bluuebunny/crossref_metadata_2025 huggingface dataset:
Triplet Energy Transfer between the Primary Donor and Carotenoids in Rhodobacter sphaeroides R‐26.1 Reaction Centers Incorporated with Spheroidene Analogs Having Different Extents of π‐Electron Conjugation
Authors: Farhoosh Roya , Chynwat Veeradej , Gebhard Ronald , Lugtenburg Johan , Frank Harry A.
Published: January 2008

Abstract— Three carotenoids, spheroidene, 3,4‐dihydrospheroidene and 3,4,5,6‐tetrahydrospheroidene, having 8, 9 and 10 conjugated carbon‐carbon double bonds, respectively, were incorporated into Rhodobacter (Rb.) sphaeroides R‐26.1 reaction centers. The extents of binding were found to be 95±5% for spheroidene, 65±5% for 3,4‐dihydrospheroidene and 60±10% for 3,4,5,6‐tetrahydrospheroidene. The dynamics of the triplet states of the primary donor and carotenoid were measured at room temperature by flash absorption spectroscopy. The carotenoid, spheroidene, was observed to quench the primary donor triplet state. The triplet state of spheroidene that was formed subsequently decayed to the ground state with a lifetime of 7.0±0.5 μs. The primary donor triplet lifetime in the Rb. sphaeroides R‐26.1 reaction centers lacking carotenoids was 60±5 μs. Quenching of the primary donor triplet state by the carotenoid was not observed in the Rb. sphaeroides R‐26.1 reaction centers containing 3,4‐dihydrospheroidene nor in the R‐26.1 reaction centers containing 3,4,5,6‐tetrahydrospheroidene. Triplet‐state electron paramagnetic resonance was also carried out on the samples. The experiments revealed carotenoid triple‐state signals in the Rb. sphaeroides R‐26.1 reaction centers incorporated with spheroidene, indicating that the primary donor triplet is quenched by the carotenoid. No carotenoid signals were observed from Rb. sphaeroides R‐26.1 reaction centers incorporating 3,4‐dihydrospheroidene nor in reaction centers incorporating 3,4,5,6‐tetrahydrospheroidene. Circular dichroism, steady‐state absorbance band shifts accompanying the primary photochemistry in the reaction center and singlet energy transfer from the carotenoid to the primary donor confirm that the carotenoids are bound in the reaction centers and interacting with the primary donor. These studies provide a systematic approach to exploring the effects of carotenoid structure and excited state energy on triplet transfer between the primary donor and carotenoids in reaction centers from photosynthetic bacteria.
Seasonal Variation in Urocanic Acid Isomers in Human Skin
Authors: Olivarius F. de Fine , Wulf H. C. , Crosby J. , Norval M.
Published: January 2008

Abstract— Urocanic acid (UCA) is a major chromophore for UV in the skin and has been suggested to act as an initiator of UV‐induced immunosuppression. It converts from the naturally occurring trans‐isomer to the cis‐isomer on UV exposure. Isomerization is dose dependent until the photostationary state is reached, and the seasonal variation in irradiance from the sun may lead to changes in the percentage of UCA present as cis ‐UCA throughout the year. Thirty young healthy subjects, skin types I‐IV, were followed from early summer till spring. At each of six visits (June, July, August, October, December, March), pigmentation and the concentration of UCA isomers were measured at six body sites: forehead, upper chest, upper back, outer upper arm, inner upper arm and buttock. In exposed as well as unexposed regions a variation in pigmentation was found, peak values being recorded in August. Total UCA concentration was lower in July and August than in the rest of the year, irrespective of body site. In July, the percentage of cis ‐UCA was close to the maximal obtainable (50‐60%) at all sites except the buttock. In the three winter months the percentage of cis‐UCA was below 7% in all regions except for the forehead, where the mean cis ‐UCA was 18% in October and March. No consistent relationship was found between UCA isomers and pigmentation or skin type.
Phytochrome‐regulated Starch Degradation in Germinating Turions of Spirodela polyrhiza
Authors: Dölger Korbinian , Tirlapur Uday K. , Appenroth Klaus‐J.
Published: January 2008

Abstract— Turions of the duckweed Spirodela polyrhiza contain about 70% starch on the dry weight basis. The rate of starch degradation in nondormant turions was highest in continuous red light (cR) followed by continuous blue light (cB), whereas continuous far red light (cFR) is almost ineffective. Continuous R could be substituted by repeated R pulses; this effect was not photoreversible by FR pulses applied after hourly R pulses. This suggested that R‐dependent high irradiance response is the mode of phytochrome action in mediating starch degradation. Comparing the mode of phytochrome action with that of phytochrome mutants of other plants it can be assumed that phytochrome B is the photoreceptor involved. Application of the translation inhibitor cycloheximide immediately stopped the phytochrome‐dependent starch degradation demonstrating the involvement of de novo synthesis of proteins.
Photochemical Preparation of Highly Water‐Soluble Pendant [60]Fullerene‐Aminopolymers
Authors: Sun Ya‐Ping , Liu Bing , Lawson Glenn E.
Published: January 2008

Abstract— In order to introduce fullerene cages into an aqueous environment, pendant [60]fullerene‐poly(propionylethyle‐neimine‐co‐ethyleneimine) was prepared photochemical‐ly. The pendant polymer is highly water soluble, with equivalent aqueous solubilities of the polymer‐bound [60]fullerene much higher than the solubility of [60]ful‐lerene in toluene. The photochemical reaction between [60]fullerene and secondary amine moieties in the ami‐nopolymers likely follows a photoinduced electron transfer‐proton transfer mechanism. The pendant polymer structures, which are represented by dehydrogenated di‐and tetra‐aminofullerene linkages, were characterized by use of proton and 13C NMR, Fourier transform‐infrared spectroscopy, gel‐permeation chromatography and optical spectroscopic methods.
Inverse Filtering and Linear Prediction as New Analytical Approaches to Analyze the Change of Absorbance Spectra in Visible Spectroscopy: in vivo Study of Protochlorophyll(ide) Phototransformation
Authors: Salvetat Richard , Eullaffroy Philippe , Popovic Radovan
Published: January 2008

Abstract— The common approach of analyzing spectra by derivation is known to be inadequate for kinetic studies in visible spectroscopy (R. I. Sharger, Photochem. Photobiol. 38, 615‐617, 1983) because the side‐lobes height introduces artifacts and reduces readability in three‐dimensional graphic representation. In this study we present for the first time a parametric method that enables the use of inverse filtering and linear prediction for kinetic investigation in visible spectroscopy in cell biology studies. The protochlorophyll(ide) phototransformation at room temperature (295 K) was used to demonstrate the performance of this analytical approach. The change of absorption spectra in etiolated barley leaves was analyzed after being illuminated by a 50 ms flash.
Accuracy of Noninvasive in vivo Measurements of Photosensitizer Uptake Based on a Diffusion Model of Reflectance Spectroscopy
Authors: Weersink Robert A. , Hayward Joseph E. , Diamond Kevin R. , Patterson Michael S.
Published: January 2008

Abstract— This study compares the photosensitizer concentration measured noninvasively in vivo by diffuse reflectance spectroscopy with the results of postmortem tissue solubilization and fluorometric assay. The reflectance spectrometer consists of a fiber optic surface probe, spectrometer and charge‐coupled device (CCD) array detector. The surface probe has eight detection fibers separated from the light source fiber by distances ranging from 0.85 to 10 mm. The imaging spectrometer disperses the light from each detector fiber onto the two‐dimensional CCD array, while maintaining spatial separation of each individual spectrum. A single exposure of the CCD therefore captures the reflectance spectrum at eight distances and over a range of 300 nm. From the spectra, the tissue's optical scattering and absorption coefficients are determined using a diffusion model of light propagation. Changes in the tissue absorption are used to estimate the photosensitizer concentration. Normal New Zealand White rabbits were injected with aluminum phthalocyanine tetrasulfonate (AlPcS4) and probe measurements made 24 h after injection on the dorsal skin, on muscle after surgically turning the skin back and on liver. For skin, the noninvasive estimate is proportional to the true concentration but low by a factor of 3. Based on Monte Carlo modeling of multilayered systems, this underestimate is attributed to the layered structure of the skin and nonuniform AIPcS4 distribution. A comparison of the noninvasive concentration estimates to the postmortem assay results finds good agreement for liver tissue even though application of the diffusion model is not strictly justified.
Capacity of UV‐lrradiated Human Fibroblasts to Support Adenovirus DNA Synthesis Correlates with Transcription‐Coupled Repair and is Reduced in SV40‐Transformed Cells and Cells Expressing Mutant p53
Authors: McKay Bruce C. , Winrow Christopher , Rainbow Andrew J.
Published: January 2008

Abstract— We have examined the capacity of UV‐irradiated human diploid fibroblasts to support adenovirus (Ad) DNA synthesis in order to assess repair of UV‐damaged DNA. The capacity of UV‐irradiated xeroderma pigmentosum group C (XP‐C) fibroblasts to support Ad DNA synthesis was similar to that of UV‐irradiated normal diploid fibroblasts, following UV exposures of greater than 9 J/m2. In contrast, XP‐A, Cockayne syndrome groups A and B (CS‐A and CS‐B) fibroblasts were reduced in their capacity to support Ad DNA synthesis compared to normal diploid fibroblasts following a similar UV treatment. These results demonstrate that the capacity of UV‐irradiated fibroblasts to support Ad DNA synthesis correlates with their ability to remove UV‐induced DNA damage from active genes by transcription‐coupled repair (TCR). We also demonstrate that simian virus 40 (SV40)‐trans‐formed human fibroblasts, Li‐Fraumeni syndrome (LFS) fibroblasts, heterozygous for mutations in one allele of the p53 gene and immortalized LFS cell lines expressing only mutant p53 are reduced in their capacity to support Ad DNA replication following similar UV treatments. These results suggest that the capacity of UV‐irradiated cells to support viral DNA synthesis involves TCR of UV‐damaged DNA and is disrupted by SV40 transformation and expression of mutant p53. We propose a model in which p53‐dependent TCR regulates p53 stability in response to UV.
Mutation of Arginine 134 to Lysine Alters the pKas of Key Groups Involved in Proton Pumping by Bacteriorhodopsin
Authors: Misra Saurav , Martin Charles , Kwon Oh‐Hoon , Ebrey Thomas G. , Chen Ning , Crouch Rosalie K. , Menick Donald R.
Published: January 2008

Abstract— Arginine 134 is located near the extracellular surface of bacteriorhodopsin (bR) and may interact with one or more nearby glutamate residues. In the bR mutant R134K, light‐induced Schiff‐base deprotonation (formation of the M intermediate) exhibits several kinetic components and has a complex pH dependence. The kinetics and pH dependence of M formation were analyzed using the following general guidelines for interpreting M formation: (1) The fastest component of M formation reflects the redistribution of the Schiff‐base proton to D85, the usual proton acceptor, in response to the change in the proton affinities of the Schiff base and D85 early in the photocycle; (2) Two additional components of M formation reflect transitions between spectroscopically similar substates of M. By applying these guidelines, supplemented by information about the pKas of D85 and the proton release group from acid (purple‐to‐blue) and alkaline titrations of the absorption spectra of the unphotolyzed R134K pigment, we explain the pH dependence of M formation as being due to titration of the counter‐ion, D85, and of the proton release group. We calculate, in R134K, that the pKa of D85 is 4.6 in the unphotolyzed state, while the pKa of the proton release group is 8.0 in the unphotolyzed state but drops to ?5.8 in the M intermediate. The same value for the pKa of the proton release group in the M intermediate is obtained when we use photocurrent measurements to monitor proton release.

The altered values of these pKas relative to the corresponding values in wild‐type bR suggest that D85 and the proton release group are coupled more weakly in R134K than in the wild type.
Effects of Substitutions D73E, D73N, D103N and V106M on Signaling and pH Titration of Sensory Rhodopsin II
Authors: Zhu Jingya , Spudich Elena N. , Alam Maqsudul , Spudich John L.
Published: January 2008

Abstract— Several mutations in the repellent phototaxis receptor sensory rhodopsin II (SRII), in residues homologous to residues important in the related proton pump bacteriorhodopsin, were expressed in Pho81Wr–, a Halobacterium salinarum strain deficient in production of SRII and its transducer protein HtrII. The lack of production of SRII and HtrII is shown to be due to insertion of an ISH2 transposon into the promoter region upstream of the htrII‐sopH gene pair. Near wild‐type phototaxis responses are rescued in Pho81Wr– by expression of HtrII with D73E, D103N or V106M receptors. Partial responses are restored by the HtrII‐D73N pair. From absorption spectroscopy of his‐tag‐purified receptor protein from mutants D73N and D73E we conclude that Asp73 is the primary counterion to the protonated Schiff base in SRII, like the corresponding Asp85 in bacteriorhodopsin. The absorption maximum of SRII (487 nm) is shifted to 514 nm in mutant D73N, a 1080 cm−1 shift identical to that caused by D85N in bacteriorhodopsin. Acid titration of SRII also induces the red shift with a pK of 3.0 in wild type. The absorption shift and the pK are nearly the same in V106M and D103N, but the pK is raised to 5.1 in D73E, confirming that Asp73 is the residue responsible for this spectral transition.
Effect of UVB Radiation on Utilization of Inorganic Nitrogen by Antarctic Microalgae
Authors: Döhler G.
Published: January 2008

Abstract— The impact of UVB (280‐315 nm) radiation (WG 305) on uptake of 15N‐ammonium and 15N‐nitrate of marine phytoplankton from station 219 (47°W, 61.5°S) and sea ice‐algae from station 265 (22.6°W, 73.29°S) was studied during the Polarstern Cruise (EPOS III, Leg 3) to the Weddell Sea, Antarctica 1989. Uptake rates of 15NH4+ were higher and more affected by UVB radiation than those of 15N03‐. Pool sizes of the main amino acids changed in response to the used inorganic nitrogen source and UV exposure. Pools of glutamine, serine and glycine decreased, whereas those of alanine, asparagine and glutamate increased after UVB irradiation. The 15N‐incorporation into the amino acids was reduced as a result of UVB exposure of phytoplankton and ice algae. Results are discussed with reference to an inhibitory effect on the enzymes of both carbon and nitrogen metabolism as well as to adaptation strategies.
Measurements of the Protective Effect of Topically Applied Sunscreens using in vitro Three‐dimensional Dermal and Skin Equivalents
Authors: Augustin Corinne , Collombel Christian , Damour Odile
Published: January 2008

Abstract— For preventing or minimizing acute and chronic skin damage caused by UV radiation, the use of sunscreens is probably the most important measure. To screen the protective efficacy of new sunscreen molecules or formulations against UV rays, we evaluated as in vitro testing methods the use of two three‐dimensional models, a dermal equivalent (DE) and a skin equivalent (SE). The DE is composed of a porous collagen‐glycosaminoglycans‐chitosan matrix populated by normal human fibroblasts. The SE is comprised of a fully differentiated epidermis realized by seeding keratinocytes onto the DE. In this study, we demonstrated that the DE and SE models react to the deleterious effects of UVA and UVB. Then, we extended our research to the evaluation of their usefulness for photoprotection trials. Sunscreen agents (Euso‐lex 8020 and 6300) and commercially available sunscreens (chemical and physical filter formulations) that protect the skin against either UVA or UVB were evaluated. The tested products were applied (n = 6) topically (10 μL) and incubated for 30 min prior to irradiation over a range of UVA (0‐50 J/cm2) or UVB (0‐5 J/cm2). The photoprotection provided by the tested sunscreen molecules and formulations was evaluated by measurement of residual cellular viability 24 h postirradiation using the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetra‐zolium bromide (MTT) test and assessment of the inflammation response by interleukin‐la release assay. When sunscreens were applied prior to UV exposure, a higher residual cellular viability versus control was obtained, demonstrating the photoprotective effects of the tested products. These in vitro models could be used for screening tests to evaluate the protective effects of sunscreen molecules and formulations, especially for UVA trials because there is a lack of consensus for an in vivo method.
Sunscreen Protection Against Ultraviolet Radiation‐induced Pyrimidine Dimers in Mouse Epidermal DNA
Authors: Ley Ronald D. , Fourtanier Anny
Published: January 2008

Pyrimidine dimers were measured in epidermal DNA of SKH:HRI mice following exposure to solar‐simulated UV radiation (SSUV, 290–400 nm) or to UVA (320–400 nm). Mice were exposed to SSUV or UVA after topical application (2 mg/cm2) of vehicle, a UVB absorber (5% 2‐ethylhexyl p‐methoxycinnamate [2‐EHMC]), or a broad‐spectrum UVA absorber (5% Mexoryl®SX). The rates of induction of pyrimidine dimers in untreated animals were 5.4 ± 0.57 times 10‐4 (mean ± SEM) and 7.6 ± 0.95 times 10‐6 dimers per 108 Da of epidermal DNA per J/m2 of SSUV and UVA, respectively. Topical application of Mexoryl®SX reduced the rate of induction of pyrimidine dimers in SSUV‐exposed animals to 4.7 ± 0.44 times 10‐5 dimers per 108 Da per J/m2 for a dimer induction protection factor (PF) of 11.5 (5.4 times 10 4/4.7 times 10‐5). The rate of dimer induction in Mexoryl®SX‐treated, UVA‐ex‐posed mice was 0.95 ± 0.2 times 10‐6 dimers per 108 Da per J/m2 (PF = 8.0). The 2‐EHMC at a concentration of 5% (wt/wt) was significantly less effective than Mexoryl®SX in preventing the induction of pyrimidine dimers in animals exposed to either SSUV or UVA. The rates of dimer induction in 2‐EHMC‐treated mice were 8.2 ± 1.1 times 10‐5 and 3.8 ± 0.33 times 10‐6 dimers per Da per J/m2 of SSUV (PF = 6.6) and UVA (PF = 2.0), respectively. Upon normalizing to the efficacy for edema induction, UVA induced approximately one‐fourth the number of pyrimidine dimers per equivalent edematous response when compared to SSUV.
Light‐dependent Oxygen Consumption in Bacteriochlorophyll‐Serine‐treated Melanoma Tumors: On‐line Determination Using a Tissue‐inserted Oxygen Microsensor
Authors: Zilberstein Judith , Bromberg Avraham , Frantz Anatol , Rosenbach‐Belkin Varda , Kritzmann Amnon , Pfefermann Reuven , Salomon Yoram , Scherz Avigdor
Published: January 2008

Successful application of anticancer therapy, and especially photodynamic therapy (PDT) mediated by type II (PDTII) processes, depends on the oxygen content within the tumor before, during and after treatment. The high consumption of oxygen during type II PDT imposes constraints on therapy strategies. Although rates of oxygen consumption and repletion during PDTII were suggested by theoretical studies, direct measurements have not been reported. Application of a novel oxygen sensor allowed continuous and direct in situ measurements (up to a depth of 8–9 mm from the tumor surface and for several hours) of temporal variations in the oxygen partial pressure (pO2) during PDT. Highly pigmented M2R mouse melanoma tumors implanted in CD1 nude mice were treated with bacteriochlorophyll‐serine (Bchl‐Ser; a new photodynamic reagent) and were subjected to fractionated illumination (700 < λ. < 900 nm) at a fluence rate of 12 mW cm‐2. This illumination led to total oxygen depletion with an average consumption rate of 7.2 uAf(O2) s‐1. Spontaneous reoxygenation (at an average rate of 2.5 µM(O2)/s) was observed during the following dark period. These rates are in good agreement with theoretical considerations (Foster et al., Radiat. Res. 126, 296,1991 and Henning et al, Radiat. Res. 142, 221, 1995). The observed patterns of oxygen consumption and recovery during prolonged periods of light/dark cycles were interpreted in terms of vasculature damage and sensitizer clearance. The presented data support the previously suggested advantages of fractionated illumination for type II photodynamic processes.
Safety Analysis: Relative Risks of Ultraviolet Exposure from Fluorescence Spectroscopy and Colposcopy Are Comparable*
Authors: Brookner Carrie K. , Agrawal Anant , Trujillo E. Vanessa , Mitchell Michele Follen , Richards‐Kortum Rebecca R.
Published: January 2008

Fluorescence spectroscopy is a promising tool for use in the diagnosis of disease in human tissue. However, few published reports have evaluated the safety of this technique, despite the fact that many spectroscopic systems use UV illumination. This study determined the relative risk associated with light exposure from spectroscopic systems compared with the traditional light sources that are used to illuminate tissue and direct biopsies. We compared spectroscopic detection systems for the cervix to the colposcope, a low‐power microscope routinely used to illuminate the cervix, which does not cause any known photochemical damage. We measured the average spectral irradiance (W/[cm2nm]) and the average tissue exposure time during a diagnostic colposcopy examination. To quantify the relative risks, we multiplied illumination spectra by several action spectra from the literature and compared the areas under the curves corresponding to each procedure. The risk associated with the average power colposcope served as our basis for comparison. We conclude that the risks of illumination using spectroscopic systems are lower than or comparable to those already encountered in routine diagnostic procedures such as colposcopy with an average power colposcope. Spectroscopic examination can be associated with a somewhat higher risk than a colposcopy with the lowest power colposcope or a shorter than average colposcopy. The analysis presented can be repeated to estimate the magnitude of risks associated with other spectroscopic diagnostic devices.
Photophysical Properties of Pyrazinocoumarin Derivatives
Authors: Shim Sang Chul , Han Gyu Seok
Published: January 2008

Pyrazinocoumarin (PzC), 7‐methoxypyrazinocoumarin (7‐MOPzC) and 5,7‐dimethoxypyrazinocoumarin (5,7‐DMPzC) show the similar UV‐visible absorption spectra as the corresponding coumarins except for more distinct shoulders in the near UV absorption band (300–350 nm), probably due to n * transition. Fluorescence excitation spectra of PzC derivatives in nonpolar solvents have the lowest energy maxima in the region of the shoulders of UV‐visible absorption, indicating the lowest fluorescent state to have the same energy as these shoulders. Fluorescence quantum yields (ρF) of pyrazinocoumarins are on the order of 10 2‐10‐4, much lower than the corresponding coumarins. The activation energies (Ea(nr)) for nonradiative processes (internal conversion, intersystem crossing, etc.) determined by the temperature effect on the fluorescence are 10.2, 6.35 and 6.57 kj/mol for PzC, 7‐MOPzC and 5,7‐DMPzC, respectively. Phosphorescence emission spectra of PzC and 7‐MOPzC are structureless with φP of 0.12 and 0.17, respectively
Anthraquinone Photonucleases: A Surprising Role for Chloride in the Sequence‐Neutral Cleavage of DNA and the Footprinting of Minor Groove‐Bound Ligands
Authors: Armitage Bruce , Schuster Gary B.
Published: January 2008

Irradiation of water‐soluble anthraquinone (AQ) reagents in the presence of chloride ions results in the spontaneous, sequence‐neutral cleavage of DNA. Mechanistic studies indicate that cleavage is initiated by chlorine atoms, produced by charge transfer interaction between chloride anion and AQ triplet states. High‐resolution gel electrophoresis suggests that cleavage arises from abstraction of a hydrogen atom from C‐4′ of deoxyribose units. The targeting of this hydrogen, which is located in the minor groove of duplex DNA, can be effectively blocked by netropsin and, to a lesser degree, berenil, leading to photofootprinting of these minor groove‐binding drugs.
Continuous Photoreduction of Methyl Viologen Using Disubstituted Terthiophenes and EDTA in Aqueous Solution
Authors: Kim Young‐Sug , McNiven Scott , Ikebukuro Kazunori , Karube Isao
Published: January 2008

The continuous photoreduction of methyl viologen by 5,5″‐bis(aminomethyl)‐2,2′:5′,2″‐terthiophene (AT) and 2,2′:5′,2″‐terthiophene‐5,5″‐dicarboxylic acid (CT), using EDTA as a sacrificial electron donor, has been investigated in aqueous solution at various pH. Apparent rates and efficiencies of production of the methyl viologen radical cation (MV+) were found to be dependent on the pH, the concentrations of all three components and the intensity of the incident light. The highest conversion efficiency (77%) was shown by the bis(aminoniethyI (‐substituted terthiophene AT at pH 7.7. The quantum yield for the formation of MV+ under these conditions was 0.24, which is comparable with other common systems
Characterization of Two Light‐Harvesting Subunits Isolated from the Brown Alga Pelvetia canaliculata: Heterogeneity of Xanthophyll Distribution
Authors: Martino Alessandra De , Douady Dominique , Rousseau Bernard , Duval Jean Claude , Caron Lise
Published: January 2008

The main light‐harvesting fraction from Pelvetia canaliculata was isolated on a sucrose density gradient from digitonin‐solubilized chloroplasts. After further solubilization by dodecyl maltoside, the bulk fraction was separated into two subunits by preparative isoelectric focusing. The more acidic brown fraction was mainly composed of 22 kDa polypeptides having an apparent pI of 4.55. Its pigment composition was very simple, containing chlorophyll (Chi) a, Chi c and fucoxanthin. The in vivo spectral properties of fucoxanthin, namely a shift in light absorption to the green and efficient energy transmission to Chi a, were conserved in this subunit. No xanthophyll associated with photoprotection was found in this band, even when obtained from photoinhibited thalli. The less acidic green band contained predominantly 22 kDa polypeptides that were resolved into numerous components by denaturing isoelectric focusing. Its pigment composition was more complex, containing, in addition, pigments of the so‐called xanthophyll cycle. In photoinhibited thalli, about half of the violaxanthin was converted into antheraxanthin and zeaxanthin. All the pigments of the xanthophyll cycle were specifically associated with this subunit, and it may thus have a central role in the thermal dissipation of the absorbed light energy as postulated for light‐harvesting complex II isolated from green plants.
Effectiveness of the Accessory Yellow Fluorescent Protein in the Bacterial Luciferase Reaction Correlates with the Lifetime of the Peroxyhemiacetal Intermediate: The Stereochemistry of the Reaction
Authors: Sirokman Geza , Hastings J. Woodland
Published: January 2008

In the in vitro reaction of Vibrio fischeri Y‐1 luciferase, the dependence of the initial luminescence intensity (Io) and its rate of decay (kd) on the chain‐length of the aliphatic aldehyde are greatly altered by the presence of yellow fluorescent protein (YFP), which functions as an accessory emitter. Whereas with no YFP both kd and Io are maximum for chain lengths ≥ 12, the fraction of the light emitted from the accessory chromophore, measured as the ratio of yellow to blue light (Y/B), is greater with shorter chain‐length aldehydes. Thus, aldehydes that are least efficient in the absence of YFP are more efficient for causing yellow emission in its presence. These results are interpreted on the basis of the expected lifetimes of the peroxyhem‐iacetals with which YFP interacts: high values of kd reflect short peroxyhemiacetal lifetimes, hence less chance of interaction with YFP. The critical dependence on aldehyde chain‐length underlines the importance of stereochemical factors in the bacterial reaction, which are discussed here in the framework of a chemically initiated electron exchange luminescence model.
Chemiluminescence of Cypridina Luciferin Analogs. Part 3. MCLA Chemiluminescence with Singlet Oxygen Generated by the Retro‐Diels‐Alder Reaction of a Naphthalene Endoperoxide
Authors: Fujimori Ken , Komiyama Tomoko , Tabata Hideo , Nojima Takayuki , Ishiguro Katsuya , Sa‐waki Yasuhiko , Tatsuzawa Hidetaka , Nakano Minoru
Published: January 2008

The chemiluminescence of the Cypridina luciferin analog, 2‐methyl‐6‐(p‐methoxyphenyl)‐3,7‐dihydroirnidazo[1,2‐a]pyrazin‐3‐one (MCLA), with O2 (1Δg) generated by the retro‐Diels‐Alder reaction of 3‐(4′‐methyI‐l'‐naphthyl)‐propionic acid endoperoxide was studied in an aqueous solution with pH 7.12 at 37°C. The retro‐Diels‐Alder reaction occurs with a first‐order rate constant of (4.16 ± 0.13) × 10−4/s to quantitatively yield O2 (1Δg) and 3‐(4′‐methyl‐l'‐naphthyl (‐propionic acid. MCLA consumed equimolar amounts of O2 (1Δg) with a second‐order rate constant (6.96 ± 0.27) × 108/M/s to emit light in an aqueous solution with pH 7.12 at 37°C. The chemiluminescence spectrum was identified as the fluorescence spectrum of 2‐acetylamino‐5‐(p‐methoxyphenyl)pyrazine (OMCLA), a major chemiluminescence reaction. Chemiluminescence spectra and product yields for MCLA reactions with O21Δg, with O2 (3Σ−g) and with superoxide anion radicals are identical, suggesting that all of these reactions occur via a common MCLA‐2‐hydrope‐roxide intermediate formed by a combination of MCLA radicals and superoxide anion radicals. We have established practical use of NEPO as an O2 (1Δg) source and MCLA as a biological probe for detecting O2 (1Δg).
Photosensitized Oxidation of Oxopurines by Rose Bengal†
Authors: Murgida Daniel H. , Aramendía Pedro F. , Balsells Rosa Erra
Published: January 2008

Photosensitized oxidations of oxopurines (OP) as caffeine, theophylline, theobromine and 1,3,7‐trimethyluric acid (TMU) by Rose Bengal were investigated. In all cases photooxidations occur by a type II mechanism. Reactive and nonreactive 1O2 quenching rate constants by OP were determined in different solvents. Based on the correlations of the rate constants with different solvent parameters (α, β, ET[30], AN, DN, *,), the initial formation of an exciplex between 1O2 and OP is proposed that evolves to a zwitterionic transition state. Some reaction products were characterized, among them 3‐mefh‐yl‐5‐(methylamine)‐1,5‐dehydrohydantoin was obtained as the main photooxidation product of TMU. A reaction mechanism is proposed for the formation of this and other reaction products.
Assessment of the Effects of Various UV Sources on Inactivation and Photoproduct Induction in Phage T7 Dosimeter
Authors: Fekete A. , Vink A. A. , Gaspar S. , Berces A. , Modos K. , Ronto Gy. , Roza L.
Published: January 2008

The correlation between the biologically effective dose (BED) of a phage T7 biological dosimeter and the induction of cyclobutane pyrimidine dimers (CPD) and (6‐4) photoproducts ((6‐4)PD) in the phage DNA was determined using seven various UV sources. The BED is the inactivation rate of phage T7 expressed in HT7 units. The CPD and (6‐4)PD were determined by lesion‐specific monoclonal antibodies in an immunodot‐blot assay. The various lamps induced these lesions at different rates; the relative induction ratios of CPD to (6‐4)PD increased with increasing effective wavelength of irradiation source. The amount of total adducts per phage was compared to the BED of phage T7 dosimeter, representing the average number of UV lesions in phage. For UVC (200–280nm radiation) and unfiltered TL01 the number of total adducts approximates the reading; however, UV sources having longer effective wavelengths produced fewer CPD and (6‐4)PD. A possible explanation is that although the most relevant lesions by UVC are the CPD and (6‐4)PD, at longer wavelengths other photoproducts can contribute to the lethal damage of phages. The results emphasize the need to study the biological effects of solar radiation because the lesions responsible for the lethal effect may be different from those produced by various UV sources.
Spectrally Resolved Imaging of Cabot Rings and Howell‐Jolly Bodies
Authors: Rothmann Chana , Malik Zvi , Cohen Amos M.
Published: January 2008

The spectral characteristics of erythropoietic cellular inclusions stained by May‐Grunwald Giemsa (MGG) were determined by spectrally resolved imaging. Multipixel spectra were obtained from Cabot rings and Howell‐Jolly (HJ) bodies, displaying a range of wavelengths of transmitted light. The spectral characteristics of these inclusions were compared with those of isolated DNA, his‐tones (type II) and arginine‐rich histones (type VI), all stained by MGG. Results of single‐cell spectroscopy show that the spectra of Cabot rings and HJ bodies share spectral characteristics with the type II and type VI histones. However, no resemblance was found between Cabot rings and DNA spectra. The spectral analysis of hetero‐chromatin displayed a spectral pattern with characteristics of both DNA and histones, while the euchromatin showed a major contribution of the DNA component.
The Role of Oxygen in the Antiviral Activity of Hypericin and Hypocrellin
Authors: Park Jaehun , English Doug S. , Wannemuehler Yvonne , Carpenter Susan , Petrich Jacob W.
Published: January 2008

The light‐induced antiviral activity of hypericin and hypocrellin in the presence and absence of oxygen was examined under experimental conditions where the effect of oxygen depletion could be quantified. There was a significant reduction of light‐induced antiviral activity of hypericin and hypocrellin under hypoxic conditions. Interestingly, antiviral activity of hypocrellin was not observed at low oxygen levels at which hypericin retained measurable virucidal activity. This suggests that additional pathways, such as the generation of protons from excited states of hypericin, may enhance the biological activity of activated oxygen species.
Electron Transfer Processes in the Reactivity of Nonsteroidal Anti‐inflammatory Drugs in the Ground and Excited States
Authors: Moore Douglas E , Ghebremeskel Kifle A. , Chen Bruce B. C. , Wong Elaine Y. L.
Published: January 2008

The nonsteroidal anti‐inflammatory drugs (NSAID), naproxen, sulindac and indomethacin, were shown to donate electrons to nitro blue tetrazolium (NBT) when irradiated with UV light in deoxygenated aqueous buffer solution (pH 7.4, 30°C). The reaction was monitored spec‐trophotometrically by the appearance of the diformazan reduction product from NBT. The electron transfer process facilitates the decomposition of the drugs. Naproxen in the presence of NBT is photodegraded principally to the alcohol (2‐[1‐hydroxyethyl]‐6‐methoxynaphthalene) at a rate approximately 20‐fold faster than when irradiated alone in deoxygenated conditions. The photoproduct from naproxen also participates in the electron transfer to NBT but at a much slower rate than naproxen. Irradiation of sulindac or indomethacin in the presence of NBT caused the slow photoreduction of NBT to diformazan. In the absence of NBT, indomethacin and sulindac are essentially unreactive when irradiated in aqueous solution. The ability of a number of NSAID to act as electron donors in their ground state was studied by observing their oxidation by potassium peroxodisulfate in pH 7.0 phosphate buffer at 50°C. The HPLC analysis of the drug remaining showed that the 2‐arylpropionic acid NSAID (naproxen, ibuprofen, ketoprofen and suprofen) reacted at a rate equivalent to the thermal decomposition of peroxodisulfate. The major products were the same as detected in the photooxidation of these drugs, resulting from decarboxylation and oxygen addition but also included a dimeric compound. On the other hand, the NSAID that do not contain the propionic acid substituent all reacted more slowly with peroxodisulfate, enabling specific reaction rate constants to be evaluated.
Hypocrellin A Photosensitization Involves an Intracellular pH Decrease in 3T3 Cells
Authors: Chaloupka Roman , Sureau Franck , Kocisova Eva , Petrich Jacob W.
Published: January 2008

Abstract— The fluorescent pH probe carboxy‐seminaphtorhoda‐fluor‐1 (C‐Snarf‐1) has been used for laser microspectrofluorometric assays of intracellular pH in 3T3 mouse fibroblasts treated with hypocrellin A. These results are compared to those previously obtained with the structurally related hydroxylated polycyclic quinone, hypericin (Sureau et al, J. Am. Chem. Soc. 118, 9484‐9487, 1996). A mean local intracellular pH drop of 0.6 units has been observed in the presence of 1 μM hypocrellin A after 90 s of exposure to 0.1 μW of laser irradiation at 514.5 nm. The time evolution of the cytoplasm acidification for hypocrellin A‐treated cells is faster than that for cells treated by hypericin. Thus, release of protons from an excited state of hypocrellin A appears to be more efficient than that from hypericin. In addition, the pH dependence of the quenching of C‐Snarf‐1 fluorescence in 3T3 cells under continuous irradiation has been observed. It is shown here that under continuous illumination, a pH decrease is able to induce a modification of the intracellular binding equilibrium of C‐Snarf‐1 that results in an increase of C‐Snarf‐1 fluorescence intensity. This latter observation suggests that the protons generated upon the photoexcitation of hypericin or its analogs may be involved in the production of other photoreactive species. Finally, we suggest that, just as for hypericin, this pH drop may be involved in the antiviral and antitumor activity of hypocrellin A.
Solar UVR Exposures of Primary School Children at Three Locations in Queensland
Authors: Gies Peter , Roy Colin , Toomey Simon , MacLennan Robert , Watson Mignon
Published: January 2008

Abstract— The ultraviolet radiation (UVR) exposures of primary school children in Brisbane, Toowoomba and Mackay (latitudes 27°30′, 27°33′ and 21°15′ south, respectively) were assessed over a period of 2 weeks at each location using UVR‐sensitive polysulfone (PS) film badges attached at the shoulder. The students filled in questionnaires on their time spent outdoors for each day of the study. These data in conjunction with the ambient UVR measured by a detector/datalogger unit at each site were used to correlate the calculated exposures with those measured using the PS badges. Overall, the questionnaires indicated that the males spent more time outdoors and had higher measured UVR exposures than females. For both boys and girls at each location, there was a strong correlation between the mean measured UVR exposure and the ambient solar UVR at that location.
Photophysical Studies of Some 5,10,15,20‐Tetraarylethynylporphyrinatozinc(II) Complexes as Potential Lead Compounds for Photodynamic Therapy
Authors: Lacey Jackie A. , Phillips David , Milgrom Lionel R. , Yahioglu Gokhan , Rees Robert D.
Published: January 2008

The photophysics of 5,10,15,20‐tetraarylethynylporphyrinatozinc(II) complexes, 1 and 2, are reported. Compared to 5,10,15,20‐tetraphenylporphyrinatozinc(II) (ZnTPP), the UV/visible spectra of 1 and 2 have red‐shifted B and Q bands, with the Q bands of increased intensity relative to the B band. FIuorescence quantum yields and lifetimes and triplet quantum yields and lifetimes are similar to ZnTPP. However, quantum yields for in vitro singlet‐oxygen generation are much larger than for ZnTPP and for 2 the quantum yield is near unity. These findings suggest that the title compounds could be potential lead compounds as sensitizers for photodynamic therapy.
Cytotoxicity and Antiproliferative Effect of Hypericin and Derivatives after Photosensitization
Authors: Vandenbogaerde Ann L. , Delaey Els M. , Vantieghem Annelies M. , Himpens Bernard E. , Merlevede Wilfried J. , de Witte Peter A.
Published: January 2008

The toxicity on three human tumor cell lines (A431, HeLa and MCF7) of five phenanthroperylenequinones (hypericin and derivatives) and two perylenequinones (cercosporin and calphostin C) was investigated after photosensitization (4 J/cm2). Furthermore, the antiproliferative effect on HeLa cells was studied for the phenanthroperylenequinones. Hypericin, 2,5‐dibromohypericin, 2,5,9,12‐tetrabromohypericin and perylenequinones displayed a potent cytotoxic and antiproliferative effect in the nanomolar range. Hypericin dicarboxylic acid exhibited no photoactivity. In general, the antiproliferative activity correlated well with the photocytotoxicity. However, the nonphotocytotoxic compound hexamethylhypericin showed potent antiproliferative activity in the nanomolar range, probably exerting its action by protein kinase C inhibition. Without light irradiation, no cytotoxic and antiproliferative effect was observed for any photocytotoxic phenanthroperylenequinone compound. Furthermore, confocal laser microscopy revealed that the subcellular localization in A431 cells was similar for the photoactive compounds; the photosensitizers were mainly concentrated in the perinuclear region, probably corresponding with the Golgi apparatus and the endoplasmic reticulum. In addition, the accumulation of the photosensitizers in HeLa cells was investigated. All compounds except hypericin dicarboxylic acid were found to concentrate to a large extent in the cells. The compound 2,5,9,12‐tetrabromohypericin seemed intrinsically more effective than hypericin since the intracellular concentration of the bromoderivative was a magnitude of order lower than that of hypericin although both compounds showed similar photobiological activity.
Recombinant Phytochrome of the Moss Ceratodon purpureus: Heterologous Expression and Kinetic Analysis of Pr→ Pfr Conversion
Authors: Zeidler Mathias , Lamparter Tilman , Hughes Jon , Hartmann Elmar , Remberg Anja , Braslavsky Silvia , Schaffner Kurt , Gartner Wolfgang
Published: January 2008

Abstract— The phytochrome‐encoding gene Cerpu;PHY;2 (CP2) of the moss Ceratodon purpureus was heterologously expressed in Saccharomyces cerevisiae as a polyhistidine‐tagged apoprotein and assembled with phytochromobilin (P φ B) and phycocyanobilin (PCB). Nickel‐affinity chromatography yielded a protein fraction containing approximately 80% phytochrome. The holoproteins showed photoreversibility with both chromophores. Difference spectra gave maxima at 644/716 nm (red‐absorbing phytochrome [Pr]) far‐red‐absorbing phytochrome [Pfr]) for the PCB adduct, and 659/724 nm for the PφB‐adduct, the latter in close agreement with values for phytochrome extracted from Ceratodon itself, implying that PφB is the native chromophore in this moss species. Immunoblots stained with the antiphytochrome antibody APC1 showed that the recombinant phytochrome had the same molecular size as phytochrome from Ceratodon extracts. Further, the mobility of recombinant CP2 holophyto‐chrome on native size‐exclusion chromatography was similar to that of native oat phytochrome, implying that CP2 forms a dimer. Kinetics of absorbance changes during the Pr→ Pfr photoconversion of the PCB adduct, monitored between 620 and 740 nm in the microsecond range, revealed the rapid formation of a red‐shifted intermediate (I70o)> decaying with a time constant of ‐ 110 u.s. This is similar to the behavior of phytochromes from higher plants when assembled with the same chromophore. When following the formation of the Pfr state, two major processes were identified (with time constants of 3 and 18 ms) that are followed by slow reactions in the range of 166 ms and 8 s, respectively, albeit with very small amplitudes.
Pharmacokinetics of Tetra (m‐hydroxyphenyl)chlorin in Human Plasma and Individualized Light Dosimetry in Photodynamic Therapy
Authors: Glanzmann Thomas , Hadjur Christophe , Zellweger Matthieu , Grosjean Pierre , Forrer Martin , Ballini Jean‐Pierre , Monnier Philippe , van den Bergh Hubert , Lim Chang Kee , Wagnières Georges
Published: January 2008

The pharmacokinetics of the photosensitizer 5,10,15,20‐tetra(m‐hydroxyphenyl) chlorin(mTHPC) was investigated in the plasma of 20 patients by absorption and fluorescence spectroscopy. The temporal behavior was characterized by a rapid decrease in concentration during the first minutes after intravenous injection of 0.15 mg/kg mTHPC. A minimum concentration in the plasma was reached after about 45 min. The drug concentration then increased again, attaining a maximum after about 10 h, after which it decreased again with a halflife of about 30 h. Irradiation tests in the oral cavity at different time intervals after the injection revealed that the tissue re‐action was only partially correlated with the mTHPC plasma level. The tissue response was stronger at later drug‐light intervals (1–4 days) than during the first hours after injection even though the mTHPC plasma concentration was higher at the shorter times. Relative mTHPC concentrations were also measured in the mucosae of the oral cavity, the esophagus and the bronchi of 27 patients by light‐induced fluorescence spectroscopy using an optical fiber‐based spectrometer. These measurements were performed prior to photodynamic therapy (PDT), 4 days after injection of the photosensitizer. Highly significant linear correlations were found between the relative mTHPC concentrations in the mucosae of these three organs. Likewise, the plasma levels of mTHPC measured just before PDT were significantly correlated with the mTHPC concentrations in the three types of mucosae mentioned above. These results indicate that mTHPC plasma levels measured just before PDT can be used for PDT light dosimetry.
Dark and Photochemical Interactions of Dimethyltetrahydrobenzoangelicin with DNA
Authors: Miolo Giorgia , Lucchini Vittorio , Vedaldi Daniela , Guiotto Adriano , Caffieri Sergio
Published: January 2008

A study of dark interaction and photoreaction between 4,6‐dimethyltetrahydrobenzoangelicin (THBA) and DNA is described. 4,6‐Dimethyltetrahydrobenzoangelicin is a furocoumarin derivative in which 4’and 5’carbons are linked by a four‐methylene bridge. In spite of the bulky aliphatic ring, THBA forms a complex with DNA in the dark and, on UVA irradiation, reacts with pyrimidine bases of DNA yielding monoadducts only involving its furan side double bond. Two main photoproducts form: they derive from a C4‐cycloaddition to thymine and cytosine, respectively, and account for 56% and 39% of the total photoreaction yield. Both show cis‐syn configuration. Two other isomers, one with thymine and one with cytosine, formed with so much lower yield (ca 3 and 1%, respectively) that their structure could not be assigned. Furthermore, in spite of its angular structure, THBA induces a small number of crosslinks in DNA.