bluuebunny/crossref_metadata_2025 huggingface dataset:
FORMATION OF AGGREGATES OF TRYPTIC FRAGMENTS DERIVED FROM THE CARBOXYL‐ TERMINAL HALF OF PEA PHYTOCHROME and LOCALIZATION OF THE SITE OF CONTACT BETWEEN THE FRAGMENTS BY AMINO‐TERMINAL AMINO ACID SEQUENCE ANALYSIS*
Authors: Yamamoto Kotaro T. , Tokutomi Satoru
Published: January 2008

Abstract—

Limited trypsinization of large pea (Pisum sativum cv. Alaska) phytochrome and subsequent size‐exclusion chromatography (SEC) in 0.1 M Na phosphate, pH 7.8, yielded a high‐molecular‐mass aggregate of tryptic fragments of phytochrome. Further SEC in 0.1 M Tris‐HCl, pH 7.5, plus various concentrations of NaSCN, indicated that the tryptic‐fragment complex contained an aggregate of 7 fragments of molecular mass from 38 to 55 kDa. The amino‐terminal sequence of each fragment was determined from the samples electroblotted from sodium dodecylsulfate polyacrylamide gels onto polyvinylidene difluoride membranes, in order to localize the various fragments on the phytochrome polypeptide chain. All of the 7 fragments in the aggregate were found to be derived from the carboxyl‐terminal half of phytochrome. A portion of the polypeptide chain (from Ala‐752 to Arg‐1000) common to all the tryptic fragments has been assigned as the site(s) of contact of the fragments. The tryptic‐fragment complex, as well as large phytochrome itself, has been shown by SEC to dissociate to monomers in 2 M NaSCN. The result indicates that the main force involved in maintaining the complex and in contacts between monomers of phytochrome is non‐ionic in nature. Relationship between the contact site(s) of the tryptic‐fragment complex and large phytochrome monomer is discussed.
DUAL EFFECTS OF TRYPTOPHAN IN THE HORSERADISH PEROXIDASE SYSTEM THAT GENERATES TRIPLET ACETONE
Authors: Silva Eduardo , Cilento Giuseppe
Published: January 2008

Abstract—

When tryptophan is added to the horseradish peroxidase/hydrogen peroxide system, it markedly increases the rate of ‘spontaneous’ conversion of peroxidase‐compound II to the native form without undergoing any alteration by spectral criteria. The D‐isomer is more efficient than the L‐isomer. The latter binds to the enzyme compound II, although at a site not very favourable for reduction. The accelerating effect of tryptophan is also seen when isobutyraldehyde or its enol added to the system, is converted into triplet acetone. Again the D‐isomer is more efficient than the L‐isomer. The D‐isomer is also more efficient in quenching the acetone phosphorescence. These results indicate that, at least in the case of L‐tryptophan where complexation with compound II occurs, the interaction of tryptophan with triplet acetone bound to the enzyme takes place in a ternary complex.
PHOTOSENSITIZATION OF ANTICANCER AGENTS‐8. ONE‐ELECTRON REDUCTION OF MITOXANTRONE: AN EPR AND SPECTROPHOTOMETRIC STUDY
Authors: Reszka Krzysztof , Lown J. William
Published: January 2008

Abstract—

An efficient method of one‐electron reduction of the anticancer agent mitoxantrone is described. The method depends on illumination of a suitable photosensitizer absorbing blue light [acriflavine, anthrapyrazole, or Ru(bpy)+] in the presence of the drug and an electron donor, such as NAD(P)H, in deaerated solutions. An EPR spectrum, assigned to a semiquinone of mitoxantrone, is generated under these conditions and identified by spectral simulation. Decay of this species, attributed to a radical‐radical reaction, gives a second order rate constant of 1.7 102M‐1s‐1 in organic media [dimethylsulfoxide (DMSO)/pH 8 buffer, 1:1 vol/vol] but is more rapid (˜104 M‐1 s‐1) in aqueous media under comparable conditions. The considerably decreased lifetime of the mitoxantrone radical at pH 5 is attributed to an additional electron transfer, promoted by protonation of the radical, and/or to an accelerated recombination of neutral radicals, leading to an EPR‐silent species. Parallel spectrophotometric studies on the generation of the mitoxantrone reduced species by photosensitized reduction are described. The method offers convenient access to a key radical species involved in the metabolism and possible mode of action of this clinical anticancer agent.
PHOTODYNAMIC INACTIVATION OF RUBELLA VIRUS ENHANCES RECOMBINATION WITH A LATENT VIRUS OF A BABY HAMSTER KIDNEY CELL LINE BHK21*
Authors: Yamamoto Nobuto , Urade Masahiro
Published: January 2008

Abstract—

Rubella virus is very sensitive to photodynamic action. When tested with 1.2 times10‐5M toluidine blue and 8 W fluorescent lamp at a fluence of 11 W/m2, inactivation kinetics showed a linear single hit curve with a k value of 1.48 min‐1. Photodynamic inactivation of rubella virus greatly enhanced recombination with a latent virus (R‐virus) of baby hamster kidney BHK21 cells. In contrast, no hybrids were detected in lysates of the cells infected with either UV‐treated or untreated rubella virus. Therefore, hybrid viruses were readily detected only in lysates of BHK21 cells infected with photodynamically treated rubella virus. Photodynamic damage of rubella virus genomes generated a new hybrid type (hybrid type 3) in addition to a previously described type 2 hybrid (formerly designated as HPV‐RV variant). Although both of these hybrid types carry the CF antigens of rubella virus, plaque forming ability of type 3 hybrid is neutralized neither by anti‐rubella serum nor by anti‐latent virus serum while type 2 hybrid is neutralized by anti‐latent virus serum.
DO YEARS OR QUANTA AGE THE RETINA?
Authors: Weale R. A.
Published: January 2008

Abstract—

The progressive loss of visual faculties with advancing age is attributed, sometimes, mainly to allegedly inevitable optical deterioration, such as clouding of the media, or again to neurosenescence, as typefied by cell‐death. The relevant factors are assessed, and it is not thought likely that changes in normal ocular optics account for changes in contrast sensitivity and visual acuity with age. The role of senescent changes in the retina is analysed. The progressive temporal and spatial patterns of the accumulation of lipofuscin in the retinal pigment epithelium (RPE) and the putative control of its concentration by the crystalline lens are examined following an earlier suggestion that lenticular UVA transmissivity may control the rate of UVA entry into the eye and so perhaps the amount of lipofuscin formed in the RPE. It is suggested that morphological changes attributed to senescence may partly be due to cumulative effects of irradiation.
INHIBITION OF TRANSIENT GENE EXPRESSION IN CHINESE, HAMSTER OVARY CELLS BY TRIPLET‐SENSITIZED UV‐B IRRADIATION OF TRANSFECTED DNA
Authors: Mitchell David L. , Adair Gerald M. , Nairn Rodney S.
Published: January 2008

Abstract— The biological effectiveness of thymine‐thymine cyclobutane dimers specifically induced by photosensitized ultraviolet‐B irradiation was analyzed by host‐cell reactivation of triplet‐sensitized, UV‐B irradiated plasmid pRSVßgal DNA transfected into normal and repair‐deficient Chinese hamster ovary cells. For comparison, pRSVßgal DNA was also UV‐C irradiated and transfected into the same cell lines. Ultraviolet endonuclease‐sensitive site induction was determined after UV‐C irradiation or acetophenone‐sensitized UV‐B irradiation of plasmid pRSVßgal DNA. These data were used to calculate the number of cyclobutane pyrimidine dimers required to inactivate expression of the lacZ reporter gene in each irradiation condition. Transfection with UV‐C‐irradiated plasmid DNA resulted in a significantly greater reduction of reporter gene expression than did transfection with acetophenone‐sensitized UV‐B‐irradiated pRSVßSgal DNA at equivalent induction of enzyme‐sensitive sites. Since only a fraction of the inhibition could be accounted for by noncyclobutane dimer photoproducts, these results suggest that cytosine‐containing pyrimidine cyclobutane dimers may be more effective than thymine‐thymine dimers in inhibiting transient gene expression as measured in such host‐cell reactivation experiments in mammalian cells.
HIGH‐PERFORMANCE LIQUID CHROMATOGRAPHY‐BASED PURIFICATION OF FIREFLY LUCIFERASES
Authors: Branchini Bruce R. , Rollins Cynthia B.
Published: January 2008

Abstract— A simple procedure is described for purifying luciferases from firefly lanterns in greater than 50% yield. The key step in the method is high‐performance liquid chromatography (HPLC) using a Bio‐Gel TSK DEAE‐5PW analytical (75 times 7.5 mm) anion exchange column. In separate experiments, partially purified protein solutions obtained from Photinus pyralis and Photinus macder‐motti lanterns by solubilization, ammonium sulfate fractionation and Sephadex G‐25 gel filtration were chromatographed. Luciferases from both species had relative molecular masses (Mg) equal to 61 ± 2 times 103 and were strongly reactive to anti‐P. pyralis luciferase antibody. Isoelectric focusing (IEF) experiments, HPLC retention times (Rt), and bioluminescence emission spectra demonstrated that the luciferases from the different Photinus species were very similar, but not identical. The purification procedures described are most suitable for the isolation of 2–10 mg of protein; however, the use of a preparative column should enable the convenient isolation of larger amounts of protein. Also, this method should be readily adaptable to the isolation of luciferases from additional genera and species of fireflies.
TRANSIENT KINETICS OF FLAVOCYTOCHROME c PHOTOREDUCTION BY METHYL VIOLOGEN
Authors: Czege J. , Kovacs K. L.
Published: January 2008

Abstract— It has been demonstrated that photoreduced methyl viologen is stable during a flash photolysis experiment if a proper anaerobic environment is maintained. Therefore a new class of potential electron donors can be introduced in the study of transient phenomena associated with intermolecular electron transfer of redox proteins. The transient redox kinetic parameters of the flavocytochrome c from the photosynthetic bacterium Thiocapsa roseopersicina are reported for the first time and compared to similar data published for other fiavoproteins from diverse sources using flavin‐type electron donors. The advantages of the photoreduced viologen based transient electron donor system are discussed.
PHOTOELECTROCHEMICAL STUDIES OF ULTRATHIN PHOTOACTIVE (POLYMER) LAYERS VIA SENSITIZATION OF ZnO
Authors: Li Xue‐Ping , Tributsch Helmut
Published: January 2008

–Since photoelectrochemical properties of very thin (< 100 Å) layers of photoactive materials cannot be studied on metal contacts due to energy transfer losses and excessive dark currents through holes, an attempt was made to investigate them in contact with a large gap oxide semiconductor (ZnO). It was expected that electrons excited within the thin layer can be injected into the conduction band of ZnO. Experiments have shown this to be possible with the p‐type polymer semiconductor poly(2,5‐furylenvinylene) applied at thickness equivalent to 1–50 monolayers. Studies on complementary sensitization with Rhodamine B suggest energy transfer mediated electron transfer across the polymer layer into ZnO. In contrast, sensitization of ZnO by thin layers of n‐CdS or rc‐FeS2 (prepared by painting or MOCVD) was not successful. Promises and difficulties of the technique which could also be applied to biological samples are discussed.
ON THE ORIGIN OF LASER‐SPECIFIC LUMINESCENCE UPON PULSED‐LASER EXCITATION OF BENZOPHENONES IN FREONS†
Authors: Clark K. Brady , Scaiano J. C.
Published: January 2008

–Excimer laser excitation (308 nm) of benzophenone in Freon‐113, as well as in Freon‐11, results in an intense emission with λmax at approx. 530 nm in addition to triplet phosphorescence. This emission is shown to result from an excited free radical bearing the diphenylmethylene moiety which is generated in a two‐photon process and which luminesces upon sensitization by the benzophenone triplet. On the basis of its spectroscopic properties and the chemical nature of the system, it is suggested that the fluorescer in this system may be the hypochlorite radical, Ph2COCl.
ENERGY TRANSFER IN TRITON X‐405 MICELLES: THE EFFECTS OF TEMPERATURE AND BRIJ 35
Authors: Ndou T. T. , Wandruszka R. von
Published: January 2008

–Energy transfer from the phenyl groups of micellar Triton X‐405 (TX‐405) to solubilized pyrene molecules has been measured at a range of temperatures and in the presence of different polyoxyethylene 23 lauryl ether (Brij 35) concentrations. Increases in temperature lead to elimination of water from the outer, wet, micelle layer and an inward movement of associated pyrene. The addition of Brij also leads to a reduction in polarity of the microenvironment of pyrene. However, sensitization is observed even at high Brij concentrations. The donor/acceptor separation caused by the introduction of Brij proceeds slowly, continuing for several minutes after its addition to micellar TX‐405.
PHOTO‐CIDNP IN GUANINE NUCLEIC ACID DERIVATIVES. A MECHANISTIC STUDY
Authors: STOB S. , SCHEEK R. M. , KAPTEIN R.
Published: January 2008

Abstract— A mechanistic study of the photo‐CIDNP effect of guanosine derivatives is presented. The pH dependence of the CIDNP effect of 5′‐GMP shows a sign reversal at pH 3.3. Using methylated guanosine derivatives evidence has been obtained that the protonation state of the N7 atom influences the radical pair generation. The mechanism involves a guanine radical dication (protonated radical cation) at low pH and a radical cation at high pH. The CIDNP behaviour of 5′‐GMP is compared with that of 5′‐AMP, that was previously studied.
LOW COST DIGITAL SPECTRORADIOMETER*
Authors: KAUFMANN WOLFGANG F. , HARTMANN KARL M.
Published: January 2008

Abstract— A self‐made low cost digitized single beam spectroradiometer is described. It is designed and calibrated to measure spectral radiant intensities in one nanometer steps for bandwidths between 1 and 20 nm within the wavelength range 200–1100 nm. The voltage output of the photoelectric detector‐system is proportional to the logarithm of the received irradiance and so constant signal resolution is gained over more than three orders of radiant intensities. Raw data recording and processing is done by a common 8 bit microcomputer, programmed in Microsoft Basic. Scanned emission spectra of a far‐red fluorescent lamp and a long arc xenon discharge lamp are presented and compared to manufacturer's data. In addition, the emission spectrum of a blue fluorescent tube has been determined to test for photometric aptitude. In this context the integral irradiances have been both measured and calculated for three radiometric sensors of defined spectral responsivities, indicating reliability of the instrumentation.
NAPHTHYL‐ AND QUINOLYLLUCIFERIN: GREEN AND RED LIGHT EMITTING FIREFLY LUCIFERIN ANALOGUES
Authors: BRANCHING BRUCE R. , HAYWARD MATTHEW M. , BAMFORD SARAH , M. BRENNAN PATRICIA , LAJINESS EVELYN J.
Published: January 2008

Abstract

In the course of investigations on the possible involvement of the CIEEL (chemically initiated electron‐exchange luminescence) mechanism in firefly bioluminescence, we have synthesized two novel firefly luciferin substrate analogues. D‐Naphthylluciferin and D‐quinolylluciferin were prepared by condensing D‐cysteine with 2‐cyano‐6‐hydroxynaphthalene and 2‐cyano‐6‐hydroxyquinoline, respectively. These analogues are the first examples of bioluminescent substrates for firefly luciferase that do not contain a benzothiazole moiety. Firefly luciferase‐catalyzed bioluminescence emission spectra revealed that compared to the normal yellow‐green light of luciferin (γmax= 559 nm), the emission from naphthylluciferin is significantly blue‐shifted (γmax= 524 nm); whereas quinolylluciferin emits orange‐red light (γmax= 608 nm). The fluorescence emission spectra, reaction pH optima, relative light yields, light emission kinetics and KM values of the analogues also were measured and compared to those of luciferin. Neither of the analogues produced the characteristic flash kinetics observed for the natural substrate. Instead, slower rise times to peak emission intensity were recorded. It appears that the formation of an intermediate from the analogue adenylates prior to the addition of oxygen is responsible for the slow rise times. The synthetic substrate analogues described here should be useful for future mechanistic studies.
PHOTOSENSITIZATION TISSUE MODEL
Authors: SCHIFANO MICHAEL J. , GROSSWEINER LEONARD I.
Published: January 2008

Abstract— Photosensitization in a light scattering matrix was investigated with a tissue model consisting of polystyrene microsphere scattering particles, in the presence of a Photofrin II as a photosensitizing agent, and subtilisin Carlsberg as an enzyme target. The photodynamic rate constant for irradiation at 435 nm, 545 nm, and red light was measured at different microsphere concentrations. The reaction rate was almost independent of the microspheres, ruling out a significant effect of light scattering on the integrated photosensitization efficiency. Modeling with the one‐dimensional diffusion approximation showed that increasing scatterer concentrations led to lower transmission and higher diffuse reflection, such that the fractional absorption was almost constant. The quantum efficiency of enzyme inactivation in the light‐scattering systems was 0.0014 ± 0.0003. In terms of incident dose, red and green light had approximately the same effectiveness and blue light was two‐fold more efficient.
x‐RAY PHOTOELECTRON VALENCE BAND STUDIES ON FIREFLY D‐(‐)‐LUCIFERIN
Authors: WADA NAOHISA , SHIBATA RIKUO , SHIBAZAKI MASAVUKI , SUZUKI NOBUTAKA
Published: January 2008

Abstract— The valence band spectrum of firefly D‐(‐)‐luciferin (Ln) was measured for the first time by x‐ray photoelectron spectroscopy (XPS). Since the conversion of Ln to decarboxydehydroluciferin (dcrL) by x‐ray irradiation occurred even within ∼30 min, the effect of the irradiation on the valence band spectrum of Ln was investigated quantitatively. We found that the XPS valence band spectrum of Ln during irradiation for 3 h corresponds to the state density of Ln calculated by the LCAO‐ASMO‐SCF‐CI method for π‐electrons. Moreover, the weak coupling model for π‐electron transfer between Ln and oxygen was proposed for the primary electronic process in Ln chemiluminescence, assuming that the calculated π‐electron state densities of Ln in acidic and basic solutions reflect the characteristics of their XPS valence band spectra.
MECHANISMS OF PHOTOELIMINATION REACTIONS OF ALKYL BENZOHYDROXAMATES
Authors: Johnson James Elver , Arfan Mohammad , Hodzi Richard , Caswell Lyman R. , Rasmussen Susan
Published: January 2008

Abstract— Photolysis at 254 nm of alkyl benzohydroxamates [C, H, CONHOR: R = CH3 H2CH3 CH(CH3)2, CH2C6H5 CH(CH3)C2H5 CH(CH3)‐n‐C6H13] in acetonitrile or hydrocarbon solvents gives benzamide. These reactions can be sensitized by benzophenone (at ca. 350 nm) and are quenched by cis‐piperylene. Racemization occurred when 2‐octyl (+)‐benzohydroxamate was irradiated in cyclohexane. These results are consistent with a mechanism involving a triplet biradical. Photolysis of phenyl benzohydroxamate [C6H5CONHOC6H5] and benzyl N‐methylbenzohydroxamate [C6H5CON‐(CH3)OCH2Q6H5] cannot be quenched with ris‐piperylene and appear to be singlet reactions.
PHOTOCHEMICAL and PHOTOPHYSICAL PROPERTIES OF PIROXICAM and BENOXAPROFEN IN VARIOUS SOLVENTS
Authors: Becker Ralph S. , Chakravorti Sankar , Yoon Minjoong
Published: January 2008

Abstract— Laser flash spectroscopy was used to examine the title compounds. Piroxicam has a triplet transient with a maximum near 450 and a lifetime of 3–21 μs depending on the solvent. The relative quantum yield is highly solvent dependent being maximum in toluene and 14 fold lower in hydrogen bonding solvents. There is another transient which is assigned as a proton transferred ground state transient. Some permanent photoproduct also appears to be produced. Benoxaprofen also has a triplet transient with a maximum near 420 nm with a lifetime of 65 μs to 250 μs depending on the solvent. In this case, the relative quantum yield only slightly varies among polar and hydrogen bonding solvents. This is in marked contrast to published data on the fluorescence yield. Some permanent photoproduct appears to be produced.
THE PHOTOCHEMISTRY OF ACETYL‐SUBSTITUTED AROYL AZIDES: THE DESIGN OF PHOTOLABELING AGENTS FOR INERT SITES IN HYDROPHOBIC REGIONS
Authors: Melvin T. , Schuster Gary B.
Published: January 2008

Abstract— The photochemistry, photophysics and hydrolytic stability of three substituted aroyl azides were investigated. The azides were selected as model compounds for potential photolabeling agents based on the extreme electrophilic reactivity of aroylnitrenes. Each of the azides studied is a derivative of benzoyl azide containing an acyl group to act as an internal triplet sensitizer and an additional functional group useful for linking the azide to a site‐selecting probe molecule. The findings show that benzoyl azides containing the three substituents in a 1,3,5‐pattern might be useful for labeling of lipophilic molecules.
INTRAMOLECULAR DONOR‐ACCEPTOR SYSTEMS: STRUCTURES OF NOVEL LINKED PORPHYRIN‐ PHENOLPHTHALEIN MOLECULAR SYSTEMS
Authors: D'Souza Francis , Krishnan V.
Published: January 2008

Abstract— Intramolecular donor‐acceptor systems bearing porphyrins covalently linked to phenol‐phthalein at various distances and at different orientations have been synthesized. Optical absorption and emission spectra and magnetic resonance studies reveal interaction between the porphyrin unit and lactone/semiquinone forms of phenolphthalein. The charge‐transfer quenching of fluoresence in these systems is found to be more pronounced compared to the intermolecular systems. The lifetime studies are interpreted in terms of intramolecular electron transfer.
REPAIR OF UV‐DAMAGED INCOMING PLASMID DNA IN Saccharomyces cerevisiae
Authors: Keszenman‐Pereyra David
Published: January 2008

Abstract— A whole‐cell transformation assay was used for the repair of UV‐damaged plasmid DNA in highly transformable haploid strains of Saccharomyces cerevisiae having different repair capabilities. Six rad alleles were selected from the three epistasis groups: radl‐1 and rad2‐l from the RAD3 group, rad6‐l and rad18‐2 from the RAD6 group, and rad52‐l and rad54‐1 from the RAD52 group. Cells carrying single, double and triple rad alleles were transformed to uracil prototrophy by centromeric plasmid DNA (YCp19) modified in vitro with UV (254 nm). Surviving fractions were calculated as the number of transformants at each fluence relative to the number of transformants with unirradiated plasmid DNA. The sensitivity of incoming DNA in single rad mutants shows that most repair is carried out by excision repair and a TMD/S‐dependent process. In the rad52‐l host, the sensitivity of incoming DNA was intermediate between those found in RAD+ and rad2‐I hosts, suggesting the involvement of a recombinational repair process. Non‐epistatic interactions were observed between rad alleles belonging to different epistasis groups. This provides validation for the classification of the three epistasis groups concerning the repair of chromosomal DNA for UV‐incoming DNA. In both rad7‐7 radb‐1 and radl‐1 rad18‐2 rad54‐l hosts, the mean fluence for one lethal event corresponds approximately to one pyrimidine dimer per plasmid molecule, indicating that they are absolute repairless hosts for incoming DNA. A comparison between cell and plasmid survival reveals that there are differences in the repairability of both chromosomal and incoming DNA. The large effect of rad6‐l mutation on cell survival and the small effect on incoming DNA suggest that, in the RAD+ strain, the RAD6 product may be essential for the repair processes which act on chromosomal DNA, but not for those which act on incoming DNA. It is proposed that in yeasts postreplication repair of incoming DNA is limited to supercoiled molecules with1–2 pyrimidine dimers that can initiate replication.
PHOTOPHYSICAL PROPERTIES OF 2‐NITRO‐5,10,15,20‐TETRA‐p‐TOLYLPORPHYRINS
Authors: Gust Devens , Moore Thomas A. , Luttrull David K. , Seely Gilbert R. , Bittersmann Edith , Bensasson René V. , Rougée Michel , Land Edward J. , Schryver F. C. De , Auweraer M. Van der
Published: January 2008

Abstract— Tetraarylporphyrins substituted with nitro groups at fipyrrolic positions are potential candidates for electron‐accepting pigments in model systems for photosynthesis. The photophysics of 2‐nitro‐5,10,15,20‐tetra‐p‐tolylporphyrin and its zinc analog have been studied in order to evaluate this potential. The ground state absorption spectrum, the triplet‐triplet absorption spectrum, the fluorescence emission spectrum, and associated photophysical parameters have been determined. The molecules have short singlet lifetimes and anomalous temperature‐ and solvent‐dependent emission spectra which are consistent with the formation of an intramolecular charge transfer state of the type P+ ‐NO2; in which the nitro group is twisted about its bond to the porphyrin, relative to the ground state conformation.
ANALYSIS OF THE DIURNAL EXPRESSION PATTERNS OF THE TOMATO CHLOROPHYLL alb BINDING PROTEIN GENES. INFLUENCE OF LIGHT and CHARACTERIZATION OF THE GENE FAMILY*
Authors: Kellmann J.‐W. , Pichersky E. , Piechulla B.
Published: January 2008

Abstract— Steady‐state mRNA levels of the chlorophyll alb binding (cab) proteins oscillate substantially during a diurnal cycle in tomato leaves. This accumulation pattern is also observed in complete darkness, supporting the hypothesis that the expression of cab genes is at least partially regulated by an endogenous rhythm (“biological clock”). The amplitude of the cab mRNA accumulation is dependent on the duration of illumination and the circadian phase in which light was applied to the tomato plants. These results at the molecular level correlate well with the photoperiodic phenomenon. The characterization of the expression pattern of individual members of the cab gene family was attempted. Distinct primer extension products were detected using specific oligonucleotides homologous to the cab 1, cab 4, cab 5 and cab 8 genes. Based on this analysis the transcription start sites of these genes were determined to be between position ‐70 and ‐9 upstream of the ATG codon. During the diurnal cycle the cab 1 and cab 4 genes exhibit the same expression pattern; no transcripts detected at 3 and 6 a.m., maximum mRNA levels were measured at noon and decreasing levels in the afternoon.
ACTION SPECTRUM FOR PHOTOREVERSION OF THE ACTIVE Pfr‐FRACTION OF Mougeotia in vivo
Authors: Fischer C. , Kraml M.
Published: January 2008

Abstract— The dichroic oriented fraction of the far‐red light absorbing form of phytochrome (Pfr) in the green alga Mougeotia was characterized by action spectroscopy. Microbeam irradiations had to be used for the induction of chloroplast movement in Pfr‐containing cells, because of the special dichroic absorption characteristics of the red light absorbing form of phytochrome (Pr) and Pfr in the alga. Fluence‐response curves were elaborated especially in the far‐red spectral region by reverting Pfr to Pr at the flanks of the cells and thus generating Pfr‐gradients. Linearly polarized light vibrating perpendicularly to the cell axis was used, thus corresponding to the S,‐transition moments of Pfr at the flanks of the cells. The action spectrum is characterized by a peak at approximately 715 nm and a very pronounced decrease towards 728 and 734 nm. The data indicate that the spectral absorption of the active Pfr‐fraction in green Mougeotia is shifted towards shorter wavelengths as compared to extracted phytochrome from etiolated or even green higher plants. This “blue shift” seems to be typical for Pfr from green lower plants.
PHOTOTROPISM–THE NEED FOR A SENSE OF DIRECTION?
Authors: Firn R. D.
Published: January 2008

Abstract— The ill defined nature of the conceptual framework used to guide research on phototropism is a handicap to progress. It is argued that some of the central concepts, such as the stimulus perception‐transduction‐response chain, have not given a useful sense of direction. Likewise the arguments as to whether hormones are involved in phototropism have now become a distraction. A constructive phase is now needed, building on an agreed framework. There is an urgent need to identify the universal elements of phototropism and to distinguish those elements from the ones which apply only in specialised cases.
KINETIC STUDIES ON ANTHRALIN PHOTOOXIDATION
Authors: Müller Klaus , Kanner Richard C. , Foote Christopher S.
Published: January 2008

Abstract— The photooxidation of the antipsoriatic drug anthralin (1,8‐dihydroxy‐9‐anthrone) has been studied by several kinetic techniques, including direct observation of 1O2 (1Δg) luminescence at 1.27 μm. The rate of deactivation of 1O2 increases at higher pH, demonstrating that the trihydroxy‐anthracene anion is the reactive species. Direct determination of the rate constant of 1O2 deactivation (kR+kQ) in deuterated buffer systems by luminescence quenching gave a value of 3.0 times 108M−1−1 for the anion; the neutral anthrone is unreactive. The rate constant for the neutral anthrone in benzene‐d6 is 2.8 times 104 M−1 s−1 Competition experiments with tetramethylethylene in acetonitrile gave a rate constant for reaction alone (kR) of 2.1 times 108 M−1 s−1 for the anion.
THE ROLE OF CALCIUM IN Chlamydomonas PHOTOMOVEMENT RESPONSES AS ANALYSED BY CALCIUM CHANNEL INHIBITORS
Authors: Hegemann P. , Neumeier K. , Hegemann U. , Kuehnle E.
Published: January 2008

Abstract— Phototaxis and light‐induced stop responses in Chlamydomonas are known to be calcium dependent. We show that phototaxis is stereoselectively inhibited by dihyropyridines, verapamil, diltiazem, ω‐conotoxin and pimozide, all inhibitors of slow L‐type calcium channels. In contrast, the stop response in Chlamydomonas can be specifically reduced only by ω‐conotoxin and pimozide. The light‐regulated calcium uptake as detected by 45calcium can be completely suppressed by verapamil and ω‐conotoxin but not by diltiazem or any of the dihyropyridine‐type calcium channel inhibitors. We conclude that phototaxis and stop response in Chlamydomonas are regulated by three distinguishable drug receptor sites. One of them controls phototaxis and is sensitive to verapamil. The second site controls stop response and phototaxis and shows a high sensitivity to ω‐conotoxin and pimozide. These two drug receptors seem to be localized in the plasma membrane and function as ion channels. In addition, calcium influences internal signal transduction from the photoreceptor to the flagella. This internal role of calcium is inhibited by the dihydropyridine binding to a dihydropyridine receptor protein.

The arylazide‐l,4‐dihydropyridine[3H]azidopine binds with a Kd= 35 nM to a 50 kDa protein located in one of the internal cell membranes. Azidopine binding is fully reversible and can be partially inhibited by nimodipine and PN‐200110. This protein is the first identified dihyropyridine receptor in an unicellular plant cell. It might serve as an internal calcium regulating channel in Chlamydomonas.
FLUOROMETRIC ANALYSIS OF THE LONG‐WAVELENGTH ABSORPTION BAND OF N‐7 METHYLATED GMP INTO THE CONSTITUENT BANDS OF THE TWO ELECTRONIC STATES
Authors: Ge Guangyuan , Zhu Shen , Bradrick Thomas D. , Georghiou S.
Published: January 2008

Steady‐state measurements of fluorescence anisotropy are used to resolve the long‐wavelength absorption spectrum of 7‐methyl guanosine 5′‐monophosphate (GMP) in pH 5 buffer at room temperature into component spectra that correspond to the electronic transitions I and II present in that spectral region. We have chosen this derivative of guanine because its fluorescence quantum yield is much greater than that of GMP. It is found that the data are adequately described by a model that involves emission exclusively from state I, with state II converting to it with 100% efficiency. The shape of the absorption spectrum of state II is virtually independent of the angle 6 between the absorption transition dipole moments of states I and II, whereas that of state I is dependent on 9. We analyze the data on the basis of the premise that in the short‐wavelength region state II is the predominantly absorbing state. This premise is based on studies of single‐crystal polarized reflection and linear dichroism from stretched films. The spectral maxima for the two states are found to be at about 290 and 260 nm, respectively. There is also a weak band which is centered at about 245 nm. The oscillator strengths are found to be 0.07, 0.21 and ‐ 0.04, for states I, II and that associated with the weak band, respectively. The importance of these findings with regard to the photophysical properties of nucleic acids and calculations of their CD spectra is discussed.
MOLECULAR STRUCTURE AND PHOTODECARBONYLATION OF 2,3,4,5‐ TETRAPHENYLCYCLOPENTANONE
Authors: Lewis Frederick D. , Field Theodore L. , Sabat Michal
Published: January 2008

Abstract—

Clemmensen reduction of tetracyclone yields r‐2,t‐3,t‐4,c‐5‐tetraphenylcyclopentanone, the structure of which was established by x‐ray crystallography. Photodecarbonylation of this molecule results in the formation of cis‐ and trans‐stilbenes and minor amounts of tetraphenykyclobutane. The stilbenes are initially formed in comparable yield, but secondary photoisomerization results in cw‐rich mixtures. Stepwise photodecarbonylation is proposed to yield triplet meso‐ 1,2,3,4‐tetraphenylbutane‐diyl which undergoes nonstereoselective elimination in preference to cyclization. The intermediacyof the same biradical in the photodimerization stilbene can be effectively eliminated on the basis of stereochemical evidence.
THEORETICAL STUDY OF ELECTRONIC SPECTRA AND PHOTOPHYSICS OF URACIL DERIVATIVES*
Authors: Baraldi I. , Brum M. C. , Costi M. P. , Pecorari P.
Published: January 2008

Abstract—

The changes that the UV absorption spectrum and the photophysics of uracil undergo under hydrogen substitution or deprotonation, were studied theoretically within the CS‐INDO/CI scheme. First of all this method was tested on uracil. It was then used for the calculation of the electronic structure of excited states (Sn, Tn) of a large number of uracil derivatives (1‐, 3‐ and 5‐methyluracil; 1,3‐, 1,5‐ and 3,5‐dimethyluracil; 5‐fluoro‐ and 5‐chlorouracil), including some anions (1‐ and 3‐methyluracil anion). The excited states were obtained in the singly‐excited configuration interaction approximation (S‐CI) and the correlation effects on (ππ*) states were studied by including the most important doubly‐ and triply‐excited configurations in the CI. The S‐CI wavefunctions were used for the calculation of the most important electronic matrix elements for spin‐orbit coupling. The photophysics of these compounds is discussed using Jablonski diagrams.
HETEROGENEOUS PHOTO CATALYSIS–VII. THE INFLUENCE OF ZINC IONS ON THE PHOTOCATALYTIC PROPERTIES OF PLATINIZED CADMIUM SULFIDE
Authors: Hetterich Wolfgang , Kisch Horst
Published: January 2008

Abstract— The reaction rate of the CdS/Pt‐catalyzed hydrogen evolution and photodehydro‐dimerization from aqueous 2,5‐dihydrofuran depends strongly on the reaction conditions in the preparation of CdS/Pt by photoplatinization. Highest rates, 12 ml H2/h, are obtained when the photocatalyst was prepared with a low‐intensity lamp in the presence of 4.3 mol% of platinate (sample I) while lower rates are observed with 1.07, 2.15, 3.23 and 6.45 mol% Pt. At higher intensity and 4.3 or 2.15 mol% Pt the produced samples II and III induce rates of 5 or 2.5 ml H2/h. Addition of zinc sulfate to the 2,5‐dihydrofuran solution results in a maximum rate increase to 7.5 and 12.5 ml H2/h in the case of II and III, respectively. Similarly, zinc sulfate improves the catalytic properties also when it is present during photoplatinization. In this case only half the amount of platinum, 2.15 mol%, is necessary to obtain the highest rates of 12 ml H2/h.
In vitro PHOTODYNAMIC ACTIVITY OF KRYPTOCYANINE
Authors: Harriman Anthony , Luengo Gustavo , Gulliya Kirpal S.
Published: January 2008

Abstract— –The photophysical properties of 1,1′‐diethyl‐4,4′‐carbocyanine chloride (kryptocyanine) have been measured in methanol solution and for the dye bound to human serum albumin, incorporated in neutral micelles and after incubation with leukemia cells. In all cases, it is found that formation of the triplet state of the dye occurs with low efficiency and that illumination of the dye under aerobic conditions does not produce significant yields of O2(1δg). Instead, the only efficient photoprocess involves rapid internal conversion from the first excited singlet state to the ground state, probably via isomerization of the polymethine sequence. These findings are discussed with respect to the demonstrated ability of kryptocyanine to photodestroy leukemic cells.
REDOX PROTEINS AS ELECTRON ACCEPTORS FROM CHLOROPHYLL TRIPLET STATE IN LIPID BILAYER VESICLES: KINETICS OF REDUCTION OF MEMBRANE RECONSTITUTED CYTOCHROME c OXIDASE MEDIATED BY 2,5‐DI‐t‐BUTYL BENZOQUINONE AND CYTOCHROME c
Authors: Chamupathi V. G. , Moezzi D. M. , Tollin G.
Published: January 2008

Abstract— Laser flash photolysis was used to determine the kinetics of electron transfer between membrane‐bound triplet chlorophyll (3C), cytochrome c (cyt c) located in the external water phase, and vesicle‐reconstituted cytochrome c oxidase (CCO). 2,5‐Di‐t‐butyl benzoquinone (2,5 TBQ) was used as an electron transfer mediator between 3C and cyt c. A light‐induced cyclic electron transfer sequence between the redox components was observed (3C → 2,5 TBQ → cyt c→ CCO → C+). Under optimum conditions of membrane surface charge and ionic strength, the overall efficiency of CCO reduction (based on 3C generated by the laser flash) was 14%. Under the anaerobic conditions used, CCO reoxidation (occurring via electron transfer to C+) was quite slow (halftime approx. 1 s at 75 mM ionic strength). The multicomponent system displayed a high level of stability, as indicated by its ability to undergo many cycles of reduction and reoxidation without any apparent degradation of the components. These results demonstrate the feasibility of constructing complex electron transfer chains, including both soluble and membrane‐bound redox proteins, in artificial lipid bilayers, whose properties can be readily controlled by manipulating parameters such as ionic strength and membrane composition.
POLARIZATION STUDY OF 5(E)‐STYRYL‐1,3‐DIMETHYL URACIL IN DIISOOCTYL SULFOSUCCINATE (AEROSOL‐OT) REVERSED MICELLE SOLUTIONS
Authors: Shin Dong‐Myung , Kim Sung Woong , Shim Sang Chul
Published: January 2008

The degree of polarization around the water pool generated in aerosol‐ OT/hexane/water reversed micelle solutions was studied by monitoring the depolarization of solubilized probe fluorescence. The 5(E)‐styryI‐1, 3‐dimethyl uracil (SDU) used in this study was moderately polar and proved to be solubilized between the interface and hydrocarbon phases in reversed micelle solution by a fluorescence quenching study with hydrophilic and hydrophobic quenchers. The degree of polarization monitored by SDU was parallel with that obtained from the fluorescence depolarization study of hydrophylic probes solubilized in the water pool and interface. A dramatic increase in microviscosity was observed when ω value became small.
TIME‐RESOLVED SPECTROSCOPIC STUDIES ON PHOTOPHYSICAL PROPERTIES OF BENOXAPROFEN IN MICELLAR SOLUTIONS: AN INTRAMICELLAR FLUORESCENCE QUENCHING
Authors: Yoon Minjoong , Chang Jae Rim , Kim Dongho , Kuriyama Yasunao , Tokumaru Katsumi
Published: January 2008

The micellar dependencies of the photophysical properties of benoxaprofen (BXP), a 2‐phenyl benzoxazole derivative, have been investigated using fluorescence spectroscopy and laser flash photolysis techniques. The fluorescence of BXP in aqueous solution has been observed to be remarkably quenched upon addition of a surfactant, cetyltrimethyl ammonium bromide (CTAB) or Triton X‐100, in contrast to its enhancement in sodium dodecyl sulfate (SDS) micellar solution. Time‐resolved fluorescence measurements show that the fluorescence decays biexponentially in the micellar solution, indicating the relaxation of micellar environments surrounding the excited BXP. The major component of fluorescence lifetimes in CTAB or Triton X‐100 micellar phase is even shorter (330–427ps) than in SDS micellar phase (731 ps). The nonradiative decay constants are significantly larger (ca 3.0 times 109 s−1) in the CTAB or Triton X‐100 micellar phase than in SDS micelles by a factor of ca 10. The major nonradiative decay is interpreted to be the internal conversion due to nuclear geometric change of BXP in the first excited singlet state. This is consistent with the observation that the quantum yields of intersystem crossing are very low (less than 0.01) in the micellar solutions as determined by the laser flash photolysis technique. The laser‐induced transient absorption spectrum of BXP in CTAB or Triton X‐100 micellar solution shows that the decay kinetics of the transients in CTAB or Triton X‐100 are significantly different from first order kinetics in SDS.
LOW TEMPERATURE POLARIZED ABSORPTION MICROSPECTROSCOPY OF SINGLE CRYSTALS OF THE REACTION CENTER FROM Rhodobacter sphaeroides WILD TYPE STRAIN 2.4.1
Authors: Frank Harry A. , Aldema Mila L. , Violette Carol A. , Parot Pierre H.
Published: January 2008

The absorbance and polarized absorbance spectra of single crystals of the reaction center complex isolated from Rhodobacter sphaeroides wild type strain 2.4.1 have been measured at 85 K. The crystals of the complex were obtained by the vapor diffusion technique. The spectroscopic experiments on the crystals were performed using an optical microspectrometer featuring a custom‐built, liquid N2‐flowing cold stage, the details of which are presented herein. These data demonstrate the feasibility of conducting optical spectroscopic experiments at cryogenic temperatures on single crystals of photosynthetic pigment‐protein complexes.
QUENCHING OF FLUORESCENCE OF AROMATIC HYDROCARBONS BY PROTONS IN CAFFEINE‐ SOLUBILIZED AQUEOUS SOLUTION. INTRACOMPLEX ENERGY TRANSFER
Authors: Nosaka Yoshio , Kira Akira
Published: January 2008

The fluorescence of pyrene and five other aromatic hydrocarbons solubilized with caffeine in aqueous solution was quenched by 0.001–1mol dm−3 sulfuric acid; this quenching did not occur in the absence of caffeine. Exceptionally a non‐alternative hydrocarbon, fluoranthene, showed an increase of the fluorescence intensity by the acid. The observed quenching rate was explained by the rate of energy transfer from the aromatic molecules to protonated caffeine in the complex.
FAR‐INFRARED SPECTRA OF LANGMUIR‐BLODGETT FILMS OF CHLOROPHYLL a, CHLOROPHYLL b, PHEOPHYTIN a and THEIR ADDUCTS WITH WATER and DIOXANE*
Authors: Tajmir‐Riahi Heidar‐Ali , Wang Gongming , Leblanc Roger M.
Published: January 2008

Fourier transform infrared spectra in the low frequency region (500–150cm−1) of Langmuir‐Blodgett films of chlorophyll a (Chi a), chlorophyll b (Chi b) and pheophytin a have been studied. Correlations between spectral changes in monolayer and multilayers of Chi a and Chi b and their adducts with water and dioxane have been established.

Spectroscopic evidence has indicated that, although there are no individual absorption bands that can be assigned to pure Mg‐nitrogen and/or Mg‐oxygen stretching or bending modes, there are several bands in the400–200 cm−1 region of the spectra containing considerable contributions from metal‐nitrogen and metal‐oxygen vibrational modes. These specific vibrations exhibit marked intensity changes and shifts upon water and dioxane interaction. The different states of chlorophyll aggregation in Langmuir‐Blodgett mono‐ and multilayers films resulted in noticeable changes in their far‐IR spectra.
IDENTITY OF THE PHOTORECEPTORS FOR THE PERCEPTION OF IRRADIANCE IN PHOTOSYNTHETIC LIGHT ACCLIMATION IN TOMATO*
Authors: Withers A. C. , Vince‐Prue D. , Thomas: B.
Published: January 2008

References

The photoreceptors involved in the photosynthetic acclimation of tomato (Lycopersicon esculentum Mill.) to increased irradiance were investigated. Plants were transferred from 100 p.mol m−2 s−1 cool white fluorescent light to higher irradiances of white light or white light supplemented with blue, red, green or yellow light. In these experiements light of all wavelengths tested was capable of causing acclimation as measured by the rate of light‐saturated photosynthesis. It was concluded that the photosynthetic system rather than the blue‐absorbing photoreceptor or phytochrome system acts as the photoreceptor for increased irradiance. No acclimation was observed in response to increased CO2 levels, but increasing light integral at a constant irradiance was effective in bringing about acclimation. We conclude that acclimation is a response to increased photosynthetic light capture rather than increased photosynthetic carbon fixation, and involves a photon counting mechanism.
PHOTOCHEMICAL trans →cis ISOMERIZATION OF 6‐STYRYLQUINOXALINE*
Authors: Kim Maeng Sup , Lee Ki Taek , Jeong Bong Mo , Lee Bok Hee , Shim Sang Chul
Published: January 2008

The trans → cis photoisomerization of fran.s‐6‐styrylquinoxaline (6‐StQx) has been investigated. Fluorescence quantum yields increase with increasing solvent polarity, whereas internal conversion and intersystem crossing decrease because of the weakening of vibronic coupling of the lowest 1(π,π*) state and 1(n,π*) state in polar solvents. Laser flash photolysis studies show an efficient singlet‐triplet intersystem crossing on direct irradiation at room temperature. Azulene quenching of fluorescence, and direct and sensitized photoisomerization indicate that the direct photoisomerization proceeds through both the singlet and triplet manifolds, mainly via the triplet state (75‐80%) at room temperature, in contrast to corresponding hydrocarbons.
TRANSLATIONAL MOBILITY IN THE ADSORBED STATE. BIMOLECULAR DEACTIVATION KINETICS OF LASER‐EXCITED AZAAROMATICS ON MICROPOROUS SILICA*
Authors: Oelkrug D. , Gregor M. , Reich S.
Published: January 2008

A series of polycondensed aromatic N‐heterocycles (acridine, benzo‐f‐quinoline 1,2,7,8‐dibenzacridine and 3,4,5,6‐dibenzacridine) were adsorbed from the gas phase and from liquid solution on highly dispersed silica gels with very different specific surface areas and pore sizes. The translational mobility of the adsorbed species was quantified by the triplet decay and the delayed fluorescence following bimolecular triplet‐triplet annihilation after pulsed laser irradiation. The decay kinetics were analyzed with conventional second order rate equations and with the fractal approach. The first method is reliable without limitations on adsorbents with large pore diameters. It yields second order annihilation constants of 4 times 1012‐6 times 1011 dm2 mol−1 s−1 depending on the masses and sterical requirements of the adsorbates. For the second method a spectral dimension ds= 4/3 was used. This method is quantitatively applicable to all heterocycles adsorbed on silica gel 60 that have very small pore sizes. An activation energy of 4.9 ± 0.5 kcal mol−1 was obtained for the translational diffusion of acridine on hydroxylated silica gel.
KINETICS OF LUMINESCENCE QUENCHING IN MICELLAR ASSEMBLIES INCLUDING EXCHANGE OF PROBE and QUENCHER*
Authors: Gehlen M. H. , Auweraer M. Van der , Schrwer F. C. De
Published: January 2008

The luminescence decay of excited probes in micelles in the presence of a Poisson distribution of quenchers is considered under conditions where both probe and quencher within the lifetime of the excited probe may exchange between the micelles. Analytical and numerical results show that the luminescence decay can be expressed by a generalized self convolution product of a multiexponential decay function.