bluuebunny/crossref_metadata_2025 huggingface dataset:
A PURIFIED 124‐kDa OAT PHYTOCHROME DOES NOT POSSESS A PROTEIN KINASE ACTIVITY*
Authors: KIM IN‐SOO , BAI UMA , SONG PILL‐SOON
Published: January 2008

Abstract The presence of protein kinase activity in the purified phytochrome preparations [Wong, et al. (1986) J. Biol. Chem.261, 12089–12097] has been re‐examined. The phytochrome preparations having SAR (specific absorbance ratio, A668/A280 for the Pr form as a measure of phytochrome purity) values of greater than 0.95 were homogeneous on SDS gel, but could be further purified to a SAR value of 1.07 by repeated gel filtrations on a Bio‐Gel A‐0.5 m column. The protein kinase activity remained in the phytochrome preparations having SAR values less than 1.05, but it became undetectable in the phytochrome preparation with a SAR value of 1.07. Two dimensional gel electrophoresis of the phytochrome preparation (SAR, 0.89) showed that a phytochrome band with pi 5.8 had no kinase activity. Phosphorylating activity of the protein kinase was enhanced to some extent by polycations, polylysine and histone. Phytochrome served as a good substrate for this enzyme. The present data indicate that phytochrome has no intrinsic protein kinase activity, but a protein kinase is present in highly purified phytochrome preparations.
DNA DAMAGE and ITS REPAIR IN Dictyostelium discoideum IRRADIATED BY HEALTH LAMP LIGHT (UV‐ B)
Authors: Okaichi Kumio , Kajitani Nobuyuki , Nakajima Katuko , Nozu Keiichi , Ohnishi Takeo
Published: January 2008

Abstract—

Irradiation by health lamp (HL) light (280–320 nm) more efficiently induced cell killing and mutation in a radiation sensitive mutant (TW8) of Dictyostelium discoideum as compared with the parental wild‐type strain (NC4). This light as well as a germicidal lamp‐light (254 nm) produced pyrimidine dimers. The dimers were removed from DNA molecules by excision repair in NC4, but more slowly in TW8. It is suggested that pyrimidine dimers are the main DNA damage caused by HL light in D. discoideum, and that this results in cell killing and induced mutation.
LIGHT PERCEPTION BY PHYTOCHROME in vivo*
Authors: Mancinelli Alberto L. , Lim Jui
Published: January 2008

Abstract—

The rate of phytochrome photoconversion in cotyledons and hypocotyls of dark‐grown seedlings of Cucurbita pepo varies significantly depending on the characteristics of the light field and the position of the sample in the light field. The overall pattern of the effects of light reflectance conditions and angle of incidence of light on phytochrome photoconversion in vivo is predictable and consistent with the results of physiological studies; however, the extent of the effects is much more difficult to predict with a satisfactory degree of approximation. The differences between phytochrome photoconversion kinetics measured in vivo and those predicted from photochemical parameters of purified phytochrome are rather large and suggest that the use of predictions as estimates of the state of phytochrome in vivo may be subject to significant limitations.
THE MICROVASCULAR EFFECTS OF PHOTODYNAMIC THERAPY: EVIDENCE FOR A POSSIBLE ROLE OF CYCLOOXYGENASE PRODUCTS
Authors: Reed Malcolm W. R. , Wieman T. Jeffery , Doak Karola W. , Pietsch Catherine G. , Schuschke Dale A.
Published: January 2008

Abstract—

Photodynamic therapy (PDT) of malignant tumors may involve the interruption of tumor and peritumor microcirculation. We have studied the effect of light activation of the photosensitizing drug dihematoporphyrin ether (DHE) on rat subcutaneous arterioles and the modulation of these effects by cyclooxygenase inhibitors indomethacin and acetyl salicylic acid (ASA). Animals received DHE 48 h prior to light activation and additionally either indomethacin, ASA or saline 3 h prior to treatment. Light activation (630 nm, 60 J/cm2) resulted in a significant reduction to 62 ± 2% SEM of initial blood flow. This effect was inhibited by ASA (98 ± 8% SEM) and indomethacin (87 ± 8% SEM). Results from the administration of various doses of both compounds indicate that this inhibition is dose related. The data presented here show that PDT causes a significant reduction in blood flow in normal arterioles and that this effect was inhibited by ASA and indomethacin indicating that prostaglandins or thromboxane A2 may play an important role in the microvascular response to PDT.
RESONANCE RAMAN SPECTRUM OF THE EXCITED 21Ag STATE OF ß‐CAROTENE
Authors: Noguchi T. , Kolaczkowski S. , Arbour C. , Aramaki S. , Atkinson G. H. , Hayashi H. , Tasumi M.
Published: January 2008

Abstract— Resonance Raman (RR) bands assignable to the 21Ag excited state of ß‐carotene are recorded using picosecond time‐resolved resonance Raman (PTR3) spectroscopy. The RR spectrum contains bands in both the C‐C (1204 cm−1, 1243 cm−1, and 1282 cm−1) and C=C (1777 cm−1) stretching regions. The time‐dependent intensities of these RR features, measured with ˜ 30 ps. resolution, are found (i) to closely correlate with picosecond transient absorption (PTA) data recorded at 575 nm on the same sample and (ii) inversely correlate with the time‐dependent intensities of RR bands assigned to the 11Ag ground state. Both of these observations support the assignment of these four RR features to the 21Ag excited state. These results remove uncertainties associated with earlier experiments in which excited‐state RR scattering from (3‐carotene was not observed in spite of predicted trends emanating from studies of shorter polyene compounds. The observed C=C band position also agrees with a recent report of this feature.
A ROLE FOR STEROLS IN THE PORPHYRIN MEDIATED PHOTOSENSITIZATION OF YEAST
Authors: Casey Warren M. , Parks Leo W.
Published: January 2008

–The yeast Saccharomyces cerevisiae was used as a model system to determine the role of sterols in the porphyrin mediated photosensitization of yeast. A sterol auxotroph, RD5‐R, was grown on sterols with different levels of unsaturation and assayed for photosensitivity in the presence of either protoporphyrin IX or hematoporphyrin (both at 100 μ,g/me). Cells grown on the completely saturated sterol (stanol), cholestanol. were substantially more resistant to the photosensitizing effects of the porphyrin. We hypothesize that this resistance arises from the inability of the porphyrin to mediate the oxidation of the membrane sterol. Our results indicate that photodegradation of the native yeast sterol, ergosterol, can account for substantial losses of cell viability.
HYDROGEN GENERATION FROM ARTIFICIAL SEA HATER IN A SEMICONDUCTOR SEPTUM ELECTROCHEMICAL PHOTOVOLTAIC CELL
Authors: TIEN H. TI , CHEN J.‐W.
Published: January 2008

Abstract

Visible light of the solar spectrum is directly converted to stored chemical energy of hydrogen from artificial sea water in a novel electrochemical photovoltaic cell. The principal element of the cell, modeled after the photosynthetic thylakoid membrane, is a semiconductor septum made of polycrystalline n‐CdSe thin film deposited on nickel foil, which separates two aqueous solutions. Under short‐circuit conditions, vigorous hydrogen evolution was seen at the Ni surface and continued as long as the cell was operated. The novel cell, the concept of which was derived from pigmented bilayer lipid membrane studies, is easy to construct, simple to operate, and appears to be a practical approach to the photochemical conversion and storage of solar energy.
A STUDY OF SOME POLYPYRIDYLRUTHENIUM(II) COMPLEXES AS DNA BINDERS AND PHOTOCLEAVAGE REAGENTS
Authors: TOSSI ALESSANDRO B. , KELLY JOHN M.
Published: January 2008

Abstract

The nature of the binding of several ruthenium polypyridyl complexes containing 2, 2`‐bipyridine (bipy), 4, 4`‐dimethyl‐2, 2`‐bipyridine (DMB), 1,10‐phenanthroline (phen), 4,7‐diphenyl‐1,10‐phenanthroline(DPP), 2, 2`, 2`‐terpyridine (terpy), 2, 2`‐biquinoline (biq), 1,4,5,8‐tetraazaphen‐anthrene (TAP) and 1,4,5,8,9,12‐hexaazatriphenylene (HAT), with calf thymus DNA, poly[d(A‐T)] and poly[d(G‐C)] were studied by absorption and emission spectroscopy, DNA melting techniques, and emission lifetime measurements. In low ionic strength phosphate buffer, spectroscopic changes and DNA stabilization depended on the polypyridyl ligands present, and indicated binding that varied from substantially electrostatic to intercalative. Ru(bipy)2(HAT)2+ and Ru(phen)32+, which bind by partial intercalation, also show a strong preference for poly[d(A‐T)]. The emission quantum yields for most complexes were increased in the presence of DNA. An exception was Ru(TAP)32+ which has a markedly reduced emission quantum yield and lifetime in the presence of poly[d(G‐C)] or CT‐DNA, due to photoredox interaction with guanines. Emission decays of the complexes generally showed multiexponential behaviour. The ability of the ruthenium complexes to sensitise DNA cleavage was determined using pBR322 plasmid DNA. Ru(TAP)32+ is the most efficient sensitiser while uncharged complexes and complexes with very short‐lived excited states do not cleave DNA.
ULTRAVIOLET RADIATION INDUCES A CHANGE IN CELL MEMBRANE POTENTIAL in vitro: A POSSIBLE SIGNAL FOR ULTRAVIOLET RADIATION INDUCED ALTERATION IN CELL ACTIVITY
Authors: GALLO RICHARD L. , KOCHEVAR IRENE E. , GRANSTEIN RICHARD D.
Published: January 2008

Abstract

The regulation of a transmembrane ionic gradient, reflected by the cellular membrane potential, has been shown in several cell systems to be involved in the regulation of cell function. This investigation presents evidence that biologically relevant doses of ultraviolet radiation (UVR) will alter the membrane potential of keratinocytes in vitro. Estimation of the relative change in the steady‐state membrane potential of the murine keratinocyte cell line PAM 212, the murine myelomonocytic cell line P388D., and normal human keratinocytes in culture, were made through the use of the lipophilic cationic membrane potential sensitive probe; triphenylmethylphosphonium. Our observations indicate that UVR composed primarily of UVB (280–320 nm) radiation at doses as low as 100 J/m2 can induce a depolarization in the murine cell lines and a hyperpoiarization in human keratinocytes. Evidence suggests that this difference in the direction of the membrane potential response reflects a difference in Na+/K+ ATPase activity following UVR. These results suggest a possible mechanism for modulation of keratinocyte activity induced by UVR.
ANTHRALIN‐DERIVED TRANSIENTS–I. THE TRIPLET STATE AND THE PRODUCTS OF ITS REACTION WITH OXYGEN IN BENZENE
Authors: BRUCE J. M. , GORMAN A. A. , HAMBLETT I. , KERR C. W. , LAMBERT C. , MCNEENEY S. P.
Published: January 2008

Abstract— Direct laser excitation in benzene of l,8‐dihydroxy‐9‐anthrone (anthralin) does not lead to transient species with lifetimes in the nanosecond time regime or longer. The triplet state has been produced in benzene by pulse radiolysis and characterised in terms of its absorption spectrum (Λmax 560 nm), natural lifetime (11 γ.s), self‐quenching properties (Ksq= 2.6 × 107 l mol‐1 s‐1) and triplet energy (234 kJ mol‐1). There is no tendency in the non‐polar medium for production of either the triplet or ground state in a tautomeric form. The observed triplet state reacts with oxygen with a typical rate constant, 2.2 × 109 l mol‐1 s‐1. The products of this reaction are singlet oxygen (∼64%) and the anthralin radical (∼14%).
FLUORESCENCE QUENCHING OF INDOLIC COMPOUNDS IN REVERSE MICELLES OF AOT
Authors: Lissi E. A. , Encinas M. V. , Bertolotti S. G. , Cosa J. J. , Previtali C. M.
Published: January 2008

Abstract— The fluorescence properties of indole, 1,2‐dimethylindole and tryptophan have been determined in sodium bis(2‐ethylhexyl)sulfosuccinate inverse micelles in heptane. Fluorescence quenching studies were done using CCl4 and acrylamide as quenchers localized in the organic and micellar pseudophase respectively. The Stern‐Volmer plots show departure from linearity and are dependent on the emission wavelength. The results were interpreted using a three pseudophases model. 1,2‐Dimethylindole is predominantly solubilized in the n‐heptane; however a small interaction with the micelles is apparent at high detergent concentration. Indole is distributed between the organic and the interfacial microphase with a partition constant of 34 ± 3, independent of the water content. Tryptophan is entirely localized at the interface. However the quenching experiments show that tryptophan molecules are not uniformly distributed in the interfacial pseudophase.
PHOTOOXIDATIVE DAMAGE TO LYSOSOMES OF CULTURED MACROPHAGES BY ACRIDINE ORANGE
Authors: Zdolsek Johann M. , Olsson G. Mikael , Brunk Ulf T.
Published: January 2008

Abstract— Cultured cells accumulate acridine orange (AO), which is a weak basic dye and a photosensi‐tizer, in lysosomes and other acidic compartments. During exposure to blue light, AO‐loaded macrophages show decreasing red granular fluorescence and increasing green diffuse fluorescence. This is hypothesized to represent peroxidative damage to lysosomal membranes resulting in an impaired proton gradient with deprotonation of the AO to its uncharged form and subsequent leakage of the dye. Further damage to the lysosomal membranes will result in release of lytic enzymes from the lysosomal compartment into the cytosol, leading to degeneration and finally cell death.

The survival of AO‐loaded and light‐exposed macrophages is controllable by varying the exposure times to blue light. Inhibition of lysosomal proteases by E‐64 results in increased cell survival after AO and blue light‐mediated damage, indicating a role of proteolytic enzymes in this type of damage.

Morphological analysis shows 'rounding up'with formation of retraction fibrils and pronounced plasma membrane blebbing. The formation of autophagic vacuoles is an early and pronounced event. After protease inhibition, however, all these phenomena are inhibitable to a considerable degree.

We have thus directed photooxidative damage selectively to lysosomal membranes and their contents. This technique will allow further detailed studies of the role of lysosomes in degeneration‐regeneration processes.
THE EFFECTS OF LOW DENSITY LIPOPROTEINS ON UPTAKE OF PHOTOFRIN II
Authors: Korbelik Mladen , Hung Jaclyn , Lam Stephen , Palcic Branko
Published: January 2008

Abstract— The cellular uptake of Photofrin II (PII) was studied using fluorescence imaging and chemical extraction. The influence of serum and low density lipoproteins (LDL) was examined under a variety of experimental conditions employing cultured human cells of different origins as well as a subcutaneously SMT‐F tumor implanted in mice. Results showed that serum inhibited PII uptake. In general, LDL also inhibits PII uptake with the exception of an initial increase in the first10–30 min when the cellular concentration of PII was measured by fluorescence imaging instead of chemical extraction. Our results suggest a possible de‐aggregation process occurring upon internalization or binding of PII to LDL.
FORMATION OF CYCLOBUTANE THYMINE DIMERS PHOTOSENSITIZED BY PYRIDOPSORALENS: A TRIPLET‐TRIPLET ENERGY TRANSFER MECHANISM
Authors: Costalat R. , Blais J. , Ballini J.‐P. , Moysan A. , Cadet J. , Chalvet O. , Vigny P.
Published: January 2008

Abstract— The 365 nm irradiation of thymine thin films in the presence of pyridopsoralens is shown to induce the formation of cyclobutane thymine dimers, in contrast to other compounds such as 8‐and 5‐methoxypsoralen. In order to elucidate the mechanism of such a photosensitized reaction, we have determined the energy of the lowest triplet state (T,) of these compounds, using phosphorescence spectroscopy and CNDO/S quantum chemistry calculations. The T, energy values were found to be significantly higher for pyridopsoralens–up to 0.3 eV–than for 8‐ and 5‐methoxypsoralen (approximately 2.8 eV), which are not able to photoinduce cyclobutane thymine dimers. The determination of the relative efficiency of cyclobutane thymine dimer formation was performed using chromatographic analysis. A good correlation was found between the energy of the T, state of the psoralen derivatives and the related cyclobutane thymine dimer formation. Moreover, the photosensitized cyclobutane thymine dimer formation appeared to be temperature‐dependent. Our results are consistent with a mechanism involving a triplet energy transfer from the pyridopsoralen to thymine.
SINGLET MOLECULAR OXYGEN INDUCED MUTAGENICITY IN A MAMMALIAN SV40‐BASED SHUTTLE VECTOR
Authors: Di Mascio P. , Menck C. F. M. , Nigro R. G. , Sarasin A. , Sies H.
Published: January 2008

Abstract— We have determined the deleterious effects of singlet oxygen CO,), generated by thermal decomposition of the water‐soluble endoperoxide 3,3'‐(1,4‐naphthylidene)dipropionate (NDPCX), on plasmid DNA. By following the electrophoretic mobility of DNA on agarose gels, we detected single and double strand breaks induced by treatment with NDPO2 The vector employed was a mammalian shuttle vector and the mutagenic consequences of these damages were investigated, using as mutation target the supF suppressor tRNA gene. A high increase of the mutation frequency, over the background, was observed in plasmids transfected in bacteria or after passage through mammalian cells. Trapping agents and quencher effects and other controls confirm the involvement of 'CK in DNA damage and mutagenicity. These findings indicate that 1O2 can induce DNA lesions which are repaired by an error‐prone process in prokaryotic and eukaryotic cells.
PHYTOCHROME‐MEDIATED PHOTOTROPISM IN Adiantum PROTONEMATA‐I. PHOTOTROPISM AS A FUNCTION OF THE LATERAL Pfr GRADIENT*
Authors: Iino Moritoshi , Shitanishi Kohji , Kadota Akeo , Wada Masamitsu
Published: January 2008

Abstract— Phytochrome‐mediated phototropism of the protonema of the fern Adiantum capillus‐veneris was studied in view of the hypothesis that phototropism is controlled by the gradient of Pfr (phytochrome in the far‐red‐absorbing form) across the short axis of the protonema. Fluence‐response relationships were investigated using a microbeam irradiation technique that allowed simultaneous stimulation of the two sides of the subapical portion of the protonema with different fluences of red light. Mathematical models describing the tropic response as a function of fluence were derived from the hypothesis in consideration of the minimal phototransformation kinetics of phytochrome. and the fitness of the functions to the experimental data was examined. The analytical results were then evaluated in view of the photochemical properties of phytochrome known from the literature. It is concluded that the extent of the tropic response is determined by the difference in the Pfr concentrations between the two sides of the protonemal cell. It is further suggested that, even if phytochrome exists as a dimer in vivo, the physiological unit of phytochrome is the monomer.
PHYTOCHROME‐MEDIATED FERN‐SPORE GERMINATION: INHIBITION BY ELEVATED TEMPERATURES*
Authors: Haupt W.
Published: January 2008

Abstract— The inhibition of light‐induced fern‐spore germination by elevated temperatures is only effective if this temperature treatment is given during coupling of the far‐red light‐absorbing form of phytochrome (Pfr) to the transduction chain. There is no evidence so far for enhanced dark destruction of Pfr as a main factor of this temperature effect.
CHARACTERIZATION OF A CALCIUM‐REQUIRING PHASE DURING PHYTOCHROME‐MEDIATED FERN‐SPORE GERMINATION OF Dryopteris paleacea Sw.*
Authors: Dürr S. , Scheuerlein R.
Published: January 2008

Abstract— For phytochrome‐mediated fern‐spore germination in Dryopteris paleacea Sw., initiated by a saturating red light (R) irradiation 20 h after imbibition, an almost absolute requirement for extracellular Ca2+ is found. To investigate the kinetics of this Ca2+ requirement spores were sown on a Ca2+‐free medium (Ca2+ < 10−8M) and Ca2+ was raised to 1 mM at defined periods after R. Alternatively, spores were sown on a Ca2+‐containing medium (1 mM) and transferred to a Ca2+‐free medium. A clearly defined period for the Ca2+ requirement is found between 30 and 50 h after R, while Ca2+ had to be present in the medium for at least 9 h to obtain half‐maximal germination. However, since the kinetics of deprivation and delayed addition of Ca2+ do not provide significantly different results, only a relative short presentation time for extracellular Ca2+ has to be expected at the level of a single cell. Ca2+ sensitivity is determined by the timing of the R irradiation, i.e. the timing of Pfr formation, which has been concluded from the observation that the variation of the imbibition time does not affect the kinetics of Ca2+ requirement and that the temporal application of polyethylene glycol (PEG), which is assumed to interrupt Pfr action, shifts the Ca2+ requirement to delayed intervals. These observations, as well as the fact that the requirement of Ca2+ has been observed for a limited period are interpreted as indirect evidence that Ca2+ action plays the role of a specific link in the phytochrome‐mediated signal‐transduction chain. The “Ca2+ kinetics” are compared with the kinetics of escape from reversibility by far‐red (FR) light and with kinetics of basic cell physiological processes occurring during germination. “Escape kinetics”, indicating “coupling” of Pfr to subsequent dark reactions, are observed at significant earlier intervals, and a gap of about 15 h is found for both the action of Pfr and of Ca2+. Thus, the direct interaction of Pfr with external Ca2+ as a first transduction step can be excluded experimentally. The kinetics of chlorophyll formation are found to be only slightly delayed, whereas the kinetics of mitosis are shifted by approximately 30 h. Almost the same slope is obtained for all kinetics investigated so far and one reaction spans a period of approximately 35 h. Obviously, variability found in the spore population is due to the coupling of Pfr whereas subsequent reactions proceed with almost identical velocity.
PHOTOTRANSFORMATION OF AGGREGATED FORMS OF PROTOCHLOROPHYLLIDE IN ISOLATED ETIOPLAST INNER MEMBRANES
Authors: Boddi Bela , Lindsten Agneta , Ryberg Margareta , Sundqvist Christer
Published: January 2008

Abstract— Irradiation of an etioplast inner membrane fraction caused the transformation of two photoactive spectroscopically different protochlorophyllide forms into two chlorophyllide forms. A weak light flash, 6% of a saturating flash, preferentially caused the formation of a short wavelength chlorophyllide form absorbing at 672 nm and emitting at 676 nm. A saturating flash resulted in the formation of the 684 nm absorbing form of chlorophyllide with an emission maximum at 698 nm.

The circular dichroism (CD) signals of the newly formed chlorophyllide forms indicated that they are pigment aggregates of different sizes. These aggregates are probably connected to protochlorophyllide reductase and NADPH or NADP. In the absence of NADPH a decomposition of the pigment aggregates took place as revealed by a decrease in the CD‐signal. A model is suggested which describes the structural changes of the pigment‐protein aggregates after irradiation.
ON THE SIGNAL‐TRANSDUCTION CHAINS OF TWO Pfr‐ MEDIATED SHORT‐TERM PROCESSES: INCREASE OF ANCHORAGE and MOVEMENT OF Mougeotia CHLOROPLASTS
Authors: Schonbohm Ekkehard , Schönbohm Elfriede , Meyer‐Wegener Jens
Published: January 2008

Abstract— We examined two published hypotheses on the signal‐transduction chain of the light‐oriented chloroplast movements in the fresh‐water alga Mougeotia. One hypothesis postulates a Ca2+‐influx controlled by a tetrapolar gradient of phytochrome in its far‐red light absorbing form (Pfr). The other hypothesis postulates anchorage sites for actin‐filaments even at those areas of the plasmalemma where phytochrome is in its inactive form (Pr). Calmodulin and Ca2+‐sequestering vesicles are assumed to be essential links of this transduction chain.

To test these hypotheses we have studied the effects of Ca2+‐entry blockers, Ca2+ deficiency and calmodulin antagonists on chloroplast movements and on chloroplast anchorage. None of our results support the Ca2+/calmodulin hypotheses mentioned above. The results and their implications (with regard to the role of Ca2', calmodulin and anchorage sites) are discussed.
PHYTOCHROME and PROTEIN PHOSPHORYLATION
Authors: Singh Bal Ram , Song Pill‐Soon
Published: January 2008

Abstract— The molecular mode of signal transduction triggered by phytochrome is unknown. One characteristic structural/topographic feature of the physiologically active form (Pfr) of phytochrome is that its tetrapyrrole chromophore becomes preferentially exposed in the Pfr form (compared to the Pr form). Phytochrome in its Pfr form appears to affect phosphorylation of cellular proteins. The literature on the phytochrome‐mediated protein phosphorylation has been reviewed in an attempt to search for the role of the chromophore topography of phytochrome in the signal transduction process. In order to initiate a dephosphorylation‐phosphorylation cascade as a possible step for the signal transduction, it may interact with a cellular protein kinase to inhibit its activity. This hypothesis has been reviewed with results from phosphorylation inhibition assays by the Pfr form of phytochrome and in light of the inhibition of protein kinase activity by tetrapyrroles in general.
THE PLASMA DISTRIBUTION OF BENZOPORPHYRIN DERIVATIVE and THE EFFECTS OF PLASMA LIPOPROTEINS ON ITS BIODISTRIBUTION
Authors: Allison Beth A. , Pritchard P. Haydn , Richter Anna M. , Levy Julia G.
Published: January 2008

Abstract— The plasma distribution and biodistribution of benzoporphyrin derivative were examined. Two analogs of benzoporphyrin derivative were mixed with human plasma in vitro and recovered in the lipoprotein fractions upon separation by chromatography or ultracentrifugation. The majority of both analogs was recovered with high density lipoprotein. The effect of prebinding benzoporphyrin derivative to lipoproteins on the biodistribution of the drug in vivo was studied in tumor bearing DBA/2J mice. At 3, 8 and 24 h post‐injection, tumor and tissue samples were excised and analyzed for benzoporphyrin derivative content. Precomplexing benzoporphyrin derivative with low density lipoprotein or high density lipoprotein led to significantly (P < 0.05) greater tumor accumulation than in aqueous solution.
THE ROLE OF CYCLIC ELECTRON FLOW AROUND PHOTOSYSTEM I and EXCITATION ENERGY DISTRIBUTION BETWEEN THE PHOTOSYSTEMS UPON ACCLIMATION TO HIGH IONIC STRESS IN Dunaliella salina
Authors: Canaani Ora
Published: January 2008

Abstract— The distribution of excitation energy between the two photosystems in the halophylic alga Dunaliella salina has been analyzed under ionic stress. In the transition from state 1 to state 2, it was found that a, the absorption cross‐section of photosystem (PS) I increased from 42 to 49% until an equal distribution between PS I and PS II was obtained in state 2. Acclimation of the algae to different salt concentrations did not change the fractions of light absorbed in PS II and PS I, but slowed down the transition time from state 1 to state 2. A large increase in ΔpH induced fluorescence quenching was observed which was abolished by the uncoupler nigericin. Photoacoustic quantum yield spectra of energy storage indicated a larger energy storage at 700 nm induced upon stress. The additional ΔpH quenching of fluorescence and the additional quantum yield of energy storage at 700 nm, in the stressed algae, are consistent with the operation of a cyclic, energy‐storing pathway in PS I which is uncoupler sensitive.
TRIPLET YIELD OF MEROCYANINE 540 IN WATER IS WAVELENGTH DEPENDENT
Authors: Seret A. , Hoebeke M. , Van de Vorst A.
Published: January 2008

Abstract— Monomers and aggregates of Merocyanine 540 (MC540) in water are able to photoisomerize. The shape of the photoisomer absorption spectrum is very similar to that of the ground state. Triplet state of MC540 in water has been produced by energy transfer from triplet anthracene and displays a broad absorption spectrum between 600 and 700 nm. The triplet state may also be produced by direct excitation of MC540 with UV light. However, when the dye is excited by visible light, no triplet state absorbance in the red could be detected so that the triplet yield of MC540 in water seems to be excitation wavelength dependent.
THE CHROMOPHORES AS ENDOGENOUS SENSITIZERS INVOLVED IN THE PHOTOGENERATION OF SINGLET OXYGEN IN SPINACH THYLAKOIDS
Authors: Jung Jin , Kim Hwan‐Su
Published: January 2008

Abstract— The photogeneration of singlet oxygen (1O2) from thylakoids and the chromophores involved as endogenous sensitizers were investigated using chloroplasts and thylakoids isolated from spinach. The blue light‐induced inhibition kinetics of photosynthetic electron transport and that of CTvCF, ATPase were also studied. The spectral dependence of the generation of 1O2 from thylakoid membranes, measured by the imidazole plus RNO method, clearly demonstrated that the Fe‐S centers play an important role in 1O2 generation, acting as sensitizers in thylakoids. The photoinhibition of the electron transport in isolated chloroplasts was strikingly depressed by a lipid‐soluble '02 quencher and enhanced by deuterium oxide substitution, indicating that the inhibition processes are mainly mediated by 1O2 which is produced via photodynamic activation. The involvement of chloroplast cytochromes in the production of 1O2 was deduced from the action spectrum for the photodynamic inhibition of the electron carrier chain. The results obtained from the kinetic studies appear consistent with the involvement of some components such as the Fe‐S centers and cytochrome chromophores of the carrier chain in the generation of 1O2.
INACTIVATION OF CITRIC ACID CYCLE ENZYMES AS A RESULT OF PHOTODYNAMIC SENSITIZATION BY MITOCHONDRIAL INNER MEMBRANE
Authors: Jung Jin , Kim Yong‐Jae
Published: January 2008

Abstract— Exposure to blue light of mitochondria under aerobic conditions resulted in inactivation of the regulatory enzymes of the citric acid cycle (CAC) contained in the mitochondrial matrix, except citrate synthase. When “soluble mitochondrial protein” was exposed to blue light under aerobic conditions, no significant loss of activity was observed for any CAC enzymes. However, the inclusion of submitochondria particles (SMP) in the photolysis system resulted in a substantial inactivation of the CAC enzymes. Of the CAC enzymes, NAD+‐specific isocitrate dehydrogenase (ICDH) appeared to be most susceptible to the membrane dependent‐photoinactivation. Imidazole protected the CAC enzymes against inactivation. In contrast, superoxide dismutase failed to protect them, except α‐ketoglutarate dehydrogenase. The photoinhibition of ICDH activity was drastically depressed in the presence of SMP whose Fe‐S centers were destroyed by the mersalyl acid treatment. The results obtained in this study suggest that the photoinactivation of the CAC enzymes in situ is mediated mainly by singlet oxygen, which is photoproduced primarily by the Fe‐S centers of mitochondrial membranes.
PHOTOSENSITIZED DAMAGE TO SUPERCOILED PLASMID DNA INDUCED BY 334‐nm RADIATION IN THE PRESENCE OF 2‐THIOURACIL CONSISTS OF ALKALI‐ and PIPERIDINE‐LABILE SITES AS WELL AS FRANK STRAND BREAKS
Authors: Churchill Mark E. , Schmitz Ann M. , Peak Jennifer G. , Peak Meyrick J.
Published: January 2008

Abstract— A covalently closed, supercoiled plasmid was irradiated with 334‐nm ultraviolet radiation in the presence of the naturally occurring photosensitizer 2‐thiouracil (s2Ura). After irradiation, some DNA samples were treated to reveal labile sites. Agarose gel electrophoresis was then used to resolve the unrelaxed supercoils from the relaxed forms, and the DNA bands were quantitated by fluorescence scanning. Irradiation of the plasmid in the absence of s2Ura induced small numbers of frank DNA strand breaks (FSB), alkali‐labile sites (ALS), and piperidine‐labile sites (PLS). The induction of each of these lesions was enhanced 30 times when s2Ura was present during aerobic irradiation. Anoxia, as well as the hydroxyl radical scavengers acetate and formate, inhibited the formation of all three lesion types. The relative proportions of the three lesion types produced by several DNA damaging treatments were measured. Hydrogen peroxide, γ‐irradiation, and s2Ura photosensitization produced nearly identical damage proportions, with PLS: FSB ratios of 1.25:1, 0.78:1, and 0.84:1, respectively. Treatment with singlet oxygen [data from Blazek et al. (1989) Photochem. Photobiol. 48,607–613] produced much different proportions, with a PLS:FSB ratio of 4.1:1. These results may indicate a role for hydroxyl radical in s2Ura‐photosensitized DNA damage.
QUANTUM YIELD OF PRODUCTION OF SINGLET MOLECULAR OXYGEN (xδg) IN AQUEOUS DISPERSIONS OF SMALL UNILAMELLAR LIPID VESICLES. A TIME‐RESOLVED NEAR‐IR PHOSPHORESCENCE STUDY*,†
Authors: Nonell Santiago , Braslavsky Silvia E. , Schaffner Kurt
Published: January 2008

The quantum yield of formation and kinetic behaviour of O2(1δg) in D2O dispersions of small unilamellar vesicles (SUVs) of dipalmitoyl phosphatidylcholine were studied by time‐resolved detection of near‐IR phosphorescence. At a SUV concentration of 26 nM, O2(1δg) is not quenched by the vesicles. It diffuses quickly through the lipid bilayer and a partition equilibrium of O2(1δg) between the lipid bilayer and the buffer is attained before decay occurs. In this equilibrium situation O2(1δg/sb>) is mostly located in the buffer phase, which permits the determination of absolute quantum yields for O2(1δg) production, φδ, by comparison of the luminescence in the dispersions with that in neat D2O. The maximal φδ values for the sensitizers incorporated in the SUV bilayer were 0.47 ± 0.09 for the dipyridyl complex of zinc(II) phthalocyanine (ZnPc), 0.35 ± 0.08 for porphycene, and 0.36 ± 0.08 for 2,7,12,17‐tetra‐H‐propylporphycene. These values are equal to those in neat organic solvents but lower than those previously obtained in SUVs by using chemical trapping agents. The high degree of organization of the environment around the sensitizers does not influence their efficiency of producing O2(1δg). While no concentration dependence is observed for ZnPc (at least up to a local concentration of 20 mM in the bilayer), φδ for both porphycenes significantly decreases above a local concentration of 4 mM in the bilayer. This result is expected in view of previous observations on the concentration dependence of other photophysical parameters of the porphycenes in such microheterog‐eneous media.
STUDY OF LUMINESCENT FORMS OF THE URANYL ION
Authors: Darmanyan Alexander P. , Khudyakov Igor V.
Published: January 2008

Abstract—

Luminescence spectra and luminescence decay kinetics of uranyl sulphate water and uranyl nitrate acetone solutions of different concentrations have been studied. Similar experiments have been done with uranyl sulphate powder under vacuum. It has been experimentally shown that the hydrolysis of uranyl sulphate in water takes place, and under low salt concentrations (0.1‐4.0 times 10‐4M) a luminescence of a basic form of the photoexcited ion with a tentative structure of UO2OH+* has been observed. The luminescence of the acidic form UO+* has been observed under higher salt concentrations (1–4 times 10‐2M) in water and under any salt concentration in acetone. The acidic form has the characteristic emission spectrum possessing vibrational structure. The luminescence concentrational quenching of both photoexcited uranyl forms and exciplex emission have not been observed. The effect of a number of organic quenchers and molecular oxygen on uranyl luminescence has been studied. There is no luminescence quenching by O2 up to 2 times 106 Pa (20 atm) pressure. The low effectiveness of energy transfer from the photoexcited uranyl forms has been explained in terms of strong steric screening of 5f‐uranium (VI) orbital by oxygen atoms and by external filled up uranium electronic shells.
ANTHRALIN‐DERIVED TRANSIENTS—II. FORMATION OF THE RADICAL BY SPONTANEOUS FRAGMENTATION OF BOTH SINGLET AND TRIPLET STATES OF THE 10,10′‐DEHYDRODIMER: RADICAL PAIR MULTIPLICITY EFFECTS
Authors: Bruce J. M. , Dodd N. J. F. , Gorman A. A. , Hamblett I. , Kerr C. W. , Lambert C. , McNeeney S. P.
Published: January 2008

Abstract—

The singlet and triplet states of the anthralin (1,8‐dihydroxy‐9‐anthrone) dehydrodimer have been produced selectively in benzene via pulsed laser excitation and pulse radiolysis respectively. The lifetime of S, is 30 ps, that of T, short but unspecified. Both states fragment spontaneously to yield a pair of anthralin radicals. The singlet radical pair predominantly undergoes geminate recombination within the solvent cage. In contrast, the corresponding triplet radical pair undergoes essentially exclusive cage escape to give the anthralin free radical (δ.max 370, 490 and 720 nm) which recombines under normal diffusive conditions. Both recombination processes lead, at least in part, to one or more species which have been assigned as tautomeric forms of the original dimer. The anthralin free radical in benzene is insensitive to the vitamin E model 6‐hydroxy‐2,2,5,7,8‐pentamethylchroman and reacts only slowly with oxygen.
THE INFLUENCE OF THE LIGANDS ON THE LUMINESCENCE OF METAL IONS*
Authors: Blasse G.
Published: January 2008

Abstract—

The nature of the ligands determines the luminescence properties of the central metal ion. This is illustrated on the following examples: (i) nonradiative transitions in the strong coupling model; (ii) nonradiative transitions in the weak coupling model; (iii) energy transfer from ligand to central ion. Several applications are dealt with. The cryptand ligands appear to play a special role.
RESEARCH NOTE
Authors: Schuster David I. , Heibel George E. , Caldwell Richard A. , Tang Wei
Published: January 2008

Abstract— –Energies and lifetimes of triplet states of a series of 2‐cyclohexenones have been measured in solution under ambient conditions by time‐resolved photoacoustic calorimetry (PAC). The PAC triplet lifetimes are in excellent agreement with lifetimes measured by kinetic absorption spectrophotometry (KAS) using nanosecond flash techniques, indicating that the present data indeed pertain to the enone triplets previously studied using KAS. The data demonstrate that, as previously proposed, the π,π* triplet energies in these systems are indeed correlated with triplet lifetimes, and vary sensibly with the anticipated extent of conformational flexibility of the C=C bond. No evidence supporting formation of metastable frans‐cyclohexenones was obtained. The data also demonstrate greater precision and, for lifetimes, greater accuracy than has hitherto been claimed for the PAC technique for study of transients with lifetimes in the 25 ns range.
UV‐INDUCED PROTEIN ALTERATIONS AND LIPID OXIDATION IN ERYTHROCYTE MEMBRANES
Authors: Kochevar Irene E.
Published: January 2008

Abstract— Certain ultraviolet radiation‐induced effects in skin may result from primary photochemical alterations in cell membranes. We have studied isolated erythrocyte membranes in order to determine the UV‐fiuence and wavelength dependence for protein alterations and lipid oxidation. Protein crosslinking was detected as high molecular weight protein (> 200 000 Da) on polyacrylamide/agarose gel electrophoresis. Spectrin decreased more rapidly than the other membrane proteins upon exposure to λ= 250–380 nm radiation. Nitrogen‐purging inhibited the UV‐induced decrease in spectrin by 60% and decreased crosslinking to an even greater degree. The decrease in spectrin was not inhibited by superoxide dismutase, catalase, or sodium azide. Radiation at 280 nm was most effective for spectrin loss, 265 and 297 nm were less effective and 254 and 313 nm were not effective. Prior irradiation at 280 nm did not sensitize the membranes to subsequent irradiation at 313 nm indicating that photodecomposition products of tryptophan are not involved. Lipid photooxidation was measured with the thiobarbituric acid assay and was induced at higher fluences of UV radiations than those required for loss of spectrin. These results indicate that the major effects of UV radiation on cell membranes are alterations of proteins and suggest that tryptophan is the major chromophore for these alterations.
ULTRAVIOLET‐B DOSE‐RESPONSE CURVES FOR LOCAL AND SYSTEMIC IMMUNOSUPPRESSION ARE IDENTICAL
Authors: Noonan Frances P. , Fabo Edward C. De
Published: January 2008

Abstract— –Irradiation of mice with UVB suppresses contact hypersensitivity either “locally”, i.e. when sensitizer is applied to the UV irradiated site, or “systemically”, i.e. when sensitizer is applied to a site distal to the site of irradiation. It has been suggested that local suppression requires lower doses of UV than does systemic suppression, and that different mechanisms are therefore responsible. We undertook a detailed analysis of the dose‐response and kinetics of UV‐induced local and systemic suppression of contact hypersensitivity to trinitrochlorobenzene in two strains of mice, C57BL/6 and BALB/c. We found that the UV dose‐responses for systemic and local suppression were identical within the same strain. Comparison, however, of UV dose‐responses between strains indicated that C57BL/6 mice required 6.4 times less UV than did BALB/c mice to generate an equivalent amount of suppression. In both strains, local suppression was initiated if sensitizer was applied immediately, or 1 or 3 days after completion of a single dose of UV. In contrast, systemic suppression was initiated only if sensitizer was applied 3 days after UV irradiation. Thus local suppression was generated in the absence of significant systemic suppression (but not vice versa), and this was dependent on time of application of sensitizer after UV irradiation, not on the dose of UV administered. Filtration of the UV source with Mylar indicated that UVB was responsible for initiating both local and systemic suppression. In summary, these results indicate that (1) genetically determined differences in susceptibility to UV suppression exist, (2) the time courses of generation of local and systemic suppression differ, and (3) the UV dose‐responses for local and systemic suppression are identical, and therefore use of the terms “low dose” and “high dose” to refer respectively to local and systemic suppression by UV irradiation are incorrect. We conclude that a common mechanism initiates UV‐induced local and systemic suppression of contact hypersensitivity by the immediate formation, at the site of UV irradiation, of an immunosuppressive signal which takes between 1 and 3 days to act systemically.
BIOLOGICALLY EFFECTIVE DOSES OF SUNLIGHT FOR IMMUNE SUPPRESSION AT VARIOUS LATITUDES AND THEIR RELATIONSHIP TO CHANGES IN STRATOSPHERIC OZONE
Authors: Fabo Edward C. De , Noonan Frances P. , Frederick John E.
Published: January 2008

Abstract— Using information on solar irradiance at different latitudes derived from a radiative transfer model and a detailed in vivo action spectrum for immune suppression in a murine system, we report here calculations of the “biologically effective” irradiance of sunlight for immune suppression. From 40°N to 40°S in summer, under normal stratospheric ozone concentrations this value ranged from 0.27 W/m2 (40°N or S) to a peak of 0.33 W/m2 (20°N or S) predicting that 50% immune suppression in the Balb/c mouse would occur after 21–26 min of sunlight exposure within this latitude range. We also found that the most effective wavelengths for immune suppression shift from a peak of 270 nm in the laboratory to near 315 nm in sunlight. Furthermore, using ozone depletion scenarios of 5 to 20%, at latitudes 20°S and 40°N, a 0.6% increase in biologically effective irradiance levels of solar UVB for immune suppression was predicted for each 1% decrease of ozone. This value rose to a nearly 1% increase for each 1% decrease in ozone at 60°N latitude in wintertime. These data indicate that activation of immune suppression, in a murine model, requires relatively low levels of sunlight and that these levels are easily obtainable over most of the populated regions of the world. Since a UVB‐activated photoreceptor, urocanic acid, regulates immune suppression in mice and since this same compound exists on other mammalian skin, including human skin, suppression of the mammalian immune system is predicted to increase if substantial stratospheric ozone depletion takes place.
SELF‐IRRADIATION EFFECT ON YEAST CELLS
Authors: Grasso F. , Musumeci F. , Triglia A. , Yanbastiev M. , Borisova S.
Published: January 2008

The effect of self irradiation on yeast cells has been investigated by counting the young gemmae formation in 104 self irradiated samples, as compared with an equal set of control samples. The results show that the rate of gemmae formation is higher in self irradiated samples; the statistical significance of the results is discussed.
COMPARATIVE PHOTO ACTIVITY OF TIN and ZINC PORPHYRIN INHIBITORS OF HEME OXYGENASE: PRONOUNCED PHOTOLABILITY OF THE ZINC COMPOUNDS
Authors: Greenbaum Nancy L. , Kappas Attallah
Published: January 2008

Metalloporphyrin inhibitors of heme oxygenase may also have photosensitizing properties in vivo. To assess photoactivity in serum, the relative ability to mediate photooxidation of tryptophan or other oxidizable targets, presumably by singlet oxygen production, was measured for tin mesopor‐phyrin, zinc mesoporphyrin, and zinc deuteroporphyrin bisglycol in aqueous solution and when bound to human serum albumin. While tin mesoporphyrin sensitized at the greatest initial rate in aqueous solution, the zinc compounds sensitized at a greater initial rate in detergent micelles or when bound to albumin. There was minimal alteration of the tin mesoporphyrin during the time course of illumination in the Soret or visible absorption regions. The zinc compounds, however, proved to be extremely photolabile and were extensively destroyed by light; the photooxidized forms were found to be ineffective as inhibitors of heme oxygenase.
AGE‐RELATED CHANGES IN THE FLUORESCENCE OF MELANIN and LIPOFUSCIN GRANULES OF THE RETINAL PIGMENT EPITHELIUM: A TIME‐RESOLVED FLUORESCENCE SPECTROSCOPY STUDY
Authors: Docchio Franco , Boulton Mike , Cubeddu Rinaldo , Ramponi Roberta , Barker Pierrette Dayhaw
Published: January 2008

The photophysical properties of purified populations of melanin and lipofuscin granules from human retinal pigment epithelium, and their changes with donor age, have been investigated using high‐sensitivity time‐resolved fluorescence spectroscopy techniques with picosecond gating capabilities. The overall fluorescence intensity of both melanin and lipofuscin granules clearly increased with increasing donor age, the increase being most marked for melanin. In all granule populations the fluorescence decays were multiexponential with subnanosecond and nanosecond decay components. The resultant time‐integrated and time‐gated spectra also exhibited marked age‐variations for each type of granule. Young melanin showed spectral patterns similar to those of bovine melanin, while a yellow‐orange fluorescence band appeared in melanin samples from older age groups. Lipofuscin granules exhibited a blue, a yellow and an orange band whose relative amounts were age‐related. The results demonstrate the potential of time‐resolved techniques for discriminating fluorophores in vitro and in situ, and have confirmed results previously obtained using extraction techniques. Furthermore, the ability of this technique to identify and quantify individual fluorophores within granules may provide an important insight into the origin and development of lipofuscin within the retinal pigment epithelium and ultimately into the mechanisms of age‐related retinal diseases.