bluuebunny/crossref_metadata_2025 huggingface dataset:
OXIDATIVE DEGRADATION OF LIGNIN BY PHOTOCHEMICAL AND CHEMICAL RADICAL GENERATING SYSTEMS
Authors: Gold Michael H. , Kutsuki Hidetoshi , Morgan Meredith A.
Published: January 2008

Abstract—

Oxidation of specifically radiolabeled 14C‐lignins by UV/H202. Fenton's reagent, photosesitizing riboflavin. UV‐ and γ‐irradiation was examined. In the presence of UV/H2O2, a hydroxyl radical (·OH) generating system. 14C‐methoxy. 2‐[14C‐sidechain] and 14C‐ring labeled lignin were rapidly and extensively degraded as measured by gel filtration of the reaction products on Sephadex LH‐20. This suggested that exposure to OH leads to rapid, nonspecific lignin degradation. Rapid degradation of 14C‐methoxy, 2‐[14C‐sidechain] and 14C‐ring labeled lignin also occurred in the presence of the ·OH generating system, Fenton's reagent, confirming the primary role of ·OH in these reactions. Photosensitizing riboflavin, also capable of effecting transformation of organic compounds via Type I hydrogen radical abstractions, caused extensive oxidative degradation of 14C‐methoxy labeled lignin and significant degradation of 2‐(14C‐sidechain] and 14C‐ring labeled lignin. In addition, UV‐ and γ‐irradiation caused slower but extensive degradation of the polymers, probably via radical type mechanisms. All of these results indicate that ·OH as well as organic radical generating systems are effective agents for the purpose of degrading this heterogeneous, optically inactive and random biopolymer.
DETERMINATION OF THEIN VIVOABSORPTION AND PHOTOSYNTHETIC PROPERTIES OF THE LICHENAcarospora schleicheriUSING PHOTO ACOUSTIC SPECTROSCOPY
Authors: O'Hara Ellen P. , Tom Roderick D. , Moore Thomas A.
Published: January 2008

Abstract—

Photoacoustic spectroscopy was used to determine thein vivospectra of the stratified components of the lichenAcarospora schleicheri.There were three pigmented layers observed by the photoacoustic method: an absorption band associated with the pigment rhizocarpic acid, a bulk cytochrome absorption, and the absorption of the algal chloroplast. Due to the different absorption properties of these distinct layers, the photoacoustic technique was able to monitor the physical effect of hydration on the lichen. Hydration of the lichen reduced the scatter of the sample, increasing the effective incident light intensity within the sample. Hydration also resulted in an increase in the optical absorption coefficient of the algal layer, which was interpreted as a movement of the algal chloroplast in response to low light fluence and hydrated conditions.

The photoacoustic technique was also used to monitor the relative photosynthetic activity of the algae within the lichen in a hydrated and dehydrated state. The photosynthetic assay could detect photosynthetic activity in the hydrated state but not in the dehydrated state. In addition, the photosynthetic response was found to be induced and repressed with light and dark periods respectively and its detection was limited at high frequencies by the damping of the thermal wave from the algal layer.
THE ROLE OF A PHOTOCHEMICAL REACTION ON THE DEACTIVATION OF EXCITED 4,5′,8‐TRIMETHYLPSORALEN IN ETHANOL
Authors: Ishikawa Mitsuru , Kikuchi Koichi , Kokubun Hiroshi
Published: January 2008

Abstract—

The transient absorption of an intermediate R which is formed from an excited state higher than the lowest triplet state was observed in an ethanol solution of 4,5′,8‐trimethylpsoralen (TMP). The temperature effects on the fluorescence yield φF for TMP and on the initial absorbance DR of R were studied and it was found that DR increases with increasing temperature whereas φF decreases. These results indicate that a photochemical reaction plays an important role on the deactivation of TMP in the excited singlet state
THE DECONVULATION OF ABSORPTION SPECTRA OF GREEN PLANT MATERIALS—IMPROVED CORRECTIONS FOR THE SIEVE EFFECT
Authors: Latimer Paul
Published: January 2008

Abstract—

The extinction (absorbance, optical density) of a suspension of algal cells or chloroplasts, etc. can be an a linear function of the absorption coefficient of the cell contents, even when the effects of scattering are negligible. The deviation from linearity is Duysens' sieve effect. The heights of absorption maxima of suspensions are depressed as compared with those of the “particle” contents. Duysens proposed an expression for correcting for this distortion; that expression proves to be a special approximate case of a more general one. This paper proposes an improved method of correction which utilizes this general expression, conventional expressions for particle absorption based on the Lorentz‐Mie and Aden and Kerker equations for scattering and absorbing, and iterative methods for numerically deducing particle absorption coefficients from suspension parameters. The procedure is illustrated by applying it to previous experimental spectra of Chlorellu cells and spinach chloroplasts.
PRIMARY PROCESSES IN THE LASER FLASH PHOTOLYSIS AND PULSE RADIOLYSIS OF l‐EPHEDRINE
Authors: Navaratnam Suppiah , Land Edward J. , Parsons Barry J. , Ahmad Iqbal , Phillips Glyn O.
Published: January 2008

Abstract— Transient absorption spectra produced by laser flash‐photolysis of an aqueous solution of ephedrine have been measured under a variety of conditions. Ephedrine was found to photoionise via a biphotonic process. The apparent yield of photoionisation increases with lowering of pH, a value of 8.8 being found for the pKa associated with this change. The cation radical absorption spectrum has been determined using the techniques of both pulse radiolysis and laser flash photolysis. The extinction coefficient of the cation at 295 nm was determined to be 1.37 × 104 dm3 mol‐1 cm‐1 and 1.2 × 104 dm3 mol‐1cm‐1 by the two techniques, respectively, at pH 11. It is also shown that the rate constant for electron abstraction by the azide radical to form the ephedrine cation is controlled by protonation of the amine group in the side chain. The ephedrine anion radical spectrum and its extinction coefficient at 305 nm were also determined. The excited states responsible for photoionisation and photodegradation are discussed.
ELECTRON SPIN RESONANCE OF MELANIN FROM HAIR. EFFECTS OF TEMPERATURE, pH AND LIGHT IRRADIATION
Authors: Arnaud R. , Perbet G. , Deflandre A. , Lang G.
Published: January 2008

Abstract— The variation with temperature, pH and light of the ESR signal of hydrated melanin powders from Japanese black hair has been studied. An explanation of the results is proposed on the basis of quinhydrone type complexes and of acid‐base equilibria of melanin and its semiquinone radicals. During exposure to light of wavelengths 254–600 nm, both stable and unstable radicals have been observed. The action spectrum for the formation of stable melanin radicals has been determined.
KINETICS OF BACTERIAL BIOLUMINESCENCE AND THE FLUORESCENT TRANSIENT
Authors: Matheson I. B. C. , Lee John
Published: January 2008

Abstract— The addition of FMNH2 to Vibrio harveyi luciferase at 2°C in the presence of tetradecanal results in the formation of a highly fluorescent transient species with a spectral distribution indistinguishable from that of the bioluminescence. The bioluminescence reaches maximum intensity in 1.5 s and decays in a complex manner with exponential components of 10‐1s‐1, 7 × 10‐3s‐1, and 7 × 10 4s‐1. The fluorescent transient rises exponentially at 7 × 10‐2s‐3 and decays at 3 × 10‐4s‐1. The slowest bioluminescence component, comprising the bulk of the bioluminescence, decays at twice the rate of the fluorescent transient under all variations of reaction conditions: concentration of reactants, temperature 2–20°C, and aldehyde chain length—decanal, dodecanal and tetradecanal. The activation energy for both the slowest bioluminescence decay and the transient fluorescence decay is 80 kJ‐mol‐1. An energy transfer scheme is proposed to explain the results where two distinct chemically energized species utilize the fluorescent transient as emitter for the slower bioluminescences, and for the faster process a fluorophore present in the protein preparation. Kinetic observations suggest that typical preparations of V. harveyi luciferase comprise 15% active protein.
DESTRUCTION OF MICROSOMAL CYTOCHROME P‐450 BY REACTIVE OXYGEN SPECIES GENERATED DURING PHOTOSENSITIZATION OF HEMATOPORPHYRIN DERIVATIVE
Authors: Dixit Rakesh , Mukhtar Hasan , Bickers David R.
Published: January 2008

Rat liver microsomal cytochrome P‐450 undergoes rapid destruction in the presence of hematoporphyrin derivative (HpD) and solar radiation (∼ 400 nm). Destruction of cytochrome P‐450 is associated with the formation of cytochrome P‐420 and significant loss of microsomal haem. Quenchers of singlet oxygen including 2,5‐dimethylfuran, histidine, ß‐carotene, and ascorbic acid and inhibitors of the hydroxyl radical such as benzoate, mannitol, and ethanol prevent deterioration of the microsomal haem‐protein, whereas superoxide dismutase and catalase are ineffective in this regard. These results indicate that generation of singlet oxygen during hematoporphyrin photosensitization is associated with destruction of microsomal cytochrome P‐450 and haem.
IN VIVO FLUORESCENCE SPECTROSCOPY OF CHLOROPHYLL IN VARIOUS UNRIPE AND RIPE FRUIT
Authors: Gross Jeana , Ohad Itzhak
Published: January 2008

—Low temperature (77 K) fluorescence emission spectra of slices obtained from the peel and various layers of the pericarp were recorded for fruits which remain green or undergo color break during ripening.

Fluorescence emission peaks characteristic of the photosystem II antennae (λF 686 nm) and reaction center (λF 696 nm), as well as of the photosystem I antenna (λF 730‐740 nm), were present in the peel and all parts of the green pericarp of ripe kiwi, avocado and cantaloupe, as well as in ripe tomato and tangerine after color break. The pattern of the fluorescence emission spectra of all samples except that of the kiwi fruit was similar to that obtained from green photosynthetic tissue of leaves, indicating a normal organization of the chlorophyll‐containing complexes of thylakoidal membranes. This pattern is characterized by a significantly higher emission at 730‐740 nm relative to that of the 696 and 686 nm peaks. In contradistinction, the fluorescence emission at 686 and 696 nm was higher than that at 730 nm in the kiwi fruit, indicating a reduction in the size of the photosystem I antenna chlorophyll. In the innermost yellowish layers of the kiwi pericarp, a further loss of this antenna occurred, as well as disorganization of the photosystem II complex. The above conclusions are suggested also by measurements of variable fluorescence kinetics.

The results presented here indicate that fluorescence spectroscopy might be used as a tool for the study of chlorophyll organization during the growth and ripening periods of fruit.
POSSIBLE INVOLVEMENT OF MEMBRANE DAMAGE IN THE IN ACTIVATION BY BROAD‐BAND NEAR‐UV RADIATION IN Saccharomyces cerevisiae CELLS
Authors: Ito Atsushi , Ito Takashi
Published: January 2008

Multiple cellular effects of near‐UV radiation (300‐380 nm) on inactivation, disruption of the permeability barrier and induction of gene conversion at the trp 5 locus were simultaneously measured in the same culture of a diploid strain of the yeast Saccharomyces cerevisiae in order to assess the critical lethal damage. Inactivation of exponential phase cells in water appeared to be closely related to the disruption of the permeability barrier. Inactivation and membrane damage were remarkably oxygen dependent, whereas the induction of genetic changes was very low and dependent much less on oxygen. The dependence on the temperature for inactivation and membrane damage was both low, conforming with the expectation that the processes are mainly photochemical and not enzymatic. These features are very contrasted with the characteristics of far‐UV radiation effects. Possible involvement of membrane damage in near‐UV inactivation of exponential phase yeast cells is discussed.
PICOSECOND FLUORESCENCE KINETICS and ENERGY TRANSFER IN THE ANTENNA CHLOROPHYLLS OF GREEN ALGAE*
Authors: Haehnel Wolfgang , Holzwarth Alfred R. , Wendler Joachlm
Published: January 2008

Single‐photon timing measurements on flowing samples of Chlorella vulgaris and Chlamydomonas reinhardtii at low excitation intensities at room temperature indicate two main kinetic components of the fluorescence at open reaction centers (F0) of photosystem II with lifetimes of approx. 130 and 500 ps and relative yields of about 30 and 70%. Closing the reaction centers progressively by preincubation of the algae with increasing concentrations of 3‐(3′,4′‐dichlorophenyl)‐l,l‐dimethylurea (DCMU) and hydroxylamine gave rise to a slow component with a lifetime increasing from 1.4 to 2.2 ns (Fmax) The yield of the slow component increased to 65‐68% of the total fluorescence yield in parallel to a decrease in the yield of the fast component to a value close to zero at the fmax‐level. The 130 ps lifetime of the fast component remained unchanged. The middle component showed an increase of its lifetime from 500 to 1100 ps and of its yield by a factor of 1.5. Spacing of the ps laser pulses by 12 μs allowed us to resolve a new long‐lived fluorescence component of very small amplitude which is ascribed to a small amount of chlorophyll not connected to functional antennae.

The opposite dependence of the yield of the fast and the slow component on the state of the reaction centers at almost constant lifetimes is consistent with a mechanism of energy conversion in largely separately functioning photosystem II units. Yields and lifetimes of these two components are in agreement with the high quantum yield of photosynthesis. The lower lifetime limit of 1.4 ns of the slow component is assigned to the average transfer time of an excited state from a closed to a neighboring open reaction center and the increase in the lifetime to 2.2 ns is evidence for a limited energy transfer between photosystems II.

Relative effects of changing the excitation wavelength from 630 to 652 nm on the relative fluorescence yields of the kinetic components were studied at the fluorescence wavelengths 682, 703 and 730 nm. Our data indicate that (i) the middle component has its fluorescence maximum at shorter wavelength than the fast component and (ii) that the antennae chlorophylls giving rise to the middle component are preferentially excited by 652 nm light. It is concluded that the middle component originates from the light‐harvesting chlorophyll alb protein complexes and the major portion of the fast component from the chlorophyll a antennae of open photosystem II reaction centers.
TEMPERATURE DEPENDENCE OF INDUCTION OF CYCLOBUTANE‐TYPE PYRIMIDINE PHOTODIMERS IN HUMAN FIBROBLASTS BY 313 nm LIGHT
Authors: Niggli Hugo J. , Cerutti Peter A.
Published: January 2008

The rate of cyclobutane‐type pyrimidine photodimerization with 313 nm light was determined in confluent cultures of xeroderma pigmentosum cells of group A. A new method was developed for the determination of sodium borohydride reduced thymine‐thymine (TT) and cytosine‐thymine (CT) dirners by high pressure liquid chromatography. It was found that the yield of dimerization andtheratioof CT/TT depended on the irradiation temperature in the physiological fluence range of 2.25 to 15 kJ m−2. Both were significantly higher at 37 than at 0°C.
A MODULATED LAMP SYSTEM FOR SOLAR UV‐B (280‐320 nm). SUPPLEMENTATION STUDIES IN THE FIELD
Authors: Caldwell M. M. , Gold W. G. , Harris G. , Ashurst C. W.
Published: January 2008

Precise control and modulation of fluorescent sunlamps are necessary for ecologically valid simulation of solar UV‐B (280‐320 nm) radiation enhancement which would correspond to ozone reduction. A control system is described which allows lamp emittance to be modulated over a large dynamic range (50:1), permits stable lamp operation and starting at low temperatures, and provides a sensitive feedback loop to compensate for both atmospheric conditions, such as cloud cover, as well as changes in radiant emittance from the lamps resulting from factors such as temperature and lamp age.
CAROTENOID PIGMENT ADMINISTRATION and DELAY IN DEVELOPMENT OF UV‐B‐INDUCED TUMORS
Authors: Mathews‐Roth Micheline M.
Published: January 2008

—The results of two studies are reported. In the first study, the carotenoid pigments, β‐carotene. canthaxanthin and phytoene were administered to mice after one UV‐B‐induced skin tumor had developed, to see if carotenoid administration would delay the development of subsequent tumors. Canthaxanthin significantly delayed the development of subsequent tumors. In the second study, the same pigments were administered starting 10 weeks before, and for 24 weeks after, exposure to a large single fluence (8 × 104J/m2) of UV‐B radiation, to determine the effect of the pigments on tumor development. Phytoene significantly prevented the development of tumors to this fluence of radiation.
TYROSINE DOES NOT ENHANCE TANNING IN PIGMENTED HAIRLESS MICE
Authors: Agin Patricia Poh , Wilson Diane K. , Shorter Gwendolyn G. , Sayre Robert M.
Published: January 2008

Pre‐tan products claiming to enhance pigmentation contain tyrosine as an‘active’ ingredient. Tyrosine is said to penetrate into the cell's metabolic pool, increasing the concentration of precursors essential to melanin formation, so that subsequent melanogenesis will be intensified. To address this theory, female pigmented hairless mice were irradiated three times weekly using FS‐20 lamps while receiving 0.01% tyrosine or 0.01% glycine either as a diet supplement or topically daily for 4 weeks. Control groups received the supplement or topical application without irradiation. Two additional groups were treated with a commercial pre‐tan enhancing product for 2 weeks prior to use of one group as a control, and the other irradiated as above. At the end of the experiment whole skin sections were taken for histological evaluation. Forward scattering absorbance spectrophotometry was performed on whole skin and separated epidermis.

Comparison of averaged forward scattering absorbance spectra for each group revealed that there was no significant difference in the skin optics of any of the irradiated groups, while each irradiated group was significantly different from its non‐irradiated control. The spectra of all treated controls fell within pre‐established normal control limits. Histological evaluation by Fontana‐Masson staining showed that all irradiated groups had developed noticeable pigmentation not present in the controls. Of the groups receiving topical applications, the irradiated tyrosine group developed strikingly less pigmentation than did the irradiated glycine group. The irradiated pre‐tan product treated group was intermediate in the development of pigmentation. Melanocytes were visible throughout the dermis and epidermis of the irradiated groups, whereas only scattered dermal melanocytes were found in the controls. It appears that oral or topical tyrosine did not enhance pigmentation present with or without irradiation, detected optically or histologically.
SITES SENSITIVE TO S1 NUCLEASE and DISCONTINUITIES IN DNA NASCENT STRANDS OF ULTRAVIOLET IRRADIATED MOUSE CELLS
Authors: Schumacher R. Ivan , Menck Carlos F. , Meneghini Rogério
Published: January 2008

Abstract Mouse 3T3 cells irradiated with ultraviolet light synthesize DNA containing sites sensitive to the single‐strand specific SI nuclease. The appearance of these sites correlates well with the presence of discontinuities in nascent strands, detected by the methodology of sedimentation in alkaline sucrose gradient. Thus, both the sites sensitive to SI nuclease and the discontinuities in nascent strands (i) are stabilized by caffeine; (ii) are no longer formed late after irradiation and (iii) disappear faster when a certain UV fluence is split into two fluences whose sum equals the single fluence. Moreover, the recovery in synthesizing DNA without SI sensitive sites is not dependent on excision repair of pyrimidine dimers or on continuous DNA synthesis. These SI sensitive sites are exclusive of replicative structures of irradiated cells and should correspond to stretches of single‐strand DNA (gaps) formed during replication.
DOXYCYCLINE INDUCED PHOTODAMAGE TO HUMAN NEUTROPHILS AND TRYPTOPHAN
Authors: SANDBERG SVERRE , GLETTE JOHAN , HOPEN GUNNAR , SOLBERG CLAUS OLA
Published: January 2008

Abstract—Neutrophil functions were studied following irradiation (340–380 nm) of the cells in the presence of 22 mUMdoxycycline. At increasing light fluence the locomotion, chemiluminescence and glucose oxidation (by the hexose monophosphate shunt) of the neutrophils steadily decreased. The photodamage increased with increasing preincubation temperature and time and was enhanced in D2O, reduced in azide and abolished in anaerobiosis. Superoxide dismutase, catalase or mannitol did not influence the photodamage. Photooxidation of tryptophan in the presence of doxycycline was increased9–10‐fold in D2O and nearly abolished in the presence of 0.25 mMNaN3, indicating that singlet oxygen is the most important reactive oxygen species in the doxycycline‐induced photodamage. The results may explain some of the features of tetracycline‐induced photosensitivity and why other authors have obtained diverging results when studying the influence of tetracyclines on neutrophil functions.
THE PRIMARY REACTION IN THE PHOTOREDUCTION OF PROTOCHLOROPHYLLIDE MONITORED BY NANOSECOND FLUORESCENCE MEASUREMENTS
Authors: VAN BOCHOVE A. C. , GRIFFITHS W. T. , VAN GRONDELLE R.
Published: January 2008

Abstract—Time resolved fluorescence measurements, carried out on protochlorophyllide reductase enriched membranes from oat (Avena sativa), are described. A fast (1 ns at 293 K) decaying fluorescence component is assigned to the photoactive NADPH‐protochlorophyllide‐enzyme complex, while a slower (5 ns) component is ascribed to non‐photoactive protochlorophyllide. The results are interpreted in terms of a new fast primary step in the light requiring step of chlorophyll synthesis. The temperature dependence of the rate of this reaction has been studied by measuring the decay time of the fast fluorescence component at various temperatures from 77 to 293 K. Complete spectra of the kinetic fluorescence components have been measured at 293, 160 and 77 K.
QUANTIFICATION OF PYRIMIDINE DIMERS AND APURINIC SITES IN DNAs OF UNIFORM LENGTH
Authors: Ciomei Marina , Sutherland Betsy M. , Ciarrocchi Giovanni
Published: January 2008

Abstract— A new simple in vitro assay for the determination of pyrimidine dimers and/or apurinic/apyrimidinic sites in non‐radioactive DNA has been developed. In this procedure, DNA substrates of uniform length‐which may be supercoiled, partially relaxed, relaxed or linear‐are treated with agents which produce specific single strand nicks at the site of the lesion. The number of lesions per molecule can be expressed as a function of the amount of single‐stranded molecules left intact after the specific nicking treatment. Unreacted molecules, which retain the original uniform length, are separated from the other smaller reaction products by electrophoresis on an alkaline agarose gel. In the case of circular molecules, the substrate is linearized by the use of an appropriate restriction endonuclease before loading on the gel. The amount of intact DNA molecules is obtained by integrating the corresponding peak of absorption after densitometric scan of the negative of the gel picture. This assay can detect up to eight damaged sites per duplex molecule. This method could be particularly useful when dealing with mixtures of DNA with different degrees of supercoiling or for comparisons between linear and circular DNA substrates.
ACTINIC RETICULOID–AN IDIOPATHIC PHOTODERMATOSIS WITH CELLULAR SENSITIVITY TO NEAR ULTRAVIOLET RADIATION
Authors: Botcherby P. K. , Magnus I. A. , Marimo B. , Giannelli F.
Published: January 2008

Abstract— Long wavelength UV radiations (320–400 nm) cause persistent inhibition of RNA synthesis and marked cytopathic changes in fibroblasts from patients with actinic reticuloid (AR) but not in those from patients with Bloom syndrome or xeroderma pigmentosum. Furthermore, the AR cells show abnormal DNA fragmentation when they are irradiated at temperatures compatible with enzyme activity. Germicidal UVR (ca. 95% 254 nm) stimulates DNA repair synthesis and inhibits DNA replication to a normal extent in the AR cells.

Thus, actinic reticuloid, a severe photodermatosis, characterised by skin sensitivity to UV‐B, UV‐A and part of the visible spectrum and by infiltrates reminiscent of mycosis fungoides, is a human disease with in vitro cellular sensitivity to UV‐A and, to our knowledge, is also the first to be reported.

We advance the hypothesis that inefficient cellular neutralisation of free radicals may explain the cellular phenotype of actinic reticuloid and contribute to the establishment of a vicious circle that would favour the chronic clinical course and persistent lympho‐histiocytic skin infiltrates characteristic of the disease.
DNA BREAKAGE CAUSED BY 334‐nm ULTRAVIOLET LIGHT IS ENHANCED BY NATURALLY OCCURRING NUCLEIC ACID COMPONENTS AND NUCLEOTIDE COENZYMES
Authors: Peak J. G. , Peak M. J. , Maccoss M.
Published: January 2008

Abstract— The induction of breaks in DNA in vitro caused by 334‐nm UV radíation is enhanced by the following compounds (fluence enhancement factors and concentrations used in parentheses): 4‐thiouridine (6.9, 1 mM), 5‐methylamino‐2‐thiouridine (7.5, 1 mM), 2‐thiouracil (41.0, 1 mM), riboflavin (14.4.0.1 mM), and the oxidized (6.8, 1 mM) and reduced (3.4, 1 mM) forms of nicotinamide adenine dinucleotide. Anoxia and diazobicyclo(2.2.2)octane reduce the number of DNA breaks caused by 334‐nm radiation plus 4‐thiouridine by 70 and 76%, respectively.
POLARIZED UV‐ABSORPTION SPECTRA OF RETINAL ISOMERS‐I. MEASUREMENTS IN EXTREMELY THIN MONOCRYSTAL PLATELETS
Authors: Drikos G. , Rüppel H. , Sperling W. , Morys P.
Published: January 2008

Abstract Crystals of all‐trans retinal and both different forms of 11‐cis, 12‐s‐cis retinal were grown on quartz slides with faces (101), (001) and (101), respectively, forming thin platelets of less than 0.2 μm thickness. Polarized UV absorption spectra at room temperature were measured in the range from 20 to 43 × 103 cm−1 with a microscope‐spectrophotometer. In this spectral range three diffuse absorption bands were observed for all crystal types at similar wave numbers. A main absorption band was found at 25–28 × 103 cm−1, and two further bands at 32–34 and 38–40 × 103 cm−1. In case of all‐trans retinal the latter band is by far the weakest in this spectral range. Additionally, the crystal spectrum of all‐trans retinal shows a shoulder at the low wavenumber side of the main band which cannot be resolved in the corresponding solution spectrum. In the crystal spectra of 11‐cis, 12‐s‐cis retinal, however, only a strong dissymmetry is observed at this side of the main band.
THE PHOTOCHEMISTRY OF PIPERAZINE‐2,5‐DIONE IN AQUEOUS SOLUTION
Authors: Coyle J. D. , Hill R. R. , Randall D.
Published: January 2008

Abstract The aqueous photochemistry of deoxygenated solutions of piperazine‐2,5‐dione was investigated and three products were isolated in low yield using preparative high‐performance liquid chromatography: 3,3′‐bis(piperazine‐2,5‐dione) (1), oxamide and N‐methyloxamide. The structure of 1 was established by infrared, mass and high‐field proton magnetic resonance spectroscopy, and by the synthesis of its meso diastereoisomer. A 1:2 mixture of meso and racemic diastereoisomers of 1 was formed in good yield in thermally or photochemically initiated reactions of piperazine‐2,5‐dione with t‐butyl peroxide in aqueous t‐butanol.

The rate of photolysis of aqueous piperazine‐2,5‐dione was markedly enhanced in the presence of iron(II) ions, copper(II) ions or powdered titanium dioxide. A diastereomeric mixture of 1, oxamide and N‐methyloxamide were isolated from the reaction with iron(II) ions. The possibility that oxamides were formed in these reactions via reaction with atmospheric oxygen was eliminated in a series of control experiments.

The results suggest α‐carbon radicals are important in the photolysis of peptides in fluid aqueous media, possibly as a consequence of photoinduced electron transfer. No significant adduct formation could be detected when mixtures of piperazine‐2,5‐dione and uracil or thymine were irradiated in frozen aqueous solution.
CHLOROPHYLL PHOTOSENSITIZED ELECTRON TRANSFER IN PHOSPHOLIPID BILAYER VESICLE SYSTEMS: EFFECTS OF CHOLESTEROL ON RADICAL YIELDS AND KINETIC PARAMETERS*
Authors: Ford William E. , Tollin Gordon
Published: January 2008

AbstractThe quenching of the triplet state of chlorophylla(Chl) by asymmetrically located electron acceptors was examined in vesicle systems containing egg yolk phosphatidylcholine and 0–50 mole % cholesterol. The incorporation of cholesterol had two main effects: (1) the distribution of Chl within the vesicle wall shifted from one favoring the inner monolayer to one favoring the outer monolayer, and (2) the Chi molecules (both ground and excited states) became more accessible to water and to the quencher molecules. This latter property was probably due to the creation of space between the phospholipid head groups by insertion of cholesterol. These phenomena required cholesterol concentrations in excess of 15 mol %. In general, the addition of cholesterol caused increases in the apparent bimolecular rate constant for triplet quenching, in the probability that quenching produced radicals, and in the rate of radical recombination. Some of the specific effects of cholesterol depended upon whether or not the quencher molecules were amphiphilic.
A PORPHYROPSIN‐LIKE ACTION SPECTRUM FROM Xenopus MELANOPHORES
Authors: Lythgoe J. N. , Thompson M.
Published: January 2008

Light causes an aggregation of the melanosomes in the melanophores of isolated dark adapted Xenopus tadpole tails. Dose response curves for 6 wavelengths of light were measured, and using a standard response, an action spectrum was derived that can be fitted to a porphyropsin absorbance curve.
TRANSMISSION OF HUMAN EPIDERMIS AND STRATUM CORNEUM AS A FUNCTION OF THICKNESS IN THE ULTRAVIOLET AND VISIBLE WAVELENGTHS
Authors: Bruls Wiel A. G. , Slaper H. , Van Der Leun Jan C. , Berrens L.
Published: January 2008

AbstractThe dependence of radiation transmission on sample thickness was studied in isolated samples of human stratum corneum and full‐thickness epidermis. The investigation also included samples of skin repeatedly exposed to UV‐B. Transmission was measured in the ultraviolet and in the visible from 248–546 nm. Two methods, one microscopic and the other mechanical, were used to measure thickness. There was a good correlation between the results.

The dependence of transmission on thickness in these samples could be described satisfactorily by an exponential function, implying that the Lambert‐Beer law is approximately valid. Thus, a single parameter, such as the half‐value layer (d½), is sufficient to characterize absorption in the skin samples.

Water content of the isolated stratum corneum was influenced by maintenance conditions: samples floating on water containing a small amount of NaCl were more hydrated than samples floating on a more concentrated salt solution, or stored in air. Changes in water content of the samples resulted in changes of thickness and, to a lesser extent, of transmission. Approximatein vivovalues ofd½were computed after estimating thein vivowater content of stratum corneum.

Differences found in the shape of the transmission spectra of stratum corneum and full‐thickness epidermis may reflect differences in chemical composition. The influence of wetting of the skin on its sensitivity to sunlight is explained in a new way.
ARYL AZIDES AS PROTEIN PHOTOLABELS: ABSORPTION SPECTRAL PROPERTIES AND QUANTUM YIELDS OF PHOTODISSOCIATION
Authors: Geiger Margaret W. , Elliot Margaret M. , Karacostas Velissarios D. , Moricone Thomas J. , Salmon Jesse B. , Sideli Vincent L. , Onge Martha A. St.
Published: January 2008

Abstract A series of ring‐substituted phenyl and naphthyl azides have been prepared. Electronic absorption spectral properties and quantum yields of disappearance have been determined in aqueous solution. For phenyl azide derivatives, the wavelengths of maximum absorption vary systematically, correlating with electronic effects of the ring substituents. Quantum yield values of 0.1–0.7 are obtained and are independent of a number of experimental conditions, including concentration. There is no simple correlation of the quantum yields of azide disappearance with electronic effects, except that the naphthyl azides have higher photochemical efficiencies than the phenyl azide derivatives. A series of potential protein photolabels has been identified based on electronic absorption characteristics and photochemical efficiencies.
DIFFERENTIAL EFFECTS OF PHOTOACTIVE FURANYL COMPOUNDS ON VIRUS FUNCTIONS
Authors: Hudson J. B. , Graham E. A. , Chan G. C. , Towers G. H. N.
Published: January 2008

Abstract— Five photoactive furanyl compounds were investigated for their activities against viruses. The two furanocoumarins used were 8‐methoxypsoralen (8‐MOP) and angelicin; two furanochromones, visnagin and khellin, and the furanoquinoline, dictamnine, were also used. The DNA‐containing herpes virus murine cytomegalovirus (MCMV) and the RNA‐containing togavirus, Sindbis virus, were the target viruses. All five compounds inactivated both viruses in the presence of UVA, although Sindbis virus was much less sensitive. The relative order of antiviral potency was 8‐MOP > dictamnine > visnagin > angelicin > khellin. Dictamnine however was slightly more effective than 8‐MOP against Sindbis virus. None of the treatments affected the structural integrity of MCMV, nor did they interfere with the normal transit of the virus into host cells or the localisation of the viral genome in the cell nucleus. Some early viral gene functions were expressed but the viruses did not replicate.
PHOTOSENSITIZATION OF MELANINS: A COMPARATIVE STUDY
Authors: Sarna T. , Menon I. A. , Sealy Roger C.
Published: January 2008

Abstract— Measurements of photosensitized free‐radical production and oxygen consumption have been made in several melanin systems. The melanins studied were cysteinyldopa melanin (a model for pheomelanin), natural pheomelanins extracted from red hair and from red chicken feathers, and eumelanin extracted from bovine eyes. Rose Bengal was used as photosensitizer. A significant enhancement in the rates of free radical production and oxygen consumption was found in all systems when sensitizer was present. The largest effects were found with cysteinyldopa melanin and effects on pheomelanins were shown to be greater (by factors of4–6) than on eumelanins.
RESONANCE RAMAN SPECTRA OF THE “BLUE” and THE REGENERATED “PURPLE” MEMBRANES OF Halobacterium halobium
Authors: Pande C. , Callender R. H. , Chang C.‐H. , Ebrey T. G.
Published: January 2008

Abstract— We have obtained the resonance Raman spectra of the deionized form of the purple membrane, the so called blue membrane, as well as the purple membrane regenerated by titrating the blue membrane with either Na+, Ca2+ or La3+. All types of regenerated purple membrane have identical Raman spectra which are virtually indistinguishable from the native light‐adapted bacteriorhodopsin spectrum. On the other hand, Raman data for the blue membrane suggest that it consists of essentially two pigment forms with absorption maxima around 605 and 570 nm and containing 13‐cis and all‐trans isomeric configurations of the chromophore. This is consistent with our chromophore extraction results which reveal that the blue membrane consists of 30% 13‐cir and 70%all‐trans chromophore.
INSTRUMENTATION FOR FLUORESCENCE MICROSCOPY WITH PICOSECOND TIME RESOLUTION
Authors: Rodgers Michael A. J. , Firey Patricia A.
Published: January 2008

Abstract— Time‐resolved fluorescence microscopy using excitation by actively mode‐locked dye lasers and analysis by time‐correlated single photon counting is shown to be an effective way of obtaining a high degree of spatial and temporal resolution. The imaging capabilities of the microscope make for optimal instrument response functions even with inexpensive photomultiplier tubes. Thus far limited (by the laser source) to long wavelength visible excitation, the excellent light collection and imaging, coupled with the sensitivity of single photon counting make it highly probable that the much weaker U‐V second harmonics of the visible dyes will be useable. Certainly the potential of using the third harmonic line (355 nm) of a mode‐locked c.w. Nd: YAG laser, or fundamental lines from mode‐locked c.w. ion lasers as excitation sources will enhance the technique. Nevertheless, with visible‐absorbing dyes only it is possible to excite such fluorochromes as chlorophylls, porphyrins, xanthenes (rose bengal, erythrosin B), phycobiliproteins, thionine dyes, ethidium bromide, and so on. Furthermore, this technique can be straightforwardly extended for polarized light measurements thereby allowing determinations of rotational diffusion of fluorochromes in cells and organelles. The extension to variable temperature situations is easy to conceive. In addition to its use for examination of cellular and sub‐cellular entities, the equipment described can be profitably employed wherever spatial resolution may provide extra information, such as studies of powders and the structures of surfaces and interfaces.
ACTION SPECTRA FOR PHOTOTROPIC BALANCE IN Phycomyces blakesleeanus: DEPENDENCE ON REFERENCE WAVELENGTH and INTENSITY RANGE
Authors: Galland Paul , Lipson Edward D.
Published: January 2008

Abstract— Action spectra for phototropic balance of Phycomyces blakesleeanus sporangiophores were measured for various reference wavelengths and intensity ranges. Balance action spectra were made at fluence rates of 10‐4 W m‐2 with reference wavelengths of 450 nm, 394 nm, 507 nm, and broadband blue light. For broad‐blue light and 450 nm light as references, typical flavin‐like action spectra were found with a ma jor peak at 455 nm, a secondary peak at 477 nm, and a minor peak at 383 nm; these peaks are wider for broad blue than for 450 nm light. With the 394 nm reference, there is a major peak at 455 nm, a secondary peak at 477 nm and a minor peak at 394 nm. An action spectrum with 507 nm reference has a major peak at 455 nm and a minor peak at 383 nm, but no peak at 477 nm. A balance action spectrum was made with 450 nm reference light near threshold intensity (2 times 10‐8 W m‐2); there, the 386 nm peak is greatly reduced, while the 455 nm peak is enhanced. The intensity dependence of the 386 nm peak was studied in detail for reference light of 450 nm. We found that the relative quantum efficiency of the 386 nm light increases with the logarithm of the 450 nm fluence rate; in the high intensity range (0.3 W m‐2) the relative quantum efficiency of the 386 nm light is 1.3 and approaches zero at 10‐9 W m‐2. These findings indicate that P. blakesleeanus phototropism is mediated by multiple interacting pigments or by a photochromic photoreceptor.
MODIFIED ACTION SPECTRA OF PHOTOGEOTROPIC EQUILIBRIUM IN Phycomyces blakesleeanus MUTANTS WITH DEFECTS IN GENES madA, madB, madC, and madH
Authors: Galland Paul , Lipson Edward D.
Published: January 2008

Abstract— Action spectra of photogeotropic equilibrium were measured for behavioral mutants of Phycomyces blakesleeanus with defects in the genes madB, madC and madH as well as for a double mutant defective in the genes madA and madC. The action spectra of strains C109 (madB), LI (madC) and L52 (madA madC) all lack the broad near‐ultraviolet peak which extends from 347 to 386 nm in the wild type; the peaks at 414 and 491 nm are also missing in these mutants. The double mutant L52 (madA madC) shows a novel broad peak at 477 nm; the relative quantum effectiveness of L52 at 477 nm is 10 times higher than in LI (madC119). These properties of the double mutant L52 (madA madC) suggest steric interaction of the madA and the madC gene products in the photoreceptor complex. For the hypertropic mutant L84 (madH) the action spectrum and absolute sensitivity are similar to those for wild type. These results confirm and extend previous findings that multiple photoreceptors are mediating phototropism in P. blakesleeanus.
PHOTODYNAMIC RELEASE OF PROTOPORPHYRIN FROM INTACT ERYTHROCYTES IN ERYTHROPOIETIC PROTOPORPHYRIA: THE EFFECT OF SMALL REPETITIVE LIGHT DOSES
Authors: Brun Atle , Sandberg Sverre
Published: January 2008

Abstract— Erythrocytes from patients with erythropoietic protoporphyria contain large amounts of protoporphyrin bound to (hemo)globin. Irradiation of these cells causes a shift in fluorescence emission maximum and a decreased fluorescence intensity which is consistent with transfer of protoporphyrin from (hemo)globin to the cell membrane. When the erythrocytes were irradiated intermittently, nearly 70% of the protoporphyrin was released and the hemolysis was less than 3%. Giving the total light dose as a single pulse, resulted in 84% protoporphyrin release and 16% hemolysis.

In vivo the erythrocytes obtain small, repetitive light doses when circulating in the dermal capillaries. We suggest the possibility that in patients with erythropoietic protoporphyria these small light pulses could be sufficient to photodamage the binding place of protoporphyrin on (hemo)globin. In the dark, protoporphyrin can then move from (hemo)globin through the cell membrane and bind to albumin in the serum. Our findings indicate that if protoporphyrin is not present in the cell membrane during irradiation, no photohemolysis will occur. This may explain why patients with erythropoietic protoporphyria have no abnormal hemolysis. The effect of intermittent light pulses may also contribute to the understanding of the protoporphyrin release from erythrocytes in patients with erythropoietic protoporphyria.
CAROTENOID DOSE LEVEL and PROTECTION AGAINST UV‐B INDUCED SKIN TUMORS
Authors: Mathews‐Roth Micheline M. , Krinsky Norman I.
Published: January 2008

Abstract— Two groups of workers have reported that low levels of carotenoids (0.07 and 0.01%) were effective in preventing tumor development in experimental animals. To see whether these low concentrations were effective in preventing the development of UV‐B induced skin tumors, groups of hairless mice were fed beta‐carotene beadlets or canthaxanthin beadlets or the equivalent weight of placebo beadlets at these two final concentrations of carotenoid, and also at a final concentration of 2%, the amount found effective by us in past experiments. The mice received their pigments either for 4 days (the group receiving 0.01%), one month (the group receiving 0.07%) or for 12 weeks (the group receiving 2%) before irradiation started, in order to duplicate the conditions used in the previously reported experiments, and continued to receive their respective diets during the irradiation and observation period. All groups received a total dose of 10.8 J/cm2 of UV‐B radiation. At 2 and 0.07%, beta‐carotene and canthaxanthin each conferred significant protection against skin tumor development. However, at 0.01 %, neither carotenoid offered protection against tumor development.
O2>‐DEPENDENT and ‐INDEPENDENT PHOTOOXIDATION OF QUERCETIN IN THE PRESENCE and ABSENCE OF RIBOFLAVIN and EFFECTS OF ASCORBATE ON THE PHOTOOXIDATION
Authors: Takahama Umeo
Published: January 2008

Abstract—The self‐sensitized photooxidation of quercetin was not suppressed by superoxide dismutase (SOD), but suppressed by ascorbate. During the suppression of quercetin photooxidation, ascorbate was oxidized. These results suggest the reduction of oxidized quercetin to quercetin by ascorbate. Quercetin photooxidation in the presence of both riboflavin and EDTA was suppressed by SOD by about 90%. The result suggests the participation of O2‐in the photooxidation of quercetin. The participation of O2‐in the quercetin oxidation was confirmed by a xanthine‐xanthine oxidase system. Based on these results the physiological and pharmacological functions of quercetin are discussed.
UVA EXPOSURE AND PITUITARY SECRETION. VARIATIONS OF HUMAN LIPOTROPIN CONCENTRATIONS (βLPH) AFTER UVA EXPOSURE
Authors: Belon Ph. E.
Published: January 2008

Abstract— Variations of βLPH concentrations were measured in a group of volunteers exposed to UVA (2 J/cm2) without psoralen treatment. Volunteers were exposed with and without sunblock cream: with the sunblock cream, the (βPH concentration did not increase at all after UVA exposure; without the sunblock cream, the mean concentration increased significantly.
ENERGY TRANSFER IN TRIMERIC C‐PHYCOCYANIN STUDIED BY PICOSECOND FLUORESCENCE KINETICS
Authors: Wendler J. , John W. , Scheer H. , Hoezwarth A. R.
Published: January 2008

Abstract—The excited state kinetics of trimeric C‐phycocyanin fromMastigocladus laminosushas been measured as a function of the emission and excitation wavelength by the single‐photon timing technique with picosecond resolution and simultaneous data analysis. A fast decay component of 22 ps (C‐phycocyanin with linker peptides) and 36 ps (C‐phycocyanin lacking linker peptides) is attributed to efficient energy transfer from sensitizing to fluorescing chromophores. At long detection wavelengths the fast decay components are found to turn into a rise term. This finding further corroborates the concept of intramolecular energy transfer. Previous reports on the conformational heterogeneity of the chromophores and/or proteins in C‐phycocyanin are confirmed. Our data also provide indications for the importance of the uncoloured linker peptides for this heterogeneity.
OBSERVATIONS ON THE PHOTOSENSITIZED BREAKAGE OF DNA BY 2‐THIOURACIL AND 334‐nm ULTRAVIOLET RADIATION
Authors: Peak Jennifer G. , Peak Meyrick J. , Foote Christopher S.
Published: January 2008

Abstract— Breaks induced in purified DNA by 334‐nm ultraviolet (UV) radiation are enhanced 30 times when 2‐thiouracil (s2Ura) is present during aerobic irradiation. This enhancement by s2Ura is maximally effective at a concentration of about 1 mM. Anoxic irradiation reduces the s2Ura‐enhanced breakage by 90%, indicating a Type II photosensitization. Benzoate, glycerol, diazabicyclo[2.2.2.]octane (DABCO) and histidine all inhibit formation of s2Ura photosensitized breaks, unlike diethylenetriaminepenta‐acetic acid (DETAPAC) and catalase, which do not. The relationships between the concentration of DABCO. benzoate and histidine and their protection against induction of single strand breaks (SSBs) were similar, with little inhibition below 10 mM and maximal inhibition near 0.1 M for all compounds. Irradiation of the DNA‐s2Ura mixture dissolved in D2O instead of H2O enhanced the rate of induction of SSBs in DNA by 334‐nm light almost five times. Addition of superoxide dismutase (40, 80 and 200 μg/ml) decreased the rate of induction of breaks in DNA by 334‐nm radiation plus s2Ura (in H2O) by about 40%. Boiled superoxide dismutase had no effect.
WEAK COMPLEX FORMATION BETWEEN PYRENE AND POLAR SOLVENTS
Authors: Nakashima K. , Koyanagi M.
Published: January 2008

Abstract— Evidence of complex formation between pyrene and polar solvent molecules has been obtained by monitoring the S1,← S0 and S2← S0 absorption spectra of pyrene. The solvents employed are propionitrile, valeronitrile, dichloromethane, and dioxane. The stabilization energy is found to be small relative to general hydrogen bond energies, but somewhat high relative to the Boltzmann energy. These are in good accord with the findings of Lianos and Georghiou [Photochem. Photobiol.30,355 (1979)] that pyrene forms 1:1 molecular complexes with several dipolar solvents in the ground state.