bluuebunny/crossref_metadata_2025 huggingface dataset:
REPAIR OF NEAR‐VISIBLE‐ and BLUE‐LIGHT‐INDUCED DNA SINGLE‐STRAND BREAKS BY THE CHO CELL LINES AA8 and EM9
Authors: Churchill Mark E. , Peak Jennifer G. , Peak Meyrick J.
Published: January 2008

The induction of single‐strand breaks (SSB) and the kinetics of SSB repair were measured in two Chinese hamster ovary cell lines irradiated with monochromatic photons of near‐visible radiation (405 nm) and blue light (434 nm). The radiosensitive and UV‐A‐sensitive mutant line EM9 is known to repair SSB induced by ionizing radiation or 365‐nm UV‐A more slowly than the parent line AA8. At the 10% survival level, EM9 cells were 1.7‐ and 1.6‐fold more sensitive than AA8 cells to 405 and 434 nm radiation, respectively. This sensitivity was not due to differences in induction of SSB because AA8 and EM9 cells accumulated the same number of initial breaks when irradiated at 0.5°C with either 405 nm (5.9 SSB per MJ/m2) or 434 nm (5.1 SSB per MJ/m2), as measured by alkaline elution. When the cells repaired these SSB at 37°C in full culture medium, biphasic repair kinetics were observed for both cell lines. In both phases of repair, EM9 cells repaired breaks induced by both wavelengths more slowly than did AA8 cells. The 1½ values for the repair phases for 405‐nm‐induced SSB were 3.8 and 150 min for EM9, and 1.5 and 52 min for AA8; the corresponding values for repair of 434 nm breaks were 3.7 and 39 min for EM9, and 2.0 and 30 min for AA8. Because of this slower repair, EM9 cells left more SSB unrepaired after 90 min than did AA8 cells for both wavelengths. The ratio of unrepaired breaks in EM9 cells to that in AA8 cells was 1.4 and 1.7 times higher for 405 and 434 nm radiation, respectively. Thus, the sensitivity of EM9 cells to near‐visible and visible light correlates with a deficiency in repairing SSB induced by these wavelengths. These results suggest that DNA damage may be a critical event in visible‐light‐induced cellular lethality and that an important determinant of the ability of AA8 and EM9 cells to survive visible light irradiation may be their ability to repair DNA strand breaks.
INACTIVATION ACTION SPECTRA OF BACILLUS SUBTILIS SPORES IN EXTENDED ULTRAVIOLET WAVELENGTHS (50–300nm) OBTAINED WITH SYNCHROTRON RADIATION
Authors: Munakata Nobuo , Saito Mikio , Hieda Kotaro
Published: January 2008

Five types of Bacillus subtilis spores (UVR, UVS, UVP, RCE, and RCF) differing in repair and/or recombinational capabilities were exposed to monochromatic radiations at 13 wavelengths from 50 to 300 nm in vacuum. An improved biological irradiation system connected to a synchrotron radiation source was used to produce monochromatic UV radiation in this extended wavelength range with sufficient fluence to inactivate bacterial spores. From the survival curves obtained, the action spectra for the inactivation of the spores were depicted. Recombination‐deficient RCE (recE) and RCF (recF) spores were more sensitive than the wild‐type UVR spores in the entire range of wavelengths. This was considered to mean that DNA was the major target for the inactivation of the spores. Vacuum‐UV radiations of125–175 nm were effective in killing the spores, and distinct peaks of the sensitivity were seen with all types of the spores. Insensitivities at 190 and 100 nm were common to all five types of spores, indicating that these wavelengths were particularly impenetrant and absorbed by the outer layer materials. The vacuum‐UV peaks centering at 150 nm were prominent in the spores defective in recombinational repair, while the far‐UV peaks at around 235 and 270 nm were prominent in the UVS (uvrA ssp) and UVP (uvrA ssp polA) spores deficient in removal mechanisms of spore photoproducts. Thus, the profiles of the action spectra were explained by three factors; the penetration depth of each radiation in a spore, the efficiency of producing DNA damage that could cause inactivation, and the repair capacity of each type of spore.
SPECTROSCOPIC STUDIES ON THE STRUCTURES OF RETINOCHROME and METARETINOCHROME*
Authors: Kishigami Akio , Sekiya Noriko , Yoshihara Kazuo , Hara Reiko , Hara Tomiyuki , Tokunaga Fumio
Published: January 2008

Abstract– Spectroscopic measurements of retinochrome and the related photoproduct, metaretino‐chrome, were carried out to determine the conformation of the retinal and the protein. Absorption spectra with fourth derivatives indicate that the tryptophan residues are located in a hydrophobic core and that the environment around these residues does not change after light irradiation. Circular dichroism measurements indicate that retinochrome has a high helical content which is not altered by the conversion of retinochrome to metaretinochrome. Fourier transform infrared difference spectra demonstrate that retinochrome has the all‐trans retinal and metaretinochrome has the 11‐CM retinal. Retinochrome has an absorption due to amino acid residue(s) which changes in metaretinochrome. This work demonstrates that conformational changes are not induced during the conversion but the electrical charge(s) of the protein are changed by irradiation.
THE SENSORY PHOTORECEPTORS OF Halobacterium halobium REVISITED: ACTION SPECTRA and INFLUENCE OF BACKGROUND LIGHT*
Authors: Hildebrand Eilo , Schimz Angelika
Published: January 2008

Abstract–Action spectra of the light‐dependent behavior ofHalobacteriumand the effect of background light have been measured with regard to the current hypothesis of Spudich and Bogomolni [Nature312,509–513 (1984)], which proposes sensory rhodopsinI(sRI587) to be the receptor for long‐wavelength light, and its photoproduct S373to be the receptor for UV light. The action spectrum shows three maxima for attractant responses (prolonged swimming intervals) at 565, 590, and 610 nm, and two maxima for repellent responses (shortened intervals) at 370 and 480 nm. The latter is assigned to sensory rhodopsin II (P‐480). All peaks are red‐shifted after substitution of the endogeneous retinal by 3, 4‐dehydroretinal. The peaks at 590 and 610 nm are suppressed by long‐wavelength background light. Ultraviolet background light converts all attractant peaks into repellent peaks. The response at 370 nm is strongly activated by visible background light, the maximal effect occurring with 510 nm. The activated state declines with a half‐life of about 1.2 s. In a growing culture, full sensitivity to UV and blue light is restored about 10 h earlier than sensitivity to long‐wavelength light. Some of the results cannot easily be explained by the sRI587/S373hypothesis. Explanations for the three maxima in the long‐wavelength range and for the maximal activation of the UV response by 510 nm light are discussed.
SULFONATED PHTHALIMIDOMETHYL ALUMINUM PHTHALOCYANINE: THE EFFECT OF HYDROPHOBIC SUBSTITUENTS ON THEin vitroPHOTOTOXICITY OF PHTHALOCYANINES
Authors: PAQUETTE BENOIT , BOYLE ROSS W. , ALI HASRAT , MACLENNAN ALEXANDER H. , TRUSCOTT T. GEORGE , VAN LIER JOHAN E.
Published: January 2008

Abstract—

The photocytotoxicity of sulfonated phthalimidomethyl aluminum phthalocyanine, a more hydrophobic photosensitizer as compared to phthalocyanine substituted with sulfonate groups only, was investigated. Inclusion of 1–2 phthalimidomethyl groups into disulfonated aluminum phthalocyanine, resulted in increased partition coefficients betweenn‐octanol and water, and a six‐fold increase in both cellular uptake and photocytotoxicity towards Chinese hamster lung fibroblast cells (line V‐79). Reducing the number of phthalimidomethyl groups, or increasing the degree of sulfonation, lead to a decrease in the partition coefficient, cellular uptake, and phototoxicity. The quantum yield of singlet oxygen was comparable for all dyes tested in this series, indicating that no significant change in this photophysical parameter resulted from phthalimidomethylation. These results suggest that the addition of 1–2 phthalimidomethyl groups to disulfonated aluminum phthalocyanine improves cellular uptake, but, as the relative efficiency of cell killing was not effected, the intracellular distribution on photosensitive molecules may not be modified.
RESONANCE RAMAN SPECTRA OF BACTERIORHODOPSIN MUTANTS WITH SUBSTITUTIONS AT ASP‐85, ASP‐96, AND ARG‐82
Authors: LIN STEVEN W. , FODOR STEPHEN P. A. , MIERCKE LARRY J. W. , SHAND RICHARD F. , BETLACH MARY C. , STROUD ROBERT M. , MATHIES RICHARD A.
Published: January 2008

Abstract—

Detergent solubilized bacteriorhodopsin (BR) proteins which contain alterations made by site‐directed mutagenesis (Asp‐96→Asn, D96N; Asp‐85→Asn, D85N; and Arg‐82→Gln, R82Q) have been studied with resonance Raman spectroscopy. Raman spectra of the light‐adapted (BRLA) and M species in D96N are identical to those of native BR, indicating that this residue is not located near the chromophore. The BRLA states of D85N and especially R82Q contain more of the 13‐cis, C=N syn (BR555) species under ambient illumination compared to solubilized native BR. Replacement of Asp‐85 with Asn causes a 25 nm red‐shift of the absorption maximum and a frequency decrease in both the ethylenic (‐7 cm−1) and the Schiff base C=NH+ (‐3 cm−1) stretching modes of BRLA. These changes indicate that Asp‐85 is located close to the protonated retinal Schiff base. The BRLA spectrum of R82Q exhibits a slight perturbation of the C=NH+ band, but its M spectrum is unperturbed. The Raman spectra and the absorption properties of D85N and R82Q suggest that the protein counterion environment involves the residues Asp‐85−, Arg‐82+ and presumably Asp‐212−. These data are consistent with a model where the strength of the protein‐chromophore interaction and hence the absorption maximum depends on the overall charge of the Schiff base counterion environment.
ELECTROSTATIC EFFECTS IN THE PHOTOREDUCTION OF FLAVINS BY EDTA
Authors: MOORE WILLIAM M. , FIFE DENNIS J. , GRABNER MARY JO , WHYTE GRACE I.
Published: January 2008

Abstract—

The anaerobic photoreduction of riboflavin, flavin mononucleotide, N(3)‐carboxymethylriboflavin, N(3)‐methyl‐lumiflavin, and lumiflavin by EDTA was studied in aqueous solution over the pH range 2.5–10. The electrostatic effects of the electron donor‐acceptor pair produce a secondary effect on the reactivity, and this effect can be predicted from the product of the charges (ZD x ZA). The trianonic and tetraanonic species of EDTA have nitrogens which are free from intramolecular hydrogen bonding, and these species are potentially the most reactive. However, in some pH regions the electrostatic effect can become the dominant factor when both the electron donor and acceptor become negatively charged. The excited states of flavins are susceptible to charge effects whether the charge is localized on the side chain or involves the isoalloxazine ring system.
SPECIES DIFFERENCES IN RESPONSE TO PHOTOHEMOLYTIC AGENTS
Authors: ROBERTSON DONALD G. , BAILEY DEBRA L. , MARTIN RONALD A.
Published: January 2008

Abstract—

Species differences in red blood cell susceptibility to the photohemolytic agents chlorpromazine, menadione and tetracycline were examined in mouse, rat, dog, and human blood. Menadione and tetracycline (25 μM) hemolyzed mouse but not dog, rat, or human red blood cells (RBC) when irradiated with UV light but not in the dark. Chlorpromazine (25 μM) produced a photohemolytic response in all four species with mouse and rat RBC lysing fastest followed by human then dog cells. Investigations into the nature of these species differences suggested that the size of mouse RBC may contribute to its high sensitivity to photohemolytic agents. An investigation of the effect of UV light on key antioxidant enzymes revealed species differences in enzyme inactivation. These data suggest that mouse RBC may be particularly vulnerable to phototoxic agents, especially those compounds which produce active oxygen species and, therefore, may prove more useful than human RBC as a model for predicting phototoxic potential of some chemical entities.
AN ELECTRON SPIN RESONANCE STUDY OF MEROCYANINE 540‐MEDIATED TYPE I REACTIONS IN LIPOSOMES
Authors: FEIX JIM B. , KALYANARAMAN B.
Published: January 2008

Abstract— The merocyanine 540 (MC540)‐mediated reduction of nitroxide spin labels in a liposomal system was examined using electron spin resonance (ESR) spectroscopy. Spin label reduction was light driven, and occurred in liposomes composed of both fully‐saturated (dimyristoyl) and mono‐unsaturated (1‐palmtoyl‐2‐oleoyl) phosphatidylcholine. Loss of the nitroxide ESR signal was enhanced by the physiological electron donors glutathione, cysteine, and NADPH; and was strongly inhibited by the presence of molecular oxygen. Nitroxides reduced in the presence of MC540 alone could be regenerated either by purging the sample with air or by the addition of ferricyanide, indicating that the ESR signal loss was due to reduction to the corresponding hydroxylamines. Only partial regeneration was attained for nitroxides reduced in the presence of glutathione, cysteine, or NADPH. Reduction rates for the lipophilic spin labels, 5‐, 12‐, and 16‐doxyl stearic acid, were not influenced by the position of the nitroxide moiety along the alkyl chain, however reduction of spin labels occupying primarily the aqueous phase was much slower. These studies demonstrate that MC540 can initiate oxidation/reduction (Type I) reactions. Such Type I processes may augment the effects of singlet oxygen in MC540‐mediated photodynamic therapy.
In vivo SPECTROPHOTOMETRIC EVALUATION OF NEOPLASTIC AND NON‐NEOPLASTIC SKIN PIGMENTED LESIONS–I. REFLECTANCE MEASUREMENTS
Authors: MARCHESINI RENATO , BRAMBILLA MARCO , CLEMENTE CLAUDIO , MANIEZZO MASSIMO , SICHIROLLO ADELE E. , TESTORI ALESSANDRO , VENTUROLI DANIELE R. , CASCINELLI NATALE
Published: January 2008

Abstract— Reflectance spectrophotometry from 400 to 800 nm on different cutaneous pigmented lesions, including primary and metastatic malignant melanoma, pigmented nevi, lentigo and seborrhoeic keratosis, has been performed by using an external integrating sphere coupled to a spectrophotometer. Measurements show that reflectance spectra of the different lesions manifest dissimilar patterns, particularly in the near IR region. Comparison of reflectance of nevi with that of malignant melanomas results in a highly significant difference (P < 10‐6) between the two samples. Though interpretation of the specta remains difficult as a result of the complexity of the optical processes of scattering and absorption, our results suggest that a detailed analysis of the reflectance spectrum may give clinically useful information, and could be utilized as an aid in clinical diagnosis of cutaneous pigmented lesions, especially where malignant melanoma is concerned.
THE PHOTOREACTION OF A RHODAMINE 6G MONOLAYER ADSORBED ON QUARTZ STUDIED BY SURFACE SECOND HARMONIC GENERATION
Authors: MEECH STEPHEN R. , YOSHIHARA KEITARO
Published: January 2008

Abstract— A monolayer of rhodamine 6G on quartz in air exhibited photochemistry upon laser irradiation in the first absorption band. The course of the reaction was followed in real time by the surface second harmonic generation method. It was observed that the photoproduct had an enhanced non‐linear coefficient, relative to rhodamine 6G. Absorption spectra showed that this was not a result of a stronger resonance enhancement of the signal by the photoproduct. Consideration of the factors to which the surface second harmonic signal is sensitive suggested that the enhancement arose from an increased charge transfer character of the photoproduct's electronic transitions, and a reorientation of its transition dipole.
INTER AND INTRAMOLECULAR INTERACTIONS OF PORPHYRINS WITH 5,5′‐DITHIOBIS(2‐NITROBENZOIC ACID)
Authors: D'Souza Francis , Krishnan V.
Published: January 2008

Abstract—

meso‐Tetraphenylporphyrin and its metal [zinc(II) and copper(II)] derivatives form both inter and intramolecular complexes with 5,5′‐dithiobis(2‐nitrobenzoic acid) (DTNB). The nature of interaction is predominantly charge transfer (CT) in origin, with the porphyrin functioning as a II‐donor and DTNB as an acceptor. Among the covalently linked intramolecular systems, the magnitude of CT interaction varies with the position (of one of the aryl groups of the porphyrin) to which DTNB is attached as ortho meta > para. Steady‐state and time‐resolved fluorescence studies revealed electron transfer to be the dominant pathway for the fluorescence quenching in these systems. Steady‐state photolysis experiments probed using EPR and optical absorption studies have shown that electron transfer (from the excited singlet state of the porphyrin) to DTNB results in the formation of thiyl radical and production of free thiolate anion. It is found that the products of electrochemical reduction of covalently linked porphyrin‐DTNB systems are different from those observed for the photochemical studies.
ACTION SPECTRA OF PHTHALOCYANINES WITH RESPECT TO PHOTOSENSITIZATION OF CELLS
Authors: Moan Johan , Berg Kristian , Bommer Jerry C. , Western Andre
Published: January 2008

Abstract—

Human carcinoma cells (NHIK 3025 cells) and Chinese hamster cells (V79 cells) were incubated with AIPcS1, AIPcS2and AIPcS4, phthalocyanines with different lipophilicity but with similar photochemical properties when in monomeric solutions. The absorption‐ and fluorescence spectra of the dyes in the cells were recorded as well as their action spectra with respect to sensitizing cells to photoinactivation. These spectra show that under the present conditions AIPcS1is strongly aggregated in both cell lines; AIPcS2is aggregated in V79 cells but much less so in NHIK 3025 cells. A main finding is that the shapes of the action spectra are similar to that of the fluorescence excitation spectra, but not to the absorption spectra, indicating that the photosensitizing effects of the dyes are mainly due to their monomeric fraction in the cells. AIPcS2and AIPcS4localize intracellularly mainly in lysosomes while AIPcS1was found to be more diffusely distributed in cells. As measured per quantum of fluorescence emitted, AIPcS2and AIPcS2are more efficient sensitizers than AIPcS4. The difference in efficiency between AIPcS2and AIPcS4is supposedly due to a different localization pattern on the suborganelle level.
INFLUENCE OF DIETARY OMEGA‐6, ‐3 FATTY ACID SOURCES ON THE INITIATION AND PROMOTION STAGES OF PHOTOCARCINOGENESIS
Authors: Black Homer S. , Thornby John I. , Gerguis Janette , Lenger Wanda
Published: January 2008

Abstract—

To determine the segment along the carcinogenic continuum at which dietary lipid exerts its principal effect, six groups of 35 Skh‐HR‐1 hairless mice were placed on defined isocaloric diets containing either 0.75%, 12% corn oil or 12% menhaden oil as sources of omega‐6 or omega‐3 fatty acids, respectively. All animals received an 11 week course of UV‐radiation from fluorescent sunlamps. Upon termination of UV, diets of some groups were crossed‐over to either low fat, high fat, omega‐6 or omega‐3 fatty acid sources. The first tumor appeared at week 14. Life‐table analysis of the tumor incidence curves and Wilcoxon tests of tumor multiplicity provided evidence that high corn oil diets significantly (P < 0.01) enhance carcinogenic expression; that tumor enhancement by the omega‐6 fatty acid source occurs during the post‐initiation, or promotion, stage; that replacement with a low corn oil diet after UV‐initiation will negate the exacerbating effect of high corn oil; and that an omega‐3 fatty acid source inhibits UV‐carcinogenesis even at high dietary levels, although not during the post‐initiation stage.
THE PHOTOTOXICITY OF 8‐M‐ETHOXYTHIONEPSORALEN AND 6‐M‐ETHYLTHIONECOUMARIN
Authors: Tuveson R. W. , Wang Gui‐Rong , Becker Ralph S.
Published: January 2008

Abstract—

The phototoxicity of 8‐m‐ethoxythionepsoralen (8‐M‐OTP) and 6‐m‐ethylthione coumarin (6‐M‐TC) when activated by UV‐A has been investigated using a variety of Escherichia coli strains, Haemophilus influenme transforming DNA and Escherichia coli pBR322 plasmid DNA. The results demonstrate that 8‐M‐OTP is a strictly oxygen independent photosensitizer that is about 500‐f‐old less efficient in forming lesions leading to equivalent lethality than is the parent compound from which it is derived (8‐M‐OP). As is true for 8MOP, 8‐M‐OTP is capable of inducing histidine independent mutations in E. coli and inactivating transforming DNA consistent with DNA being a target for lesions induced by this molecule in the presence of UV‐A. 6‐M‐TC is a strongly oxygen dependent photosensitizer activated by UV‐A when tested with either E. coli cells or transforming DNA in contrast to the parent compound (6‐m‐ethylcoumarin; 6‐M‐C) which is not phototoxic when treated with UV‐A. These results imply that the membrane may be an important target leading to lethality. 6‐M‐TC in the presence of UV‐A can inactivate pBR322 plasmid and Haemophilus influenme transforming DNA activity in virro suggesting that DNA is a potential target for this molecule when activated by UV‐A.
POTENTIATION OF OXIDATIVE DAMAGE TO PROTEINS BY ULTRAVIOLET‐A AND PROTECTION BY ANTIOXIDANTS
Authors: Hu Miao‐Lin , Tappel Al L.
Published: January 2008

Abstract—

We have studied the damage of alcohol dehydrogenase (ADH) and glyceraldehyde 3‐p‐hosphate dehydrogenase (GAPD) induced by Fe++/EDTA + H2O2 in combination with UV‐A (main output at 365 nm). Enzyme inactivation, formation of hydroxyl radicals (measured in the absence of enzymes), increase in protein carbonyls, oxidation of sulfhydryl (SH) groups, loss of native protein fluorescence, and enhanced protease degradation were used to determine protein damage. Hydroxyl radical production was greatly enhanced by the combination of UV‐A with Fe++/EDTA + H2O2. The combined treatment increased protein carbonyls but decreased native protein fluorescence and SH groups. The combined treatment caused turbidity in GAPD but not in ADH, whereas trypsin susceptibility was increased more in ADH than in GAPD. These measurements of protein oxidation correlated well with enzyme activities. Glyceraldehyde 3‐p‐hosphate dehydrogenase and dithiothreitol were most protective against such damage, while hydroxyl radical and singlet oxygen scavengers were partially effective. Superoxide dismutase had no effect. Thus, UV‐A potentiation of protein damage induced by FE++/EDTA + H2O2 appeared to involve hydroxyl radicals and perhaps singlet oxygen but not superoxide radicals. The damage to proteins induced by combination of UV‐A with physiological oxidants, iron ions and HzO2 may be relevant to UV‐A‐induced skin and tissue damage.
INACTIVATION OF LAMBDA PHAGE WITH 658 nm LIGHT USING A DNA BINDING PORPHYRIN SENSITIZER
Authors: Kasturi Chandrika , Platz Matthew S.
Published: January 2008

Abstract—

Exposure of lambda phage to 658 nm light in the presence of 5,10,15,20‐tetrakis‐(1‐methyl‐4‐pyridyl)‐21H,23H‐prphine, tetra‐p‐tosylate leads to complete (< 7 logs) inactivation as measured by the plaque assay. The sensitizer without light and 658 nm photolysis of lambda phage in the absence of sensitizer do not lead to a measurable decrease in viral inactivity. Viral inactivation is not dependent upon the presence of oxygen.
SPECTRAL QUALITY OF TWO FLUORESCENT UV SOURCES DURING LONG‐TERM USE
Authors: Adamse Paulien , Britz Steven J.
Published: January 2008

Abstract—

The characteristics of a fluorescent ultraviolet (UV) lamp (UVB‐313), UV‐B transmitting cellulose diacetate (CA) and UV‐B absorbing polyester (PE) films were determined during actual use. Although lamp emission was stable between 70 and 386 h of burn time (longer times were not investigated), the absorbance of UV‐B and UV‐A radiation by CA and PE films, respectively, increased with time when wrapped around lamps. As a result, the irradiance of lamp/filter combinations decreased steadily (even when CA films were presolarized for 10 h), making it necessary to compensate by adjusting the height of the lamp bank or by changing filters frequently. Note that corrective action is required for UV‐A controls (PE films) as well as UV‐B experimental treatments (CA films). Changing filters is preferable, since aging of CA filters caused shifts in the ratio of UV‐B to UV‐A. However, in spite of these shifts, the normalized spectrum of weighted biologically effective UV‐B radiation did not change to a large extent.
RAPID STOMATAL RESPONSE TO RED LIGHT IN Zea mays
Authors: Assma Sarah M. , Lee David M. , Malkus Per
Published: January 2008

Abstract—

Gas exchange techniques were employed to study responses of stomatal conductance to pulses of red and blue light in the grass, Zea mays. Zea mays exhibited conductance increases following brief (< 1 min) pulses of either red or blue light, in contrast to other species (e.g. Commelina communis; Assmann, 1988, Plant Physiol. 87, 226–231) that exhibit consistent conductance responses only to pulses of blue light. Red light pulses of 450 μmol m−2s−1 for x min or 225 μmol m−2s−1 for 2x min were used to probe the fluence dependence of the red light response. The red light‐stimulated conductance increase was constant for a given fluence, and increased with increasing total fluence. The conductance response to red light was larger in field grown plants (maximum growth irradiance ˜ 1600 μmol m‐2s−l) than in plants raised in growth chambers (maximum growth irradiance ˜ 150 μmol m−2s−1).
PHOTOCHEMISTRY ON SURFACES. EXCITED STATE BEHAVIOR OF RUTHENIUM TRIS(BATHOPHENANTHROLINE DISULFONATE) ON COLLOIDAL ALUMINA‐COATED SILICA PARTICLES*
Authors: Kamat Prashant V. , Ford William E.
Published: January 2008

Abstract— The excited state behavior of an anionic ruthenium(II) complex, RuL34‐(L=bathophen‐anthroline disulfonate), that is electrostatically bound to positively charged alumina‐coated silica particles is investigated. The apparent association constant for the binding of RuL34‐to the particles is 1.2 × 104M‐1. Surface photochemical processes result in decreased emission yields and multiexponential excited state decay. Excited state quenching by ground‐state molecules is evident at high surface coverages. The non‐exponential decay kinetics observed at low surface coverages can be attributed either to clustering of the RuL34‐molecules or photoionization promoted by Lewis acid sites on the particle surface.
CELL DENSITY DEPENDENCE OF ULTRAVIOLET LIGHT ENHANCED REACTIVATION OF Herpes simplex TYPE I AND THE LARGE PLAQUE EFFECT IN C3H/10T1/2 MOUSE FIBROBLASTS
Authors: Montes J. G. , Taylor W. D.
Published: January 2008

Abstract— C3H/10T1/2 mouse fibroblasts were grown to different cell densities either by plating at low density and allowing different growth periods, or by plating at a series of increasing densities and allowing the same growth period. These plates were UV irradiated at 7.5 J/m2 or mock irradiated and 24 h later infected with UV‐irradiated Herpes simplex type I virus which had been UV irradiated at 50 or 125 J/m2 or mock irradiated. The numbers and sizes of plaques were measured and these data used to calculate the extent of UV‐enhanced host cell reactivation, the capacity enhancement, the large plaque effect (LPE) and the small plaque effect (SME). The influence of cell density on these phenomena was similar for both series of density experiments. Ultraviolet‐enhanced host cell reactivation could be demonstrated only for cultures of lower density. The capacity of the cells for Herpes simplex type I virus decreased with cell density, but UV irradiated cells showed an increase in capacity with cell density. Plaque sizes decreased in all cases with cell density but the LPE and SPE were not significantly altered. The greatest variation in the above parameters occurred just as the cells were approaching confluence, where most host cell reactivation experiments are carried out. We conclude that the reproducibility of such experiments depends critically on cell density, a dependence which may be relevant to mechanistic interpretations of the UV‐dependent phenomena.
A BLUE FLUORESCENT PROTEIN FROM A YELLOW‐EMITTING LUMINOUS BACTERIUM
Authors: Karatani Hajime , Wilson Thérèse , Hastings J. Woodland
Published: January 2008

Abstract— Vibrio fischeri strain Y1 emits yellow light in vivo due to the participation of a yellow fluorescent protein (YFP) in the luciferase reaction. In this study it was found that the organism also produces a protein (referred to as Y1‐BFP) emitting strong blue fluorescence. Its molecular weight, about 25 kDa, is the same as or very close to that of YFP. The fluorescence excitation and emission maxima of the purified Y1‐BFP are at 416 and 461 nm, respectively, and the fluorescence lifetime is 12.5 ns at 2°C. The molar extinction coefficient of Y1‐BFP at 416 nm was estimated to be approx. 9500. With the homologous luciferase, Y1‐BFP decreases the intensity and rate of decay in the in vitro reaction but has no effect on its emission spectrum (in contrast to YFP, which has a striking effect on the spectrum). With luciferase isolated from Vibrio harveyi, however, Y1‐BFP causes a small blue‐shift (˜10 nm) in the emission of the enzyme catalyzed reaction, whereas YFP has no effect on the emission spectrum.
IDENTIFICATION AND CHARACTERIZATION OF THE MAJOR PHOTOADDUCTS FORMED BETWEEN 1‐PHENYL‐1,3,5‐HEPTATRIYNE AND UNDECYLENIC ACID METHYL ESTER
Authors: Lee Cheon Seok , Shim Sang Chul
Published: January 2008

Abstract—The near‐UV induced photoreactions of 1‐phenyl‐1,3,5‐heptatriyne (PHT) with undecylenic(10‐undecenoic) acid methyl ester (UAME) and 1‐hexene have been investigated in n‐hexane. Four major photoadducts have been isolated in both cases and purified by normal and reverse phase liquid chromatography. The structures of these adducts were determined by mass, UV absorption, FT‐IR,1H‐and13C‐NMR spectral analyses, one‐and two‐dimensional nuclear Overhauser effect studies, and1H‐1H homo‐correlation spectroscopy. All the data indicate that the adducts are cyclobutenes resulting from the [2+2] photocycloaddition of PHT to UAME and 1‐hexene.
QUENCHING OF SINGLET OXYGEN BY BIOMOLECULES FROM L1210 LEUKEMIA CELLS
Authors: Baker Ayse , Kanofsky Jeffrey R.
Published: January 2008

Abstract— Singlet oxygen lifetimes for detergent‐dispersed L1210 leukemia cells in deuterium oxide buffer were measured by following the decay of 1270 nm phosphorescence. Four photosensitizers and two detergents were studied. Stern‐Volmer plots were linear over the cell concentration range studied (0–107 cells/mL). The singlet‐oxygen quenching constants obtained depended somewhat upon the specific combination of detergent and photosensitizer used. Extrapolation of the singlet‐oxygen lifetime data to “100%” cell concentration (1.39 ± 0.04 × 109 cells/mL) and correction for the contribution of the water solvent gave a singlet‐oxygen lifetime between 0.17 and 0.32 us for the L1210 leukemia cell. The theoretical contributions of various types of biological molecules within the L1210 cell to the total singlet‐oxygen quenching were calculated from their concentrations and their quenching constants. These calculations suggest that proteins will quench most of the singlet‐oxygen. Only about 7% of the singlet‐oxygen is quenched by water.
PHOTODYNAMIC THERAPY OF CHEMICALLY‐ AND ULTRAVIOLET B RADIATION‐INDUCED MURINE SKIN PAPILLOMAS BY CHLOROALUMINUM PHTHALOCYANINE TETRASULFONATE
Authors: Agarwal Rajesh , Athar Mohammad , Elmets Craig A. , Bickers David R. , Mukhtar Hasan
Published: January 2008

Abstract— Photodynamic therapy (PDT) of cancer combines irradiation of tumors with visible light following selective uptake of the photosensitizer by the tumor cells. PhotofrinR‐II (Pf‐II) is the only photosensitizer which is in clinical use in PDT, whereas chloroaluminum phthalocyanine tetrasulfonate (AIPcTS) has also shown promise in preclinical studies. In most such studies, the effectiveness of the photosensitizers has been assessed in implanted tumor model systems rather than in model systems where tumors are allowed to grow in their own connective tissue matrix. In this study the pharmacoki‐netics, tumor ablation capability and cutaneous photosensitization response of AlPcTS have been assessed in mice bearing chemically‐ and ultraviolet B radiation (UVB)‐induced benign skin papillomas. When tumor‐bearing animals were injected intraperitoneally with AlPcTS (5 mg/kg body wt), maximum tumor:normal skin ratio of 2.4 was observed at 48 h, at which time the mice were irradiated within the absorption spectrum of the photosensitizer. In tumor ablation studies with SENCAR mice bearing chemically‐induced skin tumors, AlPcTS resulted in greater than 80% ablation in tumor volume at 20 days post‐irradiation. In cutaneous photosensitization response, AlPcTS produced only transient effects (no effect after 24 h) in SENCAR mice. Pharmacokinetics data, tumor ablation effects and cutaneous photosensitization response of AlPcTS were comparable in SKH‐1 hairless mice bearing UVB‐induced skin tumors. Our data indicate that AlPcTS produces significant photodynamic effects towards the ablation of murine skin tumors, and that it does not produce prolonged cutaneous photosensitivity.
NONPHOTOCHEMICAL HOLE BURNING OF THE B800‐B850 ANTENNA COMPLEX OF Rhodopseudomonas acidophila
Authors: Reddy N. R. S. , Cogdell R. J. , Zhao L. , Small G. J.
Published: January 2008

Detailed burn wavelength‐dependent hole‐burning studies of the title complex have been performed. The zero‐phonon hole (ZPH) widths for B800 at 4.2 K are 6.0 ± 0.3 cm and are discussed in terms of B80O‐B850 and B800‐B800 energy transfer. The B800* lifetime is 1.8 ± 0.2 ps. The site inhomogeneous broadening (r,) of B800 is 240 cm−1. The B850 (located at 864 nm at 4.2 K) hole spectra reveal that B850 suffers from significant homogeneous broadening, which is attributed to unit cell exciton level structure and ultrafast interexciton level relaxation. Novel ZPH action spectra lead to the resolution of a minor component at 885 nm, which is the analogue of B870 of Rhodobacter sphaeroides previously assigned as the lowest exciton level of the B850 exciton band. The B870 ZPH width of 2.0 ± 0.2 cm−1for Rhodopseudomonas acidophila leads to a total dephasing time of 5.3 ps, which is attributed to exciton scattering that stems from the energetic inequivalence of neighboring B850 unit cells.
ULTRAVIOLET RADIATION‐INDUCED PHOSPHOLIPASE A2 ACTIVATION OCCURS IN MAMMALIAN CELL MEMBRANE PREPARATIONS
Authors: Cohen Dianne , DeLeo Vincent A.
Published: January 2008

Ultraviolet erythema in human skin is mediated in part by membrane derivatives of arachidonic acid (AA). UVA (320–400nm) and UVB (290–320nm) have been shown to induce release of AA from intact mammalian cells in culture. In order to investigate the mechanism of this release we examined the effect of UVA and UVB on release of [3H] AA from membrane preparations of murine fibroblasts. C3H 10T1/2 cells were prelabelled for 24 h with [3H] AA. The membrane fractions of the cells were separated after lysis by differential centrifugation. The membranes were irradiated in suspension and the [3H] AA released from the membranes was determined by scintillation spectroscopy of supernatants3–4 h after irradiation. Both UVA and UVB induced release of AA from the membrane preparations. The response to UVB was small but significant, reaching levels approximately 150% of control release at doses of 1,200‐4,000 J/m2. The response to UVA was larger; doses of 2.5‐5.0 J/cm2 induced release equal to twice control (200%) levels, while doses of10–20 J/cm2 induced maximal release at levels approximately 400% of control. Time course studies with UVB and UVA showed maximal release at 4 h after irradiation. When the membrane preparations were incubated with a polyclonal anti‐phospholipase A2 antibody the UV induced release of [3H] AA was completely inhibited in both UVB (1200 J/m2) and UVA (10 J/cm2) treated cells. These data suggest that activation of phospholipase A2 is responsible for the UV induced release of AA in mammalian cells and that the mechanism of this activation is due, in part at least, to direct photon‐membrane interaction.
SPECTROSCOPIC PROPERTIES OF POTENTIAL SENSITIZERS FOR NEW PHOTODYNAMIC THERAPY START MECHANISMS via TWO‐STEP EXCITED ELECTRONIC STATES
Authors: Teuchner K. , Pfarrherr A. , Stiel H. , Freyer W. , Leupold D.
Published: January 2008

Three substituted tetraazaporphyrins, octa‐(4‐tert‐butylphenyl)‐tetrapyrazinoporphyrazine, tetra‐(4‐tert‐butyl)phthalocyanine and tetra‐(4‐tert‐butyi)phthalocyanatomagnesium (t4‐PcMg), were spectroscopically checked in solutions and liposomes with respect to suitability as potential sensitizers of a possible new start mechanism for photodynamic therapy (PDT) from a stepwise excited higher singlet state. This PDT start mechanism was recently proposed to overcome the problem of O2 (1δ2)‐caused cutaneous phototoxicity in PDT.

By means of absorption and fluorescence measurements as well as nonlinear absorption investigation, transient spectroscopy and lasing experiments, compound t4‐PcMg was found to have the most appropriate properties: Based on a high fluorescence quantum yield (φfi= 0.84) and a very low crossing to the triplet (φisc= 0.05), two higher excited states can be effectively populated both by two stepwise absorption transitions at 674 nm and consecutive absorption transitions at 674 and 710 nm. Moreover, t4‐PcMg incorporates into liposomes very well with spectroscopic properties similar to those in solution.
DETERMINING THE OPTIMAL DOSE OF PHOTOFRIN® IN MINISWINE ATHEROSCLEROTIC PLAQUE
Authors: Hsiang York N. , Fragoso Miguel , Tsang Vincent , Schreiber William E.
Published: January 2008

The purpose of this study was to determine the lowest dose of Photofrin (P) that would produce a 3:1 or greater ratio between atherosclerotic (AS) and control arterial walls. Aortoiliac AS was created in 24 Yucatan miniswine by a combination of balloon endothelial injury and 2% cholesterol and 15% lard diet for 7 weeks. Arteriography was then performed to demonstrate AS lesions. Following this, swine were given intravenously P in one of the following single dosages: 2.5, 1.0 or 0.5 mg/kg. Twenty‐four hours later, swine were sacrificed and aortoiliac and control carotid artery segments removed and photographed with ultraviolet light to differentiate fluorescent from nonfluorescent areas. Arterial specimens were submitted for histologic analysis and chemical extraction for determination of fluorescence using a spectrofluorometer. Tissue concentration (ng/g tissue) of P from AS vessels were: Group I, 130.4 ± 82.7; Group II, 10.0 ± 1.2; and Group HI, 9.1 ± 0.6, respectively (P < 0.05). Ratios of P concentration in AS:control vessels were: Group I, 8.1 ± 13.7; Group II, 1.1 ± 0.2; and Group III, 0.9 ± 0.1, respectively (P < 0.05).

These results demonstrated that a P dose of 2.5 mg/kg provided at least a 3:1 ratio between AS:control artery wall.
LIPOSOMAL DELIVERY OF A PHOTOSENSITIZER, BENZOPORPHYRIN DERIVATIVE MONOACID RING A (BPD), TO TUMOR TISSUE IN A MOUSE TUMOR MODEL
Authors: Richter Anna M. , Waterfield Elizabeth , Jain Ashok K. , Canaan Alice J. , Allison Beth A. , Levy Julia G.
Published: January 2008

Abstract— Biodistribution studies were carried out on 14C‐labeled benzoporphyrin derivative monoacid ring A (BPD), which had been formulated as a unilamellar liposome or taken from a stock solution in dimethyl sulfoxide diluted into phosphate‐buffered saline immediately before intravenous injection into DBA/2 mice. By and large the general distribution of BPD to various organs and tissues was comparable for both formulations. It was noted, however, that liposomal material appeared to enter tissues more rapidly and to be cleared more rapidly, as demonstrated by shorter half‐lives for a number of tissues including skin, lung and fat, and generally lower levels in most tissues 24 h following administration. Accumulation in tumor tissue was slightly higher with liposomal BPD, and clearance rates for this tissue were equivalent (half‐lives 16.1 h for liposomal BPD and 16.9 h for aqueous BPD). When the two preparations were tested in a bioassay in tumor‐bearing mice, photodynamic therapy (PDT) with liposomal BPD proved to be superior to the aqueous preparation when PDT was administered 3 h following intravenous administration of BPD. Plasma distribution studies in vitro demonstrated that 91.1 ± 0.3% of the liposomal BPD distributed to the lipoprotein fraction within the first hour of mixing, whereas only 49.1 ± 2.6% of nonliposomal BPD was associated with lipoprotein under the same conditions. Furthermore, while lipoprotein‐associated liposomal BPD distributed evenly between all three types of lipoprotein (high, low and very low density), a majority of nonliposomal BPD associated with the high‐density lipoprotein fraction.
THE PHOTOOXIDATION OF DIETHYLHYDROXYLAMINE BY ROSE BENGAL IN MICELLAR AND NONMICELLAR AQUEOUS SOLUTIONS
Authors: Bilski P. , Motten A. G. , Bilska M. , Chignell C. F.
Published: January 2008

The photooxidation of N,N‐diethylhydroxylamine (DEHA) by Rose Bengal (RB) has been investigated in micellar and nonmicellar aqueous solutions. We measured the quantum yield of oxygen consumption forming H2O2 and monitored two intermediates, the superoxide and diethylnitroxide radicals. When the pH was vaned, the quantum yield of oxidation remained constant for 6 < pH < 10.5, decreased in acidic pH, and increased considerably in NaOH solution; these changes could be attributed to the protonation and dissociation processes of the >N‐OH moiety of DEHA. The formation of diethylnitroxide radical was enhanced by superoxide dismutase or strong alkaline solution. Around neutral pH, the oxidation proceeded mainly via electron transfer from DEHA to the RB triplet (kq= 107M‐1 s‐1) with little 1O2 participation (kq < 105M‐1 s‐1). However, when RB was incorporated into micelles in alkaline solution, the contribution of the singlet oxygen pathway increased at the expense of electron transfer, which was inhibited by the less polar micellar environment. Dark autoxidation of DEHA was accelerated by heavy metal impurities and increased very strongly in NaOH solution.
FUROCOUMARIN SENSITIZATION INDUCES DNA‐PROTEIN CROSS‐LINKS
Authors: Bordin F. , Carlassare F. , Busulini L. , Baccichetti F.
Published: January 2008

The capacity of some linear and angular furocoumarins to induce DNA‐protein cross‐links by UVA (320–400 nm) irradiation has been evaluated in Chinese hamster ovary cells. Two linear furocoumarins, psoralen and 8‐methoxypsoralen appeared to be capable of inducing DNA‐protein cross‐links to a noticeable extent. 4′‐Methylangelicin and 4,4′‐dimethylangelicin formed only reduced amounts of DNA‐protein cross‐links, while angelicin and 4,6,4′‐trimethylangelicin seemed to be unable to induce significant levels of this lesion. The biological significance of this damage remains to be elucidated, but it might have an important role in furocoumarin sensitization. In the examined compounds, the capacity for inducing DNA‐protein cross‐links appears to be a property of the skin phototoxic furocoumarins. This result suggests the hypothesis of a connection between this damage and the formation of skin erythemas.
PROTECTIVE EFFECT OF SELENIUM AND ZINC ON UV‐A DAMAGE IN HUMAN SKIN FIBROBLASTS
Authors: Leccia M. T. , Richard M. J. , Bean J. C. , Faure H. , Monjo A. M. , Cadet J. , Amblard P. , Favier A.
Published: January 2008

Ultraviolet A radiation participates in cytotoxicity and carcinogenesis of the skin by a mechanism involving the generation of reactive oxygen species. Endogenous antiradical defense systems utilize metalloenzymes including Se‐dependent glutathione peroxidase and Cu and Zn superoxide dismutase. The aim of the present work was to determine the protective effect of two trace elements, Se and Zn, on cultured human diploid fibroblasts exposed to UV‐A radiation (broad‐spectrum source with a maximum intensity at 375 nm). Selenium in the culture medium (0.1 mg/L) in the form of sodium selenite increased the synthesis and activity of glutathione peroxidase by 60.5% in the absence of exposure to UV‐A radiation and by 35% after irradiation with 5 J/cm2 (P= 0.043). The presence of this element significantly increased the survival of UV‐A‐irradiated fibroblasts (P < 0.0001). This confirms the essential role of Se in the detoxifying activity of the enzyme. In addition, thiobarbituric acid‐reacting substances (TBAR), which are lipid peroxidation markers, decreased in the presence of exogenous Se:—19% and ‐22% without irradiation and after irradiation with 5 J/cm2 (P= 0.056). When Zn was added at the dose of 6.5 mg/L as ZnCl2, fibroblasts subjected to oxidizing stress induced by UV‐A were protected from cytotoxicity (P <0.0001). The TBAR production decreased significantly: ‐33% without irradiation and ‐34% after irradiation with 5 J/cm2 (P = 0.008). Superoxide dismutase activity, however, decreased after supplementing with Zn: ‐ 26% without irradiation and ‐ 20% after UV‐A irradiation (P= 0.017). The antioxidant properties of Zn are thus apparently independent of superoxide dismutase activity.
PHOTOCLEAVAGE OF DNA: IRRADIATION OF QUINONE‐CONTAINING REAGENTS CONVERTS SUPERCOILED TO LINEAR DNA
Authors: Koch Troels , Ropp J. Dezz , Sligar Stephen G. , Schuster Gary B.
Published: January 2008

Irradiation (350 nm) of air‐saturated solutions of reagents containing an anthraquinone group linked to quaternary alkyl ammonium groups converts supercoiled DNA to circular and to linear DNA. Generation of linear DNA does not occur by accumulation of numerous single‐strand cuts but by coincident‐site double‐strand cleavage of DNA. Irradiation forms the triplet state of the anthraquinone, which reacts either by hydrogen atom abstraction from a sugar of DNA or by electron transfer from a base of the DNA. Subsequent reactions result in chain scission. The quinone is apparently reformed after this sequence and reirradiation leads to double‐strand cleavage.
ULTRAVIOLET RADIATION IN ANTARCTICA: INHIBITION OF PRIMARY PRODUCTION
Authors: Holm‐Hansen Osmund , Helbling E. Walter , Lubin Dan
Published: January 2008

With the seasonal formation of the ozone hole over Antarctica, there is much concern regarding the effects of increased solar UV‐B radiation (280–320 nm) on the marine ecosystem in the Southern Ocean. In situ incubations of natural phytoplankton assemblages in antarctic waters indicate that under normal ozone conditions UV‐B radiation is responsible for a loss of approximately 4.9% of primary production in the euphotic zone, whereas UV radiation with wavelengths between 320 and 360 nm causes a loss of approximately 6.2%. When combined with data on the action spectrum for photoinhibition by UV radiation, our data suggest that the enhanced fluence of UV‐B radiation under a well‐developed ozone hole (150 Dobson units) would decrease daily primary productivity by an additional amount of 3.8%. Calculations that take into consideration the extent and duration of low stratospheric ozone concentrations during September to November indicate that the decrease in total annual primary production in antarctic waters due to enhanced UV‐B radiation would be 0.20%.