bluuebunny/crossref_metadata_2025_split huggingface dataset:
DIHYDROXY‐CAROTENOID LIPOSOMES INHIBIT PHOTOTOXICITY IN Paramecium caudatum
Authors: Rich Marvin R. , Strulle Ronald de , Ferraro Greg , Brody Steven S. 
Published: January 2008

Abstract—The phototoxic effects of hematoporphyrin derivative, using Paramecium cuudatum as a model system, are significantly reduced in the presence of carotenoid‐containing liposomes. Multilam‐melar large or small unilammelar vesicles, containing specific carotenoids, were effective in protecting the organism, whether administered exogenously in the bathing solution, or via incubation of paramecia in starved culture media containing carotenoid liposomes. The effectiveness of the carotenoids as inhibitors of phototoxic effects was found to depend on the mode of administration, with small unilammelar being more effective than multilammelar large vesicles for all carotenoids tested. Small unilammelar vesicles containing the dihydroxy‐carotenoids zeaxanthin or astaxanthin afforded the greatest protection in both exogenous and endogenous studies. The results of this study suggest that carotenoid efficacy may be determined, in part, by the environment of the carotenoid molecules.
APPLICATION OF TIME‐RESOLVED DIFFUSE REFLECTANCE TECHNIQUES IN STUDIES OF REACTION INTERMEDIATES IN SUSPENSIONS OF BACILLUS SUBTILIS
Authors: BERINSTAM A.B. , SCAIANO J.C. , BOHNE C. , MALENFANT P.R.L. , SPROIT G.D. 
Published: January 2008

Abstract:Short lived reaction intermediates such as triplet stam and free radicals can be detected in vivo using laser photolysis techniques with time‐resolved diffuse reflectance detection. This novel approach is illustrated for bacterial suspensions of Bacillus subtilis.
LIGHT‐GROWN PLANTS OF THE CUCUMBER LONG HYPOCOTYL MUTANT EXHIBIT BOTH LONG‐TERM AND RAPID ELONGATION GROWTH RESPONSES TO IRRADIATION WITH SUPPLEMENTARY FAR‐RED LIGHT
Authors: Smith Harry , Turnbull Matthew , Kendrick Richard E. 
Published: January 2008

Abstraet—Seedlings of wild type (WT) and the lh mutant of Cucumis sativus were grown in white light and given supplementary far‐red radiation either to the whole plant, or via fiber‐optic probes directed at the apical region of the hypocotyl. In both WT and mutant seedlings, reducing the ratio of red to far‐red radiation resulted in significant increases in extension growth. Direct measurement of extension rate by transducer techniques revealed that the mutant seedlings responded to additional far‐red radiation by an increment in extension rate that was equivalent to that observed with the WT seedlings. Assuming that the lh mutant is deficient in phytochrome B (Kendrick and Nagatani, The Plant Journal1: 133–139, 1991), these results indicate that although phytochrome B clearly has an important role in the induction of the shade avoidance syndrome, it is unlikely to be the sole responsible receptor.
THE TEMPERATURE DEPENDENCE OF Pfr ACTION GOVERNS THE UPPER TEMPERATURE LIMIT FOR GERMINATION IN LETTUCE
Authors: Fielding Anthony , Kristie David N. , Dearman Peter 
Published: January 2008

Abstract—In most cultivars of lettuce (Lactuca saliva L,), red light acting through the red/far‐red reversible phytochrome system promotes full germination within the20–30°C range, but at progressively higher temperatures germination declines sharply. The relationship between this upper ternperature limit for germination and the temperature dependence of phytochrome action was investigated in Grand Rapids lettuce. In fresh seeds the GT50 (temperature giving half maximal germination) was ca 29–30°C. In these seeds, escape from far‐red reversibility did not occur at 35°C, a temperature above the GT50, but occurred rapidly at 27°C, a temperature below the upper limit. Increasing periods of dark pretreatment at high temperature (35°C) or increasing concentrations of the germination inhibitor coumarin caused a progressive decline in the GT50, Escape from photoreversibility did not occur at 27°C in seeds in which the GT50 had been reduced to less than 25°C by coumarin or by prolonged high temperature pretreatment. These results indicate that there is a close correlation between the position of the upper temperature limit for germination, and the temperature dependence of phytochrome action. We conclude that factors that alter the upper temperature limit for germination do so by changing the temperature dependence of phytochrome action.
PHYTOCHROME‐MEDIATED RAPID CHANGES IN THE LEVEL OF PHOSPHOINOSITIDES IN ETIOLATED LEAVES OF Zea mays
Authors: Guron Kuljeet , Chandok Meena R. , Sopory Sudhir K. 
Published: January 2008

Abstract—The role of the active form of phytochrome in Zea mays on the polyphosphoinositide cycle was studied. As little as 15 s of red irradiation of etiolated leaves immediately increased the level of phosphatidylinositol bisphosphate (PIP2) 3–6‐fold compared to unirradiated leaves. The elevated level of PIP2 decreased with longer red irradiations up to 5 min, but remained higher than in unirradiated leaves. The level of PIP2 decreased if red irradiation was followed by far‐red irradiation. Far‐red alone had no effect. Levels of phosphatidylinositol phosphate (PIP) and phosphatidylinositol did not change significantly. Since red irradiation significantly changed PIP, but not PIP, photocontrol appears to be at the PIP kinase and phospholipase level. In related studies of the effect of light on phospholipids, 5 min of red irradiation induced significant decreases in phosphatidylcholine and phosphatidylethanola‐mine.
DETECTION AND QUANTITATION OF THREE PHYTOCHROMES IN UNIMBIBED SEEDS OF: Avena sativa L.
Authors: Wang Yu‐Chie , Cordonnier‐Pratt Marie‐Michèle , Pratt Lee H. 
Published: January 2008

Abstract—Three phytochrome apoproteins in unimbibed seeds of Avena saliva L. were identified with monoclonal antibodies directed to, and specific for, three oat phytochromes with monomeric molecular masses of 125, 124 and 123 kDa [Wang et al., 1991, Planta 184, 96–104]. All three phytochromes were readily detected in embryo‐containing portions. Only trace amounts were found in endosperm tissue. Phytochrome photoreversibility was detected after concentration and partial purification of embryo extracts by fractionation with ammonium sulfate, indicating that at least one of these seed phytochromes had its chromophore prosthetic group bound to it. Immunoblot analyses were performed to quantitate each of the three phytochromes in unimbibed seeds. Quantitation of phytochromes in detergent‐free extracts led to serious underestimates of phytochrome contents in the unimbibed seeds. In contrast, more than 93% of each of the three phytochromes in the unimbibed seeds was extracted when a modified sodium dodecyl sulfate sample buffer was used as the extraction medium. In such extracts, we measured per embryo 1.40 ± 0.12. 1.60 ± 0.05 and 6.13 ± 0.31 ng of 125–, 124– and 123‐kDa phytochrome, respectively.
THE PHOTOPERIODIC CONTROL OF FLOWERING: PROGRESS TOWARD UNDERSTANDING THE MECHANISM OF INDUCTION
Authors: O'Neill Sharman D. 
Published: January 2008

Abstract—The mechanism of photoperiodic flower induction remains a major unsolved problem in plant development. Although it is firmly established that phytochrome is the primary photoreceptor in photoperiodic responses including flowering, the intermediate processes of induction including signal transduction, biochemistry of the induced state, and synthesis and identification of the floral stimulus are still obscure. In this review, advances in key areas of research that have contributed to our understanding of photoperiodic flower induction are discussed. These include the role of phytochrome in photoperiodic flowering, physiological characterization of the photoperiodic flowering response, the mechanism of photoperiodic time measurement during induction, and the nature of flower‐promoting and flower‐inhibiting substances. Finally, the role of alterations in gene expression in mediating photoperiodic flower induction is considered along with emerging opportunities for future research that may increase our understanding of the mechanism of flower induction.
ACRYLAMIDE QUENCHING OF THE FLUORESCENCE OF GLYCERALDEHYDE‐3‐PHOSPHATE DEHYDROGENASE: REVERSIBLE AND IRREVERSIBLE EFFECTS
Authors: Bastyns Katrin , Engelborghs Yves 
Published: January 2008

Abstract— The acrylamide quenching of the tryptophan fluorescence of apo and holo glyceraldehyde‐ 3‐phosphate dehydrogenase (GAPDH) was studied. In the case of apo‐GAPDH, the steady state fluorescence quenching cannot be described by the classical Stern‐Volmer equation: strong cooperative quenching is observed. In the presence of Pi and/or cofactor NAD+ an inaccessible fraction appears. Cooperative quenching is partially suppressed in the presence of Pi and fully absent in the presence of NAD+.The measurements of the fluorescence lifetimes of the holo‐enzyme by phasefluorometry allow the resolution of two lifetimes. The long‐lived component is quenched by acrylamide, the short‐lived component is not. Quenching induces a red shift of the steady state emission peak. The quenching parameters from the lifetime measurements allow the quantitative description of the steady state fluorescence quenching data.In agreement with the observations of orstan and Gafni (Photochemistry and Phorobiology, (1990) 31, 725–731), we find that acrylamide causes a slow, irreversible loss of activity and a reduction of titratable thiol groups when it acts on the apo‐enzyme. This inactivation is strongly reduced in the presence of NAD+. We show that this inactivation is also slowed down by the presence of Pi, and that it is accompanied by a loss of the NAD+ binding site.Blocking the thiol groups with 5,5'‐dithio‐bis‐(2‐nitrobenzoic acid) does not lead to a protection against the irreversible inactivation by acrylamide, showing that reactions other than thiol modifications are involved in the irreversible effect. A fraction of the inactivation can be reversed by treatment with mercapto‐ethanol.
Stentor coeruleus SHOWS POSITIVE PHOTOKINESIS
Authors: Iwatsuki Kenji 
Published: January 2008

Abstract— Stentor coeruleus responds to a sudden increase in light intensity with a step‐up photophobic response (avoiding reaction), and to collimated light with negative phototaxis. The peaks of the action spectra for the photophobic response and for the phototaxis are in common, 610 nm.5. coeruleus showed changes in its steady‐state swimming velocity induced with varying intensities of light (photokinesis). The cells swam fast in light regions but slowly in dark ones (positive photokinesis); the mean velocity of swimming was about 0.6 mm/s at 100 lx but reached about 1.0 mm/s at 50000 lx. The peak of the action spectrum for this photokinesis was about 680 nm.The organism is the first protozoan cell reported to show three types of photoresponse: photophobic response, phototaxis and photokinesis.
SITE‐DIRECTED MUTAGENESIS OF THE LH2 LIGHT‐HARVESTING COMPLEX OF Rhodobacter sphaeroides: CHANGING βLys23 TO Gin RESULTS IN A SHIFT IN THE 850 nm ABSORPTION PEAK
Authors: Fowler Gregory J. S. , Crielaardt Wim , Visschers Ronald W. , Grondelle Rienk van , Hunter C. Neil 
Published: January 2008

AbstractThe present study describes the construction of a Rhodobacter sphaeroides light‐harvesting (LH2) mutant in which the charged residue βSLys23 is changed by site‐directed mutagenesis to a Gin residue, and the characterization of the resulting mutant complex by a range of spectroscopic techniques. In the 77 K absorption spectrum of the mutant, the peak equivalent to the 850 nm peak in the wild‐type membrane is blue‐shifted by approximately 18 nm to 837 nm; except for this blue‐shift, the 77 K. fluorescence excitation and emission spectra and the circular dichroism spectrum of the mutant are very similar to the equivalent spectra from the wild‐type membranes, suggesting that the mutation βLys23 → Gin probably does not cause any major changes in the conformation or aggregation state of these membranes. Possible causes of the 18 nm blue‐shift in the absorption spectrum are discussed.
CAROTENOID‐TO‐BACTERIOCHLOROPHYLL SINGLET ENERGY TRANSFER IN CAROTENOID‐INCORPORATED B850 LIGHT‐HARVESTING COMPLEXES OF Rhodobacter sphaeroides R‐26.1
Authors: Frank Harry A. , Farhoosh Roya , Aldema Mila L. , DeCoster Beverly , Christensen Ronald L. , Gebhard Ronald , Lugtenburg Johan 
Published: January 2008

AbstractFour carotenoids, 3,4,7,8‐tetrahydrospheroidene, 3,4,5,6‐tetrahydrospheroidene, 3,4‐dihydrospheroidene and spheroidene, have been incorporated into the B850 light‐harvesting complex of the carotenoidless mutant, photosynthetic bacterium, Rhodobacter sphaeroides R‐26.1. The extent of π‐electron conjugation in these molecules increases from 7 to 10 carbon‐carbon double bonds. Carotenoid‐to‐bacteriochlorophyll singlet state energy transfer efficiencies were measured using steady‐state fluorescence excitation spectroscopy to be 54 ± 2%, 66 ± 4%, 71 ± 6% and 56 ± 3% for the carotenoid series. These results are discussed with respect to the position of the energy levels and the magnitude of spectral overlap between the S, (2′AJ state emission from the isolated carotenoids and the bacteriochlorophyll absorption of the native complex. These studies provide a systematic approach to exploring the effect of excited state energies, spectral overlap and excited state lifetimes on the efficiencies of carotenoid‐to‐bacteriochlorophyll singlet energy transfer in photosynthetic systems.
FLUORESCENCE AND CIRCULAR DICHROISM STUDIES ON THE PHYCOERYTHROCYANINS FROM THE CYANOBACTERIUM
Authors: Sai P. S. Maruthi , Siebzehnrübl S. , Mahajan S. , SCHEER H. 
Published: January 2008

AbstractTwo phycoerythrocyanin (PEC) fractions have been obtained from the phycobilisomes of the cyanobac‐terium Westiellopsis prolifica ARM 365. They have been characterized by absorption, fluorescence and circular dichroism spectroscopy. One of them is spectroscopically similar to a PEC trimer known from other organisms. Whereas efficient energy transfer from its violin (α‐84) to the cyanin (β‐84, 155) chromophores is efficient in the trimer (αβ it is impeded after dissociation to the monomer (α,β). A second fraction of PEC which we earlier termed PEC(X) (Maruthi Sai et al., Photochem. Photobiol.55,119–124, 1992), exhibited the spectral properties similar to that of the α‐subunit of PEC from Mastigocladus laminosus. With this highly photoactive fraction, the circular dichroism spectra of the violobilin chromophore in both photoreversible states were obtained.
STUDIES ON CHROMOPHORE COUPLING IN ISOLATED PHYCOBILIPROTEINS. IV. FEMTOSECOND TRANSIENT ABSORPTION STUDY OF ULTRAFAST EXCITED STATE DYNAMICS IN TRIMERIC PHYCOERYTHROCYANIN COMPLEXES*
Authors: Hucke Mathias , Schweitzer Gerd , Holzwarth Alfred R. , Sidler Walter , Zuber Herbert 
Published: January 2008

AbstractThe excited state dynamics of trimeric phycoerythrocyanin has been studied by two‐color femtosecond transient absorption spectroscopy with a time‐resolution better than 200 fs. Upon selective excitation of the short‐wavelength phycobiliviolin chromophore at 575 nm absorption bleachings are observed. An isotropic ultrafast decay of the initial bleaching of 585 ± 40 fs has been resolved at short detection wavelength (578 nm). Upon stepwise increase of the detection wavelength up to 617 nm, the bleaching showed a delayed rise above 593 nm with rrice=380–580 fs. All other isotropic kinetic components in this wavelength range were longer than 100 ps. The ultrafast component is discussed in terms of an energy transfer process from the α‐84 phycobiliviolin chromophore to the β‐84 chromophore in adjacent monomer subunits of the trimer. It is concluded that the β‐155 chromophore is the longest‐wavelength chromophore. Exciton relaxation between closely spaced chromophore pairs is discussed as an alternative interpretation for the ultrafast component.
DELAYED MICROSECOND LUMINESCENCE OF PHYCOBILISOMES
Authors: Frackowiak Danuta , Planner Alfons , Dudkowiak Alina 
Published: January 2008

AbstractThe time‐resolved luminescence spectra (in the microsecond range) of phycobilisomes and biliproteins in buffer and polymer matrix were measured in the temperature range from 8 K. to 293 K. Delayed luminescence located in the same spectral region as prompt fluorescence of investigated samples (DLF) and the long‐wavelength delayed emission in the720–760 nm range (DL1) was observed. The temperature and viscosity dependencies of DLF and DL1 luminescences were different, but both do not have uniexponential decays and are not quenched by oxygen. This means that delayed luminescence could be generated without the participation of the triplet states, or the chromophores could be shielded by protein against interaction with oxygen. The linear dependence of delayed luminescence on exciting light intensity shows that delayed luminescence is monophotonically induced.It seems that both DLF and DL1 are related to electron‐cation recombination, which yields excited singlet states. The DLF is emitted from the first excited singlet state of biliprotein chromophores and DL1 from the same state of the excimers or from the triplet state of some groups of chromophores. Ionization energy of chromophores can be lowered as a result of their interactions with the environment. Delay of emission is due to the trapping or solvation of electrons. Every type of biliprotein consisting of phycobilisomes possesses its own “trap” and can emit the DL. In the case of native phycobilisomes a competition between the excitation energy trapping and transfer occurs.
STRUCTURES OF THE BERGAMOTTIN PHOTOPRODUCTS
Authors: Martin M.‐T. , Valla A. , Giraud M. , Brouard J.‐P. , Morliere P. , Haigle J. , Santus R. 
Published: January 2008

AbstractThe extensive use of bergamot oil in perfumery and cosmetics led us to study the photoreactivity of 5‐geranoxypsoralen (bergamottin), the major chromophore in this oil. Structure determination of the bergamottin photoproducts was achieved using extensive NMR techniques including two‐dimensional NMR: 1H‐13C correlation by long‐range coupling, 1H‐1H correlation spectroscopy (COSY) and 1H‐1H COSY phase sensitive (COSYPH). Bergaptol is formed according to the well‐known fragmentation of allyl‐aryl ethers. The other photoproducts arise from an intramolecular [2 + 2] photocycloaddition and appeared as an equimolecular mixture of diastereomeric cyclobutyl derivatives. The relative configurations were determined by nuclear Overhauser effect analysis. These structures were further corroborated by X‐ray crystal analysis. The facile formation of an intramolecular cyclobutyl derivative in bergamottin might prevent the intermolecular cyclobutane adduct formation with pyrimidine DNA bases responsible, in part, for phototoxicity of psoralens.
THE PHOTOPHYSICS OF MONOMERIC BACTERIOCHLOROPHYLLS c AND d AND THEIR DERIVATIVES: PROPERTIES OF TRIPLET STATE AND SINGLET OXYGEN PHOTOGENERATION AND QUENCHING
Authors: Krasnovsky A. A. , Cheng P. , Blankenship R. E. , Moore T. A. , Gust D. 
Published: January 2008

AbstractMeasurements of pigment triplet‐triplet absorption, pigment phosphorescence and photosensitized singlet oxygen luminescence were carried out on solutions containing monomeric bacteriochlorophylls (Bchl) c and d, isolated from green photosynthetic bacteria, and their magnesium‐free and farnesyl‐free analogs. The energies of the pigment triplet states fell in the range 1.29‐1.34 eV. The triplet lifetimes in aerobic solutions were200–250 ns; they increased to 280 pL 70 us after nitrogen purging in liquid solutions and to 0.7‐2.1 ms in a solid matrix at ambient or liquid nitrogen temperatures. Rate constants for quenching of the pigment triplet state by oxygen were (2.0‐2.5) × 109 M−1 s−1. which is close to 1/9 of the rate constant for diffusion‐controlled reactions. This quenching was accompanied by singlet oxygen formation. The quantum yields for the triplet state formation and singlet oxygen production were55–75% in air‐saturated solutions. Singlet oxygen quenching by ground‐state pigment molecules was observed. Quenching was the most efficient for magnesium‐containing pigments, kq= (0.31‐1.2) × 109 M−1 s−1. It is caused mainly by a physical process of singlet oxygen (1O2,) deactivation. Thus, Bchl c and d and their derivatives, as well as chlorophyll and Bchl a, combine a high efficiency of singlet oxygen production with the ability to protect photochemical and photobiological systems against damage by singlet oxygen.
ULTRAVIOLET RESONANCE RAMAN SPECTRA OF PHYTOCHROME: A COMPARISON OF THE ENVIRONMENTS OF TRYPTOPHAN SIDE CHAINS BETWEEN RED LIGHT‐ABSORBING AND FAR‐RED LIGHT‐ABSORBING FORMS
Authors: TOYAMA AKIRA , NAKAZAWA MIKI , MANABE KATSUSHI , TAKEUCHI HIDEO , HARADA ISSEI 
Published: January 2008

AbstractUltraviolet resonance Raman spectra of phytochrome in the red light‐absorbing form (Pr) and the far‐red light‐absorbing form (Pfr) are reported. The spectra excited at 240‐nm provide structural information about the protein part of phytochrome. The protein contains only a very small amount of β‐sheet structure and most of the tyrosine side chains are located in hydrophobic environments. Indole rings of tryptophan (Trp) interact with neighboring groups in the Pr form and these interactions become weaker with the conversion from Pr to Pfr. Some Trp side chains of Pfr are surrounded by aliphatic groups but such is not the case in Pr. These changes in the environment occur at the same time as changes in orientation of Trp side chains. Our observations suggest that interactions between Trp residues and the tetrapyrrolic chromophore occur in the Pr form and that the strength of these interactions diminishes in the Pfr form.
LIPID PHASES IN RENAL BRUSH BORDER MEMBRANES REVEALED BY LAURDAN FLUORESCENCE*
Authors: Levi Moshe , Wilson Paul V. , Cooper Otis J. , Gratton Enrico 
Published: January 2008

AbstractSteady‐state fluorescence properties of 6‐dodecanoyl‐2‐dimethylaminonapththalene (Laurdan) have been used to determine the coexistence of separate lipid‐phase domains in apical brush border membrane vesicles isolated from the rat renal cortex. The temperature dependence of generated polarization has been utilized to quantitate the lipid phases. Finally, the effect of cholesterol enrichment on these parameters has been studied. The results indicate the coexistence of lipid‐phase domains in brush border membranes based on the values of the generalized polarization and assuming that the membrane state can be described by coexistence of gel and liquid crystalline state. At 37°C, approximately19–32% of the brush border membrane lipids are in the gel phase, and cholesterol enrichment causes a further concentration‐dependent increase in the gel phase of brush border membrane lipids.
USE OF LAURDAN FLUORESCENCE IN STUDYING PLASMA MEMBRANE ORGANIZATION OF POLYMORPHONUCLEAR LEUKOCYTES DURING THE RESPIRATORY BURST*
Authors: Fiorini R. , Curatola G. , Kantar A. , Glorgi P. L. , Gratton E. 
Published: January 2008

AbstractThe changes in plasma membrane polarity of polymorphonuclear leukocytes (PMN) during the activation of the respiratory burst were investigated by measuring the steady‐state fluorescence emission spectra of 2‐dimethylamino(6‐lauroyl) naphthalene (Laurdan), which is known to be incorporated at the hydrophobic‐hydro‐philic interface of the bilayer, displaying spectral sensitivity to the polarity of its surroundings. Laurdan shows a marked steady‐state emission blue shift in nonpolar solvents, with respect to polar solvents. Our results show a blue shift of the fluorescence emission spectra of Laurdan during activation of PMN with phorbol myristate acetate or AT‐formyl‐methionyl‐leucyl‐phenylalanine. These results suggest that the activation of the respiratory burst of PMN is accompanied by a decrease in polarity in the hydrophobic‐hydrophilic interface of the plasma membrane.