bluuebunny/crossref_metadata_2025_split huggingface dataset:
FORMATION OF PURINE PHOTOPRODUCTS IN A DEFINED HUMAN DNA SEQUENCE
Authors: GALLAGHER PATRICIA E. , DUKER NAHUM J. 
Published: January 2008

AbstractThe formation of DNA base damages by broad spectrum ultraviolet irradiation (250–400 nm) was investigated using a defined sequence of human DNA. The irradiated, 92 base pair, 3‐end of the human alphoid segment was incubated with an enzyme fraction purified from bacteriophage T4‐infected E. coli. As previously reported, analysis of reaction products by sequencing gels showed enzymic incision of purine‐containing photoproducts as well as pyrimidine cyclobutane photodimers. The purine‐incising activity does not require metal ions and was unaffected by β‐mercaptoethanol or dithiothreitol. The formation of the purine photoproducts is independent of buffer; these lesions are produced by irradiation of DNA in Tris, Hepes or phosphate buffers. They are produced at biologically significant wavelengths between 260 to 300 nm. Only low levels were detected above or below this range. The formation of purine photoproducts is dose dependent with similar yields at some specific loci to pyrimidine dimers. These results suggest that purine‐containing photoproducts could be of consequence in ultraviolet carcinogenesis.
EXPOSURE OF MICE TO UV‐B RADIATION SUPPRESSES DELAYED HYPERSENSITIVITY TO Candida albicans
Authors: DENKINS YVONNE , FIDLER ISAIAH J. , KRIPKE MARGARET L. 
Published: January 2008

AbstractGroups of mice were exposed to a single dose of UV radiation before or after immunization with Candida albicans. The delayed type hypersensitivity (DTH) response was markedly depressed in all UV‐irradiated groups. Exposure of mice to UV radiation before sensitization induced splenic suppressor cells that, upon transfer to normal recipients, impaired the induction of DTH to Candida. In contrast, exposure of mice to UV radiation after sensitization interfered with elicitation of the DTH response, but this suppression was not transferable. These studies demonstrate that immunity to Candida albicans in mice is impaired by exposure to UV radiation and that two separate mechanisms may be involved.
THE ENZYMOLOGY AND MOLECULAR BIOLOGY OF THE Ca2+‐ACTIVATED PHOTOPROTEIN, AEQUORIN
Authors: CORMIER MILTON J. , PRASHER DOUGLAS C. , LONGIARU MAT , MCCANN RICHARD O. 
Published: January 2008

Abstract— Aequorin is a bioluminescent protein, isolated from the hydromedusan Aequorea victoria. A recombinant cDNA plasmid (pAEQl) was shown to encode apoaequorin by detecting photoprotein activity in an extract of an E. coli strain containing pAEQl (Prasher et al., 1986, Biochem. Biophys. Res. Comm. 126, 1259–1268). The nucleotide sequence of the pAEQl insert has been determined and is shown to differ significantly from the aequorin cDNA (AQ440) isolated by Inouye et al. (1985, Proc. Natl. Acad. Sci. USA 82, 3154–3158). Comparisons of the coding regions of the two cDNAs show there are 52 nucleotide differences, 19 of which are responsible for 18 amino acid replacements. These differences explain the microheterogeneity observed at 17 positions during the sequencing of native apoaequorin.Five aequorin isotypes extracted from Aequorea tissue are observed on 2‐dimensional gels and the E. coli‐expressed apoaequorin is shown to co‐migrate with one of these isotypes. The multiple isotypes could be caused by the presence of a multi‐gene family since Southern blot analysis of Aequorea DNA suggests the presence of a minimum of four aequorin genes. Immunoblot analysis suggests that purified native aequorin is proteolytically cleaved during its purification from Aequorea. Comparison of the deduced cDNA translations and the protein sequence suggests the loss of seven residues from the amino terminal.Overexpression of the apoaequorin cDNA in E. coli now provides the means of obtaining gram quantities of a single isotype of the protein which can be converted to aequorin in the presence of coelenterate luciferin, oxygen and an appropriate thiol. Proper extraction procedures and a single chromatographic step provides apoaequorin which is >95% homogeneous.
ISOLATION and CHARACTERIZATION OF A SUBUNIT FORM OF THE B875 LIGHT‐HARVESTING COMPLEX FROM Rhodobacter capsulatus
Authors: Heller Barbara A. , Loach Paul A. 
Published: January 2008

AbstractA structural subunit (called B816) has been isolated from the B875 light‐harvesting complex of Rhodobacter capsulatus using a detergent‐mediated dissociation of chromatophores. Rb. capsulatus MW442 (B800–850− B875+ car+) chromatophores were extracted with benzene and titrated with octyl glucoside (OG) to shift the near‐infrared absorption maximum from 873 to 816 nm. Gel filtration chromatography was then used to separate B816 from reaction centers. B816 could be quantitatively shifted back to a B875‐like form (lemax= 875 nm) by decreasing the OG concentration. A similar B816 species could be isolated in low yield from wildtype (B800–850+ B875+ car+) cells but not from SB203E (B800–850− B875 + car−). In the latter case, the B816 subunit seemed too unstable to be isolated under equivalent conditions. The α: β polypeptide ratio, the CD spectrum, and the ability to reversibly dissociate B816 to free bacteriochlorophyll and α‐ and β‐polypeptides were found to be similar to those of the B820 subunit of Rs. rubrum previously reported by our laboratory.
SPECTRAL SENSITIZATION OF SnO2 THIN FILM ELECTRODE BY THE J‐AGGREGATE OF CYANINE DYES IN MONOLAYERS
Authors: Haraguchi Akira , Yonezawa Yoshiro , Hanawa Ryotaro 
Published: January 2008

Abstract—Arachidic acid monolayers containing 5,6,5′,6′‐dibenzo‐I,I‐diethyl‐2,2′‐cyanine chloride were prepared by the spreading method and deposited on the SnO2 surface using the Langmuir‐Blodgett technique. The SnO2 : dye assembly prepared in this manner was used as a photoelectrode of the conventional electrochemical cell. A distinct J‐band was observed in the action spectra of sensitized anodic and cathodic photocurrents. Effects of calcium arachidate barriers inserted between dye layer and either SnO2 electrode (inside barrier) or electrolyte solution (outside barrier) on the photocurrent were examined. Although the inside barrier was effective in decreasing both anodic and cathodic photocurrents, the outside barrier did not suppress cathodic photocurrent. The following mechanism involving a molecular exciton of the J‐aggregate is proposed for the sensitized photocurrent. The anodic photocurrent is caused by hole trapping by some reducing agent and concomitant injection of the electron from molecular exciton to the conduction band of SnO2. Extraction of conduction‐band electron of SnO2 by molecular exciton and supplying to some oxidizing agent such as dissolved oxygen are responsible for the cathodic photocurrent.
HYDROGEN BONDING AND PHOTOTAUTOMERISM OF 3‐METHYLLUMICHROME
Authors: Szafran Magdalena M. , Koziot Jacek , Heelis Paul F. 
Published: January 2008

Abstract—The spectral changes of 3‐methyllumichrome in 1,2‐dichloroethane upon addition of hex‐afluoroisopropanol, trifluoroacetic acid and acetic acid as hydrogen donor agents, have been defined. In the presence of 0.8Mhexafluoroisopropanol, the absorption and fluorescence emission spectra of 3‐methyllumichrome in 1,2‐dichloroethane acquire features nearly identical to those observed in aqueous solution. Therefore, hexafluoroisopropanol can be considered as a model compound for studies on hydrogen bonding of alloxazine derivatives in nonpolar media. The observed spectral changes upon addition of trifluoroacetic acid are caused mainly by protonation. The presence of hydrogen bonded and protonated forms of 3‐methyllumichrome has been checked by means of excitation spectra. The addition of acetic acid causes minor hydrogen bonding effects but gives rise to the phototautomery with an efficiency of one order of magnitude higher in 1,2‐dichloroethane than previously observed in methanol or dioxane. The isoalloxazinic emission band appears at about 495 nm and shifts bathochromically to 540 nm upon increasing acetic acid concentration, probably due to the opening of the primary cyclic structure between 3‐methyllumichrome and acetic acid. The fluorescence emission spectra can be resolved using lognormal approximation into three bands, one ascribed to the alloxazinic form (maximum at about 440 nm) and the others to isoalloxazinic species (maxima at about 495 and 540 nm). The excitation spectra confirm the presence of two excited alloxazinic forms, one solvated by 1,2‐dichloroethane with emission at 435 nm and T ˜1 ns, and the second bonded with acetic acid, bathochromically shifted with T ˜5 ns and able to phototautomerize. The sum of excitation spectra of both forms in suitable proportion reconstructs the absorption spectra of 3‐methyllumichrome in 1,2‐dichloroethane and acetic acid.
ULTRAVIOLET LIGHT INDUCES DOUBLE‐STRAND BREAKS IN DNA OF CULTURED HUMAN P3 CELLS AS MEASURED BY NEUTRAL FILTER ELUTION
Authors: Peak Jennifer G. , Peak Meyrick J. 
Published: January 2008

Abstract—Neutral filter elution at pH 7.2 and 9.6 was used to measure the induction of DNA lesions in human P3 teratocarcinoma cells by monochromatic 254‐, 270‐, 313‐, 334‐, 365‐, and 405‐nm radiation and by 60gamma rays. In this assay DNA double‐strand breaks (dsb) increase the rate of elution of DNA from cell lysates on a filter. Yields of dsb as measured by this procedure were determined by using a calibration of the assay that correlates elution parameters with number of dsb caused by disintegration of 125I incorporated into the DNA. Analysis of fluence responses obtained by using the calibrated assay indicated that the number of dsb induced per dalton of DNA as measured by this assay is proportional to the square of the fluence at all the energies of radiation studied, implying that the induction of these lesions may be a two‐hit event. Analysis of the relative efficiencies for the induction of dsb by ultraviolet radiation, corrected for quantum efficiency, revealed a spectrum that coincided closely with that for the induction of single‐strand breaks (ssb) in the same cells, having a close fit with the spectrum of nucleic acid in the UVC and UVB region below 313 nm, and a shoulder in the UVA region. It was calculated, however, that there may be too few ssb for dsb to result from randomly distributed closely opposed ssb.
CHARACTERIZATION OF RAD4 GENE REQUIRED FOR ULTRAVIOLET‐INDUCED EXCISION REPAIR OF Saccharomyces cerevisiae PROPAGATED IN Escherichia coli WITHOUT INACTIVATION
Authors: Choi In Soon , Kim Jae Bum , Lee Kee Nyung , Park Sang Dai 
Published: January 2008

Abstract—The previously isolated RAD4 gene designated as pPCl from the genomic library of Saccharomyces cerevisiae (Yoon et al., 1985, Korean J. Genetics 7, 97–104) appeared to propagate in Escherichia coli and yet retained its complementing activity to rad4 mutants without inactivation. The subcloned RAD4 gene was found to be localized within a 2.5 kb DNA fragment flanking Bg/II and Bam HI sites in the insert DNA, and was shown to have the same restriction map as a yeast chromosomal DNA, as determined by Southern hybridization. Tetrad analysis and pulse‐field chromosome mapping have revealed that the cloned RAD4 gene can be mapped and integrated into the yeast chromosome V, the actual site of this gene. DNA‐tRNA hybridization has shown that the isolated RAD4 gene did not contain a suppressor tRNA gene. These results have indicated that the pPCl is a functional RAD4 gene playing a unique role involved in the nucleotide excision repair of yeast without any genetic change during amplification in E. coli.
A STUDY OF THE PHOTODYNAMIC EFFICIENCIES OF SOME EYE LENS CONSTITUENTS
Authors: Krishna C. Murali , Uppuluri Shobha , Riesz Peter , JR J. Samuel Zigler , Balasubramanian D. 
Published: January 2008

AbstractWe have studied the photochemical quantum yields of singlet oxygen production (using the RNO bleaching method) and superoxide production (using the EPR‐spin trapping method and the SOD‐inhibitable ferricytochrome c reduction spectral assay) of kynurenine (Ky), N‐formylkynurenine (NFK), 3‐hydroxykynurenine (3HK), kynurenic acid (KUA), and the flavins, riboflavin (RF) and flavin mononucleotide (FMN). Such a study of the photodynamic efficiencies is important since these compounds appear endogenously in the eye. The singlet oxygen quantum yields of the flavins and KUA are high, while Ky and 3HK generate no detectable amounts of singlet oxygen. The superoxide quantum yields of the sensitizers are low compared to their singlet oxygen, and Ky and 3HK produce no detectable amounts of superoxide. The production of the superoxide radical is enhanced in the presence of electron donor molecules such as EDTA and NADH. These results suggest that the production of oxyradicals in the lens may be modulated by the presence of endogenous electron donor molecules such as the coenzymes NADH and NADPH, which are present in significant amounts in some lenses. They also suggest that Ky and 3HK, which are known to be present in aged lenses, might play a protective rather than a deleterious role in the eye.
SITES and EFFICACY OF PHOTODAMAGE BY TIN ETIOPURPURIN in vitro USING DIFFERENT DELIVERY SYSTEMS
Authors: Kessel David , Morgan Alan , Garbo G. M. 
Published: January 2008

AbstractPhotosensitization by tin etiopurpurin (SnET2) was determined in cell culture using sensitizer dissolved in ethanol or solubilized via three different delivery systems: Cremophor EL, γ‐cyclodextrin or Molecusol (a more water‐soluble cyclodextrin derivative). Sensitizer uptake was substantially more efficient when the delivery systems were employed, in terms of intracellular level needed to lethally photosensitize cells. We observed photodamage at both membrane and mitochondrial loci, but the former was better correlated with loss of viability.
TIME‐RESOLVED FLUORESCENCE OF NITROBENZOXADIAZOLE‐AMINOHEXANOIC ACID: EFFECT OF INTERMOLECULAR HYDROGEN‐BONDING ON NON‐RADIATIVE DECAY
Authors: Lin Su , Struve Walter S. 
Published: January 2008

AbstractThe fluorescence kinetics of the nitrobenzoxadiazole (NBD) chromophore were studied at low concentrations in solvents with varying polarity and hydrogen‐bonding donor strength. The emission decay was essentially single exponential in all solvents studied. While the absorption and fluorescence solvatochromism is determined largely by the solvent polarity, the S, state decay kinetics are strongly modulated by the solvent H‐bonding capacity. The NBD emission lifetime, generally –7–10ns in the aprotic solvents, is reduced to 0.933 ns in water. The solvent deuterium isotope effect on the fluorescence decay is substantial in D20 and in methanol‐d4, but is insignificant in DMSO‐d6. These results are consistent with acceleration of S1S11 internal conversion through an accepting vibrational mode created by intermolecular hydrogen‐bonding of the NBD chromophore to an H atom‐donating solvent. This work bears on the practicality of using NBD as a fluorophore in assays for estrogen and progesterone receptors.
THE SHAPE OF FLUENCE‐RESPONSE CURVES FOR THE LIGHT‐INDUCED TRANSCRIPT ACCUMULATION IN PEA SEEDLINGS
Authors: Yoshida Kazuichi , Takimoto Atsushi , Sasaki Yukiko 
Published: January 2008

AbstractThe fluence‐response curves for the transcript accumulation of four light‐regulated genes were investigated at various times after exposure to 5‐min red light ranging from a very low fluence (1.6 × 10−3μmol m−2) to low fluence (3.0 × 103μmol m−2). The fluence‐response curves were monophasic 6 or 12 h after exposure, although they were biphasic 48 h after exposure, as reported elsewhere. The curves determined 18 or 24 h after red light exposure showed a monophasic or slightly biphasic character. That is, the shape of the fluence‐response curves changed from monophasic to biphasic with an increase in the time of darkness after the treatment with 5 min red light.
PHOTOOXYGENOLYSIS OF VITAMIN B12 and RELATED CORRINS: COBALT(III)CORRINS AS SUBSTRATES and QUENCHERS FOR SINGLET OXYGEN (1Δg)*
Authors: Kraeutler Bernhard , Stepanek Rene 
Published: January 2008

AbstractUnder photooxygenolytic conditions, vitamin B12 can be degraded to two isomeric dioxosec‐ocorrins by a regioselective oxygenolytic cleavage of the corrin macrocycle (preliminary report in Krautler and Stepanek (1985), Angew. Chem.97,71–73; Angew. Chem. Intl. Ed. Engl.24,62–64): irradiation of an oxygen saturated solution of vitamin B12 (1), of KCN and of methylene blue (molar ratio (1:1:0.005) in CD3OD at ca 200 K with visible light led to a selective oxygenolysis of the vitamin. The two products, potassium CoαCoβ‐dicyano‐5,6‐dioxo‐5,6‐seco‐5′6′‐dimethylbenzimidazolyl‐cobam‐idate (3, 10% yield) and potassium CoαCoβ‐dicyano‐14,15‐dioxo‐14,15‐seco‐5′6′‐dimetliylbenzirnida‐zolyl‐cobamidate (4, 25% yield), and 1 (31% yield) were chromatographically separated and isolated. The structures were established spectroanalytically, and by the help of an acid catalyzed methanolysis of 3 and 4 to the related CoαCoβ ‐dicyano‐heptamethyl‐ dioxosecocobyrinates (6 and 7).When irradiated with visible light in any oxygen saturated methanolic solution containing methylene blue, vitamin B12 itself exhibited considerable inertness. Only upon addition of a stoichiometric amount of KCN to such a solution (to afford the adduct 2) did the photolysis lead to oxygenation of the cobaltcorrin within a useful time. The regioselectivity of the oxygenolysis of 2 and the ratio of products formed are comparable to the outcome of the photooxygenolysis of the structurally related heptamethylcobyrinate 5 (Kräutler (1982) Helv. Chim. Acta65,1941–1948). The reaction at the methyl‐substituted meso‐positions of the corrin macrocycle is indicated to involve singlet oxygen (1Δg). In support of this interpretation, the preparative photolysis of 2 at 200 K also turned out to be about 7 times slower when CH3OH was used instead of CD3OD.
CHOLESTEROL CONTENT BUT NOT PLASMA MEMBRANE FLUIDITY INFLUENCES THE SUSCEPTIBILITY OF L1210 LEUKEMIA CELLS TO MEROCYANINE 540‐SENSITIZED IRRADIATION
Authors: Gaffney David K. , Feix Jim B. , Schwarz Hans P. , Struve Mark F. , Sieber Fritz 
Published: January 2008

AbstractThis paper examines the relationship between lipid composition, plasma membrane fluidity, expression of dye binding sites, and susceptibility to merocyanine 540 (MC540)‐sensitized irradiation in L1210 leukemia cells. Reducing the cells' cholesterol content by exchange diffusion with phosphatidylcholine liposomes or by inhibiting its biosynthesis with 25‐hydroxycholesterol enhanced plasma membrane fluidity, the expression of dye binding sites, and the cells' susceptibility to MC540‐sensitized irradiation. Conversely, if the cholesterol content was enhanced by exchange diffusion with cholesterol:phosphatidylcholine liposomes, the cells' susceptibility to MC540‐sensitized irradiation was decreased. However, contrary to expectations, dye‐binding was slightly enhanced and plasma membrane fluidity remained unchanged. Growing the cells in fatty acid‐supplemented medium had profound effects on their lipid composition. Cells enriched in polyunsaturated fatty acids had more fluid plasma membranes. However, dye‐binding was not significantly affected and photosensitivity was slightly reduced. These results suggest that cholesterol is one, but probably not the only, determinant of the expression of cellular dye binding sites and, consequently, the cell's susceptibility to MC540‐sensitized irradiation. By contrast, plasma membrane fluidity does not appear to play a major role in the regulation of dye‐binding site expression.
STRUCTURE and CONFORMATION OF PHOTOSYNTHETIC PIGMENTS and RELATED COMPOUNDS. 2. NICKEL (II) METHYL PYROPHEOPHORBIDE a–A SEVERELY ISTORTED CHLOROPHYLL DERIVATIVE*
Authors: Senge Mathias O. , Smith Kevin M. 
Published: January 2008

AbstractThe crystal structure of Ni(II) methyl pryopheophorbide a (3) (CMH34N4Ni03, Mu= 605.4) was determined by x‐ray diffraction methods in order to determine the influence of the nickel‐ion on the ring conformation. The crystals were blue octahedrons and crystallized in the tetragonal space group P4121,2 with a= 14.727(4) Å, c = 26.666(12) Å, V= 5781(3) Å3Z= 8, D= 1.391 mg/m3. (Mo Kα) = 0.71069 Åμ= 0.713 mm−1, F(000) = 2544, 130 K. The final R value was 0.064 for 4096 observed reflections, wR = 0.065. The molecule is severely distorted and shows a saddle‐shaped ring conformation, the β‐pyrrole atoms being displaced up to 0.6 A out of the plane of the nitrogens. The severe deformation restricts the use of Ni‐derivatives in spectroscopic model studies on chlorophylls and provides an example for the conformational flexibility of the phorbin macrocycle.
ACTION SPECTRA OF THE ANTILEUKEMIC and ANTIVIRAL ACTIVITIES OF MEROCYANINE 540
Authors: O'Brien J. M. , Singh R. J. , Feix J. B. , Kalyanaraman B. , Sieber F. 
Published: January 2008

AbstractAction spectra of the antileukemic and antiviral activities of merocyanine 540 (MC540) were determined using L1210 leukemia cells and human Herpes simplex virus type 1. The major peak of both action spectra aligned closely with the absorption spectrum of membrane‐bound dye monomer, and by implication, the action spectrum of 1O2 generation. These results are compatible with the notion that the antileukemic and antiviral activities of MC540 are primarily attributable to membrane‐bound monomer and at least in part mediated by 1O2.
PHOTOCHEMISTRY OF QUINOLYLMETHYLISOTHIORONIUM SALTS. GUANINE SELECTIVE DNA PHOTOCLEAVAGE REAGENTS
Authors: HENRIKSEN U. , LARSEN C. , KARUP G. , JEPPESEN C. , NIELSEN P. E. , BUCHARDT O. 
Published: January 2008

Abstract—Quinolylmethylisothioronium salts (1a and 4a) cleave DNA upon irradiation. The cleavage is more than 10‐fold enhanced by piperidine treatment and subsequently shows a high preference for guanines. Photolysis of 1a, 2a and 4a in water at Λ > 300 nm resulted in photoheterolysis. Irradiation of 1a in 2‐propanol gave only products from photohomolysis, whereas irradiation of 1a in methanol and 2a and 4a in 2‐propanol resulted in products from both photoheterolysis and photohomolysis. Quantum yields for the disappearance of 1a in water and 2‐propanol were determined. The presence or absence of oxygen had no effect in water, whereas oxidation products were observed upon irradiation in methanol and 2‐propanol in the presence of oxygen. The guanine specific DNA photoreaction is proposed to take place by alkylation at N7 via the quinolylmethyl carbocation and thus to represent a photoalkylation.
THE PROTECTIVE FUNCTION OF THE EPIDERMAL LAYER OF RYE SEEDLINGS AGAINST ULTRAVIOLET‐B RADIATION
Authors: TEVINI M. , BRAUN J. , FIESER G. 
Published: January 2008

Abstract—Ultraviolet‐B radiation induces the accumulation of UV‐absorbing pigments of the flavonoid type in the epidermal layer of rye seedlings. The content of pigments identified as isovitexin derivatives was about 4 times higher in leaves preirradiated for up to 24 h with long wavelength UV‐B radiation as compared to control plants without any UV‐B pretreatment. Leaves preconditioned in this way could prevent or reduce damage to photosynthetic function caused by short wavelength UV‐B radiation. Photosynthetic activity monitored by variable fluorescence was reduced in unprotected leaves compared to protected leaves when expressed as a fluorescence decrease ratio value, as quantum yield of photosystem II (Fvm/Fm) or as leaf vitality index (Fm/Fo).