bluuebunny/crossref_metadata_2025 huggingface dataset:
TOXICITY, DNA DAMAGE AND INHIBITION OF DNA REPAIR SYNTHESIS IN HUMAN MELANOMA CELLS BY CONCENTRATED SUNLIGHT
Authors: Parsons P. G. , Musk P.
Published: January 2008

A 1 m diameter water lens was used to focus solar radiation, giving an 8‐fold concentration of the total spectrum and a cytocidal flux similar to that of laboratory UV sources. Survival curves for human melanoma cells were similar for sunlight and 254 nm UV, in that Dq, was usually larger than Do. An xeroderma pigmentosum lymphoblastoid line was equally sensitive to both agents and human cell lines sensitive to ionizing radiation (lymphoblastoid lines), crosslinking agents or monofunctional alkylating agents (melanoma lines) had the same 254 nm UV and solar survival responses as appropriate control lines. Two melanoma sublines derived separately by 16 cycles of treatment with sunlight or 254 nm UV were crossresistant to both agents. In one melanoma cell line used for further studies, DNA strand breaks and DNA‐protein crosslinking were induced in melanoma cells by sunlight but pyrimidine dimers (paper chromatography) and DNA interstrand crosslinking (alkaline elution) could not be detected. The solar fiuence response of DNA repair synthesis was much less than that from equitoxic 254 nm UV, reaching a maximum near the Do value and then declining; semiconservative DNA synthesis on the other hand remained high. These effects were not due to changes in thymidine pool sizes. Solar exposure did not have a major effect on 254 nm UV‐induced repair synthesis.
TRIPLET STATES OF CAROTENOIDS BOUND TO REACTION CENTERS OF PHOTOSYNTHETIC BACTERIA: TIME‐RESOLVED RESONANCE RAMAN SPECTROSCOPY
Authors: Lutz Marc , Chinsky Laurent , Turpin Pierre‐Yves
Published: January 2008

Time‐resolved, low‐temperature resonance Raman spectra of triplet states of the carotenoids specifically present in bacterial reaction centers in a strained cis conformation have been obtained, thus demonstrating the possibility of studying intermediate transient states of these structures using resonance Raman spectroscopy. Resonance Raman spectra of triplet cis spheroidene and cis methoxyneurosporene present in reaction centers of Rhodopseudomonas spheroides, (strains 2.4.1. and Ga, respectively) exhibit marked differences with those of triplet, all‐trans carotenoids previously studied in vitro. These differences, together with the frequency shifts measured for the v1 modes, indicate that triplet carotenoids bound to reaction centers retain a cis conformation, and that probably no isomerization occurs to all‐trans carotenoids upon T ← S0 excitation. Pi electron distributions along the polyene backbone are probably less regular in the triplet state than in the singlet ground state, although probably not to the extent suggested by previous theoretical calculations. The apparently anomalous behaviour of the v2 bands of all‐trans carotenoids upon T ← S0 excitation is shown to result largely from the actual complexity of this region of the Raman spectra, together with a weak participation of the vc—–c internal coordinate in the corresponding modes. Finally, the Raman scattering efficiency of triplet spheroidene bound to reaction centers is lower than that of the singlet, ground state form, under equivalent excitation conditions.
ENERGETICS OF DNA REPAIR IN UV‐IRRADIATED PERIPHERAL BLOOD LEUKOCYTES FROM CHRONIC MYELOID LEUKAEMIA PATIENTS
Authors: Verma A. , Sharma R. , Jain V.K.
Published: January 2008

Abstract— The relationship between energy metabolism and UV‐induced (251 nm) DNA repair has been investigated in leukocytes obtained from peripheral blood of chronic myeloid leukaemia patients. Energy supply was modulated by using inhibitors of respiratory (antimvcin‐A) and glycolytic (2‐deoxy‐o‐glucose and other glucose analogues) pathways for adenosine‐triphosphatc (ATP) production. DNA repair was measured by the unscheduled DNA synthesis technique. Parameters of energy metabolism like glucose utilization. lactate production and ATP content of cells. were measured under similar experimental conditions. The observations made indicate the following results: (1) ATP for DNA repair can be supplied by the respiratory and/or by the glycolytic pathway. (2) In the absence of respiration, the rate of glycolysis bears a linear correlation with DNA repair. (3) A minimum threshold rate of ATP‐production is necessary for DNA repair.
MIMICRY OF CAROTENOID FUNCTION IN PHOTOSYNTHESIS: SYNTHESIS AND PHOTOPHYSICAL PROPERTIES OF A CAROTENOPYROPHEOPHORBIDE
Authors: Liddeli Paul A. , Nemeth Gregory A. , Lehman William R. , Joy Anna M. , Moore Ana L. , Bensasson René V. , Moore Thomas A. , Gust Devens
Published: January 2008

Abstract— A new molecule consisting of a carotenoid polyene covalently linked to a pyropheophorbide has been prepared. This molecule exists in solution in an extended conformation with the carotenoid moiety relatively far from the tetrapyrrole π‐electron system. The compound shows negligible antenna function (singlet energy transfer from carotenoid to pyropheophorbide), but substantial photoprotection from singlet oxygen production (due to rapid triplet energy transfer from pyropheophorbide to carotenoid). The photochemical properties of this molecule parallel those of conformationally similar carotenoporphyrins. Thus, carotenoporphyrins appear to be valid synthetic systems for modeling in vivo carotenoid‐chlorophyll interactions.
PERMEABILITY AND STRUCTURAL CHANGES INDUCED BY PHYTOCHROME IN LIPID VESICLES
Authors: Georgevich Gradimir , Roux Stanley J.
Published: January 2008

Abstract— This paper describes a method for rapidly monitoring early changes in electrolyte permeability induced by phytochrome from salt‐loaded liposomes. The method allows for the continuous monitoring of low‐level ion efflux from liposomes by measuring the conductivity of a liposome suspension medium which has osmotic and chemical potentials that promote a slow. passive efflux of the compartmented electrolytes. The addition of the far‐red absorbing form of phytochrome (Pfr) to this system at 20°C immediately produces efflux rates which are 2–3 times greater than if the red‐absorbing form (Pr) is added. This differential effect is not evident at 4°C and varies with the lipid composition of the liposomes. Under conditions in which Pfr induces a 2‐fold greater change in the electrolyte permeability of liposomes than Pr. only about 18% more 125I‐labeled Pfr than 125I‐labeled Pr binds to the liposomes. At equimolar concentrations. the photochromic small peptide of phytochrome (60 000 dalton monomer) and the more native‘large’phytochrome (120000 dalton subunits) induced equivalent changes in the electrolyte permeability of liposomes. No differential leakage of ATP, glucose, or trvpsin from liposomes was observed after Pr and Pfr reacted with vesicles enclosing these substances. The Pfr form of phytochrome promoted greater turbidity in liposome suspensions and a greater degree of aggregation and/or vesiclc fusion than Pr. The kinetics of these changes suggested that they were not the hasis of the differential permeability effects of Pr and Pfr.
ACRYLAMIDE FLUORESCENCE QUENCHING APPLIED TO TYROSYL RESIDUES IN PROTEINS
Authors: Follenius Anny , Gerard Dominique
Published: January 2008

Abstract— The quenching of the tyrosyl emission of proteins which lack tryptophanyl residues was investigated with the neutral quencher, acrylamide. The screening effect of acrylamide at the excitation wavelength, considered until now, as an obstacle to its use in tyrosine quenching studies, was allowed for by means of a theoretical correction. The value of this method was demonstrated by a comparative study using cesium ions as quenchers, which gave similar results on fluorophore location in the protein.
PHOTOBIOLOGICAL ACTIVITY OF MARMESIN (5‐B‐HYDROXYISOPROPYL‐4–5 DIHYDROFUROCOUMARIN) IN CHINESE HAMSTER V79 CELLS
Authors: Uwaifo Anthony O. , Heidelberger Charles
Published: January 2008

Abstract— Marmesin was isolated from the medicinal plant, Afraegle paniculata. Its cytotoxicity and mutagenicity in Chinese hamster V79 cells when sensitized to near ultraviolet (NUV) and long wavelength ultraviolet light or black light (BL) were assayed.

Marmesin was extremely cytotoxic in the dark. This cytotoxicity was photoenhanced in NUV and BL; the photoenhanced lethality being higher in NUV than in BL. The LD50 of marmesin under NUV and BL photosensitization were 0.002 μM and (0.012 μM), respectively. In the absence of NUV and BL, marmesin's LD50 was 0.013 μM. NUV and BL without marmesin were not significantly cytotoxic at the fluence rates of 0.29 W/m2 and 4.2 W/m2, respectively, for up to 20 min. In contrast to the observed high cytotoxicity of marmesin, its mutagenicity at the HGPRT locus (AzGr) was weak. The implication of this result in the high incidence of skin cancer in Nigeria in which A. paniculata is used as a medicinal plant is discussed.
ENERGY TRANSFER BETWEEN THE PRIMARY DONOR BACTERIOCHLOROPHYLL AND CAROTENOIDS IN Rhodopseudomonas sphaeroides
Authors: Frank Harry A. , Machnicki John , Friesner Richard
Published: January 2008

Abstract— The temperature dependencies of the primary donor triplet state spectra are presented for the phorosynthetic bacteria Rhodopseudomonas sphaeroides wild type. GIC and R26. The data suggest that energy transfer from the primary donor triplet state to the reaction center carotenoid is dependent on the type of carotenoid present, reversible in the case of strain GIC, and best understood by a model depicting the kinetic processes that can occur between two potential energy surfaces; one representing the state 3BChl2*Car and the other representing BChl23Car*. Furthermore, it is shown that the onset of spin lattice relaxation in the primary donor triplet is most likely coupled to the same energy vibrational mode as that which promotes triplet state energy transfer from the primary donor to the reaction center carotenoid
EFFECTS OF UV‐B IRRADIATION ON SOROCARP DEVELOPMENT OF Dictyostelium discoideum
Authors: HÄDER Donat‐P.
Published: January 2008

Abstract— The effect of UV‐B irradiation on the development of Dictyostelium discoideum from amoebae to mature sorocarps was studied. Radiation with wavelength ≤ 310 nm was very efficient in retarding and inhibiting the development especially when the organisms were exposed during the first 12 h. At a wavelength of 280 nm an irradiation of 1 h at an irradiance of < 0.2 W m‐2 was sufficient to completely inhibit sorocarp development. The fluence‐dependence shows as well that the development of D. discoideum is a very sensitive system to indicate UV‐B irradiation. Furthermore, since the sorocarp development is concluded within 48 h it can serve as a fast bioassay for hazardous levels of increased UV‐B irradiation which have been predicted as a result of the ozone reduction in the stratosphere due to the manmade production and emission of chlorofluoromethanes.
STREAK CAMERA MEASUREMENT OF TRYPTOPHAN AND RHODAMINE MOTIONS WITH PICOSECOND TIME RESOLUTION
Authors: Nordlund T. M. , Podolski D. A.
Published: January 2008

Abstract—

We have used a signal averaging laser (30 ps pulse)‐streak camera system to measure fluorescence anisotropy decays of dyes in solution and protein tryptophan chromophores with picosecond time resolution. Emission polarization as a function of time can be measured directly and simultaneously for both polarization directions and stored in an optical multichannel analyzer. The corrected anisotropy is computed after background subtraction. Rotations of free dyes in solution (Sulforhodamine 101, tryptophan) and the temperature‐dependent internal motions of human serum albumin (tryptophan emission) are displayed.
PHOTOOXIDATION OF MAGNESIUM TETRAPHENYLPORPHYRIN IN THE PRESENCE OF METHYL VIOLOGEN
Authors: Rieger Anne L. , Edwards John O. , Levey Gerrit
Published: January 2008

Abstract— A study of the photooxidation of magnesium tetraphenylporphyrin by oxygen in methanol with methyl viologen present has been carried out. The reaction was normally followed by the decrease of Soret band absorbance with time. The influences of air, methyl viologen, light wavelength and intensity, presence of ß‐carotene, pH, and MgTPP concentration were investigated. From bulk photolysis experiments, three products have been separated and partially characterized. A mechanism based on superoxide as the dominant oxidant is proposed.
PHOTOPHARMACOLOGY OF THE TRANQUILIZER CHLORDIAZEPOXIDE IN RELATION TO ITS PHOTOTOXICITY
Authors: Bakri† A. , Henegouwen G. M. J. Beijersbergen van , Chanal J. L.
Published: January 2008

Abstract— This study demonstrates that photobiological effects by exogenous molecules are not per se restricted to the skin. As an example the photopharmacology of chlordiazepoxide (e.g. LibriumR) was studied. Rats being exposed to UV‐A after administration of 14C2 labeled chlordiazepoxide (CDZ) showed a marked change in the pattern of urinary metabolites; the quantity of metabolites without N4‐oxide function increased, whereas that of compounds with N4‐oxide function decreased. Covalent binding to organ tissue of especially liver and skin of the irradiated rats was found. This would mean that in the irradiated rats oxaziridines which may also react with tissue of the inner organs are formed from CDZ and its N4‐oxymetabolites.

Further, the combination of light and CDZ leads to a 30% decrease in weight of the liver, indicating liver damage. This is also supported by the percentage of conjugated urinary metabolites being 1.5–2.5 times lower than in the non‐irradiated CDZ‐treated rats, possibly caused by a decrease of enzymatic activity.

The administration of CDZ‐oxaziridine to non‐irradiated rats provoked the same effects, such as a decrease of the weight of the liver comparable to that of irradiated CDZ‐treated rats. On the other hand the combination of light and treatment with N4‐desoxy CDZ did not have any effect, as expected.
PHOTODYNAMIC DAMAGE AND ITS REPAIR IN Vibrio cholerae
Authors: Sil Kaveri , Das Goutam , Das Jyotirmoy
Published: January 2008

Abstract— Repair of photodynamic damage induced by acriflavine and visible light has been examined in three strains of Vibrio cholerae differing in their capabilities to repair ultraviolet (UV) light induced DN A damage. Excision repair deficient wild type cells of strain 154 are more sensitive to photodynamic treatment compared to repair proficient cells of strain 569B. However, no difference in their capabilities to repair of damage following photodynamic treatment can be detected. No single‐strand breaks in the irradiated cell DNA are observed when the cell survival is more than 10%. Single‐strand breaks observed at cell survival less than 5% are not dark repairable even in excision repair proficient wild type cells. Repair of membrane damage can partially account for the recovery observed at low doses. In contrast, radiation‐sensitive mutant 569Bs cells which lack both excision and medium‐dependent dark repair for UV‐lesions are most efficient in repairing damage induced by photodynamic treatment.
RIBOFLAVIN‐PHOTOSENSITIZED OXIDATIVE DEGRADATION OF A VARIETY OF LIGNIN MODEL COMPOUNDS
Authors: Kutsuki Hidetoshi , Enoki Akio , Gold Michael H.
Published: January 2008

Oxidation of several lignin model compounds with alkylated paraphenolic groups by photosensitizing riboflavin (RF). rose bengal (RB) and methylene blue (MB) was examined. Photosensitizing RF cleaved l–(3‘‐4’‐diethoxyphenyl)‐1.3 dihydroxy‐2‐(4‐methoxyphenyl)propane (I). 4‐ethoxy‐3‐methoxyphenylglycerol‐(3‐guaiacyl ether (II) and l‐(4‘‐ethoxy‐3’‐methoxyphenyI)‐1,3 dihydroxypropane (IV) at their respective Cα‐Cβ bonds. Riboflavin also oxidized 3.4‐diethoxy‐benzaldehyde (VI) to the corresponding acid, and hydroxylated the conjugated olefin l‐(4‘‐ethoxy‐3’‐methoxyphenyl)1.2 propene (III) to yield the initial product IV. In contrast, MB and RB hydroxylated III but had no effect on I, II, IV or VI under identical conditions. This suggested RF effected transformations via a hydrogen radical abstraction (Type I) rather than a 1O2 mediated reaction.

To confirm this, the effects of deuterium oxide (D:0) and oxygen pressure on the photosensitizing dye reactions were examined. The effect of D20 on tryptophan (Trp) oxidation and hydroxylation of III by MB and RB was significant, indicating involvement of 1O2. D2O had no significant effect on cleavage of the diarylpropane (I) and the olefin (III) by RF, indicating these reactions did not proceed by a Type II mechanism. While O2 pressure effect on Trp oxidation by MB was insignificant, it had a large negative effect on cleavage of I by RF. These results, coupled with the relatively slow oxidation rate of Trp by RF. indicate that photosensitizing RF produces 1O2 inefficiently and is not effecting oxidation of these lignin model compounds via a Type II mechanism.
USE OF THE DYE HOECHST 33258 TO INCREASE THE PHOTOSENSITIVITY OF BROMODEOXYURIDINE‐CONTAINING CELLULAR SLIME MOLDS
Authors: Graetzer R. , Deering R. A.
Published: January 2008

The photosensitivity of amoebae of Dictyostelium discoideum to near‐ultraviolet light (near‐UV; 365 nm peak) was investigated following growth in 5‐bromodeoxyuridine (BrdUrd) and treatment with the dye Hoeschst 33258. Cell killing was studied as a function of dye‐treatment time and concentration, and BrdUrd incorporation time and concentration. For example, cells grown for 13 h in 50 μg BrdUrd/ml and then treated for 1 h in 10 μg dye/ml were reduced to 10% survival by a near‐UV exposure of 0.8 min. Combinations of any two of the three factors (BrdUrd, dye, near‐UV) were ineffective for killing. The sensitivity of the cells to near‐UV decreased rapidly as the holding time between the end of the dye treatment and the start of the UV exposure was increased.
PHOTOMOVEMENT RESPONSES OF THE HETEROTRICHOUS CILIATE Blepharisma Japonicum
Authors: Kraml Manfred , Marwan Wolfgang
Published: January 2008

Light‐induced movement responses of the heterotrichous ciliate Blepharisma japonicum were studied by physiological experiments. Two photosensory responses could be identified. A step‐up photophobic response is observed as a very rapid backward movement. Microbeam irradiations of individual cells showed that only the anterior part of the ciliate is able to perceive the light stimulus that mediates the phobic reaction. The action spectrum peaks at approximately 400 nm, which indicates that a blue light receptor is involved.

Positive photokinesis of Blepharisma could be shown as a forward movement that is accelerated by increasing the applied photon fluence rate. The steady state level of the velocity depends highly on wavelength and photon fluence rate of the actinic light. After specific inhibition of the phobic reaction bv 1 m/W NH4+, photokinesis can be induced by microbeam irradiation at any part of the cell.

We isolated two main pigments by thin layer chromatography and characterized them as hypericin‐like compounds: a red pigment that is obviously responsible for the red color of the ciliates (= blepharismin). and a yellow one with maximal absorption near 420 nm. The possible photoreceptor functions of these pigments are discussed.

We could not find in Blepharisma a distinct phototactic behavior which is so typical for the related ciliate Stentor.
ASSOCIATION OF CHLOROPHYLL WITH AMIDES ON PLASTICIZED POLYETHYLENE PARTICLES–III. UNUSUAL SPECTRA OF CHLOROPHYLL a WITH N‐METHYLMYRISTAMIDE*
Authors: Kusumoto Y. , Senthilathipan V. , Seely G.R.
Published: January 2008

—The absorption spectrum of chlorophyll a, adsorbed with the amphiphilic amide, N‐methylmyristamide. to particles of polyethylene swollen with tetradecane, is unusual in that the red band apparently consists of three main components, which by Gaussian deconvolution are located at 664.5, 678 and 687 nm. The last is very narrow, with a band width of only 5‐6 nm at half maximum. At low amide concentration, the 744 nm band of chlorophyll hydrate is also observed. Room temperature fluorescence is weak, and indistinctly resolved into bands. However, on gradual cooling to 80 K, the fluorescence intensifies greatly and becomes resolvable into at least eight bands. The circular dichroism spectrum of the red band region shows optical rotatory strength in two narrow bands at 677 and 686 nm which is enormous, compared to that of monomeric chlorophyll or even the 744 nm hydrate. It is suggested that cyclic oligomer structures, in which adjacent chlorophylls are linked through the amide group of N‐methylmyristamide, might be responsible for the spectral phenomena. Unsubstituted myristamide and N.N‐dimethylmyristamide do not produce these narrow‐banded phenomena with chlorophyll at all.
UROCANIC ACID PHOTOBIOLOGY. PHOTOCYCLOADDITION OF N,N‐DIMETHYLTHYMINE TO UROCANIC ACID*
Authors: Morrison H. , Bernasconi C. , Pandey G.
Published: January 2008

Abstract— Photolysis of N,N‐dimethylthymine (DMT) and urocanic acid (UA) gives rise to two isolable cyclobutane adducts. N,N‐dimethylthymine also photosensitizes UA E/Z isomerization. Neither phenomenon is affected by a triplet quencher, and 1DMT* is proposed as the likely reactive species. If so, prior complexation of DMT and UA would be necessary in order for their interaction to be competitive with DMT radiationless decay. These observations are potentially related to the effect of UA on viral DNA described in the following paper.
FLUORESCENCE OF BACTERIORHODOPSIN UNDER SUBPICOSECOND LIGHT EXCITATION
Authors: Sharkov A. V. , Matveetz Yu. A. , Chekalin S. V. , Konyashchenko A. V. , Brekhov O. M. , Rootskoy B. Yu.
Published: January 2008

Abstract— A streak camera detection technique has been used to record the fluorescence of bacteriorhodopsin at room temperature induced by single subpicosecond light pulses. The fluorescence lifetime of bacteriorhodopsin has been found to be less than 2 ps.
XERODERMA PIGMENTOSUM FIBROBLASTS INCLUDING CELLS FROM XP VARIANTS ARE ABNORMALLY SENSITIVE TO THE MUTAGENIC AND CYTOTOXIC ACTION OF BROAD SPECTRUM SIMULATED SUNLIGHT
Authors: PATTON JOE DALE , ROWAN LAURIE A. , MENDRALA ALAN L. , HOWELL JEFFERY N. , MAHERE VERONICA M. , MCCORMICK J. JUSTIN
Published: January 2008

Abstract— The cytotoxic and mutagenic effects of broad spectrum simulated sunlight, as delivered by a Westinghouse Sun Lamp FS 20 filtered to eliminate wavelengths below 290 nm, were determined in diploid human skin fibroblasts which differ in their ability to repair pyrimidine dimers, and compared with results obtained with UV 254 nm radiation. The cell strains tested included normal fibroblasts; excision repair‐deficient xeroderma pigmentosum (XP) cells from patients XP12BE (complementation group A). XP7BE (group D). and XP2BI (group G): and an XP variant patient (XP4BE) whose cells excise pyrimidinc dimers at a normal rate, but exhibit abnormal replication of DNA containing unexcised lesions. Cytotoxicity was assayed from loss of colony‐forming ability. The group A cells were most sensitive to the killing effect of the Sun Lamp; the group D and G cells were slightly less sensitive; the XP variant cells showed intermediate sensitivity; and normal cells were most resistant. When the Sun Lamp survival curves for the group A, group D, the XP variant and normal cells were compared with their respective UV 254 nm survival curves, the relationships between the strains were virtually identical (i. e. the curves were related by a constant fluence modification factor). suggesting a common lesion for cell killing. The marker for mutagenesis was resistance to 6‐thioguanine. The group A XP cells proved most sensitive to mutations induced by the simulated sunlight: the variant cells were intermediate; and the normal cells were the most resistant. Again, when the curves for mutations induced in these cell strains by simulated sunlight were compared with their respective 254 nm UV mutation curves, these were related by a constant fluence modification factor. suggesting a common lesion for mutagenesis. These results. taken together with published data indicating that at equicytotoxic levels of UV254 nm radiation and the filtered Sun Lamp. the number of pyrimidine dimers in the DNA of XP12BE cells was equal. support the hypothesis that the dimer is the lesion principally involved in both effects. Our data also support the hypothesis that mutations are involved in the sunlight‐induced skin cancer of XP patients.
FLUORESCENCE PROPERTIES OF ETHENOTHIAMINE*
Authors: WOLFBEIS OTTO S. , URAY GEORG
Published: January 2008

Abstract— The absorption and fluorescence properties of ethenothiamine in neutral and acidic solution are reported, and some are found to be in contradiction to previous findings. The low fluorescence quantum yields of ethenothiamine make it a poor substitute for the vitamin in biological systems.
THE PHOTOCHEMICAL INTERACTION BETWEEN THE TRIPLET STATE OF 8‐METHOXYPSORALEN AND THE MELANIN PRECURSORL–3, 4 DIHYDROXYPHENYLALANINE
Authors: CRAW M. , CHEDEKEL M. R. , TRUSCOTT T. G. , LAND E. J.
Published: January 2008

Abstract— The photochemical interaction between 8‐methoxypsoralen (8‐MOP) and the melanin precursorL–3,4‐dihydroxyphenylalanine(dopaH2) has been studied using laser flash photolysis. Triplet excited 8‐MOP was thus found to abstract electrons from dopaH2 (k∼ 2 × 109 dm3 mol‐1 s‐1) to form semireduced 8‐MOP and semioxidised dopaH2.The technique of pulse radiolysis was used to establish separately the spectra of (a) the semi‐reduced form of 8‐MOP at pH 6.5 and (b) the semioxidised forms of dopaH2 at pH 6.5, 5.8, 4.6 and 3.3. The corresponding λmax and extinction coefficients found were: for 8‐MOP at pH 6.5, λmax= 350 nm (= 9050 dm3 mol‐1 cm‐1); for dopa at pH 6.5, λmax= 305 nm (ε= 12000 dm3 mol‐1 cm‐1) and for dopaH at pH 3.3, λ= 305 nm (ε= 5900 dm3 mol‐1 cm‐1).
PHOTOACTIVITY OF TRANSIENT INTERMEDIATES IN THE PATHWAY FROM THE RED‐ABSORBING TO THE FAR‐RED‐ABSORBING FORM OF Avena PHYTOCHROME AS OBSERVED BY A DOUBLE‐FLASH TRANSIENT‐SPECTRUM ANALYZER
Authors: PRATT LEE H. , INOUE Y. , FURUYA M.
Published: January 2008

Abstract— Phototransformation from the red‐absorbing form of phytochrome (Pr) to the far‐red‐absorbing form occurs via at least two reaction stages. We report here on the photoactivity of the intermediates present during these two stages, as detected with 114/118‐kdalton Avena phytochrome by a transient spectrum analyzer with two actinic lasers of microsecond duration. Flash activation of intermediates present during the first stage results in their photoconversion back to Pr within the time resolution provided by the analyzer, which is 10 μs. Since these intermediates are present within 60 ns of excitation of Pr (Cordonnier et al., 1981), a single flash of ms duration as used here should yield a photostationary equilibrium between them and Pr. The proportion of Pr converted to intermediates by a single saturating flash is estimated to be about 30%. Flash activation of intermediates present during the second stage converts them to another transient intermediate stage, which decays thermally to Pr within 2 ms.
FORMATION OF PYRIMIDINE DIMERS IN SIMIAN VIRUS 40 CHROMOSOMES AND DNA in vitro: EFFECTS OF SALT
Authors: Edenberg HOWARD J.
Published: January 2008

Abstract— Simian virus 40 chromosomes were used to determine whether packaging of DNA into chromatin affected the yield of cyclobutane pyrimidine dimers introduced by ultraviolet light (254 nm). SV40 chromatin and purified SV40 DNA (radioactively labeled with different isotopes) were mixed and irradiated in vitro. The proteins were extracted and pyrimidine dimers detected as sites sensitive to the UV‐endonuclease encoded by bacteriophage T4. When irradiation was carried out in the presence of at least 0.05 M NaCl the same number of dimers were formed in chromatin as in free DNA. Irradiation in the absence of NaCl, however, reduced the relative yield of dimers in chromatin to 89% of that in free DNA. Different methods of chromatin preparation did not influence these results.
A LASER FLASH PHOTOLYSIS AND PULSE RADIOLYSIS STUDY OF AMILORIDE IN AQUEOUS AND ALCOHOLIC SOLUTION
Authors: Hamoudi H. I. , Heelis P. F. , Jones R. A. , Navaratnam S. , Parsons B. J. , Phillips G. O. , Vandenburg M. J. , Currie W. J. C.
Published: January 2008

Abstract Laser flash photolysis and pulse radiolysis have been carried out on the diuretic drug amiloride. The primary photochemical processes in aqueous solution were found to be photoionisation and triplet formation. Photoionisation was found to occur by a biphotonic process for 265 nm excitation but by a monophotonic process for excitation at 353 nm. The spectral properties of the resulting cation radical of amiloride were determined by pulse radiolysis using one electron oxidation by the radical anion Br2·¯ Photoexcitation of amiloride in isopropanol did not result in photoionisation but instead a semireduced radical of amiloride was observed. The spectral properties of the semireduced radical of amiloride were determined using one electron reduction by the CO2·¯ radical.
WAVELENGTH DEPENDENCE OF INACTIVATION AND MUTATION INDUCTION TO 6‐THIOGUANINE‐RESISTANCE IN V79 CHINESE HAMSTER FIBROBLASTS
Authors: Zölzer F. , Kiefer J.
Published: January 2008

Abstract The wavelength dependence of inactivation and mutation induction to 6‐thioguanine‐resistance in the range between 254 and 313 nm was investigated in V79 Chinese hamster fibroblasts. The action spectra agreed quite well with those reported by others for different effects on mammalian cells. There was no distinct difference between the wavelength dependencies of inactivation and mutation induction; the ratio of mutagenic to lethal action remained constant.
THE PHOTOLYSIS OF PENICILLAMINE DISULPHIDE IN ACIDIC AQUEOUS SOLUTION
Authors: Grant D. W. , Stewart J. H.
Published: January 2008

Quantum yields of penicillamine (PenSH), valine (PenH), β‐hydroxyvalinc (PenOH), penicillamine trisulphide (PenSSSPen). ammonia, a keto acid and penicillamine sulphinic acid (PenSO2H) were determined in the 254 nm‐photolysis of aqueous solutions of penicillamine disulphide (PenSSPen) at pH 1.8. Oxygenation of the PenSSPen solutions prior to irradiation had no effect on the yield of PenSH, but increased the yields of PenOH, ammonia, keto acid and oxyacids of sulphur and decreased the yields of PenSSSPen and PenH. Evidence was obtained that deamination of PenSSPen is initiated by Pen. radicals in deoxygenated and PenO2 radicals in oxygenated solutions. Flash photolysis was used to detect the PenSS. radical in irradiated PenSSPen solutions and to study its rate of decay. Comparison of the results of the investigation with those published for cystine indicate that substitution of the methylene hydrogens in cystine by methyl groups leads to a substantial increase in the importance of photochemical C‐S bond fission.
THE PHOTOTOXICITY OF 2,5‐DIPHENYLOXAZOLE (POP) AND 1,4‐BIS(5‐PHENYLOXAZOL‐2‐YL)BENZENE (POPOP)
Authors: Kagan Jacques , Kolyvas Chris P. , Jaworski Jeffery A. , Kagan Edgard D. , Kagan Isabelle A. , Zang Li‐Hsin
Published: January 2008

Abstract 2,5‐Diphenyloxazole (POP) is widely used for the determination of radioactivity by scintillation counting. It has been found to be phototoxic to the yeasts Saccharomyces cerevisiae and Candida utilis, to the first instar larvae of the mosquito Aedes aegypti, to the crustaceans Daphnia magna and Artemia salida, as well as to the eggs of Drosophila melanogaster. The related molecule 1,4‐bis(5‐phenyloxazol‐2‐yl)benzene (POPOP) is also phototoxic, but to a lesser degree. Both POP and POPOP can sensitize the formation of singlet oxygen.
QUENCHING OF THE EXCITED STATES OF 2‐PHENYLBENZOXAZOLE BY AZIDE ANION. FLUORESCENCE AND ESR STUDY
Authors: Reszka K. , Hall R. D. , Chignell C. F.
Published: January 2008

Electron spin resonance, spin‐trapping and fluorescence techniques demonstrate that 2‐phenylbenzoxazole (P) participates in photo‐induced reactions with alcohols and electron donors like the azide ion. Irradiation of Pat 300 nm in deaerated ethanol produces ethoxyl and hydroxyethyl radicals which can be detected with the spin trap, 5,5‐dimethyl‐l‐pyrroline‐l‐oxide (DMPO). However, irradiation of P in the presence of N‐3 leads to the appearance of the azide radical, N‐3, which also reacts with DMPO. Studies with the nitroxyl radical, 2,2,6,6‐tetramethylpiperidine‐l‐oxyl (TEMPO), suggest that electron transfer from the azide anion to an excited state of P yields the semi‐reduced sensitizer, P‐, which in turn reacts with TEMPO. The effect of sodium azide upon the fluorescence intensity and lifetime of P in aqueous ethanol has also been studied.
INDUCTION OF PHOTOPRODUCTS IN SYNTHETIC POLYNUCLEOTIDES BY FAR AND NEAR ULTRAVIOLET RADIATION
Authors: L. Mitchell David , Clarkson Judith M.
Published: January 2008

Single and double‐stranded polynucleotides of thymine and cytosine have been used to analyse the photoproducts produced by irradiation with far or near UV light. Reversed‐phase high performance liquid chromatography was used to detect and quantify cyclobutane dimers and Pyr(6–4)Pyo adducts produced by 254 nm. At 320 nm 10‐times less Thy(5–6)Thy dimers and one half the number of Cyt(5–6)Cyt dimers were induced; no Pyr(6–4)Pyo adducts were evident.

HPLC has recently been applied to the isolation and characterization of various nucleic acid substituents and their UV‐photoproducts. The relative retention times of pyrimidines and their UV photoproducts on HPLC reflect differences in the hydrophobicity of the compounds being separated. Hence, the more hydrophobic (less polar) a compound is, the greater its capacity to bind to the column and the greater its retention time; for T o T, C<>T and C<>C dimers this difference may result from variations in the number of methyl moieties (Cadet et al., 1983). The retention time of the compound also depends on its stereochemistry. Separation of the four stereoisomers of T<>T by HPLC shows that compounds which are molecular equivalents can be more or less accessible to the non‐polar stationary phase depending on their conformation (Cadet, 1980). The relatively long retention times of the bipyrimidine photoadducts suggest a structural configuration which allows greater access to the hydrophobic moieties of the molecule.

It is intriguing to consider that this difference in conformation may also be reflected in DNA–protein interactions such as binding by UV‐endonucleases or antibodies directed against UV photodamage. Proteins can be used as sensitive probes for photoproduct induction and repair but an accurate evaluation of their specificity is required. It was the intent of this paper not only to compare the induction parameters for various dimers in pyrimidine homo‐polymers but to provide controlled substrates which can be used to define the relative binding efficiencies of repair enzymes and antibodies for different types of photoproducts.
DETECTION OF DNA‐PSORALEN PHOTOADDUCTS in situ
Authors: ZAREBSKA ZOFIA , JARZABEK‐CHORZELSKA MARIA , RZȨSA GENOWEFA , GLIŃSKI WIESLAW , PAWIŃKA MARIA , CHORZELSKI TADEUSZ , JABLOŃKA STEFANIA
Published: January 2008

Abstract— An immunological method, with the use of specific immune serum, has been developed for detection of 8‐methoxypsoralen (8‐MOP) photoadducts to DNA, formed in situ in cell nuclei, after combined treatment with 8MOP and UV‐A irradiation (Zarçbska et al., 1978). Lymphocytes fixed on slides or in suspension, and cryostat sections of different mammalian tissues, served as antigenic substrate, after treatment with 8‐MOP and UV‐A in vitro. Specific fluorescence in these substrates was detected in the nuclei after treatment with 30 ˜ 140 kJ/m2 UV‐A in the presence of 0.1‐0.3 μg/cm2 8‐MOP. PHA‐stimulated‐lymphocytes appeared to be the most sensitive substrate.

However, hairless mice treated with high doses of UV‐A in vivo, 70 ˜ 360 kJ/m2 did not reveal a specific fluorescence of epidermal nuclei, unless a high local concentration of 8‐MOP was attained.

The apparent discrepancy in the level of photoadduct detection between the in vitro and in vivo treated specimens was explained by the low number of DNA‐8‐MOP‐photoadducts formed in vivo under these experimental conditions. The relevance of these findings to the role of DNA‐8‐MOP‐photoadducts formed during PUVA photochemotherapy is discussed.
TWENTY‐TWO CARBON HOMOLOGUE OF 11‐CIS RETINAL. PHOTOPHYSICAL AND PHOTOCHEMICAL PROPERTIES
Authors: DAS PARITOSH K. , BECKER RALPH S.
Published: January 2008

Abstract— Results concerning absorption‐emission spectra and fluorescence quantum yields at 77 and 298K. triplet absorption spectra, and quantum yields of intersystem crossing and photoisomerization at 298 K, are presented for 11‐cisβ‐apo‐14′‐carotenal (C22‐Ald), the immediate higher homologue of 11‐cis retinal. The absorption spectra are characterized by two band‐systems with maxima at 390–400 and 270–280 nm, respectively. Upon cooling from 298 to 77 K, the intensities of these two band‐systems undergo changes in opposite directions indicating 12‐s‐cis: 12‐s‐trans conformational changes. No intermediate band‐system analogous to the one located at 270–310 nm in cis retinals is observed for 11‐cis C22‐Ald. In nonpolar hydrocarbon solvents (e. g. cyclohexane) at room temperature, quantum yields of fluorescence (0.01), intersystem crossing (0.6) and photoisomerization (0.4) are all quite pronounced. The photophysical and photochemical properties of 11‐cis C22‐Ald are discussed in the light of similarities and dissimilarities with those of all‐trans C22‐Ald and 11‐cis retinal under comparable conditions.
TRANSIENT PHOTOCHEMISTRY OF NEUTRAL RED
Authors: MARKS G. T. , LEE E. D. , AIKENS D. A. , RICHTOL H. H.
Published: January 2008

Abstract— Flash photolysis of neutral red between pH 1.3 and pH 11 yields the triplet species 3DH2+23DH+ and 3D. Both 3DH2+2 and 3D exhibit first order decay with rate constants of 1.6 ± 0.3 × 104 s‐1 but 3DH+ decays within the lifetime of the flash. Over the entire pH range, ascorbic acid quenches the triplet, forming the semireduced radicals DH3+2 DH2+ and DH, all of which exhibit second order decay with k= 1.8 ± 0.4 ± 108M‐1s‐1 most probably by recombination with semioxidized ascorbic acid. The dependence of the rate of decay of radical neutral red on the identity of reversible reductants supports the back‐electron transfer mechanism, as does digital simulation of complex radical disproportionation schemes. In contrast to the efficient reduction of triplet neutral red by ascorbic acid, its reduction by EDTA is quite inefficient.
THE Ion GENE AND PHOTOPROTECTION IN Escherichia coli K‐12
Authors: WAKSMAN GABRIEL , THOMAS GILLES , FAVRE ALAIN
Published: January 2008

Abstract— Photoprotection i. e. the increased resistance of the cells preilluminated with near ultraviolet light (300–380 nm) to the lethal action of 254 nm radiations is observed in wild‐type Escherichia coli B cells (which exhibits the Fil phenotype) but requires either an integrated prophage or a recA mutation to be detected in E. coli K12 strains. Here we have demonstrated that significant photoprotection occurs in an E. coli K12 recA+ cell containing the Ion allele which is responsible for filamentous growth (Fil phenotype) after 254 nm irradiation. The Fil phenotype can be suppressed by the sfiA of sfiB suppressor genes. Since the E. coli K12 recA+Ion sfiB strain exhibits no more photoprotection, these data support the conclusion that in Ion strains photoprotection is due to the abolition of the 254 nm induced filamentation by the near ultraviolet treatment. In addition, we show here that near ultraviolet illumination of the cells leads to a severe restriction of the bulk protein synthesis, as well as of the inducibility of β‐galactosidase and tryptophanase. These effects are observed only in nuv+ cells that contains 4‐thiouridine the chromophore responsible for photoprotection. We propose that in Ion (lysogenic) strains, photoprotection is due to prevention of the SOS response. During the growth lag, the low residual level of protein synthesis does not allow the induction of the SOS response and accordingly prevents filamentation (the lytic cycle). Concomitantly the SOS triggering signals are eliminated via DNA repair.
LIGHT ACTIVATION OF A COMPLEX MIXTURE: EFFECTS OF UV EXCISION REPAIR ON THE MODULATION OF GENOTOXIC AND MOLECULAR EVENTS IN CHINESE HAMSTER CELLS
Authors: OKINAKA R. T. , BINGHAM J. M. , MACINNES M. A. , STRNISTE G. F.
Published: January 2008

Abstract— An aqueous effluent produced during the retorting of oil shale has been shown to induce a significant genotoxic response in cultured Chinese hamster (CHO) cells following activation by near ultraviolet light (UVA). In this report the light‐activated responses induced by this complex mixture were compared between two DNA excision repair deficient mutants and their parental strain, CHO‐AA8‐4. The mutants, UV‐5 and UV‐135, were hypersensitive to both the cytotoxic and mutagenic effects of concurrent exposures to the retort process water and UVA. Repair proficiency appeared to render AA8‐4 relatively insensitive to low doses of UVA treatment, whereas in the two mutants a linear dose‐response in the induction of 6‐thioguanine resistant (6TG®) mutations was observed even at the lower UVA doses examined. Filter DNA alkaline elution methods were utilized to demonstrate that both single‐strand breaks and DNA‐DNA interstrand crosslinks were induced in CHO DNA following process water and UVA treatment. Results were also obtained which indicated that the inability to repair DNA‐DNA crosslinks contributed significantly to the hypersensitive response seen in the excision repair mutants following the photoactivation of this complex mixture.
COMPARISON OF EFFECTS OF UVA, UVB AND UVC ON GROWTH AND VIABILITY OF MITOGEN‐STIMULATED HUMAN PERIPHERAL BLOOD CELLS
Authors: PRETELL JUDITH O. , WIMBERLY JOANNE , MCAULIFFE DANIEL J. , PARRISH JOHN A.
Published: January 2008

Abstract— Peripheral blood mononuclear cells were irradiated with UVA, UVB or UVC. The highest exposure dose used in each waveband reduced the number of viable cells to one‐third the control cell population after 3 days in culture. Exposure of these cells to half as much UV from each waveband resulted in an equivalent or greater degree of inhibition of their proliferative response to mitogen as measured by lymphoblast transformation, [3H]‐thymidine uptake and viable cell number on day 3 in culture. The pattern of inhibition was distinct for each waveband. UVA interfered with blastogenesis on the first 2 days of culture at doses which had considerably less effect on viable cell number. UVA also depressed the first round of DNA synthesis, which was detectable on the second day of culture. By day 3 in culture, however, the UVA‐induced reduction in both the number of lymphoblasts and the uptake of [3H]‐thymidine was a direct reflection of reduced numbers of viable cells. UVB did not interfere with blastogenesis in mitogen‐stimulated cultures to the same degree as did UVA. Only the highest dose of UVB depressed blast transformation more than viable cell number on day 1; by day 2 lower doses were also inhibitory. In contrast UVC had little effect on blastogenesis at any time; a reduced number of lymphoblasts observed on days 2 and 3 in culture was a direct reflection of a reduced number of viable cells rather than a reduced percent of these cells undergoing blast transformation. As with UVA‐irradiated, mitogen‐stimulated cells, [3H]‐thymidine uptake was also depressed in both UVB and UVC irradiated, mitogen‐stimulated cells on day 2. However, only UVB continued to depress DNA synthesis more than viable cell number after 3 days of culture. These results suggest that UVA, UVB and UVC may interfere with any one or more of the signals involved in the response to mitogen, be they the recognition of mitogen by T cells or accessory cells, the transformation of lymphocytes into lymphoblasts or the activation of lymphoblasts to synthesize DNA.
THE ORIENTATION OF THE REACTION CENTER CAROTENOID TRIPLET STATE MAGNETIC AXES IN CHROMATOPHORES OF Rhodopseudomonas sphaeroides WILD TYPE
Authors: FRANK HARRY A. , MACHNICKI JOHN , TOPPO PAUL
Published: January 2008

Abstract— The orientation of the principal magnetic axes of the reaction center carotenoid from Rps. sphaeroides wild type is presented. The parameters needed to simulate the observed carotenoid triplet state spectra indicate that the carotenoid adopts a planar structure within the reaction center. A high degree of geometrical and structural specificity is shown to exist for this carotenoid molecule.
THE ROLE OF ARGININES 82 AND 227 IN THE BACTERIORHODOPSIN PROTON PUMP
Authors: Drachev L. A. , Kaulen A. D. , Khorana H. G. , Moci T. , Postanogova N. V. , Skulachev V. P. , Stern L. J.
Published: January 2008

Abstract

Arginine residues 82 and 227 in bacteriorhodopsin were replaced by glutamine residues, using the site‐directed mutagenesis techniques. Mutant bacteriorhodopsins were found to be competent in formation and decomposition of the photocycle M412 intermediate as well as in generation of photoelectric potential provided that pH of the medium is sufficiently high. Lowering of pH results in transition of bacteriorhodopsin into a blue acidic form which cannot produce M412 and photo‐potential. The pK values of these transitions for Arg‐227 → Gln and Arg‐82 → Gln mutants are shifted correspondently for 1 and 4 pH units to a higher pH region in comparison with native bacteriorhodopsin. The rate of the M412 formation in both mutants was similar to that in the native protein. As to M412 decay, it is much slower in Arg‐227 → Gln mutant than in native and Arg‐82 → Gln bacteriorhodopsins. In all cases, the decay depends only slightly upon pH. It is concluded that Arg‐82 is involved in maintenance of a bacteriorhodopsin structure that is resistant to the pH decrease down to 4 whereas Arg‐227 is required first of all for the process of Schiff base reprotonation.
MUTAGENIC and RECOMBINOGENIC EFFECTS OF DNA CROSS‐LINKS INDUCED IN YEAST BY 8‐METHOXYPSORALEN PHOTOADDITION
Authors: Cassier C. , Chanet R. , Moustacchi E.
Published: January 2008

Abstract— A re‐irradiation with a saturating dose of UVA after pretreatment with 8‐methoxypsoralen (8‐MOP) plus low doses of UVA and removal of unbound 8‐MOP, induces an increase in frequencies of mutants and recombinants in repair‐proficient Saccharomyces cerevisiae. The magnitude of this increase is proportional to the first UVA dose. An incubation of cells between the two UVA doses allowing the repair of monoadducts produced by the first dose abolishes the enhancement in frequencies of mutants and recombinants. It is concluded that in yeast cross‐links are not solely lethal but could constitute, in repair proficient cells, premutagenic and prerecombinogenic lesions.
INTERDEPENDENCE OF FLUENCE, DRUG DOSE and OXYGEN ON HEMATOPORPHYRIN DERIVATIVE INDUCED PHOTOSENSITIZATION OF TUMOR MITOCHONDRIA
Authors: Gibson Scott L. , Hilf Russell
Published: January 2008

Abstract— Studies were conducted to assess the interdependence of three discrete parameters known to influence hematoporphyrin derivative (Hpd)‐induced photosensitization. The effects of fiuence, drug dose and oxygen environment were examined for their role in causing an inhibition of the activity of mitochondrial cytochrome c oxidase. Experiments were performed on R3230AC mammary tumor mitochondria in vitro and on mitochondria isolated from tumors of animals pre‐treated with Hpd in vivo. Inhibition of cytochrome c oxidase activity was observed to be directly proportional to total energy density. Photosensitization was dependent on oxygen concentration, with total energy density dependent photosensitization being diminished in environments containing less than 5% oxygen. At 1% oxygen environments, photosensitization was significantly impaired and demonstrated no drug‐dose relationship. These results suggest that tissue oxygen concentration may represent a critical factor for the therapeutic usefulness of Hpd photodynamic therapy in treatment of cancer.