bluuebunny/crossref_metadata_2025 huggingface dataset:
REPAIR OF THYMINE DIMERS AND (6–4) PHOTOPRODUCTS IN GROUP A XERODERMA PIGMENTOSUM CELL LINES HARBORING A TRANSFERRED NORMAL CHROMOSOME 9
Authors: Ishizaki Kanji , Matsunaga Tsukasa , Kato Mitsuo , Nikaido Osamu , Ikenaga Mituo
Published: January 2008

Abstract—

Transfer of a normal chromosome 9 into a xeroderma pigmentosum (XP)‐A cell line partially restored its DNA repair activity. XP‐A cell lines harboring a transferred chromosome were much more UV‐resistant than parental XP‐A cells but still more UV‐sensitive than normal cells. The amount of UV‐induced unscheduled DNA synthesis was only one‐third of that in normal cells. The repair of thymine dimers and (6–4) photoproducts in these cell lines was analyzed by using monoclonal antibodies raised against them. Although these XP‐A cell lines carrying a normal chromosome 9 could repair (6–4) photoproduct with a little lower efficiency than normal cells, the repair of thymine dimers was completely absent in these cells. The present results suggest a gene‐dosage effect in DNA excision repair mechanisms in human cells or a rather complicated mechanism which involves two or more pathways.
PHOTORECEPTOR PIGMENT IN Blepharisma: H+ RELEASE FROM RED PIGMENT
Authors: Matsuoka Tatsuomi , Murakami Yasunori , Furukohri Takahiro , Ishida Masaki , Taneda Koji
Published: January 2008

Abstract—

In faded cells of Blepharisma kept in a standard saline solution containing bacteria which had been cultured on agar plates containing glucose and polypepton, threshold light intensity for step‐up photophobic response elevated. This result suggests that red pigment (blepharismin) contained in Blepharisma cells is involved in the step‐up photophobic response. The pH of the aqueous solution of the red pigment was found to decrease when light was applied, indicating that the pigment releases H+ in response to light stimulation. However, faded pigment preparation by light irradiation did not show pH decrease. In the living cells faded by light irradiation, threshold light intensity for the step‐up photophobic response was raised. Results suggest that H+ release from the red pigment induced by light irradiation might be responsible for the step‐up photophobic response of the cells.
EFFECTS OF RHODAMINE 123 IN THE DARK AND AFTER IRRADIATION ON MITOCHONDRIAL ENERGY METABOLISM
Authors: Atlante Anna , Passarella Salvatore , Moreno Giuliana , Salet Christian
Published: January 2008

Abstract—

Isolated rat liver mitochondria have been used to study the mechanism of toxicity of Rhodamine 123 (Rho 123) in the dark and after irradiation with visible light. We report an inhibition of adenosine 5′‐diphosphate phosphorylation which is increased after illumination. In the dark, the first steps of the phosphorylation process (i.e. the entry of substrates into the matrix, the electron transport to oxygen and the creation of the proton gradient) as well as ATPase activity are not significantly perturbed at Rho 123 concentration below 10 μg/mL. In contrast, the movements of the phosphate compounds are drastically impaired. Irradiation strengthens the detrimental effects in an oxygen dependent process. The nature of the noxious transient species is not clearly established, but it is suggested that singlet oxygen could be responsible for the observed damage.
EFFECTS OF PHOTODYNAMIC TREATMENT OF PLATELETS OR ENDOTHELIAL CELLS in vitro ON PLATELET AGGREGATION
Authors: Henderson B. W. , Owczarczak B. , Sweeney J. , Gessner T.
Published: January 2008

Abstract—

The purpose of this work was to gain insight into the role played by platelets and endothelial cells in the development of thrombogenic vascular events, observed after in vivo photodynamic therapy (PDT), by studying the in vitro effects of PDT on isolated human platelets and cultured human and bovine endothelial cells. Exposure to Photofrin II (PII) and light caused platelets to rapidly lose their ability to aggregate. Photofrin II alone at high concentrations also exerted inhibitory effects on aggregation. Endothelial cells exposed to PII‐ and phthalocyanine (GaCI‐PcS2,3 or Zn‐PCS1,2)‐mediated PDT released potent platelet anti‐ and disaggregating activity which could be identified as prostacyclin by the following criteria: a close correlation between the time and dose dependent anti‐aggregating effects and released 6‐keto‐PGF1α (the spontaneous hydrolysis praduct of PGI, determined by radioimmunoassay), the inhibition of these effects by indomethacin, accumulation of 6‐keto‐PGF1α metabolite in the media of cells treated with PDT (as determined by HPLC analysis), and the absence of evidence for significant nitric oxide production. This prostacyclin release occurred following plasma membrane damage. Although no pro‐aggregating activity was observed, endothelial cells were found to release considerable amounts of arachidonic acid and prostaglandin F2α in response to PDT. These data, which indicate powerful anti‐thrombogenic effects in vitro, are in sharp contrast to the vascular effects of PDT in vivo which are characterized by severe platelet aggregation, and imply that the in vivo effects involve additional components of the vascular system.
LOW TEMPERATURE ABSORBANCE AND FLUORESCENCE SPECTROSCOPY OF THE PHOTOACTIVE YELLOW PROTEIN FROM Ectothiorhodospira halophila
Authors: Hoff W. D. , Kwa S. L. S. , Grondelle R. van , Hellingwerf K. J.
Published: January 2008

Abstract—

A simplified procedure was developed to purify the photoactive yellow protein (PYP) from Ecrorhiorhodospira halophila. Specific antibodies were used to follow the distribution of PYP through the separate purification steps. Low temperature absorbance and fluorescence characteristics of this photoactive protein were investigated.

The absorbance spectrum of PYP in 67% (vol/vol) glycerol peaked at 449 and 447 nm, at room‐and liquid nitrogen temperatures, respectively. It sharpened significantly upon cooling to 77 K and displayed fine‐structure on the blue side of its absorbance maximum, with a spacing of 25 nm.

At room temperature PYP fluoresced with a quantum yield of approximately 3.5 times 10−‐3 an emission maximum of 495 nm. Maximal excitation occurred at 457 nm, 10 nm red‐shifted with respect to the absorbance maximum. At ‐low temperature the excitation maximum remained unaltered but maximal emission shifted significantly to the blue (to 482 nm). The quantum yield of fluorescence increased to 0.07 at this temperature.

Illumination of PYP at low temperature with light from the visible part of the spectrum of electromagnetic radiation induced pronounced changes in its absorbance and fluorescence characteristics. At least two new stable intermediates were formed: one highly fluorescent, with an excitation maximum at 430 nm; additionally, a non‐fluorescent red‐shifted intermediate with an absorbance maximum at 490 nm. The amount formed of these two intermediates depended strongly on the wavelength of actinic illumination.

In combination, these data underline the spectroscopic similarities between PYP and the retinal‐containing chromoproteins that are present in Halobacterium halobium.
ISOPIMPINELLIN IS PHOTOBIOLOGICALLY INACTIVE
Authors: Ashwood‐Smith M. J. , Ceska O. , Warrington P. J.
Published: January 2008

Abstract—

Pure isopimpinellin is photobiologically inactive. Samples of isopimpinellin obtained by extraction of plants often contain small amounts of the active furocoumarin, 5‐methoxypsoralen, as an impurity. Thus the conflicting accounts of the photobiological activity of isopimpinellin are probably related to this impurity.
COTTON SEEDLING MORPHOGENIC RESPONSES TO FR/R RATIO REFLECTED FROM DIFFERENT COLORED SOILS AND SOIL COVERS
Authors: Kasperbauer Michael J. , Hunt Patrick G.
Published: January 2008

Abstract—

Cotton (Gossypium hirsutumL.) seedlings were morphologically responsive to red (R) and far‐red (FR) light (low and high FR/R photon ratios, respectively) from time of emergence. Controlled environment R and FR treatments confirmed phytochrome involvement in biomass allocation among new leaf, stem and root growth. Seedlings that received the high FR/R photon ratio developed longer and heavier stems, leaves with lower specific weights, less massive roots and higher shoot/root biomass ratios. Other cotton seedlings were grown in sunlight over different colored soils or painted panels to measure morphological effects of FR/R photon ratio in upwardly reflected light. Morphological responses to a given FR/R ratio were the same whether the reflection was from natural soil or from a painted surface. Seedlings that received the higher FR/R photon ratios in upwardly reflected light developed longer stems, leaves with lower specific weights, less massive roots and higher shoot/root biomass ratios. The potential use of colored mulches in agriculture was discussed.
AMELIORATION OF UV‐B DAMAGE UNDER HIGH IRRADIANCE. I: ROLE OF PHOTOSYNTHESIS
Authors: Adamse Paulien , Britz Steven J.
Published: January 2008

Abstract—

Sensitivity to ultraviolet‐B radiation (UV‐B,280–315 nm) is generally reduced when background irradiance is high. We tested the involvement of photosynthesis in the amelioration of UV‐B damage by treating plants at high PAR (photosynthetically‐active radiation, 400–700 nm; 1000 μmol m‐2 s‐1) with supplemental UV‐B at double ambient levels of biologically‐effective radiation (18 kJ m‐2d‐1) and either “ambient” (450 μmol mol‐1) or short term elevated (750 μmol mol‐1) CO2 levels. Responses to UV‐B were assessed by photosynthetic gas exchange, leaf expansion and production of UV‐absorbing compounds (presumptive flavonoids) in cultivars of cucumber (Cucumis sativus L.) previously demonstrated to be relatively sensitive (cv. Poinsett) and insensitive (cv. Ashley) to UV‐B. Except for marginal leaf interveinal chlorosis observed in Poinsett, both cultivars responded similarly. UV‐B had little direct effect on leaf photosynthesis, but it did cause reductions in leaf area and corresponding increases in leaf dry matter per area. Increased CO, stimulated plant growth, counteracting the effect of UV‐B on leaf growth and indicating an important role for photosynthesis. In contrast, the accumulation of UV‐absorbing flavonoid compounds was enhanced by UV‐B exposure but was not affected by COz enrichment.
PHYTOCHROME EVOLUTION: A PHYLOGENETIC TREE WITH THE FIRST COMPLETE SEQUENCE OF PHYTOCHROME FROM A CRYPTOGAMIC PLANT: (Selaginella martensii SPRING)
Authors: Hanelt Sabine , Braun Birgit , Marx Stefan , Schneider‐Poetsch Hansjörg A. W.
Published: January 2008

Abstract—

We have sequenced cDNA and genomic clones coding for phytochrome of the fern Selaginella. On the amino acid level, this phytochrome shares sequence homologies with phytochromes of higher plants which range between 62 (phytochrome E of Arabidopsis) and 55 (56)% [phytochrome C of Arabidopsis (Avena)]. Introns in the Selaginella gene are short and occupy positions known from phytochrome sequences of higher plants. A rooted phylogenetic tree based on mutation distances puts Seluginella phytochrome closest to the hypothetical ancestor. A similar tree arises if the tree is constructed with partial sequences (about 200 amino acids) around the chromophore attachment site. An extension of this tree by sequences of other cryptogamic plants (Mougeotia, Ceratodon, Psilotum) shows all these sequences including those of the phytochromes B and C of Arabidopsis on a branch, well separated from the branch formed by phytochromes known to accumulate in etiolated plants. The rooted phytochrome phylogenetic tree, however, is difficult to reconcile with the fossil record.
SIGNAL TRANSDUCTION BY PHYTOCHROME: PHYTOCHROMES HAVE A MODULE RELATED TO THE TRANSMITTER MODULES OF BACTERIAL SENSOR PROTEINS
Authors: Schneider‐Poetsch Hansjörg A. W.
Published: January 2008

Abstract—

A C‐terminal section of phytochromes turned out to share sequence homologies with the full length of the transmitter modules (about 250 amino acids) of bacterial sensor proteins. Coinciding hydrophobic clusters within the homologous domains imply that the overall folding of the two different types of peptides is similar. Hence, phytochromes appear to possess the structural prerequisites to transmit signals in a way bacterial sensor proteins do. The bacterial sensor proteins are known to be environmental stimuli‐regulated kinases belonging to two‐component systems. After sensing a stimulus by the N‐terminal part of the sensor protein, conformational alterations confer the signal to its (mostly) C‐terminal transmitter module which in turn is transitionally autophosphorylated at a conserved histidine. From the histidine the phosphate is transferred to the receiver module of a system‐specific regulator protein which eventually acts on transcription or enzyme activity. The histidine is not conserved in phytochromes. Instead, a conserved tyrosine is found spatially very close to the histidine position. This tyrosine might play the role of histidine, and kinase function might be associated with this part of phytochrome. In spite of this divergence, the structural similarities point to a common evolutionary origin of the phytochrome and bacterial modules.
ENHANCEMENT OF PHOTOREPAIR OF ULTRAVIOLET‐INDUCED PYRIMIDINE DIMERS BY PREILLUMINATION WITH FLUORESCENT LIGHT IN THE GOLDFISH CELL LINE. THE RELATIONSHIP BETWEEN SURVIVAL AND YIELD OF PYRIMIDINE DIMERS
Authors: Yasuhira Shinji , Mitani Hiroshi , Shima Akihiro
Published: January 2008

Abstract— The enhancement of photorepair of UV‐induced pyrimidine dimers by preillumination with fluorescent light, previously reported with RBCF‐1 cells derived from caudal fin of a goldfish, was studied in terms of clonogenic ability and yields of dimers. In the logarithmic growth phase, the ability of photorepair increased with the time after preillumination, reached a maximum at 8 h, and gradually declined. At 8 h, the dose decrement with the photorepair‐treatment for 20 min at 7.5 J/m2 UV increased by preillumination for 1 h from 1.6 to 3.1 J/m2 in terms of restoration of survival and from 1.2 to 4.3 J/m2 in terms of the disappearance of dimers. Incubation of the preilluminated cells in the medium containing cyclohexirnide (0.5 μg/mL) after preillumination until UV‐irradiation diminished their enhancement of photorepair. In the density‐inhibited state, the ability of photorepair was higher than in the log phase, and it was hardly enhanced by preillumination.
Cis‐UROCANIC ACID DOWN‐REGULATES THE INDUCTION OF ADENOSINE 3', 5'‐CYCLIC MONOPHOSPHATE BY EITHER trans‐UROCANIC ACID OR HISTAMINE IN HUMAN DERMAL FIBROBLASTS in vitro
Authors: PALASZYNSKI EDMUND W. , NOONAN FRANCES P. , DE FABO EDWARD C.
Published: January 2008

Abstract— It has been demonstrated that UVB radiation (290–320 nm) suppresses mammalian cell‐mediated immunity by effecting the trans to cis isomerization of urocanic acid (UCA) in the stratum corneum, the uppermost layer of the skin. Trans‐urocanic acid has been shown to be the photoreceptor for UVB‐induced immune suppression and the cis‐isomer has been demonstrated to be immunosuppressive. Little is known, however, about how the isomerization of UCA may affect the proximal or distal cells of the skin or the immune system. We report here that trans‐UCA is biologically active in vitro in human dermal fibroblasts, inducing adenyl cyclase as measured by cAMP (adenosine 3', 5'‐cyclic monophosphate) formation in a dose‐dependent manner similar to the action of histamine. Trans‐UCA and histamine stimulate 50% of maximum activity at concentrations of 3.3 μM end 13.8 μM respectively. Cis‐UCA does not increase cAMP in these human fibroblasts but actively down regulates the increase of cAMP induced by either histamine or trans‐UCA. Cis‐UCA down regulated the histamine response by 75% and the trans‐UCA response by 60% at a concentration range of 1 mM to 1 nM. The trans‐UCA induction of cAMP can also be downregulated with an H2 histamine receptor antagonist cimetidine. These results support the hypothesis that a cellular target for cis‐UCA is the dermal fibroblast and the effects reported here may represent the initial biochemical and cellular event for UVB‐induced immune suppression i.e. the immediate step following the isomerization of trans to cis‐UCA is the down regulation of cAMP by cis‐UCA. Regulation of such an important second messenger such as cAMP could then allow cascading signals to occur, leading to immune suppression.
BIOLOGICAL PROPERTIES OF SOME BENZOPSORALEN DERIVATIVES
Authors: Bordin F. , Carlassare F. , Conconi M. T. , Capozzi A. , Majone F. , Guiotto A. , Baccichetti F.
Published: January 2008

Abstract—The biological activity of some benzopsoralen derivatives, prepared with the aim of obtaining new drugs for photochemotherapy, has been studied. The more interesting compounds are 4‐hydroxy‐methyl‐4',5'‐benzopsoralen and 4‐hydroxymethyl‐4',5'‐tetrahydro‐benzopsoralen, which were found to be active in the dark also: DNA and RNA synthesis were both inhibited in Ehrlich cells, even if in a partially reversible fashion, while protein synthesis remained unaffected. In Chinese hamster ovary cells culturedin vitro, the clonal growth was strongly inhibited by incubation in the dark with both drugs, while a number of chromosomal aberrations was observed in the fraction of growing cells. Using alkaline elution, DNA strand breaks were detected. In addition, in the presence of aphidicolin, a specific inhibitor of DNA polymerase, the clonal growing capacity was completely restored; in contrast, the number of DNA strand breaks remained unchanged. All these results suggest that DNA topoisomerases are probably the target of these two benzopsoralens. These compounds are also good sensitizers; by UV‐A irradiation they have a good capacity to produce singlet oxygen, but they appeared to be unable to induce erythemas on guinea‐pig skin. Under UV‐A light, they induced a strong inhibition of DNA synthesis in Ehrlich cells. Thus, benzopsoralens appear to be capable of inducing strong antiproliferative effects by two different mechanisms, by UV‐A irradiation and in the dark.
QUANTUM YIELD VALUES FOR THE DECOMPOSITION OF SEVERAL SURFACE‐ACTIVE PHOTOREACTIVE AMPHIPHILES
Authors: McGarvey Colette E. , Holden David A. , Tchir Morris F.
Published: January 2008

Abstract— The quantum yield values for the decomposition of 12‐azido‐1‐diazo‐2‐dodecanone, 1‐diazo‐11‐dodecanone, 1‐diazo‐17‐octadecen‐2‐one, stearoyl azide and 10‐undecenyl azidoformate in hexane were determined. It was found that the compounds decomposed with relatively high quantum yields, suggesting their use in biological applications, especially for binding phospholipids to membrane proteins.
ULTRAVIOLET‐RADIATION INDUCED c‐jun GENE TRANSCRIPTION: TWO AP‐1 LIKE BINDING SITES MEDIATE THE RESPONSE
Authors: Stein Bernd , Angel Peter , Dam Hans van , Ponta Helmut , Herrlich Peter , van der Eb Alex , Rahmsdorf Hans J.
Published: January 2008

Abstract— In HeLa cells transcription of the c‐jun gene is activated strongly and rapidly by ultraviolet (UV) irradiation and, to a somewhat lesser extent, by treatment with phorbol ester tumor promoters. In the same cells UV and phorbol esters only marginally enhance the abundance of RNA transcribed from the jun D gene and from the gene coding for the serum response factor (which in turn acts on the UV and phorbol ester response element of the c‐fos gene). In contrast to c‐jun, jun B transcription is induced more efficiently by phorbol ester than by UV irradiation, suggesting that the members of the jun family are differently regulated. The promoter of c‐jun carries two enhancer elements resembling AP‐1 binding sites: the junl UV response element (URE‐71 TGACATCA‐64) and the jun2 URE (‐190 TTACCTCA‐183). These elements act independently in the UV induced expression of c‐jun. In the context of the complete c‐jun promoter they seem not to be required for c‐jun induction by phorbol esters. When fused to the Herpes simplex thymidine kinase promoter, however, the isolated elements mediate induction by both UV and phorbol esters. UV and phorbol ester treatment of cells increases the binding of transcription factors to both elements. Both elements bind factors different in modification or/and constitution from AP‐1, the heterodimeric transcription factor composed of c‐Fos and c‐Jun that controls the activity of the UV and phorbol ester response element (‐72 TGAGTCA‐66) of the human collagenase gene.
PHOTOBLEACHING OF MEROCYANINE 540: INVOLVEMENT OF SINGLET MOLECULAR OXYGEN
Authors: Singh Ravinder Jit , Feix Jimmy B. , Kalyanaraman B.
Published: January 2008

Abstract— The purpose of this study was to assess the mechanism of merocyanine 540 (MC540) photobleaching in a liposomal system. Broad based visible irradiation of MC540 in unilamellar dilauroylphosphatidylcholine (DLPC) vesicles resulted in dye bleaching that was strictly O2 dependent. The rate of self‐sensitized photobleaching was enhanced in D2O and inhibited by both azide and histidine, consistent with 1O2 intermediacy (Type II chemistry). Supportive evidence for this mechanism was obtained by using a Type II sensitizer, aluminum phthalocyanine tetrasulfonate (AIPcS Λmax, = 678 nm). Irradiation of AIPcS and MC540 in DLPC with Λ > 630 nm (absorbed only by AIPcS) light resulted in rapid bleaching of MC540, which was stimulated by D2O and inhibited by azide. A rate constant of 107M‐1 s‐1 was determined for the chemical quenching of 1O2 by MC540. The rate constant for physical quenching of 1O2 by MC540 was estimated to be ca 109M‐1 s‐1.
SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS. XVII. BENZANTHRONE
Authors: Dabestani Reza , Sik Robert H. , Motten Ann G. , Chignell Colin F.
Published: January 2008

Abstract—The photochemistry of benzanthrone (7H‐benz[de]‐anthracene‐7‐one) has been studied using electron paramagnetic resonance (EPR) in conjunction with the spin trapping technique and the direct detection of singlet molecular oxygen luminescence. Irradiation (Λcx= 394 nm) of benzanthrone (BA) in aerated ethanol, dimethylsulfoxide or benzene resulted in the generation of superoxide (O−2) which was trapped by 5,5‐dimethyl‐1‐pyrroline‐N‐oxide. The ethoxyl radical was also detected in ethanol. Photolysis of BA in deaerated basic ethanol led to the formation of BA anion radical, BA, which was detected directly by ESR. This radical anion decayed back to BA with a unimolecular rate constant of 1.5 × 10‐3s‐1. The1O2quantum yields (Λex> 345 nm) for BA in ethanol, 90% ethanol and basic ethanol (0.1NNaOH) were 0.89, 0.88 and 0.28 respectively relative to Rose Bengal. The lower yield of1O2in basic ethanol may be attributable to the reaction of oxygen with BA (which is generated in higher yield at alkaline pH) to give O−2. These findings suggest that on exposure to light BA can generate active oxygen species which may be responsible for the photocontact dermatitis caused by BA in industrial workers exposed to this chemical.
MULTIPLE MODALITY TREATMENT OF CARCINOMA CELLS WITH Pt(Rh‐123)2 PLUS X‐RAY PLUS LIGHT
Authors: Ara Gulshan , Varshney Archana , Ha Chul S. , Oseroff Allan R. , Herman Terence S. , Teicher Beverly A.
Published: January 2008

Abstract— A complex of platinum tetrachloride with two molecules of rhodamine‐123 (Rh‐123), Pt(Rh‐123)2, has been reported to act as hypoxic cell radiosensitizer of carcinoma cells in vitro and in vivo. In the present paper we report that Pt(Rh‐123)2 photosensitizes human mammary carcinoma (MCF‐7) cells and cis‐platinum resistant human mammary carcinoma (MCF‐7/CP) cells to 400–800 nm light in vitro. The efficiency of photosensitization by Pt(Rh‐123)2 was 10 times greater than for Rh‐123. Combination therapy using Pt(Rh‐123)2 plus x‐ray plus light was also much more effective compared to the combination therapy using Rh‐123 plus x‐ray plus light. After 15 μM of Rh‐123 plus x‐ray (0–8 Gy) plus light (5 J/cm2) treatment, cell survival curve was parallel to the x‐ray cell survival curve with an initial decrease in the surviving fraction corresponding to the drug plus light mediated killing. Cell killing caused by Rh‐123 (15 μM) plus x‐ray (0–8 Gy) plus light (5 J/cm2) was additive as determined by the product of the surviving fraction after Rh‐123 plus light and x‐ray. In contrast, for 15 μM of Pt(Rh‐123)2 plus x‐ray (8 Gy) plus light (5 J/cm2) treatment, whereas additive killing predicts a survival fraction of approximately 0.024, in reality, the combination therapy caused the survival fraction to decrease to 0.0012, implying that the cell killing was enhanced by a factor of 20. Using Pt(Rh‐123)2 plus x‐ray plus light, supraadditive cell killing was also observed under hypoxic conditions, although compared to normally oxygenated conditions the degree of cytotoxicity was significantly reduced. These results indicate that the platinum‐Rh‐123 complex acts both as a photo‐and radiosensitizer and should be a highly effective drug for use with combined photo and x‐irradiation.
PHOTOAGING EFFECTS ON SPECTRAL TRANSMITTANCE OF PLASTIC FILTERS
Authors: Miller Sharon A. , James Robert H. , Sykes Stephen M. , Beer Janusz Z.
Published: January 2008

Abstract— We examined the effects of ultraviolet (UV) radiation in combination with high levels of infrared (IR) radiation on the spectral transmittance of plastic filters. The biological action spectrum for damage to the human eye and skin changes dramatically in the 300–400 nm wavelength range. Cut‐off filters used in this region to shape the spectrum of exposure sources are thus critical to the design of experiments which use broadband light sources. The changes in transmittance of three types of plastic filters were observed over an exposure period of 1000 h. One set of three filters was exposed mainly to UV radiation, while the other set was exposed to UV radiation plus IR radiation. Filters exposed to both UV and IR radiation showed spectral changes in their transmittance, while the filters exposed to UV only showed no measurable changes.
PHOTOOXIDATION AND ELECTRON‐TRANSFER PROCESSES IN FREE‐BASE TETRAPHENYLPORPHIN PROBED BY RESONANCE RAMAN SPECTROSCOPY
Authors: Saini G. S. S. , Chaudhury N. K. , Verma A. L.
Published: January 2008

Abstract—We report here the resonance Raman studies of photooxidation of free base tetraphenylporphin (H2TPP) in the presence of external electron acceptors such as CCl4 and chloranil under selective laser irradiation. From the dependence of photooxidation on the concentration of electron acceptors, polarity of solvents, excitation lines and temperatures, we have inferred that a weak triplet exciplex formed between the excited H2TPP and electron acceptor in non‐polar solvents serves as transient species and the light‐induced intermolecular charge transfer from H2TPP to the electron acceptor is the primary process involved in photooxidation. Observation of partial photooxidation in the rigid matrix at low temperatures has been interpreted to be due to long‐range quantum mechanical electron tunneling process. Almost complete photooxidation is observed in a soft matrix as the donor and acceptor molecules can attain favorable relative orientation and separation for electron transfer during the excited state lifetime of the exciplex.
OXYGEN DEPENDENCE OF HYPERICIN‐INDUCED PHOTOTOXICITY TO EMT6 MOUSE MAMMARY CARCINOMA CELLS
Authors: Thomas Carin , Pardini Ronald S.
Published: January 2008

Abstract— The photodynamic effect of hypericin on EMT6 mouse mammary carcinoma cells was investigated in vitro under aerobic and hypoxic conditions. Under aerobic conditions, hypericin‐induced photocytotoxicity was dose dependent within a 1–50 μM range. Under hypoxic conditions, cells were resistant to hypericin‐induced phototoxicity. In the dark, no cytotoxicity was observed at any hypericin concentration tested either aerobically or hypoxically. Cellular accumulation of hypericin, examined by chemical extraction and spectroscopy, occurred under both hypoxic and aerobic conditions. Fluorescence photomicrographs of cells exposed to hypericin corroborate drug uptake in the plasma membrane and subcellular regions. Our results demonstrate that hypericin cytotoxicity to EMT6 mouse mammary carcinoma cells in vitro is both light and oxygen‐dependent. These results suggest that EMT6 cell kill caused by photoactivated hypericin is mediated by an oxygen‐dependent mechanism, rather than by a type I oxygen‐independent mechanism.
PHOTOPEROXIDATION OF CHOLESTEROL IN HOMOGENEOUS SOLUTION, ISOLATED MEMBRANES, AND CELLS: COMPARISON OF THE 5α‐ AND 6β‐HYDROPEROXIDES AS INDICATORS OF SINGLET OXYGEN INTERMEDIACY
Authors: Korytowski Witold , Bachowski Gary J. , Girotti Albert W.
Published: January 2008

Abstract— Singlet oxygen (1O2) can react with cholesterol (Ch) to give three possible ene‐addition hydroperoxides: 3β‐hydroxy‐5α‐cholest‐6‐ene‐5‐hydroperoxide (5α‐OOH), 3β‐hydroxycholest‐4‐ene‐6α‐hydroperoxide (6α‐OOH), and 3β‐hydroxycholest‐4‐ene‐6β‐hydroperoxide (6β‐OOH). The rates of dye‐sensitized photogeneration and also the fates of 5α‐OOH and 6β‐OOH in membrane bilayers have been studied and compared. Irradiation of unilamellar [14C]Ch/phospholipid vesicles in the presence of aluminum phthalocyanine tetrasulfonate or merocyanine 540 resulted in formation of 5α‐OOH and 6β‐OOH, as determined by high performance liquid chromatography with radiochemical or electrochemical detection. The initial rate of 6β‐OOH formation was 335% that of 5α‐OOH in a variety of liposomal systems. However, after a lag, 5α‐OOH invariably decayed via allylic rearrangement to 7α‐OOH (also known to be a free radical product), whereas 6β‐OOH accumulated in unabated fashion until Ch depletion became limiting. Photooxidation of Ch in an isolated natural membrane (erythrocyte ghost) or in L1210 leukemia cells gave similar results. When the reaction was carried out in pyridine or methanol, the rate of 6β‐OOH formation relative to 5α‐OOH was reduced by approximately half, with essentially no isomerization of the latter to 7α‐OOH. These results suggest that (i) environmental factors in a lipid bilayer somehow make photogeneration of 6β‐OOH more favorable than in homogeneous solution; and (ii) due to its relative stability, 6β‐OOH may be a more reliable probe of 1O2 intermediacy than 5α‐OOH.
EVIDENCE FOR AN ULTRAVIOLET SUNSCREEN ROLE OF THE EXTRACELLULAR PIGMENT SCYTONEMIN IN THE TERRESTRIAL CYANOBACTERIUM Chiorogloeopsis sp.
Authors: Garcia‐Pichel Ferran , Sherry Nelson D. , Castenholz Richard W.
Published: January 2008

Abstract— The proposed photoprotective role of the UV‐A absorbing, extracellular pigment scytonemin was studied in the terrestrial cyanobacterium Chlorogloeopsis sp. strain O‐89‐Cgs(1). UV‐A (315–400 nm) caused growth delay, cell growth restarting only when scytonemin had accumulated in the extracellular envelopes. Cultures with scytonemin were more resistant to photoinhibition of photosynthesis than cultures without scytonemin, the differential resistance being much greater to UV‐A‐caused photoinhibition than to photoinhibition caused by visible light. The presence of scytonemin in the extracellular envelopes was correlated with the inability of UV‐A radiation to induce strong photopigment fluorescence (685 nm emission), regardless of the specific content os photosynthetic pigments. The physical removal of the scytonemin containing extracellular envelopes brought about the loss of UV‐A resistance as measured by photobleaching rates of chlorophyll a under conditions of physiological inactivity (desiccation). These observations provide strong evidence for the proposed protective role of scytonemin, as a passive UV‐A sunscreen, in cyanobacteria.
SPECTRAL ANALYSES OF LOW LEVEL CHEMILUMINESCENCE OF A SHORT LIFETIME USING A HIGHLY SENSITIVE POLYCHROMATIC SPECTROMETER INCORPORATING A TWO DIMENSIONAL PHOTON‐COUNTING TYPE DETECTOR
Authors: Nagoshi Toshiyuki , Watanabe Nobuyuki , Suzuki Sohkichi , Usa Masashi , Watanabe Haruo , Ichimura Tsutomu , Inaba Humio
Published: January 2008

Abstract—Spectral analyses of low level chemiluminescence were carried out by using a newly developed polychromatic spectrometer in which a diffracted photon emission was detected simultaneously using a two dimensional photon‐counting device. The spectrometer was sensitive in the 400–800 nm wavelength range. Low level chemiluminescence generated in a 1 nM luminol solution could be detected as a spectrum, showing a peak at 430 nm. Short lifetime photon emission from singlet oxygen showed only two peaks at around 630 and 700 nm in this highly time‐resolved spectroscopy. Lipid peroxidation of linoleic acid by the lipoxygenase emitted a low intensity peak centered at 440 nm, but singlet oxygen emission arising from the decomposition of lipid peroxide was not observed. An injured cotyledon of a soybean seedling gave a broad emission centered at 725 nm in the absenceofhydrogen peroxide, while in its presence a different emission peak appeared at a shorter wavelength (515 nm). Oxygenated, fluorescent components in the soybean seedling may be the emitting species. Singlet oxygen and triplet carbonyl groups were shown to be unlikely sources of the emission.
SPECTRAL INHOMOGENEITY OF THE LIGHT‐HARVESTING ANTENNA OF Rhodospirillum rubrum PROBED BY TRIPLET‐MINUS‐SINGLET SPECTROSCOPY AND SINGLET‐TRIPLET ANNIHILATION AT LOW TEMPERATURES
Authors: Mourik Frank van , Visscher Kees J. , Mulder Jan M. , Grondelle Rienk van
Published: January 2008

–Triplet‐minus‐singlet (T‐S) spectra and singlet‐triplet annihilation was measured on Rhodospirillum rub‐rum chromatophores at low temperatures (4–77K). The T‐S spectrum of the LH‐1 antenna was dependent on the wavelength of excitation and thus indicative of site‐inhomogeneous broadening. The data cannot be understood adequately using the two pigment pool model (B880 + B896) but, in contrast, support a model for LH‐1, in which the spectral properties are determined by site‐inhomogeneous broadening. Consequently, the 4 K antenna domain for singlet‐triplet annihilation in LH‐1 is rather small. If the temperature is raised to 77 K the annihilation domain increases, and a fit of the fluorescence quenching and triplet yield data suggests that at 77 K the connectivity is between the extreme cases of the “lake” and the isolated “puddles” models. The implications of the observed antenna inhomogeneity on low temperature annihilation and fluorescence measurements are discussed.
COHERENT MOTION AND TRANSFER OF EXCITATION ENERGY IN THE PRIMARY PROCESSES OF PHOTOSYNTHESIS
Authors: Klevanik Alexander , Renger Gernot
Published: January 2008

Fluorescence decay curves are calculated within the framework of the Liouville von Neumann equation for simple model systems of a photosynthetic unit consisting of a reaction center coupled to either a linear chain or a hexagonal array of identical antenna pigments. A comparison of the results with those obtained by solving the Pauli Master equations reveals that in the case of coherent excitation energy transfer the fluorescence decay kinetics exhibit a strong dependence on the topological array of the antenna pigments. For systems with a different pigment array, markedly different kinetics can be expected upon decreasing the pure dephasing time.
REVERSIBLE PHOTOCHEMISTRY IN THE α‐SUBUNIT OF PHYCOERYTHROCYANIN: CHARACTERIZATION OF CHROMOPHORE AND PROTEIN BY MOLECULAR DYNAMICS AND QUANTUM CHEMICAL CALCULATIONS
Authors: Scharnagl C. , Fischer S. F.
Published: January 2008

The ground and excited state properties of two regions in the Δ15‐configurational space of the phycoviolobilin chromophore in the α‐subunit of phycoerythrocyanin are analyzed. Molecular dynamics calculations reveal that the chromophore geometry determines the active‐site dynamics. The excited state torsional potential surface shows a negative barrier for isomerization and trapping of an activated complex. Strong coupling of excited states localized in the chromophore and charge transfer states from the surrounding polar residues provides favorable prerequisites for fast excited state surface crossing in competition with other deactivation processes. The formation of a photoreduced intermediate following the photoinduced charge transfer may trigger subsequent chemical reactions.
AQUEOUS AGGREGATES OF BACTERIOCHLOROPHYLL c AS A MODEL FOR PIGMENT ORGANIZATION IN CHLOROSOMES
Authors: Miller Mette , Gillbro Tomas , Olson John M.
Published: January 2008

Chlorosomes isolated from Chloroflexus aurantiacus were extracted with chloroform/methanol. The extract contained bacteriochlorophylls c and a and lipids, but was devoid of proteins. This crude extract spontaneously formed aggregates when a methanol solution was dispersed in aqueous buffer.

The aggregates could be sedimented by ultracentrifugation and appeared in electron micrographs as stain‐excluding bodies with diameters between 70 and 170 nm. The absorption spectrum is remarkably similar to that of intact chlorosomes with an absorption maximum of bacteriochlorophyll c at around 740 nm. The circular dichroism spectrum of the aggregate is also very similar to that of intact chlorosomes. A conservative (±) band centered at 740 nm confirms the highly aggregated state of bacteriochlorophyll c in both systems.

Steady‐state fluorescence studies showed that in the aggregate energy‐transfer from bacteriochlorophyll c to a component emitting at 830 nm took place. When the aggregate was suspended in buffer saturated with 1‐hexanol the 740 nm form of bacteriochlorophyll c was reversibly converted to a form with spectral properties resembling the monomer absorbing at 670 nm but still in an aggregated state. This form of bacteriochlorophyll c showed no circular dichroism signal.
TEMPERATURE DEPENDENCE OF PICOSECOND FLUORESCENCE KINETICS OF A CYANOBACTERIAL PHOTOSYSTEM I PARTICLE*
Authors: Turconi Sandra , Schweitzer Gerd , Holzwarth Alfred R.
Published: January 2008

Picosecond time‐resolved fluorescence of photosystem I particles isolated fromSynechococcussp. was recorded in the wavelength range from 680 nm to 736 nm for temperatures of 6°C to 42°C and ‐ 100°C using the single‐photon‐timing technique. By global analysisofthe data we found four contributing lifetime components at the higher temperatures (T1' 12 ps,T1= 35 ps,T3' 65 ps,T4' 1000 ps). We attributeT1to an energy transfer between two pigment pools,T2to the charge separation process in the reaction center, componentT3is assigned to aggregate andT4to uncoupled chlorophyll emission. The corresponding decay‐associated spectra are presented. We also applied a target analysis procedure to fit parameters of a kinetic model directly to the data. The resulting rate constants and species‐associated spectra are discussed. The data indicate substantial spectral heterogeneity in the antenna with at least three substantially different chlorophyll pools. The overall exciton decay kinetics (by charge separation) is trap‐limited.
OPTICAL PROPERTIES OF EXPERIMENTAL PROSTATE TUMORS in vivo
Authors: Arnfield M. R. , Chapman J. D. , Tulip J. , Fenning M. C. , McPhee M. S.
Published: January 2008

The optical properties of tumor tissue provide important information for optimizing treatment plans in photodynamic therapy, especially when intertitial application by multiple fibers is planned. Near infrared light, required to activate novel photosensitizers, should facilitate improved light penetrance of tumor tissue compared with 630 nm light used for activating Photofrin II. We have measured light energy fluence rates for 630 and 789 nm light along radial tracks from a single laterally diffusing optical fiber centrally implanted into Dunning R3327‐AT and R3327‐H rat tracks from a single laterally diffusing optical fiber centrally implanted into Dunning R3327‐AT and R3327‐H rat prostate tumors in anesthetized rats. A total of 20 R3327‐AT and 10 R3327‐H tumors were used in this study with volumes from 2.6 to 13.3 cm3. Light track data were analyzed by an empirical model that described light attenuation. At 630 nm, light attenuation coefficients (LAC) were T1.9 × higher than those at 789 nm for both tumors with the well‐differentiated, well‐perfused tumor (R3327‐H) attenuating to a greater extent than did the rapidly growing anaplastic tumor (R3327‐AT). The intertumor variation of LAC was greater than the spatial variations observed within individual tumors. LAC were a function of tumor volume for only 630 nm light in the R3327‐AT tumors.
IS ZEAXANTHIN CAPABLE OF ENERGY TRANSFER TO CHLOROPHYLL a IN PARTIALLY GREENED LEAVES? A STUDY OF FLUORESCENCE EXCITATION SPECTRA DURING VIOLAXANTHIN DEEPOXIDATION
Authors: Pfündel Erhard E.
Published: January 2008

Absorbance spectra and excitation spectra of chlorophyll a fluoresence were recorded during the light‐induced deepoxidation of violaxauthin to zeaxanthin in bean leaves (Phaseolus coccineus) greened under intermittent light. Light minus dark fluorescence excitation difference spectra showed distinct minima at 440, 465, and 500 nm corresponding to maxima in the absorbance difference spectra. Both difference spectra were prevented by the deepoxidase inhibitor dithiothreitol and were inverted when zeaxanthin was epoxidized. The fluorescence excitation difference spectra were successfully modeled by considering the absorbance differences between violaxanthin and zeaxanthin, assuming no energy transfer from the two pigments to chlorophyll a, and accounting for light‐induced scattering changes. The pigment stoichiometry and the scattering changes of the simulation were in accordance with experimental data. The results indicate that, in the early stage of leaf development, light absorbed by the cycle pigments violaxanthin and zeaxanthin is not transferred to chlorophyll.
HYDROGEN PEROXIDE‐DEPENDENT GENERATION OF SINGLET MOLECULAR OXYGEN BY HUMAN SALIVA: ITS DETECTION BY CHEMILUMINESCENCE FROM ACypridinaLUCIFERIN ANALOG
Authors: Takahama Umeo
Published: January 2008

By the addition of hydrogen peroxide to human saliva, chemiluminescence fromCypridinaluciferin analog (CCLA) and oxygen evolution were observed. Chemiluminescence was inhibited by inhibitors of salivary peroxidase, azide and cyanide and by a singlet oxygen quencher, crocin. Deuterium oxide (99.75%) stimulated the initial increase of CCLA by15–50% and the integrated CCLA 2.1‐3.6‐fold. The result suggest that the generation of singlet oxygen by peroxidase in human saliva depends on hydrogen peroxide.
A FLUOROGENIC ACTINOMETER FOR NUCLEIC ACID PHOTOCHEMISTRY UTILIZING 1‐DEAZAPURINE N(3)‐OXIDES
Authors: Blaney Ruth , Al‐Nakib Tahsin , Davies R. Jeremy H.
Published: January 2008

A convenient and very sensitive actinometery system for UV radiation with wavelengths in the range250–310 nm is described, which is based on the fluorogenic photorearrangement of 1‐deazapurine N(3)‐oxide. The product, 1‐deazapruin‐2‐one, can be estimated fluoremetrically in the presence of the N‐oxide of 1‐deazapurine and 1‐methyl‐1‐deazapurine fail in the range 0.13‐0.15 and do not vary significantly with wavelength. There is potential for using 1‐deazupurine N(3)‐oxides as UV‐photoactivable fluorophores.
PHOTODYNAMIC KILLING OF Dictyostelium discoideum AMOEBAE MEDIATED BY 4′,5′‐DIIODOFLUORESCEIN ISOTHIOCYANATE DEXTRAN. A STRATEGY FOR THE ISOLATION OF THERMOCONDITIONAL ENDOCYTOSIS MUTANTS
Authors: Labrousse Arnaud , Satre Michel
Published: January 2008

4′, 5′‐Diiodofluorescein dextran has been synthesized by iodination of fluorescein dextran and it was used as a sensitizer in photodynamic killing of amoebae of the cellular slime mold Dictyostelium discoideum. Amoebae from axenic strain AX2 incubated in the presence of 4′,5′‐diiodofluorescein dextran efficiently internalized the molecule by fluid‐phase pinocytosis. Subsequently, illumination of cells showed dose‐ and time‐dependent loss of viability. The tertiary amine, 2,4‐ diaza[2,2,2]bicyclooctane, significantly decreased phototoxicity, whereas the presence of D2O increased phototoxicity. These effects were fully consistent with a role for excited‐state singlet oxygen generated inside the endosomal compartments in the mechanism of photoinjury. A strategy was developed to enrich for temperature‐sensitive Dictyostelium endocytosis mutants in a nitrosoguanidine mutagenized population. Incubation with 4′,5′‐diiodofluorescein dextran at 27°C to load endosomal compartments was followed by light treatment to kill parent‐type cells selectively. In contrast, mutants unable to internalize the fluid‐phase marker would survive the treatment. Six temperature‐sensitive clones were selected that grew normally at 21°C but did not grow at 27°C. They all showed markedly decreased fluid‐phase pinocytosis capacity at nonpermissive temperature as compared to their activity at 21 °C. These mutant strains should be useful in studies designed to characterize endocytosis mechanisms in Dictyostelium.
RELAXATION OF SUPERCOILED DNA BY AMINOMETHYL TRIMETHYLPSORALEN AND UV PHOTONS: ACTION SPECTRUM
Authors: Oroskar Asha A. , Gasparro Francis P. , Peak Meyrick J.
Published: January 2008

Abstract— An action spectrum of the relaxation of supercoied plasmid DNA(induction fo the firt single‐strand break) by photoactivated 4′‐aminomethyl‐4, 5′,8‐trimethylpsoralen(AMT) has been determined using monochormatic UV photons from 254 to 405 nm. The spectrum of AMT‐induced plasmid DNA relaxation fits closely with the absorbance spectrum of AMT in the spectral region between 313 nm and 405nm but deviates at wavelengths shorter than 313nm. This asay also reveals that the psoralen photosensitization reaction with DNA also produces piperidinelabile sites. Addition of mannitol and azide partially quenches the supercoil realaxation reaction, evidence for a role of Type II photosensitization pathway.
EARLY CELL KINETIC EFECTS OF A SINGLE DOSE OF NARROW‐BANDED ULTRAVIOLET B IRRADIATION ON THE RAT CORNEAL EPITHELUM
Authors: Haskjold Erling , Olsen WencheMarie , Bjerkens Rolf , Kravik Katherine
Published: January 2008

Abstract— The right eyes of 40 rats were exposed to a signal erythemogenic dose fo ultraviolet B irradiation (UVB) at 297nm. The irradiation was directed perpenddicualr to the center of the cornea. The left eyes served as controls. The animals were randomly assigned into 10 groups. The labelling index (LI) after pluse labeling the tritiated thymidine and the mitotic rate (MR) after Colcemid administration were registered in the corneal epithelium at predetermined intervals up to 96 h after the irradiation. A mathematical method was used to corealted corresponding corneal areas from the different animals. In the central the LI was considerably reduced up to 36h after the irradiation. The LI increased toward the peripheral cornea and reached normal values at the limbal area. The MR was also reduced up to 36h. However, this reduction was over the entire epithelium. The block in cell proliferation was followed by increased proliferation.
COPPER BENZOCHLORIN, A NOVEL PHOTOSENSITIZER FOR PHOTODYNAMIC THERAPY: EFFECTS ON A TRANSPLANTABLE UROTHELIAL TUMOR
Authors: Selman Steven H. , Hampton James A. , Morgan Alan R. , Keck Rick W. , Balkany AdamD. , Skalkos Dimitris
Published: January 2008

Abstract— An iminum salt of octaethylbenzochlorin with copper in the aromatic ring, CDSI, was tested for its tumoricidal effects on theA–27 N‐[4‐(5‐notro‐2‐furyl)‐2‐thiazoly] formamide tumor line. CDSI was found to be an effective photosensitiz4r in vivo when used in combination with either a xenon arc lamp or a pulsed alexandrite laser. Hemodynamically, CDSI and light caused a rapid decrease in tumor blood flow. skin photosensitization was found to be minimal when drug‐injected mice werwe illuminated in a solar simulator.
ACTION SPECTRA OF THE PHOTOPHOBIC RESPONSE OF BLUE AND RED FORMS OF Blepharisma japonicum
Authors: Checcucci Giovanni , Damato Giuseppe , Ghetti Francesco , Lenci Francesco
Published: January 2008

Abstract— When exposed, in the presence of molecular oxygen, to light intensities of the order of3–30 W m‐2, the ciliate Blepharisma japonicum changes its color from red to blue, because of the photooxidation of the photoreceptor pigment, blepharismin, to pxyblepharismin. Both red‐and blue‐pigmnentes cells show step‐up photophobic responses. The action spectra f the light‐dependent behaviour of the red and the blue form of Blepharisma have been determined; their structure is very similar to that the photosensing and phototransducing properties of blepharismin are maintained in its photooxidized form. oxyblepharismin.