bluuebunny/crossref_metadata_2025 huggingface dataset:
STUDIES ON HUMAN LENSES: II. DISTRIBUTION AND SOLUBILITY OF FLUORESCENT PIGMENTS IN CATARACTOUS AND NON‐CATARACTOUS LENSES OF INDIAN ORIGIN
Authors: Bandyopadhyay S. , Chattopadhyay D. , Ghosh S. K. , Chakrabarti B.
Published: July 2010

Abstract—Fluorometric studies of cataractous and non‐cataractous human lenses were carried out to study the emission characteristics and the distribution and solubility of lenticular pigments. Most of the detected fluorophores were well distributed over the cortical and nuclear portion of the lens. The decrease in solubility of proteins with aging and cataract formation is concomitant with increasing photolysis of tryptophan. However, this is likely a phenomenon independent of the photochemical transformations of the lens proteins. The number of emitting species in the diseased lenses are higher than in the normal mature lenses. A species emitting around 375 or 388 nm is of particular interest (Λcx, 330 nm) in that the emission characteristics of this fluorophore resemble kynurenic acid which has a high photosensitizing efficiency. The concentration of fluorescent pigments in the lenses of Indian origin is significantly high. The intense pigmentation could be attributed largely to the formation of photoproducts in the absence of normal endogenous antioxidant accumulation that is dependent on nutrition standard. If, indeed, any of these fluorescent pigments, because of their photosensitizing ability, are responsible for lenticular opacity, it is not the abundance of sunlight alone but also malnutrition that could account for the high incidence of cataract in India.
EFFECT OF PSORALEN + ULTRAVIOLET‐A ON THE CHEMOTACTIC ACTIVITY OF POLYMORPHONUCLEAR NEUTROPHILS TOWARDS ANAPHYLATOXIN C5a DES ARG
Authors: Esaki Kenji , Mizuno Nobuyuki
Published: July 2010

Abstract— It was shown that psoralen + UV‐A inhibits the chemotactic activity of polymorphonuclear neutrophils towards anaphylatoxin C5a des Arg. This reaction required oxygen and there is a high possibility that the active oxygen species was in a singlet state. Oxygen did not act directly on C5a des Arg, but rather produced oxidized psoralen which inhibited C5a des Arg activity. The effect was dependent on the concentration and types of psoralen and on the UV‐A dose. Among the psoralens, the inhibitory effect of 4,5′,8‐trimethylpsoralen was the strongest, followed by 8‐methoxypsoralen and 3‐carbethoxypsoralen and finally 4,4′,6‐trimethylangelicin. Psoralen + UV‐A failed to inhibit the chemotactic activity towards chemotactants other than anaphylatoxin C5a such as casein, the cultured filtrate of E. coli, platelet‐activating factor, leukotriene B4, 5‐hydroxy‐6,8,11,14‐eicosatetraenoic acid and 12‐L‐hydroxy‐5,8,10,14‐eicosatetraenoic acid.
UVA PHOTOLYSIS USING THE PROTEIN‐BOUND SENSITIZERS PRESENT IN HUMAN LENS
Authors: Ortwerth* B. J. , Olesen P. R.
Published: July 2010

Abstract—This research was undertaken to demonstrate that the protein‐bound chromophores in aged human lens can act as sensitizers for protein damage by UVA light. The water‐insoluble (WI) proteins from pooled human and bovine lenses were solubilized by sonication in water and illuminated with UV light similar in output to that transmitted by the cornea. Analysis of the irradiated proteins showed a linear decrease in sulfiydryl groups with a 30% loss after 2 h. No loss was seen when native a‐crystallin was irradiated under the same conditions. A 25% loss of histidine residues was also observed with the human lens WI fraction, and sodium dodecyl sulfate polyacrylamide gels indicated considerable protein cross‐linking. Similar photodamage was seen with a WI fraction from old bovine lenses. While the data show the presence of UVA sensitizers, some histidine destruction and protein cross‐linking were also obtained with a‐crystallin and with lysozyme, which argue that part of the histidine loss in the human WISS was likely due to tryptophan acting as a sensitizer.

A preparation of human WI proteins was irradiated with a total of 200 J/cm2 of absorbed light at 10 nm intervals from 290 to 400 nm. Photodamage of cysteine SH groups (35%) and methionine (28Y0) was maximum at 330 nm and diminished linearly at longer wavelengths. The major loss of tryptophan (80%) occurred at 290 nm, but destruction was observed throughout the UVA range. Tyrosine was 35% destroyed at 290 nm but decreased sharply to only 50 at 330 nm. A constant loss of histidine (20%) was seen at all wavelengths from 290 to 360 nm, with some loss (7–8%) even at 400 nm. These action spectra show that the human lens WI fraction contains a collection of protein‐bound UVA sensitizers that can cause protein photodamage similar to that seen in cataractous lenses.
THE ACTION SPECTRUM FOR INDUCTION OF CHRONIC ACTINIC DERMATITIS IS SIMILAR TO THAT FOR SUNBURN INFLAMMATION
Authors: Menagé H. du P. , Harrison G. I. , Potten C. S. , Young A. R. , Hawk J. L. M.
Published: July 2010

The action spectrum for induction of the abnormal cutaneous response at 24 h in the photosensitivity disorder chronic actinic dermatitis (CAD) was determined in 15 patients and found to be the same in shape as that for normal sunburn in fair‐skinned individuals at 24 h, as determined for 47 control volunteers, although displaced in magnitude. This suggests that an endogenous chromophore(s), the same as or similar to that/those responsible for human sunburn, may be responsible for initiation of the abnormal reaction to irradiation in CAD, and that the putative antigen associated with the CAD reaction may be derived from that/those or associated molecules.
THE PHOTOCHEMISTRY OF HUMAN RETINAL LIPOFUSCIN AS STUDIED BY EPR
Authors: Reszka Krzysztof , Eldred Graig E. , Wang Ren‐Hong , Chignell Colin , Dillon James
Published: July 2010

Fluorescent material generated in the human retina accumulates within lipofuscin (HLF) granules of the retinal pigment epithelium (RPE) during aging. We have been investigating the possible light‐induced contribution of these fluorophores to various diseases including age‐related macular degeneration. Our studies have shown that some of the fluorescent components of HLF are products of the reaction of retinaldehyde with ethanolamine and that synthetic mixtures of this reaction can serve as a useful model for photophysical studies. Previous research by us has demonstrated that irradiation of either natural or synthetic lipofuscin resulted in the formation of a triplet state and possibly a free radical. Here EPR studies were performed to verify the formation of that radical. The UV irradiation of either synthetic or natural human retinal lipofuscin extracts in oxygen‐free methanol led to the formation of a 5,5‐dimethylpyrroline‐N‐oxide (DMPO) spin‐trapped carbon‐centered radical resulting from either hydrogen atom or electron abstraction from solvent molecules. In the presence of oxygen superoxide was formed, which was observed as a DMPO adduct. It is concluded that certain components of the chloroform‐soluble fluorophores of human RPE lipofuscin granules and the fluorescent reaction products of retinaldehyde and ethanolamine are photophysically similar but not the same. Electron or hydrogen abstraction from a substrate by these fluorophores in vivo and the resulting radical products may contribute to the age‐related decline of RPE function and blue light damage in the retina.
BACTERIAL PHOTOPROTECTION THROUGH EXTRACELLULAR CADMIUM SULFIDE CRYSTALLITES
Authors: Holmes Justin D. , Smith Peter R. , Evans‐Gowing Richard , Richardson David J. , Russell David A. , Sodeau John R.
Published: July 2010

Ultraviolet light and the heavy metal, cadmium, both have toxic effects on many microorganisms. In this communication we describe a method by which the bacterium Klebsiella aerogenes surmounts both problems using one biological process: the synthesis of cadmium sulfide (CdS) crystallites. These semiconductor particles absorb radiation in the UV spectral region and therefore, when K. aerogenes produces extracellular CdS material in response to environments containing cadmium ions, a photoprotective layer is formed. The effect of UVA radiation on cultures of Klebsiella aerogenes was monitored using electron microscopy, energy‐dispersive X‐ray analysis and electronic spectroscopy. The results show that at wavelengths 320 nm Λ 400 nm, a photoprotection period of between 4 and 6 h is induced, which eventually fails due to photodegradation of the semiconductor layer to metallic cadmium and elemental sulfur.
THEORETICAL STUDY OF CIRCULAR DICHROISM OF THE LIGHT‐HARVESTING ANTENNA OF PHOTOSYNTHETIC PURPLE BACTERIA: A CONSIDERATION OF EXCITON INTERACTIONS and ENERGY DISORDER
Authors: Novoderezhkin Vladimir I. , Razjivin Andrei P.
Published: July 2010

Circular dichroism and absorption spectra of the light‐harvesting antenna of photosynthetic purple bacteria were studied taking into account exciton interactions between the antenna bacteriochloro‐phylls. Exciton states were calculated for the core antenna configuration in the form of a circular aggregate of N identical bacteriochlorophyll molecules with CN‐symmetry. The influence of pigment inhomogeneity on the proposed exciton description of the antenna was investigated. The calculated line shapes for the circular dichroism and absorption spectra agree well with experimental data for purple bacteria.
EXCITED STATE BEHAVIOR OF PHYTOCHROME Pr
Authors: Teuchner Klaus , Schulz Michael , Stiel Holger , Maisch Manfred , Rudiger Wolfhart
Published: July 2010

The primary excited state processes of phytochrome, the plant chromoprotein responsible for most photomorphogenetic responses, are investigated by picosecond intensity‐dependent transmission measurements. At sufficient high excitation intensity (starting at photon flux densities of about 1′1025 cm−2 s−l) a moderate bleaching of the absorption is observed. For the quantitative analysis of the experimental data a rate equation system approach for the energy levels responsible for the ultrafast transformation Pr→ lumi‐R and the photon transport through the sample was utilized. The following was found for the excited state parameters of the phytochrome Pr: (1) an excited state absorption of the same order of magnitude as the ground state absorption (cross section: S̀exc= 4′10−16 cm−2 at 650 nm), (2) a fast relaxation of the higher excited singlet state on the femtosecond time scale.
PHOTOMORPHOGENIC RESPONSES TO UV RADIATION III: A COMPARATIVE STUDY OF UVB EFFECTS ON ANTHOCYANIN and FLAVONOID ACCUMULATION IN WILD‐TYPE and aurea MUTANT OF TOMATO (Lycopersicon esculentum MILL.)
Authors: Brandt Kirsten , Giannini Alessandro , Lercari Bartolomeo
Published: July 2010

The UV‐mediated induction of anthocyanin and UV‐absorbing compounds was characterized in etiolated hypocotyls of wild‐type and aurea (au) mutant tomato seedlings. Ultraviolet radiation induced significant increases of anthocyanin and UV‐absorbing compounds in hypocotyls of die au mutant and of its isogenic wild‐type, but the differences in the time courses of UV‐induced pigment accumulation indicate mat different photoregulatory mechanisms are involved for each of these two groups of pigments. It appears mat prolonged presence of adequate levels of UVB (290–320nm) energy and consequently the action of a specific UVB photoreceptor are indispensable for the photoinduction of anthocyanin accumulation in UV‐irradiated hypocotyl of the au mutant that is missing the labile phytochrome pool. The large difference found between the wild‐type and the au mutant strongly indicate the involvement of labile phytochrome as the primary functional photoreceptor for the photoinduction of anthocyanin accumulation in wild‐type tomato hypocotyls. The UVB photoreceptor could at least partly replace the action of labile phytochrome (as far as anthocyanin accumulation is concerned) when the functional phytochrome pool is missing as in the au mutant. The general picture of UV‐mediated induction of total UV‐absorbing compounds shows only a macroscopic difference between wild‐type and die au mutant of tomato: the higher initial level (in darkness) of these compounds in die wild‐type in contrast to the au mutant. Although there is UV‐induced accumulation of UV‐absorbing compounds in bom genotypes, the levels in the au mutant never reach mat of the wild‐type under the same UV exposure. A UVB photosensor may play a more important role in the photoinduction of UV‐absorbing compounds. Indeed, in the absence of labile phytochrome, i.e. in the au mutant, a UVB‐absorbing photoreceptor alone is able to establish high responsiveness for the UV‐induced flavonoid accumulation.
INACTIVATION OF Trypanosoma cruzi TRYPOMASTIGOTE FORMS IN BLOOD COMPONENTS BY PHOTODYNAMIC TREATMENT WITH PHTHALOCYANINES
Authors: Gottlieb Paul , Shen Li‐Gang , Chimezie Eleanor , Bahng Soon , Kenney Malcolm E. , Horowitz Bernard , Ben‐Hur Ehud
Published: July 2010

Abstract— ‐Three phthalocyanine dyes HOSiPcOSi(CH3)2(CH2)3N(CH3)2 (Pc 4), HOSiPc‐OSi(CH3)2(CH2)3N+(CH3)3I‐ (Pc 5) and aluminum tetrasulfophthalocyanine hydroxide (AlOHPcS4) were evaluated for their ability to inactivate the trypomastigote form of Trypanosoma cruzi in fresh frozen plasma (FFP) and red blood cell concentrates (RBCC). The compound Pc 4 was found to be highly effective in killing T. cruzi, Pc 5 less effective and AlOHPcS4 ineffective. With FFP as the medium, a complete loss of parasite infectivity in vitro (≥5 log10) was found to occur with 2 μM Pc 4 after irradiation with red light (>600 nm) at a fiuence of 7.5 J/cm2, while with RBCC as the medium, a complete loss was found to occur at a fiuence of 15 J/cm2. Even without illumination, Pc 4 at 2 μM also killed about 3.7‐4.1 log10 of T. cruzi in FFP during 30 min. Observed differences in T. cruzi killing by the various phthalocyanines may relate to differences in binding; Pc 4 binds to the parasites about twice as much as Pc 5. Ultrastructural analysis of treated parasites suggests that mitochondria are a primary target of this photodynamic treatment. The data indicate that Pc 4 combined with exposure to red light could be used to eliminate bloodborne T. cruzi parasites from blood components intended for transfusion. The inactivation of T. cruzi by Pc 4 in the dark suggests a possible therapeutic application.
PSORALEN‐MEDIATED VIRUS PHOTOINACTIVATION IN PLATELET CONCENTRATES: ENHANCED SPECIFICITY OF VIRUS KILL IN THE ABSENCE OF SHORTER UVA WAVELENGTHS
Authors: Margolis‐Nunno Henrietta , Robinson Richard , Horowitz Bernard , Geacintov Nicholas E. , Ben‐Hur Ehud
Published: July 2010

Abstract— Treatments with psoralens and long‐wavelength ultraviolet radiation (UVA, 320–400 nm; PUVA) have shown efficacy for virus sterilization of platelet concentrates (PC). Our laboratory has employed the psoralen derivative 4'‐aminomethyl‐4, 5', 8‐trimethylpsoralen (AMT), and we have found that platelet integrity is best preserved when rutin, a flavonoid that quenches multiple reactive oxygen species, is present during AMT/UVA treatment of PC.

In this report, we examine the effects of different UVA spectra under our standard PC treatment conditions (i.e. 50 μg/mL AMT, 0.35 mM rutin and 38 J/cm2 UVA). Added vesicular stomatitis virus (VSV; ≥5.5 log10) was completely inactivated with the simultaneous maintenance of the platelet aggregation response (>90% of control) when a UVA light source with transmission mainly between 360 and 370 nm (narrow UVA1) was used. In contrast, with a broad‐band UVA (320–400 nm; broad UVA) light source, the aggregation response was greatly compromised (<50% of control) with only a minor increase in the rate of VSV kill. With this lamp, platelet function could be improved to about 75% of the control by adding a long‐pass filter, which reduced the transmission of shorter (≤345 nm) UVA wavelengths (340–400 nm; UVA1). At equivalent levels of virus kill, aggregation function was always best preserved when narrow UVA1 was used for PUVA treatment. Even in the absence of AMT, and with or without rutin present, narrow UVA 1 irradiation was better tolerated by platelets than was broad UVA.

Our results suggest that for PUVA treatment of PC, the UVA dose range in which complete virus kill is obtained with the simultaneous maintenance of in vitro platelet function is smallest with broad UVA irradiation and largest with narrow UVA1. Thus, the virus specificity of PC treatment with AMT, UVA and quenchers can be further enhanced by the exclusion of the shorter UVA wavelength range.
SINGLET OXYGEN IS NOT PRODUCED IN PHOTOSYSTEM I UNDER PHOTOINHIBITORY CONDITIONS
Authors: Hideg ÉVa , Vass Imre
Published: July 2010

Abstract— Excess illumination of photosynthetic systems brings about the complex functional and structural damage known as photoinhibition. According to the generally accepted and experimentally confirmed model, photoinhibition involves singlet oxygen production and subsequent oxidative damage in the photosystem II reaction center. However, it was recently suggested that singlet oxygen is not necessarily produced in photosystem II itself but rather in the non‐heme iron‐containing Fe‐S centers of photosystem I (Chung, S.K. & J. Jung, Photochem. Photobiol. 61, 383–389, 1995). Contrary to this suggestion, our electron paramagnetic resonance spectroscopy experiments with the singlet oxygen trap 2,2,6,6‐tetramethylpiperidine demonstrate that under photoinhibitory conditions, singlet oxygen is present in thylakoids and photosystem II core complex preparations but is not produced in photosystem I particles.
A Water‐Soluble Luminescence Oxygen Sensor
Authors: Castellano Felix N. , Lakowicz Joseph R.
Published: July 2010

We developed a water‐soluble luminescent probe for dissolved oxygen. This probe is based on (Ru[dpp(SO3Na)2]3) Cl2, which is a sulfonated analogue of the well‐known oxygen probe (Ru[dpp]3)Cl2. The compound dpp is 4,7‐diphenyl‐1,10‐phenanthroline and dpp(SO3Na)2 is a disulfonated derivative of the same ligand. In aqueous solution in the absence of oxygen (Ru[dpp(SO3Na)2]3)Cl2 displays a lifetime of 3.7 μs that decreases to 930 ns on equilibrium with air and 227 ns on equilibrium with 100% oxygen. The Stern–Vohner quenching constant is 11330 M−1. This high oxygen‐quenching constant means that the photoluminescence of Ru(dpp[SO3Na]2)3Cl2 is 10% quenched at an oxygen concentration of 8.8 x 10−6M, or equilibration with 5.4 torr of oxygen. The oxygen probe dissolved in water displays minimal interactions with lipid vesicles composed of dipalmityl‐L‐α‐phosphatidyl glycerol but does appear to interact with human serum albumin. The absorption maximum near 480 nm, long lifetime and large Stokes’shift allow this probe to be used with simple instrumentation based on a light‐emitting diode light source, allowing low‐cost oxygen sensing in aqueous solutions. To the best of our knowledge this is the first practical water‐soluble oxygen sensor.
Magnetic Field Effects on the Dynamics of Radical Pairs in Micelles: A New Approach to Understanding the “Cage Effect”
Authors: Kleinman Mark H. , Shevchenko Tatiana , Bohne Cornelia
Published: July 2010

The effect of temperature on the photolysis of dibenzyl ketone and 4‐methyldibenzyl ketone in sodium dodecyl sulfate micelles was studied by laser flash photolysis and product distributions derived from steady‐state photolysis. At high temperatures, the product distribution and radical decay kinetics are primarily due to random encounters of radicals, and the “cage effect” cannot be rationalized by geminate recombination reactions that occur before the radicals escape from the micelles. A mechanism is proposed in which the enhancement of the crosstermination product derived from random encounters is due to the different partitioning of each radical species between the micelles and the aqueous phase, thereby leading to different rates for the self‐termination reactions.
Erythemally Weighted Radiometers in Solar UV Monitoring: Results from the WMO/STUK Intercomparison
Authors: Leszczynski Kirsti , Jokela Kari , Ylianttila Lasse , Visuri1 Reijo , Blumthaler Mario
Published: July 2010

The first international intercomparison of erythemally weighted (EW) broadband radiometers was arranged in 1995 to improve the accuracy and comparability of the measurements carried out by solar UV monitoring networks. The intercomparison was arranged at the Radiation and Nuclear Safety Authority in Helsinki, Finland, in cooperation with the University of Innsbruck and with support from the World Meteorological Organization. Altogether 20 EW meters of six different types from 16 countries were (1) tested in the laboratory by measuring the spectral and angular responsivities and (2) calibrated in solar radiation against two reference spectroradiometers. Calibration factors (CFs) for the EW meters were determined by using simultaneously measured EW solar UV spectra as a calibration reference. The CFs averaged over solar elevations higher than 35° varied from 0.87 to 1.75, with the estimated uncertainty being ±10%. As a result of this intercomparison, for the first time the calibrations of more than 100 EW radiometers around the world are possible to trace to the same origin. The present experience indicates that the accuracy of temperature‐controlled EW radiometers is not significantly lower than the accuracy of spectroradiometers provided that strict quality assurance/quality control procedures are followed.
Multiphoton Near‐Infrared Femtosecond Laser Pulse‐Induced DNA Damage With and Without the Photosensitizer Proflavine
Authors: Shafirovich Vladimir , Dourandin Alexander , Luneva Natalia P. , Singh Carolyn , Kirigin Francis , Geacintov Nicholas E.
Published: July 2010

Abstract— The excitation of pBR322 supercoiled plasmid DNA with intense near‐IR 810 nm fs laser pulses by a simultaneous multiphoton absorption mechanism results in single‐strand breaks after treatment of the irradiated samples with Micrococcus luteus UV endonuclease. This enzyme cleaves DNA strands at sites of cyclobutane dimers that are formed by the simultaneous absorption of three (or more) 810 nm IR photons (pulse width ∼140 fs, 76 MHz pulse repetition rate, average power output focused through 10×microscope objective is ∼1.2 MW/cm2). Direct single‐strand breaks (without treatment with M. luteus) were not observed under these conditions. However, in the presence of 6 μM of the intercalator proflavine (PF), both direct single‐and double‐strand breaks are observed under conditions where substantial fractions of undamaged supercoiled DNA molecules are still present. The fraction of direct double‐strand breaks is 30 ± 5% of all measurable strand cleavage events, is independent of dosage (up to 6.4 GJ/ cm2) and is proportional to In, where I is the average power/area of the 810 nm fs laser pulses, and n = 3 ± 1. The nicking of two DNA strands in the immediate vicinity of the excited PF molecules gives rise to this double‐strand cleavage. In contrast, excitation of the same samples under low‐power, single‐photon absorption conditions (∼400–500 nm) gives rise predominantly to single‐strand breaks, but some double‐strand breaks are observed at the higher dosages. Thus, single‐photon excitation with 400–500 nm light and multiphoton activation of PF by near‐IR fs laser pulses produces different distributions of single‐and double‐strand breaks. These results suggest that DNA strand cleavage originates from unrelaxed, higher excited states when PF is excited by simultaneous IR multiphoton absorption processes.
Spectral Changes Induced by Alkaline pH and Specific Chemical Modification of Amino Acid Residues in the Light‐Harvesting II Antenna Complex from Ectothiorhodospira sp.
Authors: Buche André , Picorel Rafael
Published: July 2010

Abstract— The absorption spectrum of the membrane‐bound light‐harvesting (LH)II antenna complex from Ectothiorhodospira sp. has two characteristic near‐infrared bands at 797 (B800 band) and 857 (B850 band) nm. Alkaline pH induced a B850 band blue shift of 17–21 nm depending on experimental conditions. The blue shift was totally reversible when the original experimental conditions were re‐established. No significant effect was observed, however, on the B800 band under the same experimental conditions. The intensity and shape of the pigment circular dichroism signals were maintained with the exception of a blue shift of the signal from the B850 band concomitant with the blue shift of that absorption band. Specific chemical modification of the LHII complex with salicylaldehyde allowed correlation of the alkaline pH effect with the neutralization of a lysine positive charge. We propose that the observed blue shift of the B850 band is due to distortion of the bacteriochlorophyll domain as a consequence of electrostatic and probably hydrogen‐bonding changes but not due to modification of the pigment excitonic interactions within the pigment‐protein complex.
Effect of Alkaline Treatment on Bacteriochlorophyll a, Quinones and Energy Transfer in Chlorosomes from Chlorobium tepidum and Chlorobium phaeobacteroides
Authors: van Walree Cornells A. , Sakuragi Yumiko , Steensgaard Dorte B. , Bösinger Carola S. , Frigaard Niels‐Ulrik , Cox Raymond P. , Holzwarth Alfred R. , Miller Mette
Published: July 2010

Abstract— Chlorosomes isolated from two types of green sulfur bacteria, Chlorobium tepidum which contains bacteriochlorophyll c (BChl c) and the BChl e‐containing Chlorobium phaeobacteroides, were subjected to alkaline treatment (pH 12.7 at 40°C for 20 min). This caused selective degradation of BChl a, whereas BChl c or e were not affected. Chlorobiumquinone in the Chlorosomes was partially degraded by the alkaline treatment but menaquinone was unchanged. Fluorescence decay kinetics showed that alkaline treatment disrupted energy transfer from BChl c or e to BChl a under reducing conditions. However, this did not give rise to any substantial increase in the excited state lifetime of BChl e in C. phaeobacteroides Chlorosomes, while for C. tepidum a decrease in the BChl c lifetime was found. The steady‐state fluorescence of chlorosomes is highly dependent on the redox potential such that emission is quenched in oxidizing environments. Alkaline treatment diminished this quenching effect and caused a doubling in the BChl c or e emission intensity under aerobic conditions. Single‐photon timing experiments confirmed that alkaline treatment inhibits the energy trapping process operative under aerobic conditions. These effects of alkaline treatment on the fluorescence intensity and decay kinetics are likely to be related to the depletion in BChl a or in Chlorobiumquinone or a combination of these.
Research Note: The High Photoactivity of m‐THPC in Photodynamic Therapy. Unusually Strong Retention of m‐THPC by RIF‐1 Cells in Culture
Authors: Ball Denise J. , Vernon David I. , Brown Stanley B.
Published: July 2010

Abstract— 5,10,15,20‐Tetra(m‐hydroxyphenyl)chlorin (m‐THPC, Foscan) is an extremely powerful photosensitizer showing up to 200 times the photodynamic activity of Photofrin in patients, in terms of drug/light dose. The influence of treatment conditions on the photodynamic efficacy of m‐THPC has been compared to polyhematoporphyrin (PHP), a Photofrin equivalent, and a cationic pyridinium zinc (II) phthalocyanine (PPC), using the RIF‐1 cell line. As predicted, the presence of serum during sensitizer incubation reduced the photodynamic efficacy of all three sensitizers. However, the presence of serum during the illumination period only had an inhibitory effect with PHP and PPC but not m‐THPC. Quantification of the intracellular levels of sensitizer revealed that this was due to the efflux of PPC and PHP but not m‐THPC into the medium, suggesting that m‐THPC is tightly sequestered on entering the cell. This may partially explain the high efficacy of m‐THPC in clinical photodynamic therapy and also highlights the importance not only of incubation conditions but also illumination conditions when in vitro comparisons are performed.
Laser‐Induced Fluorescence (LIF) Recognition of the Structural Composition of Porcine Heart Valves
Authors: Christov Alexander M. , Liu Liying , Lowe Shoshona , Icton Carolyn , Dunmore‐Buyze Joy , Boughner Derek R. , Dai Erbin , Lucas Alexandra
Published: July 2010

Abstract— Reconstruction and replacement of heart valves with grafts from pig tissue is a common procedure. However, bioprosthetic valves wear out in a shorter time span than mechanical valves. Bioprosthetic valve structure may contribute to degenerative changes that lead to valve failure. There is, at present, no method to examine the structure of a tissue valve prior to implant. Laser‐induced fluorescence (LIF) of natural fluorophores is an elegant method developed for the detection of tumors, dermal lesions and atherosclerosis. We have studied LIF as a potential diagnostic technique for analysis of valvular tissue. Using excimer laser excitation, we examined natural fluorescence recorded from porcine aortic, mitral and pulmonary valves. All three valve outflow surface tissue layers are less fluorescent at 390–450 nm than the inflow layers. Immunohistochemical analysis of collagen I and elastin content in inflow and outflow surface layers of all three valves correlated well with LIF intensities and dI/dΛ values at selected wavelengths. In conclusion, the differences observed in emitted LIF from valve surface layers are found to correlate well with diversity in the structural protein content. The LIF spectroscopic measurements may provide an appropriate tool for examination of tissue valve structure prior to use for implantation.
Oxidative Modifications of the Photosystem II D1 Protein by Reactive Oxygen Species: From Isolated Protein to Cyanobacterial Cells¶
Authors: Lupínková Lenka , Komenda Josef
Published: July 2010

Action of reactive oxygen species (ROS) on the isolated D1 protein, a key component of Photosystem II (PSII) complex, was studied and compared with the effect of high irradiance on this protein in mildly solubilized photosynthetic membranes and cells of the cyanobacterium Synechocystis. Whereas singlet oxygen caused mainly protein modification reflected by shift of its electrophoretic mobility, action of hydrogen peroxide and superoxide resulted in generation of specific fragments. Hydroxyl radicals as the most ROS induced fast disappearance of the protein. The results substantiate the ability of ROS to cause direct scission of the D1 peptide bonds. Similar D1 modification, fragmentation and additionally cross‐linking with other PSII subunits were observed during illumination or hydrogen peroxide treatment of mildly solubilized thylakoids. Peroxide‐induced fragmentation did not occur in thylakoids of the strain lacking a ligand to the nonheme iron, confirming the role of this prosthetic group in the D1‐specific cleavage. The D1 modification, fragmentation and cross‐linking were suppressed by ROS scavengers, supporting the direct role of ROS in these phenomena. Identical symptoms of the ROS‐induced D1 damage were detected in illuminated cells of Synechocystis mutants with a higher probability of ROS formation, documenting the relevance of the in vitro results for the situation in vivo.
Influence of PAR and UV‐A in Determining Plant Sensitivity and Photomorphogenic Responses to UV‐B Radiation ¶†
Authors: Krizek Donald T.
Published: July 2010

The role of photosynthetically active radiation (400‐700 nm) (PAR) in modifying plant sensitivity and photomorphogenic responses to ultraviolet‐B (280–320 nm) (UV‐B) radiation has been examined by a number of investigators, but few studies have been conducted on ultraviolet‐A (320‐400 nm) (UV‐A), UV‐B and PAR interactions. High ratios of PAR‐UV‐B and UV‐A‐UV‐B have been found to be important in ameliorating UV‐B damage in both terrestrial and aquatic plants. Growth chamber and greenhouse studies conducted at low PAR, low UV‐A and high UV‐B often show exaggerated UV‐B damage. Spectral balance of PAR, UV‐A and UV‐B has also been shown to be important in determining plant sensitivity in field studies. In general, one observes a reduction in total biomass and plant height with decreasing PAR and increasing UV‐B. The protective effects of high PAR against elevated UV‐B may also be indirect, by increasing leaf thickness and the concentration of flavonoids and other phenolic compounds known to be important in UV screening. The quality of PAR is also important, with blue light, together with UV‐A radiation, playing a key role in photorepair of DNA lesions. Further studies are needed to determine the interactions of UV‐A, UV‐B and PAR.
Invited Review: Light at Night and Cancer Risk ¶
Authors: Schernhammer Eva , Schulmeister Karl
Published: July 2010

Environmental lighting powerfully suppresses the physiologic relase of melationin, which typically peaks in the middle of the night. This decreased melationin production has been hypothesized to increase the risk of cancer. Evidence from experimental studies supports a link between melationin and tumor growth. There is also fairly consistent indirect evidence from observational studies for an association between melatonin suppression, using night work as a surrgogate, and the breast cancer risk.
Rapid Communication: Direct Optical Detection of Singlet Oxygen from a Single Cell ¶
Authors: Zebger Ingo , Snyder John W. , Andersen Lars Klembt , Poulsen Lars , Gao Zhan , Lambert John D. C. , Kristiansen Uffe , Ogilby Peter R.
Published: July 2010

Singlet oxygen has been detected in single nerve cells by its weak 1270 nm phosphorescence (a1Δg→X3Σg−) upon irradiation of a photosensitizer incorporated in the cell. Thus, one can now consider the application of direct optical imaging techniques to mechanistic studies of singlet oxygen at the single‐cell level.
Analysis of Effective Molecular Diffusion Rates for Verteporfin in Subcutaneous Versus Orthotopic Dunning Prostate Tumors ¶
Authors: Zhou Xiaodong , Pogue Brian W. , Chen Bin , Hasan Tayyaba
Published: July 2010

Photosensitizer biodistribution change inside tissue is one of the dominant factors in photodynamic therapy efficacy. In this study, the pharmacokinetics of a benzoporphyrin derivative (BPD), delivered in verteporfin for injection formulation, have been quantified in the rat Dunning prostate tumor MAT‐LyLu model, using both subcutaneous and orthotopic sites. Blood plasma sampling indicated that BPD had a bi‐exponential metabolic lifetime in vivo, with the two lifetimes being 9.6 min and 8.3 h. The spatial distributions in the tumor were quantified as a function of distance from the perfused blood vessels, using fluorescence histologic images of the tumor. A fluorescent vascular marker was used to obtain locations and shapes of perfused capillaries at a wavelength of emission different from that of BPD and to allow colocalized images to be acquired of vessel and BPD locations. Using the BPD fluorescence images obtained 15 min after intravenous administration, a forward finite‐element solution to the diffusion equation was used to predict the drug distribution by matching the fluorescence intensity images observed microscopically. An inverse solver was used to minimize the root mean square error between the image of simulated diffusion and the experimental image, resulting in estimation of the diffusion coefficient of BPD in the tumor models. Effective diffusion coefficients were 0.88 and 1.59 μm2/s for the subcutaneous and orthotopically grown tumors, respectively, indicating that orthotopic tumors have significantly higher vascular extravasation rates as compared with subcutaneous tumors. This analysis supports the hypothesis that leakage rates of the photosensitizer vary considerably. Thus, although varying the time between injection and optical irradiation may be used to vary the targeting between vascular and less vascular areas, the precise time of treatment will depend on the nature of the permeability of the vasculature in the tissue being treated.
Blue Light‐induced Chloroplast Reorientations in Lemna trisulca L. (Duckweed) are Controlled by Two Separable Cellular Mechanisms as Suggested by Different Sensitivity to Wortmannin¶
Authors: Grabalska Magdalena , Malec Przemysław
Published: July 2010

Chlorplast reorientations within mesophyll cells are among the most rapid physiological responses of higher plants to blue light. At light intensities below the saturation point of photosynthesis, chloroplasts move to the cell walls perpendicular to the direction of light and maximize light absorption (low‐fluence rate response [LFR]. At light intensities above the saturation point of photosythesis, chloroplasts, redistribute to cell walls parallel to the direction of light (hight‐fluence rate response [HFR]). The actin‐based mechanism is responsible for the light‐induced chloroplast movements. We have found that an inhibitor of phosphoinositide‐3‐kinases, wortmannin, potently and irreversibly inhibited LFR and HFR chloroplast responses to blue light in Lemna trisulca L. mesophyll cells. Microscopic observations and photometric measurement indicated that 100 nM wortmannin specifically inhibited LFR in Lemna, whereas HFR displayed no sensitivity to the inhibitor at this concentraion. A complete inhibition of the HFR could be obtained by 1 μM wortmannin. These data indicate that LFR is more sensitive to wortmannin than HFR and suggest that these two responses may be under the control of different cellular mechanisms. Our results suggest that phosphoinositide kinases and other phosphoinositide cycle enzymes may play a role in the transduction of the light signal to the actin cytoskeleton in Lemna as factors specifying the direction of chloroplast movements. A hypothetical model assuming three signaling pathways regulating light‐induced chloroplast reorientations in mesophyll cells is proposed.
The Solvent‐initiated Photolysis of Dichloro(2,2′‐bipyridine)platinum(II) in Chloroform¶
Authors: Whang Sharon , Estrada Toño , Hoggard Patrick E.
Published: July 2010

Under 254 nm irradiation, [Pt(bpy)Cl2] is converted to [Pt(bpy)Cl4] in a solvent‐initiated process. The reaction is very nearly zero order throughout. The rate decreases slightly with increasing starting concentration. These characteristics can be rationalized by a rate law of the form afs, where fs, is the fraction of light absorved by chloroform. The species that reacts with [Pt(bpy)Cl2] is believed to be CCl3OO.
Involvement of G Proteins in the Mycelial Photoresponses of Phycomyces¶
Authors: Tsolakis George , Moschonas Nicholas K. , Galland Paul , Kotzabasis Kiriakos
Published: July 2010

Many responses of the zygomycete fungus Phycomyces blakesleeanus are mediated by blue light, e.g. the stimulation of β‐carotene synthesis (photocarotenogenesis) and the formation of fruiting bodies (photomorphogenesis). Even though both responses have been described in detail genetically and biophysically, the underlying molecular events remain unknown. Applying a pharmacological approach in developing mycelia, we investigated the possible involvement of heterotrimeric G proteins in the blue‐light transduction chains of both responses. G protein agonists (guanosine triphosphate analogues, cholera toxin, pertussis toxin) mimicked in darkness the effect of blue light for both responses, except for cholera toxin, which was ineffective in increasing the β‐carotene content of dark‐grown mycelia. Experiments combining the two toxins indicated that photocarotenogenesis could involve an inhibitory G protein (Gi) type, whereas photomorphogenesis may depend on a transducin (Gt type)‐like heterotrimer. The determination of the carB (phytoene dehydrogenase) and chs1 (chitin synthase 1) gene expression under various conditions of exogenous challenge supports the G protein participation. The fluctuations of the time course measurements of the carB and chs1 transcripts are discussed.
Field Testing of Biological Spectral Weighting Functions for Induction of UV‐absorbing Compounds in Higher Plants†¶
Authors: Flint Stephan D. , Searles Peter S. , Caldwell Martyn M.
Published: July 2010

Action spectra are typically used as biological spectral weighting functions (BSWF) in biological research on the stratospheric ozone depletion issue. Despite their critical role in determining the amount of UV supplied in experiments, there has been only limited testing of different functions under realistic field conditions. Here, we calculate effective radiation according to five published BSWF and evaluate the appropriateness of these BSWF in representing the induction of UV‐absorbing compounds. Experiments were carried out in the field using both ultraviolet‐B radiation (280–320 nm) supplementation and selective filtering of solar UV radiation. For the four species tested, BSWF that extend into the ultraviolet‐A radiation (320–400 nm) (UV‐A) with moderate effectiveness best represented the observed results. When compared with the commonly used generalized plant response, these BSWF suggest that simulations of ozone depletion will require more radiation than in the past experiments. However, they imply lower radiation supplements than a new plant growth BSWF that has a greater emphasis on UV‐A wavelengths.
Efficacy of Different UV‐emitting Light Sources in the Induction of T‐cell Apoptosis¶
Authors: Novák Zoltán , Bérces Attila , Rontó Györgyi , Pállinger Éva , Dobozy Attila , Kemény Lajos
Published: July 2010

Ultraviolet B(UV‐B) radiation is a modality widely used for the treatment of different skin diseases. One of the major mechanisms of UV‐B immunosuppression in this treatment modality is thought to be an apoptosis‐inducing effect on T cells infiltrating the skin. We examined the T‐cell apoptosis induction capacities of four different UV light sources, with and without UV filters. The xenon chloride (XeCl) laser proved to be the strongest apoptosis inducer. The use of a phtalic acid filter eliminated UV radiation almost completely below 300 nm, which resulted in a severe decrease in the apoptosis‐inducing capacity of different UV‐B sources. Using the results of the measurements with polychromatic UV light sources, the wavelength dependence of UV‐B light for the induction of T‐cell apoptosis was also determined. The regression line of the action spectrum demonstrated a continuous decrease from 290 to 311 nm. The apoptosis‐inducing capacity of the XeCl laser was almost four times higher than the calculated value according to the action spectrum, which might be attributed to the high irradiance of the laser as compared with nonlaser light sources.
Expressed Sequence Tag Analysis of the Dinoflagellate Lingulodinium polyedrum During Dark Phase¶
Authors: Tanikawa Naomi , Akimoto Hidetoshi , Ogoh Katsunori , Chun Wu , Ohmiya Yoshihiro
Published: July 2010

To collect information on gene expression during the dark period in the luminous dinoflagellate Lingulodinium polyedrum, normalized complementary DNA (cDNA) libraries were constructed from cells collected during the first hour of night phase in a 12:12 h light‐dark cycle. A total of 4324 5′‐end sequence tags were isolated. The sequences were grouped into 2111 independent expressed sequence tags (EST) from which 433 groups were established by similarity searches of the public nonredundant protein database. Homology analysis of the total sequences indicated that the luminous dinoflagellate is more similar to land plants and animals (vertebrates and invertebrates) than to prokaryotes or algae. We also isolated three bioluminescence‐related (luciferase and two luciferinbinding proteins [LBP]) and 37 photosynthesis‐related genes. Interestingly, two kinds of LBP genes occur in multiple copies in the genome, in contrast to the single luciferase gene. These cDNA clones and EST sequence data should provide a powerful resource for future genome‐wide functional analyses for uncharacterized genes.
Chemical and Structural Changes in Blood Undergoing Laser Photocoagulation¶
Authors: Black John F. , Barton Jennifer Kehlet
Published: July 2010

The treatment of cutaneous vascular lesions (port wine stains etc.) using lasers has been guided by theories based on the “cold” or room‐temperature optical properties of the hemoglobin target chromophore. We have recently presented evidence showing that under the influence of laser irradiation, the optical properties of blood in vitro are time and temperature dependent. Such complications are not currently subsumed into the in vivo theory. Here, we study the time‐domain optical properties of blood undergoing photocoagulation in vitro using two newly developed time‐resolved techniques. We also study the asymptotic effect of laser photocoagulation on the chemical and structural properties of the components of the blood matrix. We present evidence showing that the photocoagulation process involves significant changes in the optical absorption and scattering properties of blood, coupled with photothermally induced chemical and structural changes. We demonstrate the first use of a laser to deliberately generate magnetic resonance imaging contrast in vitro. We show that this technique offers significant potential advantages to in vivo intravenous chemical contrast agent injection.
Rose Bengal‐Sensitized Photooxidation of the Dipeptides l‐Tryptophyl‐l‐Phenylalanine, l‐Tryptophyl‐l‐Tyrosine and l‐Tryptophyl‐l‐Tryptophan: Kinetics, Mechanism and Photoproducts¶
Authors: Posadaz Ariana , Biasutti Alicia , Casale César , Sanz Jesús , Amat‐Guerri Francisco , García Norman A.
Published: July 2010

The Rose Bengal‐sensitized photooxidations of the dipeptides l‐tryptophyl‐l‐phenylalanine (Trp‐Phe), l‐tryptophyl‐l‐tyrosine (Trp‐Tyr) and l‐tryptophyl‐l‐tryptophan (Trp‐Trp) have been studied in pH 7 water solution using static photolysis and time‐resolved methods. Kinetic results indicate that the tryptophan (Trp) moiety interacts with singlet molecular oxygen (O2(1Δg)) both through chemical reaction and through physical quenching, and that the photooxidations can be compared with those of equimolecular mixtures of the corresponding free amino acids, with minimum, if any, influence of the peptide bond on the chemical reaction. This is not a common behavior in other di‐ and polypeptides of photooxidizable amino acids. The ratio between chemical (kr) and overall (kt) rate constants for the interaction O2(1Δg)‐dipeptide indicates that Trp‐Phe and Trp‐Trp are good candidates to suffer photodynamic action, with krlkt values of 0.72 and 0.60, respectively (0.65 for free Trp). In the case of Trp‐Tyr, a lower krlkt value (0.18) has been found, likely as a result of the high component of physical deactivation of O2(1Δg) by the tyrosine moiety. The analysis of the photooxidation products shows that the main target for O2(1Δg) attack is the Trp group and suggests a much lower accumulation of kynurenine‐type products, as compared with free Trp. This is possibly because of the occurrence of another accepted alternative pathway of oxidation that gives rise to 3a‐oxidized hydrogenated pyrrolo[2,3‐b]indoles.
Tattoo Pigments are Cleaved by Laser Light‐The Chemical Analysis In Vitro Provide Evidence for Hazardous Compounds¶
Authors: Vasold Rudolf , Naarmann Natascha , Ulrich Heidi , Fischer Daniela , Könlg Burkhard , Landthaler Michael , Bäumler Wolfgang
Published: July 2010

In the western world, more than 80 million people decorate their skin with tattoos. Tattoo colorants are injected into the skin, like medical drugs. Most tattoo colorants are industrial pigments, and chemical industries have never produced them for human use but only to stain consumer goods. Up to 10% of tattooed people request removal of their tattoos because of an improved self‐image or social stigmatization. In contrast to tattooing, physicians usually perform the tattoo removal. For that purpose laser light at very high intensities irradiates the skin to destroy the tattoo pigments. Based on a recent analysis of tattoo pigments, two widely used azo compounds were irradiated in suspension with laser and subsequently analyzed by using quantitative high‐performance liquid chromatography and mass spectrometry. The high laser intensities cleaved the azo compounds, leading to an increase of decomposition products such as 2‐methyl‐5‐nitroaniline,2‐5‐dichloraniline and 4‐nitro‐toluene, which are toxic or even carcinogenic compounds. Moreover, the results of the chemical analysis show that the tattoo colorants already contain such compounds before laser irradiation. Because of a high number of patients undergoing laser treatment of tattoos and based on the results of our findings in vitro, it is an important goal to perform a risk assessment in humans regarding laser‐induced decomposition products.