bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE MODE OF INTERACTION BETWEEN BLUE (UV) LIGHT PHOTORECEPTOR AND PHYTOCHROME IN ANTHOCYANIN FORMATION OF THE SORGHUM SEEDLING
Authors: Drumm H. , Mohr H. 
Published: January 2008

AbstractTwo non‐photosynthetic photoreceptors (phytochrome and a blue light photoreceptor) are involved in light‐mediated anthocyanin synthesis in the mesocotyl of Sorghum seedlings. The present study was undertaken to investigate the kind of interaction between phytochrome and the blue light photoreceptor. The data show that phytochrome (Pfr) can only act once a blue light effect has occurred. On the other hand, the blue light effect cannot express itself without Pfr. It is concluded that there is an obligatory dependency (or sequential interaction) between the blue light effect and the light effect occurring through phytochrome, although the blue light photoreaction per se is not affected by the presence or absence of phytochrome. The latter statement is based on the results of dichromatic experiments, i.e. simultaneous, high fluence rate irradiation with two kinds of light. Blue light can be replaced by UV light. It is not clarified yet whether the effect of blue and UV light is due to the same photoreceptor.
PICOSECOND LASER PHOTOLYSIS OF SQUID RHODOPSIN AT ROOM AND LOW TEMPERATURES
Authors: Shichida Yoshtnori , Kobayashi Takayoshi , Ohtani Hiroyuki , Yoshizawa Tôru , Nagakura Saburo 
Published: January 2008

Abstract. Squid rhodopsin extracted with 2% digitonin (pH 10.5 or 7.0) was excited with a 347 nm light pulse from a mode‐locked ruby laser at room temperature. Within 19 ps after the excitation, absorbance at 430 nm due to hypsorhodopsin increased and subsequently decreased with a decay time of 45 ± 10 ps. Absorbance at 550 nm due to bathorhodopsin increased with a rise time of 50 ± 10 ps. These results are the first observations of hypsorhodopsin at room temperature and clearly show that hypsorhodopsin is a precursor of bathorhodopsin which has been considered to be the earliest photoproduct in the photobleaching process of rhodopsin.Hypsorhodopsin appeared with a rise time of 70 ± 10 ps at 421 nm at liquid nitrogen temperature without any bathorhodopsin being observed during the formation of hypsorhodopsin. An experiment using an N2 laser showed that squid bathorhodopsin converted to lumirhodopsin with a decay time of about 300 ns at room temperature.
THE CHEMISTRY AND BIOLOGY OF BACTERIAL LIGHT EMISSION
Authors: Hastings J. W. 
Published: January 2008

Abstract—Bioluminescent bacteria may be isolated from sea water, and grown on a medium containing fish (or meat or yeast) extract. Cells harvested at the peak of luminescence can be lysed osmotically, releasing into the medium the soluble enzyme bacterial luciferase, which catalyzes the bioluminescent oxidation of reduced riboflavin 5′‐phosphate and long chain aldehyde by molecular oxygen. Luciferase is the simplest possible heterpolymeric protein, with an α (catalytic, 42,000 daltons)‐β (regulatory, 37,000 daltons) dimeric structure. Luciferase is not constitutive; it is induced by a substance produced by the bacteria themselves and excreted into the medium. Control also involves repression (glucose) and cyclic nucleotides.Recent work has resulted in the characterization of an intermediate in the light emitting reaction postulated to be luciferase‐bound 4a‐peroxy‐dihydro FMN. The final steps in the in vitro light‐emitting reaction involve reaction of this peroxy intermediate with aldehyde in a mixed function oxidase‐type reaction, yielding an excited luciferase‐flavin and long chain acid. The excited state is postulated to be the luciferase‐bound 4a‐hydroxy‐dihydro‐FMN. Although the identity of the in vivo aldehyde, its localization and its metabolism is unknown, studies with mutants which fail to synthesize aldehyde suggest that the 14 carbon fatty acid is a precursor. Moreover, although bacterial luciferase is highly soluble (200 mg ml‐1 in aqueous solution) there is recent evidence from our laboratory and others that its function may involve the cytoplasmic membrane.The function of light emission is of particular interest since a considerable amount of energy is involved; assuming a quantum yield of 10%, the cell foregoes the production of about 60 ATP molecules per photon. A fully induced cell emits about 104 quanta/s and about 20% (!) of the oxygen consumption of the cell has been estimated to go via the light emitting pathway. One function is in light organs of higher organisms, where they occur as symbionts. The inducible (and repressible) nature of the luminescent system may be appreciated in terms of ecological options; the bacteria may be biologically very versatile. Induction by an inducer produced by the bacteria themselves would occur only under conditions where it accumulates, as in a luminous organ of a host. In the open ocean such an accumulation does not occur; the luminous system would thus not be synthesized and energy loss via luminescence is averted, allowing the bacteria to compete in an alternate “life style”.
MEDIATION OF LIGHT‐INDUCED CHANGES IN PINEAL RECEPTOR AND SUPPORTING CELL NUCLEI AND NUCLEOLI IN STEELHEAD TROUT (SALMO GAIRDNERI)
Authors: Hafeez M. A. , Wagner H. H. , Quay W. B. 
Published: January 2008

Abstract— Mediation of the chronic effects of differences in environmental illumination on pineal photoreceptor and adjacent supporting cells was studied in two experiments using larval trout. Experiment 1 had 7 groups exposed to controlled lighting conditions for 14 months: (1) constant darkness (DD); (2) natural photocycles (LD) followed by constant light (LL); (3) natural photocycles (LD); (4) LD fluorescent light; (5) LD blue (400–525nm) light; (6) LD green (500–612nm) light; and (7) LD red (600–750 nm) light. In Experiment II the fish were exposed to LL for 27–28 days, following 10 months in DD and one of five surgical manipulations: (1) pineal masked; (2) pineal sham‐masked; (3) blinded; (4) blinded + pineal masked; (5) blinded + pineal sham masked.Nuclei and nucleoli of pineal receptor and supporting cells were largest in fish raised in DD. LL or LD cycles, and light of either narrow or broad spectral range, were not notably different in their chronic effects on receptor cell nuclei and nucleoli. However, supporting cell nuclei and nucleoli were smallest in LL. Blinding and pineal masking demonstrated that: (1) pineal receptor cell nuclei and nucleoli were affected by chronic incident light in the pineal region but not by photic or visual influences via the lateral eyes; and conversely, (2) pineal supporting cell nuclei and nucleoli were affected by chronic photic input only via the lateral eyes. The results suggest the possible presence of a cellular comparator system in which photic inputs from lateral eyes and pineal affect separately and respectively the adjacent supporting and receptor cells of the pineal organ.
SEDIMENTATION ANALYSIS OF DNA PHOTOOXIDIZED IN THE PRESENCE OF THIOPYRONINE
Authors: Triebel H. , Bär H. , Jacob H‐E. , Sarfert E. , Berg H. 
Published: January 2008

Abstract. Illumination of single‐stranded φ×174 phage DNA with visible lightλ > 500 nm) in the presence of the sensitizer thiopyronine results in both chain scissions detectable by velocity sedimentation in neutral medium and in alkali‐labile bonds which yield secondary strand breaks after alkaline treatment. Compared with the generation of primary strand breaks, the formation of alkali‐labile sites seems to be the predominant reaction.Photodynamic treatment of homogeneous double‐stranded Ta, phage DNA leads to changes in the overall conformation of DNA as revealed by an initial increase of the sedimentation coefficient. The simultaneous occurrence of different effects (decrease of molecular weight, increase of effective DNA flexibility) is particularly evident from changes in the sedimentation coefficient distribution. The fact that both processes influence the sedimentation behaviour questions the common procedure of calculating double‐strand break numbers from sedimentation coefficient distributions on the basis of s#‐M relations which are valid for intact DNA only.Photooxidized double‐stranded DNA exhibits an increased sensitivity against shear forces.
BIPHASIC ENERGY CONVERSION KINETICS AND ABSORBANCE DIFFERENCE SPECTRA OF PHOTOSYSTEM II OF CHLOROPLASTS. EVIDENCE FOR TWO DIFFERENT PHOTOSYSTEM II REACTION CENTERS
Authors: Melis A. , Duysens L. N. M. 
Published: January 2008

Abstract— The continuous illumination induced kinetics of photochemical energy conversion at system II have been measured with isolated and 3‐(3, 4‐dichlorophenyl)‐l, l‐dimethylurea (DCMU) poisoned chloroplasts by means of absorbance difference spectroscopy in the UV and by the area growth over the fluorescence induction curve at room temperature. An optimal set of conditions was found in order to isolate absorbance changes caused by the reduction of the primary electron acceptor Q of PS II by suppressing other electron transfer processes. The light induced kinetics of Q‐ accumulation in the absorbance change measurements were found to be biphasic and strictly correlated with the kinetics of the area growth measured under the same conditions. From the resolution of the biphasic kinetics at different wavelengths in the UV region of the spectrum, it was found that both kinetic components in the system II photochemistry involve the reduction of a plastoquinone molecule to its plastosemiquinone anion. From the two kinetic components one was fast and non‐exponential and the other relatively slow with an exponential time course. The initial rate difference in the kinetics of the two components was by a factor of approximately 3. A difference by a factor of about three was also found in the flash saturation curves of the two kinetic components.The results are explained by the hypothesis that in higher plant chloroplasts there are system II reaction centers embedded in a large pigment matrix with statistical energy transfer, and system II reaction centers embedded in separate, in terms of excitation energy transfer, units. The effective absorption cross section per reaction center for the centers in the statistical pigment bed is approximately 3 times larger than that of the reaction centers in the separate system II units. The two types of system II reaction centers have different yields of excitation trapping and charge stabilization properties.
DETERMINATION OF THE KINETICS OF THE BACK REACTION OF PHOTOSYSTEM II IN THE PRESENCE OF 3–(3,4‐DICHLORPHENYL)‐1,1‐DIMETHYLUREA FROM LUMINESCENCE MEASUREMENTS
Authors: Vierke Gerhard 
Published: January 2008

Abstract— An alternative method to that used by Mar and Roy (1974) for the determination of the kinetics of the back reaction of photosystem II from the luminescence decay curve in the presence of 3–(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU) has been suggested. The new theory relies upon two hypotheses: the well‐known recombination hypothesis of luminescence and the assumption that the luminescence yield in the seconds region is given by the variable part of the live fluorescence yield. The second hypothesis was introduced since assuming a constant luminescence yield results in kinetic data that are not consistent with measurements of the kinetics of the back reaction by the restoration of the area over the fluorescence rise curve. The dependence of the live fluorescence yield from the concentration of closed PS II traps was assumed to be represented by Delosme's expression originally derived for the rise curve of the fluorescence yield in the presence of DCMU.The theory is based on the fact that then the partial and total light sums of luminescence are simple functions of the concentration of the primary electron acceptor Q‐ of PS II. Thus, after integrating the luminescence decay curve the theory permits a convenient evaluation of the kinetics of the back reaction [Q‐](t) in terms of the partial and total light sum.This method was applied in order to determine the kinetics of the back reaction in Chlorella fusca in the presence of DCMU. It is shown that the kinetics of deactivation of the S, state can be described using the expression for the kinetics of the back reaction derived by Mar and Roy. As an alternative explanation, a biphasic first order decay of S2 is proposed.
PEROXIDASE CATALYZED GENERATION OF TRIPLET ACETONE
Authors: Bechara Etelvino J. H. , Oliveira Olga M. M. Faria , Duran Nelson , Baptista Roberto Casadei de , Cilento Giuseppe 
Published: January 2008

Abstract— Triplet acetone generated in the isobutanal/horseradish peroxidase/O, system is quenched by collisional agents of the diene type. A Stern‐Volmer analysis indicates that collision is considerably impeded, the barrier being largely entropic. Triplet‐triplet energy transfer to biacetyl is also observed. Quenching of triplet acetone by energy transfer to 9,10‐dibromoanthracene‐2‐sulfonate (DBAS) is a much faster process than energy transfer to these collisional agents, in accordance with the earlier inference that transfer to DBAS is a long‐range triplet‐singlet transfer process. The fraction of the triplet acetone which undergoes reduction to isopropanol is not interceptable by quenchers.Absorption and circular dichroism studies suggest that peroxidase shuttles between Compound II and I when generating the precursor hydroperoxide.
PHOTOBIOLOGICAL ACTIVITY IN YEAST OF DERIVATIVES OF PSORALEN SUBSTITUTED AT THE 3,4 AND/OR THE 4',5' REACTION SITE
Authors: Averbeck D. , Bisagni E. , Marquet J. P. , Vigny P. , Gaboriau F. 
Published: January 2008

Abstract— Derivatives of psoralen substituted at the position 3 and/or 5′ with various substituents (CN, CO‐R or COO‐R) have been newly synthesized. Their photobiological reactivity was determined by measuring the effects on survival and the induction of cytoplasmic ‘petite’ mutations (rho‐) in the haploid yeast Saccharomyces cereuisiae after treatment with 365‐nm irradiation in the presence of the different compounds. The effects were compared to those of known mono‐functional compounds such as angelicin, 3‐carbethoxypsoralen and 5,7‐dimethoxycoumarin and bi‐functional compounds such as psoralen and 8‐methoxypsoralen for which the photoaffinity to DNA is well known. The derivative carrying a CN group in position 3 of the psoralen molecule exhibited effects comparable to those of the bi‐functional agent 8‐methoxypsoralen. Three derivatives substituted at position 3 showed a biological activity comparable to those of the mono‐functional agent 3‐carbethoxypsoralen. Two compounds substituted at position 5′ by COOH or COOCH3‐groups were much less photobiologically active than the corresponding derivatives substituted in position 3. This suggested that the furanic site of the psoralen molecule may be photobiologically more active than the 3,4 site. Four newly synthesized angular derivatives, i.e. furo (2,3 f, g) coumarins, were found to be two to three times less active than angelicin.At the dose rate of 365‐nm irradiation used the measure of survival and rho‐ induction per viable cell allowed the classification of some of the compounds as mono‐ and some as bi‐functional agents in analogy to known mono‐ and bi‐functional compounds.
CAROTENOID TRIPLET STATE AND CHLOROPHYLL FLUORESCENCE QUENCHING IN CHLOROPLASTS AND SUBCHLOROPLAST PARTICLES
Authors: Mathis P. , Butler W. L. , Satoh K. 
Published: January 2008

Abstract— Absorption changes attributed to the triplet state of carotenoids and to primary electron donors (P‐700. P‐680): and fluorescence quenching at several wavelengths have been measured with a single apparatus. following flash excitation with a dye or a ruby laser. Spinach chloroplasts as well as subchloroplast particles enriched in Photosystem‐1 (F1), Photosystem‐2 (F1) or the light‐harvesting Chl a/h (FIII) have been examined at temperatures varying between 5 and 294 K.The triplet state of carotenoids has been identified on the basis of its difference spectrum (having a peak at 515 nm) and decay kinetics (⋍ 7 µs at low temperature; accelerated by O2 at 294 K). It is formed in all of the materials studied. The quantum yield of carotenoid triplet formation in chloroplasts increases at low temperature, but less than the fluorescence yield.In most cases the fluorescence quenching recovers approximately with the same kinetics as the decay of the carotenoid triplets. The fluorescence recovery is, however, significantly faster for chloroplasts at 730 nm. Fluorescence quenching occurs in all types of materials. The ratio of fluorescence quenching to the concentration of carotenoid triplets varies with the material, being maximum in chloroplasts and minimum in Fm particles.We conclude that the formation of the carotenoid triplet state is not limited to a few sites in the chloroplast and that a carotenoid triplet is a quencher of chlorophyll fluorescence. A detailed comparison of carotenoid triplets and fluorescence quenching gives some information concerning the organization of the pigments in the photosynthetic apparatus.
PRODUCTION OF BREAKS IN SINGLE‐ AND DOUBLE‐STRANDED FORMS OF BACTERIOPHAGE øx174 DNA BY PROFLAVINE AND LIGHT TREATMENT
Authors: Piette J. , Calberg‐Bacq C. M. , Van de Vorst A. 
Published: January 2008

Abstract— Irradiation at 440 + 360 nm and a fluence rate of 3.8 kJm‐2 min‐1, of both complexes previously formed between proflavine and either øX circular single‐stranded (ss) DNA or øX supercoiled duplex (RFI)DNA, induces single‐strand scissions in the two DNAs under consideration. Linear øXSS DNA molecules are detected by sedimentation through alkaline sucrose gradients. After treatment of the øXRFI DNA, however, the degree of degradation is the same whether it is measured under neutral or alkaline conditions, indicating that alkaline‐labile bonds are not created; moreover, double‐strand breaks can only be detected after accumulation of single‐strand breaks.In addition to the amount of proflavine bound to the DNA and the duration of irradiation, the following factors are shown to influence the nicking activity of the treatment: (1) the DNA structure (the øXRFI DNA is much more sensitive than the øXss DNA); (2) the ionic strength of the medium during irradiation (a high value of 0.5 leads to a markedly increased efficiency); (3) the addition of cysteamine (this latter compound decreases the reaction rate) and (4) the irradiation wavelength (after irradiation at 440 nm alone, the reaction occurs at a reduced rate and is sensitive to NaN3).The kinetics of the nicking reaction does not follow a single‐hit curve showing that at least one primary lesion occurs prior to strand breakage. On the other hand, strand scission cannot be detected after irradiation of the proflavine‐DNA complexes at the low fluence rate causing a decrease in the infectivity of both øXSS and øXRFI DNAs. Similarly. the sedimentation pattern of the DNA extracted from treated øx174 phages 99.9% inactivated, is identical to that of the control ss DNA, although more drastic treatments are susceptible to induce single strand breaks inside the phage head. Finally, the unknown lesion (s) that is biologically important does not prevent the treated DNAs from penetrating into the hostcells.
EVIDENCE FOR A MAGNESIUM DEPENDENT ATPase IN BOVINE ROD OUTER SEGMENT DISK MEMBRANES*†
Authors: Uhl Rainer , Borys Tom , Abrahamson Edwin W. 
Published: January 2008

Abstract—In the presence of Mg2+ and adenosine triphosphate (ATP), a rapid. light‐induced, light‐scattering transient is observed from bovine rod outer segments (ROS). This light‐scattering transient we have labelled ‘A’. Ca2+ cannot replace Mg2+. nor can guanosine triphosphate (GTP) replace ATP. ‘A’ is observed at ATP concentrations as low as a few μM.The half‐time of ‘A’, 60 ms at 20° and 20 ms at 37°, is consistent with a process possibly involved in visual transduction.‘A’ has the action spectrum of rhodopsin bleaching and its amplitude is strictly proportional to the fraction of rhodopsin bleached per flash. ‘A’ can be regenerated by 11‐cis retinal.Inhibition studics with ATP analogues, which cannot be hydrolysed and fail to evoke an ‘A’ response, reveal that an ATP hydrolysis process has to precede illumination in order for ‘A’ to occur.On the basis of the above findings. it is proposed that there is a Mg2+ dependent ATPase in ROS that allows the disk membrane to assume a new membrane state which, upon illumination, is altered. giving rise to the structural phenomenon monitored as light‐scattering transient ‘A’.
SENSITIVITY OF THE RETINA TO RADIATION DAMAGE AS A FUNCTION OF WAVELENGTH*
Authors: Ham William T. , Mueller Harold A. , Ruffolo John J. , Clarke A. M. 
Published: January 2008

Abstract—Exposure of the retina of the rhesus monkey to visible and infrared radiation from CW optical sources like the Sun, xenon lamps, etc. produces small lesions or scotomata which may be classified as thermal or photochemical, depending on the wavelength and duration of exposure. The action spectrum for the production of retinal lesions has been determined for eight monochromatic laser wavelengths extending from 1064 to 441 nm. The corneal power required to produce a lesion decreases by three orders of magnitude in going from 1064 to 441 nm. Exposure to 1064 nm radiation for 1000 s produces a typical thermal lesion at elevated retinal temperatures. whereas a 1000 s exposure to 441 nm light produces a photochemical lesion at power levels too low to raise the retinal temperature by an appreciable amount (<0.1°). The two types of lesion have entirely different characteristics as will be discussed in some detail. The photopathology of thc photochemical lesion has been studied at postexposure times ranging from 1 h to 90 days and will be demonstrated in a number of histological slides. Moreover, this photopathology correlates well with monocular visual acuity tests in the rhesus monkey as defined by the Landolt ring technique.To further elucidate the differential effects on the retina of short vs long wavelength CW radiation, we have divided a simulated solar spectrum at sea level into two spectral bands. 400–800 nm and 700–1400 nm, and determined the radiant exposures required to produce very mild lcsions on the rhesus retina for exposure times of 1, 10, 100 and 1000 s. To correlate our data with solar retinitis and eclipse blindness the image diameter or spot size on the retina was 159 μm, corresponding to the image size of the Sun on the human retina. Exposure to the 400–800 nm spectrum for durations of 10 s or greater required approximately 400 J/cm2 to produce a mild photochemical lesion. Reciprocity is maintained over the exposure range 10–1000 s. Radiant exposure to the 700–1400 nm spectrum, on the other hand, required roughly 69,100 J/cm2 for a 1000 s exposure. This was a mild thermal lesion. We were unable to produce a lesion for exposure times less than 1000 s. We interpret these data to mean that solar retinitis and eclipse blindness are primarily photochemical events produced by the short wavelength component of the solar spectrum, and that the infrared component of the solar spectrum plays only a minor role in these retinal pathologies.
PHOTOINITIATION OF SPORANGIOPHORES IN PHYCOMYCES MUTANTS DEFICIENT IN PHOTOTROPISM AND IN MUTANTS LACKING β‐CAROTENE
Authors: Galland Paul , Russo Vincenzo E. A. 
Published: January 2008

Abstract—The formation of sporangiophores from mature Phycomyces mycelium is inhibited in a closed system. Irradiation of the mycelium with blue light reverses the inhibition of spordngiophore formation. Dose response curves for this reaction are established for wild type. β‐caroteneless mutants and for mutants that are deficient in phototropism.Phototropic‐negative mutants. altered in genes madA and madB, have a raised threshold in this light reaction. whereas mutants deficient in genes madD to madG are unaffected. β‐caroteneless mutants deficient in genes carA, carB, or carR have a threshold raised by a factor of 100–2000 depending on the amount of residual synthesis of β‐carotene.