bluuebunny/crossref_metadata_2025_split huggingface dataset:
PHOTORECEPTIONS IN THE ECLOSION OF THE SILKWORM, Bombyx mort
Authors: Shimizu Isamu , Matsui Kei 
Published: January 2008

AbstractWhen silkworms, Bombyx mori, were kept in a photoperiodic regime of LD 8:16 during pupal development, the moths showed overt bimodal eclosion rhythms with one peak in the dark period, and with the other peak at light‐on. When the developing pupae were transferred from the photoperiodic cycle to continuous darkness, the eclosion of the dark period persisted with a free‐running circadian rhythm, while the eclosion corresponding to the light‐on peak was not shown. Vitamin A‐deficiency. which brought about a loss of photoreceptive function in compound eyes, significantly reduced the light‐on peak, but did not influence the timing of eclosion in the dark period. Covering compound eyes with black wax also reduced the light‐on peak. These results show that the eclosion clock of the silkworm is most likely entrained by an extraretinal photoreceptor, but the eclosion at light‐on is evoked by an exogenous light effect that is mediated via compound eyes
A NEW REUSABLE CHEMICAL ACTINOMETER FOR UV IRRADIATION IN THE 248 ‐ 334 nm RANGE
Authors: Brauer H.‐D. , Schmidt R. 
Published: January 2008

AbstractThe highly reversible thermally stable photochromic system consisting of heterocoerdianthrone‐endoperoxide (HCDPO) and its parent compounds HCD and 02 is proposed as a new reusable liquid chemical actinometer in the UV region 248 ≤λ≤ 334 nm. The foremost advantageous features of this new system are: (1) high reproducibility and accuracy, (2) high sensitivity, (3) almost wavelength independent quantum yields, (4) no loss in accuracy even after 100 repeated actinometric cycles and (5) very easy handling and straightforward calculability of the radiation quantum flux.
THE REDUCTIVE PHOTOALKYLATION OF FLAVIN BY N‐ALLYLTHIOUREA
Authors: Ott Ulrich , Traber Rainer , Hemmerich Peter , Kramer Horst E. A. 
Published: January 2008

AbstractIllumination of flavin in the presence of N‐allythiourea (ATU) inhibits catalytic turnover of flavin between its reduced and oxidized redox states by adduct formation, the adduct being no longer reoxidisable by oxygen. The first step in the mechanism of adduct formation is an electron transfer from ATU to flavin in the photoexcited triplet state. In further steps, the ATU radical cation deprotonates, electronic rearrangement occurs and radical combination with the flavosemiquinone follows, yielding a cyclic product in which ATU is added in the 4a‐ and 5‐position to the flavin chromophore.Reaction rates and yields were determined by flash photolysis and continuous illumination. A photochemical study by variation of the molecular structure of ATU was undertaken to prove the proposed mechanism and to determine the structural requirements of flavin inactivators.
ASSOCIATION OF POLAR LIPIDS TO SPINACH SUBCHLOROPLAST FRACTIONS EVOLVING OXYGEN
Authors: Farineau N. , Guillot‐Salomon T. , Tuquet C. , Farineau J. 
Published: January 2008

AbstractAn O2‐evolving photosystem II (PSII) fraction was isolated from spinach chloroplasts using Triton X‐100. The distribution of polar lipids is different from that in thylakoids: the ratio monogalactosyldiacylglycerol/digalactosyldiacylglycerol being higher and the level of sulfoquinovosyldiacylglycerol being lower in the PSII fraction. A large amount of phosphatidylglycerol containing trans‐Δ3‐hexadecenoic remains associated to the PSII fraction. A possible role for molecules of phosphatidylglycerol containing trans‐Δ3‐hexadecenoic acid in the regulation of energy transfer between the two photosystems is suggested.
THE INFLUENCE OF LIGHT ON THE NON‐DIAPAUSE RELATED ASPECTS OF DEVELOPMENT AND REPRODUCTION IN INSECTS
Authors: J. R. Philogene Bernard , McNeil Jeremy N. 
Published: January 2008

AbstractA literature review was undertaken to evaluate the effects of light on larval development and adult reproduction excluding diapause. Shortening or lengthening of larval developmental time, adult emergence, gametogenesis, fecundity and oviposition are all affected by both photoperiod and light quality.
A HIGHLY REACTIVE HETEROATOM ANALOG OF RETINAL AND ITS INTERACTION WITH BACTERIORHODOPSIN
Authors: Birnbaum Dov , Seltzer Stanley 
Published: January 2008

AbstractC18 formate ester (5) [2‐(6‐methyl‐8‐(2,6,6‐trimethyl‐1‐cyclohexen‐1‐yl)‐3E,5E,7E‐octatrienyl formate], a highly reactive analog of retinal, was synthesized and its interaction with bacterioopsin studied. The formate ester, in the absence of purple or bleached membrane, undergoes very rapid reaction (tl/2= 0.9 min) in neutral buffer but with membrane present it diffuses more rapidly into the membrane where it reacts slowly. Incorporation of 5 in the membrane results in a 38 nm (3900 cm‐1) red shift which remains after reconstitution with retinal. Similar experiments with the corresponding C18 alcohol (4) results in a red shift, but this absorption blue shifts upon reconstitution with retinal. Washing the formate ester‐treated membrane with bovine serum albumin or the corresponding lyophilized preparation with hexane, treatments that remove retinal oxime, fails to remove the UV‐visible absorption, suggesting that a covalent bond between the C18 moiety and a nucleophilic group of the protein has probably formed.
STUDIES ON HUMAN LENS: I. ORIGIN AND DEVELOPMENT OF FLUORESCENT PIGMENTS
Authors: Sen Asok C. , Ueno Norio , Chakrabarti Bireswar 
Published: January 2008

AbstractFluorescence spectra of normal mature human lenses have been measured and at least eight species with distinct emission characteristics identified. To determine the specific photochemical and photophysical processes responsible for the origin and development of these fluorophores, emission behavior of the products generated by successive irradiation of young human lenses (3–6 y old) as well as of L‐tryptophan solution have been systematically monitored. Fluorescent products that resulted from this irradiation were comparable to many of the fluorophores detected in aged lenses, indicating that light plays a major role in the development of these pigments. In addition to photogenerated species, there are other compounds in human lenses, presumably advanced glycosylated end products, with marked fluorescence properties.Several oxidation products of tryptophan including N‐formylkynurenine or its derivatives, β‐carboline or its derivatives, and anthranilic acid have been identified in the mature human lens. The development of several photoproducts also was attributed to endogenous ascorbate‐mediated Maillard reaction products, which undergo photoconversion by the visible light. Although some of these chromophores could act as photosensitaizers, the sensitizing efficiency of many are low. Conversely, the near‐UV filtering capability of these colored compounds conceivably could protect the vitreous and retina from development of any photochemical lesion.
PHTHALOCYANINE AND NAPHTHALOCYANINE PHOTOSENSITIZED OXIDATION OF 2′‐DEOXYGUANOSINE: DISTINCT TYPE I AND TYPE II PRODUCTS
Authors: Ravanat J.‐L. , Berger M. , Benard F. , Langlois R. , Ouellet R. , Lier J. E. van , Cadet J. 
Published: January 2008

AbstractThe photodynamic properties of the di‐and tetrasulfonated zinc and aluminium phthalocyanines and a tetrasulfonated aluminium napththalocyanine were studied using 2′‐deoxyguanosine as a DNA model compound. The major photooxidation products of this nucleoside were identified and classified according to their formation through a radical mechanism (type I) or a singlet oxygen mediated mechanism (type II). The major type I product was obtained and identified as 2,2‐diamino [(2‐deoxy‐β‐d‐erythropentofuranosyl)‐4‐amino]‐5(2H)‐oxazolone. Two major type II products were characterized as the 4R* and 4S* diastereomers of 9‐(2‐deoxy‐β‐d‐erythropentofuranosyl)‐7,8‐dihydro‐4‐hydroxy‐8‐oxoguanine. In addition a third product, also resulting from a type II photooxidation, was identified as 8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine. Quantification of these products provided a means to estimate the contribution of type I and type II pathways during the phthalocyanine and naphthalocyanine mediated photooxidation of 2′‐deoxyguanosine, confirming the major role of singlet oxygen in these processes.
KINETICS OF DYNAMIC HOLOGRAM RECORDING IN POLYMER FILMS WITH IMMOBILIZED BACTERIORHODOPSIN
Authors: Zaitsev S. Yu. , Kozhevnikov N. M. , Barmenkov Yu. O. , Lipovskaya M. Yu. 
Published: January 2008

AbstractPolymer films with immobilized photosensitive membrane protein, bacteriorhodopsin (BR), were prepared and investigated. A sensitive holographic interferometer with phase modulated optical beams was used for investigation of kinetics of dynamic hologram recording in BR polymer films. It was found that phase hologram formation consisted of two quasi‐exponential stages demonstrating existence of a diffusive process in obtained films. It was shown that the kinetics of a phase hologram recording by high intensity beams do not correlate with the exponential law. The applicability of BR polymer films as reversible photorefractive materials for dynamic holography and real‐time interferometry was discussed.
MONOLAYER STUDIES OF 5‐(4‐CARBOXYPHENYL)‐10,15,20‐TRITOLYL‐PORPHYRIN–I. OPTICAL STUDIES OF FILMS AT THE AIR‐WATER INTERFACE and OF FILMS TRANSFERRED ONTO SOLID SUBSTRATES†
Authors: Bardwell Jennifer , Bolton James R. 
Published: January 2008

Abstract— The title compound forms well‐behaved monomolecular films at the air‐water interface. The surface pressure‐molecular area isotherms change with the pH of the subphase in a manner which suggests that the carboxylic acid group acts as the hydrophylic portion of the molecule with a pKa of –7.3. In compressed monolayers the porphyrin ring appears to be oriented so that the plane of the ring is perpendicular to the surface.Spectroscopic studies of single monolayer films transferred to quartz slides using the Langmuir‐Blodgett technique indicate that three distinct species are present in the films, with the amount of each phase depending on the pH of the subphase. One species, present at low pH, is assigned as a monomer on the basis of its optical and fluorescence spectra and its fluorescence lifetime. At low pH this monomer species co‐exists with another non‐fluorescent aggregated species. For films formed on subphases with pH > 7.3, these two species are converted to a single, weakly fluorescent species which exhibits an unusual absorption spectrum. We postulate that this third species is a constrained aggregate but rule out the possibility of a face‐to‐face dimer on spectroscopic grounds.For films at the air‐water interface specular reflection, indicative of a smooth, highly absorbant film, is observed from monolayers of the title compound. Visual examination of this phenomenon proved to be very useful in assessing the completeness of spreading and the collapse point. Under certain conditions a distinct macroscopic structure is observed in the monolayer film. This structure is interpreted as evidence for the presence of two or more two‐dimensional crystalline phases. Support for this view comes from previous measurements of specular reflection on single crystals of tetraphenylporphyrin. There is no indication that variations in the macroscopic structure of the films have any significant effect on the microscopic properties such as the surface pressure‐area isotherms.
INDUCTION OF SEED GERMINATION IN Lactuca sativa L. BY NANOSECOND DYE LASER FLASHES*,†
Authors: Scheuerlein R. , Braslavsky S. E. 
Published: January 2008

Abstract— A 15 ns, tunable dye laser was used to induce germination of the photoblastic seeds of Lactuca sativa. One red laser flash in the range from 620 to 690 nm was sufficient to increase germination significantly above the dark level. Repeated flashes, however, were necessary to saturate the physiological response.The wavelength dependence for induction of germination differed for single and repetitive flashes. After saturating far‐red irradiation, the effect of single‐flash induction was a function primarily of the absorption spectrum of Pr. In addition, the establishment within the lifetime of a flash of a photochromic system between the red absorbing form of phytochrome (Pr) and the sum of photoreversible intermediate forms (ΣI700) contributes to this wavelength dependence at high fluence rates. This photochromic system is assumed to be shifted significantly toward Pr by wavelengths 660 nm. Similarly, a strong double‐flash effect, which is seen as an increase in effectiveness when a given total fluence is provided by two consecutive flashes rather than by one flash only, is restricted to those wavelengths that considerably shift the photochromic system Pr⇔ΣI700 toward Pr. Finally, the saturation level produced by a series of laser flashes depends, additionally, on absorption by Pfr.
PHYTOCHROME IN ETIOPLASTS IN RELATION TO CHLOROPHYLL ACCUMULATION*
Authors: Kraak H. L. , Spruit C. J. P. 
Published: January 2008

Abstract— De‐etiolation of maize seedlings reduces their sensitivity for red light potentiation of rapid chlorophyll accumulation in white light. An earlier proposal (Raven and Spruit, 1973) attributes this to migration of the far‐red absorbing form of phytochrome (Pfr) to receptors essential for chlorophyll synthesis, thereby increasing the local Pfr/total phytochrome (Ptot)ratio. We have studied etioplasts as possible loci for such P(r receptors.The level of spectrophotometric phytochrome in purified etioplasts isolated from red preirradiated maize seedlings was higher than that of dark grown plants. The difference was marginally significant, however. We argue that migration of a fraction of cytoplasmic Pfr to the etioplasts, too small to be spectrophotometically demonstrable, could still meet the requirements of the model.Dark destruction of bulk spectrophotometric Pfr following saturating red irradiation of seedlings is not paralleled by a decrease of etioplast phytochrome. the latter remaining essentially constant over long periods. On the other hand, the potentiating effect of red light in intact seedlings is still partially reversible by far red light even after 24 h of darkness when destruction of bulk Pfr is complete. Since this demonstrates persistent presence of Pfr active in potentiation, we propose that at least part of this Pfr is associated with the etioplasts.
PROBIT ANALYSIS OF LOW AND VERY‐LOW FLUENCE‐RESPONSES OF PHYTOCHROME‐CONTROLLED Kalanchoe blossfeldiana SEED GERMINATION*
Authors: De Petter E. , Van Wiemeersch L. , Rethy R. , Dedonder A. , Fredericq H. , De Greef J. , Steyaert H. , Stevens H. 
Published: January 2008

Abstract— Kalanchoë blossfeldiana seeds are light‐requiring for seed germination. On water or KNO3 solution and irradiated with several daily red (R) irradiations, the seeds show a low‐fluence (LF) response which is far‐red (FR) reversible. Incubated on gibberellic acid (GA3) the seeds show a very‐low‐fluence (VLF) response which can be saturated with red as well as with far red light. As germination is a quantal response, the sub‐optimal segments of the dose‐response curves are analysed by means of probit analysis in order to calculate the seed population parameters. There is a linear relation between the probit of the germination response and the logarithm of the fluence. Moreover, the slope for the VLF as well as for the LF response is the same. The VLF requires about 8 × 104 times less fluence than the LF. VLF saturation with FR requires about 200 times more fluence than with R.Although, GA3 and KNO3 modulate VLF and LF, respectively, there is no direct influence on the phytochrome‐phototransformations. Once Pfr is formed (in VLF or LF, or preserved in dry seeds) germination is proportional to the GAS concentration (for VLF and dark germination) or proportional to the KNO, concentration (for LF). The non‐photochemical events leading to germination seem to be triggered by a similar action mechanism for both GA, and KNO3.
EVIDENCE FOR A PTERIN‐DERIVATIVE ASSOCIATED WITH THE MOLYBDENUM COFACTOR OF Neurospora crassa NITRATE REDUCTASE*
Authors: Siefermann‐Harms Dorothea , Fritz Bernhard , Ninnemannt Helga 
Published: January 2008

Abstract— Following the method of Johnson and Rajagopalan (1982) for obtaining Form B of molybdopterin cofactors, we observed a prominent fluorescence band at480–482 nm in purified NR of Neurospora crassa mutant albino‐band after boiling the enzyme at acidic pH and readjusting the sample to alkaline pH. This fluorescence band is maximally excited at 410 nm and maximally emitting at pH 11 (“F‐480pH11”); at pH4–7 only a featureless fluorescence band of low intensity remains (“F‐480pH5”). The fluorescence ΔF‐480 = F‐480pH11 ‐ F‐480pHS is examined here. ΔF‐480 is associated specifically with NADPH‐dependent and MVH‐dependent nitrate reduction activities and with cytochrome b‐557 absorption. In a protease‐digested preparation lacking NADPH‐dependent NR activity, ΔF‐480 is associated with MVH‐dependent nitrate reduction.The ΔF‐480 signal is followed during the course of purification of NR. Its size increases with increasing purity of the enzyme. In partially purified NR preparations and especially in aqueous extracts from mycelia of N. crassa, a second, strong fluorescence signal with a pH‐dependent emission maximum at around 450 nm (maximally excited at350–370 nm) was found beside ΔF‐480. This “unspecific” signal was lost during NR purification. A procedure is developed to demonstrate AF‐480 also in presence of the unspecific (350‐370/450 nm) signal as well as flavins.We deduce that the ΔF‐480 component is part of the Mo cofactor of N. crassa NR and that the signal is caused by a pterin derivative. From calculations of total content of the AF‐480 component in mycelia it is likely that in vivo it is shared also by other enzymes.
BASF 13.338 INDUCED CHANGES IN STRUCTURE and FUNCTION OF THE PHOTOSYNTHETIC APPARATUS OF WHEAT SEEDLINGS
Authors: Mannan R. Mannar , Bose Saul 
Published: January 2008

Abstract— Growing wheat seedlings in the presence of BASF 13.338 [4‐chloro‐5‐dimethylamino‐2‐phenyl‐3(2H)pyridazinone], a PS II inhibitor of the pyridazinone group, brought about notable changes in the structure and functioning of photosynthetic apparatus.In BASF 13.338 treated plants, there was a decrease in the ratio of Chi a/Chl b, an increase in xanthophyll/carotene ratio and an increase in the content of Cyt b 559 (HP + LP). Chl/p700 ratio increased when measured with the isolated chloroplasts but not with the isolated PS I particles of the treated plants. The SDS‐PAGE pattern of chloroplast preparations showed an increase in the CPII/CP I ratio. The F685/F740 ratio in the emission spectrum of chloroplasts at ‐196°C increased. The difference absorption spectrum of chloroplasts between the control and the treated plants showed a relative increase of a chlorophyll component with a peak absorption at 676 nm and a relative decrease of a chlorophyll component with a peak absorption at 692 nm for the treated plants. The excitation spectra of these chloroplast preparations were similar. Chloroplasts from the treated plants exhibited a greater degree of grana stacking as measured by the chlorophyll content in the 10 K pellet. The rate of electron transfer through photosystem II at saturating light intensity in chloroplast thylakoids isolated from the treated plants increased (by 50%) optimally at treatment of 125 μM BASF 13.338 as compared to the control. This increase was accompanied by an increase in (a) I50 value of DCMU inhibition of photosystem II electron transfer; (b) the relative quantum yield of photosystem II electron transfer; (c) the magnitude of C550 absorbance change; and (d) the rate of carotenoid photobleaching. These observations were interpreted in terms of preferential synthesis of photosystem II in the treated plants.The rate of electron transfer through photosystems I and through the whole chain (H2O → methyl viologen) also increased, due to an additional effect of BASF 13.338, namely, an increase in the rate of electron transfer through the rate limiting step (between plastoquinol and cytochrome f). This was linked to an enhanced level of functional cytochrome f. The increase in the overall rate of electron transfer occurred in spite of a decrease in the content of photosystem I relative to photosystem II. Treatment with higher concentrations (> 125 μM) of BASF 13.338 caused a further increase in the level of cytochrome f, but the rate of electron transfer was no greater than in the control. This was due to an inhibition of electron transfer at several sites in the chain.
CIRCADIAN PHASE OF SPARROWS: CONTROL BY LIGHT AND DARK
Authors: Klein S. E. B. , Binkley Sue , Mosher Karen 
Published: January 2008

Abstract— Sparrows (Passer domesticus) are day‐active birds which exhibit circadian rhythms of perch‐hopping activity. The phases of sparrow's circadian rhythms were studied following single 4 h light pulses, single 4 h dark pulses, doublet treatments of light and dark pulses, and a 10 h light pulse.The sparrows exhibited a phase response curve to 4 h light pulses with maximum phase advances (3.8 h) at CT20 and maximum phase delays(–1.3 h) at CT16. The sparrows also displayed a phase response curve to dark pulses with maximum phase advances (2.2 h) at CT16 and maximum phase delays at CTO(–0.7 h).The remaining pulses were imposed during the subjective dark‐time. The 10 h pulse beginning 1 h after lights‐out produced a 2.2 h phase shift. The doublet of 2 h pulses that were the “skeleton” of the 10 h pulse produced a 2.5 h phase shift. The early 2 h pulse, applied by itself resulted in a ‐0.4 h delay; the late 2 h pulse applied singly produced a 3.1 h advance. When an early 3 h dark pulse was imposed together with a late light pulse, the phase was advanced 3.6 h; singly the pulses produced 1.8 h and 2.7 h advances.
THE KINETICS OF THE EARLY STAGES OF THE PHYTOCHROME PHOTOTRANSFORMATION Pr→ Pfr. A COMPARATIVE STUDY OF SMALL (60 kDalton) and NATIVE (124 kDalton) PHYTOCHROMES FROM OAT
Authors: Ruzsicska Bela P. , Braslavsky Silvia E. , Schaffner Kurt 
Published: January 2008

Abstract—A comparative study of the decay kinetics of photogenerated transients from small (60 kDalton) and native (124 kDalton) oat phytochrome in the red‐absorbing form (Pr) in phosphate buffer containing 5 mM ethylenediamine tetraacetic acid, pH 7.8, (PB) and in PB containing 20% ethylene glycol, has been carried out in the temperature range 275–298 K. The analysis confirmed that at least two primary photoproducts, intermediates Ii700s and Ii7oo are formed from Pr. The kinetic parameters, as observed in PB at 695 nm and 275 K, are similar for the I700 intermediates of both small and native phytochrome. Namely, the lifetimes are about 21 μs (component percentages 38%) for the I Ii700s and about 200 μ.s (62%) for the Ii700S‐ Arrhenius preexponential factors (A) of about 1016 and 1015 s‐1and activation energies of about 61 and 56 kJ/mol were measured for the absorbance decays of the I700S of small and native phytochrome, respectively. The kinetic data favour parallel paths for the formation of the Ii700s from Pr, and the activation parameters indicate that the primary photoreactions of the transformation from Pr to the far‐red‐absorbing form are restricted to the chromophore within the protein. Moreover, the relatively modest temperature dependence of the lifetimes of the Ii700S from small and native Pr supports the working hypothesis that the ground state reactions to the Iibl, intermediates–although somewhat influenced by the polypeptide fragment that is removed upon degradation of native to small Pr–are localized to the chromophore, as is most probably the case also for the primary photoreactions. The effect of the addition of 20% ethylene glycol on the pre‐exponential factors of the time‐dependent decay functions is discussed in similar terms of the early stages of the phototransformation.