C. , Kapp L. N. , Cleaver J. E.
Published: January 2008

Abstract— Exposure of human cells to psoralens and near‐UV light produces a mixture of monoadducts and crosslinks in DNA, which inhibit DNA synthesis by blocking replicon initiation and chain elongation. 8‐Methoxypsoralen (8‐MOP) has a greater effect than angelicin in normal, xeroderma pigmentosum, and Fanconi's anemia cells. Recovery of DNA synthesis is not detectable up to 8 h after exposure. The average distance between lesions that block replication in individual replicons was measured by means of bromodeoxyuridine photolysis. After exposure to 10 μg/mℓ of 8‐MOP and 7500 J/m2 of near‐UV light, blocks were formed every 20 μm. Replicon initiation was inhibited by exposure to near‐UV light alone in normal and xeroderma pigmentosum. Exposure to low concentrations of angelicin or 8‐MOP plus near‐UV light inhibited replicon initiation in normal and Fanconi's anemia cells, but not in xeroderma pigmentosum cells. Inhibition of initiation was not obvious after treatment with high concentrations of 8‐MOP or angelicin because of the dominant effect of crosslinks in blocking chain elongation.
THE PHOTOLYSIS OF PENICILLAMINE DISULPHIDE INWATER–2‐PROPANOL SOLUTIONS
Authors: Grant D. W. , Stewart J. H.
Published: January 2008

Abstract— Quantum yields of thiol, ammonia and valine were measured in the photolysis of aqueous deoxygenated solutions of penicillamine disulphide containing various concentrations of 2‐propanol. Low concentrations of alcohol (< 1 mol dm‐3) had a negligible effect on the thiol and valine yields but completely inhibited the production of ammonia. High concentrations of alcohol increased the thiol and ammonia vields, while the valine yield exhibited a maximum at an alcohol concentration of about 3 mol dm‐3. The increased thiol yields were interpreted on the basis of the photolysis of hydrogen‐bonded alcohol‐amino acid “complexes”.
A NEW MONOFUNCTIONAL PYRIDOPSORALEN: PHOTOREACTIVITY and REPAIR IN YEAST
Authors: Magana‐Schwencke N. , Moustacchi E.
Published: January 2008

Abstract— The newly synthesized derivative of psoralen, the pyrido (3,4‐c) 7 methylpsoralen (MePyPs), acts in combination with 365 nm ultraviolet as a monofunctional agent on yeast DNA. In vivo, its photoaffinity for DNA is much higher than that of the bifunctional agent, 8‐methoxypsoralen (8‐MOP). The MePyPs photo‐induced monoadducts are almost completely removed from wild type cells DNA as efficiently as 8‐MOP photo‐induced adducts during post‐treatment incubation. This process is blocked in excision‐repair defective mutants (6 to 10% residual excision in radl‐Δ or rad2‐Δ). For an equal number of photoinduced lesions, the DNA single strand breaks which are produced concomitantly to MePyPs or 8‐MOP photoadducts excision are rapidly rejoined in the case of 8‐MOP whereas they are only partly resealed for the MePyPs treatment. The high photo‐toxicity of MePyPs, a promising agent for photo‐chemotherapeutic use, is explained in terms of the high photoaffinity for DNA.
PHOTOGENERATION OF SUPEROXIDE and DECARBOXYLATED PEPTIDE RADICALS BY CARBOQUONE, MITOMYCIN C and STREPTONIGRIN. AN ELECTRON SPIN RESONANCE and SPIN TRAPPING STUDY
Authors: Carmichael Alasdair J. , Samuni Amram , Riesz Peter
Published: January 2008

Abstract—

Visible light (405–615 nm) excitation of carboquone, mitomycin C, and streptonigrin dissolved in dimethylsulfoxide in the presence of oxygen generates superoxide anion radicals (O2−). The quantum yields for these reactions range from 4.2 times 10−2 (carboquone, λ= 615 ± 10 nm) to 7.3 times 10−6 (streptonigrin, λ=545 ± 10 nm). O2− radicals were spin trapped with 5,5‐dimethyl‐1‐pyrroline‐1‐oxide (DMPO) and identified by electron spin resonance (ESR). The efficiency of DMPO to spin trap O2− in dimethylsulfoxide was determined and indicated that 91% of the O2− present in dimethylsulfoxide is trapped by DMPO. The oxidation of the photoexcited drug molecules occurs via a direct electron transfer to dissolved oxygen in solution. Ultraviolet irradiation (λ= 313 ± 10 nm) of the aminoquinone drug solutions (80% H2O, 20% dimethylsulfoxide) in the presence of peptides results in the decarboxylation of the peptides. In this case the photoexcited drugs are reduced, abstracting an electron from the C‐terminal carboxyl group of the peptides. The reaction is specific to the C‐terminal amino acid of the peptide. The decarboxylated peptide radicals were spin trapped with 2‐methyl‐2‐nitrosopropane (MNP) and identified by ESR.
RESULTS OF STUDIES OF POTENTIAL LIGHT SPECTRUM EFFECTS ON HUMAN PERFORMANCE
Authors: Irvine A. Blair , Zauner Christian W. , Allen Robert
Published: January 2008

Abstract—

Recent findings suggest that the spectrum of light from fluorescent lamps may influence human behavior and physiology. To evaluate possible light effects on exercising humans, physical performance was measured under two widely different light spectra: the spectrum from one bulb‐type (General Electric Croma‐50) approximated that of sunlight, while the other (General Electric Delux Warm White) was heavy in the red end of the spectrum. Twenty eight moderately active subjects (14 males:14 females; ages 20–32 yrs) were acclimated to light conditions for 30 min before being tested to maximal effort with a modified Balke treadmill protocol (Balke et al., 1954). The interval between tests under each light condition averaged 6.9 days. Heart rate and respiratory parameters were measured at rest, submaximum exercise (5% treadmill grade), maximum, and 3 min after test termination. Data analysis (2‐way ANOVA) indicated expected differences between genders only, with no effects attributable to light spectrum. The mean V02 max was 44.8 ml/kg min for males vs 38.6 ml/kg min for females. Mean maximum heart rate was 197 bpm for males and 194 bpm for females. Mean maximum treadmill grade averaged 24.3% for men and 22.0% for women. A significant difference in submaximum heart rate was found to be due to presentation order. These results fail to indicate that fluorescent light type influences physical performance.
MULTIPLICATIVE ACTION OF A UV‐B PHOTORECEPTOR and PHYTOCHROME IN ANTHOCYANIN SYNTHESIS
Authors: Yatsuhashi Hiroko , Hashimoto Tohru
Published: January 2008

Abstract—

Using 290‐nm light, which excites only a UV‐B photoreceptor, and 385‐ and 660‐nm light, which activate only phytochrome, the fluence rate‐response curves of monochromatic irradiations for anthocyanin synthesis in the first internodes of broom sorghum (Sorghum bicolor Moench, cv. Acme Broomcorn) were analyzed. Although the two photoreceptors absorbed light independently, they multiplicatively increased the action of each other. Accordingly, when the fluence rates of both wavelengths were changed together, the resulting slopes of the fluence rate‐response curves of double‐log plots were steep compared with the slopes obtained with the respective monochromatic irradiations. The slopes of fluence rate‐response curves for monochromatic irradiations at 325 to 345 nm were steeper than those at other wavelengths. This difference was shown to be due to the multiplicative actions of both photoreceptors.
PHOTOPHYSICS OF A WELL CHARACTERIZED HUMIC SUBSTANCE
Authors: Power Joan F. , Sharma D. K. , Langford Cooper H. , Bonneau Roland , Joussot‐Dubien Jacques
Published: January 2008

Abstract— The transient absorbance observed after flash excitation of a well characterized humic substance (“Armadale” fulvic acid) may be analyzed into three components. Two arise promptly (< 20 ps) and are assigned to a solvated electron (on the basis of decay and quenching) and its corresponding radical cation (on the basis of common origin). The third is a broad featureless band which arises only after a few ns and remains for long times. It is suggested to include triplets that may sensitize singlet oxygen.
MUTAGENIC EFFECTS PHOTOINDUCED IN MAMMALIAN CELLS IN VITRO BY TWO MONOFUNCTIONAL PYRIDOPSORALENS
Authors: Papadopoulo D. , Averbeck D. , Moustacchi E.
Published: January 2008

Abstract— The photobiological activity of the two monofunctional pyridopsoralens pyrido (3,4‐c) psoralen (PyPs) and 7‐methyl pyrido (3,4‐c) psoralen (MePyPs) was studied in mammalian cells in vitro taking 8‐methoxypsoralen (8‐MOP) as a reference compound.

In the presence of 365‐nm irradiation (UVA) MePyPs was found to be more effective than 8‐MOP in terms of DNA photobinding capacity and inhibition of cell cloning ability in Chinese hamsterV–79 cells. As a function of UVA dose and of the number of total photoadducts induced MePyPs produced a higher frequency of 6‐thioguanine resistant mutants than 8‐MOP. PyPs showed an intermediate response for cell killing and mutation induction. At equal cytotoxic levels both monofunctional pyridopsoralens exhibited the same mutagenic activity as the Afunctional furocoumarin 8‐MOP.

The antiproliferative effect being taken as indicative for an efficient photochemotherapeutic activity against psoriasis, the inhibition of cloning capacity induced by MePyPs plus UVA was studied in parallel on human skin fibroblasts. Such cells were more sensitive to 8‐MOP photoadditions thanV–79 cells and even more so to MePyPs photoadditions. Data obtained on the rate of DNA semi conservative synthesis on both cell lines following treatments with the two compounds are in line with these observations.
THE CYTOTOXIC AND MUTAGENIC EFFECTS OF UVA RADIATION ON L5178Y MOUSE LYMPHOMA CELLS
Authors: Hitchins V. M. , Withrow T. J. , Olvey K. M. , Harleston B. A. , Ellingson O. L. , Bostrom R. G.
Published: January 2008

Abstract— A broad‐band UVA source that emits primarily350–400 nm radiation and no measurable radiation below 340 nm was used to test toxicity and mutagenicity at the thymidine kinase locus in L5178Y, subclone 3.7.2C (TK+/‐) mouse lymphoma cells. Cells were exposed to a fluence of 0 to 80 × 104 J/m2. The relationship between UVA fluence and survival was found to have a shoulder region followed by an exponential decrease in survival at higher fluence levels. An exposure‐dependent increase in mutation was observed with increasing fluences from 0 to about 60 × 104 J/m2. An approximately 3‐ to 4‐fold increase in mutations (trifluorothymidine resistance) over unexposed, control cells was seen at a fluence that resulted in 90% cell killing. We conclude that UVA radiation is a mutagen in the L5178Y mouse lymphoma cells used in this study.
BIOLOGICAL ACTIVITIES OF PHTHALOCYANINES—IV. TYPE II SENSITIZED PHOTOOXIDATION OF L‐TRYPTOPHAN AND CHOLESTEROL BY SULFONATED METALLO PHTHALOCYANINES
Authors: Langlots R. , Ali H. , Brasseur N. , Wagner J. R. , Lier J. E. van
Published: January 2008

Abstract— Sulfonated phthalocyanine and a series of its metal chelates in combination with red light irradiation led to the degradation of L‐tryptophan in oxygenated aqueous solution. The photoproducts and the rate of transformation of L‐tryptophan are compared with hematoporphyrin and rose bengal sensitized photooxidation. In all cases the primary photoproducts are characterized as cis and trans‐3a‐hydroperoxy‐l,2,3,3a,8,8a‐hexahydropyrrolo[2,3‐b]indole‐2‐carboxylic acid. Support for the involvement of singlet excited oxygen is obtained from azide inhibition and the formation of the specific singlet oxygen product with cholesterol. We observed the contribution of another pathway in the case of the manganese complex.
ULTRAVIOLET PHOTOBIOLOGY AND SPECTROSCOPY USING SYNCHROTRON RADIATION*
Authors: Ito Takashi , Sutherland John , Woodhead Avril
Published: January 2008

Experimental photobiology and spectroscopy depend upon sources of visible and ultraviolet radiation. Synchrotron radiation has properties complementary to other sources: the spectrum is continuous, extending from the infrared through the visible and ultraviolet wavelengths into the X‐ray region; the radiation consists of subnanosecond pulses occurring millions of times per second; the source is small and the radiation well‐columnated and partially polarized. These desirable properties have generated interest among scientists in many disciplines and have led to the construction of electron storage rings as dedicated sources of synchrotron radiation. More advanced sources are being proposed. This issue of Photochemistry and Photo biology is devoted to the proceedings of a seminar entitled Ultraviolet Photobiology and Spectroscopy using Synchrotron Radiation, sponsored by the Japan Society for the Promotion of Science and the Division of International Programs of the National Science Foundation (USA). The three day seminar, held at Brookhaven National Laboratory in October 1985, brought together scientists from the United States and Japan who design the special facilities and use synchrotron radiation sources to study the structure of biological molecules and the damage caused by ultraviolet radiation. The papers presented fall into four categories: instrumentation, vacuum ultraviolet (UV) radiation effects, vacuum ultraviolet spectroscopy and time—resolved fluorescence spectroscopy.
QUANTITATION OF DNA DAMAGE IN NON‐RADIOACTIVE DNA
Authors: Sutherland Betsy M. , Ciarrocchi Giovanni , Ciomei Marina , Sutherland John C.
Published: January 2008

Three principal methods have been developed for measuring femtomoles of damage in nanogram quantities of non‐radioactive DNA. Lesions which can be quantified include single and double strand breaks, alkali labile sites including apurinic and apyrimidinic sites, and pyrimidine dimers. The first in vitro method measures the conversion of supercoiled DNA to relaxed or linear molecules, and can detect up to four lesions per molecule. The second in vitro method (supercoil depletion) assesses the fraction of intact linear molecules of homogeneous length, and allows detection of 8 lesions/molecule. The third method, measurement of molecular length distributions of DNAs of heterogeneous length, reveals the extent of DNA damage and repair in vivo or in vitro.
SOFT X‐RAY SCANNING MICROSCOPY: ITS PRACTICAL USE FOR ELEMENTAL MAPPING AT THE NSLS U15 BEAMLINE
Authors: Jacobsen C. , Kenney J. M. , Kirz J. , McNulty I. , Rosser R. J. , Cinotti F. , Rarback H. , Shu D.
Published: January 2008

Scanning soft X‐ray microscopy offers several advantages over other forms of X‐ray microscopy. It subjects the specimen to the lower doses of radiation and by digitally recording the image, gives direct quantitative information on the absorption of the specimen as a function of position. Elemental maps can be produced easily by comparing images taken at different wavelengths, chosen to exploit X‐ray absorption edges or resonances. This technique was used to explore the distribution of calcium in 0.2 μm‐thick bone specimens, detecting concentrations of 5% by weight, with a spatial resolution of 0.2 μm. Progress in X‐ray sources in the form of undulators and in X‐ray optics indicates that soon the range of elements that can be mapped will be extended and the spatial resolution and elemental sensitivity will be improved by an order of magnitude.
MECHANISM OF CONCENTRATION QUENCHING OF A XANTHENE DYE ENCAPSULATED IN PHOSPHOLIPID VESICLES
Authors: Plant Anne L.
Published: January 2008

Encapsulating a xanthene dye in phospholipid vesicles produces vesicle solutions that contain dye at very high microscopic concentrations, but have a low overall optical density, thereby eliminating reabsorption. Using this system, we have studied the effects of concentration on the fluorescence lifetime of one such dye, sulforhodamine 101. We have observed that the lifetime decreases as a function of encapsulated dye concentration, which is indicative of collisional quenching. The lifetime decreases from 4.5 nsec for sulforhodamine in dilute aqueous solution to 0.69 ns at an encapsulated concentration of 33 mM. The bimolecular rate constant for this event is 2.6 1010M‐1 s‐1, consistent with a diffusion controlled event. However, the quenching constant calculated from changes in intensity is 2.2 1011M‐1 s‐1. Thus, collisional quenching is not the predominant mechanism of quenching. The absorption spectra of dye in vesicles indicate an important contribution from static complex formation. Förster distance calculations indicate that energy transfer can also occur to a significant extent, with a predicted efficiency of transfer of 34% at a dye concentration of only 1 mM
STUDIES ON ENERGY DISSIPATION IN PHYCOBILISOMES USING THE KENNARD‐STEPANOV RELATION BETWEEN ABSORPTION AND FLUORESCENCE EMISSION SPECTRA
Authors: Bjourn L. O. , Bjourn G. S.
Published: January 2008

Absorption and fluorescence emission spectra were measured at room temperature (ca. 22°C) for solutions of phycocyanin‐1, phycocyanin‐2 and allophycocyanin from Phormidium luridum, and also for phycobilisome preparations from various blue‐green algae (Anabaena variabilis, Nostoc muscorum strain A, Nostoc sp. strain Mac, Phormidium luridum). Kennard‐Stepanov (KS) temperatures (T) were computed using the Kennard‐Stepanov relationship F() = b A() ‐5 exp(‐h/kT), where F() stands for fluorescence (energy per wavelength interval) as a function of wavelength (), A() is absorbance as a function of wavelength, b a proportionality factor, and h, c and k are Planck's constant, the velocity of light and Boltzmann's constant, respectively.

In most cases experimenta/ data followed the expected relationship, but at low ionic strength allophycocyanin gave a clearly biphasic KS plot, i.e. In 5F()/A() vs 1/. This could be due to the presence of both monomers and trimers in the sample at low ionic strength.

For purified allophycocyanin and phycocyanins (PC‐1 and PC‐2) as well as phycobilisomes from Phormidium luridum, the KS temperatures were only slightly (insignificantly) elevated above the sample temperature. Thus, after absorption of a photon, vibrational and configurational equilibration is essentially completed before emission of the fluorescence photon takes place.

For phycobilisomes from Anabaena variabilis and the two Nostoc species the KS temperatures were moderately elevated. Since there was no correlation between radiation temperature and excitation wavelength, the elevation is not due to excess (undissipated) vibrational energy, but rather to incomplete configurational equilibration.
INTERACTIONS BETWEEN DNA AND PSORALENAMINES STUDIED WITH DICHROISM TECHNIQUES
Authors: Nordean Bengt , Wirth Michael , Ygge Birgitta , Buchardt Ole , Nielsen Peter E.
Published: January 2008

The interaction of a series of water‐soluble mono‐ and bis‐psoralenamines with calf thymus DNA has been studied with flow UV linear dichroism (LD), circular dichroism (CD) and equilibrium techniques. The positive charge of a protonated amino group strongly enhances the DNA affinity compared to that of the parent compound, 8‐methoxypsoralen. The orientation of the psoralen when bound to DNA, depends on the position of the amino substituent. With amino substituents in the 5‐position (on the‘hydrophobic edge’of psoralen) psoralenamines tend to bind with a considerable tilt relative to the average orientation of the DNA base‐pairs. The tilt generally increases with an increased psoralen: base‐pair ratio, indicating a more random, nonintercalated binding. With the amino substituents in the 8‐position the psoralen binds with its plane parallel to that of the DNA bases as expected for intercalation. The DNA CD supports that these psoralenamines induce a considerable perturbation of the DNA structure, and the CD induced in the psoralen chromophore is in qualitative agreement with intercalation. The study also includes a theoretical and an experimental determination of the UV transition moments of the psoralen chromophore.
THE EFFECT OF THE ANTIPSORIATIC DRUG METABOLITE ETRETIN (Ro 10‐1670) ON UVB IRRADIATION INDUCED CHANGES IN THE METABOLISM OF ARACHIDONIC ACID IN HUMAN KERATINOCYTES IN CULTURE
Authors: Punnonen Kari , Puustinen Tapio , Jansean Christer T.
Published: January 2008

[14C]Arachidonic acid was avidly incorporated into human keratinocytes in culture and following exposure to UVB irradiation of 9 mJ/cm2 (erythemally effective, EE) substantial amounts of 14C‐radiolabel were released from the cells. The release of radiolabel was accompanied by a decrease in the labelling of phosphatidylethanolamine whereas the labelling of triacylglycerols and cholesteryl esters was increased. Keratinocytes produced significant amounts of prostaglandin E2 (PGE2) and following UVB irradiation of 9 mJ/cm2 (EE) the formation of prostaglandin E2 was increased.

Etretin (Ro 10‐1670), the active metabolite of the antipsoriatic drug etretinate (Ro 10‐9359), affected significantly neither the total release of radiolabel induced by UVB nor the formation of prostaglandin E2. However, in the presence of etretin the UVB irradiation induced transfer of [l4C]arachidonic acid into triacylglycerols and cholesteryl esters was not increased as much as in the corresponding experiments without etretin. On the basis of the present study it appears that etretin does not interfere with the release of arachidonic acid in amounts which could be related to the therapeutic effects of the combination of retinoids with UVB irradiation (Re‐UVB) in the treatment of psoriasis.
NON‐INVASIVE TECHNIQUE FOR OBTAINING FLUORESCENCE EXCITATION AND EMISSION SPECTRA IN VIVO
Authors: Pottier R. H. , Chow Y. F. A. , LaPlante J.‐P. , Truscott T. G. , Kennedy J. C. , Beiner L. A.
Published: January 2008

An intensified photodiode array forms the heart of a sensitive spectrophotofluorometry system that permits the rapid and non‐invasive determination of fluorescence emission spectra in the skin of living, non‐anesthetized animals. Using this system, we found it possible to obtain good emission and excitation spectra of the material responsible for the weak red fluorescence that characterizes normal mouse skin, and to follow the biosynthesis and subsequent clearance of protoporphyrin IX in the skin of non‐anesthetized mice that had been given various doses of the porphyrin precursor 5‐aminolevulinic acid.
PHOTOOXYGENATION OF METHYL LINOLEATE SENSITIZED BY PORPHYRINS AND DYES IN ACETONITRILE SOLUTION AND AQUEOUS EMULSION SYSTEMS
Authors: Ohtani Bunsho , Nishida Makoto , Nishimoto Sei‐ichi , Kagiya Tsutomu
Published: January 2008

Photooxygenation reaction of an unsaturated fatty acid ester, methyl linoleate (methyl 9‐cis.12‐cis‐octadecadienoate, ML‐H), sensitized by porphyrins and several types of dyes has been studied in aqueous emulsion and acetonitrile solution under air at 40°C. The oxygen (O2) uptake proceeded slowly in the absence of sensitizers upon irradiation of an aqueous emulsion and an acetonitrile solution of ML‐H (20 mM) at ?ex > 290 nm (11.4 and 6.1 μmol h‐1, respectively). The rate of O2 uptake was enhanced by a catalytic amount (0.1 mM) of porphyrins and dyes; hematoporphyrin (HP), zinc tetrakis(N‐methyl‐4‐pyridiniumyi)porphyrin (ZnTMPyP), methylene blue (MB), rose bengal (RB), acridine orange (AO), and acriflavine (AF). In both systems, the sensitized photooxidation of ML‐H by O2 proceeded equimolarly to produce isomeric mixture of C9 and C13 hydroperoxides having the trans,cis and trans,trans conjugated diene configurations, independent of the types of the sensitizers used. The yield ratio of trans,trans/ trans,cis products in the MB‐sensitized photooxygenation in acetonitrile and aqueous emulsion were almost equal (0.32 and 0.35. respectively). The sensitizing activity of the sensitizers, as measured by the quantum yield of O2 uptake, increased in the order: MB (≃ 0) < ZnTMPyP < RB < HP < AF < AO in the aqueous emulsion and AO < AF < HP < RB = MB in the acetonitrile solution. The order in homogeneous acetonitrile solution was interpreted by the sensitizing ability of the dyes to produce singlet oxygen, while that in heterogeneous aqueous emulsion was correlated to the lipophilicity of dyes as well as the singlet‐oxygen‐producing ability.
THE EFFECTS OF ULTRAVIOLET LIGHT ON HOST CELL REACTIVATION AND PLAQUE SIZE OF Herpes simplex VIRUS TYPE I IN C3H/lOT1/2 MOUSE CELLS
Authors: Montes Joseph G. , Taylor William D.
Published: January 2008

—Herpes simplex virus — type 1 (HSV‐I) plaque‐forming ability and plaque size were measured on C3H/1OT1/2 cell monolayers as functions of pretreatment dose with UV light at different times before inoculation with virus, in order to determine if UV‐enhanced reactivation (ER) of UV‐irradiated virus. as well as associated phenomena, could be obtained in this cell system. The number of virus plaques observed (i.e. the capacity of the cells to support virus growth) and the size of the plaques were found to increase substantially with pretreatment of the cells with UV light. However, no significant ER was observed. Therefore, the mechanisms responsible for the increases in plaque size and cell capacity seem to be independent of those responsible for ER. In work by others. C3H/l0T1/2 cells have hcen transformed by UV light at doses similar to those used in this study; the absence of ER of UV‐irradiated virus in this study indicates that the mechanism underlying ER is not required for transformation.