bluuebunny/crossref_metadata_2025_split huggingface dataset:
EXCITED‐STATE PROPERTIES OF THE ALTERNATING POLYNUCLEOTIDE POLY(dA‐dT)POLY(dA‐dT)
Authors: Ge G. , Georghiou S. 
Published: January 2008

ReferencesMeasurements of the steady‐state fluorescence spectrum and anisotropy, r, of the alternating polynucleotide poly(dA‐dT)‐poly(dA‐dT) were carried out in order to characterize its photophysical properties at room temperature. The shape of the fluorescence spectrum depends on the excitation wavelength, namely, the relative fluorescence intensity of the short‐wavelength peak decreases for excitation at short wavelengths. When monitoring the emission at short wavelengths, r is 0.18 and independent of the excitation wavelength. When monitoring the emission at long wavelengths, however, r is very low, about 0.03. These results suggest that: (i) the short‐wavelength emission stems from thymine; and (ii) the long‐wavelength emission stems from an excited‐state complex (excimer), with the same one being formed regardless of whether thymine or adenine is excited. The corresponding fluorescence spectra have been resolved. The occurrence of transfer of electronic energy is discussed.
NON‐DIMER DNA DAMAGE IN CHINESE HAMSTER V‐79 CELLS EXPOSED TO ULTRAVIOLET‐B LIGHT
Authors: Matsumoto Kumi , Sugiyama Masayasu , Ogura Ryohei 
Published: January 2008

Abstract—To understand and characterize non‐dimer DNA damage and cytotoxicity induced by ultraviolet‐B light (UV‐B,290–320 nm), an alkaline elution technique for analysis of DNA damage was used on Chinese hamster V‐79 cells. Ultraviolet‐B exposure produced a dose‐dependent induction of DNA single strand breaks and DNA‐protein crosslinks; however, there was an absence of DNA‐DNA interstrand crosslinks. Neither of these types of DNA damage were repaired within a 24 h incubation of the cells following a single UV‐B exposure; rather the damage increased. Using a colony forming assay, we found that UV‐B exposure resulted in an increase of cytotoxicity in a dose‐dependent fashion. In addition, UV‐B exposure inhibited DNA and RNA synthesis. The role of non‐dimer DNA damage in the cytotoxicity induced by UV‐B is discussed.
LATITUDINAL AND SEASONAL VARIATION IN CALCULATED ULTRAVIOLET‐B IRRADIANCE FOR RICE‐GROWING REGIONS OF ASIA*
Authors: Bachelet D. , Barnes P. W. , Brown D. , Brown M. 
Published: January 2008

AbstractUltraviolet‐B (UV‐B,280–320 nm) irradiance was calculated for more than 1200 sites in Asia to characterize the spatial and temporal variation in the present UV‐B climate for rice‐growing regions. The analytical model of Green et al. (Photochem. Photobiol.31,59–65, 1980) was used to compute UV‐B irradiance for clear skies using satellite‐observed ozone column thickness and local elevation data. Ground‐based observations of cloud cover were then used to approximate the average effect of cloud cover on UV‐B irradiance using the approach of Johnson et al. (Photochem. Photobiol.23,179–188, 1976). Over the geographic range of rice cultivation, the maximum daily effective UV‐B irradiance (UV‐BBE), when weighted according to a general plant action spectrum, was found to vary approx. 2.5‐fold under both clear and cloudy sky conditions. Under clear skies, the timing of maximum solar UV‐BBE changed with latitude and varied from February‐March near the equator to July‐August at temperate locations. Cloud cover was found to alter the season of maximum UV‐BBE in many tropical regions, due to the pronounced monsoonal climate, but had little effect on UV‐B seasonality at higher latitudes. Under a climate resulting from a doubling of atmospheric carbon dioxide, estimated UV‐B using predicted cloud cover was found to change by up to 17% from present conditions in Thailand. Both latitudinal and seasonal variation in solar UV‐B radiation may be important aspects of the UV‐B climate for rice as cultivars differ in sensitivity to UV‐B and are grown under diverse conditions and locations.
CHARACTERIZATION OF THE (6‐4) PHOTOPRODUCT OF 2′‐DEOXYCYTIDYLYL‐(3′‐>5′)‐THYMIDINE AND OF ITS DEWAR VALENCE ISOMER
Authors: DOUKI T. , VOITURIEZ L. , CADET J. 
Published: January 2008

Abstract—Far‐UV irradiation of dCpT in aqueous solution was found to generate the corresponding pyrimidine (6‐4) pyrimidone photoadduct and the related Dewar valence isomer. The two photoproducts of dCpT were found to undergo deamination in aqueous solution, giving rise to the corresponding dUpT derivatives at a relatively slow rate. It was also shown that the Dewar isomer is much more alkali‐labile than its (6‐4) precursor.
PHOTOSENSITIZATION BY SYNTHETIC DIPORPHYRINS AND DICHLORINS in vivo AND in vitro
Authors: KESSEL DAVID , DOUGHERTY T. J. , CHANG C. K. 
Published: January 2008

Abstract—A group of polycarboxylic diporphyrins, two dichlorins and a porphyrin‐chlorin dimer, with rings linked by methylene groups, were examined to help identify structures which can mediate photodynamic tumor eradication in vivo. Among the features sought were short persistence of normal tissue photosensitization and substantial absorbance at wavelengths longer than 630 nm. Both objectives were achieved, with pertinent structure‐activity relationships partly characterized. The relative hydrophobicity of the different sensitizers was an important determinant of their accumulation in cell culture, but not of in vivo effectiveness. These compounds showed affinity for protein and high‐density lipoprotein components of serum. Their distribution may be mediated by a different mechanism than that which occurs with more hydrophobic sensitizers like hematoporphyrin derivative which have greater affinity for low‐density lipoproteins and less for protein components of serum, as compared with the products examined in this study.
DO PYRIMIDINE DIMER YIELDS CORRELATE WITH ERYTHEMA INDUCTION IN HUMAN SKIN IRRADIATED in situ WITH ULTRAVIOLET LIGHT (275–365 nm)?
Authors: HACHAM H. , FREEMAN S. E. , GANGE R. W. , MAYTUM D. J. , SUTHERLAND J. C. , SUTHERLAND B. M. 
Published: January 2008

Abstract—Ultraviolet radiation produces erythema in human skin, and damages the DNA of living cells in skin. Previous work showed that broad‐band UV‐B (290–320 nm) radiation produced higher levels of cyclobutyl pyrimidine dimers in DNA of individuals with high UV‐B sensitivity (low minimal erythema dose) than in subjects of low UV‐B sensitivity [Freeman et al. (1986) J. Invest. Dermatol., 86, 34–36]. We examined the relationship between erythema induction and dimer yields in DNA of human skin irradiated in situ with narrow band radiation spanning the wavelength range 275–365 nm. We find that, in general, higher dimer yields are produced per incident photon in volunteers with higher susceptibility to erythema induced by radiation of the same wavelength.
ANALYSIS OF PHOTO‐OXIDIZED AMINO ACIDS IN TRYPTIC PEPTIDES OF CALF LENS γ‐II CRYSTALLIN
Authors: Hott J. L. , Borkman R. F. 
Published: January 2008

Abstract—Insoluble and crosslinked proteins and increased pigmentation in the eye lens are features of aging and cataracts. Determining the amino acids which are involved in insolubilization, crosslinking and visible light scattering will shed light on the mechanisms by which cataracts form. Calf lens γ‐II crystallin was irradiated at 295 nm, digested and separated into tryptic peptides. Additional tryptic peptides were found in the digest of irradiated γ‐II which were not present in the dark control digest. These peptides were identified by amino acid sequencing and shown to correspond to expected tryptic fragments of the protein, indicating more facile digestion in the UV‐irradiated protein than in dark controls. Amino acid analysis of the irradiated protein and peptides showed losses of histidine. methionine and cysteine residues as compared to control samples. Tryptophan, which is not detected by amino acid analysis, was also found to be reactive since losses in its fluorescence intensity were observed after irradiation. Some of the photochemically active amino acids had lower than expected responses in amino acid sequencing experiments. This suggested specific sites of photochemical activity in the various peptides. The evidence for peptide crosslinks is also discussed.
INDUCTION OF A TRANSIENT ENHANCEMENT OF LOW LEVEL CHEMILUMINESCENCE IN INTACT LEAVES BY ANAEROBIC TREATMENT
Authors: Roschger P. , Devaraj B. , Scott R. Q. , Inaba H. 
Published: January 2008

Abstract—Intrinsic low level chemiluminescence of dark adapted intact leaves exhibits a transient enhancement of light emission when ambient air is replaced with an anaerobic atmosphere. Re establishing aerobic conditions gives rise to a complex kinetic behavior of the light emission in the post‐anoxic phase. Metabolic changes within the leaf are suggested to be responsible for this phenom enon, where intactness of the leaf is found to be of crucial importance. Leaf homogenate showed nearly oxygen independent chemiluminescence. In contrast, low level chemiluminescence of UV‐light damaged leaves and of chloroplast preparations was inhibited by oxygen depletion. Spectral analyses of the ultraweak light emission from the intact leaf indicates that in both aerobic and anaerobic cases, the source of the ultraweak light is the same. The similarity to the spectrum of delayed fluorescence also obtained from the leaf suggests that chlorophyll is the light emitting species.
In vivo EXPOSURE TO ULTRAVIOLET RADIATION ENHANCES PATHOGENIC EFFECTS OF MURINE LEUKEMIA VIRUS, LP‐BMS, IN MURINE ACQUIRED IMMUNODEFICIENCY SYNDROME
Authors: Brotek Celestyn M. , Shopp George M. , Ryan Sharon L , Gillespie Patricia M. , Kusewitt Donna F. , Rajagopalan M. S. , Ley Kenneth D. , Ley Ronald D. 
Published: January 2008

Abstract—LP‐BM5 murine leukemia virus (MuLV) induces an immunodeticiiency syndrome (MAIDS) in C57BL/6 mice which resembles immunological abnormalities observed in early stages of human AIDS. In our study, MAIDS virus‐infected mice were exposed to low doses of ultraviolet radiation (UVR) before and after virus inoculation and compared with MAIDS‐infected but not UVRcxposed mice. In all tested parameters (blood IgM levels; mitogenic responses to PHA. ConA, LPS and anti‐μ MLR antigenic response to SRBC, enlargement and histopathologic changes of the spleen) we observed the same trend: changes due to MAIDS infection were more pronounced in the UVR‐eposed group than in the unexposed group. Statistically significant differences between these two groups were Seen for mitogenic responses at two different time points after virus inoculation. These results demonstrate that in vivo UVR exposure enhances the immunosuppressive effects of a retroviral infection. UVR exposure may affect the progression of AIDS in a similar manner.
A MODEL FOR THE MOLECULAR STRUCTURE AND ORIENTATION OF THE CHROMOPHORE IN A DIMERIC PHYTOCHROME MOLECULE*
Authors: Tokutomi Satoru , Sugimoto Tohru , Mimuro Mamoru 
Published: January 2008

Abstract—A model for the molecular structure and orientation of red‐light absorbing form of phytochrome (P,) chromophores in a dimeric molecular model of Pr is proposed. A chromophore model with probable molecular structures was generated to reproduce the absorption spectrum produced by its π‐electron conjugating system. The model has C5‐Z, syn, C10‐E, anti and C15‐Z, syn configurations and a protonation at a C‐ring nitrogen. Orientation of the chromophore model in the dimeric phytochrome molecular was analyzed by displaying the atoms of the chromophore, the coordinates of which were converted into those with respect to the molecular axes to the dimeric molecule, on a 3‐D graphic workstation. The conversions were performed by using the azimuthal angles between the Z axis of the dimeric molecule (axis of 2‐fold rotational symmetry) and the dipole moments of the electronic transition at the blue‐ (384 nm) and red‐ (667 nm) absorbing bands of the chromophore, which were calculated as 55.5° and 59.3°, respectively, based on linear dichroism of the oriented phytochrome molecules. The result demonstrates that the long axis of the P, chromophore lies almost parallel to the Y axis of the molecular model, and that the tetrapyrrolic chromophore is well contained within the flat chromophoric domain without protruding from it, a configuration that assures that the chromophore is protected against aqueous environments. The model may explain the rotation angle of the transition moment of the red‐absorbing band, induced by the phototransformation from Pr to Prr which we measured as smaller than that measured in nonoriented preparations by a photoselection technique. The model also suggests a molecular basis for the polarotropic response of phytochrome.
In vivoPHYTOCHROME‐MEDIATED PERCEPTION OF REFLECTED LIGHT SIGNALS
Authors: Mancinelli Alberto L. , Hobert Oliver , Nikas George 
Published: January 2008

Abstract—The spectrophotometric assay of phytochromein vivoin etiolated plant material was used to determine the effects of changes in reflected light on the state of the photoreceptor in etiolated seedlings exposed simultaneously to direct and reflected light. Changes in reflected light that were small in terms of the total (direct + reflected) radiation incident on the seedlings produced detectable changes in the state of phytochromein vivo. The contribution of reflected light to the state of phytochrome in vertical organs was greater than expected from its low contribution to total incident light. These data from laboratory studies complement and are consistent with results of field studies on the effects of light reflected from neighboring vegetation on plant growth under natural radiation conditions.
PHYTOCHROME PHOTOCONVERSIONin vivo. EFFECT OF THE INITIAL Pfr/Ptot RATIO
Authors: Mancinelli Alberto L. , Rossr Federica , Moroni Anna 
Published: January 2008

Abstract—The equation for phytochrome photoconversion, derived from photoconversion kinetics of purified phytochrome, predicts that the rates of photoconversions starting from low and high Pfr/Ptot(0), (initial Pfr/Ptot) should be the same for light of the same quality and fluence rate. The situation might be differentin vivo. Phytochrome photoconversion rates were measured in excised cotyledons ofCucurbita pepoL. exposed to BL (blue; ϕBL= 0.39; ϕ, Pfr/Ptot at photoequilibrium) and RI (mixture of red and far red; ϕRI= 0.46) after saturating preirradiations with red and far‐red to establish high (0.78) and low (0.02) Pfr/Ptot(0), respectively. Under BL, the rate of photoconversion is faster when starting from a high than a low Pfr/Ptot(0); under RI, the rate of photoconversion is faster when starting from a low than a high Pfr/Ptot(0)., No effects of Pfr/Ptot(0), on photoconversion rates were found in phytochrome solutions exposed to BL and RI. These data provide another indication of the discrepancies between phytochrome photconversion kineticsin vivoandin vitro.
NITRATE EFFECT ON Pfr‐MEDIATED AND GA3‐INDUCED GERMINATION IN SPORES OF Anemia phyllitidis (L.) Sw*
Authors: Haas Christian J. , Kopp Hannelore , Scheruerlein Robert 
Published: January 2008

Abstract—Spore germination in Anemia phyllitidis can be induced by red light (R) via the phytochrome system and by gibberellic acid (GA3) in the dark. An enhancing effect of NO3‐ions on the Pfr‐mediated germination could be demonstrated. This NO3‐effect was found to be pronounced during the preinduction phase and could be described by biphasic kinetics depending on the formation of Pfr by the R‐irradiation. Besides NO3, other electron accepting substances also increased germination significantly. In contrast to Pfr‐mediated germination, no enhancing effect by NO3 could be obtained for the GA3‐induced germination response. The application of an inhibitor of gibberellic acid synthesis, AMO1618, as well as the analysis of combined R and GA3 treatment, support the hypothesis that for germination of Anemia phyllitidis spores no synergism between the factors exists. Thus, it is proposed that the gibberellic acid receptor starts a signal‐transduction pathway resulting in germination which is in part independent of the Pfr‐mediated signal‐transduction chain. The NO3‐effect is specific for the Pfr‐mediated signal‐transduction chain.
PHYTOCHROME REGULATION OF MORPHOGENESIS IN GREEN PLANTS: FROM THE BELTSVILLE SPECTROGRAPH TO COLORED MULCH IN THE FIELD*
Authors: Kasperbauer Michael J. 
Published: January 2008

Abstract—Development of the theory and use of photon ratios reflected from colored mulches to regulate plant morphogenesis in the field utilized information obtained on the Beltsville Spectrograph, in controlled environments and in field plant spacing studies. An upwardly reflected far‐red to red (FR/R) ratio higher than the ratio in incoming sunlight resulted in larger shoots and a higher shoot/root biomass ratio. A reflected FR/R ratio lower than the ratio in incoming sunlight resulted in larger roots and a lower shoot/root biomass ratio.
WAVELENGTH DEPENDENCE OF PHOTOINDUCED PEROXIDATION AND CYTOTOXICITY OF HUMAN LOW DENSITY LIPOPROTEINS
Authors: Nègre‐Salvayre Anne , Paillous Nicole , Dousset Nicole , Bascoul Jacques , Salvayre Robert 
Published: January 2008

Abstract— The relative abilities of UV‐A, B and C radiations to initiate lipid peroxidation and apolipoprotein (apo) B modification of human purified low density lipoproteins have been compared. Ultraviolet‐B and C (at 310 and 254 nm, respectively) exhibited similar efficacy as shown by the increase in lipid peroxidation markers (conjugated dienes, thiobarbituric acid reactive substances and fluorescent lipid soluble products) and in oxysterols, as well as by the decrease of the contents of natural antioxidants (tocopherols and carotenes) and in polyunsaturated fatty acids. In contrast, UV‐A (at 360 nm) was found poorly effective and only at very high radiation intensities. Under all the conditions used, apoB was not affected by the UV radiations as shown by the stability of amino acid composition (except tryptophan level) and of trinitrobenzenesulfonic acid reactive amino group content. Similarly, the low density lipoprotein size was not altered. By comparison, low density lipoproteins oxidized by transition metal presented strong alterations of apoB and major changes of the apparent low density lipoprotein size.Finally, low density lipoproteins irradiated by UV‐B or C exhibited a much higher cytotoxicity on cultured cells than those irradiated by UV‐A. Under the conditions used in this paper, the cytotoxic effect of the irradiated low density lipoproteins was positively correlated with their content in lipid peroxidation products and inversely correlated with their tocopherol content.
THE INFLUENCE OF FLUORESCENCE CONCENTRATION QUENCHING ON THE EMISSION ANISOTROPY OF FLAVINS IN GLYCERINE‐WATER SOLUTIONS
Authors: Grajek H. , Bojarski C. , Zurkowska G. , Drabent R. 
Published: January 2008

Abstract— The measurements of the emission anisotropy r/r0 of flavomononucleotide (FMN) within a range of concentrations of 10–5–10‐1mol/L in glycerine‐water solutions of different viscosities‐0.056 Pa/s (system I) and 0.256 Pa/s (system II) have been carried out.In the range of high concentrations the repolarization effect due to the sharp drop of the quantum yield has been observed.The experimental results have been compared with theoretical expressions evaluated by taking into account both concentration and rotation depolarization. A good agreement on the values of the theoretical parameters obtained from independent measurements has been found.It has been stated that in the investigated systems the excitation energy transfer may be treated as a Markov process.
LIFETIMES OF BACTERIOCHLOROPHYLL FLUORESCENCE IN Rhodopseudomonas viridis AND Heliobacterium chlorum AT LOW TEMPERATURES
Authors: Kleinherenbrink F. A. M. , Cheng P. , Amesz J. , Blankenship R. E. 
Published: January 2008

AbstractFluorescence lifetimes of isolated membranes of Rhodopseudomonas viridis were measured in the temperature range of 77 K to 25 K. At room temperature, the main component of the fluorescence decay of bacteriochloro‐phyll (BChl) b had a time constant of 50 ps. In contrast to other purple bacteria, the emission at low temperature was spectrally homogeneous and showed essentially single lifetimes of 140 ps at 77 K and 180 ps at 25 K, with the primary electron donor in the oxidized state. Taking into account the relative fluorescence yields with open and closed reaction centers, we arrive at numbers of 125 ps and 215 ps, respectively, for open reaction centers. These numbers are significantly smaller than expected on the basis of measurements of the efficiency of charge separation, perhaps suggesting that the excitation decay in the absence of reaction centers is considerably faster at low temperature than at room temperature. At least four different spectral components with different lifetimes were observed at 25 K in the emission of Heliobacterium chlorum, a short‐wavelength component of about 30 ps and three longer‐wavelength components of about 100 ps, 300 ps, and 900 ps. This indicates a strong heterogeneity in the emitting pigment, BChl g‐808. The component with the shortest lifetime does not appear to be affected by the redox state of the reaction center and might reflect energy transfer to BChl g species which are connected to the reaction center.
THE MAJOR INTRINSIC LIGHT‐HARVESTING PROTEIN OF Amphidinium: CHARACTERIZATION AND RELATION TO OTHER LIGHT‐HARVESTING PROTEINS
Authors: Hiller Roger G. , Wrench Pamela M. , Gooley Andrew P. , Shoebridge Grant , Breton Jacques 
Published: January 2008

AbstractA major light‐harvesting complex (LHC) has been obtained from thylakoids of Amphidinium carterae solubilized with digitonin or decylmaltoside and separated by sucrose‐gradient centrifugation. The digitonin‐LHC forms a dark brown band at ‐17% sucrose and the decylmaltoside LHC one at ‐7% sucrose. Excellent energy transfer is retained from chlorophyll c and carotenoid to chlorophyll a. Absorbance and fluorescence excitation spectra show the existence of two major forms of chlorophyll c, one absorbing at 634 nm and the other at 649 nm. Linear dichroism spectra show the Qy transition of both forms of chlorophyll c to be aligned at <35° to the membrane plane. On sodium dodecylsulfate polyacrylamide gels the complex resolves as a single band of 19 kDa. A partial amino acid sequence shows the N‐terminus to be unblocked but modified; there is a persistent ambiguity of Ser/Asn at residue 4 and evidence for multiple but very similar polypeptides within the 19 kDa band. The peptide has strong identity with the N‐terminal regions of LHC from Phaeodactylum and Pavlova and LHC 1 of higher plants. Antibodies to the 19 kDa peptide react weakly with LHC of brown algae, diatoms and Prymnesiophytes but not with those of higher plants or Cryptophytes.
STRUCTURAL RELATIONSHIPS OF THE PHOTOSYSTEM I AND PHOTOSYSTEM II CHLOROPHYLL a/b AND a/c LIGHT‐HARVESTING APOPROTEINS OF PLANTS AND ALGAE
Authors: Plumley F. Gerald , Martinson Tracey A. , Herrin David L. , Ikeuchi Masahiko , Schmidt Gregory W. 
Published: January 2008

AbstractPolyclonal antibodies against four different apoproteins of either the chlorophyll (Chl) a/b light‐harvesting antenna of photosystem I or II, or a chlorophyll‐protein complex homologous to CP26 from Chlamydomonas reinhardtii, crossreact with11–13 thylakoid proteins of Chlamydomonas, Euglena gracilis and higher plants. The number of antigenically‐related proteins correlates with the quantity of light‐harvesting chlorophyll‐protein complex (LHC) gene types that have been sequenced in higher plants. The antibodies also react specifically with Chi a/c‐binding proteins of three diatoms and Coccolithophora sp. as determined by immunoblot and Ouchterlony assays. Four to six crossreacting proteins are observed in each chromophyte species and a functional role for some can be deduced by antibody reactivity. It appears that despite major differences in the structures of their pigment ligands, at least some domains of Chl‐binding LHC apoproteins have been conserved during their evolution, possibly functioning in protein: protein, as opposed to pigment: protein, interactions in photosynthetic membranes.