bluuebunny/crossref_metadata_2025 huggingface dataset:
INTERMEDIATES IN THE PHOTOCONVERSION OF FUNCTIONAL PHYTOCHROME IN FERN SPORES OF Dryopteris‐I DEMONSTRATION AND QUANTITATIVE CHARACTERIZATION OF THE PHOTOCHROMIC SYSTEM Pr⇔ Ii700USING NANOSECOND‐LASER PULSES*,†
Authors: Scheuerlein R. , Koller D.
Published: January 2008

Abstract— Spores of Dryopteris paleacea and D. filix‐mas are positively photoblastic with an optimum in the action spectrum around 665 nm. Light is perceived by phytochrome and the relationship between germination and mole fraction of the far‐red‐absorbing form of this pigment, Pfr, was investigated with saturating irradiations between 662 and 747 nm under low‐fluence‐rate conditions. These control irradiations establish a proportion of the total phytochrome, P,tot, as Pfr with Pfr/Ptot–φ at equilibrium. These φ ‐values were calculated according to data for native oat phytochrome (Kelly and Lagarias, 1985, Biochemistry 24, 6003) and the spectral characteristics of the interference filters. With this method a linear relationship could be found between φ and germination from 2 to 70% for D. paleacea and from 2 to 90% for D. filix‐mas, if probit germination was plotted vs probit φ

This correlation formed the basis of investigating the phytochrome photoconversion by dye‐laser pulses of 380 ± 30 ns under high‐fluence‐rate conditions, and thus to test quantitatively the impact of the photoreversibility of intermediate reactions of the photoconversion and the red‐absorbing form of phytochrome, Pfr on the final Pfr‐level. Spore germination was initiated by a single‐laser pulse in the range from 592 to 700 nm. The most effective wavelengths were 649 and 660 nm in both species, and at saturation maximal germination (ca. 50%) was obtained from 592 to 665 nm for D. paleacea or ca. 60% germination from 592 to 670 nm for D. filix‐mas. Both saturation levels correspond to a ø‐value between 0.40 and 0.45. This significantly diminished photoconversion is a consequence of the high‐fluence‐rate conditions during the laser pulse which establishes the photochromic system between Pr and a set of very early intermediates, Ii700, (= Pr⇔ Ii700). This system can be described by the extinction coefficients of Pr and the intermediates Ii700, and by the quantum yields, 4,φ for the forward and reverse reactions as φ If φ is calculated, assuming a quantum yield of 1:1 for both reactions and with the extinction coefficients of Pr and Ii7(l() (= lumi‐R) given by Eilfeld and Riidiger (1985, Z. Naturforsch.40c, 109), significantly higher values are calculated for / as compared to φ found in the control experiments.

These results can be explained either: (i) with a quantum yield ratio φpr‐φ1700: φ1700φpr=1:1 and an assumed additional dark reaction leading from Ii700 or later intermediates back to Pr: or (ii) with a quantum yield ratio φpr φ 1700: φ1700 φpr=1:2. In this case all Ii700 have to relax to Pfr. In this case all Ii700 have to relax to Pfr.
INVESTIGATION OF DAMAGE TO FOREST BY EPR SPECTROSCOPY in vivo
Authors: Stegmann H. B. , Schuler P. , Ruff H.‐J.
Published: January 2008

Abstract—

Spruce needles collected from several trees of the Black Forest were investigaled by EPR spectroscopy. These needles show in the g = 2.00 region a signal IIS(Tyr D +) and a light‐induced signal I(P700+) and a Mn2+ hyperfine structure which superimposes the other absorptions. Difference spectra, light minus dark, partly eliminate the manganese hyperfine structure, and P700+ can be observed. By comparison of these EPR signals with those of spinach chloroplast or thylakoid membranes described in the literature, significant deviations were observed, whereas several trees grown in the vicinity of Tubingen exhibit the well known D+ and P700+ EPR spectra. After treatment of branches of these ‘normal’ trees with herbicides like Amitrol and Roundup or chemicals like toluene or trichlormethane the EPR signals obtained are comparable with those observed with needles of the Black Forest.
STACKED ZINC TRIPORPHYRIN AS A PHOTOINDUCED MOLECULAR WIRE IN BILAYERS
Authors: SETA P. , BIENVENUE E. , MAILLARD P. , MOMENTEAU M.
Published: January 2008

Abstract

A molecule with three stacked zinc‐porphyrin cycles and two basket‐handles has been synthesized and incorporated into a bilayer lipid membrane. Under light excitation and in the presence of redox compounds in the aqueous phases bathing the membrane, this molecule induces a net electron flux across the membrane. The experimental variations of the flux with some external physicochemical parameters are accounted for by a tentative mechanism which relies on the ability of the porphyrin to act as an electron wire.
A PULSE RADIOLYSIS and PULSED LASER STUDY OF THE VITAMIN D3 TRIPLET STATE: LIFETIME, RELAXATION and ‘NONVERTICAL’EXCITATION
Authors: Gorman A. A. , Hamblett I. , Lambert C. , Prescott A. L.
Published: January 2008

Abstract— The triplet state of vitamin D3 in benzene has been characterised in terms of its absorption spectrum, Λmax 315 nm, its lifetime, 300 ns, its rate constant for reaction with oxygen, 4.2 times 109mol−1 s−1 and the efficiency with which it sensitizes the formation of singlet oxygen, 25%. There is a large difference in the electronic excitation energies of the spectroscopic and relaxed triplets, ˜ 237 kJ mol−1 and147–168 kJ mol−1, respectively. It has been shown that, in the endothermic situation, the vitamin D3 molecule is a 'nonvertical'acceptor of triplet energy. This is in accord with the non‐planar character of its acyclic conjugated Il‐system.
PHOTOCHEMICAL RING‐OPENING IN meso‐CHLORINATED CHLOROPHYLLS
Authors: Struck A. , Cmiel E. , Schneider S. , Scheer H.
Published: January 2008

Abstract— Irradiation of 20‐chloro‐chlorophylls of the a‐type with visible light produces long‐wavelength shifted photoproducts, which transform in the dark to linear tetrapyrroles (bile pigments). The possible significance for chlorophyll degradation is discussed.
BIOLOGICAL ACTIVITIES OF PHTHALOCYANINES‐XL PHOTOTOXICITY OF SULFONATED ALUMINUM NAPHTHALOCYANINES TOWARDS V‐79 CHINESE HAMSTER CELLS
Authors: Paquette Benoit , Ali Hasrat , Langlois Rejean , van Lier Johan E.
Published: January 2008

Abstract— The phototoxicity of sulfonated aluminum naphthalocyanines towards V‐79 Chinese hamster cells is investigated. The disulfonated naphthalocyanine exhibits similar photostability, but better cell penetrating properties than the tetrasulfonated dyes. The capacity of the naphthalocyanines to generate singlet oxygen is comparable to that of the corresponding phthalocyanines. However, in contrast to the phthalocyanine dyes, the sulfonated aluminum naphthalocyanines show very little phototoxicity towards the V‐79 cells, suggesting close association with non‐vital cell constituents or extensive formation of photoinactive adducts and aggregates.
THE PHOTOKILLING OF BLADDER CARCINOMA CELLS in vitro BY PHENOTHIAZINE DYES
Authors: Fowler G. J. S. , Rees R. C. , Devonshire R.
Published: January 2008

Abstract— The potential photodynamic therapy photosensitizers Methylene Blue, Azure C, Methylene Violet, Thionine, Methylene Green, Haematoporphyrin, Nile Blue A, chloroaluminium phthalocyanine and bis‐aluminium phthalocyanine were examined for their photoeffects and dark toxicity against a human superficial bladder carcinoma cell‐line. By examination of [3H]thymidine uptake into dye‐treated cells after irradiation with a copper‐vapour pumped dye laser, it was found that Methylene Blue was the most phototoxic and dark toxic of all the dyes tested, suggesting that the dye might be of some use as a topically applied photodrug for use in photodynamic therapy of superficial or early‐recurring carcinomas.
PHOTOBIOLOGICAL ACTIVITY OF 3,4'‐DIMETHYL‐8‐METHOXYPSORALEN, A LINEAR FUROCOUMARIN WITH UNUSUAL DNA‐BINDING PROPERTIES
Authors: Palumbo M. , Baccichetti F. , Antonello C. , Gia O. , Capozzi A. , Magno S. Marciani
Published: January 2008

Abstract— The furocoumarin derivative 3,4'‐dimethyl‐8‐methoxypsoralen (DMe‐8‐MOP) exhibits remarkable antiproliferative activity, but is devoid of skin phototoxicity. To gain insight into this peculiar behaviour we investigated non‐covalent and covalent binding of DMe‐8‐MOP to calf thymus DNA, along with DNA‐synthesis inhibition and mutagenic activity. The non‐covalent interaction of DMe‐8‐MOP with the nucleic acid is quite poor as shown by equilibrium dialysis, spectroscopic, chiroptical and hydrodynamic techniques. However, it exhibits relevant photobinding ability to DNA using both isolated nucleic acid samples and cellular systems. Unlike the large majority of congeners, DMe‐8‐MOP undergoes predominantly photochemical monoaddition to the double helical polynucleotide. Upon examination of the products obtained by enzymatic hydrolysis of DMe‐8‐MOP photomodified DNA. the formation of an unusual furan side adduct is proposed, which could account for the peculiar photochemical and photobiological properties of the 3,4'‐dimethyl furocoumarin derivative.
HYPOCRELLINS and THEIR USE IN PHOTOSENSITIZATION*
Authors: Zhenjun Diwu , Lown J. William
Published: January 2008

Abstract— Hypocrellins A and B are pigments which are isolated from parasitic fungi Hypocrella bambuase (B. et Br) sacc. and Shiraia bambusicola P. Heen found in the People's Republic of China (P.R.C.) and Sri Lanka respectively. These agents, which belong to the general class of perylene quinonoid pigments, have a long history as traditional medicinal agents especially in the P.R.C. Recently their marked photosensitizing properties have been established and exploratory studies initiated. This effort has led to the realization of the potential of the hypocrellins for the photodynamic therapy of tumors. The review summarizes the chemical and photophysical properties of the hypocrellins and their derivatives as well as studies on photosensitization to date at the molecular, cellular and in vivo levels, and their prospects as PDT agents.
OXYGEN MEDIATED PHOTOSYSTEM I ACTIVITY IN THYLAKOID MEMBRANES MONITORED BY A PHOTOELECTROCHEMICAL CELL
Authors: Goetze D. Christopher , Carpentier Robert
Published: January 2008

Abstract— A photoelectrochemical cell has been used to monitor the effects of three enzymes on the photocurrent produced by isolated spinach thylakoids. The enzymes were glucose oxidase, superoxide dismutase and catalase. It is shown that all three inhibit the photocurrent to varying degrees. The results demonstrate that electron transport to the working electrode is mediated by oxygen. Further, the activity monitored originated from photosystem I with oxygen as the acceptor and photosystem II/plastoquinone as the donor. Thus, the photoelectrochemical cell constitutes a potential new approach for the monitoring of pseudocyclic electron transport.
THE PHOTOTRANSFORMATION PATHWAY OF DIMERIC OAT PHYTOCHROME FROM THE RED‐LIGHT‐ABSORBING FORM TO THE FAR‐RED‐LIGHT‐ABSORBING FORM AT PHYSIOLOGICAL TEMPERATURE IS COMPOSED OF FOUR INTERMEDIATES
Authors: Inoue Yasunori , Rüdiger Wolfhart , Grimm Rudolf , Furuya Masaki
Published: January 2008

Abstract— –Phototransformation of oat type I phytochrome in vitro from the red‐light‐absorbing form (Pr) to the far‐red‐light‐absorbing form (Pfr) at physiological temperature (24°C) was investigated with a multichannel transient spectrum analyser. Four sequential intermediates were detected between Pr and Pfr. Absorption spectra of these intermediates suggested that three of them corresponded with the intermediates lumi‐R, meta‐Ra and meta‐Rc detected earlier at low temperature spectroscopy. A new intermediate named meta‐Rb was found in the pathway between meta‐Ra and meta‐Rc. The new intermediate is not identical with meta‐Rb previously detected at low temperature. The rate constant of Pfr appearance in isolated oat phytochrome dissolved in buffer containing 5% (vol/vol) glycerol was similar to that of etiolated pea epicotyl tissue.
SOME COMPONENTS OF THE TUMOR‐LOCALIZING FRACTION OF HEMATOPORPHYRIN DERIVATIVE
Authors: Ho Yau‐Kwan , Pandey Ravindra K. , Missert Joseph R. , Dougherty Thomas J.
Published: January 2008

Abstract— –In continuation of the effort to delineate the structure of Photofrin, a chromatographically well separated component of the tumor‐localizing fraction was isolated and purified using a combination of gel filtration chromatography and semi‐preparative high‐performance liquid chromatography. This component, the least hydrophobic of the tumor‐localizing fraction, was deemed to be dihematoporphy‐rin ether, based on mass spectrometric analysis and its behavior toward base hydrolysis and lithium aluminum hydride reduction. Although less potent than Photofrin, the purified component was an active photosensitizer.
PHOTOCHEMISTRY OF 1,2,3‐INDANETRIONE*
Authors: Netto‐Ferreira J. C. , Scaiano J. C.
Published: January 2008

The photochemistry of 1,2,3‐indanetrione (1) has been examined in solution at room temperature by steady state and laser flash photolysis. The triplet state of 1 (T = 6.5 μs, δmux, = 360 and 570 nm, in dry acetonitrile) reacts preferentially via an a‐cleavage process followed by a considerably slower loss of carbon monoxide. Triplet 1 shows a remarkably fast hydrogen abstraction rate constant when in the presence of 1,4‐cyclohexadiene (kr= 1.4 times 106M−1s−1) in spite of its low excitation energy (ET= 42 kcal/mol). This behavior can be explained by assuming that the vicinal carbonyls coplanar to the ketyl radical play an important role in its stabilization.
FORMATION OF OXONIACHLORINS ON PHOTOOXIDATION OF 20‐TRIFLUOROACETOXY‐ AND 20‐CHLORO‐CHLOROPHYLL DERIVATIVES*
Authors: Iturraspe Jose , Gossauer Albert
Published: January 2008

Zinc complexes of both 20‐trifiuoroacetoxy‐ and 20‐chloro‐pheophorbide‐a methyl ester yield the same isolable 20‐oxonia‐pheophorbide (2b) on irradiation with visible light in methylene chloride for 90 and 10 min, respectively. In the case of the 20‐chloro derivative, the yield amounts to40–50% along with 30% of starting material. Zinc complexes of 20‐trifluoroacetyl‐ and 20‐chloro‐pyropheophorbide‐a methyl ester behave likewise. In aqueous solution, the expected dihydro‐biliverdin derivatives 2 are obtained among other products, some of them display a strong red fluorescence. In the presence of nucleophiles the oxoniachlorin macrocycle is readily cleaved, yielding the corresponding linear tetrapyrroles. Particularly, reaction with cyanide ions leads to biline derivatives, which could serve as intermediates for the synthesis of natural occurring luciferins from bioluminescent plankton. The possible role of some of the above mentioned reactions in connection with chlorophyll catabolism is discussed.
CARBOXYLATED ZINC‐PHTHALOCYANINE, INFLUENCE OF DIMERIZATION ON THE SPECTROSCOPIC PROPERTIES. AN ABSORPTION, EMISSION, AND THERMAL LENSING STUDY
Authors: NEGRI R. MARTíN , ZALTS ANITA , SAN ROMáN ENRIQUE A. , ARAMENDíA PEDRO F. , BRASLAVSKY SILVIA E.
Published: January 2008

Abstract—

Monomer and dimer absorption and emission spectra, and dimerization constants are reported for the diamide of the zinc‐tetracarboxyphthalocyanine in pure dimethylformamide (DMF) and in H2O/DMF mixtures at room temperature. The dimerization constant increases steadily with the water content. The monomer absorption Q‐band is insensitive to the solvent composition, whereas dimer spectra show great variations with the water content. Stationary emission measurements show that fluorescence originates exclusively from the monomers. The fluorescence spectrum as well as its absolute fluorescence quantum yield, measured by steady‐state thermal lensing, are also insensitive to the solvent composition. The thermal lensing method is discussed for the case of two absorbing species in equilibrium.
MITOTIC INHIBITION BY PHENYLPORPHINES AND TETRASULFONATED ALUMINIUM PHTHALOCYANINE IN COMBINATION WITH LIGHT
Authors: Berg Kristian , Moan Johan
Published: January 2008

Abstract—

This work relates to studies on modes of phototoxicity by tetrasulfonated aluminium phthalocyanine (AIPcS4), tetrahydroxy‐ and monosulfonated meso‐tetraphenylporphines (3‐T‐HPP and TPPS,) on culture cells. Toxicity at moderate light exposures appears to be related to inhibition of microtubule function. Treatment of human cervix carcinoma cells of the line NHIK 3025 incubated for 18 h with the sensitizers and exposed to light inhibits multiplication for the first hours after light exposure, a significant fraction of the cells accumulating in mitosis. For the first hours after treatment, the mitotic cells were always mainly found in metaphase; generally seen as c‐metaphases and three‐group metaphases. During this time, anaphase and telophase cells were absent or greatly reduced in number. Indirect immunofluorescence staining of P‐tubulin showed that the spindle apparatus of mitotic cells was perturbed in all cases.

The accumulation in mitosis was more extensive after treatment with AIPcS4 and light than after treatment with 3‐T‐HPP or TPPS1 and light. This may be related to the great difference in the lipophilic properties of these sensitizers; i.e. AIPcS4 being highly water soluble while TPPS, and 3‐T‐HPP are lipophilic sensitizers. The lipophilicity of several sensitizers has been measured by two different methods, the partition between an aqueous and a lipophilic phase (Triton X‐114) and the binding strength to a reverse phase column. The results show that the measured relative lipophilicity of the sensitizers may be influenced by the method of analysis.
ACTION SPECTRUM FOR ENHANCEMENT OF PHOTOTROPISM BY Arabidopsis thaliana SEEDLINGS
Authors: Janoudi Abdul‐Kader , Poff Kfnneth L.
Published: January 2008

Abstract—

Fluence‐response relationships have been measured at wavelengths from 350 to 760 nm for the enhancement of phototropism in Arabidopsis thulium L. (Heynh) strain “Estland” by an irradiation at each of these wavelengths, given 2 h prior to a 450 nm inductive unilateral irradiation. Action spectra have been constructed from these fluence‐response relationships based on: (i) the fluence required to obtain a curvature of 25° (corresponding to an enhancement of 15°), (ii) the fluence required to obtain 50% of the maximum enhancement and (iii) the fluence threshold for enhancement by a pre‐irradiation. The action spectra exhibit two maxima, one at 669 nm and a second at 378 nm. The height of the maximum at 669 nm is approximately 4 times the height of the maximum at 378 nm. Based on the action spectra, it is concluded that the enhancement of phototropism in A. thaliana is mediated by phytochrome.
DETECTION AND PARTIAL SEQUENCE OF PHYTOCHROME GENES IN THE FERNS Anemia phyllitidis (L.)Sw (SCHIZAEACEAE) AND Dryopteris filix‐mas L. (POLYPODIACEAE) BY USING POLYMERASE‐CHAIN REACTION TECHNOLOGY*
Authors: Maucher Helmut P. , Scheuerlein Robert , Schraudolf Helmut
Published: January 2008

Abstract—

Phytochrome controls several developmental steps during formation and differentiation of the fern gametophyte, including spore germination, morphogenesis of the gametophyte or differentiation of the sexual cells. To obtain information about the amino acid sequence and the regulation of phytochrome expression at the gene level, two degenerated oligonucleotides against well conserved amino acid regions were designed after an optimal alignment of the known phytochrome sequences. These primers were tested against DNA isolated from Arabidopsis thaliana, and the polymerase‐chain reaction (PCR) products were cloned and sequenced. The DNA fragment produced with this method proved to be identical with a phytochrome‐A‐gene fragment from A. thaliana, and hence this fragment was used in further experiments to prove whether amplified DNA from fern species contains phytochrome‐like DNA. With this procedure we successfully detected and cloned gene fragments both from gametophytes of Anemia phyllitidis and Dryopteris filix‐mas, cultured for 7 days under vegetative conditions. In addition, poly(A)+ RNA was prepared from 7‐day‐old gametophytes of A. phyllitidis, induced to differentiate antheridia under generative conditions. This poly(A)+ RNA was transcribed into complementary DNA and used together with both phytochrome specific primers in a PCR experiment. We thereby obtained another DNA fragment. These data strongly suggest that A. phyllitidis has at least two phytochrome genes, and that at least one of them is expressed in light‐grown gametophytes.
FORTY YEARS OF BLUE‐LIGHT RESEARCH AND NO ANNIVERSARY
Authors: Galland Paul
Published: January 2008

Abstract—

The status of near‐ UV/blue‐light research is described and critically assessed. It is argued that the generally accepted proposition of flavins acting as near‐ UV/blue‐light photoreceptors is reasonable, but that also other pigments, specifically pteridines and pterins, should be considered. In view of the fact that a receptor assay, applicable to any organism and near‐UV/blue‐light reaction, is not yet at hand, caution appears to be indicated as to what one can accept as a reasonable “criterion” for the involvement of any proposed photoreceptor pigment.
NEW PHTHALOCYANINE PHOTOSENSITIZERS FOR PHOTODYNAMIC THERAPY
Authors: Oleinick Nancy L. , Antunez Antonio R. , Clay Marian E. , Rihter Boris D. , Kenney Malcolm E.
Published: January 2008

Six new aluminum and silicon phthalocyanines have been synthesized and their photocytotoxicity toward V79 cells has been studied. The compounds that have been prepared are: AIPcOSi(CH3)2(CH2),N(CH3)2, I; AIPcOSi(CH3)2(CH2)3N(CH3)3+I−, II; CH3SiPcOSi(CH3)2(CH2)3N(CH3)2, III; HOSiPcOSi(CH3)2(CH2)3N(CH3)2, IV; HOSiPcOSi(CH3)2(CH2)3)3(CH3)3+I−, V; and SiPc[OSi(CH3)2(CH2)3N(CH3)3+I−]2, VI. Relative growth delay values for compounds I‐VI and relative cytotoxicity values for compounds I, II, IV, V and VI have been determined. Compounds I and II have been shown to be comparable in photocytotoxicity to what is presumed to be AIPcOH.xH2O, and compound IV has been shown to have greater activity. The classes of compounds to which these six compounds belong appear to have potential for photodynamic therapy.
THE PHOTOPHYSICAL PROBE, 7‐AZATRYPTOPHAN, IN SYNTHETIC PEPTIDES
Authors: Rich K. L. , Négrerie M. , Li J. , Elliott S. , Thornburg R. W. , Petrich J. W.
Published: January 2008

7‐Azatryptophan is proposed as an alternative to tryptophan as a photophysical probe in the study of protein structure and dynamics. Not only are the spectral characteristics of 7‐azatryptophan easily distinguishable from those of tryptophan, but this nonnatural amino acid is shown to be amenablc to incorporation into peptides. We present the first synthesis and purification of a synthetic peptide containing 7‐azatryptophan, NAc‐Pro‐7‐azatryptophan‐Asn‐NH2, which is shown to be a competitive inhibitor of α‐chymotrysin.
SITES OF PHOTODAMAGE BY THE IMINIUM SALT OF A COPPER OCTAETHYLBENZOCHLORIN
Authors: Kessel David
Published: January 2008

Because the benzochlorin derivative copper (11) α‐meso‐N,N′‐dimethyloctaethylbenzochlorin iminium chloride (CDSI) is not fluorescent, sites of drug localization in L1210 cells were detected by indirect methods involving using a series of fluorescent probes. The CDS1‐mediated cytotoxicity was associated with mitochondrial damage, a decreased membrane potential and an increase in the heterogeneity of membrane sites of binding of a polar analog of diphenylhexatriene. Although CDS l is a cationic compound, its accumulation was not impaired in a cell line exhibiting the multidrug resistance phenotype.
THE PHOTOCHEMISTRY OF ADENOSINE: INTERMEDIATES CONTRIBUTING TO ITS PHOTODEGRADATION MECHANISM IN AQUEOUS SOLUTION AT 298 K AND CHARACTERIZATION OF THE MAJOR PRODUCT
Authors: Arce Rafael , Marínez Lydia , Danielsen Edgard
Published: January 2008

Abstract— The steady‐state (254 nm) photolysis of 9–(β‐d‐erythropentofuranosyl)adenine (adenosine) in aqueous solution was studied. Photodestruction yields on the order of 1.3 × 10−3) were determined at room temperature by measuring the initial decrease in the absorption maximum as a function of irradiation time. The use of high performance liquid chromatography (HPLC) permitted a more exact determination of the yield (2.5 × 103). The formation of photoproducts was also studied using HPLC. In the photolysis of 50 μM aqueous solutions of adenosine under anaerobic conditions at least 11 stable photoproducts are formed that absorb at 260 nm, the wavelength of maximum absorption of adenosine. The major photoproduct was also isolated and characterized as adenine; its formation yield was determined to be 4.5 × 104. This yield is affected by the presence of oxygen and by the initial concentration of adenosine employed. Fluorescence emission and excitation spectra were used to monitor the formation of highly fluorescent photoproducts that emit with maxima at365, 398, and 430 nm and absorb in the wavelength region of 240–380 nm.

The reactive species in the photodestruction mechanism were established using substrates that react selectively with the respective short‐lived species. Photoionization is a primary photoprocess implied by these studies. The triplet state of adenosine also contributes to the photodestruction mechanism.
THE CONFORMATIONAL ANALYSIS AND PHOTOISOMERIZATION OF RETINOCHROME ANALOGS WITH POLYENALS
Authors: Kinumi Tomoya , Tsujimoto Kazuo , Ohashi Mamoru , Hara Reiko , Hara Tomiyuki , Ozaki Koichi , Saka Miho , Katsuta Yuko , Wada Akimori , Ito Masayoshi
Published: January 2008

Abstract— 3, 7‐Dimethyl‐2, 4, 6, 8, 10‐dodecapentaenal was synthesized for reconstitution of the retinochrome analog. Its opsin shift was 1000 cm 1 smaller than that of native retinochrome, whose chromophore contains the same number of double bonds. The conformational change from 6‐s‐trans to 6‐s‐cis, as figured in a retinal molecule, plays an important role in the formation of the retinochrome analog, based on the estimation of opsin shifts for retinal analogs locked in the 6‐s conformation. Thus the conformation of the 6–7 single bond in the native retinochrome was suggested to be 6 ‐cis. Analysis of the circular dichroic spectra of retinochrome analogs revealed that the 6‐s conformation is independent of the appearance of the β‐band. The stereoselectivity in the photoisomerization of the retinal analogs by a retinochrome template depends on the hydrophobic binding in the region of the β‐ionone ring.
PHOTODYNAMIC THERAPY OF B16 PIGMENTED MELANOMA WITH LIPOSOME‐DELIVERED Si(IV)‐NAPHTHALOCYANINE
Authors: Biolo Roberta , Jori Giulio , Soncin Marina , Pratesi Riccardo , Vanni Umberto , Rihter Boris , Kenney Malcom E. , Rodgers Michael A. J.
Published: January 2008

The possibility of extending photodynamic therapy to the treatment of highly pigmented neoplastic lesions was tested by using Si(IV)‐naphthalocyanine (SiNc) as a tumor‐localizing agent. Si(IV)‐naphthalocyanine displays intense absorbance at 776 nm (ɛ= 5 × 105 M−1 cm−1), where melanin absorption becomes weaker. As an experimental model we selected B16 pigmented melanoma subcutaneously transplanted to C57BL mice. Upon injection of 0.5 or 1 mg kg−1 of liposome‐incorporated SiNc, maximal accumulation of the photosensitizer in the tumor was observed at 24 h with recoveries of 0.35 and 0.57 μg g−1, respectively. However, the tumor targeting by SiNc shows essentially no selectivity, since the photosensitizer concentrations in the skin (peritumoral tissue) were very similar to those found in the tumor at all postinjection times examined by us. Irradiation of SiNc‐loaded melanoma with 776 nm light from a diode laser at 24 h postinjection induces tumor necrosis and delay of tumor growth. The effect appears to be of purely photochemical nature at dose rates up to 260 mW cm−2; at higher dose rates, thermal effects are likely to become important.
THE Arabidopsis PHYTOCHROME A GENE HAS MULTIPLE TRANSCRIPTION START SITES AND A PROMOTER SEQUENCE MOTIF HOMOLOGOUS TO THE REPRESSOR ELEMENT OF MONOCOT PHYTOCHROME A GENES
Authors: Dehesh Katayoon , Franci Chris , Sharrock Robert A. , Somers David E. , Welsch Jo Anne , Quail Peter H.
Published: January 2008

We have determined the sequence of the phytochrome A gene (PHYA) and its flanking DNA from Arabidopsis thaliana and have identified transcription start sites for three nested transcripts of increasing length. The overall structure of the gene is similar as regards exon/intron organization to other angiosperm PHY genes characterized. The triple transcription start site arrangement is similar to that of pea PHYA but different from the single start site of oat, rice and maize PHYA genes, indicating a possible monocot‐dicot difference. Comparison of the Arabidopsis PHYA promoter sequence with others available indicates that both pea and Arabidopsis promoters contain a DNA element with a core sequence motif identical to one conserved in all existing monocot PHYA sequences and denned by functional assay in the oat PHYA gene as repressor element, RE1, responsible for negative light regulation.
BENZOPHENONE PHOTOSENSITIZATION OF 2′‐DEOXYGUANOSINE: CHARACTERIZATION OF THE 2R AND 2s DIASTEREOISOMERS OF 1‐(2‐DEOXY‐β‐D‐erythoW‐PENTOFURANOSYL)‐2‐METHOXY‐4,5‐IMIDAZOLIDINEDIONE. A MODEL SYSTEM FOR THE INVESTIGATION OF PHOTOSENSITIZED FORMATION OF DNA‐PROTEIN CROSSLINKS
Authors: Morin Benedicte , Cadet Jean
Published: January 2008

Abstract Benzophenone‐mediated photosensitization of 2′‐deoxyguanosine and its 3′,5′‐di‐O‐acetyl derivative, used as DNA model compounds, in oxygen‐saturated water‐methanol (1:1) solution results in the nucleophilic addition of methanol to the guanine base. The resulting modified nucleosides have been isolated by reverse‐phase high‐performance liquid chromatography and characterized by extensive spectroscopic measurements including 13C and IH nuclear magnetic resonance, fast atom bombardment mass spectrometry and circular dichroism as the 2R and 2s diastereoisomers of 1‐(2‐deoxy‐˜‐o‐erythro‐pentofuranosyl)‐2‐methoxy‐4,5‐imidazolinedione and their related 3′,5′‐di‐O‐acetyl derivates. Information concerning the absolute configuration of the two pairs of diastereoisomers was inferred from detailed nuclear Overhauser effect experiments. A reaction mechanism, involving guanine radical intermediates, is proposed to explain the generation of these new guanine photoproducts.
TIME‐RESOLVED PHOTOACOUSTIC CALORIMETRY OF TRYPTOPHAN IN WATER and ORGANIC SOLVENTS
Authors: Brancaleon L. , Crippa P. R. , Minari C.
Published: January 2008

Abstract –Very little has been done in the direct study of nonradiative decays of Trp, indole and derivatives, in spite of their relatively low fluorescence quantum yields. Time‐resolved photoacoustic calorimetry is an ideal technique for this kind of study: it is very sensitive in the detection of small amounts of heat released and, in principle, allows a broad band of temporal resolution. The photoacoustic apparatus used for our measurements offers a temporal window between 10 ns and 10 μs. The analysis of the waveforms, based on a particular deconvolution method, simultaneously gives the fraction of energy released and the associated lifetime. In a broad sense, time‐resolved photoacoustic spectroscopy can be seen as a complementary method to traditional radiative techniques such as static, time‐resolved fluorescence and flash photolysis. The present work presents studies of Trp in different solvents in order to acquire new information about the interaction of this chromophore with solvents. From our measurements the high sensitivity of Trp to solvents is confirmed. The formation of complexes is evident at the excited state (exciplexes), between the chromophore and one or more molecules of solvent. These exciplexes are characterized by having an energy different from that of the singlet and triplet of Trp. Moreover, photoacoustic measurements detect, in water, the presence of another electronic state, which seems to have characteristics similar to a triplet‐like state reported in other work.
ASSESSMENT OF GENOTOXICITY AND MUTAGENICITY OF 1,2‐DIOXETANES IN HUMAN CELLS USING A PLASMID SHUTTLE VECTOR
Authors: Emmert Steffen , Epe Bernd , Saha‐Möller Chantu R. , Adam Waldemar , Rünger Thomas M.
Published: January 2008

Abstract— 1,2‐Dioxetanes are efficient sources of triplet excited carbonyl compounds on thermal decomposition. They cause photochemical and photobiological transformations in the dark. In order to study the genotoxicity and mutagenicity of 1,2‐dioxetanes, the replicating shuttle vector pZ189 was damaged with 3,3,4‐trimethyl‐l,2‐dioxetane(TrMD) or 3‐hydroxymethyl‐3,4,4‐trimethyl‐l,2‐dioxetane (HTMD) in vitro and subsequently transfected into normal human lymphoblasts. We found a dose‐dependent increase of genotoxicity (decrease of plasmid survival) and increase of mutation frequency with both dioxetanes. However, TrMD was less mutagenic than HTMD at similar genotoxicity. Sequence analysis of the supF gene revealed more point mutations than deletions. Single base substitutions occurred exclusively at G:C sites: 94.6% of point mutations with TrMD and 100% with HTMD were G:C to T:A and G:C to C:G transversions. These are the typical mutations following 7,8‐dihydro‐8‐oxoguanine (8‐oxo‐G) formation, the main DNA lesion induced by TrMD and HTMD. Only with TrMD we found 5.4% G:C to A:T transitions, probably reflecting the more pronounced ability of TrMD to form some pyrimidine dimers. Our results indicate that 8‐oxo‐G is also the most relevant modification in in vivo mutagenesis.
KINETIC CHARACTERIZATION OF THE REDOX COMPONENTS IN SOLUBILIZED MEMBRANES FROM PORCINE NEUTROPHILS: REDUCTION WITH DITHIONITE AND PHOTOEXCITED NAD(P)H
Authors: Orii Yutaka , Miki Toshiaki , Kakinuma Katsuko
Published: January 2008

Abstract— Cytochrome b558 in solubilized membranes prepared from porcine neutrophils was reduced by dithionite with a second‐order rate constant of 2.5 times 106 M‐1 s‐1 at pH 7.4 and 20°C accompanied by spectral changes with peaks at 428 nm and 560 nm and isosbestic points at 420 and 441 nm. When an anaerobic mixture of solubilized membranes and NAD(P)H was exposed to a white light, cytochrome b558 was reduced biphasically but with almost the same spectral profiles as in the dithionite reduction. Thus, participation of redox component(s) of unknown nature in the photochemical reduction was suggested.

The NAD(P)‐ radical generated by photoexcitation of NAD(P)H with a 355 nm laser pulse under anaerobic conditions also reduced cytochrome b558 with a high rate constant of 4.3 times 108M‐1 s‐1 at pH 7.4 and 20°C. The reduction of cytochrome b558 accompanied a simultaneous reduction of a component having an absorption band around 420 nm, suggesting participation of an iron‐sulfur (Fe‐S) cluster. The cytochrome b558 reduction was followed by its reoxidation by another component with an apparent second‐order rate constant of 6.5 times 105M‐1 s‐1. During the reoxidation, the Fe‐S‐like component remained in the reduced state, and thus its role other than as electron mediator in neutrophils NADPH oxidase is suggested. Not only the rate constant but also the extent of cytochrome b558 reoxidation decreased as the same reaction mixture was exposed to the laser pulse repeatedly. This result clearly indicates that an electron accumulates in this electron‐accepting component designated tentatively as the ω component.
THE USE OF LIPID HEADGROUP CHARGE TO ENHANCE PHOTOINDUCED ELECTRON TRANSFER IN VESICLES: REACTIONS OF FUNCTIONALIZED PYRENE WITH A TWO COMPONENT VIOLOGEN SYSTEM
Authors: Li L. , Patterson L. K.
Published: January 2008

Abstract—

Kinetics of photoinduced electron transfer from a lipid functionalized pyrene, 1‐(10‐(6(8)‐octadecylpyrenyl)decanoyl)‐2‐hexanoyl‐.sn‐glycero‐3‐phosphorylcholine (OPyPC), to a two component viologen acceptor system have been measured by laser flash photolysis. N, N'‐tetramethylene‐2,2'‐bi‐pyridinium ion (DQ2+) and N, N'‐dipropyl‐4,4'‐bipyridinium sulfonate (PVS), have been utilized as the primary and secondary acceptors. It has been shown that utilization of a lipid with a net negatively charged phosphatidylglycerol headgroup provides a driving force for localizing high concentrations of primary acceptor (DQ2+) in the region of donor. Subsequently, the charged interface can act to maintain long‐term separation between the oxidized pyrene donor (OPyPC+) and the reduced secondary acceptor, PVS‐. When a dioleoyl lipid is used, reaction of (OPyPC+) with the double bond competes significantly with back reaction. However, substitution of diphytylphosphatidylglycerol for the dioleoyl analog results in a cation lifetime of about 0.5 ms and a continued very long‐lived reduced species (˜4 h). Quantum yields of ˜0.15 may be obtained in this system.
Triplet State Energy Transfer Between the Primary Donor and the Carotenoid in Rhodobacter sphaeroides R‐26.1 Reaction Centers Exchanged with Modified Bacteriochlorophyll Pigments and Reconstituted with Spheroidene
Authors: Frank Harry A. , Chynwat Veeradej , Posteraro Anthony , Hartwich Gerhard , Simonin Ingrid , Scheer Hugo
Published: January 2008

Abstract— The dynamics of triplet energy transfer between the primary donor and the carotenoid were measured on several photosynthetic bacterial reaction center preparations from Rhodobacter sphaeroides: (a) wild‐type strain 2.4.1, (b) strain R‐26.1, (c) strain R‐26.1 exchanged with 132‐hy‐droxy‐[Zn]‐bacteriochlorophyll at the accessory bacteriochlorophyll (BChl) sites and reconstituted with spheroidene and (d) strain R‐26.1 exchanged with P‐vinyl]‐132‐hydroxy‐bacteriochlorophyll at the accessory BChl sites and reconstituted with spheroidene. The rise and decay times of the primary donor and carotenoid triplet‐triplet absorption signals were monitored in the visible wavelength region between 538 and 555 run as a function of temperature from 4 to 300 K. For the samples containing carotenoids, all of the decay times correspond well to the previously observed times for spheroidene (5 ± 2 us). The rise times of the carotenoid triplets were found in all cases to be biexponen‐tial and comprised of a strongly temperature‐dependent component and a temperature‐independent component. From a comparison of the behavior of the carotenoid‐con‐taining samples with that from the reaction center of the carotenoidless mutant Rb. sphaeroides R‐26.1, the temperature‐independent component has been assigned to the buildup of the primary donor triplet state resulting from charge recombination in the reaction center. Arrhenius plots of the buildup of the carotenoid triplet states were used to determine the activation energies for triplet energy transfer from the primary donor to the carotenoid. A model for the process of triplet energy transfer that is consistent with the data suggests that the activation barrier is strongly dependent on the triplet state energy of the accessory BChl pigment, BChlB.
Indications for the Occurrence of Nitric Oxide Synthases in Fungi and Plants and the Involvement in Photoconidiation of Neurospora crassa*
Authors: Ninnemann Helga , Maier Josef
Published: January 2008

Indications for the occurrence of nitric oxide synthases in Dictyostelium, Neurospora, Phycomyces and the leguminous plant Mucuna hassjoo as well as a physiological role of nitric oxide in Neurospora crassa are demonstrated. An exogenous nitric oxide donor, sodium nitroprus‐side, inhibited light‐stimulated conidiation in N. crassa. Specific inhibitors of nitric oxide synthase, like the arginine derivatives NG‐nitro‐L‐arginine (L‐NA) and NG‐nitro‐L‐arginine‐methyl ester (L‐NAME), enhanced conidiation in darkness and in the light, whereas the stereo‐isomer D‐NAME was inactive. This communication reports to our knowledge the first time the presence of enzymatic activity of nitric oxide synthase in fungi and a higher plant and an effect of nitric oxide in fungal photophysiology.
Spectroscopic Study of New Fluorescent Probes
Authors: Sández M. I. , Suárez A. , Rios M. A. , Balo M. C. , Fernández F. , López Carmen
Published: January 2008

Abstract— Various newly synthesized substances containing the same chromophore as PRODAN were subjected to a spectroscopic study. The new substances, ω‐[6‐(N‐meth‐yl‐N‐alkylamino)naphthoyl]alcanoic acids (MANA), possess polar groups and alkyl chains of variable length that make them potentially useful as fluorescent probes in membrane studies. This paper reports on their spectroscopic properties in various pure solvents. Their Stokes shifts are given and related to different physicochemical properties of the solvents. A theoretical study of the behavior of the new substances is also presented.
Hydrogen‐Bonding Interactions between Harmane and Pyridine in the Ground and Lowest Excited Singlet States
Authors: Balón Manuel , Muñoz María A. , Guardado Pilar , Carmona Carmen
Published: January 2008

Abstract— A spectroscopic (UV‐visible, Fourier transform IR, steady‐state and time‐resolved fluorescence) study of hydrogen‐bonding interactions between harmane (1‐meth‐yl‐9H‐pyrido/3,4‐b/indole) and pyridine in the ground and lowest excited singlet state is reported. In low polar and weakly or nonhydrogen‐bonding solvents, such as cy‐clohexane, chloroform, carbon tetrachloride, toluene and benzene, the analysis of the spectroscopic data indicates that harmane and pyridine form 1:1 stoichiometric hydrogen‐bonded complexes in both the ground and singlet excited states. The formation constants of the complexes are greater in the excited than in the ground state. Hydrogen‐bonding interaction in the excited state is essential for the quenching of the fluorescence of harmane by pyridine. The stabilities of the hydrogen‐bonded complexes between harmane and pyridine diminish as the polarity and hydrogen‐bonding ability of the solvent increase.
Cytolytic Response to HIV in Patients with HIV Disease Treated with Extracorporeal Photochemotherapy: Preliminary Study
Authors: Gonzalez Joselyn , Berger Carole , Cottrill Carolyn M. , Geller Alex , Schwartz Joseph , Palangio Mark , Klainer Albert S. , Bisaccia Emil
Published: January 2008

Extracorporeal photochemotherapy (photopheresis), an immunomodulatory therapy that targets circulating T helper lymphocytes, has been applied to the management of human immunodeficiency virus (HIV) disease. Any therapy that exerts its actions on CD4+ T cells has the potential of exacerbating HIV infection. Therefore, it was necessary to observe immune function during treatment. Because cytotoxic T lymphocytes (CTL) and natural killer cells are thought to play an important role in the response against HIV infection, we examined the effect of photopheresis on HIV cytolytic activity. The study group consisted of seven patients with late‐stage HIV disease who had not received any previous treatment for HIV infection. Patients were treated exclusively with photopheresis on two consecutive days each month for 14–32 months (average, 25 months). Peripheral lymphocytes, collected at various points during treatment, were used as effectors in a Wr release assay. Epstein‐Barr virus (EBV)‐transformed autologous B cell lines transfected with recombinant vaccinia vectors that expressed the HIV env (gp120, gp41) and gag (p24) proteins were used as target cells. All seven patients demonstrated relatively constant levels of cytolysis (>10% above controls) during treatment in the context of stable CD4+ T cell counts and a stable clinical status. These results suggest that extracorporeal photochemotherapy did not impair the cytolytic response to HIV infection and may have enhanced it in some patients.
Aggregation of Chlorophyll a′ in Aqueous Methanol
Authors: Oba Toru , Watanabe Tadashi , Mimuro Mamoru , Kobayashi Masami , Yoshida Shoichiro
Published: January 2008

An aggregate of chlorophyll a′ (Chi a′, C132‐epimer of ChI a) formed in a methanovwater (40160, vol/vol) mixed solvent was examined by visible absorption, circular dichro‐ism (CD), fluorescence and resonance Raman spectrosco‐pies in relation to its possible involvement in the core of photosystem I reaction center. The Chl a′ aggregate exhibited a sharp, double‐peaked absorption spectrum (690 and 715 nm) accompanied by an intense, conservative CD signal. The fluorescence excitation polarization spectrum showed that the doublet results from the exciton splitting in a single aggregate species. Time‐dependent changes in the spectroscopic properties clearly point to a simple transformation process from one molecular species to another, though a minor component appears to coexist. This conclusion was supported also by the principal multicom‐ponent spectral estimation analysis of the transients of absorption spectra. The species formed at the initial stage is most probably a T‐shaped dimer or oligomer, which is then gradually converted into the final major product, presumably a stacked dimer. In both of these states, the Chl molecules are linked together via direct coordination of the C13’keto carbonyl oxygen onto the Mg atom of neighboring molecules, as suggested by almost identical resonance Raman spectra in ordinary and deuterated methanovwater mixed solvents. The stacked dimers probably further associate to form a colloidal state in this solvent system. Based on these results, a model for the Chl a′ aggregation is proposed.
Mutants of Arabidopsis as Tools to Understand the Regulation of Phenylpropanoid Pathway and UVB Protection Mechanisms
Authors: Bharti Arvind K. , Khurana Jitendra P.
Published: January 2008

Abstract— Plants accumulate certain phenylpropanoid compounds in the vacuoles of their epidermal and subepidermal cell layers thereby protecting the underlying tissue against UVB‐induced damage. However, a number of mutants of Arabidopsis thaliana are known that fail to synthesize these protective pigments, thereby allowing harmful UVB radiation to penetrate into their dermal layers. Study of several of these nonlethal mutants, defective in various aspects of flavonoid and lignin biosynthesis, has led to a better understanding of the coordinate regulation and expression of important genes as well as of mechanisms involved in plant defense against UVB radiation. The characteristics of the various phenylpropanoid mutants of Arabidopsis, viz. flavonoid mutants (banyuls [baity, increased chalcone synthase expression 1 [icx1]; transparent testa [tt] and ultraviolet sensitive [uvs]) and hydroxycinnamic acid ester mutants (ferulic acid hydroxylase 1 [fahl] and sinapoylglucose accumulator 1 [sng1]) are discussed in detail. We have briefly touched upon, wherever relevant, the unique aspects in other plant species too.
Exciton Derealization in the Light‐Harvesting LH2 Complex of Photosynthetic Purple Bacteria
Authors: Dracheva Tatiana V. , Novoderezhkin Vladimir I. , Razjivin Andrei P.
Published: January 2008

Abstract— Absorption and circular dichroism spectra for both long‐wavelength bands of the antenna LH2 complex from photosynthetic purple bacteria have been calculated. Calculations were performed taking into account resonant interactions between all 27 bacteriochlorophyll (BChl) molecules for different values of site inhomogeneity. The exciton derealization length within BChl800 and BChl850 rings was estimated on the basis of calculated exciton wavefunctions for different temperatures and site inhomogeneity values. The relationship between anomalously high bleaching values in pump‐probe spectra and the exciton derealization length is discussed.
Voyage au Bout de la Nuit: The Beginning (1870–1951)*
Authors: Latarjet Raymond
Published: January 2008

This is a history of photobiology from its beginning in 1870 until 1951. In 1928, the Comité International de la Lumiére (C.I.L.) was founded. Up to this point, almost all of the research and activity occurred on the continent of Western Europe, and the research was largely medical. Thereafter, the area of organized photobiology broadened and, in 1951, the name was changed to Comité International de Photobiologie (C.I.P.).