bluuebunny/crossref_metadata_2025 huggingface dataset:
RETINYLIDENE‐OPSIN SCHIFF BASE CHROMOPHORES AND THEIR ACCESSIBILITY TO WATER
Authors: Haarosi F. I. , Sándorfy C.
Published: January 2008

We propose a conceptual model to form the basis of understanding of the retinylidene‐opsin Schiff base (SB) chromophores. The first suggestion is that the protonated imine is H‐bonded to water, and this complex is similar in H‐bonding to a hydronium ion‐water dimer (H5O5+). The second proposal is a limited accessibility of water to the SB region of the chromophore. We scrutinize data from anion‐sensitive and UV‐absorbing visual pigments and find consistency with expectations based on the model: (1) Hydration plays a fundamental role in the photochemistry. (2) Protonation of the imine nitrogen is not obligatory. The latter point is supported by spectroscopic evidence from UV‐absorbing visual pigments, in which unprotonated SB chromophores are inferred. Further support is derived from thermodynamic analysis of the temperature dependence of protonation in SB models and in a UV‐absorbing visual pigment. We discuss H‐bonding opportunities for retinylidene‐opsin SB: the strong H‐bonds to ions, the weak H‐bonds of C‐H groups, serving as H‐bond donors, and of the π‐bonds, in which π‐electrons act as H‐bond acceptors.
TRENDS AND INTERANNUAL VARIATIONS IN ERYTHEMAL SUNLIGHT,1978–1993
Authors: Frederick John E. , Erlick Carynelisa
Published: January 2008

Abstract—

Information on column ozone and the earth's reflectivity obtained from satellite‐based data allows estimates of the long‐term behavior in erythemal irradiance at any location, including the attenuation provided by clouds. Year‐to‐year changes in cloudiness over specific geographic regions make a major contribution to interannual variability in irradiance at the ground. Although the general decline in column ozone amounts acted to increase erythemal irradiance over the period November 1978 to April 1993, these changes tend to be obscured by the erratic variability associated with cloudiness. The noise introduced into a time series of erythemal irradiance by clouds effectively widens the error bars assigned to derived trends. This behavior could complicate attempts to establish links between any observed changes in the biosphere and measured changes in the ozone layer.
THE EFFECT OF PHOTODYNAMIC TREATMENT OF YEAST WITH THE SENSITIZER CHLOROALUMINUM PHTHALOCYANINE ON VARIOUS CELLULAR PARAMETERS
Authors: Paardekooper Michel , Gompel Angeline E. Van , Steveninck John Van , Broek Peter J. A. Van den
Published: January 2008

Abstract—

Photodynamic treatment of Kluyveromyces marxianus with chloroaluminum‐phthalocyanine resulted in loss of clonogenicity. Several parameters were studied to identify targets that could be related to loss of colony‐forming capacity. Inhibition of various plasma membrane‐bound processes was observed, such as substrate transport and plasma membrane ATPase activity. Moreover, K+ loss from the cells was observed. Photodynamic treatment also reduced the activity of various enzymes involved in energy metabolism, thereby decreasing the cellular ATP level. It will be discussed however that none of these processes is likely to be related directly to loss of clonogenicity. Treatment with phthalocyanine and light resulted in a strong inhibition of the incorporation of 14C‐phenylalanine in trichloracetic acid‐precipitable material. The induction of the β‐galactoside utilization system was also strongly inhibited. The latter two processes did not recover during incubation, subsequent to photodynamic treatment. It is concluded that photodynamically induced inhibition of protein synthesis is a critical factor contributing to the loss of clonogenicity.
PHOTODYNAMICALLY GENERATED 3‐β‐HYDROXY‐5α‐CHOLEST‐6‐ENE‐5‐HYDROPEROXIDE: TOXIC REACTIVITY IN MEMBRANES and SUSCEPTIBILITY TO ENZYMATIC DETOXIFICATION
Authors: Geiger Peter G. , Korytowski Witold , Girotti Albert W.
Published: January 2008

Abstract—

Singlet oxygen (1O2)‐mediated photooxidation of cholesterol gives three hydroperoxide products: 3β‐hydroxy‐5α‐cholest‐6‐ene‐5‐hydroperoxide (5α‐OOH), 3β‐hydroxycholest‐4‐ene‐6α‐hydrope‐roxide (6α‐OOH) and 3β‐hydroxycholest‐4‐ene‐6β‐hydroperoxide (6β‐OOH). These species have been compared with respect to photogeneration rate on the one hand and susceptibility to enzymatic reduction/ detoxification on the other, using the erythrocyte ghost as a cholesterol‐containing test membrane and chloroaluminum phthalocyanine tetrasulfonate (AlPcS4) as a 1O2 sensitizer. Peroxide analysis was accomplished by high‐performance liquid chromatography with mercury cathode electrochemical detection (HPLC‐EC[Hg]). The initial rate of 5α‐OOH accumulation in AlPcS4/light‐treated ghosts was found to be about three times greater than that of 6α‐OOH or 6β‐OOH. Membranes irradiated in the presence of ascorbate and ferric‐8‐hydroxyquinoline (Fe[HQ]2, a lipophilic iron complex) accumulated lesser amounts of 5α‐OOH, 6α‐OOH and 6β‐OOH but relatively large amounts of another peroxide pair, 3β‐hydroxycholest‐5‐ene‐7α‐ and 7β‐hydroperoxide (7α,7β‐OOH), suggestive of iron‐mediated free radical peroxidation. When photoperoxidized membranes containing 5α‐OOH, 6α,6β‐OOH and 7α,7β‐OOH (arising from 5α‐OOH rearrangement) were incubated with glutathione (GSH) and phospholipid hydroperoxide glutathione peroxidase (PHGPX), all hydroperoxide species underwent HPLC‐EC(Hg)‐detect‐able reduction to alcohols, the relative first order rate constants being as follows: 1.0 (5α‐OOH), 2.0 (7α,7β‐OOH), 2.4 (6α‐OOH) and 3.2 (6β‐OOH). Relatively rapid photogeneration and slow detoxification might make 5α‐OOH more cytotoxic than the other peroxide species. To begin investigating this possibility, we inserted 5α‐OOH into ghosts by transferring it from 5α‐OOH‐containing liposomes. When exposed to Fe(HQ)2/ascorbate, these ghosts underwent GSH/PHGPX‐inhibitable chain peroxidation, as indicated by the appearance of 7α,7β‐OOH, phospholipid hydroperoxides and thiobarbituric acid reactive substances. Liposomal 5α‐OOH also exhibited a strong, Fe(HQ)2‐enhanced, toxicity toward LI210 leukemia cells, an effect presumably mediated by damaging chain peroxidation. This appears to be the first reported example of eukaryotic cytotoxicity attributed specifically to 5α‐OOH.
REDUCED NEAR‐UV SENSITIVITY IN Phycomyces MUTANTS AFFECTED IN THE BIOSYNTHESIS OF 6,7‐DIMETHYL‐8‐RIBITYLLUMAZINE
Authors: Tillmanns Sascha , Senger Horst , Galland Paul
Published: January 2008

Abstract—

Riboflavin‐requiring mutants of Phycomyces blakesleeanus with defects in the genes ribA, ribB, ribC and ribD were analyzed with respect to their contents of flavins, 6,7‐dimethyl‐8‐ribityllu‐mazine (DMRL) and pterins as well as their phototropic sensitivity. Strains were grown on minimal medium enriched with 10−6M riboflavin (RB), and the concentrations of the respective pigments in sporangiophores were determined by HPLC. In strains A607 ribC401 and A641 ribC402 madA7 a loss of DMRL correlated with a loss of near‐UV sensitivity. In general terms, the results suggest the participation of DMRL in photoreception, which does not necessarily imply DMRL as a photoreceptor chromophore. In more specific terms, the result could be understood on the basis of a UV/blue‐light photoreceptor, which includes besides a flavin also a lumazine‐like chromophore. Mutants C318 ribA I and C323 ribA4 accumulated DMRL, the immediate precursor of RB, as well as biopterin and neopterin. Mutant C322 ribB contained normal amounts of DMRL and pterins. Mutant C324 ribD5 had reduced amounts of neopterin and biopterin. The fact that some of the RB‐requiring mutants displayed abnormal amounts of pterins indicates a common regulation for the flavin and the pterin pathway.
DETECTION OF UVR‐INDUCED DNA DAMAGE IN MOUSE EPIDERMIS in vivo USING ALKALINE ELUTION
Authors: Kinley Judith S. , Brunborg Gunnar , Moan Johan , Young Antony R.
Published: January 2008

Abstract— Alkaline elution has been used to detect ultraviolet radiation (UVR)‐induced DNA damage in the epidermis of C3H/Tif hr/hr mice. This technique detects DNA damage in the form of single‐strand breaks and alkali‐labile sites (SSB) formed directly by UVA (320–400 nm) or indirectly by UVB (280–320 nm). The latter induces DNA damage such as cyclobutane pyrimidine dimers and pyrimidine‐pyrimidone (6–4)‐photoproducts, which are then converted into transient SSB by cellular endonucleases, during nucleotide excision repair (NER). The irradiation system used had a spectral output similar in effect to solar UVR, with the UVB component inducing 94% of the edema response observed in mice. Consequently, the majority of SSB detected were those formed via NER of UVB‐induced photoadducts. The number of SSB detected immediately after 8 kj/m2 (2.7 minimum erythema doses determined at 48 h post‐UVR [MED]) was low, indicating the formation of only small numbers of transient SSB. When DNA repair inhibitors hydroxyurea and 1 ‐β‐D‐arabinofuranosylcytosine were administered (intraperi‐toneally) to mice 30 min before UVR, they prevented sealing of the DNA SSB formed during NER. A four‐fold increase in the number of SSB detected resulted, which was found to be linearly related to the UVR dose. The SSB induced by 2 kj/m2 (less than an MED) were readily detected, with the ear showing lower numbers of SSB than the dorsum. When repair inhibitors were added post‐UVR, the rate of formation of SSB declined rapidly with time of administration, reflecting repair of DNA lesions. After a UVR dose of 6 kj/m2 (2 MED), 50% of the initial repair‐dependent SSB had been removed after approximately 2 h in the ear and 4 h in the dorsum; no more SSB appeared to be incised by 24 h post‐UVR. The technique described is an efficient and highly sensitive one for the quantification of SSB induced in UV‐irradiated skin samples in vivo.
INTERACTION BETWEEN HUMAN α1ACID GLYCOPROTEIN (OROSOMUCOID) AND 2‐p‐TOLUIDINYLNAPHTHALENE‐6‐SULFONATE
Authors: Albani J. , Vos R. , Willaert K. , Engelborghs Y.
Published: January 2008

Abstract—

The interaction between human α1‐acid glycoprotein (orosomucoid) and the fluorescent probe, 2‐p‐toluidinylnaphthalene‐6‐sulfonate (TNS) has been studied. An association constant of 16.7 (±3) X 103M‐1 was obtained for the complex at 20°C with a stoichiometry of 1:1. From the effect of temperature on the binding process, the standard enthalpy change for the binding is calculated to be ΔH0= ‐18 ± 3 kJ mol‐1 and the standard entropy change ΔS0= 19 ± 12 J K‐1 mol‐1. The tryptophan fluorescence of the protein can be described by a sum of three exponentials. Upon TNS binding, the average fluorescence lifetime of the protein in the complex changes much less than the fluorescence intensity. The bound TNS is therefore a very efficient acceptor for the protein fluorescence. The TNS bound to orosomucoid presents two fluorescence lifetimes 1 1 and 4.3 ns. The possible origins of the two lifetimes are discussed.
CATALASE INACTIVATION FOLLOWING PHOTOSENSITIZATION WITH TETRASULFONATEDMETALLOPHTHALOCYANINES
Authors: Gantchev Tsvetan G. , van Lier Johan E.
Published: January 2008

Abstract— Catalase (CAT) in solution or incorporated in erythrocytes and K562 leukemic cells is inactivated during photosensitization with tetrasulfonated metallophthalocyantnes (MePcS4). The effect of added scavengers and D20 showed that both singlet oxygen and free radical species are involved in this process. Evidence was found that direct interactions of ground or excited‐stated photosensitizers with CAT are not responsible for CAT inactivation. Specific techniques to probe early damage to the CAT structure involved optical and EPR spectroscopy, HPLC and polyacrylamide gel electrophoresis analyses. Different primary events of photosensitized protein damage included oxidation of cysteine residues as well as other amino acids, as demonstrated by the formation of carbon‐centered free radicals and the loss of absorbance at λ= 275 nm. In parallel, we detected degradation of the CAT heme groups, accompanied by release of Fe(II) ions in solution. These combined phenomena initiate cross‐linkages between CAT subunits and subsequent degradation of the protein with formation of irreversible aggregates in solution. Phthalocyanine‐mediated photoinactivation of cell‐bound CAT results in loss of protection against accumulating H202, providing an additional pathway of phototoxicity.
TIME‐DEPENDENT PHOTODYNAMIC DAMAGE TO BLOOD VESSELS: CORRELATION WITH SERUM PHOTOSENSITIZER LEVELS
Authors: Silva Fernando A. Menezes da , Newman E. L.
Published: January 2008

Abstract— We have used the technique of dynamic capillaroscopy to study the time‐course of photo‐dynamic vascular occlusion in mice injected intraperitoneally with either of two photosensitizers; hematoporphyrin esters (HPE) or meso‐tetrahydroxyphenyl chlorin (mTHPC). The peak of vascular occlusion induced by HPE coincided in time with peak serum levels of this photosensitizer (about 3 h after injection). However, there was also a second peak of occlusive activity at about 12 h after injection, at which time serum HPE was falling monotonically. In the case of mTHPC, no peak of occlusive activity was seen at 3 h after injection, even though the serum levels of this photosensitizer, like those of HPE, were highest around this time. Instead, a steady rise in photosensitizing activity was observed, peaking at 11 h. This decoupling between serum drug levels and vascular photosensitization—partial for HPE and complete for mTHPC—suggests that direct photosensitization of endothelial cells is unlikely wholly to explain the vascular collapse. Instead, there must be either another compartment that accumulates photosensitizer more slowly and in which photodynamic activity has an indirect effect on the blood capillaries or a slow metabolic transformation of mTHPC into a more active sensitizer.
GREEN FLUORESCENT PROTEIN
Authors: Chalfie Martin
Published: January 2008

Abstract— Several bioluminescent coelenterates use a secondary fluorescent protein, the green fluorescent protein (GFP), in an energy transfer reaction to produce green light. The most studied of these proteins have been the GFPs from the jellyfish Aequorea victoria and the sea pansy Renilla reniformis. Although the proteins from these organisms are not identical, they are thought to have the same chro‐mophore, which is derived from the primary amino acid sequence of GFP. The differences are thought to be due to changes in the protein environment of the chromophore. Recent interest in these molecules has arisen from the cloning of the Aequorea gfp cDNA and the demonstration that its expression in the absence of other Aequorea proteins results in a fluorescent product. This demonstration indicated that GFP could be used as a marker of gene expression and protein localization in living and fixed tissues. Bacterial, plant and animal (including mammalian) cells all express GFP. The heterologous expression of the gfp cDNA has also meant that it could be mutated to produce proteins with different fluorescent properties. Variants with more intense fluorescence or alterations in the excitation and emission spectra have been produced.
MOLECULAR EVOLUTION OF THE Ca2+‐BINDING PHOTOPROTEINS OF THE HYDROZOA
Authors: Tsuji Frederick I. , Ohmiya Yoshihiro , Fagan Thomas F. , Toh Hiroyuki , Inouye Satoshi
Published: January 2008

Abstract— Alignment of the primary structures of the hydrozoan photoproteins, aequorin, mitrocomin, clytin and obelin showed very strong amino acid sequence identities. The Ca2+‐binding sites of the proteins were found to be highly conserved. The Ca2+‐binding sites were also homologous to the Ca2+‐binding sites of other Ca2+‐binding proteins. However, aequorin, mitrocomin, clytin and obelin differed from other Ca2+‐binding proteins in that they contained a relatively large number of cysteine, tryptophan, histidine, proline and tyrosine residues, suggesting that these residues may have evolved as part of the light‐emitting mechanism. Construction of a phylogenetic tree showed that aequorin, mitrocomin, clytin and obelin form a closely related group of proteins.
FLUORESCENCE STUDIES ON THE ADSORPTION OF OCTADECYLRHODAMINE B ONTO A LATEX SURFACE
Authors: Nakashima Kenichi , Fujimoto Yoshinori , Kido Naofumi
Published: January 2008

Abstract— The interaction of octadecylrhodamine B (ORB), a lipid‐conjugated dye, with polystyrene latex in aqueous dispersions has been investigated by fluorescence techniques. The dependence of the fluorescence intensity of ORB on the latex concentration indicates that the dye is effectively adsorbed onto the latex surface from the aqueous phase and that deaggregation to fluorescent monomers from the nonfluorescent multimers takes place cooperatively when the surface coverage of the dye is reduced to a critical value. The fluorescence lifetime increases on going from a homogeneous methanolic solution to the latex dispersion, showing that the mobility of the probe is suppressed on the latex surface. From the results of polarization measurements, it is proposed that ORB molecules are adsorbed on the latex surface by a side‐on geometry. The influence of a nonionic surfactant, triton X‐100, on the fluorescence intensities of ORB and rhodamine B in the latex dispersion is also investigated.
INTERACTION OF PHOTODYNAMICALLY INDUCED CELL KILLING and DARK CYTOTOXICITY OF RHODAMINE 123
Authors: VanDerWal Jaap , Lagerberg Johan W. M. , Dubbelman Tom M. A. R. , VanSteveninck John
Published: January 2008

Abstract— Loss of clonogenicity of Chinese hamster ovary (CHO) cells, murine L929 fibroblasts and human bladder carcinoma T24 cells caused by photodynamic treatment (PDT) with hematoporphyrin derivative (HPD) is synergistically enhanced by subsequent incubation with rhodamine 123 in the dark. For CHO and L929 cells this synergistic interaction can be explained by an increased uptake of rhodamine 123 as the result of the photodynamic treatment. With aluminum phthalocyanine (AIPc) as photosensitizer only additive effects were observed in the three cell lines. Incubation in the dark with rhodamine 123, followed by a photodynamic treatment with HPD, resulted in an antagonistic interaction with regard to loss of colony formation. With AIPc the combination of treatments resulted in an additive effect with L929 and T24 cells, whereas with CHO cells a slight antagonistic interaction was observed. An antagonistic effect was also observed in model experiments, treating histidine photodynamically with HPD and measuring oxygen consumption. A possible explanation of these results could be an interaction or complex formation of rhodamine 123 with HPD resulting in a diminished singlet oxygen production. With AIPc this does not take place.
RAPID COMMUNICATION
Authors: Gryczynski Ignacy , Szmacinski Henryk , Lakowicz Joseph R.
Published: January 2008

Abstract— We show that the calcium fiuorophore Indo‐1 can be excited by simultaneous absorption of three‐photons at 885 nra, a wavelength readily available from Ti:sapphire lasers. Three‐photon excitation was demonstrated by the emission intensity of Indo‐1 which depended on the cube of the laser power, and by a higher anisotropy than was observed for two‐photon excitation. Excitation of Indo‐1 becomes a two‐photon process when the wavelength is decreased to 820 nm. Three‐photon excitation was accomplished at a low 17μ concentration of Indo‐1. Examination of the spatial profile of the excited Indo‐1 showed a smaller volume for three‐ versus two‐photon excitation. These results suggest that three‐photon excitation may be useful in fluorescence microscopy using the long wavelength output of Tksapphire lasers, and may provide higher spatial resolution than available using two‐photon excitation.
POLYPHASIC CHLOROPHYLL a FLUORESCENCE TRANSIENT IN PLANTS AND CYANOBACTERIA*
Authors: Strasserf Reto J. , Srivastava Alaka , Govindjee  
Published: January 2008

Abstract— The variable chlorophyll (Chl) a fluorescence yield is known to be related to the photochemical activity of photosystem II (PSII) of oxygen‐evolving organisms. The kinetics of the fluorescence rise from the minimum yield, F0, to the maximum yield, Fm, is a monitor of the accumulation of net reduced primary bound plastoquinone (QA) with time in all the PSII centers. Using a shutter‐less system (Plant Efficiency Analyzer, Hansatech, UK), which allows data accumulation over several orders of magnitude of time (40 μs to 120 s), we have measured on a logarithmic time scale, for the first time, the complete polyphasic fluorescence rise for a variety of oxygenic plants and cyanobacteria at different light intensities. With increasing light intensity, the fluorescence rise is changed from a typical O‐I‐P characteristic to curves with two intermediate levels J and I, both of which show saturation at high light intensity but different intensity dependence. Under physiological conditions, Chl a fluorescence transients of all the organisms examined follow the sequence of O‐J‐I‐P. The characteristics of the kinetics with respect to light intensity and temperature suggest that the O‐J phase is the photochemical phase, leading to the reduction of QA to QA‐. The intermediate level I is suggested to be related to a heterogeneity in the filling up of the plastoquinone pool. The P is reached when all the plastoquinone (PQ) molecules are reduced to PQH2. The addition of 3‐(3–4‐dichlorophenyl)‐1,1‐dimethylurea leads to a transformation of the O‐J‐I‐P rise into an O‐J rise. The kinetics of O‐J‐I‐P observed here was found to be similar to that of O‐I1‐I2‐P, reported by Neubauer and Schreiber (Z. Naturforsch.42c, 1246–1254, 1987). The biochemical significance of the fluorescence steps O‐J‐I‐P with respect to the filling up of the plastoquinone pool by PSII reactions is discussed.
MULTIPLE EFFECTS OF FLUORESCENT LIGHT ON REPAIR OF ULTRAVIOLET‐INDUCED DNA LESIONS IN CULTURED GOLDFISH CELLS
Authors: Uchida Nobuhiro , Mitani Hiroshi , Shima Akihiro
Published: January 2008

Abstract— It is known that fluorescent light illumination prior to UV irradiation (FL preillumination) of cultured fish cells increases photorepair (PR) ability. In the present study, it was found that FL preillumination also enhanced UV resistance of logarithmically growing cells in the dark. This enhancement of UV resistance differs from induction of PR because it was not suppressed by cycloheximide (CH) and it occurred immediately after FL preillumination. The effects of FL preillumination on repair of UV‐induced DNA lesions in the dark were examined by an endonuclease‐sensitive site assay to measure the repair of cyclobutyl pyrimidine dimers, and by enzyme‐linked immunosorbent assay to quantitate the repair of (6‐4) photoproducts. It was found that excision repair ability for (6‐4) photoproducts in the genome overall was increased by FL preillumination. Moreover, a decrease in (6‐4) photoproducts by FL illumination immediately after UV irradiation of the cells was found, the decrement being enhanced by FL preillumination with or without CH.
Photohaptenic Properties of Fluoroquinolones
Authors: Tokura Yoshiki , Nishijima Takafumi , Yagi Hiroaki , Furukawa Fukumi , Takigawa Masahiro
Published: January 2008

Abstract— Although quinolone antibacterial agents have both phototoxicity and photoallergenicity, the latter's potency has been poorly investigated compared with the former's. Some of the photoallergic chemicals serve as photohap‐tens, which lead to T‐cell‐mediated immune reactions after photobinding to protein by UVA radiation. We examined the photohaptenic potential of fluoroquinolones, including lomefloxacin (LFLX), ciplofloxacin, norfloxacin, ofloxacin, levofloxacin, fleroxacin, enoxacin and spar‐floxacin (SPFX). The absorption spectra of the quinolo‐nes were altered by UVA irradiation, with an exception of SPFX that seems to be photostable toward UVA. Bovine serum albumin and murine epidermal cells were coupled with these fluoroquinolones other than SPFX by exposure to UVA. Subcutaneous inoculation of fluoro‐quinolone‐photomodified epidermal cells induced and elicited a delayed‐type hypersensitivity reaction in mice. However, epidermal cells incubated with LFLX without UVA exposure also induced and elicited a significant hypersensitivity reaction to a lesser degree than LFLX‐pho‐tomodified epidermal cells. Furthermore, there was cross‐reactivity between LFLX‐photomodified epidermal cells and simply LFLX‐incubated cells. This suggests that cells can be weakly modified with LFLX even in the dark and that UVA irradiation promotes this modification. Our study demonstrated that fluoroquinolones have photohaptenic properties to which their photoallergenicity is probably ascribed.
Action Spectrum for Sporulation and Photoavoidance in the Plasmodium of Physarum polycephalum, as Modified Differentially by Temperature and Starvation
Authors: Nakagaki Toshiyuki , Umemura Shoji , Kakiuchi Yasutaka , Ueda Tetsuo
Published: January 2008

Abstract— The Plasmodium of the myxomycete Physarum polycephalum sporulates in bright natural environments, suggesting a relationship between photobehavior and sporulation. Thus, the action spectra for two light‐dependent phenomena as well as the effects of other environmental conditions have been studied. Sporulation like photo‐avoidance responded to UVC (near 270 nm) and near IR (near 750 nm) in addition to the well‐documented UVA (near 350 nm) and blue (near 460 nm) regions. Sporulation and photoavoidance had similar sensitivities in the shorter wavelengths, while the former was about 100 times more sensitive in near IR. The Plasmodium moved away from light in a wide spectral range. Starvation and high temperature at 31°C (25°C in standard conditions) reduced photoavoidance to UVA and to blue light, respectively. A high fluence rate of UVC suppressed the rhythmic contraction of the Plasmodium, and the action spectrum peaked at 270 nm. These results indicate that the Physarum Plasmodium may stay at brighter places not by positive phototaxis but by weakening the negative phototaxis to sunlight or by other possible taxes such as hydrotaxis. There may be at least four different photo‐systems in the Plasmodium.
Ultraviolet B Wavelength Dependence for the Regulation of Two Major Matrix‐Metalloproteinases and Their Inhibitor TIMP‐1 in Human Dermal Fibroblasts
Authors: Brenneisen Peter , Oh Jinsook , Wlaschek Meinhard , Wenk Jutta , Briviba Karlis , Hommel Christina , Herrmann Gemot , Sies Helmut , Scharffetter‐Kochanek Karin
Published: January 2008

Abstract— The wavelength dependence for the regulation of two major matrix‐metalloproteinases, interstitial collagenase (MMP‐1) and stromelysin‐1 (MMP‐3), and their major inhibitor, tissue inhibitor of metalloproteinases (TIMP‐1), was studied in human dermal fibroblasts in vitro. Monochromatic irradiation at 302, 307, 312 and 317 nm with intensities ranging from 20 to 300 J/m2 increased MMP‐1 and MMP‐3 mRNA steady‐state levels and the secretion of the corresponding proteins up to 4.4‐fold, whereas almost no increase was observed at wavelengths <290 nm. In contrast, the synthesis of TIMP‐1 increased only marginally. This unbalance may contribute to the severe connective tissue damage related to photoaging of the skin. The wavelengths responsible for MMP‐1 and MMP‐3 induction reported here are distinct from the absorption spectrum of DNA and are different from results previously reported in the literature. Importantly, they overlap with wavelengths whose intensity is predicted to increase on the earth's surface upon ozone depletion. Intensities and particular wavelengths used in our studies in vitro can be absorbed readily by fibroblasts within the skin in vivo and, thus, are relevant for risk assessment and development of protective agents.
Ultraweak Luminescence Generated by Sweet Potato and Fusarium oxysporum Interactions Associated with a Defense Response
Authors: Makino Takahiro , Kato Kimihiko , Lyozumi Hiroyuki , Honzawa Hiroe , Tachiiri Yoshiaki , Hiramatsu Mitsuo
Published: January 2008

Abstract— Ultraweak luminescence generated by sweet potato and nonpathogenic Fusarium oxysporum interactions associated with a defense response was detected by a photoncounting method using ultrahigh‐sensitive photodetectors. The time‐dependent intensity variation, the spectrum and the two‐dimensional imaging of the ultraweak luminescence are indicative of the defense response of the sweet potato to F. oxysporum. The production of ipomeamarone as a phytoalexin means that F. oxysporum induced the defense response in the sweet potato.
The Effect of Cold Stress on UVB Injury in Mouse Skin and Cultured Keratinocytes
Authors: Ota Toshiaki , Hanada Katsumi , Hashimoto Isao
Published: January 2008

Abstract— The effect of cold stress on skin damage caused by UVB irradiation was investigated both in vivo and in vitro. Ear skin of mice that had been exposed to cold stress at 0°C for 20 min and at 5°C for 24 h was exposed to UVB radiation. Sunburn cell production was less in mice exposed to the lower temperature. In addition, the effect of cold stress on the survival rate of UVB‐irradiated rat keratinocytes was examined in a cytotoxicity test, with the results showing that keratinocytes exposed to cold stress of 0°C had a higher survival rate than control cells. To pursue a promising clue for explaining the result, we examined metallothionein (MT) production in rat keratinocytes that had been exposed to cold stress at 0°C. Microfluorometric quantification showed a positive correlation between the time course and the intensity of immunofluorescence for MT, indicating that the molecule is inducible by exposure to cold stress in our experimental system. These results suggest that epidermal cells that have been exposed to cold stress maintain a higher resistance to UV radiation than nonexposed controls in vivo and in vitro, and that MT with radical‐scavenging activity might contribute, at least in part, to photoprotection against UVB‐induced oxidative damage in mammalian skin.
14N Electron Spin Echo Envelope Modulation (ESEEM) Spectroscopy of the Cation Radical P840+, the Primary Electron Donor of the Chlorobium limicola Reaction Center
Authors: Bratt Peter J. , Muhiuddin Irine P. , Evans Michael C. W. , Heathcote Peter
Published: January 2008

The electronic structure of the oxidized primary chlorophyll electron donor, P840+., of the green sulfur bacterium Chlorobium limicola has been investigated using electron spin echo envelope modulation (ESEEM) spectroscopy. This ESEEM investigation of the electron spin density distribution in the radical cation P840+. in membranes isolated from C. limicola confirms that the electron spin is shared eqully between the two bacteriochlorophyll a molecules. Observation of the small hyperfine couplings to the ring nitrogens by ESEEM gives results that are in agreement with those obtained from ENDOR measurements (S. E. J. Rigby, R. Thapar, M. C. W. Evans and P. Heathcote, FEBS Lett. 350,24–28, 1994) of the large hyperfine couplings to the methyl group protons. These results in combination with the Raman spectroscopy of P840 (U. Feiler, D. Albouy, B. Robert and T. A. Mattioli, Biochemistry 34,11099–11105, 1995) all indicate that the reaction center of green sulfur photosynthetic bacteria is functionally a protein homodimer providing a symmetrical protein environment for the primary electron donor.
Temperature Dependence of Charge Recombination in Heliobacillus mobilis
Authors: Chlou Hung‐Cheng , Blankenship Robert E.
Published: January 2008

Transient absorption difference spectroscopy was used to study the temperature dependence of the P798+ decay kinetics in heliobacteria. For membrane samples, two components were obtained from the fitting of kinetic traces in the temperature range of4–29°C. A3–9 ms component representing the cytochrome (cyt) c oxidation has an activation energy of 33.0 ± 2.8 KJ/mol. A12–22 ms component representing either P798+Fx ‐ or P798+FA/B recombination has an activation energy of 15.3 ± 2.4 KJ/mol. In isolated reaction centers (RC), only one 14 ms component due to P798+Fx ‐ recombination was obtained in this temperature range. The Arrhenius plot shows that the recombination rate of this P798+Fx ‐ state is temperature independent in the near room temperature range. For RC in the temperature range of60–298 K, a12–15 ms decay was obtained at temperatures greater than 240 K. Biphasic decay traces (12–15ms and2–4 ms components) were obtained at temperatures between 170 K and 230 K. Only one2–4 ms component was found at temperatures lower than 160 K. The gradual switchover from the12–15 ms to the2–4 ms component upon cooling may indicate the shift of the P798+Fx ‐ recombination state to a state that is prior to P798+Fx, although other interpretations can not be excluded. The absorption difference spectrum (ΔA@ 160 K ‐ ΔA@ 240 K) in the blue region shows a positive amplitude below 405 nm and a negative amplitude above 405 nm implying that the2–4 ms decay component may be due to the recombination of P798+A1‐, where A1 is a quinone‐type acceptor.
Site‐Directed Mutagenesis and Analysis of Second‐Site Revertants Indicates a Requirement for C‐Terminal Amino Acids of PsaB for Stable Assembly of the Photosystem I Reaction Center Complex in Chlamydomonas reinhardtii
Authors: Lee Hyeonmoo , Bingham Scott E. , Webber Andrew N.
Published: January 2008

The PsaA and PsaB polypeptides form the reaction center core heterodimer of photosystem I (PSI). Both PsaA and PsaB are predicted to have 11 hydrophobic domains, although it is unclear how both polypeptides fold within the thylakoid membrane. If all 11 hydrophobic regions form membrane‐spanning domains, the N‐ and C‐terminus must be located on opposite sides of the membrane. The C‐terminus of PsaB is very conserved in a wide range of organisms and may be important for PSI assembly or function. Using chloroplast transformation in Chlamydomonas reinhardtii we have generated a series of C‐terminal extension and deletion mutants of the PsaB polypeptide. Analysis of these mutants and spontaneous revertants indicates that the C‐terminus may be extended by at least 14 amino acids without impairing PSI assembly. Deletion of amino acids 732–736 also has no impact on PSI, whereas deletion of amino acids 727–736 results in no accumulation of the complex. The site of truncation in the 727–736 deletion coincides with the end of the hydrophobic domain XI supporting a location of the C‐terminus of PsaB on the lumenal side of PSI.
Thymidine‐Psoralen Photoaddition: Stereoselective Formation of Atrans‐synPyrone Adduct
Authors: Décout Jean‐Luc , Guendouz Amine , Lhomme Jean
Published: January 2008

To study the photoreactions between thymidine and psoralen and to devise a synthetic route to prepare thymidine‐5‐methoxypsoralen adducts, we have synthesized a compound in which thymidine is linked to a 5‐methoxypsoralen derivative by a short flexible chain located to allow only the formation ofsynintramolecular [2+2] cycloadducts. Irradiation at 365 nm carried out at usual concentrations (10−2‐10−3M) resulted in a regioselective dimerization involving the 3,4 double bonds. Extreme dilution (c5 × 106M) was necessary to observe the intramolecular photoaddition, which produces exclusively the 3,4‐trans‐synadduct. These results are compared to those obtained previously with similar heterodimers that lead exclusively to the 3,4‐cis‐antithymine or thymidine‐psoralen adduct on exposure to near UV light.
8‐Oxodeoxyguanosine Formation in the DNA of Cultured Cells After Exposure to H2O2 Alone or with UVB or UVA Irradiation
Authors: Rosen J. E. , Prahalad A. K. , Williams G. M.
Published: January 2008

The objective of the present study was to establish whether H2O2 alone or in the presence of UVA or UVB would give rise to formation of the oxidatively damaged DNA base 7, 8‐dihydro‐8‐oxo‐2′‐deoxyguanosine (8‐oxo‐dG) in cultured adult rat liver (ARL‐18) epithelial cells. Hydrogen peroxide alone at 5 mM increased 8‐oxo‐dG levels by 42% of that of culture control. Compared to culture control, UVB exposure at a dose of 0.63 J/cm2 elevated 8‐oxo‐dG levels only 8.4%. In the presence of 5 mM H2O2+ UVB (0.63 J/cm2), 8‐oxo‐dG levels were elevated 155% above culture control suggesting a synergistic effect. A UVA dose of 10 J/cm2 did not elevate 8‐oxo‐dG levels above culture control. In the presence of 5 mM H2O2 plus UVA (12 J/cm2), 8‐oxo‐dG levels were elevated 310% above controls compared with an increase of 75.8% above control levels at the same dose in the absence of H2O2. These results reveal that both UVA or UVB can promote H2O2 generation of reactive oxygen species (ROS) in whole cells resulting in an increase in the formation of 8‐oxo‐dG, although the photodynamic generation of ROS from H2O2 occurs with a much higher efficiency in the presence of UVB. Our study also demonstrates that 8‐oxo‐dG can be generated in cellular DNA of whole cells exposed to H2O2 and UVA or UVB, indicating that the ROS generated in whole cell systems are long enough lived to migrate to the nucleus and cause DNA damage.
Hypericin‐Induced Phototoxicity in Cultured Fibroblasts and Swine Erythrocytes
Authors: Yu Hai , Wolford Suzanne T. , Kegode Redempta , Zhao Wei , Osweiler Gary D.
Published: January 2008

Hypericin is a naturally occurring photosensitizer, whose presence in plants has been responsible for cutaneous phototoxicity in grazing animals. The photosensitizing properties of this agent have recently been exploited in models for anti‐tumor and anti‐viral activity. The cytotoxicity of hypericin and light was assessed in 3T3 mouse fibroblasts using the MTT [3‐(4, 5‐dimethylthiazol‐2‐yl)‐2, 5‐diphenyl tetrazolium bromide)] assay and the lactate dehydrogenase (LDH) leakage assay. Membrane damage was assessed in swine erythrocytes using hemolysis, potassium (K+) leakage and formation of lipid hydroperoxides. Concentration‐ and light‐dependent decreases in fibroblast viability were seen starting at hypericin concentrations of 1.25 μM and light power flux levels of 24 J/cm2 using a visible light source and at 0.417 μM hypericin and a similar light dose using a solar simulator, No LDH leakage was observed at hypericin concentrations up to 30 μM and visible light up to 144 J/cm2. Light‐and/or concentration‐dependent increases in hemolysis, K+ leakage and formation of lipid hydroperoxides in red blood cell (RBC) membranes were observed, but at concentrations and light doses much greater than those required to induce cytotoxicity in fibroblasts. Lipid peroxidation and hemolysis occurred at 15 μM hypericin and 24 J/cm2 (visible light source). Potassium ion leakage occurred at concentrations and light levels as low as 5 μM and 12 J/cm2 or 15 μM and 4.8 J/cm2 (visible light source) but was still a less sensitive indicator than fibroblast cytotoxicity. Evidence for both type I and type II reactions was shown in RBC membranes by TLC analysis of cholesterol products. In the absence of light, hypericin appears to be relatively nontoxic in the models tested.
Signal Transduction and HIV Transcriptional Activation After Exposure to Ultraviolet Light and Other DNA‐Damaging Agents
Authors: Valerie Kristoffer , Laster William S. , Cheng Luhua , Kirkham Jean C. , Reavey Peter , Kuemmerle Nancy B.
Published: January 2008

Short wavelength (254 nm) ultraviolet light (UVC)† radiation was much more potent in activating transcription of human immunodeficiency virus 1 (HIV) reporter genes stably integrated into the genomes of human and monkey cells than ionizing radiation (IR) from a 137Cs source at similarly cytotoxic doses. A similar differential was also observed when c‐jun transcription levels were examined. However, these transcription levels do not correlate with activation of nuclear factor (NF)‐kB and AP‐1 measured by band‐shift assays., i. e. both types of radiation produce similar increases in NF‐kB and AP‐1 activity, suggesting existence of additional levels of regulation during these responses. Because of the well‐established involvement of cytoplasmic signaling pathways in the cellular response to tumor necrosis factor‐α (TNF‐α), UVC, and IR using other types of assays, the role of TNF‐α in the UVC response of HIV and c‐jun was investigated in our cell system. We demonstrate that UVC and TNF‐α activate HIV gene expression in a synergistic fashion, suggesting that it is unlikely that TNF‐α is involved in UVC activation of HIV transcription in stably transfected HeLa cells. Moreover, maximum TNF‐α stimulation resulted in one order of magnitude lower levels of HIV expression than that observed after UVC exposure. We also observed an additive effect of UVC and TNF‐α on c‐jun steady‐state mRNA levels, suggestive of a partial overlap in activation mechanism of c‐jun by UVC and TNF‐α; yet these responses are distinct to some extent. Our results indicate that the HIV, and to some extent also the c‐jun, transcriptional responses to UVC are not the result of TNF‐α stimulation and subsequent downstream cytoplasmic signaling events in HeLa cells. Additional levels of regulation that do not directly involve the NF‐kB and AP‐1 transcription factors, such as changes in chromatin structure associated with the UV repair process, may also be important for a full transcriptional response of HIV and c‐jun to UVC. In addition to the new data, this report also summarizes our current views regarding UVC‐induced activations of HIV gene expression in stably transfected cells.
Log‐Normal Description of Fluorescence Spectra of Organic Fluorophores
Authors: Burstein Edward A. , Emelyanenko Victor I.
Published: January 2008

The smooth fluorescence bands of various organic fluorophores of different classes (e. g. indole, tryptophan, tyrosine, phthalimides, quinine sulfate, aminopyridines, acetylanthracenes) in different ionization states of their substituents and dissolved in various solvents can be accurately fitted on the frequency (wavenumber) scale by the four‐parametric log‐normal distribution curves up to the far spectral wings. This fact suggests that the log‐normal function is a good analytical description for smooth emission spectra of so‐called complex molecules. Examination of log‐normal parameters of 126 spectra of several tryptophan derivatives measured in different ionization states in various solvents revealed a straight‐linear relation between three shape parameters of the log‐normal function, namely, the positions of spectral maxima and of the two half‐maximal amplitudes. This fact indicates that only one parameter is needed to describe the band shape for the set of tryptophan derivatives. A similar linearity was also observed for the series of spectra of 1‐ and 2‐acetylanthracenes or 3‐amino‐N‐methyl‐phthalimides when varying the solvent. As a result, the spectral maximum position can entirely determine the shape of emission spectra of a series of a fluorophore derivatives in any environmental condition. Such a simplified mathematical representation significantly facilitates the problem of analytical resolution of composite fluorescence spectra, for instance, those of proteins.
Lethal Effect Induced in Pseudomonas aeruglnosa Exposed to Ultraviolet‐A Radiation
Authors: Fernández Rubén O. , Pizarro Ramón A.
Published: January 2008

Ultraviolet‐A (365 nm, 120 kJ/m2/h) exposure caused cell death in Pseudomonas aeruginosa at doses at which Escherichia coli cell viability was not affected. We have not found that UVA induced growth delay or any other sublethal effect. Irradiated suspensions of P. aeruginosa showed a marked reduction in membrane‐bound succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH) activities. Succinate‐driven respiration and several nutrient transport systems were also inhibited. Whereas SDH and LDH activities were independent of the irradiation conditions, cell viability, respiration and transport systems were protected when irradiation was performed in an N2 atmosphere. A similar protective effect was observed when cells were grown in media containing glycerol or when preirradiation bacterial growth was carried out at 30°C (instead of 37°C). Results suggest that UVA induces a differential damaging effect on several biochemical functions of P. aeruginosa. The UVA induced photodamage may fall into two categories: indirect damage mediated by oxygen (cell killing and inhibition of respiration and transport systems) and direct damage to SDH and LDH (apparently not oxygen dependent). These enzymes and leucine transport appear not to be involved in the lethal effect described herein because they were altered despite viability‐preserving conditions.
Circular and Linear Dichroism of Aggregates of Chlorophyll a and Chlorophyll b in 3‐Methylpentane and Paraffin Oil
Authors: Oksanen J. A. I. , Helenius V. M. , Hynninen P. H. , Amerongen H. van , Korppi‐Tommola J. E. I. , Grondelle R. van
Published: January 2008

A circular (CD) and linear dichroism (LD) study of the water adducts of the green plant chlorophylls a (Chl a) and b (Chl b) in hydrocarbon solvents 3‐methylpentane and paraffin oil is presented. A strong red shift of the Qy‐absorption band from 663 to 746 nm (1678 cm−1) is observed as the water adduct of Chl a is formed. The Chl a‐water adduct shows a strong, nonconservative CD signal, which is characterized by a positive peak at 748 nm and two negative peaks at 720 and 771 nm. The maximum CD (AL ‐ AR) is only one order of magnitude smaller than the isotropic absorption maximum. We propose that this exceptionally strong signal is the so‐called psi‐type CD. The LD spectrum was measured in a flow of paraffin oil. The isotropic absorption maximum peaks at 742 nm in paraffin oil, whereas the maximum of the LD signal is at 743 nm. The LD signal is positive over the whole water‐adduct absorption band indicating that the transition dipole of the 742 nm transition is preferentially oriented along the long axis of the aggregate. The structure of the Chl b‐water adduct is less well defined. The preparations of the Chl b‐water adduct are unstable. The Chl b‐water adduct absorption band maximum is at 683 nm. The CD signal of the Chl a‐water adduct is about 200‐fold the CD of the Chl b‐water adduct. We could not orient the Chl b‐water adducts by flow, which suggests that the adducts are small or disordered.
Photodynamic Effects of Hypericin on Lipid Peroxidation and Antioxidant Status in Melanoma Cells
Authors: Hadjur Christophe , Richard Marie‐Jeanne , Parat Marie‐Odile , Jardon Pierre , Favier Alain
Published: January 2008

Photodynamic‐induced cytotoxicity by hypericin (HYP) was studied on three human melanoma cell lines: one pigmented cell line (G361) and two amelanotic cell lines (M18 and M6). No significant variation in the rate of uptake and in the maximum level of HYP incorporation for the different cells was observed. In the dark, no cytotoxicity was observed in the range0–10−6M HYP for the three cell lines. Amelanotic cells were found to be more sensitive than pigmented cells to irradiation of HYP with visible light (Λ > 590 nm). In addition, for the three cell lines HYP‐induced photocytotoxicity was found to be drug‐dose and light‐dose dependent. Under the conditions used, thiobarbituric acid‐reacting substances (TBARs) were significantly increased in amelanotic cells after irradiation (P < 0.0001). By contrast, the amount of TBARS remained unchanged in pigmented cells. Antioxidant defenses including enzymes and glutathione (GSH) were assayed before and after HYP photosensitization. Significantly increased total SOD activity was observed after photosensitization for amelanotic cells (P < 0.05), while glutathione peroxidase (GSHPx) and catalase (Cat) activities but also GSH levels were significantly decreased (P < 0.01). In pigmented cells a significantly increased Cat activity was found (P < 0.05), whereas GSHPx was unaffected after irradiation. It can be inferred that (a) HYP may be an effective PDT agent for melanoma and (b) there is a relationship between melanin content and sensitivity to HYP phototoxicity in human melanoma cells.