bluuebunny/crossref_metadata_2025 huggingface dataset:
MUTATIONAL INTERACTIONS BETWEEN NEAR‐UV RADIATION AND DNA DAMAGING AGENTS IN Escherichia coli: THE ROLE OF NEAR‐UV‐INDUCED MODIFICATIONS IN GROWTH AND MACROMOLECULAR SYNTHESIS
Authors: Moraes E. C. De , Tyrrell R. M.
Published: January 2008

Abstract— The mutational interactions between near‐ultraviolet (near‐UV, 334 nm, 365 nm) radiation and DNA damaging agents (far‐UV (254 nm) and ethyl‐methanesulphonate (EMS)) were studied in strains of Escherichia coli B/r trp thy with different susceptibilities to near‐UV‐induced growth delay (wild‐type, rel and srd). Far‐UV induced reversion to tryptophan independence is reduced while forward mutation to streptomycin is enhanced by prior exposure of the rel+ srd+ strains to near‐UV radiation. The observed interactions are reduced (rel) or absent (srd) in the two mutant strains as are the corresponding growth and macromolecular synthesis delays normally observed after near‐UV treatment. Quantitatively, the degree of interaction induced by near‐UV pre‐treatment correlates closely with the degree of protein synthesis inhibition. We propose a mechanism for the contrasting interactions at the two genetic loci based on the different pathways by which pre‐mutagenic lesions may be processed. The primary chromophore for the mutational interactions would appear to be 4‐thiouracil‐containing transfer RNA.
A NON‐TYPICAL CYCLOBUTANE DIMER PHOTOPROD‡ FROM 5‐ETHYLOROTATE
Authors: KULIKOWSKA EWA , MIURA IWAO , NAKANISHI KOJI , ZAWADZKI ZBIGNIEW , SHUGAR DAVID
Published: January 2008

Abstract— One of the two major photoproducts resulting from the irradiation of 5‐ethylorotate in neutral aqueous medium has been identified as an unusual cyclobutane photodimer formed from the 5.6 bond of the parent 5‐ethylorotate and the exocyclicC–5‐Cx bond of 5‐ethylidenehydroorotate the initial photoproduct of 5‐ethylorotate [Kulikowska et al., Z. Naturforsch. 31c, 514 (1976)]. Irradiation at 254 nm in neutral aqueous medium causes the heterodimer to photodissociate to the two parent monomers with a quantum yield of 0.28. The heterodimer also hydrolyzes to the parent monomers in aqueous base at room temperature or by heating in the solid state. A scheme for the major photochemical transformation of 5‐ethylorotate is presented.
PHOTOREACTIVATION OF ICR 2A FROG CELLS EXPOSED TO SOLAR UV WAVELENGTHS
Authors: Rosenstein Barry S.
Published: January 2008

Abstract Exposure of ICR 2A frog cells to photoreactivating light (PRL) following irradiation with a fluorescent sun lamp (FSL) resulted in an enhancement in survival compared with FSL‐irradiated cells incubated in the dark. Hence, pyrimidine dimers played a role in the killing of cells exposed to the UV produced by this source. However, when the light was passed through a series of filters to remove increasing segments of the wavelength region shorter than 320 nm, the effect of the PRL progressively decreased, demonstrating that non‐dimer photoproducts play an increasingly important role in the killing of cells exposed to wavelengths approaching 320 nm. Cells were also exposed to 313 nm UV produced by a monochromator and it was found, once again, that the effectiveness of the PRL treatment depended on the filter the beam was passed through. These results indicate that for both FSL‐produced UV and 313 nm UV emitted by a monochromator, that the critical photoproducts induced within the cell depend on the filter used in conjunction with the UV source.
ULTRAVIOLET RADIATION INHIBITS BOTH ACCESSORY CELL AND RESPONDER T CELL FUNCTION IN THE PROLIFERATIVE RESPONSE TO HAPTENATED‐SELF
Authors: Pretell Judith O. , McAuliffe Daniel J. , Parrish John A.
Published: January 2008

Ultraviolet‐irradiated, hapten‐conjugated stimulator cells were unable to generate a proliferative response in unirradiated autologous T cells. The inhibition of the hapten‐specific response was found to depend on both the dose and waveband of UV radiation used as well as the timing of irradiation with regard to haptenation. UVC (254 nm) was 10‐fold more effective in eliminating the response than UVB (290–320 nm) which in turn was 104‐fold more effective than UVA (320–400 nm) with regard to the amount of incident energy required. Incident doses of UV lower than those within each waveband which virtually eliminated the response resulted in partial inhibition. This inhibition was significantly greater if UV radiation followed haptenation rather than preceding it, suggesting that UV radiation may have caused some loss of antigenicity. The interaction of UV radiation with hapten did not lead to enhanced phototoxicity; survival curves of viable cells placed in culture after the same dose and waveband of UV, either before, after or without haptenation, were similar. Independent experiments revealed that irradiation of the T cells with lower doses of UV than those required to reduce the stimulation 50% with irradiated haptenated stimulator cells, was itself directly inhibitory of their response to unirradiated, TNP‐conjugated adherent cells.
THE UV PROTEIN FLUORESCENCE OF PURPLE MEMBRANE AND ITS APOMEMBRANE
Authors: Acuña A. U. , González J. , Lillo M. P. , Otón J. M.
Published: January 2008

The ultraviolet fluorescence of the purple membrane of H. halobium and its apomembrane was characterized by measuring emission spectra, polarization, decay lifetimes and the changes induced by pH and temperature. The fluorescence quantum yields of the two membranes are 0.024 × 0.003 and 0.17 × 0.03, respectively. The emission, which shows lifetimes in the 0.4 to 4 ns range, was assigned to heterogeneous populations of emitters, consisting, probably, of two tryptophans in the purple membrane and seven or eight residues in the apomembrane. Acrylamide quenching experiments showed that the accessibility of this neutral quencher to the fluorophors is reduced greatly in both membranes. Fluorimetric methods were also used in an attempt to monitor the purple complex reconstitution process. It was concluded that the fluorescence quantum yields of any monomers, dimers and trimers present in the partially reconstituted membranes should be very similar.

Finally, based on the spectroscopic results and on specific folding patterns of the seven α‐helical regions of bacteriorhodopsin (Stoeckenius and Bogomolni, 1982), it is proposed that Trp 137, Trp 138 (and perhaps Trp 10) of the protein molecule are the most plausible fluorophors in the purple membrane. It is also suggested that the protein in the apomembrane takes a more open configuration which is permeable to small ions and molecules.
FLASH INDUCED OSCILLATION OF THE LOW TEMPERATURE THERMOLUMINESCENCE BAND Zv IN CHLOROPLASTS
Authors: Vass Imre , Rzsa Zsuzsa , Demeter Sndor
Published: January 2008

Using preilluminating flashes at 2°C prior to continuous excitation of isolated chloroplasts at ‐80°C, a period‐four oscillation with maxima at the 0th, 4th and 8th flashes was observed in the amplitude of the thermoluminescence band Zv. Inactivation of the water‐splitting system by hydroxylamine‐ or Tris‐treatments greatly diminished the Zv band. On the other hand, its amplitude was not considerably affected by the addition of inhibitory concentration of DCMU. On the basis of the results, the possible origin of the Zv band is discussed.
ACTION SPECTRUM FOR PHOTOREACTIVATION OF ULTRAVIOLET‐INDUCED MORPHOLOGICAL ABNORMALITY IN SEA URCHIN EGGS
Authors: Ejima Yosuke , Ikenaga Mituo , Shiroya Tsugio
Published: January 2008

Abstract An action spectrum was obtained for photoreactivation (PR) of morphological abnormality arising from ultraviolet (UV)‐irradiation of sea urchin sperm. The wavelength dependence of PR was measured by the restoration of the formation of normal pluteus larvae after the exposure of fertilized eggs to various fluences of monochromatic PR light (313 to 500 nm). The PR action spectrum showed a maximum around 365 nm and a secondary peak somewhere above 400 nm. High PR activity beyond 400 nm wavelengths may reflect an advantageous or adaptational ability to cope with harmful effects of solar UV radiation.
PHOTOHEMOLYTIC LESIONS: STOICHIOMETRY OF CREATION BY PHLOXINE B
Authors: Valenzeno Dennis Paul
Published: January 2008

The uptake of the halogenated fluorescein sensitizers, Rose Bengal and phloxine B, by erythrocyte membranes was measured as a function of incubation time. Ghost membranes concentrate the sensitizers to levels greatly in excess of the sensitizer concentration in the suspension medium. Most of the uptake occurs in the first hour and is virtually complete by four hours. It is not significantly affected by stirring under the present conditions. The distribution of sensitizer cannot be explained as partitioning between immiscible solvents. Rather the data fits the Freundlich adsorption isotherm over a wide range of sensitizer concentrations and ghost protein values. Photohemolysis experiments were performed using sensitizer concentrations and incubation times similar to those used in the sensitizer uptake studies. The kinetics of lysis were found to vary with the 1.2 power of sensitizer concentration using PB. When combined with the uptake data for this sensitizer, these results imply that photohemolytic lesions in the red cell membrane are formed by the action of two sensitizer molecules.
KINETICS OF STACKING INTERACTIONS IN FLAVIN ADENINE DINUCLEOTIDE FROM TIME‐RESOLVED FLAVIN FLUORESCENCE
Authors: Visser A. J. W. G.
Published: January 2008

The time dependence of the fluorescence of flavin adenine dinucleotide (FAD) was measured with a subnanosecond‐resolving fluorometer. In contrast to the fluorescence decay of FMN, the decay of FAD was proved to be nonexponential. The time‐dependent fluorescence of FAD can be interpreted by assuming an equilibrium between closed and open conformers in the ground state. The rate constant for folding in the excited state and the fluorescence lifetime of the intramolecular complex could be evaluated from analysis of the observed fluorescence decay. The results on FAD were compared to those on NADH obtained earlier.
A MULTICHANNEL TRANSIENT SPECTRUM ANALYSER FOR ABSORPTION CHANGES MEASUREMENT WITH ONE MICROSECOND RESOLUTION
Authors: Furuya Masaki , Inoue Yasunori , Maeda Yoshio
Published: January 2008

A custom‐designed photometer for recording flashlight‐induced transient absorbance spectra with microsecond time resolution in the wavelength range from 350 to 800 nm with 0.5 nm resolution is reported. The apparatus is equipped with two 600 ns half‐width pulse (output = 400 mJ) tunable dye lasers for double‐flash analysis and an optical multichannel analyser having a silicon intensified target detector. Measuring light from a tungsten‐halogen lamp is passed through the sample, dispersed into a spectrum and focused on the head of the detector. A transient spectrum is measured over a range of 330 nm simultaneously by applying high voltage to the detector for the desired interval. The delay from the actinic flash to applying the high voltage can be controlled electronically. Distortion caused by scattering of the actinic flash under optimal conditions is negligible within 1.5 is after the flash peak. Detector linearity reaches about 104 and a noise level of less than ±0.005A can be achieved without data accumulation. This apparatus is applicable not only to transparent samples but to turbid ones with 100 μs resolution.
TRIPLET, RADICAL ANION AND RADICAL CATION SPECTRA OF FUROCOUMARINS
Authors: BENSASSON R. V. , CHALVET O. , LAND E. J. , RONFARD‐HARET J. C.
Published: January 2008

Abstract— Absorption spectra of triplets, radical anions and radical cations of four furocoumarins, psoralen (Ps), 8‐methoxypsoralen (8MOP), 5‐methoxypsoralen (5MOP) and 3‐carbethoxypsoralen (3CPs), have been determined by laser flash photolysis and pulse radiolysis. The triplet spectra of 8MOP, 5MOP and 3CPs are strongly modified when going from an H‐bonding solvent such as water to a non H‐bonding solvent as benzene or acetonitrile while the triplet spectrum of Ps is solvent independent. Theoretical considerations using a CNDO/S method are able to explain the existence of these two different triplets. For 8MOP, 5MOP and 3CPs in water the triplets might be considered as triplet exciplexes 3(FCδ‐. H2Oδ+) consistent with these triplet spectra being similar to the spectra of the corresponding radical anions.
DNA ASSOCIATED WITH THE CELL MEMBRANE IS INVOLVED IN THE INHIBITION OF THE SKIN REJECTION RESPONSE INDUCED BY INFUSIONS OF PHOTODAMAGED ALLOREACTIVE CELLS THAT MEDIATE REJECTION OF SKIN ALLOGRAFT
Authors: Perez Maritza I. , Yamane Yasuhiro , John Lori , Gasparro Francis P. , Edelson Richard L.
Published: January 2008

Abstract

Cell membrane DNA (cmDNA) is a form of DNA located on the surface of human and murine T‐cells. It has recently been characterized as a target for photomodification by 8‐methoxypsoralen (8‐MOP) and long‐wave ultraviolet light (UV‐A). Whereas 8‐MOP itself is biologically inert, photoactivated 8‐MOP is covalently bound to pyrimidine bases in DNA. We have investigated the possible involvement of cmDN A photomodification in the induction of the suppression of skin allograft rejection in BALB/c mice preimmunized with 8‐MOP/UV‐A photodamaged alloreactive cells which mediates this allograft rejection. This suppression is demonstrated by inhibition of delayed‐type hypersensitivity (DTH) and mixed leukocyte culture (MLC) responses. Splenocytes from BALB/c mice undergoing rejection of CBA/j skin graft which contained an expanded population of the effector T lymphocytes that mediate the rejection were treated with DNAse to remove cmDNA before or after treatment with 8‐MOP and UV‐A prior to infusion into naive BALB/c recipients. Mice that received pretreated effector cells were tested for MLC responses to CBA/j or B10 alloantigens before and after the DTH response. The DTH response of all groups of pretreated BALB/c mice to the relevant alloantigen was specifically suppressed as compared with the response of control mice. However, adoptive transfer of the suppression of the DTH response was optimally demonstrable only in syngeneic recipients of cells from donor mice treated with photodamaged alloreactive cells. Also, splenocytes from BALB/c mice immunized with photodamaged alloreactive cells demonstrated highly significant hyporesponsiveness and suppression of the MLC response of naive mice to the relevant alloantigen in the case of the primary MLC response, and to both alloantigens in the secondary MLC response which was totally eliminated by prior pretreatment of these effector cells with DNAse. Therefore, it appears that the suppression of the DTH response can be induced by pretreatment of the effector cells with DNAse and/or 8‐MOP and UV‐A but is adoptively transferable optimally only from mice which are recipients of photodamaged alloreactive cells. Moreover, the effectiveness of this treatment is decreased by prior removal of cmDNA from these cells. The presence of cmDNA is necessary for induction of suppression of the primary and secondary MLC responses in mice treated with photodamaged cells of allograft rejection.
ESTIMATION OF THE OPTICAL PARAMETERS AND LIGHT GRADIENTS IN LEAVES: MULTI‐FLUXversusTWO‐FLUX TREATMENT
Authors: Remisowsky Alexander Martinez v. , McClendon John H. , Fukshansky Leonid
Published: January 2008

Abstract

Parameters of light propagation in plant leaves‐absorption and scattering coefficients, asymmetry of scattering‐have been estimated on the basis of measured transmission and remission as well as internal fluxes. This estimation has been carried through by solving the inverse problem of the 4‐flux radiative transfer‐a theory considering forward and backward diffuse as well as directed components of the overall radiation in a multiply scattering sample. Using the gained parameters, light flux gradients in a two‐layered model leaf have been calculated at different wavelengths. Monte Carlo simulation of absorption spectra performed with the parameters obtained with this treatment is in a good agreement with experimental spectra, thus substantiating the theory. Parallel calculations with the two‐flux (Kubelka‐Munk) theory provide an estimation of the accuracy and applicability of this more simple treatment. Calculations have been performed for two different plants.
DIURNAL VARIATIONS IN LUMINESCENCE IN Scenedesmus obtusiusculus (CHLOROPHYCEAE) INDUCED BY 3‐(3,4‐DICHLOROPHENYL)‐1,1‐DIMETHYLUREA
Authors: Mellvig Staffan , Tillberg Jan‐Eric
Published: January 2008

Abstract— Luminescence from synchronously cultured Scenedesmus obtusiusculus cells was measured with a high sensitivity photon counter. Recording of light emission was initiated 0.2 s after switching off actinic light. Luminescence decay was separated into two phases: one for decay to 104 pulses s‐1, the other for decay from 104 to 103 pulses s‐1. Most photons are emitted during the rapid decay to 104 pulses s‐l. Only small diurnal variations of the two phases could be observed in controls. Treatment with 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU) decreased both the total number of photons emitted and the time required to reach the 104 pulses s‐1 level. No diurnal rhythmicity was induced by DCMU in the first phase but DCMU induced a pronounced diurnal variation in decay time in the second phase of luminescence parallelled by a periodicity in the number of photons emitted. The results indicate that DCMU interferes with the participation of PS I in luminescence. The chlorophyll alb ratio was constant during the life cycle of the cells. No relation could be observed between luminescence and the diurnal rhythmicity in photosynthesis that is characteristic for synchronized unicellular algae.
ACTION SPECTRUM STUDIES FOR INDUCTION OF IMMUNOLOGIC UNRESPONSIVENESS TO DINITROFLUOROBENZENE FOLLOWING IN VIVO LOW DOSE ULTRAVIOLET RADIATION
Authors: Elmets Craig A. , LeVine Mark J. , Bickers David R.
Published: January 2008

Abstract— Topical application of the contact sensitizer dinitrofluorobenzene to the skin of C3H mice previously exposed in vivo to low doses of UVB radiation from FS20 sun lamps resulted in the acquisition of antigen‐specific unresponsiveness to that hapten. When narrow band radiation at various wavelengths between 260 and 320 nm was employed, increasing doses of radiation were found to produce increasing amounts of immunosuppression. Construction of an action spectrum curve revealed that radiation between 260 and 300 nm was most efficient in producing unresponsiveness. Wavelengths above 300 nm were much less efficient than those below 300 nm. These results indicate that there are major differences in the effectiveness of various components of the short and middle wavelength UV spectrum in eliciting immunologic unresponsiveness to a topically administered hapten. Potential chromophores for this UVB‐induced immunosuppressive effect include DNA and urocanic acid.
DEACTIVATION OF PYRENE BY INDOLE IN MICELLAR SOLUTIONS
Authors: Encinas M. V. , Lissi E. A.
Published: January 2008

Abstract— The deactivation rate of excited pyrene by indole strongly depends on the polarity of the media. In micellar systems (Triton X‐100, cetyltrimcthylammonium chloride (CTAC) and sodium dodecylsulfate (SDS) the deactivation efficiency is enhanced due to the high local concentration of indole in the micellar pseudophase. Quantitative interpretation of the data in CTAC and SDS micelles requires to take into account indole exchange between the micelles and the aqueous phase. In SDS micelles, where due to their smaller size the exchange process is more relevant, the exit and entrance rates are (3.0 ± 0.6) x 106 and (1.2 ± 0.3) x 1010M−1s−1 respectively. Intramicellar bimolecular quenching constants are (1.1 ± 0.2) x 108 M−1 s−1 (1.4 ± 0.2) x 108M−1 s−1 and (1.5 ± 0.2) x 108M−1 s−1 in Triton X‐100, SDS and CTAC respectively. These rates are similar to those measured in ethanol rich ethanol‐water homogeneous solutions. This is in agreement with the average polarity sensed by both pyrene and indole in the micellar pseudophases.
REAL TIME COMPUTER‐CONTROLLED TRACKING OF MOTILE MICROORGANISMS
Authors: Häder Donat‐P. , Lebert Michael
Published: January 2008

Abstract— A hardware and software system is described which is capable of automatically following the movement of microorganisms and analyzing the deviation of individuals in a population from a predefined direction. The image of the moving organisms is viewed by a video camera, digitized in real time and stored in a dedicated video memory holding 512 times 256 pixels with 64 grey levels. A microcomputer has access to this video memory via four parallel ports. The software analyzes the position of an organism selected randomly and attempts to follow its track for a predefined period of time. If successful, it calculates the direction of movement and stores the data in a file for statistical analysis.

Using this system, the movement of populations of the unicellular flagellate, Euglena gracilis, in unilateral and bilateral light beams has been studied and compared with the dark behavior. When irradiated from two opposite light sources of equal fluence rates half of the population swims towards either light source. However, when the light sources are oriented at an angle of 90° to each other the cells move on the resultant away from the light. These results confirm the shading hypothesis for negative phototaxis.
QUENCHING OF TRYPTOPHAN PHOSPHORESCENCE IN ALCOHOL DEHYDROGENASE FROM HORSE LIVER and ITS TEMPERATURE DEPENDENCE
Authors: Barboy Natalie , Feitelson Jehuda
Published: January 2008

Abstract— The phosphorescence of alcohol dehydrogenase from horse liver (LADH) can be observed at room temperature. The quenching of this long‐lived light emission, which comes from a tryptophan residue well buried within the interior of the enzyme structure, was measured. The rate constants for the quenching by the small oxygen molecule and by the I‐1ion were found to be 1.4 → 108M‐1 s‐1 and 108M‐1 s‐1, respectively, at room temperature. The temperature dependence of the quenching yields an activation energy of about 14 kcal/mol. This activation energy and the meaning of the accompanying large pre‐exponential factor in the Arrhenius equation, A = 1018M‐l s‐1, are discussed in terms of a model in which the quencher threads its way through the protein network.
EFFECT OF WATER ON PHOTOCHEMICAL REDUCTION OF CONCENTRATED THIONINE SOLUTION BY VISIBLE LIGHT
Authors: Temizer Aytekin
Published: January 2008

Abstract— The photochemical reactions in concentrated thionine solution have been studied using continuous illumination. Thionine solution is photoreduced to leucothionine in an oxygen‐free acidic medium. Electrochemical measurements of the photoreduction of thionine are reported. A possible reaction pathway for the energy transfer is proposed. It is found that polymeric forms of thionine and leucothionine are not involved in photoreduction. It is proposed that a complex must be formed prior to photochemical reduction. This complex species, having a lifetime of several seconds, is reduced to leucothionine, water being the reducing agent. Following this reduction, H2O2 is formed and the production of H2O2 is detected by differential pulse polarography.
FLUORESCENCE QUENCHING FOR FLAVINS INTERACTING WITH EGG WHITE RIBOFLAVIN‐BINDING PROTEIN
Authors: Bystra‐Mieloszyk K. , Balter A. , Drabent R.
Published: January 2008

Abstract— The effect of flavin structure variation upon the binding process of flavin to hen egg white riboflavin was studied using fluorescence methods for formylmethylflavin (FMF), riboflavin (RF) and flavomononucleotide (FMN).

Measurements of flavin fluorescence intensities (steady state and phase‐sensitive) and lifetimes were performed in a variety of RBP concentrations and temperatures (4 to 40°C). No fluorescence of flavoproteins was detected, while the fluorescence of flavins was found to be quenched by RBP. The overall quenching process is dominated by the static quenching (about 88%) due to the flavoprotein complex formation in the ground state, presumably a charge transfer complex.
NEGATIVE PHOTOTAXIS OF Dictyostelium discoideum PSEUDOPLASMODIA IN UV RADIATION
Authors: Häder Donat‐P.
Published: January 2008

Abstract— Pseudoplasmodia of the cellular slime mold Dictyostelium discoideum show negative phototactic orientation in lateral ultraviolet radiation. The action spectrum has a peak in the UV‐B band near 280 nm. The absorption spectrum shows a prominent peak in the same wavelength range. Thus, negative phototaxis can be easily explained by the assumption that the lens effect, by which D. discoideum slugs detect the light direction, is defeated by the high internal absorption in this wavelength range.
EXCITATION ENERGY TRANSFER IN THE CHROMATICALLY ADAPTED PHYCOBILIN SYSTEMS OF BLUE‐GREEN ALGAE: DIFFERENCE IN THE ENERGY TRANSFER KINETICS AT PHYCOCYANIN LEVEL
Authors: Mimuro Mamoru , Yamazaki Iwao , Yamazaki Tomoko , Fujita Yoshihiko
Published: January 2008

Abstract— Excitation energy transfer in chromatically adapted phycobilin system was investigated with the blue‐green algae Tolypothrix tenuis and, supplementary, Fremyella diplosiphon with use of time‐resolved fluorescence spectrum (Yamazaki et al, 1984). Special attention was paid to the energy migration at the phycocyanin (PC) level in the phycoerythrin (PE)‐rich and PE excited system and in the PE‐less and PC excited system. The energy transfer from PC to allophycocyanin was far faster in the former than in the latter in both organisms. Such feature was the same as our previous observation for PE‐rich system of Porphyridium cruentum and PE‐less system of Anacystis nidulans (Yamazaki et al, 1984). Thus, the difference in phycobilisome structure is not a cause for such difference. Based on simulation analysis, we interpreted our observation as that (1) all PC chtomophores do not equally participate to the energy migration within PC compartment but (2) a short transfer path through PC compartment is formed probably by f‐type chromophores and (3) the difference in the “length” of this path is a main determinant for kinetic difference between PE‐rich and PE‐less systems.
ULTRAVIOLET LIGHT IRRADIATION OF DEFINED‐SEQUENCE DNA UNDER CONDITIONS OF CHEMICAL PHOTOSENSITIZATION
Authors: Umlas Marc E. , Franklin William A. , Chan Gerald L. , Haseltine William A.
Published: January 2008

Abstract— The formation of cyclobutane pyrimidine dimers and UV light‐induced (6‐4) products was examined under conditions of triplet state photosensitization. DNA fragments of defined sequence were irradiated with 313 nm light in the presence of either acetone qr silver ion. UV irradiation in the presence of both silver ion and acetone enhanced the formation of TT cyclobutane dimers, yet no (6‐4) photoproducts were formed at appreciable levels. When photoproduct formation was also measured in pyrimidine dinucleotides, only cyclobutane dimers were formed when the dinucleotides were exposed to 313 nm light in the presence of photosensitizer. The relative distribution of each type of cyclobutane dimer formed was compared for DNA fragments that were irradiated with 254, 313, or 313 nm UV light in the presence of acetone. The dimer distribution for DNA irradiated with 254 and 313 nm UV light were very similar, whereas the distribution for DNA irradiated with 313 nm light in the presence of acetone favored TT dimers. Alkaline labile lesions at guanine sites were also seen when DNA was irradiated with 313 nm light in the presence of acetone.
PHYTOCHROME MACRO‐DISTRIBUTION, LOCAL PHOTOCONVERSION AND INTERNAL PHOTON FLUENCE RATE FOR Cucurbita pepo L. COTYLEDONS
Authors: Seyfried Max , Schäfer Eberhard
Published: January 2008

Abstract—Using 7‐day‐oId cotyledons ofCucurbita pepoL., local phytochrome photoconversions could be measured for blue, red and far‐red light. For this purpose, after nonsaturating irradiation, cotyledons were sliced into discs 0.3 to 0.5 mm thick andsignals measured. This method also yielded the internal phytochrome distribution of the cotyledons with maximal concentration near the adaxial surface, dropping to about 50% in the center and reaching again about 90% at the abaxial surface. Local phytochrome conversion rates were used to calculate internal fluence rates across the cotyledons. Relative internal fluence rates were also derived from measured reflectances and transmittance according to the Kubelka‐Munk theory. The general shape of the internal fluence distribution calculated on the basis of these two methods coincided well. It was observed that the internal local photoconversion is proportional to the penetration depth over a wide range of incident fluences and for all wavelengths tested, showing in addition that reciprocity holds. A method to calculate internal fluence rates by a simplified procedure assuming either linear or exponential functions is described.
THE OPTICAL PROPERTIES OF ADENINE FROM 1.8 TO 80 eV*
Authors: Arakawa E. T. , Emerson L. C. , Juan S. I. , Ashley J. C. , Williams M. W.
Published: January 2008

Experimental measurements of the optical reflectance of solid adenine films have been obtained for photon energies extending from 1.8 to 80 eV. From these data we have established the complex index of refraction, the complex dielectric function, and the energy‐loss function Im(‐l/). Structure in the dielectric functions are ascribed to * transitions at photon energies less than ~9 eV and to * transitions at higher energies. A broad peak in the energy‐loss function near 24 eV is associated with a collective resonance involving all the valence electrons. Sum rule calculations are used to demonstrate the overall consistency of the data.
WAVELENGTH DEPENDENCE OF THE FORMATION OF SINGLE‐STRAND BREAKS AND BASE CHANGES IN DNA BY THE ULTRAVIOLET RADIATION ABOVE 150 nm
Authors: Hidea Kotaro , Hayakawa Yoshihiko , Ito Atsushi , Kobayashi Katsumi , Ito Takashi
Published: January 2008

The wavelength dependence of the formation of two types of DNA damage, single‐strand breaks and base changes, was investigated in the UV region from 150 nm to 254 nm using superhelical closed circular (form I) colicin El DNA with synchrotron radiation. Single‐strand breaks were measured by agarose gel electrophoresis as a direct conversion of form I DNA to form II DNA (open circular). Base damages were defined as sensitive sites to a crude extract of endonuclease from Micrococcus luteus. They also were estimated using the same conversion, from form I to form II after the DNA was treated with endonuclease. The fluence‐effect relationship could be fitted by a simple exponential function for both types of damage. Action spectra were constructed based on the reciprocal of the 37% fluence. The action spectrum for strand breaks increased rather monotonically over three decades from 254 nm to 150 nm in a logarithmic scale, while that for base damages showed a breaking point at 190 nm, being relatively flat above 190 nm. The characteristics of the action spectra are compared with the absorption spectra of the DNA and its main chain moiety calculated on the basis of data on calf thymus DNA and synthetic polynucleotides. Our main conclusions are (1) that the majority of single‐strand breaks were induced by the absorption of photon in the sugar‐phosphate group in the vacuum‐UV region and (2) that the base changes were induced equally well by absorption in the vacuum‐UV and in the far‐UV region.
ACTION SPECTRA IN ULTRAVIOLET WAVELENGTHS (150‐250 nm) FOR INACTIVATION AND MUTAGENESIS OF Bacillus subtilis SPORES OBTAINED WITH SYNCHROTRON RADIATION
Authors: Munakata N. , Hidea K. , Kobayashi K. , Ito A. , Ito T.
Published: January 2008

Bacillus subtilis spores were exposed in vacuo to monochromatic UV radiation from synchrotron radiation in the wavelength range of 150 nm to 250 nm. Survival and frequency of mutation to histidine‐independent reversion were analysed for three types of spores differing in DNA‐repair capabilities. UVR spores (wild‐type DNA repair capability) exhibited nearly equal sensitivity to the lethal effects of far‐UV (220 nm and 250 nm) and of vacuum‐UV radiation (150 and 165 nm), but showed marked resistance to 190 nm radiation. UVS spores (excision‐repair and spore‐repair deficient) and UVP spores (a DNA polymerase I‐defective derivative of UVS) exhibited similar action spectra; pronounced sensitivity at 250 and 220 nm, insensitivity at 190 nm and a gradual increase of the sensitivity as the wavelength decreased to 165 nm. In all strains, the action spectra for mutation induction paralleled those for the inactivation, indicating that vacuum‐UV radiation induced lethal and mutagenic damages in the spore DNA. The insensitivity of the spores to wavelengths around 190 nm may be explicable by assuming that radiation is absorbed by materials surrounding the core in which DNA is situated.
EFFECTS OF SOLAR AND ARTIFICIAL UV IRRADIATION ON MOTILITY AND PHOTOTAXIS IN THE FLAGELLATE, Euglena gracilis
Authors: Hauder Donat‐P.
Published: January 2008

The effect of solar irradiation on the percentage of motile cells, their average speed and their phototactic orientation to white actinic light was studied in the flagellate, Euglena gracilis. Unfiltered solar radiation in midsummer during mid‐day at a location near Lisboa, Portugal, was found to impair motility within 2 h. This effect is exclusively due to the UV‐B component of the radiation and not due to UV‐A, visible light or a temperature increase. Likewise, phototactic orientation was drastically impaired. Reduction of the solar UV‐B irradiation by insertion of an ozone‐Hooded plexiglass cuvette partially reduced the inhibition and covering the cuvettes with glass prevented any decrease in motility and photoorientation. Similar results were found with artificial irradiation (Xe lamps). After inoculation the motility of the population follows an optimum curve (optimum at 8 days). Also, the UV‐B effect on motility was smallest after about one week and increased for younger and older cultures.
OXIDATION OF WATER WITH PHOTOCATALYST—I. REDUCTION OF ELECTRON ACCEPTORS IN WATER SOLUTION WITHOUT ADDITIONAL ELECTRON DONORS
Authors: Marinov Beniamin S.
Published: January 2008

Photoreduction of electron acceptors—myoglobin, hemin and methyl viologen—sensitized by eosin or methylene blue in water solution was studied. The rate of photoreduction of acceptors grows with increasing pH. At pH 9.0 quantum yield of myoglobin reduction reached 1.5%, whereas the efficiency of the low molecular weight acceptors—hemin and methyl viologen—was much lower. Control experiments demonstrated that buffer molecules and the protein moiety were not the source of electrons for the reduction. All the data support the conclusion that in the process under the study hydroxide ions of water appear to be the linal electron donors.
PHOTOCLEAVAGE OF DNA IN THE PRESENCE OF SYNTHETIC WATER‐SOLUBLE PORPHYRINS
Authors: Praseuth Dani`le , Gaudemer Alain , Verlhac Jean‐Baptiste , Kraljic I. , Sissoëff I. , Guillé E.
Published: January 2008

In the presence of oxygen and visible light, various synthetic water‐soluble porphyrins cleave pBR 322 plasmid supercoiled DNA (form I) producing relaxed (form II) and linear (form III) DNA corresponding to single‐strand and double‐strand breaks respectively. Large variations are observed in the efficiency of the porphyrins containing a diamagnetic metal or no metal at all. Singlet oxygen (1O2) seems to be involved in the mechanism of cleavage consistent with the inhibitory effect of the azide anion, N–3. The higher efficiency of cationic porphyrins (as compared to anionic ones) is due to their greater affinity for DNA as shown by experiments carried out at either high ionic strength or in the presence of the surfactant, sodium dodecyl sulfate.
ULTRAVIOLET HYPERSENSITIVITY OF COCKAYNE SYNDROME LYMPHOBLASTOID LINES—THE EFFECTS OF EXOGENOUS β‐NICOTINAMIDE ADENINE DINUCLEOTIDE
Authors: Otsuka Fujio , Kukita Atsushi
Published: January 2008

Four Cockayne Syndrome (CS) lymphoblastoid lines were tested for the lethal effects of UV radiation (254 nm) with or without addition of exogenous β‐nicotinamide adenine dinucleotide (β‐NAD +) to their culture medium. Two of them exhibited a small but significantly increased resistance to UV radiation when β‐NAD+ was added to the culture. However, their UV sensitivity after β‐NAD + addition was still much greater than that of normal control lines. Normal control lymphoblastoid lines and those from complementation group A and group C of xeroderma pigmentosum (XP) did not reveal any differences in post‐UV sensitivity after the addition of exogenous β‐NAD+. Thus the abnormal response to the lethal effects of UV radiation of CS lymphoblastoid lines could not be rectified by β‐NAD+ addition. However, β‐NAD+ does appear to play some partial role in reducing the high UV sensitivity of some CS lymphoblastoid lines.
SELECTIVE TYPE I PHOTOOXIDATIONS IN MIXTURES OF PORPHYRINS AND ELECTROPHILIC NITROIMIDAZOLES
Authors: Bazin M. , Santus R.
Published: January 2008

Abstract— Electrophilic compounds metronidazole (METRO) and misonidazole (MISO), considerably enhance the photooxidation quantum yield of Type I photodynamic substrates such as Trp, Tyr and Cys. For the latter, the quantum yield of photooxidation which can be much greater than one, suggests radical chain reactions. On the other hand, METRO and MISO inhibit 1O2 formation because they react at diffusion controlled rate (∼109M−1 S−1) with porphyrin triplets forming, porphyrin radical cations. As a result, the porphyrins are still able to photosensitize the destruction of Type I substrates even in the absence of O2. These results are discussed with respect to the possibility of increasing the sensitivity of hypoxic cells to porphyrin photosensitization.
ELIMINATION OF RESIDUAL TUMOR CELLS FROM AUTOLOGOUS BONE MARROW GRAFTS BY DYE‐MEDIATED PHOTOLYSIS: PRECLINICAL DATA*
Authors: Sieber Fritz
Published: January 2008

Abstract MC540‐mediated photolysis has several features that make it potentially attractive as a clinical purging procedure. (1) The experience with experimental tumors suggests that MC 540‐mediated photolysis is effective against a broad range of leukemias and solid tumors, including drug‐resistant tumors (Sieber et al., 1984b). Drug‐resistant tumor cells are likely to occur in heavily pretreated patients. (2) MC540‐mediated photolysis is not cell‐cycle dependent (Manna and Sieber, 1985). It kills both resting and cycling cells. In this regard, MC 540‐mediated photolysis is a valuable complement to cell‐cycle specific cytotoxic drugs. (3) There is a large differential in sensitivity between normal pluripotent hematopoietic stem cells and leukemia and neuroblastoma cells. (4) The mechanism of action of MC 540‐mediated photolysis is different from that of lectins, antibodies and most cytotoxic drugs. MC 540 binds to the lipid portion of the plasma membrane and membrane lipids are probably a primary target of the toxic photoproducts. Antibodies and lectins react with proteins and carbohydrates and most drugs have intracellular targets (e.g. nuclear DNA). We would therefore expect little cross‐resistance if MC 540‐mediated photolysis were used in combination with other purging procedures. (5) The small amounts of dye that remain associated with the marrow graft and are infused into the patient are approximately 100 000‐fold less than the LD10 (in mice) and therefore unlikely to cause any harm. The outcome of the first clinical application of the technique supports this view (Sieber et al., 1986c).

A better understanding of the underlying molecular mechanisms will undoubtedly lead to more effective applications of the technique and perhaps to the identification of more potent analogs of MC 540.
EFFECTS OF UV‐B IRRADIATION ON PHOTOMOVEMENT IN THE DESMID, Cosmarium cucumis
Authors: Häder Donat‐P.
Published: January 2008

Abstract Monochromatic UV‐B irradiation affects neither the absorption nor the fluorescence of the bulk pigments in the desmid Cosmarium cucumis but it impairs photomovement of these organisms at fluence rates which are not higher than the ambient level of solar UV‐B irradiation. Photoaccumula‐tions and phototaxis are strongly inhibited especially at wavelengths ≤ 300 nm while photodispersal at higher white light fluence rates is hardly affected by supplementary UV‐B. This effect has important consequences for the growth and survival of populations in their natural environment: these photosyn‐thetic organisms utilize photomovement to find and stay in areas of suitable visible light fluence rates. The UV‐B component of solar irradiation both impairs the strategy of the organisms to find a suitable position and the escape mechanism by which the cells move out of areas with too strong white illuminances which photooxidize the bulk pigments and bleach the population within a few days.
AN ACTION SPECTRUM IN THE BLUE and ULTRAVIOLET FOR PHOTOTROPISM IN ALFALFA*
Authors: Baskin Tobias Isaac , Iino Moritoshi
Published: January 2008

Abstract Phototropism is a common property of plants, but it is not known if different species use the same photoreceptor for their response. We have determined fluence‐response relations for phototropism in response to brief, broad‐band blue irradiation for four plant species grown under red light (Amaranthus paniculatus, Linum usitatissimum, Vigna radiata and Medicago sativa) and compared these to ones previously obtained for Pisum sativum and Zea mays, grown under similar conditions. Curves for all species showed a bell‐shaped dependence on fluence, a characteristic of first positive curvature as originally defined for the Avena coleoptile, and had a similar optimal fluence, near 3 H.mol m−2. We have obtained an action spectrum in the blue and UV spectral regions for first positive phototropism of the hypocotyl of alfalfa grown under red light. Fluence‐response curves at wavelengths between 300 and 500 nm were nearly identical in shape and magnitude; whereas below 300 nm, their slopes and maximum curvatures were reduced. The action spectrum showed that activity rose sharply at wavelengths below 500 nm, peaked at 450 nm with shoulders on either side of that peak, and had lesser peaks at 380 and, in the far ultraviolet, at 280 nm. This action spectrum was very similar to ones in the literature (obtained between 350 and 500 nm) for first and second positive phototropism of oat coleoptiles. We conclude that the same photoreceptor mediates phototropism in oat and alfalfa.
FÖRSTER TRANSFER CALCULATIONS BASED ON CRYSTAL STRUCTURE DATA FROM Agmenellum quadruplicatum C‐PHYCOCYANIN
Authors: Sauer Kenneth , Scheer Hugo , Sauer Peter
Published: January 2008

Excitation energy transfer in C‐phycocyanin is modeled using the Forster inductive resonance mechanism. Detailed calculations are carried out using coordinates and orientations of the chromophores derived from X‐ray crystallographic studies of C‐phycocyanin from two different species (Schirmer et al, J. Mol. Biol.184, 257–277 (1985) and ibid., 188, 651‐677 (1986)). Spectral overlap integrals are estimated from absorption and fluorescence spectra of C‐phycocyanin of Mastigocladus laminosus and its separated subunits. Calculations are carried out for the β‐subunit, αβ‐monomer, (αβ)3‐trimer and (αβ)0‐hexamer species with the following chromophore assignments: β155 = 's’(sensitizer), β84 =‘f (fluorescer) and α84 =‘m’(intermediate):]:. The calculations show that excitation transfer relaxation occurs to 3=98% within 200 ps in nearly every case; however, the rates increase as much as 10‐fold for the higher aggregates. Comparison with experimental data on fluorescence decay and depolarization kinetics from the literature shows qualitative agreement with these calculations. We conclude that Forster transfer is sufficient to account for all of the observed fluorescence properties of C‐phycocyanin in aggregation states up to the hexamer and in the absence of linker polypeptides.
UV PHOTOBIOLOGY OF THE NEMATODE Caenorhabditis elegans: ACTION SPECTRA, ABSENCE OF PHOTOREACTIVATION and EFFECTS OF CAFFEINE
Authors: Keller Cindy I. , Calkins John , Hartman Phillip S. , Rupert Claud S.
Published: January 2008

Action spectra for UV inactivation of reproduction in Caenorhabditis elegans have been obtained for strains N2 (wild‐type) and rad‐3 (radiation‐sensitive). Use of a dye laser radiation source, providing high intensity in a narrow wavelength band, has permitted more detail (14 wavelengths between 260 and 320 nm) than available in the spectra for other multicellular organisms. Overall sensitivity of N2 is similar to that of wild‐type Escherichia coli; that of rad‐3 is 30‐fold higher between 265 and 310 nm; relative sensitivity decreases above 310 nm but also seems to increase for irradiation below 265 nm. Tests for photoreactivation and for modification of survival by post‐irradiation treatment with caffeine were negative.
ESTIMATION OF AN INDEX OF HYDROPHOBICITY OF DNA INTERIOR USING 5‐METHOXYPSORALEN AS A FLUORESCENT PROBE
Authors: Sasaki Masako , Nakasato Isao , Sugiura Hiroyuki , Fujita Hitoshi , Sakata Toshibumi
Published: January 2008

The index of hydrophobicity of DNA interior was estimated by measuring fluorescence spectra of psoralen derivatives associated with DNA. The environment around 5‐MOP associated with DNA was as hydrophobic (Dk= 34) as methanol, suggesting that the molecules reside at the space between the base‐pairs in B‐form DNA. This is also true for 8‐MOP. Thus, planar and aromatic molecules of 5‐ and 8‐MOP are more stable in the interior of DNA than in aqueous medium due to hydrophobic affinity.
PHOTOPHYSICAL PROPERTIES OF PORPHYRIN‐CHLORIN SYSTEMS IN THE PRESENCE OF SURFACTANTS
Authors: Cubeddu Rinaldo , Keir William F. , Ramponi Roberta , Truscott T. George
Published: January 2008

Abstract The therapeutic efficacy of PDT is related to the capability of the photosensitizer to absorb light at a wavelength that can penetrate into tissues. We have synthesized two systems, a haematoporphyrin‐chlorin (HPC) and a dihaematoporphyrin ether or ester (DHE) with the terminal ring converted to a chlorin (DHEC). The presence of the chlorin moiety provides an extra band at ˜ 660 nm with a relative amplitude from 5 to 10 times larger than that of the porphyrin at 630 nm. Since both HPC and DHEC strongly aggregate in buffer, we have studied their photophysical properties in the presence of cationic surfactants at different concentrations below and above the critical micelle concentrations. Absorption spectra were measured together with emission spectra and fluorescence decays at different observation wavelengths under excitation at 364 nm. The results were compared with those obtained for DHE in the same environmental conditions. As for DHE, the presence of micelles disaggregate both compounds, resulting in a large increase in the relative emission intensity at ˜ 670 nm due to the presence of the chlorin moiety. The fluorescence decays could be fitted by two or three exponential components indicating the presence of more than one molecular species and/ or conformations. On the basis of our measurements the chlorin molecule does not seem to modify appreciably the photophysical properties of the porphyrin molecules but does superimpose its absorption and emission spectrum onto that of the porphyrin. This result may be of relevance in the possible use of these compounds in PDT.
ROLE OF SPECIFIC CELLULAR TARGETS IN THE HEMATOPORPHYRIN‐SENSITIZED PHOTOINACTIVATION OF MICROBIAL CELLS
Authors: Bertoloni G. , Zambotto F. , Conventi L. , Reddi E. , Jori G.
Published: January 2008

Abstract The hematoporphyrin‐sensitized photoinactivation of Candida albicans is mainly carried out by porphyrin molecules which are present in the cell‐incubation medium. Photoexcitation of hematoporphyrin by visible light appears to cause limited biochemical and functional alterations of the cytoplasmic membrane; this allows the penetration of the dye into the cell, with a consequent important photoinactivation of the mitochondria. The latter process is of critical importance for the decrease in the survival of the irradiated cells.