bluuebunny/crossref_metadata_2025_split huggingface dataset:
TRENDS AND INTERANNUAL VARIATIONS IN ERYTHEMAL SUNLIGHT,1978–1993
Authors: Frederick John E. , Erlick Carynelisa 
Published: January 2008

Abstract—Information on column ozone and the earth's reflectivity obtained from satellite‐based data allows estimates of the long‐term behavior in erythemal irradiance at any location, including the attenuation provided by clouds. Year‐to‐year changes in cloudiness over specific geographic regions make a major contribution to interannual variability in irradiance at the ground. Although the general decline in column ozone amounts acted to increase erythemal irradiance over the period November 1978 to April 1993, these changes tend to be obscured by the erratic variability associated with cloudiness. The noise introduced into a time series of erythemal irradiance by clouds effectively widens the error bars assigned to derived trends. This behavior could complicate attempts to establish links between any observed changes in the biosphere and measured changes in the ozone layer.
THE EFFECT OF PHOTODYNAMIC TREATMENT OF YEAST WITH THE SENSITIZER CHLOROALUMINUM PHTHALOCYANINE ON VARIOUS CELLULAR PARAMETERS
Authors: Paardekooper Michel , Gompel Angeline E. Van , Steveninck John Van , Broek Peter J. A. Van den 
Published: January 2008

Abstract—Photodynamic treatment of Kluyveromyces marxianus with chloroaluminum‐phthalocyanine resulted in loss of clonogenicity. Several parameters were studied to identify targets that could be related to loss of colony‐forming capacity. Inhibition of various plasma membrane‐bound processes was observed, such as substrate transport and plasma membrane ATPase activity. Moreover, K+ loss from the cells was observed. Photodynamic treatment also reduced the activity of various enzymes involved in energy metabolism, thereby decreasing the cellular ATP level. It will be discussed however that none of these processes is likely to be related directly to loss of clonogenicity. Treatment with phthalocyanine and light resulted in a strong inhibition of the incorporation of 14C‐phenylalanine in trichloracetic acid‐precipitable material. The induction of the β‐galactoside utilization system was also strongly inhibited. The latter two processes did not recover during incubation, subsequent to photodynamic treatment. It is concluded that photodynamically induced inhibition of protein synthesis is a critical factor contributing to the loss of clonogenicity.
PHOTODYNAMICALLY GENERATED 3‐β‐HYDROXY‐5α‐CHOLEST‐6‐ENE‐5‐HYDROPEROXIDE: TOXIC REACTIVITY IN MEMBRANES and SUSCEPTIBILITY TO ENZYMATIC DETOXIFICATION
Authors: Geiger Peter G. , Korytowski Witold , Girotti Albert W. 
Published: January 2008

Abstract—Singlet oxygen (1O2)‐mediated photooxidation of cholesterol gives three hydroperoxide products: 3β‐hydroxy‐5α‐cholest‐6‐ene‐5‐hydroperoxide (5α‐OOH), 3β‐hydroxycholest‐4‐ene‐6α‐hydrope‐roxide (6α‐OOH) and 3β‐hydroxycholest‐4‐ene‐6β‐hydroperoxide (6β‐OOH). These species have been compared with respect to photogeneration rate on the one hand and susceptibility to enzymatic reduction/ detoxification on the other, using the erythrocyte ghost as a cholesterol‐containing test membrane and chloroaluminum phthalocyanine tetrasulfonate (AlPcS4) as a 1O2 sensitizer. Peroxide analysis was accomplished by high‐performance liquid chromatography with mercury cathode electrochemical detection (HPLC‐EC[Hg]). The initial rate of 5α‐OOH accumulation in AlPcS4/light‐treated ghosts was found to be about three times greater than that of 6α‐OOH or 6β‐OOH. Membranes irradiated in the presence of ascorbate and ferric‐8‐hydroxyquinoline (Fe[HQ]2, a lipophilic iron complex) accumulated lesser amounts of 5α‐OOH, 6α‐OOH and 6β‐OOH but relatively large amounts of another peroxide pair, 3β‐hydroxycholest‐5‐ene‐7α‐ and 7β‐hydroperoxide (7α,7β‐OOH), suggestive of iron‐mediated free radical peroxidation. When photoperoxidized membranes containing 5α‐OOH, 6α,6β‐OOH and 7α,7β‐OOH (arising from 5α‐OOH rearrangement) were incubated with glutathione (GSH) and phospholipid hydroperoxide glutathione peroxidase (PHGPX), all hydroperoxide species underwent HPLC‐EC(Hg)‐detect‐able reduction to alcohols, the relative first order rate constants being as follows: 1.0 (5α‐OOH), 2.0 (7α,7β‐OOH), 2.4 (6α‐OOH) and 3.2 (6β‐OOH). Relatively rapid photogeneration and slow detoxification might make 5α‐OOH more cytotoxic than the other peroxide species. To begin investigating this possibility, we inserted 5α‐OOH into ghosts by transferring it from 5α‐OOH‐containing liposomes. When exposed to Fe(HQ)2/ascorbate, these ghosts underwent GSH/PHGPX‐inhibitable chain peroxidation, as indicated by the appearance of 7α,7β‐OOH, phospholipid hydroperoxides and thiobarbituric acid reactive substances. Liposomal 5α‐OOH also exhibited a strong, Fe(HQ)2‐enhanced, toxicity toward LI210 leukemia cells, an effect presumably mediated by damaging chain peroxidation. This appears to be the first reported example of eukaryotic cytotoxicity attributed specifically to 5α‐OOH.
REDUCED NEAR‐UV SENSITIVITY IN Phycomyces MUTANTS AFFECTED IN THE BIOSYNTHESIS OF 6,7‐DIMETHYL‐8‐RIBITYLLUMAZINE
Authors: Tillmanns Sascha , Senger Horst , Galland Paul 
Published: January 2008

Abstract—Riboflavin‐requiring mutants of Phycomyces blakesleeanus with defects in the genes ribA, ribB, ribC and ribD were analyzed with respect to their contents of flavins, 6,7‐dimethyl‐8‐ribityllu‐mazine (DMRL) and pterins as well as their phototropic sensitivity. Strains were grown on minimal medium enriched with 10−6M riboflavin (RB), and the concentrations of the respective pigments in sporangiophores were determined by HPLC. In strains A607 ribC401 and A641 ribC402 madA7 a loss of DMRL correlated with a loss of near‐UV sensitivity. In general terms, the results suggest the participation of DMRL in photoreception, which does not necessarily imply DMRL as a photoreceptor chromophore. In more specific terms, the result could be understood on the basis of a UV/blue‐light photoreceptor, which includes besides a flavin also a lumazine‐like chromophore. Mutants C318 ribA I and C323 ribA4 accumulated DMRL, the immediate precursor of RB, as well as biopterin and neopterin. Mutant C322 ribB contained normal amounts of DMRL and pterins. Mutant C324 ribD5 had reduced amounts of neopterin and biopterin. The fact that some of the RB‐requiring mutants displayed abnormal amounts of pterins indicates a common regulation for the flavin and the pterin pathway.
INTERACTION BETWEEN HUMAN α1ACID GLYCOPROTEIN (OROSOMUCOID) AND 2‐p‐TOLUIDINYLNAPHTHALENE‐6‐SULFONATE
Authors: Albani J. , Vos R. , Willaert K. , Engelborghs Y. 
Published: January 2008

Abstract—The interaction between human α1‐acid glycoprotein (orosomucoid) and the fluorescent probe, 2‐p‐toluidinylnaphthalene‐6‐sulfonate (TNS) has been studied. An association constant of 16.7 (±3) X 103M‐1 was obtained for the complex at 20°C with a stoichiometry of 1:1. From the effect of temperature on the binding process, the standard enthalpy change for the binding is calculated to be ΔH0= ‐18 ± 3 kJ mol‐1 and the standard entropy change ΔS0= 19 ± 12 J K‐1 mol‐1. The tryptophan fluorescence of the protein can be described by a sum of three exponentials. Upon TNS binding, the average fluorescence lifetime of the protein in the complex changes much less than the fluorescence intensity. The bound TNS is therefore a very efficient acceptor for the protein fluorescence. The TNS bound to orosomucoid presents two fluorescence lifetimes 1 1 and 4.3 ns. The possible origins of the two lifetimes are discussed.
14N Electron Spin Echo Envelope Modulation (ESEEM) Spectroscopy of the Cation Radical P840+, the Primary Electron Donor of the Chlorobium limicola Reaction Center
Authors: Bratt Peter J. , Muhiuddin Irine P. , Evans Michael C. W. , Heathcote Peter 
Published: January 2008

AbstractThe electronic structure of the oxidized primary chlorophyll electron donor, P840+., of the green sulfur bacterium Chlorobium limicola has been investigated using electron spin echo envelope modulation (ESEEM) spectroscopy. This ESEEM investigation of the electron spin density distribution in the radical cation P840+. in membranes isolated from C. limicola confirms that the electron spin is shared eqully between the two bacteriochlorophyll a molecules. Observation of the small hyperfine couplings to the ring nitrogens by ESEEM gives results that are in agreement with those obtained from ENDOR measurements (S. E. J. Rigby, R. Thapar, M. C. W. Evans and P. Heathcote, FEBS Lett. 350,24–28, 1994) of the large hyperfine couplings to the methyl group protons. These results in combination with the Raman spectroscopy of P840 (U. Feiler, D. Albouy, B. Robert and T. A. Mattioli, Biochemistry 34,11099–11105, 1995) all indicate that the reaction center of green sulfur photosynthetic bacteria is functionally a protein homodimer providing a symmetrical protein environment for the primary electron donor.
Temperature Dependence of Charge Recombination in Heliobacillus mobilis
Authors: Chlou Hung‐Cheng , Blankenship Robert E. 
Published: January 2008

AbstractTransient absorption difference spectroscopy was used to study the temperature dependence of the P798+ decay kinetics in heliobacteria. For membrane samples, two components were obtained from the fitting of kinetic traces in the temperature range of4–29°C. A3–9 ms component representing the cytochrome (cyt) c oxidation has an activation energy of 33.0 ± 2.8 KJ/mol. A12–22 ms component representing either P798+Fx ‐ or P798+FA/B recombination has an activation energy of 15.3 ± 2.4 KJ/mol. In isolated reaction centers (RC), only one 14 ms component due to P798+Fx ‐ recombination was obtained in this temperature range. The Arrhenius plot shows that the recombination rate of this P798+Fx ‐ state is temperature independent in the near room temperature range. For RC in the temperature range of60–298 K, a12–15 ms decay was obtained at temperatures greater than 240 K. Biphasic decay traces (12–15ms and2–4 ms components) were obtained at temperatures between 170 K and 230 K. Only one2–4 ms component was found at temperatures lower than 160 K. The gradual switchover from the12–15 ms to the2–4 ms component upon cooling may indicate the shift of the P798+Fx ‐ recombination state to a state that is prior to P798+Fx, although other interpretations can not be excluded. The absorption difference spectrum (ΔA@ 160 K ‐ ΔA@ 240 K) in the blue region shows a positive amplitude below 405 nm and a negative amplitude above 405 nm implying that the2–4 ms decay component may be due to the recombination of P798+A1‐, where A1 is a quinone‐type acceptor.
Site‐Directed Mutagenesis and Analysis of Second‐Site Revertants Indicates a Requirement for C‐Terminal Amino Acids of PsaB for Stable Assembly of the Photosystem I Reaction Center Complex in Chlamydomonas reinhardtii
Authors: Lee Hyeonmoo , Bingham Scott E. , Webber Andrew N. 
Published: January 2008

AbstractThe PsaA and PsaB polypeptides form the reaction center core heterodimer of photosystem I (PSI). Both PsaA and PsaB are predicted to have 11 hydrophobic domains, although it is unclear how both polypeptides fold within the thylakoid membrane. If all 11 hydrophobic regions form membrane‐spanning domains, the N‐ and C‐terminus must be located on opposite sides of the membrane. The C‐terminus of PsaB is very conserved in a wide range of organisms and may be important for PSI assembly or function. Using chloroplast transformation in Chlamydomonas reinhardtii we have generated a series of C‐terminal extension and deletion mutants of the PsaB polypeptide. Analysis of these mutants and spontaneous revertants indicates that the C‐terminus may be extended by at least 14 amino acids without impairing PSI assembly. Deletion of amino acids 732–736 also has no impact on PSI, whereas deletion of amino acids 727–736 results in no accumulation of the complex. The site of truncation in the 727–736 deletion coincides with the end of the hydrophobic domain XI supporting a location of the C‐terminus of PsaB on the lumenal side of PSI.
Thymidine‐Psoralen Photoaddition: Stereoselective Formation of Atrans‐synPyrone Adduct
Authors: Décout Jean‐Luc , Guendouz Amine , Lhomme Jean 
Published: January 2008

AbstractTo study the photoreactions between thymidine and psoralen and to devise a synthetic route to prepare thymidine‐5‐methoxypsoralen adducts, we have synthesized a compound in which thymidine is linked to a 5‐methoxypsoralen derivative by a short flexible chain located to allow only the formation ofsynintramolecular [2+2] cycloadducts. Irradiation at 365 nm carried out at usual concentrations (10−2‐10−3M) resulted in a regioselective dimerization involving the 3,4 double bonds. Extreme dilution (c5 × 106M) was necessary to observe the intramolecular photoaddition, which produces exclusively the 3,4‐trans‐synadduct. These results are compared to those obtained previously with similar heterodimers that lead exclusively to the 3,4‐cis‐antithymine or thymidine‐psoralen adduct on exposure to near UV light.
8‐Oxodeoxyguanosine Formation in the DNA of Cultured Cells After Exposure to H2O2 Alone or with UVB or UVA Irradiation
Authors: Rosen J. E. , Prahalad A. K. , Williams G. M. 
Published: January 2008

AbstractThe objective of the present study was to establish whether H2O2 alone or in the presence of UVA or UVB would give rise to formation of the oxidatively damaged DNA base 7, 8‐dihydro‐8‐oxo‐2′‐deoxyguanosine (8‐oxo‐dG) in cultured adult rat liver (ARL‐18) epithelial cells. Hydrogen peroxide alone at 5 mM increased 8‐oxo‐dG levels by 42% of that of culture control. Compared to culture control, UVB exposure at a dose of 0.63 J/cm2 elevated 8‐oxo‐dG levels only 8.4%. In the presence of 5 mM H2O2+ UVB (0.63 J/cm2), 8‐oxo‐dG levels were elevated 155% above culture control suggesting a synergistic effect. A UVA dose of 10 J/cm2 did not elevate 8‐oxo‐dG levels above culture control. In the presence of 5 mM H2O2 plus UVA (12 J/cm2), 8‐oxo‐dG levels were elevated 310% above controls compared with an increase of 75.8% above control levels at the same dose in the absence of H2O2. These results reveal that both UVA or UVB can promote H2O2 generation of reactive oxygen species (ROS) in whole cells resulting in an increase in the formation of 8‐oxo‐dG, although the photodynamic generation of ROS from H2O2 occurs with a much higher efficiency in the presence of UVB. Our study also demonstrates that 8‐oxo‐dG can be generated in cellular DNA of whole cells exposed to H2O2 and UVA or UVB, indicating that the ROS generated in whole cell systems are long enough lived to migrate to the nucleus and cause DNA damage.
Hypericin‐Induced Phototoxicity in Cultured Fibroblasts and Swine Erythrocytes
Authors: Yu Hai , Wolford Suzanne T. , Kegode Redempta , Zhao Wei , Osweiler Gary D. 
Published: January 2008

AbstractHypericin is a naturally occurring photosensitizer, whose presence in plants has been responsible for cutaneous phototoxicity in grazing animals. The photosensitizing properties of this agent have recently been exploited in models for anti‐tumor and anti‐viral activity. The cytotoxicity of hypericin and light was assessed in 3T3 mouse fibroblasts using the MTT [3‐(4, 5‐dimethylthiazol‐2‐yl)‐2, 5‐diphenyl tetrazolium bromide)] assay and the lactate dehydrogenase (LDH) leakage assay. Membrane damage was assessed in swine erythrocytes using hemolysis, potassium (K+) leakage and formation of lipid hydroperoxides. Concentration‐ and light‐dependent decreases in fibroblast viability were seen starting at hypericin concentrations of 1.25 μM and light power flux levels of 24 J/cm2 using a visible light source and at 0.417 μM hypericin and a similar light dose using a solar simulator, No LDH leakage was observed at hypericin concentrations up to 30 μM and visible light up to 144 J/cm2. Light‐and/or concentration‐dependent increases in hemolysis, K+ leakage and formation of lipid hydroperoxides in red blood cell (RBC) membranes were observed, but at concentrations and light doses much greater than those required to induce cytotoxicity in fibroblasts. Lipid peroxidation and hemolysis occurred at 15 μM hypericin and 24 J/cm2 (visible light source). Potassium ion leakage occurred at concentrations and light levels as low as 5 μM and 12 J/cm2 or 15 μM and 4.8 J/cm2 (visible light source) but was still a less sensitive indicator than fibroblast cytotoxicity. Evidence for both type I and type II reactions was shown in RBC membranes by TLC analysis of cholesterol products. In the absence of light, hypericin appears to be relatively nontoxic in the models tested.
Signal Transduction and HIV Transcriptional Activation After Exposure to Ultraviolet Light and Other DNA‐Damaging Agents
Authors: Valerie Kristoffer , Laster William S. , Cheng Luhua , Kirkham Jean C. , Reavey Peter , Kuemmerle Nancy B. 
Published: January 2008

AbstractShort wavelength (254 nm) ultraviolet light (UVC)† radiation was much more potent in activating transcription of human immunodeficiency virus 1 (HIV) reporter genes stably integrated into the genomes of human and monkey cells than ionizing radiation (IR) from a 137Cs source at similarly cytotoxic doses. A similar differential was also observed when c‐jun transcription levels were examined. However, these transcription levels do not correlate with activation of nuclear factor (NF)‐kB and AP‐1 measured by band‐shift assays., i. e. both types of radiation produce similar increases in NF‐kB and AP‐1 activity, suggesting existence of additional levels of regulation during these responses. Because of the well‐established involvement of cytoplasmic signaling pathways in the cellular response to tumor necrosis factor‐α (TNF‐α), UVC, and IR using other types of assays, the role of TNF‐α in the UVC response of HIV and c‐jun was investigated in our cell system. We demonstrate that UVC and TNF‐α activate HIV gene expression in a synergistic fashion, suggesting that it is unlikely that TNF‐α is involved in UVC activation of HIV transcription in stably transfected HeLa cells. Moreover, maximum TNF‐α stimulation resulted in one order of magnitude lower levels of HIV expression than that observed after UVC exposure. We also observed an additive effect of UVC and TNF‐α on c‐jun steady‐state mRNA levels, suggestive of a partial overlap in activation mechanism of c‐jun by UVC and TNF‐α; yet these responses are distinct to some extent. Our results indicate that the HIV, and to some extent also the c‐jun, transcriptional responses to UVC are not the result of TNF‐α stimulation and subsequent downstream cytoplasmic signaling events in HeLa cells. Additional levels of regulation that do not directly involve the NF‐kB and AP‐1 transcription factors, such as changes in chromatin structure associated with the UV repair process, may also be important for a full transcriptional response of HIV and c‐jun to UVC. In addition to the new data, this report also summarizes our current views regarding UVC‐induced activations of HIV gene expression in stably transfected cells.
Log‐Normal Description of Fluorescence Spectra of Organic Fluorophores
Authors: Burstein Edward A. , Emelyanenko Victor I. 
Published: January 2008

AbstractThe smooth fluorescence bands of various organic fluorophores of different classes (e. g. indole, tryptophan, tyrosine, phthalimides, quinine sulfate, aminopyridines, acetylanthracenes) in different ionization states of their substituents and dissolved in various solvents can be accurately fitted on the frequency (wavenumber) scale by the four‐parametric log‐normal distribution curves up to the far spectral wings. This fact suggests that the log‐normal function is a good analytical description for smooth emission spectra of so‐called complex molecules. Examination of log‐normal parameters of 126 spectra of several tryptophan derivatives measured in different ionization states in various solvents revealed a straight‐linear relation between three shape parameters of the log‐normal function, namely, the positions of spectral maxima and of the two half‐maximal amplitudes. This fact indicates that only one parameter is needed to describe the band shape for the set of tryptophan derivatives. A similar linearity was also observed for the series of spectra of 1‐ and 2‐acetylanthracenes or 3‐amino‐N‐methyl‐phthalimides when varying the solvent. As a result, the spectral maximum position can entirely determine the shape of emission spectra of a series of a fluorophore derivatives in any environmental condition. Such a simplified mathematical representation significantly facilitates the problem of analytical resolution of composite fluorescence spectra, for instance, those of proteins.
Lethal Effect Induced in Pseudomonas aeruglnosa Exposed to Ultraviolet‐A Radiation
Authors: Fernández Rubén O. , Pizarro Ramón A. 
Published: January 2008

AbstractUltraviolet‐A (365 nm, 120 kJ/m2/h) exposure caused cell death in Pseudomonas aeruginosa at doses at which Escherichia coli cell viability was not affected. We have not found that UVA induced growth delay or any other sublethal effect. Irradiated suspensions of P. aeruginosa showed a marked reduction in membrane‐bound succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH) activities. Succinate‐driven respiration and several nutrient transport systems were also inhibited. Whereas SDH and LDH activities were independent of the irradiation conditions, cell viability, respiration and transport systems were protected when irradiation was performed in an N2 atmosphere. A similar protective effect was observed when cells were grown in media containing glycerol or when preirradiation bacterial growth was carried out at 30°C (instead of 37°C). Results suggest that UVA induces a differential damaging effect on several biochemical functions of P. aeruginosa. The UVA induced photodamage may fall into two categories: indirect damage mediated by oxygen (cell killing and inhibition of respiration and transport systems) and direct damage to SDH and LDH (apparently not oxygen dependent). These enzymes and leucine transport appear not to be involved in the lethal effect described herein because they were altered despite viability‐preserving conditions.
Circular and Linear Dichroism of Aggregates of Chlorophyll a and Chlorophyll b in 3‐Methylpentane and Paraffin Oil
Authors: Oksanen J. A. I. , Helenius V. M. , Hynninen P. H. , Amerongen H. van , Korppi‐Tommola J. E. I. , Grondelle R. van 
Published: January 2008

AbstractA circular (CD) and linear dichroism (LD) study of the water adducts of the green plant chlorophylls a (Chl a) and b (Chl b) in hydrocarbon solvents 3‐methylpentane and paraffin oil is presented. A strong red shift of the Qy‐absorption band from 663 to 746 nm (1678 cm−1) is observed as the water adduct of Chl a is formed. The Chl a‐water adduct shows a strong, nonconservative CD signal, which is characterized by a positive peak at 748 nm and two negative peaks at 720 and 771 nm. The maximum CD (AL ‐ AR) is only one order of magnitude smaller than the isotropic absorption maximum. We propose that this exceptionally strong signal is the so‐called psi‐type CD. The LD spectrum was measured in a flow of paraffin oil. The isotropic absorption maximum peaks at 742 nm in paraffin oil, whereas the maximum of the LD signal is at 743 nm. The LD signal is positive over the whole water‐adduct absorption band indicating that the transition dipole of the 742 nm transition is preferentially oriented along the long axis of the aggregate. The structure of the Chl b‐water adduct is less well defined. The preparations of the Chl b‐water adduct are unstable. The Chl b‐water adduct absorption band maximum is at 683 nm. The CD signal of the Chl a‐water adduct is about 200‐fold the CD of the Chl b‐water adduct. We could not orient the Chl b‐water adducts by flow, which suggests that the adducts are small or disordered.