bluuebunny/crossref_metadata_2025_split huggingface dataset:
BACTERIAL PHOTOPROTECTION THROUGH EXTRACELLULAR CADMIUM SULFIDE CRYSTALLITES
Authors: Holmes Justin D. , Smith Peter R. , Evans‐Gowing Richard , Richardson David J. , Russell David A. , Sodeau John R. 
Published: July 2010

AbstractUltraviolet light and the heavy metal, cadmium, both have toxic effects on many microorganisms. In this communication we describe a method by which the bacterium Klebsiella aerogenes surmounts both problems using one biological process: the synthesis of cadmium sulfide (CdS) crystallites. These semiconductor particles absorb radiation in the UV spectral region and therefore, when K. aerogenes produces extracellular CdS material in response to environments containing cadmium ions, a photoprotective layer is formed. The effect of UVA radiation on cultures of Klebsiella aerogenes was monitored using electron microscopy, energy‐dispersive X‐ray analysis and electronic spectroscopy. The results show that at wavelengths 320 nm Λ 400 nm, a photoprotection period of between 4 and 6 h is induced, which eventually fails due to photodegradation of the semiconductor layer to metallic cadmium and elemental sulfur.
THEORETICAL STUDY OF CIRCULAR DICHROISM OF THE LIGHT‐HARVESTING ANTENNA OF PHOTOSYNTHETIC PURPLE BACTERIA: A CONSIDERATION OF EXCITON INTERACTIONS and ENERGY DISORDER
Authors: Novoderezhkin Vladimir I. , Razjivin Andrei P. 
Published: July 2010

AbstractCircular dichroism and absorption spectra of the light‐harvesting antenna of photosynthetic purple bacteria were studied taking into account exciton interactions between the antenna bacteriochloro‐phylls. Exciton states were calculated for the core antenna configuration in the form of a circular aggregate of N identical bacteriochlorophyll molecules with CN‐symmetry. The influence of pigment inhomogeneity on the proposed exciton description of the antenna was investigated. The calculated line shapes for the circular dichroism and absorption spectra agree well with experimental data for purple bacteria.
EXCITED STATE BEHAVIOR OF PHYTOCHROME Pr
Authors: Teuchner Klaus , Schulz Michael , Stiel Holger , Maisch Manfred , Rudiger Wolfhart 
Published: July 2010

AbstractThe primary excited state processes of phytochrome, the plant chromoprotein responsible for most photomorphogenetic responses, are investigated by picosecond intensity‐dependent transmission measurements. At sufficient high excitation intensity (starting at photon flux densities of about 1′1025 cm−2 s−l) a moderate bleaching of the absorption is observed. For the quantitative analysis of the experimental data a rate equation system approach for the energy levels responsible for the ultrafast transformation Pr→ lumi‐R and the photon transport through the sample was utilized. The following was found for the excited state parameters of the phytochrome Pr: (1) an excited state absorption of the same order of magnitude as the ground state absorption (cross section: S̀exc= 4′10−16 cm−2 at 650 nm), (2) a fast relaxation of the higher excited singlet state on the femtosecond time scale.
PHOTOMORPHOGENIC RESPONSES TO UV RADIATION III: A COMPARATIVE STUDY OF UVB EFFECTS ON ANTHOCYANIN and FLAVONOID ACCUMULATION IN WILD‐TYPE and aurea MUTANT OF TOMATO (Lycopersicon esculentum MILL.)
Authors: Brandt Kirsten , Giannini Alessandro , Lercari Bartolomeo 
Published: July 2010

AbstractThe UV‐mediated induction of anthocyanin and UV‐absorbing compounds was characterized in etiolated hypocotyls of wild‐type and aurea (au) mutant tomato seedlings. Ultraviolet radiation induced significant increases of anthocyanin and UV‐absorbing compounds in hypocotyls of die au mutant and of its isogenic wild‐type, but the differences in the time courses of UV‐induced pigment accumulation indicate mat different photoregulatory mechanisms are involved for each of these two groups of pigments. It appears mat prolonged presence of adequate levels of UVB (290–320nm) energy and consequently the action of a specific UVB photoreceptor are indispensable for the photoinduction of anthocyanin accumulation in UV‐irradiated hypocotyl of the au mutant that is missing the labile phytochrome pool. The large difference found between the wild‐type and the au mutant strongly indicate the involvement of labile phytochrome as the primary functional photoreceptor for the photoinduction of anthocyanin accumulation in wild‐type tomato hypocotyls. The UVB photoreceptor could at least partly replace the action of labile phytochrome (as far as anthocyanin accumulation is concerned) when the functional phytochrome pool is missing as in the au mutant. The general picture of UV‐mediated induction of total UV‐absorbing compounds shows only a macroscopic difference between wild‐type and die au mutant of tomato: the higher initial level (in darkness) of these compounds in die wild‐type in contrast to the au mutant. Although there is UV‐induced accumulation of UV‐absorbing compounds in bom genotypes, the levels in the au mutant never reach mat of the wild‐type under the same UV exposure. A UVB photosensor may play a more important role in the photoinduction of UV‐absorbing compounds. Indeed, in the absence of labile phytochrome, i.e. in the au mutant, a UVB‐absorbing photoreceptor alone is able to establish high responsiveness for the UV‐induced flavonoid accumulation.
PSORALEN‐MEDIATED VIRUS PHOTOINACTIVATION IN PLATELET CONCENTRATES: ENHANCED SPECIFICITY OF VIRUS KILL IN THE ABSENCE OF SHORTER UVA WAVELENGTHS
Authors: Margolis‐Nunno Henrietta , Robinson Richard , Horowitz Bernard , Geacintov Nicholas E. , Ben‐Hur Ehud 
Published: July 2010

Abstract— Treatments with psoralens and long‐wavelength ultraviolet radiation (UVA, 320–400 nm; PUVA) have shown efficacy for virus sterilization of platelet concentrates (PC). Our laboratory has employed the psoralen derivative 4'‐aminomethyl‐4, 5', 8‐trimethylpsoralen (AMT), and we have found that platelet integrity is best preserved when rutin, a flavonoid that quenches multiple reactive oxygen species, is present during AMT/UVA treatment of PC.In this report, we examine the effects of different UVA spectra under our standard PC treatment conditions (i.e. 50 μg/mL AMT, 0.35 mM rutin and 38 J/cm2 UVA). Added vesicular stomatitis virus (VSV; ≥5.5 log10) was completely inactivated with the simultaneous maintenance of the platelet aggregation response (>90% of control) when a UVA light source with transmission mainly between 360 and 370 nm (narrow UVA1) was used. In contrast, with a broad‐band UVA (320–400 nm; broad UVA) light source, the aggregation response was greatly compromised (<50% of control) with only a minor increase in the rate of VSV kill. With this lamp, platelet function could be improved to about 75% of the control by adding a long‐pass filter, which reduced the transmission of shorter (≤345 nm) UVA wavelengths (340–400 nm; UVA1). At equivalent levels of virus kill, aggregation function was always best preserved when narrow UVA1 was used for PUVA treatment. Even in the absence of AMT, and with or without rutin present, narrow UVA 1 irradiation was better tolerated by platelets than was broad UVA.Our results suggest that for PUVA treatment of PC, the UVA dose range in which complete virus kill is obtained with the simultaneous maintenance of in vitro platelet function is smallest with broad UVA irradiation and largest with narrow UVA1. Thus, the virus specificity of PC treatment with AMT, UVA and quenchers can be further enhanced by the exclusion of the shorter UVA wavelength range.
A Water‐Soluble Luminescence Oxygen Sensor
Authors: Castellano Felix N. , Lakowicz Joseph R. 
Published: July 2010

ABSTRACTWe developed a water‐soluble luminescent probe for dissolved oxygen. This probe is based on (Ru[dpp(SO3Na)2]3) Cl2, which is a sulfonated analogue of the well‐known oxygen probe (Ru[dpp]3)Cl2. The compound dpp is 4,7‐diphenyl‐1,10‐phenanthroline and dpp(SO3Na)2 is a disulfonated derivative of the same ligand. In aqueous solution in the absence of oxygen (Ru[dpp(SO3Na)2]3)Cl2 displays a lifetime of 3.7 μs that decreases to 930 ns on equilibrium with air and 227 ns on equilibrium with 100% oxygen. The Stern–Vohner quenching constant is 11330 M−1. This high oxygen‐quenching constant means that the photoluminescence of Ru(dpp[SO3Na]2)3Cl2 is 10% quenched at an oxygen concentration of 8.8 x 10−6M, or equilibration with 5.4 torr of oxygen. The oxygen probe dissolved in water displays minimal interactions with lipid vesicles composed of dipalmityl‐L‐α‐phosphatidyl glycerol but does appear to interact with human serum albumin. The absorption maximum near 480 nm, long lifetime and large Stokes’shift allow this probe to be used with simple instrumentation based on a light‐emitting diode light source, allowing low‐cost oxygen sensing in aqueous solutions. To the best of our knowledge this is the first practical water‐soluble oxygen sensor.
Magnetic Field Effects on the Dynamics of Radical Pairs in Micelles: A New Approach to Understanding the “Cage Effect”
Authors: Kleinman Mark H. , Shevchenko Tatiana , Bohne Cornelia 
Published: July 2010

ABSTRACTThe effect of temperature on the photolysis of dibenzyl ketone and 4‐methyldibenzyl ketone in sodium dodecyl sulfate micelles was studied by laser flash photolysis and product distributions derived from steady‐state photolysis. At high temperatures, the product distribution and radical decay kinetics are primarily due to random encounters of radicals, and the “cage effect” cannot be rationalized by geminate recombination reactions that occur before the radicals escape from the micelles. A mechanism is proposed in which the enhancement of the crosstermination product derived from random encounters is due to the different partitioning of each radical species between the micelles and the aqueous phase, thereby leading to different rates for the self‐termination reactions.
Erythemally Weighted Radiometers in Solar UV Monitoring: Results from the WMO/STUK Intercomparison
Authors: Leszczynski Kirsti , Jokela Kari , Ylianttila Lasse , Visuri1 Reijo , Blumthaler Mario 
Published: July 2010

ABSTRACTThe first international intercomparison of erythemally weighted (EW) broadband radiometers was arranged in 1995 to improve the accuracy and comparability of the measurements carried out by solar UV monitoring networks. The intercomparison was arranged at the Radiation and Nuclear Safety Authority in Helsinki, Finland, in cooperation with the University of Innsbruck and with support from the World Meteorological Organization. Altogether 20 EW meters of six different types from 16 countries were (1) tested in the laboratory by measuring the spectral and angular responsivities and (2) calibrated in solar radiation against two reference spectroradiometers. Calibration factors (CFs) for the EW meters were determined by using simultaneously measured EW solar UV spectra as a calibration reference. The CFs averaged over solar elevations higher than 35° varied from 0.87 to 1.75, with the estimated uncertainty being ±10%. As a result of this intercomparison, for the first time the calibrations of more than 100 EW radiometers around the world are possible to trace to the same origin. The present experience indicates that the accuracy of temperature‐controlled EW radiometers is not significantly lower than the accuracy of spectroradiometers provided that strict quality assurance/quality control procedures are followed.
Oxidative Modifications of the Photosystem II D1 Protein by Reactive Oxygen Species: From Isolated Protein to Cyanobacterial Cells¶
Authors: Lupínková Lenka , Komenda Josef 
Published: July 2010

ABSTRACTAction of reactive oxygen species (ROS) on the isolated D1 protein, a key component of Photosystem II (PSII) complex, was studied and compared with the effect of high irradiance on this protein in mildly solubilized photosynthetic membranes and cells of the cyanobacterium Synechocystis. Whereas singlet oxygen caused mainly protein modification reflected by shift of its electrophoretic mobility, action of hydrogen peroxide and superoxide resulted in generation of specific fragments. Hydroxyl radicals as the most ROS induced fast disappearance of the protein. The results substantiate the ability of ROS to cause direct scission of the D1 peptide bonds. Similar D1 modification, fragmentation and additionally cross‐linking with other PSII subunits were observed during illumination or hydrogen peroxide treatment of mildly solubilized thylakoids. Peroxide‐induced fragmentation did not occur in thylakoids of the strain lacking a ligand to the nonheme iron, confirming the role of this prosthetic group in the D1‐specific cleavage. The D1 modification, fragmentation and cross‐linking were suppressed by ROS scavengers, supporting the direct role of ROS in these phenomena. Identical symptoms of the ROS‐induced D1 damage were detected in illuminated cells of Synechocystis mutants with a higher probability of ROS formation, documenting the relevance of the in vitro results for the situation in vivo.
Influence of PAR and UV‐A in Determining Plant Sensitivity and Photomorphogenic Responses to UV‐B Radiation ¶†
Authors: Krizek Donald T. 
Published: July 2010

ABSTRACTThe role of photosynthetically active radiation (400‐700 nm) (PAR) in modifying plant sensitivity and photomorphogenic responses to ultraviolet‐B (280–320 nm) (UV‐B) radiation has been examined by a number of investigators, but few studies have been conducted on ultraviolet‐A (320‐400 nm) (UV‐A), UV‐B and PAR interactions. High ratios of PAR‐UV‐B and UV‐A‐UV‐B have been found to be important in ameliorating UV‐B damage in both terrestrial and aquatic plants. Growth chamber and greenhouse studies conducted at low PAR, low UV‐A and high UV‐B often show exaggerated UV‐B damage. Spectral balance of PAR, UV‐A and UV‐B has also been shown to be important in determining plant sensitivity in field studies. In general, one observes a reduction in total biomass and plant height with decreasing PAR and increasing UV‐B. The protective effects of high PAR against elevated UV‐B may also be indirect, by increasing leaf thickness and the concentration of flavonoids and other phenolic compounds known to be important in UV screening. The quality of PAR is also important, with blue light, together with UV‐A radiation, playing a key role in photorepair of DNA lesions. Further studies are needed to determine the interactions of UV‐A, UV‐B and PAR.
Invited Review: Light at Night and Cancer Risk ¶
Authors: Schernhammer Eva , Schulmeister Karl 
Published: July 2010

ABSTRACTEnvironmental lighting powerfully suppresses the physiologic relase of melationin, which typically peaks in the middle of the night. This decreased melationin production has been hypothesized to increase the risk of cancer. Evidence from experimental studies supports a link between melationin and tumor growth. There is also fairly consistent indirect evidence from observational studies for an association between melatonin suppression, using night work as a surrgogate, and the breast cancer risk.
Rapid Communication: Direct Optical Detection of Singlet Oxygen from a Single Cell ¶
Authors: Zebger Ingo , Snyder John W. , Andersen Lars Klembt , Poulsen Lars , Gao Zhan , Lambert John D. C. , Kristiansen Uffe , Ogilby Peter R. 
Published: July 2010

ABSTRACTSinglet oxygen has been detected in single nerve cells by its weak 1270 nm phosphorescence (a1Δg→X3Σg−) upon irradiation of a photosensitizer incorporated in the cell. Thus, one can now consider the application of direct optical imaging techniques to mechanistic studies of singlet oxygen at the single‐cell level.
Analysis of Effective Molecular Diffusion Rates for Verteporfin in Subcutaneous Versus Orthotopic Dunning Prostate Tumors ¶
Authors: Zhou Xiaodong , Pogue Brian W. , Chen Bin , Hasan Tayyaba 
Published: July 2010

ABSTRACTPhotosensitizer biodistribution change inside tissue is one of the dominant factors in photodynamic therapy efficacy. In this study, the pharmacokinetics of a benzoporphyrin derivative (BPD), delivered in verteporfin for injection formulation, have been quantified in the rat Dunning prostate tumor MAT‐LyLu model, using both subcutaneous and orthotopic sites. Blood plasma sampling indicated that BPD had a bi‐exponential metabolic lifetime in vivo, with the two lifetimes being 9.6 min and 8.3 h. The spatial distributions in the tumor were quantified as a function of distance from the perfused blood vessels, using fluorescence histologic images of the tumor. A fluorescent vascular marker was used to obtain locations and shapes of perfused capillaries at a wavelength of emission different from that of BPD and to allow colocalized images to be acquired of vessel and BPD locations. Using the BPD fluorescence images obtained 15 min after intravenous administration, a forward finite‐element solution to the diffusion equation was used to predict the drug distribution by matching the fluorescence intensity images observed microscopically. An inverse solver was used to minimize the root mean square error between the image of simulated diffusion and the experimental image, resulting in estimation of the diffusion coefficient of BPD in the tumor models. Effective diffusion coefficients were 0.88 and 1.59 μm2/s for the subcutaneous and orthotopically grown tumors, respectively, indicating that orthotopic tumors have significantly higher vascular extravasation rates as compared with subcutaneous tumors. This analysis supports the hypothesis that leakage rates of the photosensitizer vary considerably. Thus, although varying the time between injection and optical irradiation may be used to vary the targeting between vascular and less vascular areas, the precise time of treatment will depend on the nature of the permeability of the vasculature in the tissue being treated.
Blue Light‐induced Chloroplast Reorientations in Lemna trisulca L. (Duckweed) are Controlled by Two Separable Cellular Mechanisms as Suggested by Different Sensitivity to Wortmannin¶
Authors: Grabalska Magdalena , Malec Przemysław 
Published: July 2010

ABSTRACTChlorplast reorientations within mesophyll cells are among the most rapid physiological responses of higher plants to blue light. At light intensities below the saturation point of photosynthesis, chloroplasts move to the cell walls perpendicular to the direction of light and maximize light absorption (low‐fluence rate response [LFR]. At light intensities above the saturation point of photosythesis, chloroplasts, redistribute to cell walls parallel to the direction of light (hight‐fluence rate response [HFR]). The actin‐based mechanism is responsible for the light‐induced chloroplast movements. We have found that an inhibitor of phosphoinositide‐3‐kinases, wortmannin, potently and irreversibly inhibited LFR and HFR chloroplast responses to blue light in Lemna trisulca L. mesophyll cells. Microscopic observations and photometric measurement indicated that 100 nM wortmannin specifically inhibited LFR in Lemna, whereas HFR displayed no sensitivity to the inhibitor at this concentraion. A complete inhibition of the HFR could be obtained by 1 μM wortmannin. These data indicate that LFR is more sensitive to wortmannin than HFR and suggest that these two responses may be under the control of different cellular mechanisms. Our results suggest that phosphoinositide kinases and other phosphoinositide cycle enzymes may play a role in the transduction of the light signal to the actin cytoskeleton in Lemna as factors specifying the direction of chloroplast movements. A hypothetical model assuming three signaling pathways regulating light‐induced chloroplast reorientations in mesophyll cells is proposed.
The Solvent‐initiated Photolysis of Dichloro(2,2′‐bipyridine)platinum(II) in Chloroform¶
Authors: Whang Sharon , Estrada Toño , Hoggard Patrick E. 
Published: July 2010

ABSTRACTUnder 254 nm irradiation, [Pt(bpy)Cl2] is converted to [Pt(bpy)Cl4] in a solvent‐initiated process. The reaction is very nearly zero order throughout. The rate decreases slightly with increasing starting concentration. These characteristics can be rationalized by a rate law of the form afs, where fs, is the fraction of light absorved by chloroform. The species that reacts with [Pt(bpy)Cl2] is believed to be CCl3OO.
Involvement of G Proteins in the Mycelial Photoresponses of Phycomyces¶
Authors: Tsolakis George , Moschonas Nicholas K. , Galland Paul , Kotzabasis Kiriakos 
Published: July 2010

ABSTRACTMany responses of the zygomycete fungus Phycomyces blakesleeanus are mediated by blue light, e.g. the stimulation of β‐carotene synthesis (photocarotenogenesis) and the formation of fruiting bodies (photomorphogenesis). Even though both responses have been described in detail genetically and biophysically, the underlying molecular events remain unknown. Applying a pharmacological approach in developing mycelia, we investigated the possible involvement of heterotrimeric G proteins in the blue‐light transduction chains of both responses. G protein agonists (guanosine triphosphate analogues, cholera toxin, pertussis toxin) mimicked in darkness the effect of blue light for both responses, except for cholera toxin, which was ineffective in increasing the β‐carotene content of dark‐grown mycelia. Experiments combining the two toxins indicated that photocarotenogenesis could involve an inhibitory G protein (Gi) type, whereas photomorphogenesis may depend on a transducin (Gt type)‐like heterotrimer. The determination of the carB (phytoene dehydrogenase) and chs1 (chitin synthase 1) gene expression under various conditions of exogenous challenge supports the G protein participation. The fluctuations of the time course measurements of the carB and chs1 transcripts are discussed.
Field Testing of Biological Spectral Weighting Functions for Induction of UV‐absorbing Compounds in Higher Plants†¶
Authors: Flint Stephan D. , Searles Peter S. , Caldwell Martyn M. 
Published: July 2010

ABSTRACTAction spectra are typically used as biological spectral weighting functions (BSWF) in biological research on the stratospheric ozone depletion issue. Despite their critical role in determining the amount of UV supplied in experiments, there has been only limited testing of different functions under realistic field conditions. Here, we calculate effective radiation according to five published BSWF and evaluate the appropriateness of these BSWF in representing the induction of UV‐absorbing compounds. Experiments were carried out in the field using both ultraviolet‐B radiation (280–320 nm) supplementation and selective filtering of solar UV radiation. For the four species tested, BSWF that extend into the ultraviolet‐A radiation (320–400 nm) (UV‐A) with moderate effectiveness best represented the observed results. When compared with the commonly used generalized plant response, these BSWF suggest that simulations of ozone depletion will require more radiation than in the past experiments. However, they imply lower radiation supplements than a new plant growth BSWF that has a greater emphasis on UV‐A wavelengths.