bluuebunny/crossref_metadata_2025_split huggingface dataset:
SURFACE‐ENHANCED RESONANCE RAMAN SCATTERING SPECTROSCOPY AS A SURFACE TOPOGRAPHY PROBE IN PLANT PHOTOSYNTHETIC MEMBRANES
Authors: Picorel R. , Bakhtiari M. , Lu T. , Cotton T. M. , Seibert M. 
Published: January 2008

Abstract—Strong resonance Raman (RR) and surface‐enhanced resonance Raman scattering (SERRS) signals from carotenoids were detected from thylakoid (stromal‐side out) vesicles and inside‐out (lumenal‐side out) vesicles isolated from spinach chloroplasts. The intensity of the signals from both types of membranes was comparable, indicating that plant carotenoids are exposed on or close to both surfaces or sides of the thylakoid membrane. This is in contrast to previous studies with bacterial photosynthetic membranes (Picorel et al., 1988, J. Biol. Chem. 263, 4374–4380; and 1990, Biochemistry29, 707–712) that show carotenoids selectively located on the cytoplasmic side. In addition; strong RR and SERRS signals were detected from stacked and unstacked photosystem‐II‐enriched membrane fragments, demonstrating that carotenoids are also exposed on both surfaces of the appressed region of the thylakoid membrane. Antibodies against the photosystem (PS) II extrinsic proteins blocked SERRS signals from stacked PS II membrane fragments, but only partially affected the SERRS signals from unstacked membranes. The results indicate that these antibodies, which preferentially cover the surface of the original lumenalside of the appressed region, act as spacers between the membrane and SERRS electrode surfaces. The original stromal‐side of the appressed region is unaffected. These findings verify the distance sensitivity of the SERRS technique and underscore the above conclusion about the location of carotenoids in the appressed regions. Finally, SERRS signals are sensitive to membrane aging and storage temperature; caution is suggested to those applying SERRS spectroscopy to intact membrane systems.
REPAIR OF THYMINE DIMERS AND (6–4) PHOTOPRODUCTS IN GROUP A XERODERMA PIGMENTOSUM CELL LINES HARBORING A TRANSFERRED NORMAL CHROMOSOME 9
Authors: Ishizaki Kanji , Matsunaga Tsukasa , Kato Mitsuo , Nikaido Osamu , Ikenaga Mituo 
Published: January 2008

Abstract—Transfer of a normal chromosome 9 into a xeroderma pigmentosum (XP)‐A cell line partially restored its DNA repair activity. XP‐A cell lines harboring a transferred chromosome were much more UV‐resistant than parental XP‐A cells but still more UV‐sensitive than normal cells. The amount of UV‐induced unscheduled DNA synthesis was only one‐third of that in normal cells. The repair of thymine dimers and (6–4) photoproducts in these cell lines was analyzed by using monoclonal antibodies raised against them. Although these XP‐A cell lines carrying a normal chromosome 9 could repair (6–4) photoproduct with a little lower efficiency than normal cells, the repair of thymine dimers was completely absent in these cells. The present results suggest a gene‐dosage effect in DNA excision repair mechanisms in human cells or a rather complicated mechanism which involves two or more pathways.
PHOTORECEPTOR PIGMENT IN Blepharisma: H+ RELEASE FROM RED PIGMENT
Authors: Matsuoka Tatsuomi , Murakami Yasunori , Furukohri Takahiro , Ishida Masaki , Taneda Koji 
Published: January 2008

Abstract—In faded cells of Blepharisma kept in a standard saline solution containing bacteria which had been cultured on agar plates containing glucose and polypepton, threshold light intensity for step‐up photophobic response elevated. This result suggests that red pigment (blepharismin) contained in Blepharisma cells is involved in the step‐up photophobic response. The pH of the aqueous solution of the red pigment was found to decrease when light was applied, indicating that the pigment releases H+ in response to light stimulation. However, faded pigment preparation by light irradiation did not show pH decrease. In the living cells faded by light irradiation, threshold light intensity for the step‐up photophobic response was raised. Results suggest that H+ release from the red pigment induced by light irradiation might be responsible for the step‐up photophobic response of the cells.
EFFECTS OF RHODAMINE 123 IN THE DARK AND AFTER IRRADIATION ON MITOCHONDRIAL ENERGY METABOLISM
Authors: Atlante Anna , Passarella Salvatore , Moreno Giuliana , Salet Christian 
Published: January 2008

Abstract—Isolated rat liver mitochondria have been used to study the mechanism of toxicity of Rhodamine 123 (Rho 123) in the dark and after irradiation with visible light. We report an inhibition of adenosine 5′‐diphosphate phosphorylation which is increased after illumination. In the dark, the first steps of the phosphorylation process (i.e. the entry of substrates into the matrix, the electron transport to oxygen and the creation of the proton gradient) as well as ATPase activity are not significantly perturbed at Rho 123 concentration below 10 μg/mL. In contrast, the movements of the phosphate compounds are drastically impaired. Irradiation strengthens the detrimental effects in an oxygen dependent process. The nature of the noxious transient species is not clearly established, but it is suggested that singlet oxygen could be responsible for the observed damage.
EFFECTS OF PHOTODYNAMIC TREATMENT OF PLATELETS OR ENDOTHELIAL CELLS in vitro ON PLATELET AGGREGATION
Authors: Henderson B. W. , Owczarczak B. , Sweeney J. , Gessner T. 
Published: January 2008

Abstract—The purpose of this work was to gain insight into the role played by platelets and endothelial cells in the development of thrombogenic vascular events, observed after in vivo photodynamic therapy (PDT), by studying the in vitro effects of PDT on isolated human platelets and cultured human and bovine endothelial cells. Exposure to Photofrin II (PII) and light caused platelets to rapidly lose their ability to aggregate. Photofrin II alone at high concentrations also exerted inhibitory effects on aggregation. Endothelial cells exposed to PII‐ and phthalocyanine (GaCI‐PcS2,3 or Zn‐PCS1,2)‐mediated PDT released potent platelet anti‐ and disaggregating activity which could be identified as prostacyclin by the following criteria: a close correlation between the time and dose dependent anti‐aggregating effects and released 6‐keto‐PGF1α (the spontaneous hydrolysis praduct of PGI, determined by radioimmunoassay), the inhibition of these effects by indomethacin, accumulation of 6‐keto‐PGF1α metabolite in the media of cells treated with PDT (as determined by HPLC analysis), and the absence of evidence for significant nitric oxide production. This prostacyclin release occurred following plasma membrane damage. Although no pro‐aggregating activity was observed, endothelial cells were found to release considerable amounts of arachidonic acid and prostaglandin F2α in response to PDT. These data, which indicate powerful anti‐thrombogenic effects in vitro, are in sharp contrast to the vascular effects of PDT in vivo which are characterized by severe platelet aggregation, and imply that the in vivo effects involve additional components of the vascular system.
LOW TEMPERATURE ABSORBANCE AND FLUORESCENCE SPECTROSCOPY OF THE PHOTOACTIVE YELLOW PROTEIN FROM Ectothiorhodospira halophila
Authors: Hoff W. D. , Kwa S. L. S. , Grondelle R. van , Hellingwerf K. J. 
Published: January 2008

Abstract—A simplified procedure was developed to purify the photoactive yellow protein (PYP) from Ecrorhiorhodospira halophila. Specific antibodies were used to follow the distribution of PYP through the separate purification steps. Low temperature absorbance and fluorescence characteristics of this photoactive protein were investigated.The absorbance spectrum of PYP in 67% (vol/vol) glycerol peaked at 449 and 447 nm, at room‐and liquid nitrogen temperatures, respectively. It sharpened significantly upon cooling to 77 K and displayed fine‐structure on the blue side of its absorbance maximum, with a spacing of 25 nm.At room temperature PYP fluoresced with a quantum yield of approximately 3.5 times 10−‐3 an emission maximum of 495 nm. Maximal excitation occurred at 457 nm, 10 nm red‐shifted with respect to the absorbance maximum. At ‐low temperature the excitation maximum remained unaltered but maximal emission shifted significantly to the blue (to 482 nm). The quantum yield of fluorescence increased to 0.07 at this temperature.Illumination of PYP at low temperature with light from the visible part of the spectrum of electromagnetic radiation induced pronounced changes in its absorbance and fluorescence characteristics. At least two new stable intermediates were formed: one highly fluorescent, with an excitation maximum at 430 nm; additionally, a non‐fluorescent red‐shifted intermediate with an absorbance maximum at 490 nm. The amount formed of these two intermediates depended strongly on the wavelength of actinic illumination.In combination, these data underline the spectroscopic similarities between PYP and the retinal‐containing chromoproteins that are present in Halobacterium halobium.
ISOPIMPINELLIN IS PHOTOBIOLOGICALLY INACTIVE
Authors: Ashwood‐Smith M. J. , Ceska O. , Warrington P. J. 
Published: January 2008

Abstract—Pure isopimpinellin is photobiologically inactive. Samples of isopimpinellin obtained by extraction of plants often contain small amounts of the active furocoumarin, 5‐methoxypsoralen, as an impurity. Thus the conflicting accounts of the photobiological activity of isopimpinellin are probably related to this impurity.
COTTON SEEDLING MORPHOGENIC RESPONSES TO FR/R RATIO REFLECTED FROM DIFFERENT COLORED SOILS AND SOIL COVERS
Authors: Kasperbauer Michael J. , Hunt Patrick G. 
Published: January 2008

Abstract—Cotton (Gossypium hirsutumL.) seedlings were morphologically responsive to red (R) and far‐red (FR) light (low and high FR/R photon ratios, respectively) from time of emergence. Controlled environment R and FR treatments confirmed phytochrome involvement in biomass allocation among new leaf, stem and root growth. Seedlings that received the high FR/R photon ratio developed longer and heavier stems, leaves with lower specific weights, less massive roots and higher shoot/root biomass ratios. Other cotton seedlings were grown in sunlight over different colored soils or painted panels to measure morphological effects of FR/R photon ratio in upwardly reflected light. Morphological responses to a given FR/R ratio were the same whether the reflection was from natural soil or from a painted surface. Seedlings that received the higher FR/R photon ratios in upwardly reflected light developed longer stems, leaves with lower specific weights, less massive roots and higher shoot/root biomass ratios. The potential use of colored mulches in agriculture was discussed.
AMELIORATION OF UV‐B DAMAGE UNDER HIGH IRRADIANCE. I: ROLE OF PHOTOSYNTHESIS
Authors: Adamse Paulien , Britz Steven J. 
Published: January 2008

Abstract—Sensitivity to ultraviolet‐B radiation (UV‐B,280–315 nm) is generally reduced when background irradiance is high. We tested the involvement of photosynthesis in the amelioration of UV‐B damage by treating plants at high PAR (photosynthetically‐active radiation, 400–700 nm; 1000 μmol m‐2 s‐1) with supplemental UV‐B at double ambient levels of biologically‐effective radiation (18 kJ m‐2d‐1) and either “ambient” (450 μmol mol‐1) or short term elevated (750 μmol mol‐1) CO2 levels. Responses to UV‐B were assessed by photosynthetic gas exchange, leaf expansion and production of UV‐absorbing compounds (presumptive flavonoids) in cultivars of cucumber (Cucumis sativus L.) previously demonstrated to be relatively sensitive (cv. Poinsett) and insensitive (cv. Ashley) to UV‐B. Except for marginal leaf interveinal chlorosis observed in Poinsett, both cultivars responded similarly. UV‐B had little direct effect on leaf photosynthesis, but it did cause reductions in leaf area and corresponding increases in leaf dry matter per area. Increased CO, stimulated plant growth, counteracting the effect of UV‐B on leaf growth and indicating an important role for photosynthesis. In contrast, the accumulation of UV‐absorbing flavonoid compounds was enhanced by UV‐B exposure but was not affected by COz enrichment.
PHYTOCHROME EVOLUTION: A PHYLOGENETIC TREE WITH THE FIRST COMPLETE SEQUENCE OF PHYTOCHROME FROM A CRYPTOGAMIC PLANT: (Selaginella martensii SPRING)
Authors: Hanelt Sabine , Braun Birgit , Marx Stefan , Schneider‐Poetsch Hansjörg A. W. 
Published: January 2008

Abstract—We have sequenced cDNA and genomic clones coding for phytochrome of the fern Selaginella. On the amino acid level, this phytochrome shares sequence homologies with phytochromes of higher plants which range between 62 (phytochrome E of Arabidopsis) and 55 (56)% [phytochrome C of Arabidopsis (Avena)]. Introns in the Selaginella gene are short and occupy positions known from phytochrome sequences of higher plants. A rooted phylogenetic tree based on mutation distances puts Seluginella phytochrome closest to the hypothetical ancestor. A similar tree arises if the tree is constructed with partial sequences (about 200 amino acids) around the chromophore attachment site. An extension of this tree by sequences of other cryptogamic plants (Mougeotia, Ceratodon, Psilotum) shows all these sequences including those of the phytochromes B and C of Arabidopsis on a branch, well separated from the branch formed by phytochromes known to accumulate in etiolated plants. The rooted phytochrome phylogenetic tree, however, is difficult to reconcile with the fossil record.
SIGNAL TRANSDUCTION BY PHYTOCHROME: PHYTOCHROMES HAVE A MODULE RELATED TO THE TRANSMITTER MODULES OF BACTERIAL SENSOR PROTEINS
Authors: Schneider‐Poetsch Hansjörg A. W. 
Published: January 2008

Abstract—A C‐terminal section of phytochromes turned out to share sequence homologies with the full length of the transmitter modules (about 250 amino acids) of bacterial sensor proteins. Coinciding hydrophobic clusters within the homologous domains imply that the overall folding of the two different types of peptides is similar. Hence, phytochromes appear to possess the structural prerequisites to transmit signals in a way bacterial sensor proteins do. The bacterial sensor proteins are known to be environmental stimuli‐regulated kinases belonging to two‐component systems. After sensing a stimulus by the N‐terminal part of the sensor protein, conformational alterations confer the signal to its (mostly) C‐terminal transmitter module which in turn is transitionally autophosphorylated at a conserved histidine. From the histidine the phosphate is transferred to the receiver module of a system‐specific regulator protein which eventually acts on transcription or enzyme activity. The histidine is not conserved in phytochromes. Instead, a conserved tyrosine is found spatially very close to the histidine position. This tyrosine might play the role of histidine, and kinase function might be associated with this part of phytochrome. In spite of this divergence, the structural similarities point to a common evolutionary origin of the phytochrome and bacterial modules.
SPECTRAL INHOMOGENEITY OF THE LIGHT‐HARVESTING ANTENNA OF Rhodospirillum rubrum PROBED BY TRIPLET‐MINUS‐SINGLET SPECTROSCOPY AND SINGLET‐TRIPLET ANNIHILATION AT LOW TEMPERATURES
Authors: Mourik Frank van , Visscher Kees J. , Mulder Jan M. , Grondelle Rienk van 
Published: January 2008

Abstract–Triplet‐minus‐singlet (T‐S) spectra and singlet‐triplet annihilation was measured on Rhodospirillum rub‐rum chromatophores at low temperatures (4–77K). The T‐S spectrum of the LH‐1 antenna was dependent on the wavelength of excitation and thus indicative of site‐inhomogeneous broadening. The data cannot be understood adequately using the two pigment pool model (B880 + B896) but, in contrast, support a model for LH‐1, in which the spectral properties are determined by site‐inhomogeneous broadening. Consequently, the 4 K antenna domain for singlet‐triplet annihilation in LH‐1 is rather small. If the temperature is raised to 77 K the annihilation domain increases, and a fit of the fluorescence quenching and triplet yield data suggests that at 77 K the connectivity is between the extreme cases of the “lake” and the isolated “puddles” models. The implications of the observed antenna inhomogeneity on low temperature annihilation and fluorescence measurements are discussed.
COHERENT MOTION AND TRANSFER OF EXCITATION ENERGY IN THE PRIMARY PROCESSES OF PHOTOSYNTHESIS
Authors: Klevanik Alexander , Renger Gernot 
Published: January 2008

AbstractFluorescence decay curves are calculated within the framework of the Liouville von Neumann equation for simple model systems of a photosynthetic unit consisting of a reaction center coupled to either a linear chain or a hexagonal array of identical antenna pigments. A comparison of the results with those obtained by solving the Pauli Master equations reveals that in the case of coherent excitation energy transfer the fluorescence decay kinetics exhibit a strong dependence on the topological array of the antenna pigments. For systems with a different pigment array, markedly different kinetics can be expected upon decreasing the pure dephasing time.
REVERSIBLE PHOTOCHEMISTRY IN THE α‐SUBUNIT OF PHYCOERYTHROCYANIN: CHARACTERIZATION OF CHROMOPHORE AND PROTEIN BY MOLECULAR DYNAMICS AND QUANTUM CHEMICAL CALCULATIONS
Authors: Scharnagl C. , Fischer S. F. 
Published: January 2008

AbstractThe ground and excited state properties of two regions in the Δ15‐configurational space of the phycoviolobilin chromophore in the α‐subunit of phycoerythrocyanin are analyzed. Molecular dynamics calculations reveal that the chromophore geometry determines the active‐site dynamics. The excited state torsional potential surface shows a negative barrier for isomerization and trapping of an activated complex. Strong coupling of excited states localized in the chromophore and charge transfer states from the surrounding polar residues provides favorable prerequisites for fast excited state surface crossing in competition with other deactivation processes. The formation of a photoreduced intermediate following the photoinduced charge transfer may trigger subsequent chemical reactions.
AQUEOUS AGGREGATES OF BACTERIOCHLOROPHYLL c AS A MODEL FOR PIGMENT ORGANIZATION IN CHLOROSOMES
Authors: Miller Mette , Gillbro Tomas , Olson John M. 
Published: January 2008

AbstractChlorosomes isolated from Chloroflexus aurantiacus were extracted with chloroform/methanol. The extract contained bacteriochlorophylls c and a and lipids, but was devoid of proteins. This crude extract spontaneously formed aggregates when a methanol solution was dispersed in aqueous buffer.The aggregates could be sedimented by ultracentrifugation and appeared in electron micrographs as stain‐excluding bodies with diameters between 70 and 170 nm. The absorption spectrum is remarkably similar to that of intact chlorosomes with an absorption maximum of bacteriochlorophyll c at around 740 nm. The circular dichroism spectrum of the aggregate is also very similar to that of intact chlorosomes. A conservative (±) band centered at 740 nm confirms the highly aggregated state of bacteriochlorophyll c in both systems.Steady‐state fluorescence studies showed that in the aggregate energy‐transfer from bacteriochlorophyll c to a component emitting at 830 nm took place. When the aggregate was suspended in buffer saturated with 1‐hexanol the 740 nm form of bacteriochlorophyll c was reversibly converted to a form with spectral properties resembling the monomer absorbing at 670 nm but still in an aggregated state. This form of bacteriochlorophyll c showed no circular dichroism signal.
TEMPERATURE DEPENDENCE OF PICOSECOND FLUORESCENCE KINETICS OF A CYANOBACTERIAL PHOTOSYSTEM I PARTICLE*
Authors: Turconi Sandra , Schweitzer Gerd , Holzwarth Alfred R. 
Published: January 2008

AbstractPicosecond time‐resolved fluorescence of photosystem I particles isolated fromSynechococcussp. was recorded in the wavelength range from 680 nm to 736 nm for temperatures of 6°C to 42°C and ‐ 100°C using the single‐photon‐timing technique. By global analysisofthe data we found four contributing lifetime components at the higher temperatures (T1' 12 ps,T1= 35 ps,T3' 65 ps,T4' 1000 ps). We attributeT1to an energy transfer between two pigment pools,T2to the charge separation process in the reaction center, componentT3is assigned to aggregate andT4to uncoupled chlorophyll emission. The corresponding decay‐associated spectra are presented. We also applied a target analysis procedure to fit parameters of a kinetic model directly to the data. The resulting rate constants and species‐associated spectra are discussed. The data indicate substantial spectral heterogeneity in the antenna with at least three substantially different chlorophyll pools. The overall exciton decay kinetics (by charge separation) is trap‐limited.
OPTICAL PROPERTIES OF EXPERIMENTAL PROSTATE TUMORS in vivo
Authors: Arnfield M. R. , Chapman J. D. , Tulip J. , Fenning M. C. , McPhee M. S. 
Published: January 2008

AbstractThe optical properties of tumor tissue provide important information for optimizing treatment plans in photodynamic therapy, especially when intertitial application by multiple fibers is planned. Near infrared light, required to activate novel photosensitizers, should facilitate improved light penetrance of tumor tissue compared with 630 nm light used for activating Photofrin II. We have measured light energy fluence rates for 630 and 789 nm light along radial tracks from a single laterally diffusing optical fiber centrally implanted into Dunning R3327‐AT and R3327‐H rat tracks from a single laterally diffusing optical fiber centrally implanted into Dunning R3327‐AT and R3327‐H rat prostate tumors in anesthetized rats. A total of 20 R3327‐AT and 10 R3327‐H tumors were used in this study with volumes from 2.6 to 13.3 cm3. Light track data were analyzed by an empirical model that described light attenuation. At 630 nm, light attenuation coefficients (LAC) were T1.9 × higher than those at 789 nm for both tumors with the well‐differentiated, well‐perfused tumor (R3327‐H) attenuating to a greater extent than did the rapidly growing anaplastic tumor (R3327‐AT). The intertumor variation of LAC was greater than the spatial variations observed within individual tumors. LAC were a function of tumor volume for only 630 nm light in the R3327‐AT tumors.
IS ZEAXANTHIN CAPABLE OF ENERGY TRANSFER TO CHLOROPHYLL a IN PARTIALLY GREENED LEAVES? A STUDY OF FLUORESCENCE EXCITATION SPECTRA DURING VIOLAXANTHIN DEEPOXIDATION
Authors: Pfündel Erhard E. 
Published: January 2008

AbstractAbsorbance spectra and excitation spectra of chlorophyll a fluoresence were recorded during the light‐induced deepoxidation of violaxauthin to zeaxanthin in bean leaves (Phaseolus coccineus) greened under intermittent light. Light minus dark fluorescence excitation difference spectra showed distinct minima at 440, 465, and 500 nm corresponding to maxima in the absorbance difference spectra. Both difference spectra were prevented by the deepoxidase inhibitor dithiothreitol and were inverted when zeaxanthin was epoxidized. The fluorescence excitation difference spectra were successfully modeled by considering the absorbance differences between violaxanthin and zeaxanthin, assuming no energy transfer from the two pigments to chlorophyll a, and accounting for light‐induced scattering changes. The pigment stoichiometry and the scattering changes of the simulation were in accordance with experimental data. The results indicate that, in the early stage of leaf development, light absorbed by the cycle pigments violaxanthin and zeaxanthin is not transferred to chlorophyll.