bluuebunny/crossref_metadata_2025 huggingface dataset:
REPAIR OF UV‐IRRADIATED PLASMID DNA IN EXCISION REPAIR DEFICIENT MUTANTS OF Saccharomyces cerevisiae
Authors: Ikai Kaori , Tano Keizo , Ohnishi Takeo , Nozu Keiichi
Published: January 2008

Abstract— The repair of UV‐irradiated DNA of plasmid Yep13 was studied in the incision defective strains by measurement of cell transformation frequency. In Saccharomyces cerevisiae, radl,2,3 and 4 mutants could repair UV‐damaged plasmid DNA. In Escherichia coli, uvrA mutant was unable to repair UV‐damaged plasmid DNA; however, pretreatment of the plasmid with Micrococcus luteus endo‐nuclease increased repair. We concluded that all the mutations of yeast were probably limited only to the nuclear DNA.
INTRAMOLECULAR EXCIPLEX FORMATION IN Nα‐ACETYL‐1‐PYRENYLALANYL‐1‐METHYLTRYPTOPHAN METHYLESTER
Authors: Ruttens F. , Oedeweeck R. , Lopez‐Arbeloa F. , De Schryver F. C.
Published: January 2008

Abstract— The synthesis, absorption and emission properties of erythro (e) and threo (t) Na‐acetyl‐1‐pyrenylalanyl‐1‐methyltryptophan methylester (APTE) are reported. From the dependency of the exciplex emission maximum on the solvent polarity, the exciplex dipole moment of erythro and threo APTE were calculated. The evolution of the ratio of the quantum yield of exciplex emission and the quantum yield of emission from the locally excited state is correlated with solvent polarity and with the tendency of the solvent to interact with the peptide chain through hydrogen bonding. It is shown that solvents, inert towards the peptide function, shift the equilibrium between the two ground state conformations towards C7, in which an exciplex geometry can be reached. Hydrogen accepting solvents shift the conformational equilibrium towards C5, which cannot form an exciplex directly within the lifetime of excited pyrene.
INTERFACING FOR LASER FLASH PHOTOLYSIS EXPERIMENTS: A NEW APPROACH
Authors: Malba Vincent , Jones Guilford , Poliakoff E. D.
Published: January 2008

Abstract— A computer‐controlled nanosecond laser flash photolysis system incorporating a CAMAC interface system is described. The resulting system provides many benefits, particularly with regard to ease of operation and flexibility. The use of readily available, off‐the‐shelf components results in rapid installation, high‐level language programability, expandability, and moderate cost. Transient absorption spectra of the benzophenone triplet, ketyl radical and ketyl radical anion in aqueous acetonitrile, demonstrate the utility of the apparatus described.
EFFECTS OF IONIC STRENGTH and pH ON THE BINDING OF SANGUINARINE TO DEOXYRIBONUCLEIC ACID
Authors: Nandi R. , Chaudhuri K. , Maiti M.
Published: January 2008

Abstract— The interaction of sanguinarine with DN A has been studied in buffers of various ionic strengths and pH values where the physicochemical properties of DNA remain unchanged. Spectrophotometric analysis using absorption and fluorescence techniques indicates that the complex formed between sanguinarine and DNA is a function of ionic strength and pH. Increasing the salt concentration minimizes the importance of intercalator charge and extrapolation to 1 M [Na+] salt reveals the intercalative abilities, as reflected in binding constants, to be of the same order of magnitude as that of ethidium bromide. The fluorescence of sanguinarine bound to DNA is quenched and can be decreased by [Na +], [Mg2+] and [Ca2+] ions. The influence of pH on the fluorescence spectrum of sanguinarine with increasing concentration of DNA was studied. It is concluded that the binding of sanguinarine to DNA contains a large favourable non‐electrostatic interaction and the alkaloid binds more DNA in buffer of low ionic‐strength and acidic pH.
ALKALINE QUENCHING OF BACTERIORHODOPSIN TRYPTOPHANYL FLUORESCENCE: EVIDENCE FOR AQUEOUS ACCESSIBILITY OR A HYDROGEN‐BONDED CHAIN
Authors: Palmer Patricia L. , Sherman Warren V.
Published: January 2008

Abstract— Comparison between Trp fluorescence yields of membrane‐bound bacteriorhodopsin (BR) and retinylidene‐free bacterioopsin (BO) is consistent with a model in which all eight Trp residues are active fiuorophores in the latter, while the emission of all but two residues in the former is lost by energy transfer to retinal. The visible chromophore of BR is progressively bleached with increasing pH. Up to pH 12 this bleaching is reversed on reneutralization; but above this the change is irreversible with the appearance of a new absorption band characteristic of free retinal. Emission yields for both proteins decrease with increasingly alkaline pH in a manner typical of energy transfer to weakly‐fluorescent tyrosinate. The limiting yields, reached at a pH corresponding to that producing irreversible bleaching of the visible chromophore, agree with an integral value of one remaining active Trp fluorophore in BR and between one and two in BO and show that the bulk of Trp are within the 11 Å Förster energy‐transfer distance of Tyr accessible to OH−. Current models of the native protein structure of BR arrange the polypeptide chain primarily in a bundle of seven helical segments with axes perpendicular to the lipid bilayer plane and with buried polar residues, including Trp and Tyr, located at intrahelical surfaces. An interpretation of the observed accessibility of buried Tyr to OH− is that an aqueous region exists within the protein structure. Moreover, this putative aqueous region must be close to the retinylidene chromophore and thus may be associated with the light‐driven ion transport system. The results are also compatible with energy transfer to internal Tyr residues which are connected via a chain of phenolate hydrogen bonds to a surface Tyr.
LUCIFERASES FROM DIFFERENT SPECIES OF FIREFLIES ARE ANTIGENICALLY SIMILAR
Authors: Wienhausen G. , DeLuca M.
Published: January 2008

Abstract— Antibodies raised against luciferase purified from adult Photinus pyralis are shown to bind to luciferases from several species of the families Lampyridae and Elateridae. Based on their migration in denaturing gels, the enzymes from Pyrophorus plagiophthalamus are smaller and Photuris species larval enzyme is larger than the P. pvralis enzvme. All of the enzvmes examined are antieenicallv similar.
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.
RELATIVE IMPORTANCE OF BLUE LIGHT AND LIGHT ABSORBED BY PHYTOCHROME IN GROWTH OF MUSTARD (Sinapis alba L.) SEEDLINGS*
Authors: Drumm‐Herrel Helga , Mohr Hans
Published: January 2008

Abstract— Hypocotyl straight growth in mustard (Sinapis alba L.) responds very strongly and in precisely the same way to low fluence rate red (RL) and white light (WL). The effect of weak light can be attributed fully to light absorption by phytochrome. Only with increasing fluence rate an effect of blue light (BL) comes into play which cannot be explained by the action of phytochrome. However, this specific action of BL can be demonstrated in hypocotyl growth of mustard seedlings only up to 5 days after sowing (25°C). With older seedlings control of hypocotyl growth seems to be exerted exclusively via phytochrome. Regarding the far‐red light dependent “high irradiance reaction” (FR‐HIR) it was found that it plays a dominant role in growth of mustard only during a relatively short period. It tends to disappear in favor of a RL‐HIR between 3 and 4 days after sowing. It is concluded that the seedling exhibits a largely endogenous temporal pattern of responsiveness to light. Phototropism of the mustard seedling can be elicited by low fluence rates (< 1 mW m−2) of unilateral BL. This same light has no effect on straight growth. It is concluded that BL‐dependent phototropic growth response of a hypocotyl and the effect of BL on longitudinal growth of the hypocotyl are unrelated phenomena.
DIURNAL MODULATION OF PHOTOTROPIC RESPONSE BY TEMPERATURE AND LIGHT IN Chenopodium rubrum L. AS RELATED TO STEM EXTENSION RATE ANDARGININE DECARBOXYLASE ACTIVITY*
Authors: Schwali M. , Kropp B. , Steinmetz V. , Wagner E.
Published: January 2008

Abstract— Seedlings of Chenopodium rubrum were grown under 12: 12 h light‐dark cycles with the light period at 32.5°C and darkness at 10°C (“normal” conditions) or with light at 10°C and darkness at 32.5CC (“inverse” conditions). When grown under unilateral white light with the photo‐thermoperiodic conditions described above, inverse seedlings did not show phototropic curvature while normal seedlings did. Regardless of temperature regime used, plants irradiated with unilateral blue light (456 nm) at 10°C failed to curve on subsequent incubation at 32.5°C. If the phototropic stimulus was given at 32.5°C followed again by 32.5°C in darkness, phototropic curvature was observed. The results with monochromatic blue light thus explain the lack of phototropic response of “inverse” seedlings with the unilateral light period given at 10°C. “Inverse “seedlings showed a sharp rhythm in their capacity to respond to phototropic stimulation at 32.5°C. The greatest capacity to respond came when the stem extension rate was actually zero. The differential growth accompanying phototropic curvature thus seems to be different from the growth responsible for uniform stem elongation. The curvature may result from differential turgor changes as in the case of sun tracking of leaves. “Inverse seedlings” showed clear signs of stress and displayed a rhythm in arginine decarboxylase, an enzyme thought to be stress‐related, with maxima during the low temperature light periods. It is concluded that the phototropic perception transduction chain is modified by the inverse conditions somewhere before the final growth‐turgor steps, since they exhibit geotropic sensitivity.
THE BLUE LIGHT RESPONSE OF STOMATA: PULSE KINETICS AND SOME MECHANISTIC IMPLICATIONS*
Authors: Zeiger Eduardo , Iino Moritoshi , Ogawa Teruo
Published: January 2008

Abstract— Intact leaves of Commelina communis irradiated with high fluence rates of red light, showed discrete increases in stomatal conductance in response to pulses (1‐100 s) of blue light (250 μmol m−2 s−1). Red light pulses were ineffective, indicating that the conductance increases were not mediated by photosynthesis and that they constitute a specific stomatal response to blue light. The response peaked 15 min after the pulse and was completed within50–60 min. Conductance increases were proportional to pulse duration up to about 30 s and saturated at longer exposures. The relationship between stomatal responses and pulse duration approximately fitted an exponential function, with a t 9s. Pulse responses at two different fluences indicated that reciprocity held. Responses to two consecutive pulses varied with time between pulses. A saturating pulse applied immediately after a preceding one induced no additional response; two saturating pulses 50 min apart caused two identical, consecutive responses. Total increases in conductance induced by two pulses separated by intermediate time intervals increased with time between pulses with a = 9 min. These results point to a blue light‐dependent photoconversion of a molecular form, with the activity of the photoconversion product decaying in a thermal reaction. Under continuous blue light, prevailing fluence rates and rates of the light and thermal reactions are postulated to determine steady‐state activities of the photoconversion product and proportional increases in conductance levels. These findings have implications for the environmental and metabolic roles of the stomatal response to blue light.
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.
PHOTOTROPISM AND AXIS EXTENSION IN LIGHT‐GROWN MUSTARD (Sinapis alba L.) SEEDLINGS‡
Authors: Rich T. C. G. , Whitelam G. C. , Smith H.
Published: January 2008

Abstract— The relationship between phototropism and axis extension was examined in light‐grown mustard (Sinapis alba L.) seedlings using the low pressure sodium lamp (SOX)† technique to eliminate growth responses due to phytochrome. Addition of blue light caused no net inhibition of hypocotyl elongation, but plants showed a phototropic response. Curvature was caused by a simultaneous inhibition of growth on the illuminated side of the hypocotyl and an acceleration on the shaded side. Phototropism thus occurs independently of axis elongation and suggests that they are two separate processes. The results are inconsistent with the Blaauw theory of phototropism.
THE TRIPLET STATE OFPYRIDOXAL–5′‐PHOSPHATE IN LASER FLASH PHOTOLYSIS
Authors: Cornish T. J. , Ledbetter J. W.
Published: January 2008

Abstract— Sensitization and quenching experiments demonstrate that laser flash photolysis ofpyridoxal–5′‐phosphate populates a triplet state about 244 kJ/mol. Excitation by the 337.1‐nm photons from a nitrogen laser generated transient absorption in the 400‐nm region which decayed with a fast first order component on a much slower one. Xanthone photosensitized the same absorption; oxygen, nitric oxide, biacetyl, and 1,3‐cyclo‐hexadiene quenched it. Spectra and lifetimes suggest that the triplet state leads to radical formation.
THE MOLECULAR WEIGHT OF HAEMATOPORPHYRIN DERIVATIVE, ITS GEL COLUMN FRACTIONS and SOME OF ITS COMPONENTS IN AQUEOUS SOLUTION
Authors: Swincer A. Geoffrey , Ward A. David , Howlett Geoffrey J.
Published: January 2008

Abstract— The average molecular weights of haematoporphyrin derivative (HPD), the fractions of HPD that can he obtained by gel chromatography and of purified haematoporphyrin and protoporphyrin in aqueous solution have been determined by ultracentrifugation. The results show that HPD contains polymeric material with the excluded fraction from the gel column (HPD aggregate) having an average molecular weight of greater than 20000. The two remaining gel column fractions of HPD have lower molecular weights and their similarity indicates that these fractions do not separate because of molecular weight differences. Purified haematoporphyrin has a comparatively low molecular weight in aqueous solution but the data is not capable of discriminating between monomer, dimer or slightly higher oligomer. In contrast, protoporphyrin sediments to the bottom of the centrifuge tube under the conditions of sedimentation equilibrium indicating that it has an average molecular weight considerably greater than that of HPD aggregate.
INDUCTION OF CHROMOSOME ABERRATIONS IN ICR 2A FROG CELLS EXPOSED TO265–313 nm MONOCHROMATIC ULTRAVIOLET WAVELENGTHS and PHOTOREACTIVATING LIGHT
Authors: Rosenstein Barry S. , Rosenstein Rebecca B.
Published: January 2008

Abstract— Exposure of ICR 2A cells to either 265, 289, 302 or 313 nm monochromatic UV wavelengths caused the induction of chromosome aberrations with chromatid gaps and breaks being the most common type of aberration detected. Treatment of U V‐irradiated cells with photoreactivating light (PRL) resulted in a lower yield of aberrations demonstrating that pyrimidine dimers are involved in the formation of chromosome aberrations induced by the UV wavelengths tested. However, the decrease in the level of aberrations resulting from PRL treatment of 313 nm‐irradiated cells was significantly less than for the other wavelengths indicating that non‐dimer photoproducts may have played an important additional role in the induction of chromosome aberrations by this UV wavelength.
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.
WAVELENGTH EFFECTS ON THE PHOTOCYCLOREVERSION QUANTUM YIELD OF SOME PHOTOCHROMIC ENDOPEROXIDES
Authors: Brauer H.‐D. , Schmidt R.
Published: January 2008

Abstract— The photocycloreversion quantum yields Q of the endoperoxides of anthradichromene, benzodixanthene and dimethylhomoocoerdianthrone have been investigated in the 248 ≤γ≤ 405 nm wavelength range. Two types of wavelength dependencies can be distinguished phenomenologically. For the excitation of the Sn(n≥ 3) states of dimethylhomöocoerdianthrone endoperoxide γ‐independent Q‐values have been observed throughout 365 ≥γ≥ 265 nm. The endoperoxides of anthradichromene and benzodixanthene in contrast exhibit a quite different and unusual dependence of Q on γ. For both compounds Q first increases with photon energy until a fairly sharp maximum in Q is reached at 302 nm. With further increasing energy Q falls off and approaches a wavelength independent plateau between 280 and 248 nm. The S1‐states of the endoperoxides investigated are inactive for photocycloreversion, which is generally found in endoperoxide photochemistry. The wavelength dependencies observed reveal that the photocycloreversion of endoperoxides deviates remarkably from the commonly accepted generalization that photochemical reactions in solution phase should only occur from the lowest excited singlet or triplet states.
PHOTOINACTIVATION OF A Chlamydomonas MUTANT(NL–11) IN THE PRESENCE OF METHIONINE: ROLES OF H2O2 and O‐2
Authors: Takahama Umeo , Egashira Takeshi , Nakamura Kazuo
Published: January 2008

Abstract— A mutant of Chlamydomonas reinhardtii(NL–11) isolated from a wild type (137c+) was inactivated in the light in the presence of methionine at concentrations where the wild type was not inactivated. The inactivation was suppressed by either catalase or superoxide dismutase (SOD). Light‐induced H2O2 formation and nitroblue tetrazolium (NBT) reduction inNL–11 were greater than those in the wild type. Methionine stimulated both the H2O2 formation and the NBT reduction inNL–11 as well as the wild type. The light‐induced NBT reduction inNL–11 in the presence of methionine was partially suppressed by externally added SOD suggesting the participation of O‐2. These results suggest that the hypersensitivity ofNL–11 to methionine in the light is due to stimulated formation of H2O2 and O‐2.
RESONANCE RAMAN and ABSORPTION SPECTRA OF ISOMERIC RETINALS IN THEIR LOWEST EXCITED TRIPLET STATES
Authors: Wilbrandt R. , Jensen N.‐H. , Houée‐Levin C.
Published: January 2008

Abstract— The triplet‐triplet absorption spectra of 9‐cis‐, 13‐cis‐ and all‐fraw‐retinal as well as the time‐resolved resonance Raman spectra of the lowest electronically excited triplet states of 9‐cis‐, 11‐cis, 13‐ciy and all‐trans‐retinal in aromatic solvents at room temperature have been obtained under conditions ensuring the isomeric purity of the starting materials. The triplet states were produced by triplet energy transfer from a sensitizer in pulse‐radiolysis experiments. The overall results suggest that the isomeric retinals form either different relaxed triplet species or different mixtures of relaxed triplet species. The possible implications about the size of the energy barriers separating the various triplet species are discussed. The resonance Raman spectra obtained by using either anthracene (ET= 177.7 kJ mol‐1) or naphthalene (ET= 254.8 kJ mol‐1) as sensitizers were virtually identical for the corresponding triplet states from each of the isomers 11‐cis‐, 13‐a's‐ and all‐tams‐retinal, suggesting that the relaxed triplet species or the mixture of relaxed triplet species formed from each isomer is independent of the energy of the sensitizer.
PICOSECOND FLUORESCENCE DECAY TIME MEASUREMENTS OF NUCLEIC ACIDS AT ROOM TEMPERATURE IN AQUEOUS SOLUTION
Authors: Georghiou S. , Nordlund Thomas M. , Saim A. M.
Published: January 2008

Abstract— We report the room‐temperature fluorescence decay times of calf thymus DNA when native and when 16% of its guanine residues are methylated at theN–7 position. The samples were excited with single, 25 ps, 266 nm laser pulses from a frequency‐quadrupled Nd: YAG laser. Fluorescence was detected with a streak camera‐optical multichannel analyzer system that has a time jitter of about 2 ps. For DNA and methylated DNA we detected a major component that has a decay time of about 10 and 20 ps, respectively. A second component has a corresponding decay time of about 65 and 80 ps and makes a contribution of0–10% and20–40% depending on the transmission characteristics of the emission filter employed. In contrast, the decay time of 7‐methyl GMP, which contains the same fluorophore as methylated DNA, is approximately single exponential and has a decay time of180–210 ps depending on the emission filter. The absence of a pronounced time delay between the fluorescence decay profiles of the nucleic acids and the exciting light pulse points against the formation of excited‐state complexes (excimers).
PROTEIN GLOBULE SPEEDS UP THE HEME PHOTOREDUCTION
Authors: Marinov Beniamin S. , Gerasimenko Vladimir V.
Published: January 2008

Abstract— To answer the question whether the external electron can be transferred through the protein globule, the rate of photoreduction of the free heme with dye radicals was compared with that of the heme in various protein environments, in cytochrome c, myoglobin and in heme‐HSA complex. In all cases the globular part of proteins did not prevent the photoreduction of the heme; in fact, it speeded up the process. As determined by flash‐photolysis, the rate constants(1–5) x 108 M‐1 s‐1 are close to that of the diffusion controlled reactions between molecules of similar size. The experimental data confirm the hypothesis that the native protein globule can transfer external unpaired electrons rather effectively. We make the supposition that this ability is a general feature of proteins but not a function related to electron carriers only.
CAROTENE and CYTOCHROME C DEPENDENT SURVIVAL KINETICS IN RESPONSE TO HIGH INTENSITY VISIBLE LIGHT IN THE SMUT FUNGUS Ustilago violacea
Authors: III Oscar H. Will , Newland Natalie A. , Blelville Kaylan L.
Published: January 2008

Abstract— Exposure of variously pigmented strains of Ustilago violacea to high intensity incandescent radiation resulted in the generation of three types of survival curves. High carotene, low cytochrome c containing strains of U. violacea were generally characterized by linear type I survival curves with slopes approximately equal to zero. Strains which lacked carotenes were characterized by exponential decay type II survival curves. A third survival curve, type III was observed with carotene accumulating strains which also contained large amounts of cytochrome c. The type III curves are characterized by an initial loss of viability, similar to the type II curves, followed by a recovery period, with eventual stability in survival. The survival curve type appears to be dependent on the relative mg quantities of cytochrome c and carotenes in the cells. Strains with carotene/cytochromec ratios of0–1 × 10‐1,3–15× 10‐1 and l6 × 10‐1 and above had type II, type III and type I survival curves, respectively.
[MESITYL]BACTERIORHODOPSIN. THE PROPERTIES OF AN ANALOGUE OF THE PURPLE MEMBRANE CONTAINING [MESITYL] RETINAL AS THE CHROMOPHORE
Authors: Sonnewald Ursula , Seltzer Stanley , Robinson A. Edward , Packer Lester
Published: January 2008

Abstract— A new synthesis of all‐trans‐[mesityl]retinal, II, (all‐trans‐3,7‐dimethyl‐9‐(2′,4′,6′‐trimethylphenyl)‐2,4,6,8,‐nonatetraenal) and 13‐cis‐[mesityl]retinal, VI, (3,7‐dimethyl‐9‐(2′4′6′‐trimethylphenyl)‐2Z,4E,6E,8E‐nonatetraenal) is reported. Combination of all‐trans‐[mesityl]retinal with bacterioopsin results in the formation of a synthetic membrane (Λmax 460) which has photocycling properties similar to the purple membrane although its cycling rate is very much slower. An M‐type intermediate can be trapped at ‐60°C. Photoreversal of the M‐intermediate to the wavelength of initial absorption is observed. Phototransformation of the initial [mesityl]bacteriorhodopsin is accompanied by conversion of the all‐frans to the 13‐cis‐isomer.
AN IN VITRO TEST FOR PHOTOINDUCED TOXICITY OF BENZOTHIADIAZINE DIURETICS USING BACTERIOPHAGE LAMBDA
Authors: Fujita Hitoshi , Matsuo Itsuro
Published: January 2008

Abstract— The relative photoinduced toxicity of five benzothiadiazine diuretics was assessed with respect to their potentiality to inactivate bacteriophage lambda by exposure to near‐UV light in a semi‐aqueous solution of 40% N,N‐dimethylformamide. The results showed the following order for the toxicity on a quantum yield basis: penflutizide > trichlormethiazide > methichlothiazide > benzylhydrochlorothiazide > hydrochlorothiazide. Since the bacteriophage was inactivated even when mixed with preirradiated solutions of the diuretics, some photoproducts are responsible for the photoinduced toxicity of the diuretics. Although a lowered pH affected the infectivity, it was a minor factor.
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.
ON THE MECHANISM OF WAVELENGTH REGULATION IN VISUAL PIGMENTS
Authors: Kakitani Hiroko , Kakitani Toshiaki , Rodman Hillary , Honig Barry
Published: January 2008

Abstract— The contributions of different factors that might be responsible for the 500 nm absorption maximum of bovine rhodopsin are evaluated in detail. These include: (1) electrostatic interactions between the chromophore and a charged amino acid on the apoprotein; (2) exciton interactions with aromatic amino acids; (3) twisting about single bonds which have considerable double bond character; (4) weak interactions between the Schiff base and a putative counter‐ion. Analysis of these mechanisms in terms of theoretical and experimental results suggests that(2–4) are all capable of contributing to the protein induced spectral shifts. However, the “external point charge” model proposed previously, i.e. mechanism (1), appears to provide the crucial interaction. In this paper, the theoretical basis for this model is discussed in detail. The model is briefly evaluated in light of the amino‐acid sequence of bovine rhodopsin and possible implications for other visual pigments are considered.
EXCIMER FORMATION OF N‐(I‐PYRENESULFONYL)‐DIPALMITOYL‐L‐α‐ PHOSPHATIDYLETHANOLAMINE AT THE LIPID‐WATER INTERFACE OF FAT CELL PLASMA MEMBRANES
Authors: Kaneda Norio , Tanaka Fumio , Kido Nobuo , Yagi Kunio
Published: January 2008

Abstract— The mechanism of excimer formation of N‐(l‐pyrenesulfonyl)‐dipalmitoyl‐L‐α‐phosphatidylethanolamine incorporated into fat cell plasma membranes was studied by means of steady‐state and pulse fluorometry. It was found that the pyrenesulfonyl group at the lipid‐water interface of the membrane formed an appreciable amount of ground‐state dimers and that the excimer of the pyrenesulfonyl group was formed through two different processes: (i) the collisional interaction of an excited monomer with a ground‐state monomer, and (ii) the direct excitation of a ground‐state dimer (approximate ratio of the two processes, 1:1). Analysis of fluorescence decay curves revealed that the detailed mechanism of excimer formation by process (i) is essentially similar to the mechanism established for the reaction in organic solvents but not to that in a highly viscous medium such as the hydrocarbon core of the membrane.
4‐THIOURIDINE AS A PHOTODYNAMIC AGENT
Authors: Salet C. , Bazin M. , Moreno G. , Favre A.
Published: January 2008

Abstract— The 4‐thiouridine photosensitized oxidation of tryptophan and histidine has been followed by measuring the oxygen consumption. The yield of photooxidation has been compared using 4‐thiouridine and hematoporphyrin as photosensitizers.
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.
TIN‐PROTOPORPHYRIN: A POTENT PHOTOSENSITIZER OF BILIRUBIN DESTRUCTION
Authors: McDonagh Antony F. , Palma Lucita A.
Published: January 2008

Abstract— Tin(IV)‐protoporphyrin chloride, a proposed chemotherapeutic agent for prevention of neonatal hyperbilirubinemia, is a potent photosensitizer of bilirubin destruction in vitro at visible wavelengths (410, 540, 580 nm). We speculate that the drug may have phototoxic effects in vivo if it accumulates in light‐accessible tissues.
DYES AND DYE MIXTURES USEFUL FOR GENERATION OF UV IN A FLASHLAMP DRIVEN TUNABLE DYE LASER
Authors: Wheeler John , Calkins John
Published: January 2008

Abstract— We have used a flashlamp driven tunable dye laser combined with angle tuned frequency doubling crystals for producing UV‐B radiation for action spectra studies of various organisms. Optimum UV‐B power generation is needed to provide biologically effective doses at wavelengths greater than 300 nm. Optimizing power will also serve to lengthen the lifetime of dyes and other laser components at shorter wavelengths where UV‐B output is more than adequate. While much information is available on dyes and dye performance from manufacturers, little information is available on the use of dyes and dye mixtures for providing the continuous high power spectrum of wavelengths necessary for biological UV action spectroscopy. We have examined a number of dyes and dye mixtures for optimal laser performance at wavelengths from 260 to 330 nm. The dyes and dye mixtures discussed here provide adequate power output in the UV‐B wavelength range and have allowed us to perform numerous UV‐B action spectra studies using the tunable dye laser.
MEASUREMENT OF CELL LYSIS BY LIGHT SCATTERING
Authors: Valenzeno Dennis Paul , Trank John W.
Published: January 2008

Abstract— A method is presented which is capable of continuously monitoring the degree of hemolysis in erythrocyte suspensions too dilute to be monitored by conventional light transmission techniques. Scattered light is used to non‐destructively assess hemolysis in sparse monolayers which are particularly well suited to many photohemolytic studies. The small angle scattering (<10°), measured here, shows a transient decline as cells settle in a culture dish and then is constant if no lysis occurs. Lysis is indicated by a decrease in scattered light to < 20% of initial intensity when lysis is complete. The light used to monitor lysis is restricted to wavelengths longer than 700 nm which is outside the absorption band of many. photosensitizers of current interest, and is a wavelength range at which light scattering is relatively independent of changes in cell volume. In photohemolytic studies with phloxine B lysis values from light scattering are shown to correlate well with lysis values from hemoglobin release. An apparatus is described which is capable of periodically measuring lysis in eight suspensions without intervention by the experimenter.
PORPHYRIN PHOTOSENSITIZATION OF PROTEINS IN CELL MEMBRANES AS STUDIED BY SPIN‐LABELLING AND BY QUANTIFICATION OF DTNB‐REACTIVE SH‐GROUPS
Authors: Moan Johan , Vistnes Arnt I.
Published: January 2008

Abstract— Human cells of the line NHIK 3025 were exposed to hematoporphyrin derivative (Hpd) and light and analysed with respect to; (i) the mobility of membrane proteins as determined by electron spin resonance measurements of a protein‐bound spin label, (ii) fluorescence excitation spectra, (iii) relative number of DTNB‐reactive SH‐groups on their surface and in sonicated cell homogenates, (iv) survival, and (v) morphologic appearance as seen by ordinary phase contrast microscopy. A significant fraction of the porphyrins bound to the outer cell membrane was in close contact with proteins. 5,5′‐Dithiobis‐2‐nitrobenzoic acid reactive SH‐groups on the outer cell membrane were very sensitive to the treatment with Hpd + light and were degraded according to non‐exponential kinetics. When the cells were irradiated after spin labelling, the labelled proteins became less mobile during the irradiation, indicating protein cross linking. Irradiation before spinlabelling resulted in a selective degradation of low‐mobility proteins.
HOECHST 33258 DYE GENERATES DNA‐PROTEIN CROSS‐LINKS DURING ULTRAVIOLET LIGHT‐INDUCED PHOTOLYSIS OF BROMODEOXYURIDINE IN REPLICATED AND REPAIRED DNA
Authors: Xi‐Cang Guo , Morgan William F. , Cleaver James E.
Published: January 2008

Abstract— Substitution of bromodeoxyuridine for thymidine in the DNA of mammalian cells sensitizes them to a range of wavelengths of ultraviolet light. Cells are also sensitized to photochemical reactions involving dyes such as Hoechst 33258, which is used to produce differential staining of chromatids according to their bromodeoxyuridine content. Irradiation with 313 nm light of human and hamster cells containing bromodeoxyuridine in their DNA produced single‐strand breaks, detectable by alkaline elution, but no DNA‐protein cross‐links. Irradiation with 360 nm light in the presence of Hoechst 33258 produced extensive DNA‐protein cross‐linkage as well as single‐strand breaks. These cross‐links were observed in DNA containing bromodeoxyuridine incorporated by either semiconservative or repair replication, and may provide a method for identification of proteins in close proximity to replication forks or repair sites. When the protein was removed with proteinase K, bromodeoxyuridine in repair patches after irradiation by doses of ultraviolet (254 nm) light as low as 0.26 J/m2 could readily be detected. Hoechst 33258‐mediated photolysis, therefore, provides a sensitive new technique for measuring repair replication after ultraviolet light irradiation.
EXCITED STATE pKa BEHAVIOUR OF DAPI. A RATIONALIZATION OF THE FLUORESCENCE ENHANCEMENT OF DAPI IN DAPI‐NUCLEIC ACID COMPLEXES*
Authors: Szabo A. G. , Krajcarski D. T. , Cavatorta P. , Masotti L. , Barcellona M. L.
Published: January 2008

Abstract— The steady state and time resolved fluorescence of the drug and chromosomal staining agent, 4′,6‐diamidino‐2‐phenylindole dihydrochloride, DAPI, was examined under different solvent conditions. In solutions between pH 3 and pH 9 the fluorescence spectral maximum of DAPI was found at 460 nm. The fluorescence decayed with double exponential kinetics, with decay times of 2.86 and 0.144 ns, at all wavelengths below 550 nm. At 550 nm single exponential decay kinetics with a lifetime of 0.153 ns was observed. The fluorescence spectrum could be resolved into two components, the 2.86 ns component having a spectral maximum near 450 nm and the 0.144 ns component having a spectral maximum near 490 nm. The results are rationalized in terms of there being two different configurations of DAPI, one of which undergoes a rapid protonation of the indole ring by proton transfer from the 6‐amidinium group in the excited singlet state. The 0.144 ns component is assigned as the fluorescence from the excited state of the protonated indole ring. The results provide an explanation of the fluorescence enhancement in DAPI‐nucleic acid complexes.
VUV/SOFT‐X‐RAY SPECTROSCOPIC FACILITIES AT THE SYNCHROTRON RADIATION LABORATORIES IN JAPAN
Authors: Namioka Takeshi
Published: January 2008

The present status is described of the vacuum ultraviolet/soft‐X‐ray spectroscopic facilities at the synchrotron radiation laboratories in Japan. An overview is presented of the spectroscopic instruments available and under development at the SOR‐RING at the Institute for Solid State Physics, University of Tokyo, the Photon Factory‐ring at the National Laboratory for High Energy Physics, the UVSOR at the Institute for Molecular Science, and the TERAS at the Electrotcchnical Laboratory. Emphasis is placed upon the unique features of the instruments developed in Japan.
VUV ABSORPTION AND ITS RELATION TO THE EFFECTS OF IONIZING CORPUSCULAR RADIATION*
Authors: Inokuti Mitio
Published: January 2008

Elements of the physics of photoabsorption as well as of energy transfer from fast charged particles are discussed. Among the key notions there are oscillator‐strength spectra, quantum yields, and action spectra. Throughout the discussion, emphasis is put on the important role of soft X‐rays and VUV light as obtained from a synchrotron radiation source in the understanding of actions of ionizing radiations in general.
EFFECTS OF UV, SUNLIGHT AND X‐RAY RADIATION ON QUIESCENT HUMAN CELLS IN CULTURE
Authors: Kantor G. J.
Published: January 2008

Nondividing human diploid fibroblasts (HDF) in culture have been used to study the effect on cell lethality of ultraviolet light, natural sunlight and X‐rays. A lethal effect is defined as cellular degeneration, loss from the culture and inability to exclude vital strains. Far‐and mid‐UV have a readily observable lethal effect (cell loss), with DNA and DNA damage as the critical target and critical damage respectively. In part, natural sunlight kills cells by a similar mechanism but has an additional lethal effect at longer exposure times. This additional effect is expressed by the retention of the dead cells in culture, in contrast to the UV‐induced promotion of cell degeneration and loss. Relatively large doses of X‐rays that destroy proliferative capacity, have no detectable lethal effect on the maintenance of nondividing cells. The biological response of nondividing HDF to radiations from different parts of the electromagnetic spectrum is dissimilar.
PHOTOCHEMICAL BEHAVIOR AND EMISSION CHARACTERISTICS OF 9‐VINYLANTHRACENE
Authors: Ebeid E. M. , El‐Gamal M. A. , Morsi S. E.
Published: January 2008

9‐Vinylanthracene (9‐VA) is an efficient fluorescer of fluorescence quantum yield = 0.91 0.03 in methanol (ex= 365 nm). This is consistent with its low photochemical quantum yields c (cx= 365 nm) of 0.005 in the absence of azobisisobutyronitrile (AIBN) radical initiator and c= 0.02 in the presence of 10‐2M dm‐3 AIBN. 9‐Vinylanthracene was shown to behave as a 9‐substituted anthracene undergoing photodimerization rather than the typical vinyl aryl monomer photopolymerization. The photodimer formation is supported by spectroscopic techniques. 9‐Vinylanthracene undergoes efficient fluorescence quenching in the presence of AIBN. Stern‐Volmer plots indicate a collisional mechanism. 9‐Vinylanthracene crystals as well as polycrystalline films give excimeric emission (max= 510 nm, cx= 380 nm) which is considerably red shifted (ca. 100 nm) compared with molecular emission.