bluuebunny/crossref_metadata_2025 huggingface dataset:
PHOTOREPAIR OF PYRIMIDINE DIMERS IN THE EPIDERMIS OF THE MARSUPIAL Monodelphis domestica*
Authors: Ley R. D.
Published: January 2008

Abstract Induction and fate of ultraviolet radiation‐induced pyrimidine dimers in DNA have been measured in the epidermis of the marsupial, Monodelphis domestica, using damage‐specific endonucleases from Micrococcus luteus. Approximately 90% of the dimers are lost when irradiated animals are subjected to photoreactivating light for 180 min. No loss of dimers was detected when the animals were held for a similar period of time in the dark. The capacity of these epithelial cells to photorepair pyrimidine dimers may provide a useful whole animal system in which to determine the role of pyrimidine dimers in photobiological responses of the skin.
FLUORESCENCE PROPERTIES OF C‐PHYCOCYANIN ISOLATED FROM A THERMOPHILIC CYANOBACTERIUM
Authors: Seibert Michael , Connolly John S.
Published: January 2008

AbstractThe fluorescence lifetime of purified C‐phycocyanin from the thermophilic cyanobacterium,Phormidium laminosum(strain OH‐1‐p. Cl 1), was measured as 1.48 ± 0.06 ns using the technique of time‐correlated single‐photon counting under very weak excitation pulses. The natural radiative lifetime (∼6.1 ns) of the pigment was calculated by integrating the absorption spectrum using the Strickler–Berg equation. From these two lifetimes we calculate a fluorescence quantum yield of ∼0.24 which is very close to the value ∼0.22 which we measure relative to the known value of cresyl violet in methanol. Both the fluorescence lifetime and the quantum yield of the pigment from this organism are lower than most previous values reported in the literature. We conclude that our lower values are not due to high light intensity, pH, buffer, concentration, instrumentation artifacts, aggregation effects or the thermophilic nature of the organism. Instead, we suggest that the photophysical properties of C‐phycocyanin are species dependent, perhaps due to the specific molecular environment of the tetrapyrrole.
STUDIES ON PHYTOCHROME PHOTOCONVERSIONS IN VITRO WITH LASER‐INDUCED OPTOACOUSTIC SPECTROSCOPY*
Authors: Jabben Merten , Heihoff Klaus , Braslavsky Silvia E. , Schaffner Kurt
Published: January 2008

After excitation at room temperature with a 15 ns dye laser pulse, phytochrome (60 kDalton) from etiolated oat seedlings was studied by optoacoustic spectroscopy, which records the heat emission caused by non‐radiative deactivation processes of the photoexcited molecule. The action spectrum for the heat emitted by Pr deviates from the absorption spectrum around 610 and 695 nm, indicating the build‐up of photoproduct(s) within 15 ns after excitation. It is proposed that the 695 nm product is identical with I700 and lumi‐R known to be the first intermediate on the Pr× Pfr pathway, and that the photochemical back reaction of I700 to Pr occurs on the same time scale. About 90% of the absorbed light energy was lost by radiationless deactivation. Values for the rate constants of excited state deactivation of Pr and for the internal energy content difference of the primary photoproducts are calculated.
TESTING KINETIC MODELS FOR THE BACTERIORHODOPSIN PHOTOCYCLE—II. INCLUSION OF AN O TO M BACKREACTION
Authors: Parodi Luis A. , Lozier Richard H. , Bhattacharjee Somendra M. , Nagle John F.
Published: January 2008

Abstract Using previously established procedures we have tested a kinetic model of bacteriorhodopsin involving a backreaction from O to M. This model is superior to the previously tested models involving only unidirectional reaction paths. However, the spectrum of O is still too strongly temperature dependent in the red. Therefore, at least one additional feature is necessary to obtain a completely consistent kinetic model of the bacteriorhodopsin photocycle.
EVIDENCE FOR A HETEROGENOUS ORGANIZATION OF VIOLAXANTHIN IN THYLAKOID MEMBRANES
Authors: Siefermann‐Harms Dorothea
Published: January 2008

AbstractTwo functionally different species of violaxanthin have been observed in thylakoid membranes, one that can be de‐epoxidised to zeaxanthin under light and one not available for light‐induced zeaxanthin formation (Siefermann, D. and H. Y. Yamamoto, 1974,Biochim. Biophys. Acta357, 144–150). Here the distribution of available and unavailable violaxanthin is examined between membrane subfractions obtained from Triton X‐100 solubilized spinach thylakoids by isoelectric focusing: (1) Only 40% of the available violaxanthin is detected in isolated Chl‐proteins, while the residual 60% occur in a fraction of‘free’pigments; (2) Almost 80% of the unavailable violaxanthin is recovered from the light‐harvesting Chla/b‐protein complex (36%) and from photochemically active complexes containing photosystem I (20%) or photosystem II (20%). The results suggest a heterogenous organization of available and unavailable violaxanthin in thylakoid membranes.
LIGHT‐INDUCED CHEMOTACTIC REACTIONS IN THE DINOFLAGELLATE,Peridiniopsis berolinensis
Authors: Häder Maria
Published: January 2008

AbstractThe photosensitizer riboflavin induces accumulation of the colorless flagellatePeridiniopsis berolinensisin a light field at low photon fluence rates but dispersal from a light field at high photon fluence rates. The wavelength dependence of the accumulation resembles the absorption spectrum of riboflavin in the visible range. The photodynamic effects are caused by a positive or negative chemotactic response to photoproducts in the medium which are produced by photochemical reactions of the dye.
A WAVELENGTH EFFECT ON UROCANIC ACID E/Z PHOTOISOMERIZATION*
Authors: Morrison Harry , Bernasconi Christian , Pandey Ganesh
Published: January 2008

Abstract E‐Urocanic acid exhibits a single, featureless, long‐wavelength absorption band with λmax˜258 nm in water. However, the quantum efficiency for E→Z photoisomerization is wavelength dependent in this region, with the maximum value at the low energy edge of the band (e.g. 313 nm) and appreciably lower efficiencies measured at ≦ 300 nm.
ULTRAVIOLET ACTION SPECTRA FOR DNA DIMER INDUCTION, LETHALITY, AND MUTAGENESIS IN Escherichia coli WITH EMPHASIS ON THE UVB REGION
Authors: Peak M. J. , Peak J. G. , Moehring M. P. , Webs R. B.
Published: January 2008

Abstract —Ultraviolet (UV) action spectra were obtained for lethality and mutagenesis (reversion to tryptophan independence) in Escherichia coli WP2s for wavelengths 254–405 nm with detailed analysis in the UVB region (290–320 nm). Parallel chemical assay yields of pyrimidine dimers in DNA of E. coli RT4 were determined at the same wavelengths. Spectral regions isolated from a Xe arc and resonance lines from a high‐pressure Hg‐Xe arc lamp were both used for irradiation. In all cases, precise energy distributions throughout the isolated Xe bands regions were defined.

Lethality, mutagenesis, and dimer induction all decreased in efficiency in a similar fashion as the wavelengths of the radiation increased. Between 300 and 320 nm, all characteristics measured showed differences of about two and a half orders of magnitude. Between these wavelengths, the values of the three end points used either coincide with or parallel the absorption spectrum of DNA. The mutagenesis action spectrum coincides closely with the absorption spectrum of DNA. The lethality spectrum is closely parallel to the mutagenicity spectrum; the points, however, consistently occur at about 2 nm longer wavelengths. A calculation derived from the slope of the UVB spectra reveals that a 1‐nm shift of the solar UV spectrum to shorter wavelengths would result in a 35% increase in its mutagenic potential. At 325 nm, both biological action spectra show sharp decreases in slope. In addition, above 325 nm the spectra for lethality. mutagenicity, and dimer formation diverge sharply; lethalities at these UVA wavelengths were approximately tenfold greater relative to mutagenicity than at shorter wavelengths. The relative yield of dimer formation by 365 nm radiation is intermediate between the yields for lethality and mutagenesis.
ACTION SPECTRA FOR HEMATOPORPHYRIN DERIVATIVE AND PHOTOFRIN II WITH RESPECT TO SENSITIZATION OF HUMAN CELLSIN VITROTO PHOTOINACTIVATION
Authors: Moan Johan , Sommer Stein
Published: January 2008

Abstract—Human cells of the line NHIK 3025 were labelled with hematoporphyrin derivative (Hpd) or Photofrin II (PII). Absorption and fluorescence excitation spectra of cell‐bound porphyrins were recorded. Furthermore, the corresponding action spectra for photoinactivation of the cells were determined in the spectral region 350–650 nm. The cell‐bound porphyrins were also analysed by means of HPLC. The following conclusions are drawn:

(a) Porphyrins with low polarity are selectively bound to the cells.

(b) Aggregated as well as unaggregated porphyrins are bound to the cells.

(c) The action spectra indicate that the aggregated porphyrins do not contribute significantly to the photosensitivity of the cells.

(d) The action spectra closely resemble the fluorescence excitation spectra of porphyrins bound to proteins.
SALT AND pH‐DEPENDENT CHANGES OF THE PURPLE MEMBRANE ABSORPTION SPECTRUM
Authors: Kimura Yoshiaki , Ikegami Akira , Stoeckenius Walther
Published: January 2008

Abstract —Purple membrane suspensions change their color to blue and the absorption maximum shifts to 608 nm when the membrane is deionized on a cation exchange column or when it is washed first with < 2N NaCl followed by deionized water. The deionized chromophore is essentially identical with the chromophore produced by lowering the pH of the native membrane to < 4.0 (pK < 3.0). However, the deionized membrane does not aggregate and can be obtained in the pure state. The original purple color of the membrane is restored by addition of around 1 mM Na+, K+ or 10 μM Mg2+, Ca2+, Sr2+, Mn2+, Pb2+ or La2+ when the protein concentration is 5μM. The required salt concentrations decrease with decreasing pH. Direct measurement of bound Ca2+ by atomic absorption spectroscopy yields a ratio of Ca2+ to protein of <2 and a binding constant of 1.4 × 106. Titration of the spectral change with salts at different pH values shows a linear relation between the pH and the logarithm of the salt concentration, with a 1:1 ratio for Na+ and 1:2 ratio for Ca2+. These relations are well predicted by Gouy‐Chapman theory; however, the accompanying release of protons, changes of the CD spectrum, the complex kinetics of the spectral change during reconstitution with salt and preliminary X‐ray diffraction results all suggest that conformational changes may be occurring in the protein.
SOLVENT INFLUENCES ON THE SINGLET QUENCHING OF CHLOROPHYLLaBY 2, 5‐DIMETHYL‐p‐BENZOQUINONE
Authors: NATARAJAN L. V. , RICKER JANET E. , BLANKENSHIP ROBERT E. , CHANG RAYMOND
Published: January 2008

Abstract—The quenching of chlorophyllaexcited singlet states by 2.5‐dimethyl‐p‐benzoquinone has been investigated in solvents of varying viscosity and polarity. The observed singlet lifetimes showed little variation in several hydrocarbon solvents. Stern‐Volmer constantKdepends on the viscosity of the solvent, although cyclic and straight‐chain hydrocarbons behave somewhat differently. The decrease of theKvalues with increase of viscosity suggests that the quenching mechanism is at least partly dynamic, although there is evidence for static quenching as well. The influence of solvent polarity on theKvalues was found to be insignificant, which is consistent with a very short‐lived ion pair intermediate formed by electron‐transfer quenching.
SHORT‐TERM ADAPTATION OF HIGHER PLANTS TO CHANGING LIGHT INTENSITIES AND EVIDENCE FOR THE INVOLVEMENT OF PHOSPHORYLATION OF THE LIGHT HARVESTING CHLOROPHYLLalbPROTEIN COMPLEX OF PHOTOSYSTEM II
Authors: Dau Holger , Canaani Ora
Published: January 2008

Abstract

The short‐term adaptation of intact leaves to an increase in light intensity was studied by an analysis of chlorophyll fluorescence and oxygen evolution monitored by photoacoustics. An increase in light intensity led to an oxygen “gush”. This “gush” was followed by a large (up to 120%) biphasic increase in the yield of oxygen evolution characterized by a fast phase (T = 0.5–2 min) and a slow phase (T = 4–20 min). The fast phase of the increase in oxygen yield was coupled to a decrease of fluorescence, whereas the slow phase was accompanied by a parallel fluorescence increase. A comparison of fluorescence parameters with oxygen yield indicates that the slow phase of the increase in oxygen yield was coupled to an increase in the antenna size of photosystem II. The slow phase was not inhibited by the uncoupler Nigericin but it was absent in chlorophyll‐b‐less barley mutants dencient in the light harvesting chlorophylla/bprotein complex of photosystem II (LHC II). These experiments indicate that changes in the LHC II mediated energy distribution, which occur in the time‐range of several minutes, are involved in the adaptation to changing light intensities. Moreover, electrophoretic analysis of32P orthophosphate labeled leaf discs adapted to low and high light intensities suggests that the slow phase of the increase in oxygen evolution involves dephosphorylation of the 25 kDa polypeptide of LHC II, by a small extent of 12%. The trigger for the slow phase of the increase in oxygen yield does not involve the oxidation of the plastoquinone pool. It was found that in response to the increased light intensity, the plastoquinone pool became more reduced as judged by model calculations. Experiments with the uncoupler Nigericin suggest that the control of the slow phase of adaptation to increased light intensity was also not exerted by the pH gradient across the thylakoid membrane.

The similarities between the adaptation to increased light intensity and the state II to state I transition suggest that both adaptation phenomena involve LHC II dephosphorylation possibly triggered by the cytochromeb6/fcomplex.
DIBUCAINE FLUORESCENCE and LIFETIME IN AQUEOUS MEDIA AS A FUNCTION OF pH*
Authors: Vanderkooi Garret
Published: January 2008

Abstract— The absorption and fluorescence spectra and fluorescence lifetimes of the local anesthetic dibucaine (2‐butoxy‐N‐[2‐(diethylamino) ethyl]‐4‐quinoline carboxamide) are reported as a function of pH in aqueous media. The fluorescence emission maxima are at 400 nm in neutral solution, 397 nm in alkali, and 454 nm in acid. The fluorescence is strongest and has the longest lifetime in neutral solution; the quantum yields are 0.25, 0.033, and 0.032, and the lifetimes (determined by the phase shift method) are 3.29, 0.60, and 1.37 ns, for the neutral, alkaline, and acid solutions, respectively. The pKoi the tertiary amine group was determined by fluorescence intensity and lifetime measurements to be 8.95, and the pK of the aromatic nitrogen was found to be 1.80 ± 0.03 by absorption and fluorescence intensity measurements. Phase and modulation lifetimes differed in the manner expected for a two lifetime system in the pH titration range of the tertiary amine, but gave anomalous results in the titration range of the aromatic nitrogen.
UV‐INDUCTION OF SOS RESPONSES IN Staphylococcus epidermidis: CHARACTERISTICS OF THE PROCESS
Authors: Silva B. S. , Leitato A. C.
Published: January 2008

Abstract— Lysogenic induction, Weigle reactivation (WR) and Weigle mutagenesis (WM) induced by UV radiation were studied using the wild type Staphylococcus epidermidis W5 and its u> phage. The difference in UV sensitivity between the lysogenic and non‐lysogenic strains of S. epidermidis is extremely large when compared with wild type non‐lysogenic and lysogenic strains of Escherichia coli. The kinetics of prophage liberation by the lysogenic culture of 5. epidermidis are faster than those described for E. coli. The UV‐fluences which result in the maximum lysogenic induction, WR and WM are much lower than those described for E. coli. The maximum WR and WM are obtained immediately after the irradiation (within the 15 min allowed for phage adsorption). We suggest that in S. epidermidis the basal level of RecA protein can promote the efficient induction of SOS functions.
FAR UV IRRADIATION OF DNA IN THE PRESENCE OF PROTEINS, AMINO ACIDS OR PEPTIDES
Authors: Larcom L. L. , Rains C. A.
Published: January 2008

Abstract—The DNA of bacteriophage SP02c12 was subjected to 254 nm irradiation in solutions containing lysozyme or histone. In these solutions, the protein‐DNA mass ratios and the ionic strengths of the solvents were varied to change the amount of protein associated with the DNA. Lysozyme‐DNA binding constants were measured under the same conditions. The sensitivity of phage DNA to biological inactivation by UV increased as the amount of lysozyme bound per DNA strand increased. Although binding constants could not be measured for the DNA‐histone interaction, this protein had a protective effect which was greater under conditions which cause enhanced binding. No crosslinking of either protein could be detected even at doses ten‐fold greater than those giving a surviving fraction of 0.01.

Irradiation was also performed in the presence of various amino acids and short peptides. These were chosen to include amino acids which: (1) are positively charged, (2) absorb UV of this wavelength or (3) form UV‐induced crosslinks to DNA. None of the amino acids tested affected sensitivity of the DNA to biological inactivation. Peptides containing a UV‐absorbing amino acid and a positively charged amino acid enhanced sensitivity. For each of these peptides, a mixture of the constituent amino acids had the same effect as the peptide itself. Under the conditions used, no evidence for formation of DNA‐amino acid crosslinks was found. The results indicate that proteins and peptides can sensitize DNA to UV inactivation by mechanisms other than covalent crosslink formation. Such mechanisms could include energy or electron transfer or alterations in the conformation of the DNA.
METHYLALLOPSORALEN‐THYMINE 3,4‐ and 4',5'‐MONOADDUCTS FORMED IN THE PHOTOREACTION WITH DNA
Authors: Caffieri Sergio , Rodighiero Paolo , Vedaldi Daniela , DallAcqua Francesco
Published: January 2008

Abstract—Two new allopsoralens, i.e. 4,7.5'‐trimethylallopsoralen and 4,7,4'‐trimethylallopsoralen have been irradiated (365 nm) in the presence of DNA. The DNA so treated was hydrolyzed and among the products of its hydrolysis new 3,4‐ and 4',5'‐monocycloadducts between the two furocoumarins and thymine have been isolated. The monoadducts have been characterized on the basis of their spectroscopic properties, of their capacity to undergo photoreversion forming the parent compounds and of the NMR data. Acis‐synconformation has been suggested for both 3,4‐ and both 4',5'‐monoadducts.
PHOTOREACTIVATION BY TRIPLET FLAVIN and PHOTOINACTIVATION BY SINGLET OXYGEN OFNeurospora crassaNITRATE REDUCTASE*
Authors: Fritz Bernhard J. , Ninnemann Helga
Published: January 2008

Abstract—In the present paper the mechanism of photoreactivation and photodestruction of partially purified nitrate reductase fromNeurospora crassawas investigated. For both photoreactions exogenous flavin was needed; the rates of the photoreactions depended on the concentration of free flavin in the irradiated sample. Their efficiency as photoreceptors increased in the sequence FAD–FMN–riboflavin. No effect of enzyme‐bound flavin as photoreceptor was found in these photoreactions. Photoreactivation of nitrate reductase inactivated by reduction in the presence of KCN is due to its reaction with flavins in their triplet state. Photodestruction is due to singlet oxygen generated from triplet flavin in the presence of oxygen. Rate constants are estimated to bek =1–5 × 10‐1M‐1s‐1for the reaction of nitrate reductase with the flavin triplet (photoreactivation) andk= 5 × 10‐1M‐1s‐1for the reaction with singlet oxygen (photodestruction).
ULTRAVIOLET RADIATION STIMULATES THE RELEASE OF ARACHIDONIC ACID FROM MAMMALIAN CELLS IN CULTURE*
Authors: Leo Vincent A. De , Hanson Deborah , Weinstein I. B. , Harber Leonard C.
Published: January 2008

Abstract— C3H 10T½ cells in culture were prelabelled with [3H]arachidonic acid and exposed to UVB radiation. Almost immediately after irradiation cells released labelled arachidonate metabolites into media in a dose dependent manner. This release was inhibited by removing calcium ions from the system and by the addition of dexamethasone and parabromophenacyl bromide to the system. This suggests that the UVB stimulated release of arachidonic acid from membrane phospholipids is, in part, mediated by a phospholipase A2 enzyme system. Thin layer chromatographic examination of media extracts revealed a dose dependent UVB stimulation of prostaglandin production by cultured cells.
STOICHIOMETRY and KINETICS OF PROTON RELEASE UPON PHOTOSYNTHETIC WATER OXIDATION
Authors: Förster Verena , Junge Wolfgang
Published: January 2008

Abstract—We studied the magnitude and the rise kinetics of proton release into the interior of thylakoids by flash spectrophotometty with neutral red as pH indicator. Excitation of dark‐adapted thylakoids by a series of between 4 and 11 flashes produced a complex pattern of proton release into the thylakoid lumen. Proton release upon each flash was time resolved.

A slow component of proton release oscillated weakly in magnitude with period of two as function of flash number. It exhibited a half‐rise time of approximately 20 ms from the very first flash on, and it was abolished by inhibitors of plastohydroquinone oxidation. This component was attributed to the oxidation of plastohydroquinone by PS Iviathe Cytb6/f complex.

Additionally, rapid and multiphasic proton release was observed with half‐rise times of less than 2 ms which exhibited a pronounced and damped oscillation with period of four as function of flash number. This rapid proton release was attributed to water oxidation. A detailed kinetic analysis suggested that proton release occurred with the following stoichiometry and with the following half‐rise times during the transitions S1Si+1of water oxidation: 1 H+(250 μs, S0→1): 0 H+(S1→ S2):1 H+(200 μs, S2→S3):2 H+(1.2 ms, S3→ S4→ S0).Proton release and proton rebinding upon oxidation and reduction of the intermediate electron carrier Z, respectively, may have influenced the kinetics of the respective proton yields but not the stoichiometric pattern.
MECHANISM OF THE PHOTOHYDRATION OF PYRIMIDINES: A FLASH PHOTOLYSIS STUDY*
Authors: Garner A. , Scholes G.
Published: January 2008

Abstract— Based on comparisons between the microsecond flash photolysis of uracil and substituted uracils and the radiation chemistry of the corresponding 5,6‐dihydro‐2,4‐dioxopyrimidines, it is proposed that the mechanism of photohydration of pyrimidine bases involves the formation of a pyrimidine carbocation. The effects of substitution in the pyrimidine ring and of pH are consistent with a proton transfer from water to the excited singlet state at theC–5 position of the pyrimidine ring. The resultant carbocation is thought to undergo solvolysis to form the photohydrate or eliminate a proton at N‐l producing an intermediate isomeric form of the pyrimidine (isopyrimidine) which re‐arranges to the parent pyrimidine by a first‐order process.
SEPARATION AND PHOTOTOXICITYIN VITROOF SOME OF THE COMPONENTS OF HAEMATOPORPHYRIN DERIVATIVE
Authors: Cowled P. A. , Forbes I. J. , Swincer A. G. , Trenerry V. C. , Ward A. D.
Published: January 2008

Abstract—The separation and fractionation of some of the components of haematoporphyrin derivative by chemical extraction, gel chromatography and membrane filtration are described. The composition of the various fractions and the purity of the individual porphyrins can be assessed by high performance liquid chromatography. Porphyrins containing vinyl side chains show an unusual ability to form relatively stable aggregates of apparently high molecular weight. The effect is most pronounced with protoporphyrin and is not observed with haematoporphyrin which has no vinyl side chains. These aggregates can be separated by gel chromatography or membrane filtration from non (or less) aggregated material. The aggregates show greaterin vitrocytotoxicity than the other fractions.
THE BLUE LIGHT GRADIENT IN UNILATERALLY IRRADIATED MAIZE COLEOPTILES: MEASUREMENT WITH A FIBER OPTIC PROBE
Authors: Vogelmann T. C. , Haupt W.
Published: January 2008

Abstract— The blue light (450 nm) gradient was measured with a fiber optic microsensor in etiolated maize coleoptiles that were irradiated unilaterally. Patterns of transmitted and scattered light across the shoot were related to the morphology of the coleoptile and varied greatly between the coleoptile base, mid‐region and tip. In the coleoptile base, light was scattered equatorially around the coleoptile sheath so that there was more light on the shaded side of the sheath than in the shaded side of the primary leaves. In the hollow mid‐region there were strong reflecting boundaries at the air‐coleoptile interfaces, which resulted in step like transitions in the light gradient. In the coleoptile tip, there was a steep, near‐linear gradient of blue light, with the greatest amount of light on the irradiated side. There was no evidence that the coleoptile tip acts as a lens or that there are anomalies that result in more light on the shaded than irradiated side. Immediately beneath the irradiated surface, the space irradiance was about twice the fluence rate of the light beam. The magnitude of the light gradient was 4:1 between the irradiated and shaded side of the mid‐region and tip and 8:1 for the coleoptile base.
ENERGY TRANSFER FROM PHYCOBILINS TO CHLOROPHYLL a IN HEAT‐STRESSED CELLS OF Anacystis nidulans: CHARACTERIZATION OF THE LOW TEMPERATURE 683 nm FLUORESCENCE EMISSION BAND*
Authors: Mohanty Prasanna , Hoshina Satoshi , Fork David C.
Published: January 2008

Abstract— Heat‐induced changes of the characteristics of fluorescence spectra of Anacystis nidulans cells were studied after 39°C‐grown cells were heated at 55°C. Heat‐treatment of the cells induced no changes in the absorption properties or photosystem I‐catalyzed cytochrome oxidation, but induced a dramatic change in the fluorescence characteristics of the cells. The low temperature fluorescence emission spectra of heated cells showed a large increase of fluorescence emission at683–685 nm (F683) and at 695 nm, while the bands at 660 nm (allophycocyanin) and at 718 nm (chlorophyll a of photosystem I) were not affected when the cells were excited with light absorbed by phycobilins. When the cells were heated for various periods, a progressive increase of the intensity of F683 occurred with the loss in oxygen evolution capacity. The increase of the F683 band was observed prior to the increase of the F695 band. Quenching of emission spectra by the addition of quinones indicates that the F683 band emanated mainly from a long wavelength form of allophycocyanin. Excitation spectra of heated cells measured at 77 K showed that light absorbed by phycobilins was effective in exciting F685, F695, and F715 emission. A possible energy distribution pathway in Anacystis nidulans is discussed.
XERODERMA PIGMENTOSUM COMPLEMENTATION GROUP F: MORE ASSIGNMENTS AND REPAIR CHARACTERISTICS
Authors: Fujiwara Y. , Uehara Y. , Ichihashi M. , Nishioka K.
Published: January 2008

Abstract— The specific heterodikaryon complementation method enabled us to assign three patients with mild xeroderma pigmentosum (XP) symptoms (XP25KO, XP27KO, XP28KO) to complementation group F. UV‐induced unscheduled DNA synthesis (UDS) remained unnormalized in the heterodikaryons between either of the above three XP strains and the reference group F XP3YO. All these particular XP strains as well as XP3YO exhibited an equally low level of10–15% UDS by a 3 h [3H]‐thymidine labeling following 10 J/m2 254 nm UV, while they attained 60% UDS of normal at an extended time of 25 h. The present group F strains were 3 and 1.5 times as sensitive to the lethal effect of UV as normal and XP group E cells, respectively, based on the mean lethal dose (Do) comparison. Normal cells had the biphasic time‐UDS kinetics of early rapid and late slow repair. Characteristically, however, all of the present group F strains were defective in only early rapid repair, but normally proficient in slow repair.
A MODEL FOR THE ORIGIN OF PHOTOSYNTHESIS–III. THE ULTRAVIOLET PHOTOCHEMISTRY OF UROPORPHYRINOGEN*
Authors: Mercer‐Smith Janet A. , Raudino Anthony , Mauzerall David C.
Published: January 2008

Abstract— The photochemical ramifications of the high ultraviolet flux on the primordial earth prior to the formation of the ozone layer have been considered in a study of the ultraviolet photochemistry of uroporphyrinogen (urohexahydroporphyrin), a colorless compound which absorbs strongly at wavelengths less than 220 nm. Urohexahydroporphyrin was investigated since it is the first macrocycle formed on the biosynthetic pathway of chlorophyll and can be used to test the hypothesis that the biosynthetic pathway to chlorophyll recapitulates the evolutionary history of photosynthesis.

When urohexahydroporphyrin is illuminated in aqueous anaerobic solution, hydrogen gas is produced. More hydrogen gas is produced in the presence of a colloidal platinum catalyst. The products of the photooxidation of urohexahydroporphyrin are urotetrahydroporphyrin (uroporphomethene) and uroporphyrin. This research shows how the oxidation of uroporphyrinogen to uroporphyrin, the first biogenetic porphyrin, could have occurred anaerobically and abiotically on the primordial earth.
REPAIR IN Escherichia coli OF A PSORALEN‐DNA INTERSTRAND CROSSLINK SITE SPECIFICALLY INTRODUCED INTO T410A411 OF THE PLASMID pUC 19
Authors: Zhen Wei‐Ping , Jeppesen Claus , Nielsen Peter E.
Published: January 2008

Abstract— Escherichia coli was transformed with a pUC 19 plasmid which contained a 4,5′,8‐trimethylpsoralen cross‐link specifically at position T410‐A411, and transformants in which the cross‐link had been repaired were scored on the basis of ampicillin resistance. Repair was only seen after induction of the SOS‐system by shortwave ultraviolet irradiation. The repair efficiency was 6%, and of 100 colonies analyzed only two was found to be mutated at the cross‐linked site: a T‐A transversion was observed at position 410. A repair mechanism which does not involve recombination is proposed.
DISTRIBUTION OF PORPHYRINS IN THE VARIOUS COMPARTMENTS OF UNILAMELLAR LIPOSOMES OF DIPALMITOYL‐PHOSPHATIDYLCHOLINE AS PROBED BY FLUORESCENCE SPECTROSCOPY
Authors: Ricchelli Fernanda , Jori Giulio
Published: January 2008

Abstract—The spectroscopic properties of hematoporphyrin, hematoporphyrin‐dimethyl ester, uroporphyrin and uroporphyrinoctamethyl ester, incorporated into unilamellar liposomes of dipalmitoylphos‐phatidylcholine, have been studied with the aim to assess the distribution of porphyrins within the various liposomal compartments.

The results obtained indicate that the highly hydrosoluble uroporphyrin is partitioned in the endoliposomal aqueous pool while its octamethylester is homogeneously distributed in the inner lipid monolayer. Hematoporphyrin and its dimethylester show an heterogeneous distribution within the phospholipid bilayer. At T = 25°C these porphyrins are preferentially located in the outer phospholipid monolayer.

Detailed studies on hematoporphyrin indicate that the distribution between the inner and outer phospholipid monolayer is a function of temperature and liposome dimensions. In particular, the increase of temperature above the critical temperature for the liquid‐gel phase transition of the liposomes causes a partial shift of the porphyrin molecules toward the inner phospholipid monolayer. Moreover, the increase of liposome dimensions leads to a greater accessibility of porphyrin to the external medium.
INVESTIGATION OF CHROMOPEPTIDES FROM C‐PHYCOCYANIN BY UV‐VIS ABSORPTION, EMISSION AND CIRCULAR DICHROISM SPECTROSCOPY
Authors: Schneider Siegfried , Köst‐Reyes Eliana , Scharnagl Christina , Geiselhart Peter
Published: January 2008

Four different chromopeptides were isolated after digestion of C‐phycocyanin with pepsin. Their UV‐vis absorption and circular dichroism spectra were measured at two different pH values without and with urea present in the buffered solutions. For one chromopeptide, fluorescence spectra and the kinetics of fluorescence decay were studied in more detail. The results are discussed in comparison with quantum‐mechanical model calculations. It is concluded that due to the interaction between the oligopeptide chain and the chromophore, the latter is present as a mixture of helical and semi‐extended forms, respectively.
PHOTORESPONSES OF SEMICONDUCTOR POLYCRYSTALLITES SEPARATING TWO AQUEOUS SOLUTIONS
Authors: Tien H. Ti , And Z.‐C. Bi , Tripathi A. K.
Published: January 2008

Solar cells using polycarbonate membranes, with CdS deposited on them, were made by a very simple way; the CdS‐containing membrane separates a Lucite cell into two compartments. On illumination, about 150 mV photovoltage (Vop) and 0.5 μA cm‐2photocurrent (Isc) could be produced; one side of the membrane acted as photoanode, and the other side as photocathode. By means of coating Victoria Blue B (VBB) onto the membrane before CdS deposition, the maximumVopandIscof the CdS‐deposited membrane could reach 500 mV and 3.0 (μA cm‐2, respectively. A mixture of CdS and CdSe deposited membrane has also been tested and found to have both the advantages of high photovoltage (over 400 mV) and good stability after modification. Even more interesting results were also obtained with CdSe pellets in place of the CdS‐deposited membrane, in whichVopandIscof the cell were 1.2 V and 6 mA cm‐2, respectively. The essential aspect of the system, modelled after the photosynthetic thylakoid membrane, contains an asymmetrical, ultrathin semiconductor crystallite layer separating two aqueous solutions.
EXTENSIVE CROSSLINKING BETWEEN SUBUNITS OF OLIGOMERIC PROTEINS INDUCED BY FUROCOUMARINS PLUS UV‐A IRRADIATION
Authors: Schiavon O. , Veronese F. M.
Published: January 2008

Abstract— Exposure of oligomeric proteins to UV‐A irradiation in the presence of various furocoumarins results in extensive crosslinking of the enzyme subunits. The mechanism by which these covalent bridges are formed does not involve the furocoumarin moiety as the crosslinking agent, but depends upon oxidative processes, mainly involving singlet oxygen and radical mediated processes not involving oxygen. The formation of crosslinks is not per se responsible for the inactivation of enzymes since in glutamate dehydrogenase the two reactions proceed at the same rate, in catalase it is not accompanied by enzyme inactivation and in alcohol dehydrogenase the inactivation rate is higher than polymerization.
PHOTOCHEMICAL SENSITIZATION BY AZATHIOPRINE AND ITS METABOLITES—I. 6‐MERCAPTOPURINE
Authors: Hemmens Violet J. , Moore Douglas E.
Published: January 2008

Abstract— Azathioprine is used as an immunosuppressant for renal transplant recipients, but is frequently associated with severe skin cancer as a side effect. 6‐Mercaptopurine, the primary metabolite of azathioprine. absorbs strongly in the UVA region and displays substantial photochemical reactivity. The primary photochemical processes in aqueous solution are triplet state formation and photoionization, as shown by flash photolysis. In oxygenated solution, singlet oxygen and superoxide are produced, and ground state 6MP appears to react with these species. Glutathione inhibits this reaction and is itself oxidized. In deoxygenated solution, reactions implicating the thiyl radical and hydrogen atom and electron transfer occur as shown by reaction with histidine and p‐nitrosodimethylaniline. Nitro Blue Tetrazolium or acrylamide.
EVALUATION OF STRUCTURALLY‐RELATED PHENOLS FOR ANTI‐PHOTOCARCINOGENIC AND PHOTOPROTECTIVE PROPERTIES
Authors: Black Homer S. , Tigges Jenny
Published: January 2008

Abstract—Butylated hydroxytoluene (BHT) has previously been shown to provide protection against UV‐mediated erythema, carcinogenesis, and induction of epidermal ornithine decarboxylase (ODC). Butylated hydroxytoluene is but one compound of a class of organic chemicals, the phenols, that demonstrates antioxidant properties. On the basis of structural characteristics, the phenolic compounds butylated hydroxyanisole (BHA), propyl gallate, and vanillin were compared to BHT for antiphotocarci‐nogenic activity. SKH‐Hr‐1 female mice were fed diets containing 0.5% (wt/wt) BHT, BHA, vanillin or 0.3% propyl gallate. The animals received constant, daily (5 days/week) suberythemic levels of UVB radiation from Westinghouse BZS‐WLG lamps. Radiation was discontinued when 25 sunburn units (SBUs) had been delivered at week eleven. Animals were evaluated weekly for tumor latency and multiplicity. Of the four phenols tested, only BHT conveyed significant inhibition of both carcinogenic parameters—increasing latency by 5.2 weeks and reducing tumor multiplicity by 60%. Vanillin significantly reduced tumor multiplicity (48%). BHA and propyl gallate were without effect. Because ODC has been considered a requisite step in carcinogenesis, ODC activity was assayed to determine whether its induction might serve as a rapid screen for potential anti‐carcinogenic phenols. Animals were fed the respective phenol‐containing diets for two weeks, exposed to 0.45 J/cm/of UVB from FS‐20 lamps, and epidermal extract assayed for ODC activity 28 h post‐irradiation. Both BHT and BHA significantly inhibited ODC induction, the former being most effective. Vanillin and propyl gallate were without effect. These data indicate that neither antioxidant or lipophilic properties, nor thetert‐butyl substituent common to both BHT and BHA, are sufficient determinants of anti‐photocarcinogenic activity. Nor does it appear that inhibition of ODC induction is an adequate indicator of such activity.
PHOTOADDITION OF CHLORPROMAZINE TO GUANOSINE‐5′‐MONOPHOSPHATE
Authors: Ciulla Thomas A. , Epling Gary A. , Kochevar Irene E.
Published: January 2008

Abstrart—The photochemistry of chlorpromazine (CPZ) with guanosine‐5′‐monophosphate (GMP) was studied as a model for the photoaddition of CPZ to DNA. Irradiation of CPZ with calf thymus DNA produced a product emitting at 520 nm, whereas with GMP emission was at 495 nm. HPLC separation of photolysis mixtures of [3H]CPZ with GMP and [14C]GMP with CPZ indicated that three photoadducts were formed. One of the adducts fluoresced at 500 nm and appeared to be the product detected but not separated by Fujita et al. (Photochem. Photobiol. 1981, 34, 101–105). A second adduct emitted at 460 nm, and the third was nonfluorescent. The photoadduct emitting at 500 nm was characterized by UV, fluorescence, and NMR to be an adduct from coupling of the C‐8 position of guanine to the C‐2 position of the phenothiazine ring of CPZ. The cation radical of CPZ (CPZ +) does not appear to be an intermediate since enzymatically generated CPZ + formed a product that eluted with a retention time close to that of the photoadducts, but did not emit at 520 nm.
WAVELENGTH DEPENDENCE FOR ORNITHINE DECARBOXYLASE INDUCTION IN VIVO†
Authors: Kligman Lorraine H. , Kaidbey Kays H.
Published: January 2008

Abstract— The wavelength dependence for ornithine decarboxylase induction was investigated in vivo in the epidermis of albino hairless mice. A 4 cm2 area of dorsal skin was exposed to narrow wavebands (HPBW 6.6 nm) from a monochromator optically coupled to a 5 kW Xe arc source. Dose‐response studies were caried out at 260, 275, 290, 300 and 315 nm. The animals were sacrificed 24 h after irradiation and the epidermis separated and assayed for ODC activity. A dose‐related induction of ODC was observed at 260, 275, 290 and 300 nm. No stimulation was observed following exposure to 315 nm (maximal dose 6400 J/m2). ODC induction appeared to be linearly related to log UV dose within the dose range of 200 to 1600 J/m2. The dose required to induce an approximately 50‐fold increase in activity (1.5 nmol CO2/h/mg protein) was determined from the dose‐response regression lines and used to construct an action spectrum. Peak effectiveness occurred at 290 nm, with a rapid loss after 300 nm. After correction for epidermal transmission, peak effectiveness was shown to occur around 260 nm.
PHOTOSENSITIZATION BY ANTITUMOR AGENTS—1. PRODUCTION OF SINGLET OXYGEN DURING IRRADIATION OF ANTHRAPYRAZOLES WITH VISIBLE LIGHT
Authors: Reszka Krzysztof , Tsoungas Petros G. , Lown J. William
Published: January 2008

Abstract— Oxygen consumption, photoinduced by visible light, and sensitized by novel anthrapyrazole antitumor agents has been observed. Generation of singlet oxygen upon irradiation of ethanolic solutions of the drugs with visible light (480–520 nm) was demonstrated using a specific 1O2 acceptor, 2.5‐dimethylfuran and a quencher, sodium azide. An electron paramagnetic resonance method was employed to measure the rate of oxygen consumption. Significant differences were found in the sensitizing properties among the anthrapyrazoles studied. Intramolecular hydrogen bonding within the chro‐mophore is one of the structural factors that determine the efficacy of a given anthrapyrazole in 1O2 generation
HORSE HEART CYTOCHROMEcAS AN ELECTRON ACCEPTOR FROM CHLOROPHYLL TRIPLET IN NEGATIVELY CHARGED LIPID BILAYER VESICLES*
Authors: Senthilathipan Velu , TOllin Gordon
Published: January 2008

Abstract—Cytochromechas been shown to bindviaelectrostatic interactions to egg phosphatidylcholine vesicles which contain 5–30 mol percent of negatively‐charged surfactant (dihexadecylphosphate) in a low ionic strength medium. Under these conditions the oxidized cytochrome can function as a direct one‐electron acceptor from membrane‐bound triplet state chlorophyll to produce chlorophyll cation radical and reduced cytochrome. Kinetic experiments using laser flash photolysis have demonstrated that triplet quenching and the yield of electron transfer products increase, and product lifetime decreases, with an increase in the magnitude of the negative charge on the vesicles, and with a decrease in the ionic strength of the medium. Both triplet quenching and product formation rates and yields showed saturation behavior as the cytochrome concentration was increased, and reached limiting values at 20–30μMcytochrome when the vesicle contained 20 mol percent of the negatively‐charged surfactant. This behavior is interpreted in terms of saturation of the vesicle surface binding sites. Under optimum conditions in this system, approximately 20% of the chlorophyll triplet molecules could be converted to electron transfer products which had a halftime for the reverse reaction of approximately 1.5 ms.
OXYGEN RADICALS MEDIATE CELL INACTIVATION BY ACRIDINE DYES, FLUORESCEIN, and LUCIFER YELLOW CH
Authors: Martin Joseph P. , Logsdon Naomi
Published: January 2008

Abstract Acridine dyes, fluorescein and lucifer yellow CH are fluorescent photosensitizers used experimentally to selectively stain and photodynamically destroy eukaryotic cells and subcellular structures. We have determined that the mechanism of light‐ and oxygen‐dependent inactivation of E. coli by these dyes involves oxygen radicals and hydrogen peroxide.

All of the dyes oxidized NAD(P)H† under illumination. Superoxide (O2−), detected as the superoxide dismutase (SOD)‐inhibitable reduction of ferricytochrome c, was a major product of the dye sensitized photooxidation.

Cationic acridine dyes penetrated the membranes of E. coli and were photoreduced intracellularly. Reduced dyes diffused back into the medium and mediated the reduction of extracellular ferricytochrome c. The anionic dyes fluorescein and lucifer yellow CH were unable to mediate extracellular cytochrome c reduction, indicating that these dyes were impermeable to the E. coli membranes. Acridine dyes, when illuminated, inhibited the growth of E. coli in a rich medium, and induced the synthesis of SOD. Fluorescein and lucifer yellow CH did not inhibit growth or induce SOD synthesis because they were unable to enter the cells.

Superoxide (O2−) and hydrogen peroxide (H2O2), generated by the enzyme xanthine oxidase were toxic to E. coli B. Inactivation by xanthine oxidase was partially inhibited by exogenous SOD and completely inhibited by exogenous catalase or SOD plus catalase. Similarly, exogenous SOD plus catalase protected against inactivation by acridines and fluorescein‐NADH or lucifer yellow CH‐NADH mixtures. Prior induction of superoxide dismutase and catalase in E. coli B significantly protected cells against a subsequent challenge by illuminated acridine dyes. SOD and catalase preinduction combined with additions of exogenous SOD and catalase completely protected E. coli B against photodynamic inactivation by acridine yellow. The hydroxyl radical scavengers, dimethyl sulfoxide, sodium benzoate and thiourea, protected E. coli B against photodynamic inactivation by acridine orange.

The results implicate O2−, H2O2, and the hydroxyl radical (OH‐) as underlying molecular agents of the phototoxicity mediated by acridine orange, acridine yellow, fluorescein and lucifer yellow CH.
A COMPARISON OF DOSIMETERS USED FOR SOLAR ULTRAVIOLET RADIOMETRY
Authors: Diffey B. L.
Published: January 2008

Abstract Radiometric measurements of terrestrial sunlight using three different types of broadband dosimeters were compared with equivalent integrated quantities obtained from simultaneous spectroradiometric measurements. Measurements were made at Durham, UK (55oN) during one day in mid‐summer and one day in the autumn. By this means it was possible to encompass a wide range of ultraviolet irradiances. There was close agreement between UV‐A irradiance measured using a broad‐band radiometer and determined spectroradiometrically over the whole range of irradiances, when allowance was made for the spectral sensitivity of the UV‐A radiometer. The agreement between erythemally‐effective irradiance determined spectroradiometrically and the response of a Robertson‐Berger meter showed some non‐linearity due to the mismatch between the erythema action spectrum and spectral response of the sensor. There was a similar disparity in agreement between erythemally‐effective dose determined spectroradiometrically and the response of polysulphone film for similar reasons. Nevertheless it is concluded that if these latter two dosimeters are calibrated using sunlight, or a solar simulator, as the source, they can yield data which are sufficiently reliable for many applications.
UV‐B RADIATION EFFECTS ON PHOTOSYNTHESIS, GROWTH and CANNABINOID PRODUCTION OF TWO Cannabis sativa CHEMOTYPES
Authors: Lydon John , Teramura Alan H. , Coffman C. Benjamin
Published: January 2008

The effects of UV‐B radiation on photosynthesis, growth and cannabinoid production of two greenhouse‐grown C. sativa chemotypes (drug and fiber) were assessed. Terminal meristems of vegetative and reproductive tissues were irradiated for 40 days at a daily dose of 0, 6.7 or 13.4 kJ m‐2 biologically effective UV‐B radiation. Infrared gas analysis was used to measure the physiological response of mature leaves, whereas gas‐liquid chromatography was used to determine the concentration of cannabinoids in leaf and floral tissue.

There were no significant physiological or morphological differences among UV‐B treatments in either drug‐ or fiber‐type plants. The concentration of Δ9‐tetrahydrocannabinol (Δ9‐THC), but not of other cannabinoids, in both leaf and floral tissues increased with UV‐B dose in drug‐type plants. None of the cannabinoids in fiber‐type plants were affected by UV‐B radiation.

The increased levels of Δ9‐THC in leaves after irradiation may account for the physiological and morphological tolerance to UV‐B radiation in the drug‐type plants. However, fiber plants showed no comparable change in the level of cannabidiol (a cannabinoid with UV‐B absorptive characteristics similar to Δ9 THC). Thus the contribution of cannabinoids as selective UV‐B filters in C. sativa is equivocal.