bluuebunny/crossref_metadata_2025 huggingface dataset:
UNDERSTANDING PHOTOSYNTHESIS, PIGMENT AND GROWTH RESPONSES INDUCED BY UV‐B AND UV‐A IRRADIANCES
Authors: Middleton Elizabeth M. , Teramura Alan H.
Published: July 2010

Abstract—Plant response to UV‐B (0.290–0.320 μm) irradiation in controlled environments has been difficult to assess, possibly because plants also respond to UV‐A (0.320–0.400 μm) and visible radiation. Photosynthetic dysfunction is often reported, but effects on photosynthetic pigments have been equivocal. Because UV‐A/blue radiation is involved in pigment synthesis, the experimental UV‐A irradiation was controlled and this study was conducted under high ambient photosynthetic photon flux (mid‐day PPF > 1400 pmol m –2 s–1). Two biologically effective UV‐B irradiances (10.7 and 14.1 kJ m‐2 day‐I) were utilized and the UV‐A irradiances were matched in controls (˜5 and 9 kJ m‐2 day‐1). Normal and two mutant pigment isolines (chlorophyll‐deficient, flavonoid‐deficient) of soybean cultivar Clark were utilized for comparisons. Many pigmedgrowth variables exhibited a statistical interaction between spectral quality and quantity. UV‐A/blue photoregulation was demonstrated in the UV‐A controls. The pigmentlgrowth pattern observed at the lower UV‐B irradiance was interpreted as a photosystem II response similar to shade adaptation, suggesting phytochrome involvement in UV‐B irradiation responses. On the other hand, two variables most commonly observed to manifest UV‐B‐induced effects—decreased photosynthesis and increased leaf flavonoid content—exhibited no interactions due to UV exposure or spectral quality. In general, the observed response patterns indicated either moderation of UV‐B‐induced responses by UV‐A/blue radiation, or coaction between them, and provides an explanation for the common failure to demonstrate fluence‐related responses in UV‐B experiments.
COMPUTER SIMULATION OF EXCITON JUMPING STATISTICS AND ENERGY FLOW IN C‐PHYCOCYANIN OF ALGAE Agmenellum quadruplicatum IN THE PRESENCE OF TRAPS
Authors: Demidov Andrey A. , Borisov Alexander Yu.
Published: July 2010

Abstract—Energy migration has been studied in C‐phycocyanin (C‐PC) rods with traps located in the terminal trimer disc, using the Monte Carlo method and the system of differential equations. It has been found that jump time statistics can be described by the function F = C(t/)exp(‐t/ < to>), where C is the constant, t and < t0 > are, respectively, the exciton jump time and its averaged value for chromophores of the corresponding spectral types (α84, β84 or β155). The values < t0 > were calculated for the cases of C‐PC monomers, trimers and higher associates.

The C‐PC model, which consists of three hexamers with traps located in the β84 chromophores of the peripheral trimer, was examined. It was found that the total efficiency of excitation capturing, øtr, exceeds 90%, provided “local” quantum yield of energy trapping ø0 > 10%. The ø0 value influences both the excitation lifetime (τ) and the mean number of excitation jumps (Niump) before its conversion. For the ø0= 100% and 10%, the corresponding lifetimes and numbers of jumps were calculated to be τ= 75 and 155 ps and Njump= 105 and 222 jumps, respectively.

The dynamics of excitation redistribution along the C‐PC rods and the fluorescence kinetics for various ø0 values were calculated for C‐PC chromophores excited by a +, and the correlation between these processes and ø0, was disclosed. The transient processes of excitation redistribution were shown to proceed within a time period t < 30 ps.
INDUCTION and DISAPPEARANCE OF THYMINE DIMERS IN HUMAN SKIN EXPOSED TO UVB RADIATION: FLOW CYTOMETRIC MEASUREMENTS IN REPLICATING and NONREPLICATING EPIDERMAL CELLS
Authors: Berg Rob J. W. , Bueger Susan C. de , Guikers Kees , Weelden Huib van , Vloten Willem A. van , Leun Jan C. van der , Gruul Frank R. de
Published: July 2010

We have earlier reported on determining UV‐induced DNA damage in murine epidermal cell suspensions by flow cytometric analysis of the fluorescence from a fluorescein isothiocyanate‐labeled antibody (H3) directed against thymine dimers (T><T). Here we present an optimization of the technique for analysis of epidermal cell suspensions from 4 mm biopsies from human skin. Cells with different DNA contents can easily be distinguished in flow cytometry by the intensity of DNA‐specific 7‐amino‐actinomycin D fluorescence. Genuine G2‐M‐phase cells can further be distinguished from cell doublets by pulse‐shape discrimination. Thus, T><T levels in individual cells with different DNA contents (i.e. G0‐G1, S or G2‐M phases) can be determined after in vivo exposure of human skin to environmentally relevant UVB (280–315nm) doses. The method was applied to measure the decrease of T><T‐specific fluorescence at 24 h after exposure was 46% (ranging between 16% and 66%) for the G0‐G1 cells and 70% (ranging between 37% and 100%) for the S + G2‐M cells. The difference was statistically highly significant. Determination of individual DNA repair capacities with this method can become a convenient diagnostic tool for patients with DNA repair disorders, or it may even be used to identify individuals with low repair proficiencies and increased risk of developing skin cancers.
BILIRUBIN PHOTOTOXICITY TO HUMAN CELLS BY GREEN LIGHT PHOTOTHERAPY in vitro
Authors: Böhm F. , Drygalla F. , Charlesworth P. , Böhm K. , Truscott T. G. , Jokiel K.
Published: July 2010

Phototherapy of newborn infants with blue or green light is the most common treatment of neonatal hyperbilirubinemia. Using bilirubin bound to human lymphoid and basal skin cells we obtained the green light dose dependency of the bilirubin phototoxicity to these cell types. Cells (3–5× 106/mL) were incubated with bilirubin complexed to human serum albumin (final concentrations 340 μM bilirubin, 150 μM albumin). Under these conditions all cells showed maximum binding of bilirubin. Irradiation with broadband green light (Λmax= 512 nm) over 24 h led to a light dose‐dependent population of cells, which contained no bilirubin on the cell membrane as determined by Nomarski interference microscopy. The light‐induced mechanism of the disappearance of bilirubin caused lethal membrane damage to the cells (trypan blue exclusion test). The cell kill rate increased with the irradiation dose and with the fraction of cells with no bilirubin. When 90% of lymphoid cells were bilirubin free, 46% of them were dead (using 480 J cm−1 green light). Similar results were obtained with basal skin cells. In addition, bilirubin‐induced damage of cell membrane and nuclear membrane was also shown by transmission electron microscopy. Bilirubin (340 μM) in the dark led to 5% of the cells being killed. Basal skin cells bind 2.5 times more bilirubin molecules than lymphoid cells and showed a different bilirubin disappearance. Irradiation of bilirubin in carbon tetrachloride with 514.5 nm laser light showed generation of singlet oxygen via its luminescence at 1270 nm. These results demonstrate that green light phototherapy of hyperbilirubinemia may cause both skin and immune system damage.
PHOTOREACTION OF 5‐METHOXYPSORALEN WITH THYMIDINE and THE THYMINE MOIETY OF ISOLATED and Saccharomyces cerevisiae DNA. CHARACTERIZATION and MEASUREMENT OF THE TWO cis‐syn FURAN‐SIDE MONOCYCLOADDUCTS
Authors: Anselmino Catherine , Averbeck Dietrich , Cadet Jean
Published: July 2010

The photoreaction of the furan‐side moiety of 5‐methoxypsoralen (5‐MOP) with thymidine used as a DNA model compound was investigated in the dry state. Under these conditions, two main fluorescent photoadducts were formed and isolated by HPLC. The two modified nucleosides were characterized as the twocis‐syndiastereoisomers of furan‐side monoadducts of 5‐MOP to thymidine on the basis of spectroscopic measurements including UV, fluorescence,1H‐NMR and circular dichroism analysis. The identification and quantification of the latter photoproducts within naked DNA exposed to photoexcited 5‐MOP were achieved by enzymatic digestion completed by HPLC separation and fluorescence detection. Similarly, the twocis‐synfuran‐side monoadducts were found to be formed in the DNA ofSaccharomyces cerevisiaecells after incubation with 5‐MOP and subsequent exposure to 365 nm at an incident dose of 38.4 kJ m−2. Under these conditions, the rate of induction of two diastereoisomeric photoadducts was as low as one modification per 106and 2 × 105bases, respectively.
VERTICAL DISTRIBUTION OF PHYTOPLANKTON IN COASTAL WATERS and ITS DETECTION BY BACKSCATTERING MEASUREMENTS
Authors: Piazena H. , Häder D.‐P.
Published: July 2010

Remote sensing using backscattering data sampled by satellite or airplane is a promising method of monitoring the content of phytoplankton in marine waters. Usually the analysis of the organism concentration is based on the ratio of signals in suitable spectral channels. However, the attenuation of the optical signals involved in the analysis does not only depend on the concentration of organisms but also on their vertical distribution in the water column, on the water type and on the individual content of chlorophyll and accessory pigments in the species that establish the population. The present paper discusses the results of direct measurements of both vertical distribution of phytoplankton concentration and of solar spectral irradiation scattered and absorbed in different waters of the Baltic Sea and the Mediterranean. From these measurements relations are derived between backscattered spectral signals, water type and the vertical distribution of the organisms. The content of organisms in the column is consistently underestimated if no additional information on water type and vertical distribution of the organisms is taken into account. These data can be estimated from backscattering data of high resolution. In addition, a calibration and adaptation of the remote sensing data by ground truth is necessary to determine the optical properties of different species.
VISIBLE LIGHT ANAEROBIC PHOTOCONVERSION OF TYROSINE SENSITIZED BY RIBOFLAVIN. CYTOTOXICITY ON MOUSE TUMORAL CELLS
Authors: Silva Eduardo , Fürst Sonia , Edwards Ana M. , Becker M. Ines , Ioannes Alfredo E. De
Published: July 2010

The anaerobic phototransformation of tyrosine under visible light sensitized by riboflavin is reported. The cytotoxicity of the anaerobic photoproducts on in vitro‐cultured myeloid mouse tumoral cells was demonstrated. A radical mechanism is proposed. Dityrosine was identified as one of the main anaerobic photoproducts by using absorption, emission and 1H‐NMR spectra.
THE MOLECULAR CHAPERONE FUNCTION OF α‐CRYSTALLIN IS IMPAIRED BY UV PHOTOLYSIS
Authors: Borkman Raymond F. , McLaughlin Jennifer
Published: July 2010

Buffer solutions of the lens protein γ‐crystallin and the enzymes aldolase and liver alcohol dehydrogenase became turbid and formed solid precipitate upon exposure to an elevated temperature of 63°C or to UV radiation at 308 nm. When α‐crystallin was added to the protein solutions in stoichiometric amounts, heat or UV irradiation did not cause turbidity, or turbidity developed much less rapidly than in the absence of α‐crystallin. Hence, normal α‐crystallin functioned as a molecular chaperone, providing protection against both UV and heat‐induced protein aggregation. When α‐crystallin was preirradiated with UV at 308 nm, its ability to function as a chaperone vis‐a‐vis both UV and heat‐induced aggregation was significantly impaired, but only at relatively high UV doses. A major effect of preirradiation of α‐crystallin was to cause interpeptide crosslinking among the αA2 and αB2 subunits of the α‐crystallin macromolecule. In our experiments α‐crystallin was exposed to UV doses, which resulted in 0, 50 and 90% crosslinking as judged by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. α‐Crystallin samples that were 50% and 90% crosslinked gave chaperone protection, which was increasingly impaired relative to unirradiated α‐crystallin. The results are consistent with the notion that UV irradiation of α‐crystallin results in loss of chaperone binding sites.
PHOTOCHEMICAL REACTIONS OF AZIDOCOUMARINS
Authors: Feng Kesheng , Mahdavi‐Anary Farah , Partch Richard E. , Li Yuzhuo
Published: July 2010

Abstract—Photochemical reactions of 6‐azidocoumarin and 7‐azido‐4‐methylcoumarin in the presence of secondary amines have been investigated for their potential applications in photoaffinity labeling. It was found that the singlet nitrene generated from 6‐azidocoumarin isomerized to a dehydroazepine intermediate that reacted with an amine to yield two isomeric adducts. Photolysis of 7‐azido‐4‐meth‐ylcoumarin, in contrast, gave a triplet nitrene that abstracted hydrogen atoms from secondary amine molecules to form 7‐amino‐4‐methylcoumarin as the major product. The difference in the intersystem crossing rate between the two compounds originates from the azido position relative to the carbonyl group. Because of its ability to form a covalent linkage with a nucleophile, 6‐azidocoumarin is deemed to have a greater potential as a photoaffinity label than 7‐azido‐4‐methylcoumarin.
INFLUENCE OF COMBINED AC‐DC MAGNETIC FIELDS ON FREE RADICALS IN ORGANIZED and BIOLOGICAL SYSTEMS. DEVELOPMENT OF A MODEL and APPLICATION OF THE RADICAL PAIR MECHANISM TO RADICALS IN MICELLES
Authors: Scaiano J. C. , Cozens F. L. , Mohtat N.
Published: July 2010

Abstract— The effect of an alternating current (AC) magnetic field (MF) on radical behavior is identical to that exerted by a direct current (DC) field of the same instantaneous strength provided that the frequency is low enough in comparison with radical pair dynamics. This criterion is easily met by environmental fields. In general, combined AC/DC fields will lead to increased radical concentrations and oscillating free radical concentrations. Interestingly, the frequency of oscillation for radical concentration seldom follows exactly the pattern of the external AC component of the MF. Even the simple case of an AC‐only field at 60 Hz can lead to oscillations in radical concentrations at 120 Hz. The concentration time dependence patterns can be even more complex when the singlet and triplet levels of the radical pair are not degenerate. Further, the effects can change dramatically depending upon the absolute and relative values of the AC and DC components, thus providing a possible explanation for MF windows for certain effects reported experimentally. Effects on the average radical concentration are probably relevant only for fields higher than about 0.1 gauss. Oscillating radical concentrations may influence signal transduction processes or other cellular mechanisms; at the present time there is not enough knowledge available to establish a reasonable threshold for these types of effects. This contribution aims at providing a solid foundation to guide the experimentalist in the design of meaningful experiments on the possible role of MF perturbations of radical chemistry on biological response.
AUTOFLUORESCENCE SPECTROSCOPY OF OPTICALLY TRAPPED CELLS
Authors: Konig1 Karsten , Liu1 Yagang , Sonek1 Greg J. , Berns Michael W. , Tromberg Bruce J.
Published: July 2010

Abstract— Cellular autofluorescence spectra were monitored in a single‐beam gradient force optical trap (“optical tweezers”) in order to probe the physiological effects of near infrared and UVA (320–400 nm) microirradiation. Prior to trapping, Chinese hamster ovary cells exhibited weak UVA‐excited autofluorescence with maxima at 455 nm characteristic of β‐nicotinamide adenine dinucleotide (phosphate) emission. No strong effect of a 1064 nm NIR microbeam on fluorescence intensity and spectral characteristics was found during trapping, even for power densities up to 70 MW/cm2 and radiant exposures of 100 GJ/cm2. In contrast to the 1064 nm trap, a 760 nm trapping beam caused a two‐fold autofluorescence increase within 5 min (about 20 GJ/cm2). Exposure to 365 nm UVA (1 W/cm2) during 1064 nm trapping significantly altered cellular autofluorescence, causing, within 10 min, a five‐fold increase and a 6 nm red shift versus initial levels. We conclude that 1064 nm microbeams can be applied for an extended period without producing autofluorescence changes characteristic of alterations in the cellular redox state. However, 760 nm effects may occur via a two‐photon absorption mechanism, which, in a manner similar to UVA exposure, alters the redox balance and places the cell in a state of oxidative stress.
REDUCTION OF INTERFERON‐γ AS A CRITICAL MECHANISM BY WHICH ULTRAVIOLET RADIATION PREVENTS TUMOR REJECTION
Authors: Gensler Helen L. , Simpson Jeannette , Gerrish Kevin , Gilmore James
Published: July 2010

Abstract— Mice irradiated with UVB, unlike nonirradiated mice, are highly susceptible to syngeneic, immunogenic tumors induced by UVB irradiation or by chemicals. We postulated that UV induced susceptibility to immunogenic tumors results from a reduction in host capacity to generate an interferon (IFN)‐γ immune response to tumor antigens. Shaved BALB/c mice were exposed to 6 × 105 J m‐2 of UVB radiation delivered intermittently over 12 weeks. The UVB‐irradiated and nonirradiated mice received intradermal injections of UVM12 or BP2 tumor cells. After 0, 1.5, 3, 7 or 21 days, draining lymph nodes were excised. Lymph node cells were incubated with UVM12 or BP2 cells that had received 2.5 Gy of γ‐radiation. After 48 h in culture, supernatants were analyzed for IFN‐γ content by enzyme‐linked immunosorbent assay and cellular RNA was extracted for mRNA detection by reverse transcriptase‐polymerase chain reaction analysis. At 7 days after tumor injection, draining lymph node cells from nonirradiated control mice secreted significant levels of IFN‐γ and contained at least 0.0729 amol of IFN‐γ mRNA/μg cDNA upon in vitro exposure to γ‐irradiated tumor cells. Draining lymph node cells removed from UV‐irradiated mice contained only 18% as much IFN‐γ mRNA and secreted little or no IFN‐γ when exposed to γ‐irradiated tumor cells. A single injection of antibody directed against murine IFN‐γ rendered normal mice as susceptible as UV‐irradiated mice to BP2 tumor cells. Thus, chronic UV irradiation leads to an inability of host tumor draining lymph node cells to mount an IFN‐γ response to tumor antigens. Reduced levels of IFN‐γ at the time of early exposure to tumor antigens can lead to tumor susceptibility and can account for the inability of UV‐irradiated mice to reject antigenic tumors.
CELLULAR FLUORESCENCE OF THE ENDOGENOUS PHOTOSENSITIZER PROTOPORPHYRIN IX FOLLOWING EXPOSURE TO 5‐AMINOLEVULINIC ACID
Authors: Steinbach Pia , Wedmgandt Helmut , Baumgartner Reinhold , Kriegmair Martin , Hofstädter Ferdinand , Knüchel Ruth
Published: July 2010

Abstract— Supplying 5‐aminolevulinic acid (ALA), a precursor in the biosynthetic pathway to heme from an external source leads to an accumulation of the endogenous fluorescent photosensitizer protoporphyrin IX (PPIX). Following instillation of ALA in the urinary bladder neoplastic tissue can be discerned by fluorescence cystoscopy or treated by illumination with light of an appropriate wavelength. In order to provide a biological rationale for the clinical findings, we have analyzed the capacity of three different cell lines to accumulate PPIX by flow cytometry. Three different urothelial cell lines, normal fibroblasts and endothelial cells were exposed to ALA under varying conditions. Urothelial cell lines J82 and RT4, derived from malignancies of the bladder displayed fluorescence intensities 9‐ and 16‐fold, respectively, above the fluorescence level of the normal urothelial cell line HCV29. Human umbilical cord endothelial cells fluoresced moderately while the fibroblast cell line Nl exhibited a fluorescence level comparable to those of the cancer cells. Fluoresence increased with increasing cell density and was also dependent on the growth of cells as monolayers or multicellular spheroids. Increasing ALA concentrations led to saturation of fluorescence after 4 h of incubation at cell type‐specific fluorescence levels obtained at different ALA concentrations. Continuous incubation in medium containing serum resulted in a linear rise of fluorescence during the first 4 h, which was followed by a saturation period (8–24 h) and a renewed rise. In the case of serum depletion, fluorescence intensities were significantly higher and increased linearly during the entire 48 h incubation period. By replacing serum with albumin, it could be shown that the emission of PPIX into the medium in the presence of serum is mainly caused by this protein. The ALA‐induced fluorescence was predominantly perinuclear after 4 h of incubation and relocated toward the cell membrane after prolonged incubation. This study demonstrated the complexity of factors influencing the ALA‐induced fluorescence and should stimulate further research in this field.
pH Effects on the Spectroscopic and Photochemical Behavior of Enoxacin: A Steady‐State and Time‐Resolved Study
Authors: Sortino S. , Guidi G. De , Giuffrida S. , Monti S. , Velardita A.
Published: July 2010

The spectroscopic and photochemical behavior of Enoxacin (ENX), 1‐ethyl‐6‐fluoro‐1,4‐dihydro‐4‐oxo‐7‐(1‐piperazinyl)‐1,8‐naphthyridine‐3‐carboxylic acid, has been investigated in aqueous solutions between pH 3.5 and pH 12. The absorption and emission properties of ENX are strongly affected by pH. The fluorescence quantum yield, 4 x 10−3 at pH 3.5, increases by a factor of two on going to neutral pH while a strong reduction is observed at alkaline pH. The photodegradation quantum yield also depends on pH, being maximum in neutral conditions (ca 0.04). Nanosecond flash photolysis experiments confirm that the yield of absorbing transients is maximum at neutral pH while it decreases to zero at acid and alkaline pH. These results indicate that both the dissociation of the carboxylic group and the protonation of the piperazinyl residues are key steps for the formation of the photochemically active form of ENX. Loss of F− by heterolytic cleavage of the C–F bond is proposed to occur from the triplet state of the zwitterion with formation of a carbocation. A path for the evolution of this intermediate to the final product is also proposed.
Porphyrins and Related Compounds as Photoactivatable Insecticides I. Phototoxic Activity of Hematoporphyrin Toward Ceratitis capitata and Bactrocera oleae
Authors: Amor T. Ben , Tronchin M. , Bortolotto L. , Verdiglione R. , Jori G.
Published: July 2010

The photodynamic sensitizer hematoporphyrin (HP) IX was efficiently accumulated by Ceratitis capitata (Mediterranean fruit fly) and Bactrocera oleae (olive fly) when the insects were fed with a sugar/protein bait containing micromolar amounts of porphyrin. Hematoporphyrin appeared to be mainly accumulated in the midgut, Malpighian tubes, adipose tissue and cuticle and was gradually cleared from the organism in a 24–48 h time interval. Exposure of the HP‐fed flies to light mimicking the solar spectrum caused a decrease in the survival whose extent was modulated by the HP concentration in the bait, the irradiation fluence rate and the total light dose. For 8 μmol/mL HP in the bait 100% mortality during 1 h exposure to light was obtained using a fluence rate of 1220 μE s−1 m−2 for C. capitata and 2080 μE s−1 m−2 for B. oleae. The latter fly was somewhat less photosensitive than C. capitata possibly owing to the smaller amount of ingested HP and/or darker pigmentation. Studies are in progress in order to extend these investigations from the laboratory to the field scale.
Photogenotoxicity of Fluoroquinolones in Chinese Hamster V79 Cells: Dependency on Active Topoisomerase II
Authors: Snyder Ronald D. , Cooper Curt S.
Published: July 2010

Abstract— The Chinese hamster V79 lung cell in vitro micronucleus assay was adapted to detect and quantify phototoxicity and photogenotoxicity of fluoroquinolones. Using this assay, the quinolones were ranked in terms of decreasing phototoxicity: clinafloxacin > lomefloxacin, sparfloxacin > trovafloxacin, nalidixic acid, ofloxacin, ciprofloxacin > enoxacin, norfloxacin. This rank order agrees well with published studies utilizing various other phototoxicity models and establishes this approach as a fast and sensitive way to characterize the phototoxic potential of quinolones. Nearly complete inhibition of phototoxicity was observed if the cells were pretreated for as little as I min with 10–20 mM sodium azide prior to the addition of quinolone. An identical azide effect was seen in unirradiated quinolone‐and etoposide‐treated cells. These findings are consistent with a model in which sodium azide renders DNA topoisomerase II catalytically inactive. In this state, topoisomerase II cannot initiate DNA strand cleavage and the DNA/topoisomerase complex becomes insensitive to quinolones and other topoisomerase II inhibitors. The fact that azide reduces both UV‐dependent and UV‐independent toxicity and clastogenicity strongly suggests a common mechanism of toxicity dependent on the formation of topoisomerase‐induced DNA double‐strand breaks.
Photooxidized Products of Recombinant αA‐Crystallin and W9F Mutant
Authors: Dhir Prajay , Akhtar Nila J. , Sun Tian‐Xiao , Liang Jack J.‐N.
Published: July 2010

Abstract— Human lenses contain many photosensitizers that absorb light at wavelengths above 300 nm, most notably UVA light (320–400 nm). Kynurenine (Kyn) and 3‐hydroxykyn‐urenine (HK), two of the best‐known photosensitizers in the human lens, may play a significant role in photooxidation‐related changes in lens proteins, such as conformational change and aggregation. In vitro irradiation experiments with proteins indicate that the Trp residue (with maximal absorption at 295 nm) is more susceptible to photooxidation by UVB light (280–320 nm) than by UVA light, but most UVB light below 300 nm is screened by the cornea and little reaches the lens, especially the nuclear region where nuclear color develops. Therefore, if photooxidation is an important contributor to nuclear color or nuclear cataract, it must arise from a photosensitized reaction. In the present study, we use recombinant αA‐and its Trp‐deficient mutant W9F as models to study the effects of UVA irradiation in the presence of HK or Kyn and of UVB (300 nm) irradiation on α‐crystallins. αA‐crystallin showed a large decrease in Trp fluorescence and a large increase in non‐Trp (blue) fluorescence after the HK‐sensitized or 300 nm photooxidation. For the W9F mutant, a smaller decrease in protein fluorescence (Λex at 280 nm) and a smaller increase in blue fluorescence than for the wild‐type αA‐crystallin were observed. A decrease in the near‐UV CD was also observed for both photooxidized αA and the W9F mutant. The effect of Kyn sensitization is smaller than that of HK sensitization. A study of chaperone‐like activity indicated that only 300 nm photooxidized αA and the W9F mutant increased the ability to protect insulin from dithiothreitol‐induced aggregation. Thus, sensitized photooxidation can occur in amino acids other than Trp by UVA in the presence of HK or Kyn with effects similar to, albeit smaller than, those of direct UVB (300 nm) photooxidation.
Receptor‐Mediated Targeting of Phthalocyanines to Macrophages Via Covalent Coupling to Native or Maleylated Bovine Serum Albumin
Authors: Brasseur Nicole , Langlois Réjean , Madeleine Carole La , Ouellet Rene , van Lier Johan E.
Published: July 2010

Abstract— Targeted delivery of aluminum tetrasulfophthalocyanine (AlPcS4) to the scavenger receptor of macrophages, via coupling to maleylated bovine serum albumin (mal‐BSA), was explored as a means to improve photodynamic efficacy. The AlPcS4 was covalently coupled to BSA (9:1 molar ratio) via one or two sulfonamide‐hexanoic‐amide spacer chains, followed by treatment with maleic anhydride to yield the mal‐BSA‐phthalocyanine conjugates. The latter were tested for singlet oxygen production, receptor‐mediated cell uptake and phototoxicity toward J774 cells of macrophage origin and nonphagocytic EMT‐6 cells. Cell uptake of 125I‐mal‐BSA showed specific binding for J774 cells but not for EMT‐6 cells. Competition studies of the conjugates with 125I‐mal‐BSA showed that coupling of AlPcS4 to BSA resulted in recognition of the conjugate by the scavenger receptor, whereas coupling to mal‐BSA further enhanced its binding affinity. This suggests that affinity for the scavenger receptor is related to the overall negative charge of the protein. Phototoxicity of the conjugates toward J774 cells paralleled their relative affinity, with mal‐BSA‐AlPcS4 coupled via two spacer chains showing the highest activity. The conjugates were less phototoxic toward the EMT‐6 cell line. The activities in both cell lines of all conjugated AlPcS4 preparations were, however, lower than that of the free disulfonated AlPcS2. Possible implications for the in vivo use of protein‐photosensitizer conjugates to target selectively various macrophage‐associated disorders is discussed.
Dependence of Fibroblast Autofluorescence Properties on Normal and Transformed Conditions. Role of the Metabolic Activity
Authors: Croce A. C. , Spano A. , Locatelli D. , Barni S. , Sciola L. , Bottiroli G.
Published: July 2010

Abstract— The dependence of autofluorescence properties on the metabolic and functional engagement and on the transformation condition was studied on single cells. Normal Galliera rat fibroblasts at low subculture passage (cell strain), at high subculture passage (stabilized cell line), and transformed ceil line derived from a rat sarcoma were used as a cell model. The study was performed by microspectrofluorometric and fluorescence imaging technique. The autofluorescence properties of cells were studied by excitation at two wavelengths, namely 366 nm and 436 nm, that are known to favor the emission of different fluorophores. Spectral shape analysis indicated that under excitation at 366 nm autofluorescence is ascribable mainly to coenzyme molecules, particularly to reduced pyridine nucleotides, while under excitation at 436 nm, flavin and lipopigment emission is favored. The energetic metabolic engagement of the different cell lines was analyzed in terms both of parameters related to anaerobicaerobic pathways (biochemical assay) and of mitochondrial features (supravital cytometry). The results showed that the cell strain and the stabilized and transformed cell lines can be distinguished from one another on the basis of both overall fluorescence intensity and the relative contributions of spectral components. These findings indicated a relationship between autofluorescence properties and energetic metabolism engagement of the cells that, in turn, is dependent on the proliferative activity and the transformed condition of the cells. In that it is a direct expression of the energetic metabolic engagement, autofluorescence can be assumed as an intrinsic parameter of the cell biological condition, suitable for diagnostic purposes.
An Insight into the Mechanisms of the Phototoxic Response Induced by Cyamemazine in Cultured Fibroblasts and Keratinocytes¶
Authors: Morliére Patrice , Haigle Josiane , Aissani Karim , Fillpe Paulo , Silva João Nuno , Santus René
Published: July 2010

The phototoxicity of cyamemazine (CMZ, Tercian®), a neuroleptic of the phenothiazine family, has recently been reported in humans. CMZ has an absorbance maximum at 267 nm (molar absorptivity, 25800 M−1 cm−1) but a weaker molar absorptivity in the ultraviolet A (UV‐A) region. CMZ exhibits a fluorescence with maximum emission at 535 nm and a quantum yield of 0.11. CMZ is a powerful photosensitizing agent toward HS 68 human skin fibroblasts and NCTC 2544 keratinocytes. At a UV‐A radiation dose of 10 J/cm2, innocuous to cells in the absence of CMZ, the LD50 (lethal dose corresponding to 50% killing) are 0.5 and 1 μM for the fibroblasts and the keratinocytes, respectively, after overnight incubation with the drug. Short incubation times do not significantly alter the LD50. The CMZ‐induced phototoxicity is accompanied by lipid membrane peroxidation consistent with the amphiphilic character of this photosensitizer. Keratinocytes are an order of magnitude less sensitive to the photosensitized lipid peroxidation than fibroblasts. Microspectrofluorometry reveals that lysosomal membranes are major sites of CMZ incorporation into the two cell lines because a Forster‐type resonance energy transfer process occurs from CMZ to LysoTracker Red DND99 (LTR), a specific fluorescent probe of lysosomal membranes. The CMZ‐photosensitized destruction of LTR demonstrates that CMZ retains its photosensitizing capacity after its lysosomal uptake.
Epidermal Lignin Deposition in Quinoa Cotyledons in Response to UV‐B Radiation¶
Authors: Hilal Mirna , Parrado María Francisca , Rosa Mariana , Gallardo Miriam , Orce Luis , Massa Eddy Marta , González Juan Antonio , Prado Fernando Eduardo
Published: July 2010

UV‐B radiation (280–320 nm) is harmful to living organisms and has detrimental effects on plant growth, development and physiology. In this work we examined some mechanisms involved in plant responses to UV‐B radiation. Seedlings of quinoa (Chenopodium quinoaWilld.) were exposed to variable numbers of UV‐B radiation doses, and the effect on cotyledons was studied. We analyzed (1) cotyledons anatomy and chloroplasts ultrastructure; (2) peroxidase activity involved in the lignification processes; and (3) content of photosynthetic pigments, phenolic compounds and carbohydrates. Exposure to two UV‐B doses induced an increase in the wall thickness of epidermal cells, which was associated with lignin deposition and higher activity of the peroxidase. The chloroplast ultrastructure showed an appearance typical of plants under shade conditions, likely in response to reduced light penetration into the mesophyll cells due to the screening effect of epidermal lignin deposition. Exposure to UV‐B radiation also led to (1) enhancement in the level of phenolics, which may serve a protective function; (2) strong increase in the fructose content, a fact that might be related to higher requirement of erythrose‐4P as a substrate for the synthesis of lignin and phenolics; and (3) reduction in the chlorophyll concentration, evidencing alteration in the photosynthetic system. We propose that the observed lignin deposition in epidermal tissues of quinoa is a resistance mechanism against UV‐B radiation, which allows growing of this species in Andean highlands.
Radiative Relaxation Quantum Yields for Synthetic Eumelanin¶
Authors: Meredith Paul , Riesz Jennifer
Published: July 2010

We report absolute values for the radiative relaxation quantum yield of synthetic eumelanin as a function of excitation energy. These values were determined by correcting for pump beam attenuation and emission reabsorption in both eumelanin samples and fluorescein standards over a large range of concentrations. Our results confirm that eumelanins are capable of dissipating >99.9% of absorbed UV and visible radiation through nonradiative means. Furthermore, we have found that the radiative quantum yield of synthetic eumelanin is excitation energy dependent. This observation is supported by corrected emission spectra, which also show a clear dependence of both peak position and peak width on excitation energy. Our findings indicate that photoluminescence emission in eumelanins is derived from ensembles of small chemically distinct oligomeric units that can be selectively pumped. This hypothesis lends support to the theory that the basic structural unit of eumelanin is oligomeric rather than heteropolymeric.
Decreased Levels of (6–4) Photoproduct Excision Repair in Hybrid Fish of the Genus Xiphophorus¶
Authors: Mitchell David L. , Nairn Rodney S. , Johnston Dennis A. , Byrom Michelle , Kazianis Steven , Walter Ronald B.
Published: July 2010

Selected hybridization in the fish genus Xiphophorus has been used for many years to study the genetics of malignant melanoma. Because DNA damage caused by ultraviolet radiation is implicated in the etiology of sunlight‐induced melanoma, the heritability of mechanisms that mitigate DNA damage is a matter of some interest. We examined nucleotide excision repair of the two major types of DNA‐damage induced by sunlight; the cyclobutane pyrimidine dimer (CPD) and the pyrimidine (6–4) pyrimidone dimer [(6–4)PD]. In most cases, removal of the (6–4) PD was more rapid than the CPD, and in many cases, the F1 hybrid showed reduced repair efficiency compared with the parental species. These data demonstrate reduced function in multienzyme hybrid systems and provide molecular support for potential reduced fitness in hybrid fish under conditions of environmental stress.
Biodistribution Assessment of a Lutetium(III) Texaphyrin Analogue in Tumor‐bearing Mice Using NIR Fourier‐transform Raman Spectroscopy¶
Authors: Synytsya Alla , Król Vladimír , Matejka Pavel , Poučkovó Pavla , Volka Karel , Sessier Jonathan L.
Published: July 2010

The use of near‐infrared (NIR)‐excited Fourier‐transform (FT) Raman spectroscopy as a technique for evaluating the extent of photosensitizer localization in tumor (human pancreatic adenocarcinomas)‐bearing mice has been tested using lutetium(III) texaphyrin analogue Ln‐T2B2Tex. The complex was injected subcutaneously in the form of three injections given during the course of 3 days. The kinetics of biodistribution were then followed over a time scale of 1–6 days. The NIR‐FT‐Raman spectra of tissue samples obtained from the xenographic tumor, muscle, heart, brain, liver, spleen, kidney and blood were recorded and used to identify the presence of Lu‐T2B2Tex in these tissues. Five Raman sensitizer markers were used to estimate the relative content of Lu‐T2B2Tex in tumor at various postinjection times. UV‐Visible (Vis) absorption spectroscopic detection of this sensitizer in tissue extracts was applied as a conventional method. Both spectroscopic methods were in good agreement with each other and confirm that Lu‐T2B2Tex localizes well in tumor tissue. Maximal drug content was observed 3 days after the final injection. This time delay seems to be optimal for tumor irradiation in photodynamic therapy.
Torsion Potential Works in Rhodopsin¶
Authors: Yamada Atsushi , Yamato Takahisa , Kakitani Toshiaki , Yamamoto Shigeyoshi
Published: July 2010

We investigate the role of protein environment of rhodopsin and the intramolecular interaction of the chromophore in the cis‐trans photoisomerization of rhodopsin by means of a newly developed theoretical method. We theoretically produce modified rhodopsins in which a force field of arbitrarily chosen part of the chromophore or the binding pocket of rhodopsin is altered. We compare the equilibrium conformation of the chromophore and the energy stored in the chromophore of modified rhodopsins with those of native rhodopsins. This method is called site‐specific force field switch (SFS). We show that this method is most successfully applied to the torsion potential of rhodopsin. Namely, by reducing the twisting force constant of the C11=C12 of 11‐cis retinal chromophore of rhodopsin to zero, we found that the equilibrium value of the twisting angle of the C11=C12 bond is twisted in the negative direction down to about −80°. The relaxation energy obtained by this change amounts to an order of 10 kcal/mol. In the case that the twisting force constant of the other double bond is reduced to zero, no such large twisting of the bond happens. From these results we conclude that a certain torsion potential is applied specifically to the C11=C12 bond of the chromophore in the ground state of rhodopsin. This torsion potential facilitates the bond‐specific cis‐trans photoisomerization of rhodopsin. This kind of the mechanism is consistent with our torsion model proposed by us more than a quarter of century ago. The origin of the torsion potential is analyzed in detail on the basis of the chromophore structure and protein conformation, by applying the SFS method extensively.
Spatial Control of Reactive Oxygen Species Formation in Fibroblasts Using Two‐photon Excitation¶
Authors: King Brett A. , Oh Dennis H.
Published: July 2010

Two‐photon excitation (2PE) provides a means of generating reactive oxygen species (ROS) in cells and tissues with a high degree of spatial specificity. In cultured monolayers of human fibroblasts and fibroblast‐derived cells treated with the commonly used probe of ROS formation, 5‐(and 6)‐chloromethyl‐2′,7′‐dichlorodihydrofluorescein diacetate, acetyl ester (CM‐H2DCFDA), cells irradiated through a microscope objective with 150 fs near‐infrared laser pulses became highly fluorescent, reflecting intracellular ROS formation. The fluorescence intensity inside cells increased quadratically with the average power of radiation for pulsed excitation and was unchanged for continuous wave irradiation with the same average power of radiation for pulsed excitation and was unchanged for continuous wave irradiation with the same average power. Single fibroblasts embedded within dermal equivalents were also targeted in this manner and formed ROS, whereas neighboring unirradiated cells were spared. These results demonstrate that ROS can be generated intracellularly in skin cells using 2PE of the metabolic or oxidative products of CM‐H2DCFDA and that formation of ROS can be localized in both cell monolayers and in a tissue equivalent. This technique should be useful in understanding the response of whole tissues such as skin to local generation of ROS and may have applications in photodynamic therapy.
Riboflavin and UV‐Light Based Pathogen Reduction: Extent and Consequence of DNA Damage at the Molecular Level
Authors: Kumar Vijay , Lockerble Owen , Kell Shawn D. , Ruane Patrick H. , Platz Matthew S. , Martin Christopher B. , Ravanat Jean‐Luc , Cadet Jean , Goodrich Raymond P.
Published: July 2010

We are developing a technology based on the combined application of riboflavin (RB) and light for inactivating pathogens in blood products while retaining the biological functions of the treated cells and proteins. Virus and bacteria reduction measured by tissue culture infectivity or colony formation with UV light alone and in combination with RB yield equivalent results. The effects of RB as a sensitizing agent on DNA in white cells, bacteria and viruses in combination with UV light exposure have been evaluated. UV‐mediated DNA degradation in Jurkat T cells and leukocytes in plasma as measured by the FlowTACS assay was significantly increased in the presence of RB. Agarose gel electrophoretic analysis of DNA in Escherichia coli and leukocytes in plasma demonstrated enhanced DNA degradation in the presence of RB. UV light in combination with RB prevented the reactivation of lambda phage compared with samples irradiated in the absence of RB. UV‐mediated oxidative damage in calf thymus DNA was also enhanced in the presence of RB. These observations clearly demonstrate that the presence of RB and UV light selectively enhances damage to the guanine bases in DNA. These data also suggest that the type and extent of damage to DNA for virus in the presence of RB and light make it less likely to be repaired by normal repair pathways available in host cells.
Effects of Suplementary Ultraviolet‐B Irradiance on Maize Yield and Qualities: A Field Experiment¶
Authors: Gao Wei , Zheng Youfei , Slusser James R. , Heisler Gordon M. , Grant Richard H. , Xu Jianqiang , He Douliang
Published: July 2010

Stratospheric ozone depletion has caused an increase in the amount of ultraviolet‐B (UV‐B) radiation reaching the earth's surface. Numerous investigations have demonstrated that the effect of UV‐B enhancements on plants includes reduction in grain yield, alteration in species competition, susceptibility to disease and changes in plant structure and pigmentation. Many experiments examining UV‐B radiation effects on plants have been conducted in growth chambers or greenhouses. It has been questioned whether the effect of UV‐B radiation on plants can be extrapolated to field responses from indoor studies because of the unnaturally high ratios of UV‐B/ ultraviolet‐A radiation (320–400 nm) and UV‐B/photosynthetically active radiation (PAR) in many indoor studies. Field studies on UV‐B radiation effect on plants have been recommended to use the UV and PAR irradiance provided by natural light. This study reports the growth and yield responses of a maize crop exposed to enhanced UV‐B radiation and the UV‐B effects on aize seed qualities under field conditions. Enhanced UV‐B radiation caused a significant reduction in the dry matter accumulation and the maize yield in turn was affected. With increased UV‐B radiation the flavonoid accumulation in maize leaves increased and the contents of chlorophyll a, b and (a+b) of maize leaves were reduced. The levels of protein, sugar and starch of maize seed decreased with enhanced UV‐B radiation, whereas the level of lysine increased with enhanced UV‐B radiation.
Tryptophan Fluorescence in the Bacillus subtilis Phototropin‐related Protein YtvA as a Marker of Interdomain Interaction¶
Authors: Losi Aba , Ternelli Elena , Gärtner Wolfgang
Published: July 2010

The Bacillus subtilis protein YtvA, related to plant phototropins (phot), binds flavin mononucleotide (FMN) within the N‐terminal light, oxygen and voltage (LOV) domain. The blue light‐triggered photocycle of YtvA and phot involves the reversible formation of a covalent photoadduct between FMN and a cysteine (cys) residue. YtvA contains a single tryptophan, W103, localized on the LOV domain and conserved in all phot‐LOV domains. In this study, we show that the fluorescence parameters of W103 in YtvA‐LOV are markedly different from those observed in the full‐length YtvA. The fluorescence quantum yields are ca 0.03 and 0.08, respectively. In YtvA‐LOV, the maximum is redshifted (ca 345 vs 335 nm) and the average fluorescence lifetime shorter (2.7 vs 4.7 ns). These data indicate that W103 is located in a site of tight contact between the two domains of YtvA. In the FMN‐cys adduct, selective excitation of W103 at 295 nm results in minimal changes of the fluorescence parameters with respect to the dark state. On 280 nm excitation, however, there is a detectable decrease in the fluorescence emitted from tyrosines, with concomitant increase in W103 fluorescence. This effect is reversible in the dark and might arise from a light‐regulated energy transfer process from a yet unidentified tyrosine to W103.