bluuebunny/crossref_metadata_2025 huggingface dataset:
IMMUNOLOGICALLY ACTIVE LESIONS INDUCED ON DOUBLE‐STRANDED DNA WITH ULTRAVIOLET
Authors: Wakizaka Akira , Okuhara Eiji
Published: January 2008

Abstract— Some immunochemical properties of double‐stranded DNA irradiated with UV were studied, using a radioimmunoassay with irradiated [3H]‐DNA and experimentally produced antibodies to DNA. Reactivity of antibodies revealed that irradiated DNA contained an immunologically active structure other than the irradiated DNA specific structure, resembling that of thermally denatured DNA. inhibition assay demonstrated that while DNA‐antibody binding was effectively inhibited by mixed purine and pyrimidine oligonucleotides, thymine dimer containing pyrimidine oligonucleotides derived from the irradiated DNA showed no appreciable inhibition. The antigenic structure specific for irradiated DNA was found to be thermally labile in low salt medium. Cupric and ferrous ions and cysteine added to the DNA solution inhibited antigenicity formation during irradiation, but these substances exhibited no effect on dimer formation in irradiated frozen thymine solution. Calcium ions and histidine were inert for the former reaction but inhibited the latter effectively. This suggests that different mechanisms are involved in the 2 processes. The immunologically active UV‐induced lesions appeared to depend mainly on a conformational structure change of the DNA strands rather than on a single modified base moiety.
THE ROLE OF SINGLET OXYGEN IN PHOTOOXIDATION OF EXCITABLE CELL MEMBRANES
Authors: Pooler J. P. , Valenzeno Dennis P.
Published: January 2008

Abstract— Giant nerve axons from lobsters were photooxidized by visible light from a Xe arc using eosin Y, rose bengal and methylene blue as sensitizers. The degree of modification was assayed as the rate constant for block of sodium channels during illumination. Protection or enhancement of modification was tested for several reagents known to interact with singlet oxygen. Deuterium oxide enhanced the modification up to 57% while sodium azide protected up to 60%. β ‐Carotene, triethylamine and DABCO exerted no effect. From a consideration of the probable low polarity environment of the sensitization sites and diffusional restrictions on reagents it is concluded that intramembranously created singlet oxygen plays a significant role in membrane modification.
THE RELATIONSHIP OF ACCESSORY PIGMENTS TO CHLOROPHYLL a CONTENT IN CHLOROPHYLL‐DEFICIENT PEANUT AND SOYBEAN VARIETIES
Authors: Eskins K. , Banks D. J.
Published: January 2008

Abstract— A relationship between Chl a and each of its accessory pigments, neoxanthin, violaxanthin, lutein, Chl b and carotene, is demonstrated in soybean and peanut genotypes. These genotypes include normal and Chl‐deficient types. Plots of Chl a content against accessory pigment content generate straight‐line relationships that are extrapolated to intersect the Chl a axis. The points of intersection correctly predict the order of origin of certain accessory pigments (lutein, carotene and Chl b), but incorrectly predict that neoxanthin and violaxanthin arise after the introduction of Chl a.
SPECTROSCOPY OF POLYENES–III. ABSORPTION AND EMISSION SPECTRAL INVESTIGATION OF POLYENE SCHIFF BASES AND PROTONATED SCHIFF BASES RELATED TO VISUAL PIGMENTS
Authors: Das Paritosh K. , Kogan Gregory , Becker Ralph S.
Published: January 2008

Abstract— A number of n‐butylamine Schiff bases of polyenals related to retinals as homologues and analogues, and their protonated forms, have been studied for absorption and emission spectral properties. The polyene Schiff bases exhibit the same general features in their absorption spectra as those of the parallel polyenals except that the lBu←1Ag and π*←n singlet transitions are at substantially higher energy in the Schiff bases (the shift being larger for the π*← n transition). The Schiff bases with short polyene chainlength (n= 2, 3 where n is the number of double bonds including C=N) do not fluoresce or phosphoresce in 3‐methylpentane in the temperature range 298–77 K. The Schiff bases with intermediate chainlength (n= 4, 5) show fluorescence at 77 K with intensity strongly dependent on the nature of solvent. The Schiff bases with relatively long chainlength (n= 5–7) show strong or moderately strong fluorescence at 77 K and very weak fluorescence at 298 K (n = 7) with intrinsic radiative lifetimes much longer than those estimated from the oscillator strength of the low‐energy, strong absorption band (1Bu←1Ag). A discussion on the possible state order and nature of the fluorescing state of the various polyene Schiff base systems is presented.
FORMATION OF SINGLET MOLECULAR OXYGEN BY 8‐METHOXYPSORALEN*
Authors: Mol N. J. de , van Henegouwen G. M. J. Beijersbergen
Published: January 2008

Abstract— The formation of singlet molecular oxygen (lO2) by energy transfer from the excited 8‐meth‐oxypsoralen (8‐MOP) molecule was investigated. This was done in several ways: (a) In the reaction of irradiated 8‐MOP with the 1O2 acceptor 2‐methyl‐2‐pentene, the characteristic oxidation products were identified. (b) The rate of the 8‐MOP sensitized photooxidation of 3, 4‐dihydroxy phenylalanine (dopa), which appeared to be also a useful 1O2 acceptor, was larger in D2O than in H2O. (c) The β‐values for reaction of 1O2with dopa in the presence of 8‐MOP or of methylene blue as 1O2 generators were in accordance with each other. The consequences of 1O2 formation by 8‐MOP sensitization is discussed for the clinical use of this compound.
DOSE‐RESPONSE CHARACTERISTICS OF IMMUNOLOGIC UNRESPONSIVENESS TO UV‐INDUCED TUMORS PRODUCED BY UV IRRADIATION OF MICE
Authors: DeFabo E. C. , Kripke M. L.
Published: January 2008

Abstract— Irradiation of mice with unfiltered FS40 sunlamps renders them susceptible to challenge with highly antigenic UV‐induced skin tumors. Dose‐response studies demonstrated that the susceptibility of mice to tumor challenge was directly proportional to the total dose of UV radiation, and was independent of the manner in which the dose was administered. A fractionated dose was no more effective than the same total dose given as a single treatment in inducing susceptibility to tumor challenge. The effects of even suboptimal doses of UV radiation persisted for as long as 6 months after the UV treatment.
SPATIAL ARRANGEMENT OF RHODOPSIN IN THE DISK MEMBRANE AS STUDIED BY ENZYMATIC LABELING*
Authors: Adams Alois J. , Somers Robert L. , Shichi Hitoshi
Published: January 2008

Abstract—Intact disks prepared from fresh bovine retinas were phosphorylated with γ‐[32P]‐ATP and highly purified rhodopsin kinase. After regeneration. the visual pigment was cxtracted and purified on ECTEOLA‐cellulose. The purified pigment contained [32P]‐radioactivity. When intact disks were frozen and thawed. the membrane was inverted and became capable of binding concanavalin A. The inversion process could be followed by measuring the entrapment by the disk of [3H]‐inulin. the impermeable polysaccharide. When the inverted disks were incubated with UDP‐[3H]‐galactose and galactosyltransferase and rhodopsin was extracted and purified. [3H]‐gahctose was incorporated into the pigment. From these results we conclude that rhodopsin is a transmembrane protein with its carbohydrate moiety on the internal (intradiscal) surface and its phosphorylation sites on the external (interdiscal) surface
CHEMISTRY OF SINGLET OXYGEN—XXVIII*. STERIC AND ELECTRONIC EFFECTS ON THE REACTIVITY OF SULFIDES WITH SINGLET OXYGEN
Authors: Kacher Mark L. , Foote Christopher S.
Published: January 2008

Abstract—The rates of reaction of singlet oxygen with a number of alkyl and aryl sulfides have been determined in CH3OH. The rate for diethylsulfide is 1.71 ± 0.06 × 107M‐1 s‐1. The addition of methyl groups α to the sulfur causes an approximate tenfold decrease in rate for each symmetrical pair. A similar effect is caused by replacement of alkyl by phenyl groups. The rates of substituted thioanisoles correlate well with σ(ρ= ‐1.6). but poorly with EP/2 (half‐peak oxidation potentials). A mechanism involving nucleophilic reaction of the sulfide with oxygen, rather than charge transfer is suggested.
INACTIVATION OF LIPID‐CONTAINING VIRUSES BY HYDROPHOBIC PHOTOSENSITIZERS AND NEAR‐ULTRAVIOLET RADIATION
Authors: Snipes Wallace , Keller Gregory , Woog John , Vickroy Tom , Deering Reginald , Keith Alec
Published: January 2008

Abstract—The hydrophobic photosensitizers acridine and phenothiazine inactivate the lipid‐contnining viruses PM2,φ6, and herpes simplex when samples are illuminated with near‐UV radiation. φ23–1‐a. which is insensitive to organic solvents and presumably contains no lipids. is not inactivated under comparable conditions. For acridinc, the inactivation of virus requires that oxygen be present and is inhibited by sodium azide, implicating the involvement of singlet oxygen. For phenothiazine, oxygen is not required for photosensitized inactivation. Treatment of PM2 with acridine and near‐UV light caused a complete disruption of the virion, as determined by sucrose gradient analysis of treated and untreated samples. These data and related observations suggest that lipid‐containing viruses are inactivated through photosensitized membrane damage.
THE LIGHT DEPENDENT QUENCHING OF CHLOROPLAST FLUORESCENCE BY COFACTORS OF CYCLIC ELECTRON FLOW IN PHOTOSYSTEM I
Authors: Homann Peter H.
Published: January 2008

Abstract—When 3–(3′,4′‐dichlorophenyl)‐1,1‐dimethylurea poisoned, intact thylakoids of isolated chloroplasts are illuminated in salt free suspension media, N‐methylphenazinium cations (MP+) are reversibly taken up. Simultaneously, the chlorophyll fluorescence is reversibly lowered. When inorganic salts in the reaction medium provide membrane permeant charge balancing ions, the extent of the MP+ association with the thylakoids is strongly increased, but the fluorescence lowering is hardly affected. lonophoretically active agents inhibit specifically the salt dependent increment of the MP+ interaction with the thylakoids, but have only insignificant effects on the fluorescence lowering provided the experimental conditions do not allow the formation of a proton gradient across the thylakoid membrane. On the basis of these results, and of data obtained from comparative studies with other cofactors of cyclic electron transport in PS I, it is suggested that the ‘energy dependent’ fluorescence lowering is linked to a binding of cationic cofactors to nucleophilic sites in or at the thylakoid membrane. Such sites appear to become exposed in the wake of a light dependent transport of the cofactor, or of protons, into the thylakoid.
THE ABSOLUTE VALUE OF THE REACTION RATE CONSTANT OF BILIRUBIN WITH SINGLET OXYGEN IN D2O
Authors: Matheson I. B. C.
Published: January 2008

Abstract— The chemical reaction rate constant of bilirubin with singlet oxygen in basic aqueous solution has been redetermined to be 3.5 × 108 M‐1 s‐1 by a competitive technique using a 1,3‐diphenylisobenzofuran in sodium dodecyl sulfate micelles. Bilirubin also physically quenches a singlet oxygen with a rate constant of 9 × 108M‐1 s‐1. The lifetime of singlet oxygen in D2O solution has been determined to be 35 μs. The absorption cross‐section for the molecular oxygen 3∑g‐→1δg+ 1v electronic transition at 1.06μn in aqueous solution is unexpectedly larger than the gas paase cross‐section.
ON THE MECHANISMS OF PHOTOLYSIS OF COMPOUNDS I AND II OF HORSERADISH PEROXIDASE AT 77 K*
Authors: Nadezhdin A. D. , Dunford H. B.
Published: January 2008

Abstract—When Compounds I and II of horseradish peroxidase in glycerol/water glasses at 77 K were irradiated with the light of a mercury lamp, some changes in optical spectra as well as the development of strong EPR signals of a free‐radical type were detected. In case of photolysis of Compound I the light of wavelengths around 400 nm was the most effective, while only short wavelength (≥ 280 nm) light affected Compound II. The results of experiments with thawing and freezing the product of photolysis of Compound I (called Intermediate Y) provide further evidence for the suggestion that the ferric state of the heme iron is generated in the course of the photolysis. The quantum yields of the photolysis of Compound I at different wavelengths of irradiating light were obtained and mechanisms of the photolysis of Compounds I and II are proposed.
OXODIPYRROMETHENES AS REACTIVE SINGLET OXYGEN ACCEPTORS. MEASUREMENT OF THEIR CHEMICAL REACTION RATES BY A LASER FLASH PHOTOLYSIS TECHNIQUE
Authors: Matheson I. B. C. , Lightner D. A.
Published: January 2008

Abstract— Singlet oxygen has been generated directly in 1,1,2‐trichloro, 1,2,2‐trifluoroethane solution by irradiation of the oxygen dimol 23∑‐g→21δg transition with a pulsed dye laser and the 3∑g‐→1δg+ lv transition with a continuous Nd‐YAG laser. The rates of chemical reaction and physical quenching of singlet oxygen so generated has been measured for a series of substituted oxodipyrro‐methenes. The results show that the oxodipyrromethenes react with singlet oxygen at rates comparable to that for 1,3‐diphenylisobenzofuran. The rate of quenching of singlet oxygen by ground state oxygen has been measured to be 2.5±0.3 × 103M‐l s‐1.
UV‐ENHANCED VIRUS REACTIVATION IN MAMMALIAN CELLS: EFFECTS OF METABOLIC INHIBITORS*
Authors: Lytle C. D. , Goddard J. G.
Published: January 2008

Abstract—The induction process of UV‐enhanced reactivation of UV‐irradiated herpes simplex virus was investigated in CV‐1 monkey kidney cells. A protein synthesis inhibitor, cycloheximide (0.5–5 μg/m/), present in the culture medium For 24 h between cell irradiation and virus infection decreased the enhanced virus survival normally found in UV‐irradiated cultures. The enhanced virus reactivation became essentially resistant to the addition of cycloheximide by 6–8 h after cell irradiation, indicating that the cycloheximide‐sensitive process necessary for enhanced reactivation was complete by that time. Since cycloheximide not only inhibits protein synthesis, but DNA synthesis as well, we investigated the effect of a DNA synthesis inhibitor, hydroxyurea. Hydroxyurea did not decrease UV‐enhanced virus survival, but resulted in enhanced virus survival even in unirradiated cells. Therefore, the cycloheximide‐caused inhibition of UV‐enhanced reactivation did not arise from inhibition of DNA synthesis. The combined results indicate that (1) UV‐enhanced virus reactivation in monkey kidney cells requires de novo protein synthesis during the first 6–8 h after cell irradiation and that (2) DNA synthesis inhibition may be the initiating event.
SATURATION OF DNA REPAIR IN MAMMALIAN CELLS*
Authors: Ahmed Farid E. , Setlow R. B.
Published: January 2008

Abstract—Excision repair seems to reach a plateau in normal human cells at a 254 nm dose near 20J/m2. We measured excision repair in normal human fibroblasts up to 80J/m2. The four techniques used (unscheduled DNA synthesis, photolysis of BrdUrd incorporated during repair, loss of sites sensitive to a UV endonuclease from Micrococcus luteus, and loss of pyrimidine dimers from DNA) showed little difference between the two doses. Moreover, the loss of endonuclease sites in 24 h following two 20J/m2 doses separated by 24 h was similar to the loss observed following one dose. Hence, we concluded that the observed plateau in excision repair is real and does not represent some inhibitory process at high doses but a true saturation of one of the, rate limiting steps in repair.
THEORY OF TIME‐DEPENDENT PHOTO‐SELECTION IN INTERACTING FIXED SYSTEMS
Authors: Tanaka Fumio , Mataga Noboru
Published: January 2008

Abstract— Time‐dependent and time‐independent photo‐selections are considered in the case where rotational motion or the fluorophore is negligible. The expressions derived are applied to the dual emission system and energy transferring systems. Explicit equations of the photo‐selection for a dimer where the constituent monomers weakly interact with each other are also worked out. Relationships of the present theory with the previous works are discussed.
PHYSIOLOGICAL STUDIES ON PEA TENDRILS—X. CHARACTERIZATION OF THE LIGHT ACTIVATION EFFECT ON CONTACT COILING AS A BLUE LIGHT TRIGGER*
Authors: Shotwell M. , Jaffe M. J.
Published: January 2008

Abstract— Tendrils of the Alaska pea lose their capacity to coil in response to a mechanical stimulus between 24 and 48 h after being placed in the dark. Light is thereafter necessary for the motor response to proceed once the mechanical stimulus has becn sensed by dark‐adapted tendrils. An action spectrum for this light activation effect showed that the most effective region of the visible spectrum was a narrow band in the blue region.

Tendrils excised from their petiole and leaflets coiled more than any other preparation used. A linear relationship was found between the duration of post‐stimulated white light treatment and the amount of coiling.
BLACKLIGHT AND SHORTWAVE UV SENSITIVITY OF NEUROSPORA CRASSA AS A FUNCTION OF CULTURE AGE
Authors: Weaver Christine A. , Tuveson R. W.
Published: January 2008

Abstract— Conidia of differing ages from wild type and the fluffy (fl) mutant of Neurospora were inactivated with both blacklight and shortwave UV. Five‐day‐old cultures of both wild type and fluffy conidia were equally sensitive to inactivation by shortwave UV while the fluffy mutant was more sensitive to blacklight inactivation. As the cultures age, both wild type and the fluffy mutant become more sensitive to inactivation by blacklight and shortwave UV. Possible explanations are offered for the enhancing effects of age on sensitivity to blacklight and shortwave UV.2
AN EPR STUDY OF π‐CATION RADICALS IN DINUCLEOSIDE PHOSPHATES AND DNA PRODUCED BY PHOTOIONIZATION
Authors: Sevilla M. D. , D'Arcy J. B. , Morehouse K. M. , Engelhardt M. L.
Published: January 2008

Abstract—

In this work we have produced the π‐cation radicals of a number of nucleotides, dinucleoside phosphates, and DNA in aqueous glasses (8M NaCIO4) by photoionization and investigated these species by EPR spectroscopy. Results found for nucleotides and dinucleoside phosphates containing one type of DNA base, e.g. TpT, GpG, or dApdA, were used in the analysis of spectra found for mixed dinucleoside phosphates, e.g. TpdG. For TpdG and TpdA in neutral glasses photoionization takes place from the purine base and no transfer of charge to the pyrimidine base is found. In basic conditions both the adenine and thymine π‐cations are observed in TpdA. In both neutral and basic conditions the results found for mixed dinucleoside phosphates containing guanine show that the guanine cation is formed preferentially by photolysis. This result was found to extend to DNA. Photolysis of DNA in 8M NaC1O4 produced principally the guanine cation. Computer simulations using parameters determined by other workers from a study of γ‐irradiated oriented DNA closely match the spectrum found in this work attributed to the guanine cation in dinucleoside phosphates and DNA. This work thus confirms the presence of the guanine cation in γ‐irradiated DNA.
EFFECT OF RECEIVER ORIENTATION ON ERYTHEMA DOSE1,2
Authors: Burt James E. , Luther Frederick M.
Published: January 2008

Abstract—

‐The analysis of solar erythema dose under changing ozone amount, previously confined to the study of horizontal surfaces, is extended to include the effects of receiver orientation. A semi‐empirical model is used to calculate erythema (sunburn) dose for non‐horizontal plane areas under cloudless conditions as a function of latitude, season, and ozone amount. According to the model, in middle and high latitudes, surfaces with inclination angles (α) up to 45° receive at least 80% of the daily erythema dose received by a horizontal surface. Much larger reductions in daily erythema dose occur for α > 45°. which can result in a significant reduction in the latitudinal gradient of erythema dose. The amplification factor for erythema dose (Δdose/ΔO3) varies significantly with latitude, but it is only weakly dependent upon receiver orientation. Additional calculations indicate that the amplification factor may be significantly larger for skin cancer than for erythema.
PHOTOELECTRIC EFFECTS IN DYE‐SENSITIZED ARTIFICIAL LIPID MEMBRANES
Authors: Mountz James M. , Tien H. TI
Published: January 2008

Abstract—

Using dyes of known redox potentials the specific mechanisms of dark and light potential generation is analyzed in pigmented lipid membranes. The role of the ionic and electronic conductance, as well as the redox potential gradient is specifically related to the observed open circuit voltage developed across the membrane. The results can be most easily explained by the redox electrode model.
INTERMOLECULAR INTERACTIONS IN VISUAL PIGMENTS. THE HYDROGEN BOND IN VISLON
Authors: Favrot J. , Leclercq J. M. , Roberge R. , Sandorfy C. , Vocelle D.
Published: January 2008

Abstract—

Model studies including quantum chemical calculations and the measurement of infrared and ultraviolet spectra are presented as contributions to the elucidation of the nature of the photochemical step of vision. The importance of the hydrogen bond in which the protonated nitrogen of the retinal Schiff base is involved is stressed as well as that of the perturbation of the β‐ionone ring by negative groups. It is suggested that by combining these two perturbations the low excitation energy of rhodopsin can be obtained without actual protonation of the Schiff‐base prior to photon absorption. The variation of rhodopsin's color from one species to another could also be related to this. Protonation could be a consequence of photonabsorption and the higher basicity of the excited state. This, in turn, leads to the suggestion that the protonated species is actually bathorhodopsin, not rhodopsin. Comments are made on the identity of the (ππ*) state which is involved.
LASER PHOTOLYSIS STUDIES OF QUINONE REDUCTION BY CHLOROPHYLL a IN ALCOHOL SOLUTION
Authors: Tollin Gordon , Castelli Francesco , Cheddar Glen , Rizzuto Frank
Published: January 2008

Abstract—

Upon laser photolysis of chlorophyll‐quinone solutions in ethanol, transients due to the chlorophyll triplet state (Ct), the chlorophyll cation radical (C+) and the semiquinone radical (Q‐) can be observed. The rise of Q‐ parallels the decay of Ct. demonstrating the precursor role of the triplet. The decay of C+ is second order, consistent with reverse electron transfer, and has a rate constant which is independent of quinone potential, and an activation energy of 14kJ/mol due mainly to the temperature dependence of solvent viscosity. Triplet quenching and C+ yield are found to decrease with decreasing quinone potential.
MUTATION INDUCTION BY AND MUTATIONAL INTERACTION BETWEEN MONOCHROMATIC WAVELENGTH RADIATIONS IN THE NEAR‐ULTRAVIOLET AND VISIBLE RANGES
Authors: Tyrrell Rex M.
Published: January 2008

Abstract— The induction of mutations (reversion to tryptophan independence) by various UV (254, 313, 334 and 365 nm) and visible (405 and 434 nm) wavelengths was measured in exponential phase populations of Escherichia coli B/r thy trp and B/r thy trp uvrA by assay of irradiated populations on semi‐enriched media. No mutations were induced in the repair proficient strain at wavelengths longer than 313 nm. Mutations were induced in the excisionless strain at wavelengths as long as 405 nm but less than expected from the known amount of DNA damage induced. Irradiation at the longer wavelengths (434, 405, 365 and 334 nm) suppressed the appearance of 254‐ or 313‐nm‐induced mutations in the repair competent strain but not in the excision deficient strain. The relative dose‐requirement for mutation suppression was related to the relative efficiency of these wavelengths in inducing growth delay. These results suggest that the growth delay induced by near‐UV and visible wavelengths allows more time for the ‘error‐free” excision repair process to act on the potentially mutagenic lesions induced by 254‐ and 313‐nm radiations, thereby reducing the mutation frequency observed in the repair‐proficient strain. The level of near‐UV mutation induced in the excision deficient strain is lower than expected from the DNA damage known to be induced. It is possible that near‐UV radiation induces a class of lethal lesions that are not susceptible to error‐prone repair.
TRANSFORMATION OF BALB 3T3 CELLS EXPOSED TO A GERMICIDAL UV LAMP AND A SUNLAMP
Authors: Withrow Thomas J. , Lugo Maria H. , Dempsey Mary J.
Published: January 2008

Abstract— The effect of germicidal UV and sunlamp exposure on direct and simian virus‐40 (SV‐40) transformation of Balb 3T3 cells was studied. Transformation was determined by the ability of transformed cells to grow as clones in agar. Radiation from these lamps enhanced direct transformation, and enhanced viral transformation to approximately the same degree. Enhanced transformation was seen with exposures of light that caused no measurable cell killing, which suggests that the induction of new transformants is involved rather than the selection of pre‐existing transformants. Induction is also suggested by post‐irradiation growth kinetics experiments.
CHLORPROMAZINE PHOTOSENSITIZATION–II. FAILURE TO DETECT ANY EVIDENCE FOR INVOLVEMENT OF DNA DAMAGE IN THE PHOTODYNAMIC KILLING OF ESCHERICHIA COLI IN THE PRESENCE OF CHLORPROMAZINE
Authors: Matsuo Itsuro , Ohkido Muneo , Fujita Hitoshi , Suzuki Kenshi
Published: January 2008

Abstract— When a suspension of Escherichia coli was irradiated with near‐UV light in the presence of chlorpromazine (at a concentration below a cytotoxic level), the cells were killed. Efficiency of the photodynamic killing was not influenced by the deficiency of the uvrA gene or the recA gene. Neither phenotypic reversion of E. coli Hs30R (arginine auxotroph) nor induction of lambda prophage in lysogenic bacteria was detected after this treatment.
SPONTANEOUS ORGANIZATION OF TWO XANTHOPHYLL COMPOUNDS IN WATER‐ALCOHOL SOLUTIONS AS SHOWN BY CIRCULAR DICHROISM
Authors: Lematre J. , Maudinas B. , Ernst C.
Published: January 2008

Abstract— Alcoholic solutions of lutein, violeoxanthin and acetylated lutein containing more than 50% water exhibited strong CD signals in the main absorption region of the polyene chromophore.

The CD spectra obtained depended on the water content of the medium and were affected by temperature and detergents.

The spectroscopic changes in absorption and circular dichroism reveal a spontaneous ability of such pigment molecules for a stereospecific multimolecular organization in a hydrophilic environment. The biological significance of these spectroscopic phenomena is also discussed.
THE PHOTOREACTIONS OF 8‐METHOXYPSORALEN WITH TRYPTOPHAN AND LENS PROTEINS*
Authors: Lerman S. , Megaw J. , Willis I.
Published: January 2008

Abstract— We have previously demonstrated that 8‐methoxypsoralen (8‐MOP) can be found in the lenses of rats injected (i.p.) with this drug, and that its presence can lead to a photosensitized enhancement of lenticular fluorescence. The cutaneous photosensitizing properties of psoralens are thought to be mediated via their excited triplet states, resulting in photoaddition cyclobutane products between pyri‐midine bases and 8‐MOP. We have now investigated the possibility that similar types of photoadducts could be generated between 8‐MOP and the aromatic amino acid residues in lens proteins. Our experiments involved in vitro irradiation (at 360 nm) of aqueous solutions of 0.1 mM 8‐MOP plus purified alpha, beta, or gamma crystallins from calf or normal human (under 20 years of age) lenses. UV absorption and fluorescence emission spectra were measured before and after radiation, and aliquots from all experiments were frozen and kept in the dark for subsequent phosphorescence and EPR spectroscopy. Similar experiments were performed with irradiated aqueous solutions of tryptophan or thymine plus 8‐MOP. All controls consisted of solutions kept in the dark. NMR spectra demonstrated that the hydrogen atoms at the 3,4 and 4',5' positions of the 8‐MOP molecule were lost following irradiation, suggesting that these two sites were involved in the photoproduct formed between tryptophan and 8‐MOP. These studies strongly suggest that 8‐MOP is capable of forming photoaddition products with tryptophan and with lens proteins as well as DNA in vivo, resulting in its permanent retention within the ocular lens.
ENHANCED KILLING OF CHINESE HAMSTER CELLS FOLLOWING COMBINED EXPOSURE TO ‘SUNLIGHT’ AND X‐RAYS*
Authors: Han A. , Elkind M. M.
Published: January 2008

Abstract— Enhanced cell killing due to combined exposure to sunlight‐like near‐UV light (Westinghouse Sun Lamps, FS20) and X‐rays, indicative of damage interaction, is observed at all stages of the cell cycle. The greatest interaction is observed in the middle of the DNA synthetic phase. At equal survival, ‘sunlight’ damage is only partly additive to X‐ray damage, and vice versa, whereas in earlier studies we found that far‐UV light (254 nm) produces damage completely additive to X‐ray damage. Loss of damage interaction between radiations is more rapid after a first dose of X‐rays than after a first dose of ‘sunlight’.
PHOTODYNAMIC AND SUNLIGHT INACTIVATION OF ESCHERICHIA COLI STRAINS DIFFERING IN NEAR‐UV SENSITIVITY AND RECOMBINATION PROFICIENCY
Authors: Tuveson R. W. , March Melinda E.
Published: January 2008

Abstract— Stationary cells of four Escherichia coli strains exhibiting all four possible combinations of genes controlling near‐UV sensitivity (nur vs nur+) and recombination proficiency (far‐UV sensitivity; recA1 us recA+) have been inactivated by visible light in the presence of acridine orange (AO, 10µg/ml) and sunlight. The results demonstrate that strains sensitive to near‐UV inactivation are also sensitive to inactivation by visible light in the presence of AO and sunlight irrespective of the recA allele carried by the strain. These results may be interpreted to mean that major mechanisms of inactivation of stationary E. coli cells by near‐UV, visible light in the presence of AO and sunlight are similar and not closely related to the mechanism of inactivation by far‐UV.
THE MECHANISM OF SINGLET‐SINGLET EXCITATION ENERGY TRANSFER FROM CAROTENOIDS TO CHLOROPHYLL
Authors: Naqvi K. Razi
Published: January 2008

Abstract— It is proposed that the light‐harvesting function of carotenoids in photosynthesis requires electron exchange between the energy donor (carotenoids) and the acceptor (antenna Chi molecules); this supports an earlier suggestion by Goedheer (1972) that there exists a close spatial relationship between these pigments in vivo.
FUNCTIONAL DETERGENT PROBES OF MICELLE STRUCTURE. ABSORPTION, FLUORESCENCE AND QUENCHING MEASUREMENTS
Authors: Turro Nicholas J. , Tanimoto Yoshifumi , Gabor Gavriella
Published: January 2008

Abstract— The absorption and fluorescence spectra of two functional ionic detergents containing an indole chromophore have been studied as micelle probes and have been compared to the corresponding spectra of 1‐methylindole. The quenching of the fluorescence of the probes by NO‐2 and Co2+ has also been investigated. Based on the results obtained, it is concluded that 1‐methylindole is associated with the surface of HDTBr micelles, whereas it is located in the interior of SDS micelles. The chromophore of the indole detergents is considered to be located in the interior of HDTBr and SDS micelles.
TEMPERATURE DEPENDENCE OF PHOTOSYNTHETIC EXCITATION TRANSFER—ACTIVATIONLESS TRANSFER
Authors: Sarai Akinori , Yomosa Sigeo
Published: January 2008

Abstract— We have investigated the temperature dependence of photosynthetic excitation transfer by quantum‐mechanical treatment. Our theoretical analyses predict that the temperature dependence of most excitation transfers is quite weak in the relatively high temperature range (kT 100cm‐1), whereas some excitation transfers exhibit complex temperature dependence in the low temperature range due to the environmental effect. The temperature‐independency in the high temperature range results from the fact that most excitation transfers among various Chi forms characterized by different absorption peaks almost satisfy the activationless condition where the energy gap for the excitation transfer matches with the nuclear rearrangement energy. This activationless condition, which has already been noticed in the electron transfers in the reaction center, is suggested to play central roles in the efficient energy conversion in the primary stage of photosynthesis.
BEHAVIOR OF HETEROEXCIMER SYSTEMS IN SINGLE BILAYER LIPOSOMES
Authors: Waka Yasuhiro , Mataga Noboru , Tanaka Fumio
Published: January 2008

Abstract— Behavior of heteroexcimers formed between pyrene moieties incorporated at varying depths from the charged surface of vesicles and exogeneous N, N‐dimethylaniline during the lifetime of excited pyrene moiety have been investigated by means of fluorescence measurements and laser photolysis. Fluorescence studies show that the fluorescence quenching kinetics in liposomes is rather similar to that in homogeneous bulk solutions, in contrast to the case of ordinary micellar solutions. Weak heteroexcimer fluorescence as well as transient absorption bands of ion radicals produced as a consequence of electron transfer from the amine to the excited pyrenyl group were observed. Comparison of the present results with those in homogeneous solutions indicates that the polar environment where dielectric constant is as large as 10 is attained in the hydrocarbon core of the liposomes. The polar environment of the fatty acid chains suggests the presence of water molecules penetrated into the hydrocarbon core.
ORIENTATION OF RETINYLIDENE CHROMOPHORE OF HYPSORHODOPSIN IN FROG RETINA
Authors: Tokunaga Fumio , Sasaki Norihiro , Yoshizawa Tôru
Published: January 2008

Abstract— Hypsorhodopsin and bathorhodopsin were formed in the frog retina by irradiating rhodopsin at liquid He temperature (9 K) with orange light (> 520 nm) and blue light (437 nm), respectively. Hypsorhodopsin was converted to bathorhodopsin in the retina by warming above 32 K in the dark. Similar phenomena were observed in the rod outer segment suspension. A difference spectrum between hypsorhodopsin and bathorhodopsin in the retina produced by warming was almost identical with that in the rod outer segment suspension. This suggests that the transition dipole moment of hypsorhodopsin is parallel to the disk membrane plane which is also parallel to that of bathorhodopsin.
THE REGENERATION OF VISUAL PIGMENTS AND THE CHANGE OF ROD HYPERSENSITIVITY AFTER IRRADIATION BY BLEACHING LIGHT IN FROG RETINA
Authors: Azuma Katsu , Azuma Masami
Published: January 2008

Abstract— The regeneration processes of visual pigments and the dark adaptation processes of rod photoreceptor after irradiation by bleaching light were studied by spectrophotometric, electroretinographic(ERG) methods and the measurement of early receptor potentials (ERPs) in bullfrog retina. After irradiation by bleaching light, rhodopsin in the isolated retina regenerated to an extent depending on the wavelength and intensity of the bleaching light as well as pH. Intense blue light and a weak alkaline environment (pH 7.5–9.5) favoured the regeneration. The regeneration of pigment in the green rods could not be detected in these experiments on the isolated retina. The regeneration of cone pigment was studied by measuring ERPs from both isolated retinas and retinas with pigment epithelium‐choroid complex separated from scleras, which are called PEC‐retinas. In the PEC‐retinas, cone pigment regenerated more rapidly and with better efficiency than in the isolated retinas.

Rod photoreceptors desensitized permanently by bleaching light did not demonstrate hypersensitivity at 0.1 mM [Ca2+]out, which induced hypersensitivity in non‐desensitized photoreceptor, but showed the hypersensitivity when the [Ca2+]out, was lowered further by the addition of EGTA.
INTERMEDIATE PROCESSES IN PHOTOTRANSDUCTION: A STUDY IN DROSOPHILA MUTANTS
Authors: Minke Baruch , Armon Eli
Published: January 2008

Abstract— A variety of procedures were used to modify the light response of Drosophila photoreceptors in order to find out if these manipulations produce effects that mimic some aspects of light adaptation. The ultimate goal of our approach is to use these experimental manipulations to dissect the different stages of the phototransduction process.

The means which were used to modify the light response were as follows: (a) light adaptation of normal photoreceptors, (b) exposure of normal photoreceptors to various levels of CO2 (c) light adaptation of the trp Drosophila mutant in which the receptor potential decays to baseline during illumination, (d) exposure of the temperature sensitive norpAH52 mutant of Drosophila to elevated temperatures. Intensity‐response functions were obtained using intracellular and extracellular recordings. The maximal response amplitude (Vmax) was then plotted as a function of the light intensity (s̀) which evoked a response of half maximal amplitude. This plot was used to compare the effects of the procedures described above. Qualitatively all the manipulations had similar effects, they reduced Vmax and shifted s̀ to higher levels of light intensity, however, quantitatively the various effects were different.

The finding that each experimental manipulation gave a different Vmax versus s̀ plot suggests that they affect different stages in phototransduction. We suggest that the slope of the Vmax versus a function can be interpreted in terms of an ordered cascade of events in phototransduction. This interpretation might give us a tool to distinguish between early and late stages in phototransduction.
ABSORPTION, LUMINESCENCE, SOLVENT‐INDUCED CIRCULAR DICHROISM AND1H NMR STUDY OF BILIRUBIN DIMETHYL ESTER: OBSERVATION OF DIFFERENT FORMS IN SOLUTION*
Authors: Holzwarth Alfred R. , Langer Elisabeth , Lehner Harald , Schaffner Kurt
Published: January 2008

Abstract—

Bilirubin dimethyl ester (I) has been studied by absorption, fluorescence and fluorescence excitation, solvent‐induced circular dichroism, and 1H NMR techniques. The existence of two forms of the solute involving either or both syn‐anti dipyrromethenone and lactam‐lactim equilibria was established, and the occurrence of even more forms remains possible. The relative population is strongly influenced by the nature of the solvent and by temperature. Thus, the population of one species predominates in ethanol. What is presumed to be the same species increases on cooling in all solvents, while the population of another species is strongly preferred in dichloromethane. In other solvents appreciable populations of both forms persist over the temperature range 77–300 K.
CHLOROPHYLL PHOTOCHEMISTRY IN CONDENSED MEDIA—II. TRIPLET STATE QUENCHING AND ELECTRON TRANSFER TO QUINONE IN LIPOSOMES*
Authors: Hurley John K. , Castelli Francesco , Tollin Gordon
Published: January 2008

Abstract—

The fate of excitation energy and electron transfer to quinones within Chl‐a‐containing phosphatidyl choline liposomes has been investigated. The bilayer membrane of the liposome stabilizes the Chl triplet state, as evidenced by a three‐fold increase in the lifetime over that observed in ethanol solution. The relative triplet yield follows the relative fluorescence yield, indicative of quenching at the singlet level. Triplet state lifetimes are markedly shortened as the Chl concentration is increased, demonstrating that quenching occurs at the triplet level as well. This process is shown to be due to a collisional de‐excitation. In the presence of quinones, the Chl triplet reduces the quinone resulting in production of long‐lived electron transfer products. The percent conversion of Chl triplet to cation radical when benzoquinone is employed as acceptor is approximately 60 ± 10%, which is slightly less than in ethanol solution (70 ± 10%). The lifetime of the radical, however, can be as much as 1900 times longer. With respect to potentially useful photochemical energy conversion, the magnitude of this increased lifetime is far more significant than is the decreased radical yield.
EXTERNAL HEAVY ATOM EFFECT IN THE ENERGY TRANSFER FROM TETRAMETHYL‐1,2‐DIOXETANE CHEMI‐EXCITED ACETONE TO ANTHRACENE
Authors: Adam Waldemar , Cilento Giuseppe , Zinner Klaus
Published: January 2008

Abstract—

Generation of the fluorescent state of anthracene by energy transfer from chemi‐excited acetone is remarkably more efficient in bromobenzene than in benzene. Triplet‐triplet energy transfer populates the second triplet of the acceptor and is followed by intersystem crossing (ISC) to the fluorescent state. It is only on the latter ISC step that the external heavy atom perturbation operates. However, with 9,10‐dibromoanthracene as acceptor, spin‐orbital coupling also increases the transfer step and more in bromobenzene than in benzene. A possible inference from this work is that 9,10‐diphenyl‐anthracene, which is commonly used to count singlets, may to some extent also count triplets.
ENERGY TRANSFER FROM CAROTENOID POLYENES TO PORPHYRINS: A LIGHT‐HARVESTING ANTENNA
Authors: Moore Ana L. , Dirks Gary , Gust Devens , Moore Thomas A.
Published: January 2008

Abstract—

Carotenoid to porphyrin singlet‐singlet energy transfer has been observed in a new covalently linked carotenoid‐porphyrin ester. Nuclear magnetic resonance studies reveal that the relatively high energy transfer efficiency (˜ 25%) is a result of a stacked conformation in which the 26 π electron carotenoid chromophore resides ˜4–5 Å above the mean porphyrin plane. Substantial quenching of porphyrin fluorescence was also observed. Implications for the mechanism of energy transfer and possible applications to synthetic solar energy conversions systems are discussed.
Z/E PHOTOISOMERIZATION OF UROCANIC ACID*
Authors: Morrison H. , Avnir D. , Bernasconi C. , Fagan G.
Published: January 2008

Abstract—

The E ⇆ Z photoisomerization of the title compound (UA) (a naturally occurring sunscreen) has been studied in aqueous solution. At a UA concentration of 6mM and using 313nm excitation, φE→z= 0.52, φZ→E= 0.47 and the photostationary state is 34% E. Under these conditions, loss of UA is minimal. Low energy triplet quenchers fail to impede the isomerization, but the reaction can be induced by several triplet sensitizers. The ET for UA is estimated to be approximately 55 kcal/mol.
SPECIFIC PHOTOCOUPLING OF 5‐BROMOURIDINE TO TRYPTOPHAN IN AQUEOUS FROZEN SOLUTION§
Authors: Saito I. , Ito S. , Matsuura T. , Hélène C.
Published: January 2008

Abstract—5‐Bromouridine (BrUd) photochemically reacted with l‐tryptophan (trp) only in aqueous frozen solution giving rise to 2‐[1,2,3,4‐tetrahydro‐1‐(β‐d‐ribofuranosyl)‐2,4‐dioxo‐5‐pyrimidinyl]‐l‐tryptophan (1a). Under similar conditions irradiation of 5‐bromouracil (BrU) and trp gave the corresponding coupled product 2. Addition of acetone, potassium carbonate or sodium chloride to the frozen system completely inhibited the photocoupling reaction. These photocoupling reactions are suggested to proceed via mixed aggregate formation between trp and BrUd (or BrU) in frozen aqueous solution. Stacking interactions in these aggregates are characterized by an efficient quenching of trp fluorescence by BrUd. Under the same conditions other amino acids such as phenylalanine, tyrosine, histidine and lysine did not react with BrUd, indicating that the photocoupling of BrUd (or BrU) is specific for trp.
THE SENSITIVITY OF TRICHOMONAS VAGINALIS AND TRICHOMONAS GALLINAE TO ULTRAVIOLET RADIATION
Authors: Daly James J. , Baker Max L. , Burton Stanley B.
Published: January 2008

Abstract The formation of colonies in solid medium was used as a criterion of viability to determine the effect of ultraviolet radiation on Trichomonas vaginalis. Both viability (colony) counts and total cell (hemocytometer) counts were used to estimate physiological ages of cell populations to be irradiated. Washed‐cell suspensions in 0.6% saline were exposed to far‐ (254 nm) and near‐UV (300–400 nm) radiation and dose‐response survival curves were constructed from colony counts. The effect of far‐UV was found to be independent of growth phase with the D0 for exponential, early stationary, and late stationary cells 2.6, 2.7, and 2.7 J/m2, respectively. Survival to near‐UV increased with the age of cells with the estimated D50 being 216 J/m2 for exponential cells, 1360 J/m2 for early stationary cells, and 4200 J/m2 for late stationary cells. Exponential cells of Trichomonas gallinae irradiated with near‐UV had a D50 of 340 J/m2. T. vaginalis is highly sensitive to far‐UV relative to protozoa. T. vaginalis and T. gallinae are highly sensitive to near‐UV relative to other microorganisms.
DEPENDENCE ON STAGE OF GROWTH OF MAMMALIAN CELL SENSITIVITY TO NEAR‐UV IRRADIATION*
Authors: Griego Viola M. , Webb Robert B. , Matsushita Tatsuo
Published: January 2008

Abstract The variable sensitivity of exponentially growing mouse myeloma cells (66.2 subclone of MPC11) to monochromatic near‐UV (365 nm) radiation was studied by determination of the relative cloning efficiency (i.e. survival) of cells in soft agar. Maximum sensitivity of the cells to near‐UV light was found during the middle and late stages of exponential growth when the survival was only one‐tenth of that during the early stage of growth. In addition, the shapes of near‐UV survival curves changed with the stage of the cells irradiated. These data indicate that stages of growth can substantially alter the response of mammalian cells to near‐UV radiation. These data further suggest the importance of testing the response of the cells throughout the growth employed in the experimental procedure.
PHOTOREPAIR IN LARVAL ANCHOVY, ENGRAULIS MORDAX
Authors: Kaupp Sandor E. , Hunter John R.
Published: January 2008

Abstract Photorepair of UV‐B lesions occurred in embryonic northern anchovy larvae. The photoreactive fluence rate required to fully activate photorepair mechanisms was less than 10% of that available from the sun on a clear day in March (33N). Even with UV–B enhancement from ozone depletion, sufficient photoreactive fluence exists in the sea to ensure maximal photorepair of UV damage in anchovy larvae.
THE EFFECT OF PROTOPORPHYRIN ON HISTAMINE SECRETION BY RAT PERITONEAL MAST CELLS: A DUAL PHOTOTOXIC REACTION
Authors: Ortner Mary J. , Abhold Raymond H. , Chignell Colin F.
Published: January 2008

Abstract— Protoporphyrin‐induced phototoxicity in rat peritoneal mast cells was manifested either by inhibition of 48/80‐stimulated histamine secretion or by cell lysis. At a protoporphyrin concentration of 100ng/m/ (0.17 μM), histamine secretion was completely inhibited after 30min illumination. After initiation, the inhibited state progressed in the dark, and was irreversible, however, it did not develop into cell lysis. More severe phototoxic reactions in mast cells could not be produced by increasing the PP concentration or the incubation time; however, cell lysis was evoked by increasing the light intensity between 180–950W/m2, using a light source with emission maxima in the 350–470nm region. Dual phototoxic effects could also be demonstrated in erythrocytes by manipulating the illumination conditions. Increased resistance to osmotic lysis was seen under moderate conditions, and decreased resistance and cell lysis were seen under severe conditions. In the absence of protoporphyrin, the effect of light alone on mast cells was similar to protoporphyrin‐phototoxicity, although the light intensities required were higher both for inhibition (60–130W/m2) and lysis (280–950W/m2). The data therefore indicate that certain cell functions can be specifically disrupted by phototoxic reactions that are not cytotoxic; however, phototoxic reactions that lead to severe membrane protein denaturation and cell lysis also occur. The manifestation of these dual effects depends on the intensity of illumination in the 350–470nm region.