bluuebunny/crossref_metadata_2025 huggingface dataset:
TYPE I AND TYPE II SENSITIZERS BASED ON ROSE BENGAL ONIUM SALTS*
Authors: Linden Shwn Meei , Neckers D. C.
Published: January 2008

Abstract— New Rose Bengal oniurn salts containing one or two iodonium, sulfonium, phosphonium, and pyrylium ions have been prepared as part of a program to develop sensitizers which can function as Type I radical photoinitiators and Type II energy transfer donors depending on experimental conditions. The absorption spectra of the onium salts in different solvents indicate an equilibrium between tight and loose ion pairs which depends on the solvent polarity, the cation and concentration. Typical Rose Bengal photochemistry requires the structure be that of the loose ion pair in the solvent of choice. Similar factors also influence bleaching behavior, and bleaching is the result of electron transfer processes. The quantum yields of singlet oxygen production from the onium salts in polar solvents are similar to that of the parent, Rose Bengal disodium salt.
ACUTE EFFECTS OF NEAR ULTRAVIOLET AND VISIBLE LIGHT ON THE CUTANEOUS ANTIOXIDANT DEFENSE SYSTEM
Authors: Fuchs J. , Huflejt M. E. , Rothfuss L. M. , Wilson D. S. , Carcamo G. , Packer L.
Published: January 2008

Abstract— Reactive oxygen species are considered to play an important role in cutaneous pathology. Enzymic and non‐enzymic antioxidants can prevent oxidative damage but may be overcome by strong pro‐oxidative stimuli. The acute effect of a single exposure to near ultraviolet (UVA)/visible radiation (> 320 nm) on various skin antioxidants was examined in hairless mice immediately after irradiation. Impairment of cutaneous catalase and glutathione reductase activity was observed. Superoxide dismu‐tase and glutathione peroxidase were not significantly influenced. Inhibition of catalase may render skin more susceptible to the damaging effects of hydrogen peroxide and its reaction products such as the hydroxyl radical. Partially diminished glutathione reductase activity is not accompanied by a change in reduced/oxidized glutathione level immediately after irradiation. There was a tendential (not statistically significant) decrease in cutaneous tocopherol, ubiquinol + ubiquinone 9 and ascorbic acid levels, either indicating direct photodestruction or consumption by reaction products of photooxidative stress. This partial impairment of the cutaneous antioxidant defense system by near ultraviolet/visible light, showing that the most susceptible component in skin is catalase, suggests possible pharmacological interventions.
TIME‐GATED FLUORESCENCE SPECTROSCOPY OF THE TUMOR LOCALIZING FRACTION OF HpD IN THE PRESENCE OF CATIONIC SURFACTANT
Authors: Cubeddu R. , Ramponi R. , Liu W.‐Q. , Docchio F.
Published: January 2008

Abstract—

Time‐gated fluorescence spectroscopy was performed on the tumor localizing fraction (TLF) of HpD in buffer at different concentrations of cationic surfactant. This technique obtains emission spectra with programmable delay relative to the excitation pulse. According to the measured fluorescence decay‐time constants (0.7, 3 and 15 ns) three gates were considered, delayed by 0, 5 and 18 ns, respectively, to evaluate the contribution of the emitting molecular species to the spectra. Simultaneous to these measurements, fluoresence decay waveforms and time‐integrated spectra were also detected. In buffer and in detergent micelles the fluorescence spectra are given by the superposition of the emission of the different molecular species present in the solution, and no appreciable interaction among the chromophores is observed. On the contrary, in the pre‐micellar range of the surfactant, evidence for the existence of an energy transfer mechanism was found. This effect seems to be related to the conflgurational state of the TLF polymeric chains and depends on the relative TLF/surfactant concentration.
CRITICAL IMPORTANCE OF THE TRIPLET LIFETIME OF PHOTOSENSITIZER IN PHOTODYNAMIC THERAPY OF TUMOR
Authors: Takemura T. , Ohta N. , Nakajima S. , Sakata I.
Published: January 2008

Abstract—

The relation between the lifetimes of the triplet states of various porphyrins and their photosensitizing effects on the photodynamic therapy (PDT) of tumor has been examined. Diethylene‐triamine pentaacetic acid ester of 4‐[1‐(2‐hydroxy‐ethyloxy)ethyl]‐2‐vinyl deuteroporphyrin‐IX gallium (III) complex (Ga‐DP), zinc (II) complex (Zn‐DP), and manganese (III) complex (Mn‐DP) and Photofrin II (PII) are used as the photosensitizer. The triplet lifetimes have been measured for the samples adsorbed on filter paper (FP) and found to be 57 ms (Ga‐DP), 26 ms (Zn‐DP), 610 |xs (Mn‐DP) and 9 ms (PII). The phosphorescence of Ga‐DP in tumor‐bearing golden hamsters are measured both in tumor tissue and in liver. They show bi‐exponential decay with the lifetimes of about 5 and 20 ms. From the values, the generation rate, kct[3O2], of singlet molecular oxygen in living animal tissue may be estimated to be an order of 102 s‐1. The PDT effects have been quantitatively investigated for in vitro experiments; upon irradiation the growth inhibitions of mouse p388 leukemia cells are obtained as a function of concentration of Ga‐DP, Zn‐DP, Mn‐DP and PII. The experimental results indicate that the PDT effects depend essentially on the triplet lifetimes of the photosensitizers.
CYTOTOXICITY AND MUTAGENICITY OF OPHTHALMIC SOLUTION PRESERVATIVES AND UVA RADIATION IN L5178Y CELLS
Authors: Withrow Thomas J. , Brown Natalie T. , Hitchins Victoria M. , Strickland Amparo G.
Published: January 2008

Abstract—

Four chemical preservatives commonly used in ophthalmic solutions were tested for their toxic and mutagenic potential in mouse lymphoma cells with and without exposure of the cells to ultraviolet A (UVA) radiation. The preservatives tested were benzalkonium chloride (BAK), chlorhexidine, thimerosal and ethylenediaminetetraacetic acid (EDTA). Cell survival and mutagenesis were measured using the L5178Y mouse lymphoma (TK+/‐) system. Cells were exposed to varying amounts of preservatives for 1 h at 37o.C, and then aliquots were irradiated with UVA radiation (during the exposure to preservative). Cells were then assayed for survival, and for mutagenesis at the thymidine kinase (TK) locus. In concentrations commonly found in ophthalmic solutions, BAK, chlorhexidine, and thimerosal were toxic to cells, and thimerosal was slightly mutagenic. When cells were exposed to preservative and UVA radiation, chlorhexidine was mutagenic and the mutagenic activity of thimerosal was enhanced.
TRANSVERSE LOCATION OF NEW FLUORENE BASED DEPTH DEPENDENT FLUORESCENT PROBES IN MEMBRANES ‐ QUENCHING STUDIES WITH 9,10‐DIBROMOSTEARIC ACID*
Authors: LALA ANIL K. , KOPPAKA V.
Published: January 2008

Abstract— Fluorescence quenching technique has been used to determine the transverse location of the fluorescent fluorenyl fatty acids in single bilayer vesicles prepared from phosphatidylcholine. The fluorenyl fatty acids used here are 2‐fluorenyl acetic, butyric, hexanoic and octanoic acid. In addition a new type of fluorescent probe, 7‐n‐butyl‐fluorene‐2‐butyric acid, wherein a hydrophobic tail is attached to 2‐fluorenyl‐butyric acid has also been used to study its effect on alignment of these probes in the membrane. The association properties of the quencher 9,10‐dibromostearic acid have been analysed. It is observed that the quencher association involves partitioning into the vesicles and does not involve any binding to the vesicles. The absolute partition coefficient of the 9,10‐dibromostearic acid which partitions between the aqueous and the lipid phases of the phospholipid dispersion has been evaluated. Using this information the corrected Stern‐Volmer plots were drawn and the bimolecular quenching constant evaluated.
SINGLET OXYGEN INDUCES FRANK STRAND BREAKS AS WELL AS ALKALI‐ AND PIPERIDINE‐LABILE SITES IN SUPERCOILED PLASMID DNA
Authors: BLAZEK ED ROBERT , PEAK JENNIFER G. , PEAK MEYRICK J.
Published: January 2008

Abstract

A covalently closed, circular, supercoiled plasmid was exposed to singlet oxygen by a separated‐surface sensitizer. For each exposure, the quantity of single oxygen entering the DNA target solution was estimated by its oxidation of histidine. After singlet oxygen exposure, some DNA samples were treated to disclose occult lesions. Agarose gel electrophoresis was then used to resolve the unrelaxed supercoils from the relaxed circular and linear species, and all bands were quantitated fiuorometrically. Exposure of supercoiled plasmid DNA to singlet oxygen induced frank DNA strand breaks, alkali‐labile sites (pH 12.5, 90°C, 30 min), and piperidine‐labile sites (0.4 M, 60°C, 30 min), all in a dose‐dependent manner. Yields of alkali‐labile and piperidine‐labile sites ranged from one to four times the frank strand break yield. Replacement of buffered H2O by buffered D2O as the DNA solvent for singlet oxygen exposures increased DNA lesion yields by a factor of 2.6 (averaged over lesion classes). Our data for the detection of frank strand breaks is at variance with published results from studies in which singlet oxygen was derived from a thermolabile endoperoxide dissolved in the DNA solution.
BIOLOGICAL UV‐DOSES AND THE EFFECT OF AN OZONE LAYER DEPLETION
Authors: DAHLBACK ARNE , HENRIKSEN THORMOD , LARSEN SøREN H. H. , STAMNES KNUT
Published: January 2008

Abstract

Effective UV‐doses were calculated based on the integratated product of the biological action spectrum (the one proposed by IEC, which extends to 400 nm, was adopted) and the spectral irradiance. The calculations include absorption and scattering of UV‐radiation in the atmosphere, both for normal ozone conditions as well as for a depleted ozone layer.

For Scandinavian latitudes the effective annual UV‐dose increases by approximately 4% per degrees of latitude towards the Equator. An ozone depletion of one percent increases the annual UV‐dose by approximately 1% at 60°N (increases slightly at lower latitudes). A large depletion of 50% over Scandinavia (60°N) would give these countries an effective UV‐dose similar to that obtained, with normal ozone conditions, at a latitude of 40°N (California or the Mediterranean countries). The Antarctic ozone hole increases the annual UV‐dose by 20 to 25% which is a similar increase as that attained by moving 5 to 6 degrees of latitude nearer the Equator.

The annual UV‐dose at higher latitudes is mainly determined by the summer values of ozone. Both the ozone values and the effective UV‐doses vary from one year to another (within ± 4%). No positive or negative trend is observed for Scandinavia from 1978 to 1988.
KINETIC MODEL OF BACTERIORHODOPSIN PHOTOCYCLE: PATHWAY FROM M STATE TO bR
Authors: CHERNAVSKII D. S. , CHIZHOV I. V. , LOZIER R. H. , MURINA T. M. , PROKHOROV A. M. , ZUBOV B. V.
Published: January 2008

Abstract

A model of the last parts of the bacteriorhodopsin (bR) photocycle is proposed on the basis of experimental data for the kinetic behavior of the ‘O’ intermediate during a temperature pulse in distilled water suspension. The model includes the previously proposed (but not well characterized) intermediate ‘N’ between the ‘M’ and ‘O’ states of bR. This intermediate exists in fast temperature‐dependent quasistationary equilibrium with the red‐shifted intermediate ‘O’ and has a maximum of absorption close to the bR spectrum.
PRODUCTION OF MALONALDEHYDE FROM SQUALENE, A MAJOR SKIN SURFACE LIPID, DURING UV‐IRRADIATION
Authors: DENNIS K. JASON , SHIBAMOTO TAKAYUKI
Published: January 2008

Abstract

Malonaldehyde (MA), a product of lipid peroxidation, is known to have a number of toxicological effects. Among skin surface components, squalene has been suggested as a significant source of MA following UV exposure. Irradiation of squalene coated on the inside surface of glass tubes served as a simple model to examine skin surface photochemistry. Malonaldehyde produced during UV‐irradiation was reacted with methyl hydrazine to form N‐methylpyrazole, which was then measured by gas chromatographic analysis. Ultraviolet A‐irradiation produced low levels of MA from squalene, with a maximum of 1.0 nmol MA/µmol squalene near 6 h. Malonaldehyde production varied with the energy of irradiation, with levels of 176 nmol/mg squalene and 9 nmol/mg squalene produced after 3 h of irradiation with UVB and UVA, respectively. The thiobarbituric acid (TBA) assay for lipid peroxidation showed large overestimations of MA levels under all irradiation conditions tested. The TBA assay predicted the highest levels of MA with UVC but we did not detect any MA with our assay.
ACRYLAMIDE QUENCHING OF TRYPTOPHAN PHOTOCHEMISTRY AND PHOTOPHYSICS
Authors: TALLMADGE D. H. , HuEBNERt J. S. , BORKMAN R. F.
Published: January 2008

Abstract— Studies of acrylamide quenching of tryptophan (Trp) fluorescence, photochemistry, and photoionization have been conducted. Quenching of Trp fluorescence in aqueous solution by addition of acrylamide in the concentration range 0.0–0.5 M was measured and resulted in a Stern‐Volmer quenching constant of Ksv= 21 ± 3 M‐1. Photolysis experiments were performed in which Trp was photolyzed at 295 nm in the presence of varying concentrations of acrylamide. The loss of Trp was monitored using reverse‐phase high performance liquid chromatography (RP‐HPLC) and was observed to follow first order kinetics. Production of N‐formylkynurenine (NFK) was observed by RP‐HPLC in irradiated Trp samples both in the presence and absence of added acrylamide. In addition, no new photochemical product was detected. This was taken as evidence that acrylamide did not alter the photochemical pathway but just reduced the reaction rate as expected for a physical quenching mechanism. Plotting the reciprocal of photolysis rate constant versus acrylamide concentration produced a Stern‐Volmer constant for quenching of Trp photochemistry of Ksv= 6 ± 2 M‐1. The Ksv values for both fluorescence quenching and photolysis quenching were thus large, implying efficient quenching of both processes by acrylamide. Assuming an excited singlet state lifetime of 2.8 ns, the calculated second‐order quenching rate constants for fluorescence and photolysis were kq= 7.5 × 109 and 2.1 × 109M‐1S‐1 respectively. The possible involvement of photoionization in the photolysis mechanism was investigated by studies of acrylamide quenching of voltage transients produced by xenon flash lamp excitation of Trp at aqueous/teflon or aqueous/mica interfaces. Plots of reciprocal photovoltage amplitude versus acrylamide concentration yielded linear Stern‐Volmer plots with Ksv= 5 ± 1 M‐1. This number may not be directly comparable to those obtained above for photolysis and fluorescence quenching, because quenching of photovoltage involved an excited Trp adsorbed on a teflon surface, while the former processes occurred in bulk solution. Nonetheless, the value of Ksv observed in the photoionization experiments showed that this process was also efficiently quenched by acrylamide.
SKIN PHOTOSENSITIVITY AND PHOTODESTRUCTION OF SEVERAL POTENTIAL PHOTODYNAMIC SENSITIZERS
Authors: ROBERTS W. GREGORY , SMITH KEVIN M. , MCCULIOUGH JERRY L. , BERNS MICHAEL W.
Published: January 2008

Abstract— The major side effect associated with porphyrins (Photofrin II) in clinical photodynamic therapy is skin photosensitivity. In order to avoid this deleterious reaction, patients must remain out of the sunlight for approximately 1 month. A possible procedure to reduce the amount of skin photosensitivity is to photodegrade (photobleach) the compound in the skin.

In this study, we report a series of experiments describing the photodegradation rates of two photosensitizers currently receiving attention due to their potential for use in PDT (mono L‐aspartyl chlorin e., and chloroaluminum sulfonated phthalocyanine). These compounds are compared to Photofrin II (Pfll). Experiments consisted of determining photodegradation rates and efficiencies of the sensitizers in (i) phosphate buffered saline (PBS), (ii) PBS with fetal calf serum (to enhance absorption and simulate cellular binding or deaggregation), (iii) Chinese Hamster Ovary cells, and (iv) Balb/c mice. We performed two standardized skin sensitivity assays using the Hartely albino guinea pig irradiated with a UV blue point lamp and Balb/c mice irradiated with the therapeutic wavelength of each sensitizer. In addition, we performed a cell clonogenicity assay comparing photodegraded and fresh Pfll on CHO cells. The photodegraded Pfll exhibited significant phototoxicity, although the fluorescence was bleached by more than 70%.

The results show that Pfll causes major skin photosensitization and that the other compounds produce no substantial skin sensitivity. Our studies suggest that photodegradation of Pfll with 630 nm light has little influence on the phototoxicity of the compound. In addition, skin sensitivity was not alleviated with prior photobleaching with 405 nm light.
In situPYRIMIDINE DIMER DETERMINATION BY LASER CYTOMETRY
Authors: MORI TOSHIO , WANI ALTAF A. , D'AMBROSIO STEVEN M. , CHANG CHIA‐CHENG , TROSKO JAMES E.
Published: January 2008

Abstract—By using antiserum against pyrimidine dimers and argon‐laser imaging microspectrofluoro‐metry, we established a new method to determine UV‐induced pyrimidine dimers and their repair in individual human cells. The method was sensitive enough to determine dimers induced by UV dose as low as 2 J/m2. Normal human cells repaired 50 and 60% of total damage within 8 and 24 h after UV irradiation (20 J/m2), butXeroderma pigmentosumcells (complementation group A) were unable to repair any within the same period. Therefore, the method proved to be a quick, easy, sensitive and accurate means to determine pyrimidine dimersin situ.
A FLUORESCENCE STUDY OF THE BINDING OF HOECHST 33258 and DAPI TO HALOGENATED DNAs
Authors: Hard Torleif , Fan Pei , Kearns David R.
Published: January 2008

Abstract— We have studied the time‐resolved and the steady‐state fluorescence of the DNA groove binders 4',6‐diamidino‐2‐phenylindole (DAPI) and Hoechst 33258 with the double stranded DNAs poly(dA‐dU) and poly(dl‐dC) and their halogenated analogs, poly(dA‐FdU) and poly(dI‐Br5dC). These studies were prompted by earlier observations that the steady‐state fluorescence of Hoechst 33258 is quenched on binding to halogenated DNAs (presumably due to an intermolecular heavy atom effect involving the halogen atom in the major groove), and recent studies which clearly point to a binding site in the minor groove of DNA. Measurements of the time resolved fluorescence decay demonstrate that the fluorescence of Hoechst 33258 is quenched on binding to the halogenated DNAs. in agreement with previous observations. However, quenching studies carried out using the free halogenated bases IdUrd and BrdCyd in solution yielded bimolecular rate constants more than one order of magnitude larger than those expected for an intermolecular heavy atom effect. Moreover, the quenching of the Hoechst 33258 fluorescence was accompanied by an accelerated photochemical destruction of Hoechst 33258. We therefore conclude that the fluorescence quenching observed with halogenated DNAs is probably due to a photochemical reaction involving Hoechst 33258, rather than direct contact of Hoechst 33258 with the halogen substituents in the major groove of the DNA. The fluorescence decay measurements however, do provide clear evidence for at least two different modes of binding. Taking into account the alternating sequences used in this study and the possibility of two different conformations for bound dye, at least four different modes of binding are plausible. Our present data do not allow us to distinguish between these alternatives.

The time‐resolved fluorescence decays and fluorescence quantum yields of DAPI are not affected by the presence of the heavy atom substituents in the DNA major groove. Based on this observation and earlier reports that DAPI binds in one of the DNA grooves, we conclude that the high affinity sites for DAPI on DNA are located in the minor groove.
INDUCTION OF Trichoderma SPORULATION BY NANOSECOND LASER PULSES: EVIDENCE AGAINST CRYPTOCHROME CYCLING
Authors: Horwitz Benjamin A. , Perlman Alexander , Gressel Jonathan
Published: January 2008

Abstract— An important question in the study of photoreceptor action in morphogenesis is whether the chromophore is unidirectionally photobleached, or whether it is recycled, allowing each receptor molecule to be counted more than once. The common soil fungus Trichoderma harzianum grows vegetatively in the dark and sporulates in response to a pulse of blue or UV‐A light. Colonies were grown at 26oC, transferred to 3oC, illuminated with non‐saturating light, and then put back at 26oC to sporulate. The fluence‐response curves for photoinduction in the cold and at 26oC were identical, indicating that there are no enzymatic transduction processes during irradiation. Regions of the perimeter of dark‐grown colonies were given single pulses (maximum duration, 30 ns) at 355 nm with a neodymium laser. We obtained a complete fluence‐response curve for the laser pulses, which agreed with data for irradiations in the second to minute range. Photoinduction at 3oC, and validity of Bunsen‐Roscoe reciprocity from nanoseconds to minutes, support the hypothesis that the inductive event is a simple first‐order photobleaching reaction.
LIGHT‐DEPENDENT CAROTENOID BIOSYNTHESIS IN MUTANT C‐6D OF Scenedesmus obliquus
Authors: Humbeck Klaus
Published: January 2008

Abstract— Pigment mutant C‐6D of the green alga Scenedesmus obliquus exhibits a light‐dependent chloroplast differentiation. The changes were analyzed by high performance liquid chromatography (HPLC). Dark‐grown cells of mutant C‐6D contain only precursors of carotenoids (carotene, neurosporene, lycopene and β‐zeacarotene). The lycopene and two neurosporenes were identified to be cw‐isomers. After transfer to light lycopene decreases rapidly. Simultaneously the other precursors increase for a short period and then decrease, too.

Using a specific HPLC‐system the changes in carotene‐ and xanthophyll‐content were analyzed. During the first 30 min of illumination the amount of β‐carotene increases very fast and then levels off. The kinetics of xanthophyll‐formation differ remarkably. Whereas lutein is synthesized immediately after onset of illumination, all other xanthophylls are formed with high rates only after a lag‐phase of about 30 min.

After illumination in the presence of nicotine no cyclic carotenes and xanthophylls could be detected. Instead of the cw‐lycopene these cells contain high amounts of the all‐trans lycopene.

The light‐regulation of the biosynthetic pathway leading to carotenes and xanthophylls in mutant C‐6D is discussed.
PHOTORECEPTORS CONTROLLING TRANSCRIPTION OF rbcS GENES IN GREEN LEAF TISSUE OF Pisum sativum
Authors: Clugston Carol K. , Barnett Linda K. , Urwin Nigel A. R. , Jenkins Gareth I.
Published: January 2008

Abstract— We have investigated the photoreceptors controlling transcription of genes encoding the small subunit (rbcS) of ribulose 1,5‐bisphosphate carboxylase‐oxygenase in green leaf tissue of pea (Pisum sativum). RbcS transcription was measured by hybridising labelled transcripts of isolated nuclei to rbcS cDNA clones. Transfer of green Pisum leaf tissue to darkness for 5 h causes a substantial decrease in the rate of rbcS transcription and the rate is restored rapidly when the plants are returned to white light. Low fluence rates of red light are ineffective in restoring the rate of rbcS transcription, suggesting that phytochrome alone does not fully mediate the response. Blue light is similarly effective to white light of an equal fluence rate (120 μmol m−2 s−1) in restoring the rate of rbcS transcription in the dark‐treated plants, indicating that a blue light photoreceptor is involved. However, red light at the same fluence rate produces about 65% of the effect of blue or white light, showing that the blue light photoreceptor is not the only photoreceptor controlling rbcS transcription in the green leaf tissue. The identity of the photoreceptor responsible for the red light effect is discussed. Similar effects of blue and red light are observed at the level of transcript abundance in dark‐grown pea leaf tissue given a brief illumination with red light, which potentiates the tissue for rapid transcript accumulation in white light.
PHYTOCHROME‐REGULATED EXPRESSION OF GENES ENCODING LIGHT‐HARVESTING CHLOROPHYLL a/b‐PROTEIN IN TWO LONG HYPOCOTYL MUTANTS and WILD TYPE PLANTS OF Arabidopsis thaliana*
Authors: Sun Lin , Tobin Elaine M.
Published: January 2008

Abstract— The cab genes which encode the light‐harvesting chlorophyll a/b‐protein (LHCP) are expressed normally with respect to phytochrome regulation in the hy‐3 and hy‐5 long hypocotyl mutants of Arabidopsis thaliana. In etiolated seedlings of these mutants as well as of the wild type, 1 min of red light elevates cab mRNA levels substantially within 2 h; this increase is reversed if far‐red light is given immediately after the red light treatment. We conclude that the genetic defects in these mutants do not affect steps in the signal transduction pathway leading to the regulated expression of cab genes. Additionally, the mRNA from one of the three known A. thaliana cab genes, AB140, is similar in quantity to the mRNAs from the other two, AB165 and AB180, in dark‐grown seedlings of hy‐3 and hy‐5 as well as the parent A. thaliana (Landsberg) after a brief red light treatment. This aspect of cab gene expression differs from the strain Columbia of A. thaliana in which AB140 mRNA is the predominant message. In mature white light‐grown plants of the strain Columbia, AB140 as well as a combination of AB165 and AB180 mRNAs are expressed at high levels, suggesting that AB165 and/or AB180 may be developmentally regulated.
A POSSIBLE CONTROL BY PHYTOCHROME and OTHER PHOTORECEPTORS OF PROTEIN ACCUMULATION IN THE GREEN ALGA Ulva rigida
Authors: López‐Figueroa F. , Rüdiger W.
Published: January 2008

Abstract— The effects of red, blue and green light pulses on total protein accumulation in the green alga Ulva rigida following transfer from a low to high nitrate medium in darkness were examined. Red light pulses prior to transfer to darkness increased protein accumulation by about 55%. Blue and green light pulses also stimulated protein accumulation, but to a lesser extent (40‐30% respectively). Stimulation of protein accumulation by red, blue or green light was largely (red light) or partially (blue or green light) reversible by far‐red. The role of phytochrome and a red/green photoreversible system in the control of protein synthesis is discussed.
PHYTOCHROME‐MEDIATED THRESHOLD CONTROL OF HYPOCOTYL GROWTH IN PARTLY DE‐ETIOLATED MUSTARD (Sinapis alba L.) SEEDLINGS
Authors: Oelze‐Karow Heidemarie , Mohr Hans
Published: January 2008

Abstract— Hypocotyl elongation in etiolated mustard (Sinapis alba L.) seedlings is known to be controlled by phytochrome (Pfr) through a threshold mechanism. The Pfr threshold value required to suppress hypocotyl growth was low (3 times 10−2% Pfr, based on total phytochrome in the hypocotyl at 36 h after sowing = 100%). In the present study the question was addressed whether the threshold control by Pfr of hypocotyl elongation also operates in light‐pretreated, partly de‐etiolated seedlings after transfer to darkness. The experimental results show that this is the case. Calculation of the threshold level in far‐red light pretreated seedlings led to a very low value (3 times 10−7%) compared to etiolated seedlings (3 times 10−2%). In red light pretreated seedlings the threshold level was calculated to be 9 times 10−7%. Since the light pretreatment affected the rate of degradation of phytochrome strongly (half‐life of Ptot in continuous red light was found to be 35 min in far‐red pretreated instead of 47 min in etiolated material), the difference in threshold level between far‐red and red pretreated material cannot be interpreted unambiguously. However, the conclusion can be drawn that light nretreatment strongly increases the degradation rate of Pfr and decreases the threshold level.
EVIDENCE FOR INVOLVEMENT OF PHYTOCHROME REGULATION IN MALE STERILITY OF A MUTANT OF Oryza sativa L.
Authors: Tong Zhe , Wang Tai , Xu Yang
Published: January 2008

Abstract— A rice mutant (Oryza sativa L. Nongken 58S) “Hubei photoperiod‐sensitive genie male‐sterile rice” (ms mutant) has been found to be male sterile under long day cycles (LD) and fertile in short day cycles (SD). After formation of the secondary rachis‐branch primodia the mutant plants under SD were interrupted in the middle of the long night phase (night break) for 10 days with 5 min pulses of red light (R) or far‐red light (FR). Rates of normal pollen and seed setting of the mutant treated by R or R → FR → R declined significantly, while the rates after FR or R → FR treatments were similar to those under SD alone. The result of these induction reversion experiments is consistent with the operational criteria for the involvement of photochrome. Wild‐type rice (O. sativa L. Nongken 58) under the same treatment showed no change in fertility. Experiments on the effect of different dark intervals (20 s to 15 min) between R and FR on male sterility of the ms mutant showed that the longer the dark interval, the greater the escape of R induction from FR reversibility. Treatment with SD or LD after formation of pollen mother cells had no influence on fertility of the ms mutant plants treated previously with R or FR night breaks.
In vitro EVALUATION OF PHOTOTOXIC PROPERTIES OF FOUR STRUCTURALLY RELATED BENZOPORPHYRIN DERIVATIVES
Authors: Richter Anna M. , Waterfield Elizabeth , Jain Ashok K. , Sternberg Ethan D. , Dolphin David , Levy Julia G.
Published: January 2008

Abstract— Four structural analogs of benzoporphyrin derivative (BPD) have been studied and compared for photosensitizing activity in vitro. All analogs have an identical reduced tetrapyrrol porphyrin ring, and differ by the position of a cyclohexadiene ring (fused at either ring A or ring B of the porphyrin) and the presence of either two acid groups or one acid and one ester group at rings C and D of the porphyrin. Photosensitizer activity was tested with the Ml tumor cell line using an assay (the MTT assay) which detects mitochondrial hydrogenases as a measure of cell viability. This assay was shown to be equivalent to the standard clonogenicity or [3H]thymidine uptake assay. Comparative studies with the BPD analogs showed that the monoacid derivatives had equivalent cytotoxicity and were about five‐fold more active than the diacid forms. This was the case whether the assays were performed in the presence or absence of fetal calf serum.
ULTRAVIOLET RESONANCE RAMAN SPECTROSCOPY OF BACTERIORHODOPSIN
Authors: Netto Madeline M. , Fodor Stephen P. A. , Mathies Richard A.
Published: January 2008

Abstract— Ultraviolet resonance Raman spectra of bacteriorhodopsin have been obtained using 229 nm excitation from a hydrogen‐shifted neodymium yttrium aluminum garnet (Nd: YAG) laser. High signal‐to‐noise spectra are observed exhibiting vibrational bands at 762, 877, 1011, 1175, 1356, 1552 and 1617 cm−1 which are assigned to scattering from tryptophan and tyrosine side chains. This demonstrates the feasibility of using UV resonance Raman spectroscopy to monitor aromatic amino acid structural changes during the bacteriorhodopsin photocycle.
PRODUCTS OF CHLOROPHYLL PHOTODEGRADATION–1. DETECTION and SEPARATION
Authors: Llewellyn Carole A. , Mantoura R. Fauzi C. , Brereton Richard G.
Published: January 2008

Abstract— The photodegradative fate of 14C‐radiolabelled phaeophytin a adsorbed on hydrophobic particles in an aqueous suspension is followed. An approximate mass balance is made for the hydrophilic, hydrophobic and CO, fractions. In addition, components of the colourless hydrophilic fraction produced from photodegrading chlorophyll a, phaeophytin a, phaeophorbide a and chlorophyll b are detected and separated using reverse‐phase ion‐pair and ion‐exclusion HPLC with UV detection. The increase in the hydrophilic molecules and the decrease in chlorophyll a are measured as the photodegradation proceeds.
PRODUCTS OF CHLOROPHYLL PHOTODEGRADATION–2. STRUCTURAL IDENTIFICATION
Authors: Llewellyn Carole A. , Mantoura R. Fauzi C. , Brereton Richard G.
Published: January 2008

Abstract— Hydrophilic products of chlorophyll a photodegradation are structurally identified using UV/visible and fourier transform infrared spectrophotometry and gas chromatography‐mass spectrometry. The major peak detected during reverse‐phase high performance liquid chromatography of the colourless photodegradation products is identified as glycerol. Lactic, citric, succinic and malonic acids, as well as alanine, are also identified.
ELECTROCHEMICAL SUPEROXIDATION OF FLAVINS: GENERATION OF ACTIVE PRECURSORS IN LUMINESCENT MODEL SYSTEMS
Authors: Mager Humphrey I. X. , Tu Shiao‐Chun , Liu Yaw‐Hwa , Deng Yuanjian , Kadish Karl M.
Published: January 2008

Abstract— Using 3‐methyllumifiavin and tetraacetylriboflavin as examples, we have shown that the so‐called “fully oxidized” flavins can be “superoxidized” at an anodic potential of 1.8 to 1.9 V giving flavin radical cation transients which are rapidly transformed in subsequent chemical reactions. An attack by H2O subsequent to the superoxidation of 3‐methyllumifiavin provides a route for the formation of 4a‐hydroxy‐3‐methyllumiflavin radical cation, as evident from the subsequent decomposition to the protonated form of the starting flavin. When 3‐methyllumiflavin is superoxidized in the presence of a base, a recycling process occurs, allowing superoxidized flavin to be trapped in a slower, competitive conversion. The relatively more stable trapped product is active in reacting with H2O2 to emit chemiluminescence. Electrochemical oxidation of H2O2 in acetonitrile at 1.30 V in the presence of an oxidized flavin results in a direct protonation of the flavin by H+ generated from the electrolysis of H2O2. Minor reactions presumably provide alternative formations of the 4a‐hydroperoxy‐ and 4a‐hydroxy‐flavin radical cation transients by the direct addition of HOO and HO‐ radicals, which also arise in the oxidation of H2O2, to protonated flavin. Under such conditions the superoxidized flavin radical cation is apparently also formed, either directly or by process(es) such as decomposition of the flavin 4a‐adduct radical cations. Subsequent reductions of either the superoxidized flavin or the flavin 4a‐adduct radical cations lead to an almost steady level of luminescence. The superoxidized flavin, the trapped product, and the N5‐unprotected, 4a‐derivatized flavin radical cations are considered valuable models in further studies on the validity of the chemically initiated electron exchange luminescence mechanism in flavin‐mediated luminescence reactions, including bacterial bioluminescence.
PHOTOCHEMICAL ONE‐POT SYNTHESIS OF VINBLASTINE and VINCRISTINE
Authors: Pennanen S. , Huhtikangas A.
Published: January 2008

The naturally occurring cytostatic dimer alkaloids vinblastine1and vincristine2were photochemically synthesized in slightly acidic aqueous solution from the monomer alkaloids catharan‐thine3and vindoline4. Multi‐centre reactions should obviously be involved and some of the principal photochemistry‐associated phenomena here discussed are quite likely to be characteristic even to the biosynthetic reactions yielding vinblastine1and vincristine2in the cells ofCatharanthus roseus.
NEW TRENDS IN THE DESIGN OF LUMINESCENT METAL COMPLEXES*
Authors: Balzani Vincenzo , Ballardini Roberto
Published: January 2008

Abstract—

The requirements needed for an ideal luminophore are discussed with reference to the luminescent properties of organic molecules and metal complexes. Recent strategies for the design of luminescent metal complexes are discussed, with particular emphasis on cage‐type complexes and oligonuclear homo‐ and hetero‐metallic complexes.
TIME‐RESOLVED LUMINESCENCE SPECTROSCOPY OF PHOTOSENSITIZERS OF BIOMEDICAL INTEREST*
Authors: Andreoni Alessandra
Published: January 2008

Abstract—

Studying the fluorescence decay of chromophores, either used as fluorescent labels to stain specific biomolecules or as photosensitizers to produce irreversible chemical or physicochemical modifications on biological substrates, is being demonstrated to be a valuable method of investigating the interactions underlying a variety of phenomena. In fact, all possible primary steps in a photosensitized biological system are phenomena that may occur during the chromophore S, lifetime and act as quenching mechanisms of the S, state. Thus they can be identified, and the relative importance of the corresponding transient species quantitatively determined, with suitable techniques of time‐resolved fluorescence spectroscopy. The examples discussed in this paper concern both tumor photosensitizing drugs, such as anthracyclines and porphyrins, and skin sensitizers (e.g. furocoumarins).
NEW FEATURES IN THE PHOTOPHYSICS and PHOTOCHEMISTRY OF 2‐(2'‐HYDROXY‐PHENYL)BENZOTHIAZOLES INTRODUCED BY AMINE SUBSTITUTION
Authors: Lenoble Christian , Becker Ralph S.
Published: January 2008

Abstract— –The photophysics and photochemistry of the 4′‐diethylamino derivative of both 2‐phenyl‐benzothiazole and 2‐(2′‐hydroxyphenyl)benzothiazole have been studied by nanosecond and microsecond laser flash photolysis and picosecond emission spectroscopy. For the non‐hydroxy substituted molecule, the singlet excited state was shown to relax primarily via fluorescence emission, and a very weak triplet transient was observed after laser flash excitation. The 2‐(2′‐hydroxy‐4′‐diethylamino‐phenyl)benzothiazole (AHBT) was shown to undergo excited state intramolecular proton transfer (ESIPT) in the picosecond timescale (k > 3 times 1010 s‐1) to form a colored zwitter‐ion/keto form in solution at room temperature while the ground state back proton transfer was slower by a factor of?105. However, in marked contrast with other derivatives of 2‐(2′‐hydroxyphenyl)benzothiazole and related molecules, the ESIPT was not the only deactivation process of the lowest singlet excited state of the enol form. Under steady‐state excitation at room temperature (and low temperature), the fluorescence emission of the enol form was observed. The T‐T absorption of the enol form was also observed and furthermore, the ESIPT was shown to have an activation energy which was estimated to be ? 4 kJ. None of the foregoing, fluorescence and T‐T absorption of the enol nor activation energy for proton transfer have been observed for the parent or derivatives of 2‐(2′ hydroxyphenyl)benzothiazoles. The striking new features for the ESIPT photochemistry and photo‐physics for the 4′‐diethylamino derivative of 2‐(2′‐hydroxyphenyl)benzothiazole are discussed and MO calculations are used to aid in the interpretation of some of the experimental results.
ACTIVITY AND PHYSICOCHEMICAL PROPERTIES OF PHOTOFRIN®
Authors: Ho Yau‐Kwan , Missert Joseph R. , Dougherty Thomas J.
Published: January 2008

Upon certain conditions of storage, Photofrin® samples changed their photodynamic therapy activity in mice. These samples showed similar absorption and high performance liquid chromatography (HPLC) profiles. The Photofrin® samples that were active, however, had higher relative fluorescence yields than those which failed. Active and inactive samples also had different characteristics when analyzed by gel filtration chromatography using Sephacryl S‐300; the failed samples had 60% or more high‐molecular‐weight fraction. The change of the amount of this high‐molecular‐weight fraction with the time of storage at room temperature could be clearly demonstrated. Results from fluorescence, HPLC and mass spectrometry studies suggest that the high‐molecular‐weight fraction may form by dehydration from or condensation between various components of Photofrin®.
CAROTENOIDS OF Erwinia herbicola AND AN Escherichia coli HB101 STRAIN CARRYING THE Erwinia herbicola CAROTENOID GENE CLUSTER
Authors: Hundle Bhupinder S. , Beyer Peter , Kleinig Hans , Englert Gerhard , Hearst John E.
Published: January 2008

Carotenoid pigments of Erwinia herbicola and a transformed strain of Escherichia coli carrying the carotenoid biosynthesis gene cluster of E. herbicola have been analyzed. Both organisms are capable of making essentially the same carotenoids, indicating that all of the genes required for the biosynthesis of the wild type E. herbicola carotenoids have been transformed intact into E. coli. The major products in both species of bacteria are p‐cryptoxanthin glucoside, zeaxanthin monoglucoside and zeaxanthin diglucoside. These compounds are the first example of secondary, non‐allylic carotenoid glucosides. The absolute configuration 3R,3′R for zeaxanthin diglucoside was determined from its circular dichroism spectrum. Both species of bacteria also accumulate small amounts of hydrocarbon carotenes with similar cisltrans isomerization states.
PHOTOINITIATED VECTORIAL TRANSMEMBRANE ELECTRON TRANSFER IN BILAYERS SENSITIZED BY A FACE TO FACE TRIPORPHYRIN ACTING AS A MOLECULAR ELECTRONIC DEVICE. AMPLIFICATION DUE TO IONIC COUPLING
Authors: Lamrabte A. , Janot J. M. , Bienvenue E. , Momenteau M. , Seta P.
Published: January 2008

Under light excitation transmembrane electron transfer is observed when a stacked Zn‐Cu‐Zn triporphyrin is incorporated in a bilayer between aqueous redox phases. The electric polarization of the membrane due to the photoinduced transmembrane charge flux drives ion transport. This effect increases the net charge transfer across the system, giving rise to an amplification similar to a field effect transistor. Thus this system can be considered an organic photo transistor.
ON THE EVIDENCE FROM HIGH‐INTENSITY TWO‐PHOTON LASER PHOTOLYSIS FOR ENERGY TRANSFER FROM HIGH‐LYING QUASI‐RYDBERG STATES OF THYMINE TO ISO‐ENERGETIC STATES OF WATER
Authors: Daniels Malcolm
Published: January 2008

High intensity two‐photon picosecond excitation at 266 nm (effective energy 9.2 eV) has been shown to cause efficient photolysis of thymine in aqueous solution. Experimental results for the quantum yield of solvated electrons, θ (e−aq), and the net consumption of thymine, θ(‐Thy) have been interpreted (Oraevsky and Nikogosyan, 1985) as indicating a stoichiometric excess of solvated electrons over thymine radical‐cations. To account for this under conditions in which direct two‐photon photolysis of water is negligible, it has been concluded that it is necessary to postulate the occurrence of extensive energy transfer from high‐lying thymine states to dissociating/ionizing states of water. This Note demonstrates that: (i) the supposed excess of e−aqdepends on an implicit assumption concerning the secondary radical reactions (dimerization) such that ‐ΔTh+=ΔThy+; if secondary radicals dismutate then ‐Thy =½δThy+, leading a stoichiometric deficit of e−aq; and (ii) the experimental results can be accounted for by a mixed dimerization/dismutation mechanism, without invoking energy transfer. Thus there is no evidence unambiguously requiring the postulate of energy transfer. But if it occurs, stoichiometry places restrictions on the extent of transfer and the nature of the secondary radical reactions.
ULTRAWEAK LIGHT EMISSION FROM RAT LIVER NUCLEI
Authors: Devaraj B. , Scott R. Q. , Roschger P. , Inaba H.
Published: January 2008

Abstract–An extremely weak native light emission from rat liver nuclei was detected and studied using a highly sensitive single photon counting system. This emission is oxygen dependent and we attribute it to (per) oxidative processes. The effects of deuterium oxide and l,4‐diazabicyclo‐[2.2.2] octane on the light emission suggests the possible involvement of singlet oxygen. The kinetic features of the underlying reactions including biphasic response to both oxygen and temperature changes, could be clearly discerned. Further study of this light emission can serve as a useful adjunct to biochemical investigations of oxidative processes which play an important role in mutation, carcinogenesis and aging.
MODIFICATION OF MEMBRANE COMPOSITION, EICOSANOID METABOLISM, AND IMMUNORESPONSIVENESS BY DIETARY OMEGA‐3 AND OMEGA‐6 FATTY ACID SOURCES, MODULATORS OF ULTRAVIOLET‐CARCINOGENESIS
Authors: Fischer Marie A. , Black Homer S.
Published: January 2008

Abstract–Dietary sources of lipids containing predominantly n‐3 or n‐6 fatty acids (FA) have been examined for effect upon several potential pathophysiologic parameters. Epidermal, plasma, and red blood cell (RBC) membrane FA composition exhibited marked differences between animals fed the respective dietary lipid sources. Reduced levels of 18:1, 20:3 and 20:4 occurred in the n‐3 FA fed animals which exhibited significantly higher levels of 20:5 and 22:6. Approximately equal levels of 18:2 were present in animals fed either diet. Despite marked differences in RBC membrane FA composition, only marginal effect upon osmotic fragility occurred. Lower levels of 20:3 and 20:4 found in n‐3 fed animals could result from a deficit of elongase and/or A5‐desaturase activity. Whether lower 20:4 levels in n‐3 fed animals could rate‐limit eicosanoid metabolism is unknown, but epidermal capacity to metabolise arachidonic acid in these animals was found to be closely related to n‐6 FA intake. Animals fed n‐3 FA exhibited markedly lower levels of plasma PGE2, even when the diet was supplemented with n‐6 FA. In addition, UV‐radiated animals receiving the n‐3 FA source demonstrated a reduced (30%) response to inflammatory stimulus and a greater (4.5‐fold) delayed hypersensitivity (DH) to dinitrochlorobenzene than animals fed the n‐6 FA source. These data demonstrate that dietary lipid strongly influences tissue FA composition, eicosanoid metabolism, and, in the case of DH, at least one type of T‐cell mediated immune response in UV‐irradiated animals.
THE INFLUENCE OF SMECTIC PHASES OF PERFLUORODECYL DECANE ON THE PHOTOREACTIONS OF PERFLUOROHEPTYL OCTYL KETONE. AN EXAMPLE OF MICROSCOPIC DISORDER IN HIGHLY ORDERED LAYERED PHASES*
Authors: Vilalta Patricia M. , Hammond George S. , Weiss Richard G.
Published: January 2008

The consequences of solvent order, imposed by the two smectic phases of 1,1,1,2,2,3,3,4, 4,5,5,6,6,7,7,8,8,9,9,10,10‐heneicosylfluoroeicosane (F10H10, a “diblock” molecule) on the photochemistry of 1,1,1,2,2,3,3,4,4,5,5.6,6,7,7‐pentadecylfluoro‐8‐hexadecanone (F7COH8) were investigated. Results from irradiations of F7COH8 in smectic F10H10 are compared to those obtained in hexane, perfluorohexane, and the isotropic phase of F10H10. They are complemented by 2H‐NMR experiments on F10H10 solutions of F7COH8 deuterated at the methylene alpha to the carbonyl, and differential scanning calorimetry thermograms. More than 85% of the photoproducts are derived from carbonyl reduction and Norrish II processes. Based upon the 2H‐NMR spectra and Norrish II photoproduct ratios, the microscopic environment experienced by the locus of reaction of F7COH8 in smectic F10H10 is not very restrictive towards the solute shape changes that must occur. This conclusion was not anticipated because the macroscopic order of the smectic phases of F10H10 is high.