bluuebunny/crossref_metadata_2025 huggingface dataset:
TRIPLET EXCITED STATE OF COUMARIN AND 4'5‘ DIHYDROPSORALEN: REACTION WITH NUCLEIC ACID BASES AND AMINO ACIDS
Authors: Land E. J. , Truscott T. G.
Published: January 2008

Abstract—The triplet‐triplet absorption spectra of coumarin, 5.7 dimethoxycoumarin and the furocoumarin 4'5′ dihydropsoralen. a model for 4'5′ psoralen‐pyrimidine mono adducts, have been determined by the techniques of pulse radiolysis and laser flash photolysis. The extinction coefficients of the triplet transitions have been measured and used to determine the singlet → triplet intersystem crossing quantum yields for 347 nm excitation in water. Reaction rate constants for coumarin and 4'5′ dihydropsoralen triplets with various pyrimidine and purine nucleic acid bases, and amino acids, have been measured. Long‐lived transient absorptions detected after quenching coumarin and 4'5′ dihydropsoralen triplets with tryptophan are assigned to mixtures of the corresponding coumarin radical anion and the tryptophan radical cation. The spectra of the radical anions of coumarin and 4'5′ dihydropsoralen were established using pulse radiolysis of the coumarins in aqueous formate. It is suggested that coumarins and furocoumarin triplets are quenched by nucleic acid bases and amino acids via a chargetransfer mechanism.
NETROPSIN: INTERACTION WITH ULTRAVIOLET IRRADIATED DNA
Authors: Sutherland John Clark , Duval John F. , Farland William H. , Griffin Kathleen Pietruszka
Published: January 2008

Abstract—Ultraviolet irradiation of double‐stranded DNA reduces the circular dichroism (i < 300 nm) induced when the basic peptide antibiotic netropsin (Nt) is added to DNA subsequent to thc irradiation compared to the CD induced by the same concentrations of Nt added to unirradiated DNA. Nt is known to bind to A T base pairs in duplex DNA but will not bind to single‐stranded DNA. The reduction in the maximum induced CD observed with saturating concentrations of Nt is a linear function of the concentration of pyrimidine dimers which. along with other dinucleotide photoproducts. form short disrupted regions in duplex DNA. The decrease in the CD of Nt bound to irradiated DNA could be due to elimination of potential Nt sites in the vicinity of a dimer. reduction in the average magnitude of the CD of Nt bound near a dimer or various combinations of these effects. In addition there is a reduction in the average binding constant for Nt bound to irradiated DNA compared to unirradiated DNA suggesting that formation of dinucleotide photoproducts either tends to preferentially eliminate the tighter binding sites or that tighter sites are converted to weaker ones. A simple model suggests that no more than one‐third to one‐half of the pyrimidine dimcrs formed in DNA completely eliminate a Nt site.
PHOTOINITIATION OF SPORANGIOPHORES IN PHYCOMYCES MUTANTS DEFICIENT IN PHOTOTROPISM AND IN MUTANTS LACKING β‐CAROTENE
Authors: Galland Paul , Russo Vincenzo E. A.
Published: January 2008

Abstract—The formation of sporangiophores from mature Phycomyces mycelium is inhibited in a closed system. Irradiation of the mycelium with blue light reverses the inhibition of spordngiophore formation. Dose response curves for this reaction are established for wild type. β‐caroteneless mutants and for mutants that are deficient in phototropism.

Phototropic‐negative mutants. altered in genes madA and madB, have a raised threshold in this light reaction. whereas mutants deficient in genes madD to madG are unaffected. β‐caroteneless mutants deficient in genes carA, carB, or carR have a threshold raised by a factor of 100–2000 depending on the amount of residual synthesis of β‐carotene.
BIOLOGICAL EFFECTS OF NEAR‐UV RADIATION 2‘‐ACETYLFORMANILIDE‐SENSITIZED FORMATION OF HYDROGEN PEROXIDE FROM NUCLEOSIDES AND NUCLEOTIDES
Authors: McCormick J. P. , Oczos A.
Published: January 2008

Abstraet—2′‐Acetylformanilide has been found to be an effective, near‐ultraviolet (300–380 nm) sensitizer for the photooxidation of nucleosides and nucleotides in aqueous solution, with hydrogen peroxide being formed in high yield. The decreasing order of hydrogen peroxide formation and substrate destruction was found to be: guanosine. adenosine, thymidine, uridine and cytidine. The process was highly pH dependent, low pH being most favorable for photooxidation. Experiments using deuterium oxide and superoxide dismutase indicate that both singlet oxygen and superoxide ion can be involved in hydrogen peroxide formation.
SENSITIVITY OF MONONUCLEAR CELLS TO UV RADIATION
Authors: Morison Warwick L. , Parrish John A. , Anderson R. Rox , Bloch Kurt J.
Published: January 2008

Abstract—The viability of peripheral blood mononuclear cells, as measured by trypan blue dye exclusion, is decreased by exposure to UV radiation in vitro. The toxicity of the UV radiation is doseand wavelength‐dependent; UVC is approximately 10 times more effective than UVB and 105 times more effective than UVA.
STRUCTURAL FACTORS CONTROLLING THE ACTION OF UV LIGHT IN NUCLEIC ACIDS*
Authors: Lang H. , Zimmer Ch.
Published: January 2008

Abstract— UV light induced conformational effects of different deoxyoligonucleotides and deoxypolynucleotides containing thymine and adenine residues are investigated by means of CD measurements and quantum yield calculations. UV‐irradiation at the wavelengths 254, 280 and 313 nm indicate that unsensitized irradiation at low doses leads to thymine photoproduct formation of non‐cyclobutane type.

In contrast to that irradiation at 313 nm in the presence of acetophenone causes different changes in the CD spectra due to the formation of thymine dimers of the cyclobutane type structure.

Quantum yield calculations demonstrate a pronounced dependence of the photoproduct formation on the nucleotide sequence of the oligomers. Thus, clustering of thymine dimer formation can be neglected. Adenine photoproducts in the (A.T) containing oligomers are only formed at higher fluences. > 1.5 × 104 J/m2 and are biological less important events.
PHOTOCHEMISTRY AND PHOTOPHYSICS OF GUANINE‐CONTAINING DINUCLEOSIDES
Authors: Morgan James P. , Callis Patrik R.
Published: January 2008

Abstract— Yields and action spectra are reported for photochemistry. fluorescence. and total lumincscence at 405 nm due to UV excitation (240–300 nm) or dilutc (‐0.1 mM) solutions or guanosine 5–monophosphate (GMP) and the dinucleosides linking guanine with adenine (ApG and GpA). cytosine (CpG) and uracil (GpU) in neutral ethylene glycol‐water (7:3) glasses at 140–165 K. Phosphorescence lifetimes were determined at 140 K. Less complete data are presented for GpC, UpG and dpGpT. Quantum yields for all three processes were usually found to increase as the excitation wavelength increases. Although intramolecular exciplex formation was not dominant under these conditions interactions were strong enough to frustrate attempts at interpretation of results within the Forster very weak coupling framework. There is evidence that the GMP photochemistry proceeds from the triplet state. Surprisingly, this photochemistry is not quenched in ApG, GpA, and dpGpT at 163 K although the adenine (A) and thymine (T) moieties are known to have lower triplet states. At 140 K the phosphorescence from ApG and GpA was entirely characteristic of A but both G and T components were observed from dpGpT.
INTERACTION BETWEEN DNA AND 8–METHOXYPSORALEN STUDIED BY LINEAR DICHROISM
Authors: Tjerneld Folke , Nordén Bengt , Ljunccren Bo
Published: January 2008

Abstract— High sensitivity linear dichroism on DNA oriented by flow is shown to provide conclusive information about the interaction with 8–methoxypsoralen (8–MOP) both in the dark and by irradiation. 8–MOP forms directly in the dark a weak complex with DNA with a structure consistent with the intercalation model of Lerman. When aqueous DNA‐psoralen solutions are UV irradiated (30800 nm). a photoadduct is formed. By comparison with experiments in ice matrix, it is suggested that it is the primarily bound 8–MOP that is responsible for the final product. It is inferred that this product is the 41,5I‐photoadduct of 8–MOP. The orientation of the photo adduct on DNA is not consistent with intercalation.
PHOTODECOMPOSITION OF CATECHOLAMINES. PHOTOPRODUCTS, QUANTUM YIELDS AND ACTION SPECTRUM OF ADRENALINE
Authors: Mol N. J. de , van Henegouwen G. M. J. Beyersbergen , Gerritsma K. W.
Published: January 2008

Abstract—

The photochemical decomposition of several catecholamines in aqueous solution was investigated. The respective aminochromes were found to be products of adrenaline and isoprenaline. Irradiation of adrenochrome and N‐isopropylnoradrenochrome produced their respective 5, 6‐dihydroxyindoles in addition to the ultimate formation of melanine. No trihydroxyindoles could be detected amongst the photoproducts of catecholamines.

The action spectrum of adrenaline suggested that the catecholamine itself, in excited state, initiated the first step in the transformation process. The quantum yields for the decomposition were determined for several catecholamines: N‐alkyl compounds. decompose more rapidly under influence of light (λ 254 nm) than those with an unsubstituted amino group. In determining the quantum yields the use of corrections for the inner filter effect could be avoided.
INHIBITION OF 15‐HYDROXYPROSTAGLANDIN DEHYDROGENASE ACTIVITY BY NEAR‐ULTRAVIOLET LIGHT AND TRYPTOPHAN PHOTOPRODUCTS*
Authors: Sun Ming , Zigman Seymour , Tai Hsin‐Hsiung
Published: January 2008

Abstract—

The activity of NAD+ dependent 15‐hydroxyprostaglandin dehydrogenase. the major prosta‐glandin catabolic enzyme, was found to be effectively inhibited by near‐UV radiation and by tryptophan photoproduct. Both free tryptophan and tryptophan photoproducts enhance the inhibitory action of near‐UV light on the enzyme.
THE CONTRIBUTION OF RHODOSPZRZLLUM RUBRUM FERREDOXIN II TO IN VIVO EPR SIGNALS AND ITS ROLE IN ELECTRON TRANSPORT
Authors: Corker G. A. , Henkin B. M. , Sharpe S. A.
Published: January 2008

Abstract—

Evidence is presented that Fd II, an iron‐sulfur protein containing 4 irons and 4 acid‐labile sulfurs, is responsible for a number of signals previously reported detectable in cells of R. rubrum. When oxidized, Fd II exhibits a g = 2.012 EPR signal which is readily detected in R. rubrum cells. In our hands, Fd II is photochemically reduced to an EPR‐silent product contrary to the results of other investigators. However. in the presence of reducing agents. the reduced form is apparently denatured upon freezing. The denatured form exhibits EPR signals similar to some also previously observed in whole cells.

Fd II catalyzes the ascorbate‐DCPIP linked photoreduction of NAD with R. rubrum chromatophores even in the presence of an inhibitor which suppresses the formation of pH and emf gradients. This result raises the possibility of a role for Fd II in non‐cyclic electron transport in R. rubrum.
LASER PHOTOLYSIS STUDIES OF QUINONE REDUCTION BY PHEOPHYTIN a IN ALCOHOL SOLUTION
Authors: Castelli Francesco , Cheddar Glen , Rizzuto Frank , Tollin Gordon
Published: January 2008

Abstract‐ Upon laser photolysis of pheophytin‐benzoquinone solutions in ethanol, transients due to the pheophytin triplet state (Pt), an exciplex (Pδ+ Qδ‐), the pheophytin cation radical (P+) and the semiquinone radical (Q‐) can be observed. Kinetic analysis indicates that the evolution of these transients at times longer than one microsecond is due to the decay of the exciplex with the concomitant formation of P+ and Q‐, reverse electron transfer to form P and Q, solvent oxidation by P+, and Q‐ disproportionation. In support of the suggested solvent oxidation reaction, a large deuterium isotope effect is observed upon changing the solvent from methanol to its fully‐deuterated counterpart. Comparisons are made between these results and those obtained with chlorophyll as described in the preceding paper.
MULTIPLE EXCITATIONS AND REACTION YIELDS IN PHOTOSYNTHETIC SYSTEMS
Authors: Mauzerall D.
Published: January 2008

Abstract—

Alternative explanations of the limited yield of product when bacterial reaction centers are excited by intense ps pulses (Moskowitz and Malley, Photochem. Photohiol. 27 55, 1978) are given. These alternatives, based on photoreversal or multitrap effects, can be experimentally distinguished by a predicted wavelength variation or by the effect of a second flash.
RAPID AND SENSITIVE OPTICAL ROTATION MEASUREMENT: KINETICS OF CONFORMATIONAL CHANGE OF RHODOPSIN INTERMEDIATE
Authors: Tsuda Motoyuki
Published: January 2008

Abstract—

A rapid and sensitive optical rotation (OR) measurement system using laser light has been developed to meet the demands of flash‐photolysis experiments. The optimal OR resolution of the apparatus is 0.3mdeg with 10 μs time constant with single shot. The OR resolution could be easily improved less than 0.1 mdeg with accumulation of data by a kinetic processor. Applications are briefly described for the study of transient conformational change of photochemical intermediates of octopus rhodopsin following a blue light flash.
PHOTOCHEMICAL REACTION BETWEEN PROTEIN AND NUCLEIC ACIDS: PHOTOADDITION OF TRYPTOPHAN TO PYRIMIDINE BASES*1
Authors: Reeve A. E. , Hopkins T. R.
Published: January 2008

Abstract— The photochemical interactions between tryptophan and nucleic acid bases were studied. When aqueous solutions of tryptophan were irradiated (Λ > 260 nm) at neutral pH in the presence of each of the nucleic acid bases, pyrimidine bases but not purine bases were altered. Air was found to decrease the rate of reaction. Two classes of photoproducts were isolated by thin layer and ion‐exchange chromatography and partially characterized. One was the dihydro‐pyrimidine forms of the base (see Reeve and Hopkins, 1979) and the other consisted of tryptophan‐pyrimidine photoadducts. Four tryptophan‐uracil and two tryptophan‐thymine adducts each with a 1:1 molecular stochiometry were found. Spectroscopic measurements and a positive reaction with Ehrlich's reagent indicate that the indole nucleus remained intact, but that the pyrimidine base was reduced at the 5, 6 double bond. The absence of a positive ninhydrin reaction and the effect of pH on the quantum yield of the photoadduct formation indicated that the ionized a‐amino acid group of tryptophan was involved in photoadduct formation. Indole derivatives lacking an a‐amino group were also found to form photoadducts with pyrimidine bases.

The experimental results are consistent with a reaction mechanism involving tryptophan excitation to the first excited singlet state as the initial event. Radical scavenging experiments indicate that tryptophan free radicals, formed by electron dissociation from the excited state, react with the ground state pyrimidine.
EFFECT OF METAL IONS ON THE LUMINESCENCE OF ACRIDINE DYES BOUND TO DNA
Authors: Prusik Thaddeus , Kolubayev Tatiana , Morelli Michael J. , Brenner Henry C.
Published: January 2008

Abstract— The luminescence of acridine dyes intercalated in DNA was studied as a function of the concurrent binding of metal ions to DNA, in an effort to deduce specific site interactions of the dyes. Two dyes, proflavine (PF) and acridine orange (AO), and two metal ions, silver and mercuric, were used. Both ions quench the fluorescence of the dyes in aqueous solution at room temperature. The metal ions have a different effect on the fluorescence of these dyes when they are intercalated between the base pairs of DNA. The fluorescence of AO is decreased when silver is bound, while the fluorescence of PF is enhanced. Since Ag+ initially binds to GC sites in DNA, which quench the PF fluorescence, it ostensibly ‘turns off’ the quenching by DNA at these sites, and this effect is greater than the quenching effect of the silver ion itself. Hg2+ ion initially binds to AT sites in DNA. Since both dyes fluoresce from AT sites, Hg2+ is expected to quench their fluorescence. This behavior is observed at low r (metal ion/base). At higher r values, however, where Hg2+ is expected to begin binding to GC sites, the fluorescence of PF is enhanced. These quenching turn‐off effects are tentatively interpreted in terms of a change in the structure of the dye/DNA complex which occurs when a metal ion binds at the intercalation site. At 77 K. no fluorescence enhancement is observed when metal ions bind; Ag+ quenches the fluorescence and enhances the phosphorescence of both dyes. Qualitatively similar results are obtained with Hg2+.
FLUORESCENT TAUTOMERS AND THE APPARENT PHOTOPHYSICS OF ADENINE AND GUANINE
Authors: Wilson Robert W. , Callis Patrik R.
Published: January 2008

Abstract— Fluorescence, absorption and fluorescence excitation spectra, and quantum yields of 0.02 mM solutions of adenine, 7‐methyladenine (7‐MA), guanine and 7‐melhylguanine (7‐MG) are presented for excitation with240–300 nm light. The solvent is neutral ethylene glycol‐water (70:30 v/v) in the temperature range140–165 K. Phosphorescence spectra of adenine and 7‐MA at 140 K are also presented. The excitation spectrum of adenine shows vibrational structure, whereas the absorption does not. However, the fluorescence of adenine shows the vibrational structure, as do the absorption, fluorescence and excitation spectra of 7‐MA. The results confirm (and reinforce) the notion that luminescence from adenine under these conditions is from the N7–H tautomer, instead of the more abundant N9–H form. In a similar fashion, the data from guanine and 7‐MG strongly suggest that the luminescence from guanine is also mostly from the N7–H tautomer.
LIGHT AND pH INDUCED CHANGES IN THE SURFACE PRESSURE‐AREA ISOTHERMS OF BACTERIORHODOPSIN
Authors: Vivino A. , Berns D. S. , Brody S. S.
Published: January 2008

Abstract— Pressure‐area isotherms of monolayers of purple membrane fragments were measured at an air‐water interface. The pH of the aqueous phase was varied from 2 to 10. Over the pH range 5 to 9 the area/molecule of bacteriorhodopsin was constant and illumination of the film had no effect on the isotherms.

At pH's more acid than 5 and more alkaline than 9, there were large decreases in area/molecule. Under these conditions of extreme pH the monolayer was very sensitive to light. Illumination resulted in irreversible increases in area/molecule.
PHOTOCHEMICAL REACTIONS BETWEEN TRYPTOPHAN AND POLYNUCLEOTIDES*
Authors: Reeve A. E. , Hopkins T. R.
Published: January 2008

Abstract— Anaerobic solutions of 14C labelled tryptophan and single‐stranded synthetic polyribonucleotide form adducts when irradiated with UV light at wavelengths longer than 270 nm. These adducts are stable to cold 10% trichloroacetic acid and are also more resistant to hydrolysis catalyzed by bovine ribonuclease A than non‐irradiated controls. All polyribonucleotides reacted with trp to some extent with reactivities in the order poly rU > poly rC = poly rA > poly rG.
ACTION SPECTRUM FOR GROWTH DELAY INDUCED BY NEAR‐ULTRAVIOLET LIGHT IN E. coli B/r K*
Authors: Kubitschek H. E. , Peak M. J.
Published: January 2008

Abstract— The action spectrum for growth delay induced by near‐uv light was determined for Escherichia coli B/r growing in a defined medium. This spectrum agrees with and extends that determined earlier by Jagger and his co‐workers for E. coli B growing in nutrient broth. The extended spectrum is indistinguishable from the absorption spectrum for 4‐thiouridine above 320 nm, but deviates significantly at wavelengths shorter than this from the spectrum for 8–13 link formation in transfer RNA containing 4‐thiouridine at position 8. These results extend the evidence that 4‐thiouridine in transfer RNA is the chromophore for near‐UV induction of growth delay, but weaken the case for linkage of a pyrimidine at position 13 in transfer RNA as the mechanism of growth delay.
QUENCHING OF INTRAMOLECULAR AMINE‐HYDROCARBON EXCIPLEX FLUORESCENCE BY WATER
Authors: Ibemesi J. A. , El‐Bayoumi M. Ashraf
Published: January 2008

Abstract— The quenching of intramolecular exciplex fluorescence in 2,6‐bis(methylamino)naphtha]ene, (II), 2,6‐bis(/V‐methyl, methylamino)naphthalene, (III) and 2,6‐bis(N‐dimethy], methylamino)naphthalene, (IV) by water was investigated. Exciplex fluorescence intensity decreased continuously with increase in water concentration; while monomer fluorescence intensity remained constant up to 25% of water, followed by a rapid increase in intensity.

Absorption spectra showed that specific interaction occurred between water and ground state amine molecules at high concentrations (25% by volume) of water. These observations were interpreted in terms of a static quenching involving the interaction of water with the ground‐state amine and a dynamic quenching involving the interactions of water with the exciplex. Our observations explain the greater efficiency of exciplex‐fluorescence quenching by protic polar solvents.
EXCITED STATES OF DNA AND ITS COMPONENTS AT ROOM TEMPERATURE—III. SPECTRA, POLARISATION AND QUANTUM YIELDS OF EMISSIONS FROM ApA AND poly rA*
Authors: Morgan James P. , Daniels Malcolm
Published: January 2008

Abstract— Corrected normalised emission spectra from 300 to 480 nm and their polarisation are reported for neutral and poly rA at room temperature. Yields are 4 times (ApA) and 6 times (poly rA) greater than the monomer. Comparison of emission spectra and polarisation spectra demonstrates heterogeneity of emission and, following attempts at spectral synthesis, comparison with experimental reference spectra allows the observed total emission spectra to be resolved into four components assigned as I monomer‐like emission, II excimer fluorescence, HI monomer phosphorescence, IV excimer phosphorescence; the polarisation of the excimer fluorescences of ApA and poly rA are deduced. The observations can be understood quantitatively using a simple stacking model with excimer emissions originating in the stacked components. Quantitative differences between ApA and poly rA are due to their different hypochromism and extent of stacking. Differences of polarisation are attributed to different stacking geometries, and the directional properties of the transition moment suggest that the excimer fluorescence is largely charge‐resonance in nature.
THE PHOTOCHEMICAL QUANTUM YIELD FOR THE SELF‐SENSITIZED PHOTOOXIDATION OF BILIRUBIN. EVIDENCE FOR OXYGEN‐INDUCED INTERSYSTEM CROSSING AT HIGH OXYGEN CONCENTRATIONS
Authors: Matheson I. B. C. , Curry N. U. , Lee John
Published: January 2008

Abstract— The in vitro self‐sensitized photooxygenation of bilirubin has been studied as a function of oxygen and bilirubin concentrations in a variety of solvents. The results which have been interpreted in terms of a singlet oxygen reaction indicate bilirubin triplet yields of 0.05–0.08 and further show that oxygen induced intersystem crossing is appreciable at high oxygen concentrations. The results also show that the quantum efficiency of the photochemical reaction would be of the order of 1% at the bilirubin and oxygen concentrations typical for the in vivo treatment of neonatal jaundice.
SYSTEMATIC ERRORS DUE TO EXCITATION PULSE WIDTH IN FAST KINETIC TECHNIQUES
Authors: Duddell D. A.
Published: January 2008

Abstract— Convolution of the decay function with the excitation pulse function leads to systematic error in both kinetic and spectral analysis of transients. The error in rate constant determination for a first order decay can be kept to about 1% if the decay half‐life is equal to the pulse half‐width and to well below 1% for half‐lives equal to or longer than twice the half‐width. The errors in transient absorbance measurements are much greater. Only if the half‐life approaches 200 times the pulse half‐width is the error reduced to 1%. It is suggested that spectral measurements should be corrected for this error.
A THEORETICAL STUDY OF EXCITONS IN CHLOROPHYLL a PHOTOSYSTEMS ON A PICOSECOND TIMESCALE
Authors: Shipman Lester L.
Published: January 2008

Abstract— The creation and decay of singlet excitons in structurally‐explicit Chi a photosystems were investigated by numerical integration of the appropriate Master Equations. The antenna chlorophylls were excited by a simulated 6ps Gaussian light pulse. Positions and orientations for the antenna chlorophylls were randomly generated within regions whose size and shape were chosen to be appropriate for the particles observed in freeze‐fractured photosynthetic membranes. Among the variables considered were chlorophyll concentration, depth of the trap (i.e. P680 or P700), and the R0 parameter for Förster transfer. Among the properties considered were antenna fluorescence lifetime; detrapping rates; the instantaneous and integrated quantum yields for antenna fluorescence and intersystem crossing; and the instantaneous and integrated quantum yields for trap fluorescence, intersystem crossing, and photochemistry. A variety of experimental evidence was used as input to the computational model.
CHLORPROMAZINE PHOTOSENSITIZATION—I. EFFECT OF NEAR‐UV IRRADIATION ON BACTERIOPHAGES SENSITIZED WITH CHLORPROMAZINE
Authors: Matsuo Itsuro , Ohkido Muneo , Fijita Hitoshi , Suzuki Kenshi
Published: January 2008

Abstract— Both DNA bacteriophage and RNA bacteriophage were inactivated when they were irradiated with near‐UV light (black light) in the presence of chlorpromazine. The far‐UV sensitive mutants of T4D, i.e. T4Dv, T4Dpx and T4Dy, were no more sensitive to near‐UV light plus chlorpromazine than the wild type. Electron microscopic observations showed that adsorption of T4D was greatly influenced by the treatment. The present results may indicate that the inactivation of T4D is due to the loss of adsorption caused by impairment in the tail or the tail fiber protein rather than the inactivation of DNA.
BIOCHEMISTRY OF CENTIPEDE BIOLUMINESCENCE*
Authors: Anderson James Michael
Published: January 2008

Abstract— The centipede (Orphaneous brevilabiatus) secretes a bioluminescent slime. The corrected emission spectrum of this luminescence was found to have maxima at about 510 and 480 nm. The reaction was found to require both a luciferin and luciferase and showed an unusually low pH optimum (4.6). Oxygen was required for the reaction, but oxygen could interact with one of the components allowing for anaerobic light emission.
A RAPID AND EFFICIENT METHOD TO PREPARE CHLOROPHYLL A AND B FROM LEAVES
Authors: Omata Tatsuo , Murata Norio
Published: January 2008

Abstract— Highly purified Chi a and b were prepared from spinach leaves in a short time by a combined use of the column chromatography with DEAE‐Sepharose CL‐6B and Sepharose CL‐6B. The former chromatography eliminated carotenoids, phaeophytin and chlorophyllide, and the latter chromatography efficiently separated Chi a and b.
LIMITING REACTIONS IN HYDROGEN PHOTOPRODUCTION BY CHLOROPLASTS AND HYDROGENASE
Authors: Rosen Michael M. , Krasna Alvin I.
Published: January 2008

Abstract— Hydrogen was photoproduced from water in a system containing isolated chloroplasts, hy‐drogenase, a coupling electron carrier (ferredoxin or methyl viologen), and an oxygen scavenger. The rate and extent of hydrogen production anaerobically was much less than the rate of aerobic electron‐carrier reduction by chloroplasts and was not limited by hydrogenase. The limiting reaction in the coupled system was the extent of reduction of methyl viologen anaerobically rather than its oxidation by oxygen produced during the course of the reaction. Inhibition of photosystem II by 3‐(3,4dichlorophenyl)‐1,1‐dimethylurea and addition of a photosystem 1 electron donor did not lead to photoproduction of hydrogen or photoreduction of methyl viologen. Extensive photosystem I hydrogen evolution was obtained when thiols were also present. Platinum asbestos or palladium asbestos replaced hydrogenase in a system coupled to chloroplasts.
THERMAL GENERATION OF ELECTRONICALLY EXCITED STATES BY α‐PEROXYLACTONES: ACTIVATION PARAMETERS AND EXCITATION YIELDS AS A FUNCTION OF α‐DEUTERATION*
Authors: Adam Waldemar , Yany Faris
Published: January 2008

Abstract— The kinetics and the direct, the 9,10‐dibromo‐ (DBA) and the 9,10‐diphenylanthracene‐ (DPA) enhanced chemiluminescence of tert‐butyl α‐peroxylactone 1, with and without α‐deuteration, was investigated in order to probe the mechanism of direct chemiexcitation by these hyperenergetic molecules. The small secondary isotope effect on the rates and activation parameters suggests that a diradical mechanism is obtained. The partitioning of the diradical intermediate into excited vs ground state product and the yield of triplet excited product are moderately (ca. 5‐fold) increased by α‐deuteration, but the singlet yield is unaffected. A convenient and useful chemiluminescence method for the determination of fluorescence quantum yields has been developed.
REDUCED CYSTINE CONCENTRATION IN BLOOD PLASMA EXPOSED TO BROAD SPECTRUM LIGHT
Authors: Felten Richard P. , Sykes Stephen M. , Lamanna Anthony , Waxler Morris
Published: January 2008

Abstract— Heterozygote and homozygote Gunn rat blood plasma, as well as human blood plasma, was exposed for 24 h to broad‐spectrum fluorescent light (Dura‐Test Vita‐Lite). The result of this exposure was the reduction of half‐cystine concentrations in all exposed samples when compared to unexposed controls. The data suggests that the effect observed was not the result of direct photic energy absorption by cystine but was the result of a photic intermediate.
PHOTOREACTIVATION OF ULTRAVIOLET LIGHT‐INDUCED SISTER CHROMATID EXCHANGES IN POTOROUS CELLS
Authors: Ishizaki Kanji , Nikaido Osamu , Takebe Hiraku
Published: January 2008

Abstract— Exposure to visible light after UV‐irradiation showed a remarkable effect on UV‐induced sister chromatid exchanges (SCEs). After 6‐h exposure to visible light (3 × 105 J/m2), two‐thirds of the UV‐induced SCEs were prevented, confirming Kato's findings. Exposure to visible light before UV irradiation had no effect. This effect of visible light on UV‐induced SCEs was temperature dependent, suggesting the presence of enzymatic photoreactivation.
THE INACTIVATION OF A NATURAL POPULATION OF COLIFORM BACTERIA BY SUNLIGHT
Authors: Grigsby Perry , Calkins John
Published: January 2008

Abstract— The ‘natural purification’ of water, processes by which pathogenic organisms disappear from contaminated waters, is of great importance regarding water resources. The relative importance of the various processes which remove undesirable organisms is yet to be determined. Wastewater was exposed to sunlight by placing 120 m/samples in UV transparent or absorptive cylindrical vessels which were then placed in a 50/ container filled with water from a lagoon system, thus simulating actual exposure conditions in the lagoon system. Samples were exposed to natural sunlight for 3 days and received different wavelengths of sunlight, depending upon the presence of predetermined filters. The dynamics of the coliform population was observed. It was noted that coliform bacteria demonstrated a significant growth potential when held in darkness or during the night. An entire day of full unfiltered sunlight was a potent bacteriocidal agent, reducing coliform survival to less than 0.01% of the initial value. Removing the shorter wavelengths (Λ. < 325 nm) by optical filters or by the optical properties of the wastewater itself still left components of sunlight capable of killing coliforms. Our studies support the concept that solar UV radiation makes a substantial contribution to the natural purification of water.
SENSITIVITY TO PHOTOADDITION OF MONO‐AND BIFUNCTIONAL FUROCOUMARINS OF X‐RAY SENSITIVE MUTANTS OF SACCHAROMYCES CEREVISIAE
Authors: Henriques J. A. P. , Moustacchi E.
Published: January 2008

Abstract— With the exception of rad53, seven other X‐ray sensitive mutants of the rad50 serie of Saccharomyces cerevisiae were found to be more sensitive than the wild type to photoaddition of Afunctional (3‐methoxypsoralen) and monofunctional (3‐carbethoxypsoralen) furocoumarins. The magnitude of sensitivity to killing is dependent upon the locus and the phase of growth.

This means that in addition to the two repair pathways (excision‐resynthesis and mutagenic pathways) previously shown to be involved in repair of furocoumarins photo‐induced lesions, a third pathway is implicated in the repair of such lesions.
THE DEPENDENCE OF PHOTOSENSITIZING EFFICACY OF ACRIDINE ORANGE AND TOLUIDINE BLUE ON THE DEGREE OF SENSITIZER‐CELL INTERACTION
Authors: Ito Takashi
Published: January 2008

Abstract— Previous work of photosensitizing action in vivo has commonly been performed under the ‘steady’ conditions where the sensitizing dye is equilibrated with the cells by allowing ample time for the sensitizer‐cell interaction prior to light illumination. The present experiments, by combining a fast mixing technique (20 ms) with short illumination (mostly & < 10 s), intended to measure the change in the efficacy of the sensitizing action on yeast cells during a short period of time starting from the mixing of the two components, sensitizers and cells. We found that the efficacy of the sensitizing action of acridine orange (AO) began to increase within 20 s and continued to do so until at least 10 min. This was true both for the inactivation and the induction of genetic changes. Similar experiments with toluidine blue (TB), which is believed to be normally unpenetrable into the cell, showed no such fast change characterized by a time of less than 60 s, but unexpectedly revealed a small but significant increase in the efficacy after 20–30 min of mixing. This slow change may indicate that TB can penetrate slowly into the hydrophobic region in the membrane, and as a result, it exerts action with a higher efficiency than it remains in the outside medium. The increased induction of genetic changes beyond control level with the fast (& < 60s)TB sensitization in H2O and D2O medium is discussed in terms of the diffusiveness of 1O2 into the cell interior.
BILIRUBIN‐PHOTOSENSITIZED LYSIS OF RESEALED ERYTHROCYTE MEMBRANES*
Authors: Deziel Mark R. , Girotti Albert W.
Published: January 2008

Abstract— The ability of bilirubin to photosensitize biomembrane damage has been tested, using resealed human erythrocyte ghosts as a model system. Continuous irradiation of bilirubin‐charged ghosts with broad‐band blue light resulted in membrane lysis, as evidenced by the release of trapped markers such as Na+ or glucose‐6‐phosphate. Sodium dodecyl sulfate‐gel electrophoresis of membrane proteins revealed a progressive and relatively rapid loss of spectrin (bands 1 and 2) and band 4.1 during irradiation, accompanied by the appearance of cross‐linked polypeptides. The antioxidant butylated hydroxytoluene protected ghosts against lysis, but not against protein cross‐linking, suggesting that lipid peroxidation is the crucial membrane disrupting event.
CONCENTRATION QUENCHING OF FLUORESCENCE FROM CHLOROPHYLL‐a, PHEOPHYTIN‐a, PYROPHEOPHYTIN‐a AND THEIR COVALENTLY‐LINKED PAIRS*
Authors: Yuen M. J. , Shipman L. L. , Katz J. J. , Hindman J. C.
Published: January 2008

Abstract— We have systematically investigated the quenching of pigment fluorescence in pyridine solutions of Chlorophyll‐a, Pheophytin‐a, Pyropheophytin‐a, and their covalently‐linked pairs. In all cases, the fluorescence decay curves could be fit within experimental error to a single exponential. Intermolecular quenching constants were computed by fitting the measured decay rate constant vs concentration curves to a power series in the concentration of the various species. Analysis of the shapes of these quenching curves provided information about the operant quenching mechanisms. For Chlorophyll‐a and Pheophytin‐a, the observed decay kinetics are consistent with a quenching mechanism in which singlet excitation is transferred from fluorescent monomers to relatively non‐fluorescent dimers. For Pyropheophytin‐a, on the other hand, the decay kinetics are consistent with a mechanism involving the collision between an excited monomer and a ground state monomer. For all three covalently‐linked pairs, the decay kinetics are consistent with a mechanism in which singlet excitation is transferred from fluorescent ‘open’ forms to relatively non‐fluorescent ‘closed’ forms. Difference absorption spectroscopy was used to obtain direct evidence for the formation of ground state dimers at higher pigment concentrations. Equilibrium constants for dimer formation computed from the kinetic data and difference spectral data were in good agreement, 3.2 M‐1 and 1.4 M‐1, respectively.
USEFUL PHOTOLUMINESCENCE PROBES OF MICELLAR SYSTEMS—CYCLIC AZOALKANES AS FLUORESCENCE ACCEPTORS AND 1,5‐DIMETHYLNAPHTHALENE AS A FLUORESCENCE DONOR
Authors: Aikawa Masayuki , Yekta Ahmad , Liu Jonq‐Min , Turro Nicholas J.
Published: January 2008

Abstract— Certain cyclic azoalkanes are shown to exhibit substantial fluorescence intensity and attractive absorption parameters in detergent solutions. Quenching of the fluorescence of detergent solutions of 1,5‐dimethylnaphthalene by these bicyclic azoalkanes has been investigated and is found to provide a useful system to study properties of micellar systems.
PHOTODYNAMIC INACTIVATION OF YEAST CELLS SENSITIZED BY HEMATOPORPHYRIN
Authors: Stenstrøm A. G. Kvello , Moan J. , Brunborg G. , Eklund T.
Published: January 2008

Abstract— Yeast cells are inactivated by treatment with hematoporphyrin and light. The inactivation is mainly mediated by singlet oxygen. The quantum yield of singlet oxygen increases with increasing pH, while the efficiency of cellular inactivation decreases with increasing pH. Cells in the stationary phase are much more resistant to the treatment than cells in exponential growth. Membrane damage seems to be the main determining step in the photoinactivation.
REDUCTION BY NEAR‐ULTRAVIOLET (334 nm) LIGHT OF E. COLI CAPACITY FOR PHAGE GROWTH DEPENDS UPON THE rel GENE AND 4‐THIOURIDINE
Authors: Wingo Richard J. , Fossum Tore , Luo Solomon , Jagger John
Published: January 2008

Abstract— Near‐ultraviolet radiation (near UV; 300–380 nm) has long been known to produce a transient reduction of the capacity of bacteria to support phage growth. The present work shows that, at high fluenœs (40–100 kJ/m2), 85% of 334‐nm‐induced reduction of capacity in Escherichia coli B/r requires the rel gene; that is, it results from rel‐gene activity caused by the near‐UV treatment. This rel‐gene activity leads to (1) a bacterial growth delay and concomitantly lowered bacterial metabolism, and (2) a parallel delay in phage development, with a considerable depression of burst size. We propose that the observed effects on phage development are a consequence primarily of the lowered bacterial metabolism, but they may also result partly from a direct inhibition of phage DNA synthesis by the rel gene product, these effects together leading to the observed reduction of capacity in a rel+ strain. The remaining 15% of capacity reduction, observed in a rel strain, has an unknown mechanism, but does appear to involve a delay in phage development.

At least 95% of the total capacity reduction observed in the rel+ strain in the range 40–100 kJ/m2 requires the presence of 4‐thiouridine, an unusual base in E. coli transfer RNA, which is presumably both the chromophore and the target for near‐UV‐induced capacity reduction.
THE PRIMARY PROCESSES OF VISION: A VIEW FROM THE EXPERIMENTAL SIDE
Authors: Applebury M. L.
Published: January 2008

Abstract— Experimental observations from picosecond spectroscopy studies of the early photochemical events in vision are presented. The data are discussed for implications about the nature of the primary photochemical event, the temperature effect on the molar absorption coefficient of bathorhodopsin, and proton translocation in the dynamic events leading to the formation of bathorhodopsin.
RHODOPSIN‐PHOSPHOLIPID INTERACTION IN DETERGENT AND IN THE DISK
Authors: Ikai Atsushi , Tamura Eriko , Nishigai Masaaki
Published: January 2008

Abstract— Solubilization of cattle disk membrane in deoxycholate shifted the fluorescence emission maximum from 324 to 331 nm without changing the intensity. Tryptophyl residues are probably located at the hydrophobic interface between rhodopsin and phospholipid. Depletion of deoxycholate concentration from the solubilized disk by Sephacryl 200 column chromatography produced rhodopsin‐phospholipid complexes with different characteristics that are the intermediate stages of membrane formation from homogeneous molecular solution. Association of rhodopsin takes place in a two‐dimensional way even in the appreciably low content of phospholipid.

Sedimentation velocity studies showed that reassociation of lipid and rhodopsin occurs in 0.2% deoxycholate as well as in 0.05% sodium dodecylsulfate.

By using Sephacryl column we can now prepare, within 60 min, the rhodopsin‐lipid complex that can form large vesicles in response to the addition of MgCl2 without dialysis. This type of lipoprotein complex will be useful to the study of the mechanism of the two dimensional membrane formation.
RECONSTITUTION OF SQUID RHODOPSIN IN RHABDOMAL MEMBRANES
Authors: Seki Takaharu , Hara Reiko , Hara Tomiyuki
Published: January 2008

Abstract— Squid opsin which is capable of combining with 11‐cis or 9‐cis retinal to reconstitute photo‐pigment has been prepared by irradiation of rhabdomal membranes with orange light (> 530 nm) in the presence of 0.2 M hydroxylamine. When the irradiation is carried out either at concentrations of hydroxylamine higher than 0.2 M or with light of wavelength shorter than 530 nm, rhodopsin in the membranes is bleached quickly, but the ability of the resultant opsin to form rhodopsin is greatly reduced.

The optimum pH for rhodopsin regeneration in rhabdomal membranes was found to be between 6.5 and 8.5. The rate of regeneration of rhodopsin increases with raising temperature, and at about 20°C it is almost the same as that of isorhodopsin. Even after solubilization in digitonin solution, opsin still preserves the ability to reform rhodopsin.

All‐trans retinal can be incorporated into retinochrome‐bearing membranes, in which it is isomerized into 11‐cis isomer by the photoisomerase activity of retinochrome. Rhabdomal membranes retaining active opsin can take up 11‐cis retinal from retinochrome membranes so as to synthesize rhodopsin.
DISTRIBUTION OF ENZYMES INVOLVED IN NUCLEOTIDE METABOLISM IN THE DISK AND OTHER ROD MEMBRANES
Authors: Shichi Hitoshi , Somers Robert L.
Published: January 2008

Abstract— Intact disks and inverted disks were prepared from bovine retinal rods and the distribution in the disk membrane of such enzymes as guanyl cyclase, cyclic nucleotide phosphodiesterase, GTP binding protein (GTPase), 5'‐nucleotidase and rhodopsin kinase was investigated. Guanyl cyclase was not detected in the disk; the enzyme activity was high in a membranous fraction containing the cilium or axoneme and the rod outer segment plasma membrane. Cyclic nucleotide phosphodiesterase, GTP binding protein (GTPase) and rhodopsin kinase were associated on the external surface of disk in the presence of 2 mM Mg2+. The enzymes dissociated from the membrane when Mg2+ was depleted. Thus, magnesium ion seems to regulate the state of these enzymes in the outer segment. 5'‐Nucleotidase activity was low in intact disks but was significantly enhanced after inversion of the disk. The catalytic site of the enzyme, therefore, must be located on the internal (intradiscal) surface. Since the disks are known to be formed by invagination of the plasma membrane, 5'‐nucleotidase, by inference, would have its catalytic site exposed on the external surface of the plasma membrane. Preliminary experiments showed that the capability of light‐activated rhodopsin to activate cyclic nucleotide phosphodiesterase was inhibited by phosphorylation of the pigment. This supports the idea that rhodopsin kinase, cyclic nucleotide phosphodiesterase and GTPase exist as a functional complex on rod membranes.
THE ELECTRICAL RESPONSE OF CEPHALOPOD VISUAL CELL MEMBRANE FRAGMENTS
Authors: Takagi M.
Published: January 2008

Abstract— Microvilli membrane fragments of squid (Todarodes pacificus) visual cells were adsorbed onto an oil surface in an aqueous medium. An electrical conductance increase was observed on illuminating the adsorbed film, and photopotential responses were recorded in a salt free medium of pH below 6, or in a saline of pH over 6. These electrical photoresponses are discussed in relation to the late receptor potential of squid retina.
POLARIZED FLUORESCENCE OF 5‐METHYLCYTOSINE SPECIES IN SOLUTION AT ROOM TEMPERATURE
Authors: Anderson Bruce E. , Callis Patrik R.
Published: January 2008

Abstract—

Fluorescence yields (πf,'s) and polarizations (P) are measured for aqueous 5‐methylcytosine (˜ 0.1 mM) at 20°C as a function of pH over the range 2–14. Both properties change abruptly and in parallel at pH's corresponding to the known pKa values. Polarizations were also obtained for the 5‐methylcytosine cation, neutral and anion species in ethylene glycol water glass at ˜180K. The weak fluorescence of the neutral and cation species at 20°C was polarized almost as highly as at low temperature. When the fluorescence lifetimes are assumed to be correctly given by the product of calculated radiative lifetimes and quantum yields, the polarizations are found to be consistent with rotational diffusion rates ˜4 times faster than predicted from Stokes‐Einstein models for the neutral and anion species. The cation seemed to rotate about two times more slowly than the neutral and anion species. It was also shown that the properties of the three species are such that a plot of 1/P vs apparent πf in the pH range 2–11 is fortuitously linear.
THE ANAEROBIC PHOTOLYSIS OF TRYPTOPHAN CONTAINING PEPTIDES
Authors: Dillon James
Published: January 2008

Abstract—

The anaerobic photolysis of either Glycine‐l‐Tryptophan or Glycine‐l‐Tryptophan‐Glycine, leads to one major product. These analogous compounds are shown to be the result of deamination followed by cyclization to the 4‐position of indole. Structural proof is given, and the possible mechanisms involved in the reaction are discussed.
ULTRAVIOLET INACTIVATION OF THE MIDI VARIANT OF Qβ RNA: UV‐INDUCED ‘KINETIC BARRIERS’ TO REPLICATION AT TWO TEMPERATURES
Authors: O'Hara Patrick J. A. , Gordon Milton P.
Published: January 2008

Abstract—

MDV‐1 RNA is a small variant of bacteriophage Qβ, and is an active template in replication reactions catalyzed by Qβ replicase. The predominant lesion formed when MDV‐1 is irradiated with 254 nm light with a dose of 2500 Jm‐2 is uridine hydrate, which is chemically closely related to the major thymidine products formed in DNA by ionizing radiation. We have found that the replication of irradiated MDV‐1 RNA is inhibited at 37°C as well as 12°C. However, while replication appears to be blocked at the sites of photolesions at 12°C, Qβ replicase ‘pauses’ at the lesions before continuing elongation at 37°C. This effect is not caused by reversion of the photoproducts to parent material at the higher temperature. ‘Pauses’ (caused by ‘kinetic modulators’) during the synthesis of nucleic acids from unirradiated templates have been reported to occur in a number of systems and may play a role in the regulation of transcription and replication. Our results suggest that one consequence of radiation damage to nucleic acid bases may be the introduction of lesions which mimic such modulators, leading to aberrations in the regulation of nucleic acid synthesis.
HERPES SIMPLEX VIRUS PRODUCES LARGER PLAQUES WHEN ASSAYED ON ULTRAVIOLET IRRADIATED CV1 CELLS
Authors: Coohill Thomas P. , Babich Michael A. , Taylor William D. , Snipes Wallace
Published: January 2008

Abstract—

Plaque development for either untreated or UV treated irradiated Herpes simplex virus Type 1 is faster when assayed on UV irradiated CV1 cells. This Large Plaque Effect only occurs if a minimum delay of 12h between cell irradiation and viral inoculation is allowed. Shorter delays give plaques that are smaller than controls (unirradiated virus‐unirradiated cells). The effect is maximal for a 48‐h delay and remains unchanged for delays as long as 84h. The effect is greatest for cell exposures of 10J m‐2.