bluuebunny/crossref_metadata_2025_split huggingface dataset:
BIOSYNTHESIS AND ASSEMBLY OF PURPLE MEMBRANE OF HALOBACTERIUM HALOBIUM S9: LIGHT STIMULATION OF BACTERIORHODOPSIN FORMATION
Authors: Konishi Tetsuya , Seki Mayumi 
Published: January 2008

Abstract— The effect of light on purple membrane biogenesis in Halobacterium halobium S9 strain was investigated. When bacteria were grown in the dark, the 570nm absorption due to bacteriorhodopsin increased more slowly than under illumination, but eventually after longer incubation, reached the same level as that seen in the illuminated culture.Analysis of membrane fractions by sucrose density gradient centrifugation revealed that two different membrane fractions, containing purple and brown membrane could be detected in the exponential growth phase. Another fraction whose density was higher than that of purple membrane, disappeared concomitantly with the increase in purple membrane and brown membrane, indicating that it may be related to purple membrane formation.HPLC analysis of membrane proteins showed that there was no significant difference in de novo synthesis of bacterio–opsin between dark and illuminated cultures. This led us to conclude that light stimulated retinal binding to bacterio–opsin and/or retinal biosynthesis rather than bacterio–opsin synthesis. Bacteriorhodopsin seemed to form the brown membrane fraction first, which then spontaneously reorganized into purple membrane.When incorporated in liposomes, bacteriorhodopsin in brown membrane was found to have rather higher proton pump activity than that in purple membrane. The H+ pumping activity was quite heat labile. This and the CD spectra indicated that bacteriorhodopsin in brown membrane might exist without forming normal timer unit.
SOLID PHASE PHOTOREDUCTION OF METHYLVIOLOGEN ON CELLULOSE SENSITIZED BY TRIS(2,2′‐BIPYRIDYL)RUTHENIUM COMPLEX
Authors: Kaneko Masao , Yamada Akira 
Published: January 2008

Abstract–Methylviologen (MV2+) adsorbed on cellulose could be reduced photochemically in the solid phase sensitized by tris(2,2′‐bipyridyl)ruthenium(II) complex, [Ru(II)(bpy)3], using disodium ethylene‐diaminetetraacetic acid (Na2EDTA) as a reducing agent. Formation of the cation radical (MV +.) was confirmed by visible and EPR spectra. The MV+. formed on cellulose was remarkably stable against air oxidation and rapidly accumulated even by the irradiation under air. Water adsorbed on the cellulose greatly retarded the photoreaction. Action spectrum showed that the excitation of Ru(II)(byp)3 is responsible for the photochemical reaction. The quenching of the emission from Ru(II)(bpy)*3 by MV2+. indicated that a primary photochemical reaction occurs between Ru(II)(bpy)*3 and MV2+. The main reaction path is the reduction of MV2+ by Ru(II)(bpy)3, giving MV+. and Ru(III)(bpy)3, followed by the reduction of Ru(III)(bpy)3 to Ru(II)(bpy)3 with Na2EDTA, which in turn is oxidized to give carbon dioxide.
A STUDY OF THE PHOTOCHEMICAL PROPERTIES OF SOME CINNAMATE SUNSCREENS BY STEADY STATE AND LASER FLASH PHOTOLYSIS
Authors: Morlière P. , Avice O. , Melo T. Sa E , Dubertret L. , Giraud M. , Santus R. 
Published: January 2008

AbstractThe E⇄ Z photoisomerization of 4′‐methoxycinnamates, used as sunscreens in cosmetics, has been studied by steady state and laser flash photolysis, in aqueous and organic solutions. Photoisomerization quantum yields are found to be fairly high (˜0.5‐1), although no intermediate is detected upon laser flash photolysis. Cinnamates are not photodynamic sensitizers but are able to quench the 8‐methoxy‐psoralen and 5‐methoxypsoralen triplets which produces E → Z isomerization.
EFFECT OF PHYTOCHROME ON THE BIOSYNTHESIS OF ACYCLIC AND CYCLIC CAROTENOIDS IN HIGHER PLANTS
Authors: Grumbach Karl H. 
Published: January 2008

Abstract—Radish plants were grown in the presence of three different herbicides that interfere with the formation of the normal range of cyclic carotenoids, leading to an accumulation of acyclic biosynthetic intermediates, mainly phytoene (SAN 6706 and amitrole) and zeta‐carotene (3852). Plants were then irradiated by four different light programs in order to gain more insight into the first steps of carotenoid biosynthesis and their control by light and phytochrome. In all cases, herbicide‐treated and control, carotenoid biosynthesis was greatly enhanced by red light consistent with an effect of phytochrome on the early steps of the pathway. However, similar enhancement was also obtained after treatment with far‐red light. Indeed with SAN 6706‐treated plants synthesis of phytoene was stimulated to a much greater extent by far‐red light given alone, than by red light. The involvement of phytochrome in the regulation of carotenoid biosynthesis appears not to be as simple as previously supposed.
LIQUID PHASE ELECTRON SPIN‐ECHO STUDIES: DIRECT DETECTION OF THE TRANSVERSE RELAXATION TIME OF PHOTOPRODUCED TETRAMETHYLBENZIDINE CATION IN AQUEOUS MICELLAR SOLUTIONS OF SODIUM DODECYLSULFATE
Authors: Narayana P. A. , Kevan Larry 
Published: January 2008

AbstractElectron spin echo detection of laser photogenerated tetramethylbenzidine cation in liquid sodium dodecylsulfate micellar solutions at room temperature is reported. The phase memory time is 180 ns which can be identified with the transverse relaxation time. Deuteration effects on the phase memory time indicate that the cation interacts more strongly with surfactant molecules than with water molecules.
PICOSECOND FLUORESCENCE STUDIES OF P700‐ENRICHED PARTICLES OF SPINACH CHLOROPLASTS
Authors: Kamogawa Keui , Morris John M. , Takagi Yoshihiro , Nakashima Nobuaki , Yoshihara Keitaro , Ikegami Isamu 
Published: January 2008

AbstractDynamic properties of the picosecond fluorescence of highly enriched reaction‐center particles of photosystem I (8 ‐ 10 chlorophylls/P700) prepared from spinach have been investigated. The number (N) of photons used to excite chlorophyll molecules per reaction center was controlled between 0.06 and 80. The 1/e lifetime was ca. 25 ps for N1. which is much shorter than previously measured lifetimes of photosystem I particles. The initial fluorescence intensity saturated at higher excitation intensities (N≲ 1). This was interpreted in terms of interaction and annihilation among excited chlorophyll molecules which occur almost entirely within the duration of a laser flash. The spectrum‐resolved fluorescence decay was faster at 690 than at 680 nm. This implies that two kinds of antenna chlorophylls, apart from and in close proximity to P700, have different lifetimes. Upon heat treatment a component with a much longer fluorescence decay time was observed. The growth of this component upon heat treatment at increasing temperatures showed a correlation with a decrease in the amount of P700 that could be photooxidized.
ULTRAVIOLET RADIATION INHIBITS BOTH ACCESSORY CELL AND RESPONDER T CELL FUNCTION IN THE PROLIFERATIVE RESPONSE TO HAPTENATED‐SELF
Authors: Pretell Judith O. , McAuliffe Daniel J. , Parrish John A. 
Published: January 2008

AbstractUltraviolet‐irradiated, hapten‐conjugated stimulator cells were unable to generate a proliferative response in unirradiated autologous T cells. The inhibition of the hapten‐specific response was found to depend on both the dose and waveband of UV radiation used as well as the timing of irradiation with regard to haptenation. UVC (254 nm) was 10‐fold more effective in eliminating the response than UVB (290–320 nm) which in turn was 104‐fold more effective than UVA (320–400 nm) with regard to the amount of incident energy required. Incident doses of UV lower than those within each waveband which virtually eliminated the response resulted in partial inhibition. This inhibition was significantly greater if UV radiation followed haptenation rather than preceding it, suggesting that UV radiation may have caused some loss of antigenicity. The interaction of UV radiation with hapten did not lead to enhanced phototoxicity; survival curves of viable cells placed in culture after the same dose and waveband of UV, either before, after or without haptenation, were similar. Independent experiments revealed that irradiation of the T cells with lower doses of UV than those required to reduce the stimulation 50% with irradiated haptenated stimulator cells, was itself directly inhibitory of their response to unirradiated, TNP‐conjugated adherent cells.
THE UV PROTEIN FLUORESCENCE OF PURPLE MEMBRANE AND ITS APOMEMBRANE
Authors: Acuña A. U. , González J. , Lillo M. P. , Otón J. M. 
Published: January 2008

AbstractThe ultraviolet fluorescence of the purple membrane of H. halobium and its apomembrane was characterized by measuring emission spectra, polarization, decay lifetimes and the changes induced by pH and temperature. The fluorescence quantum yields of the two membranes are 0.024 × 0.003 and 0.17 × 0.03, respectively. The emission, which shows lifetimes in the 0.4 to 4 ns range, was assigned to heterogeneous populations of emitters, consisting, probably, of two tryptophans in the purple membrane and seven or eight residues in the apomembrane. Acrylamide quenching experiments showed that the accessibility of this neutral quencher to the fluorophors is reduced greatly in both membranes. Fluorimetric methods were also used in an attempt to monitor the purple complex reconstitution process. It was concluded that the fluorescence quantum yields of any monomers, dimers and trimers present in the partially reconstituted membranes should be very similar.Finally, based on the spectroscopic results and on specific folding patterns of the seven α‐helical regions of bacteriorhodopsin (Stoeckenius and Bogomolni, 1982), it is proposed that Trp 137, Trp 138 (and perhaps Trp 10) of the protein molecule are the most plausible fluorophors in the purple membrane. It is also suggested that the protein in the apomembrane takes a more open configuration which is permeable to small ions and molecules.
FLASH INDUCED OSCILLATION OF THE LOW TEMPERATURE THERMOLUMINESCENCE BAND Zv IN CHLOROPLASTS
Authors: Vass Imre , Rzsa Zsuzsa , Demeter Sndor 
Published: January 2008

AbstractUsing preilluminating flashes at 2°C prior to continuous excitation of isolated chloroplasts at ‐80°C, a period‐four oscillation with maxima at the 0th, 4th and 8th flashes was observed in the amplitude of the thermoluminescence band Zv. Inactivation of the water‐splitting system by hydroxylamine‐ or Tris‐treatments greatly diminished the Zv band. On the other hand, its amplitude was not considerably affected by the addition of inhibitory concentration of DCMU. On the basis of the results, the possible origin of the Zv band is discussed.
PHOTOHEMOLYTIC LESIONS: STOICHIOMETRY OF CREATION BY PHLOXINE B
Authors: Valenzeno Dennis Paul 
Published: January 2008

AbstractThe uptake of the halogenated fluorescein sensitizers, Rose Bengal and phloxine B, by erythrocyte membranes was measured as a function of incubation time. Ghost membranes concentrate the sensitizers to levels greatly in excess of the sensitizer concentration in the suspension medium. Most of the uptake occurs in the first hour and is virtually complete by four hours. It is not significantly affected by stirring under the present conditions. The distribution of sensitizer cannot be explained as partitioning between immiscible solvents. Rather the data fits the Freundlich adsorption isotherm over a wide range of sensitizer concentrations and ghost protein values. Photohemolysis experiments were performed using sensitizer concentrations and incubation times similar to those used in the sensitizer uptake studies. The kinetics of lysis were found to vary with the 1.2 power of sensitizer concentration using PB. When combined with the uptake data for this sensitizer, these results imply that photohemolytic lesions in the red cell membrane are formed by the action of two sensitizer molecules.
KINETICS OF STACKING INTERACTIONS IN FLAVIN ADENINE DINUCLEOTIDE FROM TIME‐RESOLVED FLAVIN FLUORESCENCE
Authors: Visser A. J. W. G. 
Published: January 2008

AbstractThe time dependence of the fluorescence of flavin adenine dinucleotide (FAD) was measured with a subnanosecond‐resolving fluorometer. In contrast to the fluorescence decay of FMN, the decay of FAD was proved to be nonexponential. The time‐dependent fluorescence of FAD can be interpreted by assuming an equilibrium between closed and open conformers in the ground state. The rate constant for folding in the excited state and the fluorescence lifetime of the intramolecular complex could be evaluated from analysis of the observed fluorescence decay. The results on FAD were compared to those on NADH obtained earlier.
A MULTICHANNEL TRANSIENT SPECTRUM ANALYSER FOR ABSORPTION CHANGES MEASUREMENT WITH ONE MICROSECOND RESOLUTION
Authors: Furuya Masaki , Inoue Yasunori , Maeda Yoshio 
Published: January 2008

AbstractA custom‐designed photometer for recording flashlight‐induced transient absorbance spectra with microsecond time resolution in the wavelength range from 350 to 800 nm with 0.5 nm resolution is reported. The apparatus is equipped with two 600 ns half‐width pulse (output = 400 mJ) tunable dye lasers for double‐flash analysis and an optical multichannel analyser having a silicon intensified target detector. Measuring light from a tungsten‐halogen lamp is passed through the sample, dispersed into a spectrum and focused on the head of the detector. A transient spectrum is measured over a range of 330 nm simultaneously by applying high voltage to the detector for the desired interval. The delay from the actinic flash to applying the high voltage can be controlled electronically. Distortion caused by scattering of the actinic flash under optimal conditions is negligible within 1.5 is after the flash peak. Detector linearity reaches about 104 and a noise level of less than ±0.005A can be achieved without data accumulation. This apparatus is applicable not only to transparent samples but to turbid ones with 100 μs resolution.
DNA ASSOCIATED WITH THE CELL MEMBRANE IS INVOLVED IN THE INHIBITION OF THE SKIN REJECTION RESPONSE INDUCED BY INFUSIONS OF PHOTODAMAGED ALLOREACTIVE CELLS THAT MEDIATE REJECTION OF SKIN ALLOGRAFT
Authors: Perez Maritza I. , Yamane Yasuhiro , John Lori , Gasparro Francis P. , Edelson Richard L. 
Published: January 2008

AbstractCell membrane DNA (cmDNA) is a form of DNA located on the surface of human and murine T‐cells. It has recently been characterized as a target for photomodification by 8‐methoxypsoralen (8‐MOP) and long‐wave ultraviolet light (UV‐A). Whereas 8‐MOP itself is biologically inert, photoactivated 8‐MOP is covalently bound to pyrimidine bases in DNA. We have investigated the possible involvement of cmDN A photomodification in the induction of the suppression of skin allograft rejection in BALB/c mice preimmunized with 8‐MOP/UV‐A photodamaged alloreactive cells which mediates this allograft rejection. This suppression is demonstrated by inhibition of delayed‐type hypersensitivity (DTH) and mixed leukocyte culture (MLC) responses. Splenocytes from BALB/c mice undergoing rejection of CBA/j skin graft which contained an expanded population of the effector T lymphocytes that mediate the rejection were treated with DNAse to remove cmDNA before or after treatment with 8‐MOP and UV‐A prior to infusion into naive BALB/c recipients. Mice that received pretreated effector cells were tested for MLC responses to CBA/j or B10 alloantigens before and after the DTH response. The DTH response of all groups of pretreated BALB/c mice to the relevant alloantigen was specifically suppressed as compared with the response of control mice. However, adoptive transfer of the suppression of the DTH response was optimally demonstrable only in syngeneic recipients of cells from donor mice treated with photodamaged alloreactive cells. Also, splenocytes from BALB/c mice immunized with photodamaged alloreactive cells demonstrated highly significant hyporesponsiveness and suppression of the MLC response of naive mice to the relevant alloantigen in the case of the primary MLC response, and to both alloantigens in the secondary MLC response which was totally eliminated by prior pretreatment of these effector cells with DNAse. Therefore, it appears that the suppression of the DTH response can be induced by pretreatment of the effector cells with DNAse and/or 8‐MOP and UV‐A but is adoptively transferable optimally only from mice which are recipients of photodamaged alloreactive cells. Moreover, the effectiveness of this treatment is decreased by prior removal of cmDNA from these cells. The presence of cmDNA is necessary for induction of suppression of the primary and secondary MLC responses in mice treated with photodamaged cells of allograft rejection.
ESTIMATION OF THE OPTICAL PARAMETERS AND LIGHT GRADIENTS IN LEAVES: MULTI‐FLUXversusTWO‐FLUX TREATMENT
Authors: Remisowsky Alexander Martinez v. , McClendon John H. , Fukshansky Leonid 
Published: January 2008

AbstractParameters of light propagation in plant leaves‐absorption and scattering coefficients, asymmetry of scattering‐have been estimated on the basis of measured transmission and remission as well as internal fluxes. This estimation has been carried through by solving the inverse problem of the 4‐flux radiative transfer‐a theory considering forward and backward diffuse as well as directed components of the overall radiation in a multiply scattering sample. Using the gained parameters, light flux gradients in a two‐layered model leaf have been calculated at different wavelengths. Monte Carlo simulation of absorption spectra performed with the parameters obtained with this treatment is in a good agreement with experimental spectra, thus substantiating the theory. Parallel calculations with the two‐flux (Kubelka‐Munk) theory provide an estimation of the accuracy and applicability of this more simple treatment. Calculations have been performed for two different plants.
REAL TIME COMPUTER‐CONTROLLED TRACKING OF MOTILE MICROORGANISMS
Authors: Häder Donat‐P. , Lebert Michael 
Published: January 2008

Abstract— A hardware and software system is described which is capable of automatically following the movement of microorganisms and analyzing the deviation of individuals in a population from a predefined direction. The image of the moving organisms is viewed by a video camera, digitized in real time and stored in a dedicated video memory holding 512 times 256 pixels with 64 grey levels. A microcomputer has access to this video memory via four parallel ports. The software analyzes the position of an organism selected randomly and attempts to follow its track for a predefined period of time. If successful, it calculates the direction of movement and stores the data in a file for statistical analysis.Using this system, the movement of populations of the unicellular flagellate, Euglena gracilis, in unilateral and bilateral light beams has been studied and compared with the dark behavior. When irradiated from two opposite light sources of equal fluence rates half of the population swims towards either light source. However, when the light sources are oriented at an angle of 90° to each other the cells move on the resultant away from the light. These results confirm the shading hypothesis for negative phototaxis.
FLUORESCENCE QUENCHING FOR FLAVINS INTERACTING WITH EGG WHITE RIBOFLAVIN‐BINDING PROTEIN
Authors: Bystra‐Mieloszyk K. , Balter A. , Drabent R. 
Published: January 2008

Abstract— The effect of flavin structure variation upon the binding process of flavin to hen egg white riboflavin was studied using fluorescence methods for formylmethylflavin (FMF), riboflavin (RF) and flavomononucleotide (FMN).Measurements of flavin fluorescence intensities (steady state and phase‐sensitive) and lifetimes were performed in a variety of RBP concentrations and temperatures (4 to 40°C). No fluorescence of flavoproteins was detected, while the fluorescence of flavins was found to be quenched by RBP. The overall quenching process is dominated by the static quenching (about 88%) due to the flavoprotein complex formation in the ground state, presumably a charge transfer complex.
THE OPTICAL PROPERTIES OF ADENINE FROM 1.8 TO 80 eV*
Authors: Arakawa E. T. , Emerson L. C. , Juan S. I. , Ashley J. C. , Williams M. W. 
Published: January 2008

AbstractExperimental measurements of the optical reflectance of solid adenine films have been obtained for photon energies extending from 1.8 to 80 eV. From these data we have established the complex index of refraction, the complex dielectric function, and the energy‐loss function Im(‐l/). Structure in the dielectric functions are ascribed to * transitions at photon energies less than ~9 eV and to * transitions at higher energies. A broad peak in the energy‐loss function near 24 eV is associated with a collective resonance involving all the valence electrons. Sum rule calculations are used to demonstrate the overall consistency of the data.
WAVELENGTH DEPENDENCE OF THE FORMATION OF SINGLE‐STRAND BREAKS AND BASE CHANGES IN DNA BY THE ULTRAVIOLET RADIATION ABOVE 150 nm
Authors: Hidea Kotaro , Hayakawa Yoshihiko , Ito Atsushi , Kobayashi Katsumi , Ito Takashi 
Published: January 2008

AbstractThe wavelength dependence of the formation of two types of DNA damage, single‐strand breaks and base changes, was investigated in the UV region from 150 nm to 254 nm using superhelical closed circular (form I) colicin El DNA with synchrotron radiation. Single‐strand breaks were measured by agarose gel electrophoresis as a direct conversion of form I DNA to form II DNA (open circular). Base damages were defined as sensitive sites to a crude extract of endonuclease from Micrococcus luteus. They also were estimated using the same conversion, from form I to form II after the DNA was treated with endonuclease. The fluence‐effect relationship could be fitted by a simple exponential function for both types of damage. Action spectra were constructed based on the reciprocal of the 37% fluence. The action spectrum for strand breaks increased rather monotonically over three decades from 254 nm to 150 nm in a logarithmic scale, while that for base damages showed a breaking point at 190 nm, being relatively flat above 190 nm. The characteristics of the action spectra are compared with the absorption spectra of the DNA and its main chain moiety calculated on the basis of data on calf thymus DNA and synthetic polynucleotides. Our main conclusions are (1) that the majority of single‐strand breaks were induced by the absorption of photon in the sugar‐phosphate group in the vacuum‐UV region and (2) that the base changes were induced equally well by absorption in the vacuum‐UV and in the far‐UV region.
ACTION SPECTRA IN ULTRAVIOLET WAVELENGTHS (150‐250 nm) FOR INACTIVATION AND MUTAGENESIS OF Bacillus subtilis SPORES OBTAINED WITH SYNCHROTRON RADIATION
Authors: Munakata N. , Hidea K. , Kobayashi K. , Ito A. , Ito T. 
Published: January 2008

Abstract Bacillus subtilis spores were exposed in vacuo to monochromatic UV radiation from synchrotron radiation in the wavelength range of 150 nm to 250 nm. Survival and frequency of mutation to histidine‐independent reversion were analysed for three types of spores differing in DNA‐repair capabilities. UVR spores (wild‐type DNA repair capability) exhibited nearly equal sensitivity to the lethal effects of far‐UV (220 nm and 250 nm) and of vacuum‐UV radiation (150 and 165 nm), but showed marked resistance to 190 nm radiation. UVS spores (excision‐repair and spore‐repair deficient) and UVP spores (a DNA polymerase I‐defective derivative of UVS) exhibited similar action spectra; pronounced sensitivity at 250 and 220 nm, insensitivity at 190 nm and a gradual increase of the sensitivity as the wavelength decreased to 165 nm. In all strains, the action spectra for mutation induction paralleled those for the inactivation, indicating that vacuum‐UV radiation induced lethal and mutagenic damages in the spore DNA. The insensitivity of the spores to wavelengths around 190 nm may be explicable by assuming that radiation is absorbed by materials surrounding the core in which DNA is situated.