bluuebunny/crossref_metadata_2025_split huggingface dataset:
PHOTOLESIONS AND BIOLOGICAL INACTIVATION OF PLASMID DNA ON 254 nm IRRADIATION AND COMPARISON WITH 193 nm LASER IRRADIATION
Authors: Gurzadyan Gagik G. , Gorner Helmut , Schulte‐Frohlinde Dietrich 
Published: January 2008

AbstractPlasmid pTZ18R and calf thymus DNA in aerated neutral aqueous solution were irradiated by continuous 254 nm light. The quantum yields are φssb= 4.0 × 10‐5and φdsb= 1.4 × 10‐6for single‐ and double‐strand break formation, respectively, φbr= 2.3 × 10‐5for base release, φdn=2.1 × 10‐3for destruction of nucleotides, and φicl×φlds× 1 × 10‐6for interstrand cross‐links and locally denatured sites, respectively. The presence of Tris‐HCI/ ethylenediaminetetraacetic acid (10:1, pH 7.5) buffer strongly reduces φssb, The corresponding φ values, obtained on employing pulsed 193 nm laser irradiation, are much larger than those using λirr, = 254 nm. This is ascribed to a contribution of chemical reactions induced by photoionization, which is absent for 254 nm irradiation. The quantum yields of inactivation of plasmid DNA (λirr= 254 nm) were measured by transformation of theEscherichia colistrains AB1157 (wild type), φina(1157) = 1.6 × 10‐4, AB1886 (uvr‐), φina(1886) = 4.2 × 10‐4, AB2463 (rec‐), φina(2463) = 4.1 × 10‐4and AB2480 (uvr‐rec‐), φina(2480) = 3.1 × 10‐3. The quantum yields of inactivation of plasmid DNA are compared with those of the fourE. colistrains (denoted as chromosomal DNA inactivation) obtained from the literature. The results forE. colistrain AB2480 show that the chromosomal DNA and the plasmid DNA are both inactivated by a single pyrimidine photodimer per genome. With theE. colistrain AB2463 inactivation of plasmid and chromosomal DNA is the same for the same total damage per genome and is ∼ 10 times smaller than for AB2480. This is explained by photodimer repair in chromosomal and plasmid DNA and by the absence of dsb repair in both cases. In the repair wild‐type strain AB1157, inactivation of the plasmid DNA is roughly 100 times higher than that of the chromosomal DNA. We postulate that a portion of this difference is due to repair of dsb by the recA system in chromosomal DNA and that such repair does not take place in the plasmid DNA. The biological results from 254 nm irradiation are compared with those from 193 nm laser irradiation.
A PULSED LASER AND PULSE RADIOLYSIS STUDY OF AMPHIPHILIC CHLOROPHYLL DERIVATIVES WITH PDT ACTIVITY TOWARD MALIGNANT MELANOMA
Authors: Fiedor L. , Gorman A. A. , Hamblett I. , Rosenbach‐Belkin V. , Salomon Y. , Scherz A. , Tregub I. 
Published: January 2008

AbstractTwo amphiphilic derivatives of chlorophyll, which have high potential as photodynamic therapy sensitizers for malignant melanoma have been investigated by a combination of laser flash photolysis and pulse radiolysis. It is shown that direct excitation of monomeric forms of these molecules in both hydrophilic and hydrophobic environments produces significant yields of the corresponding triplet states, which have been characterized in terms of spectral and kinetic parameters. In both environments, scavenging of the triplets by oxygen produces singlet oxygen, O2(lΔ8), with essentially unit efficiency as evidenced by time‐resolved IR luminescence measurements.
FLAVIN‐PHOTOSENSITIZED MONOMERIZATION OF DIMETHYLTHYMINE CYCLOBUTANE DIMER IN THE PRESENCE OF MAGNESIUM PERCHLORATE
Authors: Miyake Kunihito , Masaki Yasuhiro , Miyamoto Ikuya , Yanagida Shozo , Ohno Takeshi , Yoshimura Akio , Pac Chyongjin 
Published: January 2008

AbstractWe have investigated the photosensitized monomerization of the cis,syn‐cyclobutane dimer of 1,3‐di‐methylthymine using riboflavin tetraacetate and a 5‐deazaflavin derivative as photosensitizer. Although little monomerization of the dimer is induced by photoexcitation of the flavins in the absence of any additives, the flavins can function as an efficient photosensitizer in the presence of magnesium perchlorate. Mechanistic studies involving spectroscopic, quantum‐yield and flash‐photolysis measurements demonstrated that the photosensitized monomerization exclusively proceeds through electron transfer from the dimer to the triplet flavins complexed with Mg2+. The effects of magnesium perchlorate are compared with those on the chloranil‐photosensitized monomerization and also with the effects of HClO4 on the flavin‐photosensitized reaction.
TWO DIFFERENT TYPES OF PHOTOCHEMISTRY IN PHYCOERYTHROCYANIN α‐SUBUNIT*
Authors: Hong Qiang , Zhao Kai‐Hong , Scheer Hugo 
Published: January 2008

AbstractThe photochemical activities of phycoerythrocyanin α‐subunits fromMastigocladus laminosusseparated by isoelectric focusing were tested by irradiating at 500, 550, 577 and 600 nm. Two types of photoreversible photochromic responses have been characterized by absorption and absorption difference spectroscopy. Type I is the well‐known absorption shift from 571 to 506 nm. Type II is a new response characterized by a line‐broadening of the 570 nm absorption.
NUCLEAR FACTOR κB BINDING ACTIVITY IN MOUSE L1210 CELLS FOLLOWING PHOTOFRIN II‐MEDIATED PHOTOSENSITIZATION
Authors: Ryter Stefan W. , Gomer Charles J. 
Published: January 2008

AbstractClinical photodynamic therapy (PDT) uses the photosensitizer photofnn II to produce singlet molecular oxygen and other reactive oxygen intermediates for localized tumor tissue cytotoxicity. In this report, we show that PDT enhances the DNA binding activity of nuclear factor kappa B (NFkB), a transacti vator of cytokine gene expression. Photosensitization following a 16 h incubation of photofrin II induced NFkB binding activity in mouse leukemia L1210 cells 10‐fold above that observed in exponentially growing cultures. Serum starvation, as well as drug‐alone and light‐alone controls, elevated basal NFkB binding activity two‐ to three‐fold. Upstream stimulatory factor binding activity was not modulated by any of the cell treatments and was used to standardize gel mobility shift data. This study identifies porphynn‐mediated PDT as an inducer of NFkB binding activity, extending recent findings that NFkB activation is a general response to oxidative stress.
LIGHT‐MEDIATED CYCLIZATION OF (E)‐3‐(5‐[6‐HYDROXY‐7‐METHOXY] BENZOFURANYL)PROPENOIC ACID, A WATER‐SOLUBLE PRECURSOR OF 8‐METHOXYPSORALEN
Authors: Mohammad Taj , Morrison Harry 
Published: January 2008

AbstractThe title compound is a stable, water‐soluble “pro‐drug” for 8‐methoxypsoralen, which converts to psoralen upon photolysis with UVA light. The process involves the photolytic formation of acisisomer that lactonizes in a dark reaction.
HOMOLOGY AT THE AMINO ACID LEVEL BETWEEN PLANT PHYTOCHROMES AND A REGULATOR OF ASEXUAL SPORULATION IN Emericella (=Aspergillus) nidulans
Authors: Grifith Gareth W. , Jenkins Gareth I. , Milner‐White E. James , Clutterbuck A. John 
Published: January 2008

Abstract–Protein sequence comparison between the N‐terminal regions of the BRLA (bristle A) protein of the ascomycete fungus Aspergillus nidulans and a number of plant phytochromes has demonstrated a moderate level of sequence similarity. The region of similarity corresponds to the phytochrome domains believed to be responsible for photoreception and which undergo light‐induced conformational changes, although a putative chromophore‐binding site is not evident. Over 22% of residues are conserved and 24% conservatively substituted between residues 1 and 272 of BRLA and the N‐terminal domains of Type 1 phytochromes from dicotyledonous species. A lower level of similarity, but over the same region, is observed in comparison with a wider range of phytochromes. Given the known role of BRLA as a transcriptional activator involved in conidiation, and the red/far‐red reversible photoregulation of this developmental process, the similarity with phytochromes may be significant.
ADVENTITIOUS INTERCONVERSION OF cis‐ AND trans‐UROCANIC ACID BY LABORATORY LIGHT
Authors: Hug Daniel H. , Hunter John K. 
Published: January 2008

AbstractUrocanic acid (UCA) is a chromophore in the stratum corneum. Ultraviolet radiation (ultraviolet B) has been shown to suppress mammalian cell‐mediated immunity. The photoisomerization of trans‐UCA to cis‐UCA was proposed as the initiator of the suppression process. Cis‐urocanic acid has been demonstrated to suppress immunity by a variety of experiments. Investigators should be aware that laboratory illumination may be capable of interconverting trans‐UCA and cis‐UCA during experimental manipulations. This possible inadvertent contamination of one isomer by the other may influence results. We demonstrated that fluorescent lamps, daylight, sunlight and incandescent lamps were able to bring about isomerization. Window glass and container materials of plastic and clear glass did not filter out effective wavelengths, but three commercial plastic diffusers on fluorescent fixtures prevented the isomerization. Because the molar extinction coefficient (ɛ) for cis‐UCA is less than that of trans‐UCA, we have exposed 0.1 mMtrans‐UCA to ambient light and monitored the change in absorbance. A method is given to calculate the percentage of trans and cis isomers from the absorbance at 277 nm when the initial purity and absorbance are known. Using this procedure, we validated the molar extinction coefficient of cis‐UCA.
THE ORIGIN OF THE RED‐SHIFTED ABSORPTION MAXIMUM OF THE M412 INTERMEDIATE IN THE BACTERIORHODOPSIN PHOTOCYCLE
Authors: Gat Y. , Sheves M. 
Published: January 2008

AbstractThe factors that red shift the absorption maximum of the retinal Schiff base chromophore in the M412 intermediate of bacteriorhodopsin photocycle relative to absorption in solution were investigated using a series of artificial pigments and studies of model compounds in solution. The artificial pigments derived from retinal analogs that perturb chromophore‐protein interactions in the vicinity of the ring moiety indicate that a considerable part of the red shift may originate from interactions in the vicinity of the Schiff base linkage. Studies with model compounds revealed that hydrogen bonding to the Schiff base moiety can significantly red shift the absorption maximum. Furthermore, it was demonstrated that although s‐trans ring‐chain planarity prevails in the M412 intermediate it does not contribute significantly (only ca 750 cm−1) to the opsin shift observed in M412. It is suggested that in M412, the Schiff base linkage is hydrogen bonded to bound water and/or protein residues inducing a considerable red shift in the absorption maximum of the retinal chromophore.
ASCORBIC ACID GLYCATION OF LENS PROTEINS PRODUCES UVA SENSITIZERS SIMILAR TO THOSE IN HUMAN LENS
Authors: Ortwerth B. J. , Linetsky Mikhail , Olesen Paul R. 
Published: January 2008

Abstract—‐Soluble calf lens proteins were extensively glycated during a 4 week incubation with ascorbic acid in the presence of oxygen. Amino acid analysis of the dialyzed proteins removed at weekly intervals showed an increasing loss of lysine, arginine and histidine, consistent with the extensive protein cross‐linking observed. Irradiation of the dialyzed samples with UVA light (1.0 kJ/cm2 total illumination through a 338 nm cutoff filter) caused an increasing loss of tryptophan, an additional loss of histidine and the production of micromolar concentrations of hydrogen peroxide. No alteration in amino acid content and no photolytic effects were seen in proteins incubated without ascorbic acid or in proteins incubated with glucose for 4 weeks. The rate of hydrogen peroxide formation was linear with each glycated sample with a maximum production of 25 nmol/mg protein illuminated. The possibility that the sensitizer activity was due to an ascorbate‐induced oxidation of tryptophan was eliminated by the presence of a heavy metal ion chelator during the incubation and by showing equivalent effects with ascorbate‐incubated ribonuclease A, which is devoid of tryptophan. The ascorbate‐incubated samples displayed increasing absorbance at wavelengths above 300 nm and increasing fluorescence (340/430) as glycation proceeded. The spectra of the 4 week glycated proteins were identical to those obtained with a solubilized water‐insoluble fraction from human lens, which is known to have UVA sensitizer activity.The incubation of lens proteins with dehydroascorbic acid or l‐threose, but not fructose, produced equivalent glycation, protein crosslinking and sensitizer activity. The relative sensitizer activity of the 4 week glycated sample was quantitatively very similar to that of a water‐insoluble fraction from aged human lenses. These data are consistent with the hypothesis that the protein‐bound brunescence in the lens may be advanced glycation endproducts, which are formed in large part by the oxidation products of ascorbic acid, and that these compounds may contribute significantly to the UVA sensitizer activity present in aged human lenses.
NEAR‐INFRARED‐FT‐RAMAN STUDY OF AGGREGATION OF BACTERIOCHLOROPHYLL c IN WHOLE LIVING Chlorobium limicola
Authors: Sato Hidetoshi , Uehara Kaku , Ishii Takasada , Ozaki Yukihiro 
Published: January 2008

Abstract—Near‐infrared excited Fourier‐transform Raman spectra have been measured for whole living Chlorobium limicola f. thiosulfatophilum to explore in situ structure of bacteriochlorophyll c (BChl‐c). The spectra, whose Raman bands are preresonance enhanced via a Qy band of BChl‐c, did not contain contributions from the major components of bacteria such as proteins and lipids. Therefore, the spectra provide selective structural information about BChl‐c in the chlorosomes in a totally nondestructive manner. A marker band, appearing at 1605 cm‐1 for the coordination number of the Mg atom, shows that BChl‐c in the chlorosomes is five coordinate. The Raman spectrum of living bacteria closely resembles that of BChl‐c in water‐saturated carbon tetrachloride (w‐std CC14) where it is comprised of dimer, tetramer and polymer spectra. However, a band assigned to a C=O stretching mode of the 131‐keto group is identified only at 1641 cm‐1. A band arising from the free keto carbonyl group, which appears in the spectrum of BChl‐c in w‐std CC14, is not observed in the spectra of bacteria. These observations suggest that BChl‐c in the chlorosomes forms mostly coordinate polymeric species whose structure is very similar to that of BChl‐c in w‐std CC14.
CHEMILUMINESCENT DIPHENYLACETALDEHYDE OXIDATION BY MITOCHONDRIA IS PROMOTED BY CYTOCHROMES and LEADS TO OXIDATIVE INJURY OF THE ORGANELLE
Authors: Nantes Isbli L. , Cilento Giuseppe , Bechara Etelvino J. H. , Vercesi Aníbal E. 
Published: January 2008

Abstract—Plant and animal mitochondria promote the aerobic oxidation of diphenylacetaldehyde (DPAA). This process is accompanied by chemiluminescence and rotenone‐insensitive oxygen uptake. Tn rat liver and potato tubers, mitochondrial swelling is concurrently detected. Light emission and oxygen consumption decreased (about 50%) in cytochrome c‐depleted mitochondria. A model system–cytochrome c or b5/dihexadecylphosphate liposomes–was also able to oxidize DPAA with parallel reduction of the cytochrome. Reduction of respiratory complex I or I plus II by addition of rotenone or antimycin A, respectively, did not prevent DPAA oxidation. However, when all cytochrome was reduced by addition of cyanide, aldehyde oxidation was completely suppressed. Altogether these data indicate that respiratory cytochromes are responsible for DPAA oxidation with production of excited species and consequent mitochondrial permeabilization.
SUBCELLULAR DISTRIBUTION OF HYPERICIN IN HUMAN CANCER CELLS
Authors: Miskovsky Pavol , Sureau Franck , Chinsky Laurent , Turpin Pierre‐Yves 
Published: January 2008

Abstract—Confocal laser microspectrofluorometric measurements on human T47D mammary tumor cells have been performed to assess the intracellular distribution of hypericin within the various cell compartments: cytoplasmic membrane, cytoplasm and nucleus. Confocal fluorescence measurements obtained from microvolumes (˜ 1 μm3) located within the three sites of interest show that, while being primarily located in the cell membrane and cytoplasm after a short‐term incubation in a 10−6M hypericin‐containing culture medium, hypericin actually reaches the inside of the cell nucleus after a long‐term incubation (210 min). Moreover, owing to the relative fluorescence quantum yields of hypericin determined in vitro when the molecule interacts with DNA, membrane and protein model systems, it is assumed that there is a significant accumulation of the drug into the cell nucleus. Consequently, the nucleus has to be considered as a possible target for the toxic action of hypericin.
EPR PERSISTENCE MEASUREMENTS OF UV‐INDUCED MELANIN FREE RADICALS IN WHOLE SKIN
Authors: Collins Bernard , Poehler Theodore O. , Bryden Wayne A. 
Published: January 2008

Abstract—Electron paramagnetic resonance is used to detect the formation of free radicals caused by exposure to ultraviolet radiation in chemically untreated rabbit skin. A fast jump in EPR signal level, occurring over a few seconds, is observed immediately after a skin sample is exposed to UV. This is followed by a slower increase toward an elevated steady‐state signal over a period of hours as the skin is continuously exposed to a UV light source. Upon cessation of UV light exposure, EPR signal levels undergo an abrupt drop followed by a slower decay toward natural levels. Elevated free radical concentrations following UV exposure are found to persist for several hours in whole skin. These results are consistent with time‐resolved EPR measurements of photoinduced radicals in various natural melanins.
PHOTOINDUCED TRANSIENT PHENOMENA IN CYCLODEXTRIN SOLID COMPLEXES: PHOTOCHEMISTRY OF AROMATIC KETONES
Authors: Barra Mónica , Scaiano J. C. 
Published: January 2008

Abstract—The photochemistry of benzophenone (BP) in cyclodextrin (α‐, ß‐ and γ‐CD) solid complexes has been examined by time‐resolved diffuse reflectance laser‐flash photolysis techniques. Benzophenone is photoreduced as a consequence of hydrogen abstraction from the CD cavity. Both BP phosphorescence and diphenylketyl radical fluorescence spectra in CD solid complexes were recorded at room temperature. Lifetime distribution analysis is used in order to describe the dynamics of triplet decay. The most probable BP triplet lifetime is found to decrease as the size of the CD cavity decreases (α‐CD = 0.3 (µs, ß‐CD = 0.5 µs and γ‐CD = 1.2 (µs). This observation contrasts with that for xanthone, a more rigid, yet structurally related ketone (α‐CD = 8 µs, ß‐CD = 3 µ.s and γ‐CD = 0.6 (µs) studied previously. The differences are interpreted in terms of changes in triplet reactivity and of restrictions on molecular mobility.
THE GENERATION OF HYDROGEN PEROXIDE BY THE UVA IRRADIATION OF HUMAN LENS PROTEINS
Authors: Linetsky Mikhail , Ortwerth B. J. 
Published: January 2008

Abstract—The water‐insoluble proteins from aged human lens are known to contain protein‐bound chromophores that act as UVA sensitizers. The irradiation of a sonication‐solubilized, water‐insoluble fraction from human lenses (55–75 years) with UVA light (1.5 kj/cm2, λ > 338 nm) caused an oxygen‐dependent photolysis of tryptophan, not seen when either α‐crystallin or lysozyme were irradiated. The suggested requirement for active oxygen species was consistent with a linear increase in hydrogen peroxide formation, which was also observed. A final concentration of 55 µM H2O2 was attained, with no H202 being detected in either dark‐incubated controls or in irradiated samples of native proteins. The UVA‐dependent H2O2 formation was increased 50% by superoxide dismutase (SOD) and abolished by catalase, arguing for the initial generation of superoxide anion. A linear photolysis of histidine and tryptophan was also seen; however, the addition of SOD or SOD and catalase had no effect on the photolytic destruction of either amino acid. Superoxide dismutase increased the oxidation of protein SH groups implicating H2O2, but SOD and catalase caused a decrease in SH oxidation only at later time periods. The direct addition of H2O2 to a water‐insoluble sonicate supernatant fraction caused only a slight oxidation of SH groups, but this was increased four‐ to eight‐fold when the protein was denatured in 4.0 M guanidine hydrochloride.Overall, the data suggest a UVA‐dependent oxidation of protein SH groups via H2O2 generated within the large protein aggregates of the water‐insoluble fraction. These data also provide a mechanism for oxidation of the sulfur‐containing amino acids in vivo—a process that is known to accompany the formation of age‐onset cataracts.
SINGLET OXYGEN GENERATION FROM LIPOSOMES: A COMPARISON OF TIME‐RESOLVED 1270 NM EMISSION WITH SINGLET‐OXYGEN KINETICS CALCULATED FROM A ONE DIMENSIONAL MODEL OF SINGLET‐OXYGEN DIFFUSION and QUENCHING
Authors: Fu Yingxian , Kanofsky Jeffrey R. 
Published: January 2008

Abstract— Time‐resolved measurements of 1270 nm singlet‐oxygen emission following pulsed‐laser excitation were made from unilamellar dimyristoyl 1‐α‐phosphatidylcholine liposomes labeled with zinc phthalocyanine. The effect of the hydrophobic quenchers, β‐carotene and ethyl β‐apo‐8′trans carotenoate, and the hydrophilic quenchers, histidine and methionine, upon the kinetics of the 1270 nm singlet‐oxygen emission was studied. Hydrophobic quenchers principally lowered the intensity of the 1270 nm emission and caused only modest changes in the lifetime of the 1270 nm emission. The decrease in 1270 nm emission caused by hydrophobic quenchers was related to the size of the liposomes. The larger the radius of the liposome, the greater the decrease in 1270 nm emission caused by a given concentration of hydrophobic quencher. In contrast, hydrophilic quenchers principally decreased the lifetime of the 1270 nm emission. The effect of hydrophilic quenchers was independent of the size of the liposomes.There was good agreement between the experimental results and the kinetics of the singlet‐oxygen emission calculated using a one dimensional model of singlet‐oxygen quenching and diffusion. The kinetics of singlet‐oxygen emission from liposomes without added hydrophobic quenchers closely approximated the theoretical kinetics of singlet oxygen in a homogeneous aqueous solution.
Function of the Reaction Center of Green Sulfur Bacteria
Authors: Sakurai Hidehiro , Kusumoto Noriaki , Inoue Kazuhito 
Published: January 2008

AbstractThe reaction center (RC) of green sulfur bacteria belongs to the Fe‐S type RC, as do the photosystem I of oxygenic photosynthetic organisms and the RC of heliobacteria. The core parts of the green sulfur bacterial and the heliobacterial RC are assumed to be homodimeric, in contrast to those of purple bacteria, photosystem I and photosystem II. This paper describes recent advances in the study of the function of the green sulfur bacterial RC.