bluuebunny/crossref_metadata_2025 huggingface dataset:
THE EFFECT OF SYSTEMIC CYCLOSPORIN A ON A HAIRLESS MOUSE MODEL OF PHOTOAGING
Authors: Moloney Stephen J. , Learn Douglas B.
Published: January 2008

Abstract—

The mechanisms that cause skin wrinkling in response to chronic exposure to sunlight are unknown. We investigated the possibility that wrinkling of Skh‐1 hairless mice is associated with an ultraviolet (UV) radiation‐induced immunologic alteration. Exposing Skh‐1 hairless mice to a regimen of nonerythemal UV‐B (290–320 nm) radiation induced skin wrinkles after 6–7 weeks. Concomitant treatment with cyclosporin A decreased the time to the onset of wrinkles to approximately 4 weeks. Exposing HRS/J hairless mice or athymic nude mice to a similar nonerythemal UV‐B radiation regimen for 10 weeks failed to induce skin wrinkles. Concomitant administration of cyclosporin A and UV‐B radiation for 7 weeks to HRS/J hairless mice induced no skin wrinkles. Ultraviolet‐B or UV‐B plus cyclosporin A exposure caused increased immunohistochemical staining for Ia and F4/80 antigens in the upper dermis of tissue from Skh‐1 mice, as compared to controls. Treating Skh‐1 mice with UV‐B radiation plus cyclosporin A was also associated with a large increase in the number of CD3+ cells in the dermis. These staining patterns were absent in similarly treated HRS/J hairless mice. Dermal mast cell numbers in Skh‐1 mice were 2–3‐fold higher than in HRS/J, athymic nude or NSA mice. Treatment with cyclosporin A increased Skh‐1 dermal mast cell numbers approximately 2‐fold but had no effect on the dermal mast cell numbers in HRS/J or NSA mice. Based on these findings we postulate that UV‐B light and cyclosporin A exacerbate an immunological condition in Skh‐1 mice, one consequence of which is manifested as skin wrinkles. Thus, the induction of skin wrinkles in this mouse strain may have no relevance to the wrinkles observed in human skin after chronic exposure to sunlight.
THE EFFECT OF LIGHT QUALITY IN Prunus cerasus. I. PHOTORECEPTORS INVOLVED IN INTERNODE ELONGATION AND LEAF EXPANSION IN JUVENILE PLANTS
Authors: Baraldi R. , Cristoferi G. , Facini O. , Lercari B.
Published: January 2008

Abstract—

Evidence is presented to suggest that stem elongation in this woody species is controlled not only by phytochrome as previously suggested for other woody species, but also by a specific blue absorbing pigment (BAP). In contrast, the BAP seems to have no role to play in the development of total leaf area in these juvenile specimens.
EFFECT OF CALCIUM ON DARK ADAPTATION IN Phycornyces PHOTOTROPISM
Authors: Sineshchekov Alexey V. , Lipson Edward D.
Published: January 2008

Abstract—

Adaptation processes enable phototropism of Phycomyces to operate over a 10‐decade range of blue‐light intensity (1 nW m−2‐10 W m‐2). To investigate the influence of calcium on dark adaptation, the phototropic latency method was employed with the modification that sporangiophores were temporarily immersed in solutions containing CaCI2 or LaCI3 Following such treatment, the time course of bending was found to have two components with distinct latencies and bending rates. After immersion in darkness for 30 min in LaCI3 solution or 1 h in a solution of CaCI2 MgCI2, or the calcium chelator EGTA, each sporangiophore was adapted to a blue light beam (1 W m‐2) for 45 min by rotation around its vertical axis. Cessation of rotation defined the onset of the phototropic stimulus, at which time the intensity was reduced by as much as 103‐fold. For a 102‐fold reduction (to 10−2 W m−2), immersion in CaCl2 (10–100 μM) reduces the latency 13 min for the early bending component and 18 min for the late component, whereas treatment with the calcium‐channel blocker lanthanum (0.1–11 μM LaCI3) increases the latency 12 min for the early component and 13 min for the late component. EGTA (10 μM) also had an inhibitory effect, increasing the latency of the first and the second components by 7 and 10 min, respectively. In experiments performed similarly, but without the light adaptation treatment after immersion, no differences between calcium‐treated and control sporangiophores were found. The bending rates of both components show only a weak dependence on calcium. Finally, experiments with MgCI2 (10–100 μM) were indistinguishable from control experiments, indicating that the divalent cation Mg+2, unlike Ca+2, had no effect on latency or bending rate. The results show that calcium affects the phototropic latency, and may function in the adaptation processes for Phycomyces phototropism.
STRUCTURAL STUDIES ON THE PHOTORECEPTOR PHYTOCHROME: REEVALUATION OF THE EPITOPE FOR MONOCLONAL ANTIBODY Z‐3B1
Authors: Bonenberger J. , Schendel R. , Schneider‐Poetsch H. A. W. , Rüdiger W.
Published: January 2008

Abstract—

The photoreceptor phytochrome is widely distributed in the plant kingdom from angiosperms to ferns, mosses and algae. The epitope for the monoclonal antibody Z‐3B1 which exhibits wide‐ranging cross‐reactivity with phytochromes from higher and lower plants was mapped by the combination of several methods: by Western blot with proteolytic fragments of known localization, by sequence comparison of phytochromes from various plants, and by production of overlapping fusion proteins. The only sequence which is common to all positively‐reacting fusion proteins is the sequence A‐830 to R‐859. This sequence must contain the Z‐3B1 epitope. The best candidate is suggested to be the T‐cell antigenic sequence K‐Y‐ V/I‐E‐A/C‐L‐L‐T (=K‐848 to T‐855). The significance of the highly conserved epitope in all phytochromes is discussed.
EXPRESSION OF OAT phyA cDNA IN THE MOSS Ceratodon purpureus
Authors: Thümmler Fritz , Schuster Harald , Bonenberger Johannes
Published: January 2008

Abstract—

The possibility of transforming Cerarodon purpureus protoplasts by PEG‐mediated direct DNA uptake was tested. Transformation with a plasmid carrying a kanamycin‐resistance gene resulted in kanamycin‐resistant colonies of C. purpureus protonemata. A full‐length cDNA clone coding for oat phyA phytochrome was isolated. The clone HM4.1 which is 3.7‐kb long exhibits about 99% nucleotide sequence identity to the known phytochrome clone AP3. The expression of HM4.1 in C. purpureus protonemata was tested. A construct with the 35s‐promotor and the structural gene of HM4.1 was cotransformed with the plasmid containing the kanamycin‐resitance. Kanamycin‐resistant colonies were tested for the presence of HM4.1 sequences in a genomic Southern experiment. Two out of 19 kanamycin‐resistant colonies reacted positively with a HM4.1 specific probe. The expression of phyA in the positive colonies was examined with monoclonal antibodies specific for oat phytochrome. The Western blot experiment with protein extracts of the two positive colonies grown in the dark revealed clear signals at 124‐kDa which were not detected in control plants. These data demonstrate the possibility of expressing oat phyA‐apoprotein in C. purpureus protonemata. The transgenic moss protonemata did not show phenotypical alterations in response to the foreign phytochrome polypeptide; it is not known at the moment if the tetrapyrole chromophore is attached to the oat polypeptide in the protonemata or not.
THE ECOLOGICAL FUNCTIONS OF THE PHYTOCHROME FAMILY. CLUES TO A TRANSGENIC PROGRAMME OF CROP IMPROVEMENT
Authors: Smith Harry
Published: January 2008

Abstract—

Phytochrome‐mediated proximity perception and induction of shade avoidance responses provide clues towards a novel genetic engineering approach for the improvement of crop plants. In this Commentary Article, I argue that the elimination, or disablement, of proximity perception and the associated shade avoidance syndrome by transgenic manipulation of phytochrome genes should provide a strategy for the creation of new crop plants in which a greater proportion of assimilates is incorporated into harvestable material. Such a programme would enable increases in agricultural productivity without a requirement for the increased application of agrochemicals. Some potential approaches towards realizing these goals are proposed.
PHOTOACTIVATION OF HYPERICIN GENERATES SINGLET OXYGEN IN MITOCHONDRIA AND INHIBITS SUCCINOXIDASE
Authors: Thomas Carin , MacGill Randall S. , Miller Glenn C. , Pardini Ronald S.
Published: January 2008

Abstract— Photosensitized inhibition of mitochondrial succinoxidase by hypericin was measured in vitro and found to be drug‐dose, light‐dose, and wavelength dependent. Singlet oxygen generation, monitored using the singlet oxygen trap tetramethylethylene, and oxygen consumption in isolated mitochondria sensitized by hypericin were also light‐dose and wavelength dependent. Unequivocal evidence for the generation of singlet oxygen was obtained using kinetic isotope ratios of products from the reaction between singlet oxygen and geminally deuterated tetramethylethylene. An action spectrum for the inhibition of succinoxidase was measured at wavelengths between 400 and 700 nm and found to parallel the recorded visible absorption spectrum of hypericin in isolated mitochondria. The greatest singlet oxygen generation, oxygen consumption, and succinoxidase inhibition occurred with white light or 600 nm irradiation. These data are consistent with a type II singlet‐oxygen‐mediated mechanism for hypericin induced photosensitized inhibition of mitochondrial succinoxidase.
CHEMIEXCITATION IN THE PEROXIDATIVE METABOLISM OF DIETHYLSTILBESTROL
Authors: Knudsen Fernanda da Silva , Cilento Giuseppe
Published: January 2008

Abstract— When the synthetic estrogen and tumourogenic compound diethylstilbestrol is exposed to horseradish peroxidase (HRP) and H2O2 in the presence of the cationic surfactant hexadecyltrimethyl‐ammonium bromide (CTAB), a burst of oxygen consumption and concomitant light emission are observed. The quinone form of the product is not seen in the absorption spectrum because CTAB strongly catalyses its conversion to Z, Z‐dienestrol. The emission spectrum shows several peaks. Total emission is dramatically enhanced by chlorophyll and by xanthene dyes. A key intermediate in chemiexcitation is 4‐hydroxypropiophenone. The ability to promote chemiexcitation is retained through various generations of metabolites, giving origin to a cascade of excited states. Since the biological effects of diethylstilbestrol appear to be connected with its peroxidative metabolism, chemiexcitation may eventually prove to be of importance in, for example, toxicity of the drug.
HOECHST 33258 PHOTOSENSITIZATION OF 5‐IODODEOXYURIDINE‐SUBSTITUTED DNA TO 365 nm LIGHT: DEPENDENCE OF DEHALOGENATION ON THE DYE‐TO‐NUCLEOTIDE RATIO
Authors: Rahn R. O. , Sellin H. G.
Published: January 2008

Abstract— DNA containing 5‐iododeoxyuridine substituted at levels ranging from 1 to 24% was irradiated at 365 nm in the presence of various amounts of the Hoechst dye 33258. The subsequent loss of iodine was measured by following the loss of radioactive iodine (125I) from filter immobilized DNA subjected to repeated washings. A plot of the photochemical cross section (s̀B) for this process as a function of r, the molar ratio of dye added per nucleotide present, shows a maximum at r= 0.04 to 0.06, followed by a decrease with increasing dye‐to‐phosphate ratios to give a minimum at r= 0.5. Increasing the amounts of dye further results in s̀B reaching a second maximum at r 1, after which it levels off. An attempt was made to interpret these results in terms of the binding models currently employed for analyzing binding of Hoechst dye to DNA. Chain breaks as measured in alkali were also measured and found to be enhanced by the dye; the ratio of breaks per iodine loss was 0.9.
PHYSIOLOGICAL ASYMMETRY IN ETIOLATED PEA EPICOTYLS: RELATION TO PATTERNS OF AUXIN DISTRIBUTION AND PHOTOTROPIC BEHAVIOR*
Authors: Kuhn Helene , Galston Arthur W.
Published: January 2008

Abstract— Etiolated pea seedlings require transformation of Pr phytochrome to Pfr before they display optimal phototropic response to unilateral blue light. This study investigates the possible role of auxin transport in explaining these phenomena. Labeled [2–14C]IAA applied to the intact terminal buds of dark‐grown and red light‐treated pea seedlings was measured 210 min later on the shaded and illuminated sides of the epicotyl as a function of direction and duration of irradiation with blue light. Totally darkened epicotyls show an asymmetry in distribution of radioactivity in the upper growth zone of the epicotyl, in favor of the side under the concave part of the apical hook. Red light, which greatly potentiates curvature toward subsequent unilateral blue light, lowers this asymmetry. Blue light directed to the epicotyl of red‐pretreated plants in a plane parallel to the hook and from the side bearing the convex portion of the hook induces positiive phototropic curvature as well as a surplus of radioactivity on the illuminated side of the upper epicotyl and on the shaded side of the lower growth zone of the epicotyl. Light directed to the side bearing the concave part of the hook also causes an accumulation of counts in the upper part of the lighted side but produces neither curvature of the epicotyl nor accumulation of counts in the lower shaded side. Because of this built‐in physiological asymmetry in the growth zone just below the apical hook, it is difficult to explain the effects of red and blue light on curvature in terms of patterns of auxin distribution alone.
IDENTIFICATION OF A TRANSFORMING ras ONCOGENE IN AN ULTRAVIOLET RADIATION‐INDUCED CORNEAL TUMOR OF Monodelphis domestica
Authors: Sabourin Carol L. K. , Freeman Abbie G. , Kusewitt Donna F. , Ley Ronald D.
Published: January 2008

Abstract— Chronic exposure of the gray, short‐tailed opposum, Monodelphis domestica to ultraviolet radiation (UVR) induces mesenchymal tumors of the cornea. High molecular weight DNA samples from 6 UVR‐induced corneal tumors were assayed for their ability to transform NIH 3T3 cells to tumorigenicity. NIH 3T3 cells transfected with DNA from 5 of the corneal tumors produced 14 tumors in nude mice. Cell lines were established from these tumors. DNA from 13 of 14 tumor cell lines contained repetitive opossum DNA sequences. Southern blot analysis revealed that DNA from 3 of 4 cell lines derived from tumorigenic NIH 3T3 cells transfected with DNA from a single opposum tumor contained opossum Ki‐ras oncogene sequences in addition to the murine Ki‐ras gene. Northern blot analysis of mRNA from a mouse tumor cell line containing opossum Ki‐ras gene sequences showed mRNA species identical in size to opossum Ki‐ras mRNA, as well as murine Ki‐ras mRNA species. These results suggest that an activated Ki‐ras oncogene was present in one of the original opossum corneal tumors tested. Thus, activation of Ki‐ras may play a role in the development of UVR‐induced corneal tumors in Monodelphis domestica. Further characterization of ras oncogenes in these opossum tumors may provide information on the molecular mechanisms by which UVR induces corneal tumors in this species.
SYNTHETIC CAROTENOIDS, NOVEL POLYENE POLYKETONES AND NEW CAPSORUBIN ISOMERS AS EFFICIENT QUENCHERS OF SINGLET MOLECULAR OXYGEN
Authors: Devasagayam Thomas P. A. , Werner Thomas , Ippendorf Hans , Martin Hans‐Dieter , Sies Helmut
Published: January 2008

Abstract— Novel synthetic polyene polyketones and new synthetic capsorubin isomers were examined for their ability to quench singlet molecular oxygen (1O2) generated by the thermodissociation of the endoperoxide of 3,3'‐(l,4‐naphthylene) dipropionate (NDPO2). C28‐polyene‐tetrone (1) exhibits the highest physical quenching rate constant with 1O2 (kq= 16 × 109M‐1 s‐1). For comparison, the rate constant for the most efficient biological carotenoid, lycopene (3) is kq= 9 × 109M‐1 s‐1 that of β‐carotene (5) kq= 5 × 109M‐1 s‐1. The presence of two oxalyl chromophores at the ends of the polyene chain seems to enhance the 1O2 quenching ability in the C28‐polyene‐tetrone (1). C28‐polyene‐tetrone‐diacetal (2) (kq= 9 × 109M‐1 s‐1) and C40‐epiisocapsorubin (4) (kq= 8 × 109M‐1 s‐1) also have high 1O2 quenching abilities. Two carotenoids from plants, phytoene and phytofluene, were much less efficient, kq values being below 107M‐1 s‐1. Due to the very high singlet oxygen quenching abilities, C28‐polyene‐tetrone (1), C28‐polyene‐tetrone‐diacetal (2) and C40‐epiisocapsorubin (4) may have potential use in preventing 1O2‐induced damage in biological and non‐biological systems.
WAVELENGTH DEPENDENCE (150–290 nm) OF THE FORMATION OF THE CYCLOBUTANE DIMER AND THE (6–4) PHOTOPRODUCT OF THYMINE
Authors: Yamada Hiroyuki , Hieda Kotaro
Published: January 2008

Abstract— The action cross sections for the formation of the cyclobutane dimer and the (6–4) photoproduct of thymine as well as the absorption cross sections of thymine were determined in the wavelength region between 150 and 290 nm. Thymine films sublimed on glass plates were irradiated by monochromatic photons in a vacuum; the induced photoproducts were quantitatively analyzed by high‐performance liquid chromatography (HPLC). Under our conditions, two major peaks appeared on the HPLC chromatograms of irradiated samples. The two peaks were identified as being the cis‐syn cyclobutane dimer and the (6–4) photoproduct, based on their HPLC retention times, absorption spectra in the effluent, and photochemical reactivity. The fractions of the two photoproducts increased linearly with the fluence at low fluences over the entire wavelength range. Their action cross sections were determined by the slopes of the linear fluence response curve at 10 nm intervals between 150 and 290 nm. The two action spectra showed a similar wavelength dependence and had a maximum at 270 nm as well as two minor peaks at 180 and 220 nm, at which wavelengths the peaks of the absorption spectrum of thymine sublimed on a CaF2 crystal plate appeared. The quantum yields had relatively constant values of around 0.008 for the dimer and 0.013 for the (6–4) photoproduct above 200 nm, decreasing to 0.003 and 0.006, respectively, at 150 nm as the wavelength became shorter.
ANTAGONISTIC EFFECTS OF RED AND FAR‐RED LIGHTS ON THE STABILITY OF PHOTOSYSTEM II IN PEA LEAVES EXPOSED TO HEAT
Authors: Havaux Michel , Strasser Reto J.
Published: January 2008

Abstract— The presence of light during exposure of intact pea leaves to high temperature (40°C) protects Photosystem II (PSII) against inactivation, as indicated by the preservation of the maximal variable 685 nm chlorophyll fluorescence and the photosynthetic oxygen evolution. This photoprotection was observed (i) to be saturated at low fluence rates (ca 10 W m‐2) and (ii) to be strongly dependent on the spectral characteristics of the light. It was specifically induced by red light (630–670 nm) whereas other wavelengths were much less protective. A strong antagonism between red and far‐red lights was also observed, with PSII stabilization by red light being partially cancelled by additional far‐red light.
INHIBITION OF 12‐O‐TETRADECANOYLPHORBOL‐13‐ACETATE‐INDUCED TUMOR PROMOTION IN MURINE SKIN BY SYSTEMIC EFFECTS OF ULTRAVIOLET IRRADIATION
Authors: Gensler H. L. , Simpson P. J. , Powell M. Broome
Published: January 2008

Abstract— Systemic effects of UVB irradiation (280–320 nm) have been shown to prevent subsequent chemical tumorigenesis induced by an initiation—promotion protocol. The present investigation was designed to determine whether initiation or promotion is prevented by UV irradiation. Groups of 25 B6DZF1/J mice received 12 weeks of intermittent dorsal UVB radiation treatments administered before, or 3 weeks after, initiation with a single application of 7,12‐dimethylbenz[a]anthracene on the ventral skin. All mice were promoted ventrally with 5 μg 12–0‐tetradecanoylphorbol‐13‐acetate (TPA) applied three times weekly throughout the experiment. UV irradiation consisted of five 30‐min exposures per week to a bank of 6 Westinghouse FS40 sunlamps. UV irradiation applied before or after initiation resulted in a decrease of 18—‐16 tumors per group of 25 mice, for a reduction of 61 and 50%, respectively, at 24 weeks after the first TPA treatment. Thus, prevention of tumor development was similar whether the UV influence was present or not during initiation. This finding suggests that the UV prevention of promotion could account for UV inhibition of skin tumors induced by an initiation—promotion regimen. Consistent with this concept, pretreatment of mice with dorsal UVB radiation was found to reduce DNA synthesis after exposure to TPA by 46%, although it did not decrease tritiated benzo[a]pyrene binding to DNA, in ventral epidermis. Thus, UVB irradiation systemically reduced TPA‐induced tumor promotion in murine skin.
DNA AS A SOLAR DOSIMETER IN THE OCEAN*
Authors: Regan J. D. , Carrier W. L. , Gucinski H. , Olla B. L. , Yoshida H. , Fujimura R. K. , Wicklund R. I.
Published: January 2008

Abstract— Stratospheric ozone depletion may result in increased solar UV‐B radiation to the ocean's upper layers and may cause deleterious effects on marine organisms. The primary UV‐B damage induced in biological systems is to DNA. While physical measurements of solar UV‐B penetration into the sea have been made, the effective depth and magnitude of actual DNA damage have not been determined. In the experiments reported here, UV‐B‐induced photoproducts (cyclobutane pyrimidine dimers) have been quantified in DNA molecules exposed to solar UV at the surface and at various depths in clear, tropical marine waters off Lee Stocking Island (23° 45‘ N, 76° 0.7’ W), Exuma Cays, Bahamas. [14C]thymidine‐labeled DNA or unlabeled bacteriophage øX174 DNA was placed in specially designed quartz tubes at various depths for up to five days. Following exposure, DNA samples were removed to the laboratory where UV‐B‐induced pyrimidine dimers were quantified using a radiochromatographic assay, and bacteriophage DNA inactivation by solar UV‐B was assayed by plaque formation in spheroplasts of Escherichia coli. Pyrimidine dimer induction was linear with time but the accumulation of dimers in DNA with time varied greatly with depth. Attenuation of dimer formation with depth of water was exponential. DNA at 3 m depth had only 17% of the pyrimidine dimers found at the surface. Bacteriophage øX174 DNA, while reduced 96% in plaque‐forming ability by a one day exposure to solar UV at the surface of the water, showed no effect on plaque formation after a similar exposure at 3 m. The data collected at the water's surface showed a “surface‐enhanced dose” in that DNA damages at the real surface were greater than at the imaginary surface, which was obtained by extrapolating the data at depth to the surface. These results show the sensitivity of both the biochemical (dimers) and biological (phage plaques) DNA dosimeters. DNA dosimeters offer a sensitive, convenient and relatively inexpensive monitoring system, having both biochemical and biological endpoints for monitoring the biologically effective UV‐B flux in the marine environment. Unlike physical dosimeters, DNA dosimeters do not have to be adjusted for biological effectiveness since they are sensitive only to DNA‐mediated biologically effective UV‐B radiation. Results of pyrimidine dimer induction in DNA by solar UV accurately predicted UV doses to the phage DNA.
KINETIC STUDY OF STRESS‐INDUCED LUMINESCENCE FROM DIFFERENT TISSUES
Authors: Radotić Ksenija , Jeremić Milorad , Radenović ČEdomir
Published: January 2008

Abstract— Exponential decay of the stress‐induced luminescence from different tissues was resolved into the first order reaction components and appropriate rate constants were determined from the reaction half‐times. Kinetic analysis shows that luminescence decays generally through three parallel pseudo‐first order reactions which can be affected independently. The same order of magnitude (even very close numerical values) of the rate constants of luminescent reactions induced by different chemical and physical stimuli in different organisms suggests that a common mechanism is included in their luminescence. Analysis of the secondary kinetics appearing in the particular cases of the luminescence decay, as well as kinetic analysis of the stress‐induced radical decay measured by electron paramagnetic resonance, show that activated forms of oxygen and peroxy‐radicals have a central role in the luminescence emission.
9,11‐DIcis‐12‐FLUORORHODOPSIN. CHROMOPHORE PROPERTIES FROM 19F‐NMR STUDIES
Authors: Colmenares Leticia U. , Liu Robert S. H.
Published: January 2008

Abstract— From a 19F‐NMR study of 9,11‐dicis‐12‐fluororhodopsin and its photobleached product, we concluded that the initially formed chromophore retained its configuration and the photoproduct corresponded to the two‐bond isomerized all‐trans. Upon standing, it slowly isomerized to the 9‐cis isomer. The method represents a direct, non‐destructive procedure for determining configuration purity of the pigment formed. Its unique fluorine opsin shift value is consistent with the expected different orientation of the fluoro‐substituent in a dicis pigment.
TEMPORAL CHANGES IN SURFACE ULTRAVIOLET RADIATION: A STUDY OF THE ROBERTSON‐BERGER METER AND DOBSON DATA RECORDS
Authors: Frederick John E. , Weatherhead Elizabeth C.
Published: January 2008

Abstract— Ultraviolet radiation data sets obtained by Robertson‐Berger meters located at Bismarck, ND and Tallahassee, FL show variations over the time period 1974–1985 which we interpret in terms of clouds and ozone. Cloudiness is a major source of variance in the irradiance measurements. When this variance is minimized, the monthly mean Robertson‐Berger meter record contains trends which are in good agreement with irradiance calculations based on the Dobson ozone measurements in spring, summer and early autumn. Despite the agreement among trends, predictions based on the ozone data explain 40% or less of the variance in the monthly mean radiation values over the 11‐year period. The radiation measurements contain negative trends in winter which are contrary to expectations based on the behavior of ozone alone. These trends remain when we minimize the effects of cloudiness. Based on the information available in this study, it is not possible to determine whether the wintertime trends have an instrumental or environmental origin.
THE LIGHT‐HARVESTING SYSTEM OF THE UNICELLULAR ALGA Mantoniella squamata (PRASINOPHYCEAE): EVIDENCE FOR THE LACK OF A PHOTOSYSTEM I‐SPECIFIC ANTENNA COMPLEX
Authors: Schmitt A. , Herold A. , Welte C. , Wild A. , Wilhelm C.
Published: January 2008

The light‐harvesting complexes (LHC) were isolated from the unicellular alga Mantoniella squamata (Prasinophyceae) by sucrose‐density centrifugation. Beside the major LHC (II), a photosystem I complex was obtained that could be dissociated into a photosystem I core complex and an associated LHC I. In contrast to other chlorophyll b‐containing antennae, both LHC II as well as LHC I were observed to be identical with respect to the following features: the molecular weights, the isoelectric points and the retention behavior on anion‐exchange chromatography of the apoproteins, the pigment content and the absorption and fluorescence spectra. We conclude from these results that Mantoniella contains only one homogenous population of LHC, which cooperate with both photosystems not on the basis of specific recognition but on the simple basis of statistical interaction. This is the first report of a chlorophyll b‐containing light‐harvesting system without any subpopulations: therefore, it is suggested that it arises from a most primitive type of chlorophyll b‐containing chloroplast.
PIGMENT COMPLEXES OF LIGHT‐HARVESTING CHLOROPHYLL a/b BINDING PROTEIN ARE STABILIZED BY A SEGMENT IN THE CARBOXYTERMINAL HYDROPHILIC DOMAIN OF THE PROTEIN*
Authors: Paulsen Harald , Kuttkat Andrea
Published: January 2008

In order to identify segments of light‐harvesting chlorophyll a/6‐binding protein (LHCP) that are important for pigment binding, we have tested various LHCP mutants regarding their ability to form stable pigment‐protein complexes in an in vitro reconstitution assay. Deletion of 10 C‐terminal amino acids in the LHCP precursor, pLHCP, did not significantly affect pigment binding, whereas deletion of one additional amino acid, a tryptophan, completely abolished the formation of stable pigment‐protein complexes. This tryptophan, however, can be exchanged with other amino acids in full‐length pLHCP without noticeably altering the stability or spectroscopic properties of pigment complexes made with these mutants. Thus, the tryptophan residue is not likely to be involved in a highly specific interaction stabilizing the complex. A double mutant of LHCP lacking 66 N‐terminal and 6 C‐terminal amino acids still forms pigmented complexes that are virtually identical to those formed with the full‐length protein concerning their pigment composition and spectroscopic properties. We conclude that about 30% of the polypeptide chain in LHCP is not involved in pigment binding.
FLUORESCENCE LINE NARROWING SPECTROSCOPY OF Zn PORPHYRINS*
Authors: Logovinsky Veronika , Kaposi A. D. , Vanderkoor J. M.
Published: January 2008

Fluorescence line narrowing (FLN) spectroscopy was used to study the vibrational features of Zn porphyrins, including Zn octaethylporphine, Zn mesoporphyrin, Zn deuteroporphyrin and Zn coproporphyrin, and the interaction of these porphyrins with their solvent matrices. A number of ground‐state vibrational levels were identified for each of the Zn porphyrins. Six of these levels persistent throughout almost all spectra were analyzed in terms ofcontributions of specific internal vibrational modes of the porphyrins. A number of other vibrational levels were identified as characteristic of the peripheral substituents of Zn porphyrin. Phonon wing contribution in the FLN spectra increased with increased polarity of the solvent matrix, and the Stokes shift calculated from the conventional spectra was correlated with the strength of phonon coupling. Specific vibrational modes were found to couple differently with the solvent and to have different phonon wings. The conventional and energy‐selected spectra of Zn coproporphyrin in 5 M guanidine HCI suggest that guanidine ligates to the Zn atom.
ISOLATION, CHARACTERIZATION AND RECONSTITUTION OF PHYCOBILIPROTEIN ROD‐CORE LINKER POLYPEPTIDE COMPLEXES FROM THE PHYCOBILISOME OF Mastigocladus laminosus*
Authors: Glauser Manuel , Sidler Walter , Zuber Herbert
Published: January 2008

A rod‐core complex, (αβ)6PC. LRC29.5,(αβ)3APC.LC8.9, composed of hexameric phycocyanin (PC) and trimeric allophycocyanin (APC) subcomplexes associated to the CpcG2 gene product, has been isolated from the phycobilisome of Mastigocladus laminosus. Exactly the same complex was obtained by reconstitution using the subcomplexes(αβ)3PC. LRC 29.5 and (aβ)3APC.LC8.9 as educts. Spectroscopic analysis of the isolated PC‐LR and PC‐LRC complexes from M. laminosus shows that the LRC cause the largest red‐shift in the absorbance and fluorescence emission maxima of PC. These results indicate that LRC mediate PC‐APC interactions in vitro. Only the CpcG2 polypeptide was able to promote this specific interaction, as neither CpcG3‐PC nor, as a negative control, CpcC‐PC complexes showed any reconstitution products with the core subcomplex (αβ)3APC.Lc8.9. This is an indication that each of the four LRC in the phycobilisomes of M. laminosus and Anabaena sp. PCC 7120 attaches two peripheral rods specifically to one of four different core binding sites.
PHOTOPHYSICAL PROPERTIES OF 3,3′‐DIALKYLTHIACARBOCYANINE DYES IN HOMOGENEOUS SOLUTION
Authors: Krieg Marianne , Redmond Robert W.
Published: January 2008

The photophysical properties of 3,3′‐dialkylthiacarbocyanine iodides and chlorides were measured in various solvents. It was found that photoisomerization and fluorescence are the major contributors to the deactivation of the excited singlet state; intersystem crossing occurs with only a very low efficiency. In ethanol, a triplet yield of 0.004 and a singlet oxygen quantum yield of 0.002 were determined. The photophysical parameters of these dyes are not substantially influenced by the length of the alkyl chain or the size of the halide counterion. The substitution of an ethyl with an octadecyl‐chain only slightly hinders photoisomerization, and the replacement of the chloride with an iodide reduces only marginally the fluorescence lifetimes and fluorescence quantum yields in chloroform. A significant external heavy‐atom effect is observed using dibromoethane as a solvent: triplet and singlet oxygen yields increase7–10‐fold, and the triplet lifetime decreases from 55 μs to 15 mUs.
TIME‐GATED FLUORESCENCE IMAGING FOR THE DIAGNOSIS OF TUMORS IN A MURINE MODEL
Authors: Cubeddu R. , Canti G. , Taroni P. , Valentini G.
Published: January 2008

A system for time‐gated fluorescence imaging was used to perform measurements on tumor‐bearing mice treated with hematoporphyrin derivative (HpD). The aim of the study was to define the potential of this technique in the diagnosis of tumors by taking advantage of the long fluorescence lifetime of the exogenous dye with respect to the decay times of the natural fluorescence. After the administration of three different drug doses (5, 10 and 25 mg/kg body weight), fluorescence images were acquired at various uptake times (from 2 h to 10 d), to determine the best instrumental conditions and experimental procedure for the detection of tumors in the murine model considered. The optimal fluorescence contrast between the tumor area and the surrounding healthy tissue was found at 12 h after the administration of either 5 or 10 mg/kg HpD and was anticipated at 8 h for the highest drug dose. In this optimum condition, the tumor region could be identified even after the injection of 5 mg/kg HpD. A better fluorescence contrast was always obtained in 15 ns‐delayed images with respect to synchronous ones.
THE UNUSUAL UVA‐DEPENDENT ANTIVIRAL PROPERTIES OF THE FUROISOCOUMARIN, CORIANDRIN
Authors: Hudson J. B. , Graham E. A. , Harris L. , Ashwood‐Smith M. J.
Published: January 2008

The novel furoisocoumarin, coriandrin, which was found recently to possess an interesting combination of photobiological properties, was investigated for antiviral activity in the presence and absence of UVA (long‐wavelength ultraviolet radiation). In contrast to results obtained with other antiviral furocoumarins, such as 8‐MOP (8‐methoxypsoralen), coriandrin was much more phototoxic to the RNA‐virus Sindbis virus than to the DNA‐virus murine cytomegalovirus, although both viruses were substantially more sensitive to this compound than they were to 8‐MOP. Human immunodeficiency virus, HIV‐1, was also susceptible to coriandrin + UVA.

Another unexpected finding was that viruses without membranes were completely resistant to coriandrin. This suggests that a membrane component was a target for the compound. The antiviral activity of coriandrin was profoundly inhibited by serum components in the reaction mixtures, which suggests that the compound may have a strong affinity for certain protein or lipid materials, although maximal interference was only obtained when all components of the reaction mixture, virus, coriandrin and serum, were irradiated simultaneously.

Thus it appears that coriandrin has unusual antiviral properties that would not be predicted from its chemical similarity to furocoumarins.
DNA NICKING BY ULTRAVIOLET RADIATION IS ENHANCED IN THE PRESENCE OF IRON and OF OXYGEN
Authors: Audic Annie , Giacomoni Paolo U.
Published: January 2008

Double‐stranded covalently closed circular supercoiled DNA (ccc DNA) from plasmid pUK 9 was irradiated in vitro at denned wavelengths in the UV region (290, 313 and 365 nm). The nicking was monitored by electrophoresis on agarose gels, ethidium staining and densitometric quantitation of supercoiled and relaxed moieties. At the explored wavelengths, the dose required for introducing one nick per million phosphodiester bonds diminishes with increased concentration of added ferric iron, whereas the effect of cupric iron is practically negligible. Adding metal chelators or bubbling argon prior to the irradiation results in a dramatic increase in the dose required for introducing one nick per million phosphodiester bonds. Taken together, these results seem to indicate that iron and oxygen play a role as cofactors in the UV‐induced nicking of ccc DNA in vitro.
MOLECULAR CHANGES DURING THE PHOTOOXIDATION OF α‐CRYSTALLIN IN THE PRESENCE OF UROPORPHYRIN
Authors: Dillon James , Chiesa Raul , Wang Ren‐Hong , McDermott Martin
Published: January 2008

Singlet oxygen reacts preferentially with three amino acids in proteins, His, Trp and Met. In order to study the specific molecular events that result from such oxidations, calf a‐crystallin was photooxidized in the presence of uroporphyrin and the reactions were investigated by high performance liquid chromatography peptide mapping using a photodiode array detector followed by fast atom bombardment mass spectrometry (FAB‐MS). From these studies, the following conclusions can be inferred: (1) Upon photooxidation residue Met‐68 of the B chain is oxidized to Met sulfoxide, whereas residue Trp‐60 remains intact. (2) Two of the 16 His residues in a‐crystallin are photooxidized with an apparent pKa of ca 7.0. (3) FAB‐MS analysis suggests that residue Lys‐166 close to the C‐terminal end of the A chain forms a cross‐link with the His‐7 residue close to the N‐terminal end of the A chain. This may be either an inter‐ or intramolecular cross‐link.
PHOTON EMISSION BY BACTERIA CHALLENGED WITH PHENYLACETALDEHYDE. A POSSIBLE DISTINCTION BETWEEN GRAM‐POSITIVE and GRAM‐NEGATIVE BACTERIA
Authors: Surpili Marcelo José , Faijoni‐Alario Adelaide , Cilento Giuseppe
Published: January 2008

With all bacteria tested, addition of phenylacetaldehyde leads to light emission. The latter is markedly stronger with gram‐negative bacteria, presumably because they possess a thinner wall and an extra external lipophilic membrane. Consistent with this explanation, the bactericidal effect of phenylacetaldehyde is also stronger with gram‐negative bacteria.

The spectrum of the emitted light shows maximal emission in the 500 nm region and is very similar to that observed when a protein (bovine serum albumin), free amino acids or isopropylamine reacts with phenylacetaldehyde.
INCLUSION AND FLUORESCENE QUENCHING OF 2, 3‐DIMETHYLNAPHTHALENE IN β‐CYCLODEXTRIN CAVITIES
Authors: Encinas M. V. , Lissi E. A. , Rufs A. M.
Published: January 2008

Abstract— The fluorescence quenching of 2,3‐dimethylnaphthalene (DMN) incorporated to β‐cyclodextrin (β‐CD) cavities by different olefins (fumaronitrile, acrylonitrile, acrylamide and 2‐hydroxyethylmethacrylate) has been measured as a function of the β‐CD concentration. The quenching efficiency decreases when the β‐CD concentration increases, but extrapolation of the data to infinite cavities concentration does not indicate complete protection. These results are interpreted in terms of two quenching processes, one of them taking place between 2,3‐dimethylnaphthalene associated to a β‐CD cavity and free quencher, and the other between the DMN and the quencher molecule, both associated with a different cavity. The rate constants of both quenching processes and the β‐CD quencher association constant are obtained from the dependence of the quenching efficiency with β‐CD concentration.
STRUCTURE OF A THYMINE‐THYMINE ADDUCT FORMED BY MENADIONE PHOTOSENSITIZATION
Authors: Katz Henry , Stallings William , Glusker Jenny P.
Published: January 2008

Abstract— The structure of one of the dithymine adducts formed by near‐UV photosensitization of aqueous oxygenated thymine in the presence of 2‐methyl‐ 1, 4‐naphthoquinone is reported. The compound, 6′β‐hydroxy‐5′β‐1 ‐ [5‐methylpyrimidinyl‐ 2,4‐dione]‐5′‐6′‐dihydrothymine has one thymine ring (ring I) linked through the 1‐nitrogen atom to the C5′ atom of a second thymine, which has been hydroxylated af C6′ (ring II). Crystals are monoclinic, space group 12/c, and the structure was refined to Robs= 0.036 for 2072 unique reflections with intensities I greater than 2.33s̀(I). Ring I is planar, whereas ring II is not. Ring I and the OH group on ring II are cis to ring II. The planar ring I and the OH group are attached, respectively, in an equatorial and axial manner to ring II (which is in the sofa conformation). The planar rings I of close‐lying pairs of molecules stack parallel to each other. The structure is held together by a hydrogen‐bonding system consisting of the water molecules, the NH groups, two of the C=O groups and the OH group. The chemical formula and relative configurations at C5′ and C6 are established by this analysis.
In vitro AND in vivo UPTAKE OF BENZOPORPHYRIN DERIVATIVE INTO HUMAN AND MINISWINE ATHEROSCLEROTIC PLAQUE
Authors: Hsiang York N. , Crespo M. Teresa , Richter Anna M. , Jain Ashok K. , Fragoso Miguel , Levy Juli G.
Published: January 2008

Abstract— Befnzoporphyrin derivative(BPD) has been demonstrated to be fnew potent photosentsitze for photodynamic therapy(PDT). Althought most of wrok on BPD has been focused on its potential applications for cancer tratment, BPD amy have potential clilnical uses in the treatment of artheros clerosis. The purposes of this study was to determine in vitro and vivo uptake of BPD into atherosclerotic plaque. Samples of atherosclerotic human femoral and popliteal arteries were incubated with BPD‐monoacid, ring A(BPD‐MA) for 1 h in the following concentrations: 1, 5, 10, 20, 30 and 40 μg/mL. fluorescence from all samplesd was determined by chemical etraction with a spectrofluorometer. the tissue concentration for human arteries was 0.37 ± 0.03, 2.78 ± 1.5, 3.6 ± 1.91, 7.15 ± 2.36, 8.06 ± 3.09 and 14.6 ± 4.81 μg/g, respectively. In aeddition, three miniswine were rendered atherosclerotic and given BPD 2.0 mg/ Kg intravenously. The concentration of BPD‐MA in miniswine aorta was93–190 ng/g and the plaque/normal ration was 1.7–3.5, for miniswine cartoid artery contained 54 ng/g. this study showed that BPD‐MA was taken up in atherosclerotic vesselsd both in vitro and in vivo and mey have potential for PDT of atherosclerosis.
PHOTOSENSORY TRANSDUCTION IN CILIATES. I. AN ANALYSIS OF LIGHT‐INDUCED ELECTRICAL AND MOTILE RESPONSES IN Stentor coeruleus
Authors: Fabczak Stanislaw , Fabczak Hanna , Tao Nengbing , Song Pill‐Soon
Published: January 2008

Abstract— Light‐induced membrane potantial changes and motile responses have been studied in Stentor cells with intracellular microelectrodes and video microscopy, respectively. Intracellulae microelectrode showed that step‐up increase in light induced an electrical membrane response which consisted of an initial membrane depolarization (photoreceptor potential) followed by an action potential and maintaining phase of depolarization (afterdepolarization). The amplitude of the receptor potetial is dependent on the intensity of light stimulus and the action potetials appears with a lag period (latency) after the onset of light stimuklus. The extent of the membrane established between the latency for te action poitential and the onset of ciliary reversal (stop responses). A time correlation was also observed between the duration of the membrane afterdepolarization and the duration of backward swimming. the action spectrum for the photoreceptor potential amplitude of Stentor resembled the action spectra for the latency of ciliary reversal and the photoresponsiveness, iondicating that the photomovement response and membrane potential changes are coupled through the same photosensor system. A hypothesis on the photosensory transduction chain in Stentor is discussed according to ehich the photoreceptors and the ciliary apparatus is mediated by the membrane potential canges.
WAVELENGTH DEPENDENCE OF THE PHOTODECOMPOSITION OF 2‐DEOXYTHYMIDYLYL‐(3′→5′)‐2′‐DEOXYTHYMIDINE, dTpdT, IRRADIATED BY MONOCHROMATIC VACUUM‐UV PHOTONS ABOVE 50 nm
Authors: Mikio Saitou
Published: January 2008

Abstract— 2′‐Deoxythymidylyl‐(3′→5′)‐2′‐deoxythymidine, dTpdT, was irradiated in solids with monochromatic synchrotron radiations at wavelengths between 50 and 260 nm, in order to investigate the photodecomposition mode of dTpdT in the wavelength region around and above the ionization potential. The photoproducts were separated and quantitatively analyzed by high‐performance liquid chromatography. The results of the present experiment were as follows: (1) Below 210 nm the major photoproducts were three decomposition products (thymine [Thy], 2′‐deoxythymidine 5′‐monophosphate [5′‐dTMP] and 2′‐deoxythymidine 3′‐monophosphate [3′‐dTMP]), whereas above 210 nm these decomposition products were under the detection limit and trace amounts of cyclobutane thymine (Thy) dimers (cis‐syn and trans‐syri) and thymine(6–4) photoproduct were detected. 2′‐Deoxythymidine (dThd) was not detected at any wavelengths tested. (2) The yields of the three decomposition products had very similar wavelength dependence with each other: the yields increased exponentially with the decrease in the wavelength down to 100 nm, whereas they were relatively constant below 100 nm. (3) The ratios of the yields of dTMP (5′‐dTMP plus 3′‐dTMP) to the yield of Thy showed minor deviations from 1 both above and below the ionization potential of deoxyribose (9.7 eV, or 130 nm: Tasaki et al., 1990, J. Am. Chem. Soc. 112,538–548): the average ratio was 0.85 between 50 and 100 nm and 1.30 between 120 and 210 nm. The ratios should be 1 if photodecomposition is induced only by deoxyribose decomposition. These ratios therefore indicated that the major photodecomposition mode of dTpdT was the destruction of deoxyribose moieties and additional minor modes caused the deviation from 1. (4) The yield of 5′‐dTMP was twice as much as the yield of 3′‐dTMP, showing that the deoxyribose residue without the 5′‐phosphate group was more sensitive than the deoxyribose residue with the 5′‐phosphate group.
THE PHOTOPHYSICAL CONSTANTS OF SEVERAL FLUORESCENT DYES PERTAINING TO ULTRASENSITIVE FLUORESCENCE SPECTROSCOPY
Authors: Soper Steven A. , Nutter Harvey L. , Keller Richard A. , Davis Lloyd M. , Shera E. Brooks
Published: January 2008

Abstract— The successful implementation of ultrasensitive fluorescence spectroscopy of biological and chemical species depends upon certain photophysical parameters associated with the fluorescent dye used in the investigation. These parameters include the fluorescence quantum efficiency, photodestruction quantum efficiency, absorption cross section and fluorescence lifetime. These photophysical constants were measured for several fluorescent dyes that are used for the tagging of biological species. Three different solvents, ethanol, water and a cationic surfactant used above its critical micelle concentration, were studied. The effective photon yield (ratio of the fluorescence quantum yield to the photodestruction quantum efficiency) for the dyes is nearly 100 times greater in ethanol than it is in water because of the superior photostabilities of these dyes in ethanol solvents. The implications of these parameters for the design of an ultrasensitive fluorescence experiment are discussed.