bluuebunny/crossref_metadata_2025 huggingface dataset:
Reassessment of the Electronic‐Conduction Behavior above the Verwey‐Like Transition of Ni2+‐ and Al3+‐Doped LiMn2O4
Authors: Fang Tsang‐Tse , Chung Han‐Yang
Published: July 2010

The electronic conduction behavior above the Verwey‐like transition temperature (Tv) of Ni2+‐ and Al3+‐doped LiMn2O4 has been reassessed. The nonadiabatic small‐polaron model is adopted to assess the conduction mechanism. The Jahn–Teller distortion and short‐range ordering are found to play a role in the variations of the lattice parameter and conduction behavior above Tv. It is also found that the effect of the dopant content on the activation energy is minor but is significant on the preexponential factor during the hopping process above Tv. In simultaneously comparing the effects of the dopants with quite different chemistry on the electronic‐conduction behavior in Ni2+‐ and Al3+‐doped LiMn2O4, it indeed provides a deep sight into understanding the fundamental conduction mechanism above Tv.
INTERACTION OF DIHYDROOROTATE DEHYDROGENASE WITH LIGHT*
Authors: Miller Richard W. , Kerr Carolyn T.
Published: July 2010

Abstract— Several flavoproteins are known to undergo photoactivated reduction by EDTA. However, the effects of visible light on the non‐heme iron containing flavoproteins have not been characterized previously. Dihydroorotate dehydrogenase was studied as an example of this class of enzymes. Interaction with visible light was found to be complex.

Under low intensity photoirradiation of long duration the anaerobic enzyme was partially reduced to a form having increased absorbance at 630 nm. Similar absorbance changes have been correlated with semiquinone species. However, the irradiated enzyme exhibited irreversible changes in catalytic function. Activity with NADH was greatly reduced and a portion of the flavin coenzyme content was labilized. Fluorescence intensity of the enzyme was markedly increased by exposure to light, confirming partial degradation of a catalytic site.

Isothermal irradiation with light of high intensity in the range 330–600 nm caused the enzyme to be reduced rapidly. Spectroscopic changes were observed which persisted after reoxidation of flavins. Intense new absorbance maxima between 310 and 330 nm together with a large decrase in absorbance at 450 nm were noted. Under controlled conditions approximately half of the total flavin and practically all of the bound FAD were labilized. NADH oxidase activity and NADH linked reduction of orotate were selectively lost. The correlation between FAD labilization and loss of activity strengthens the hypothesis that FAD represents the site of activity with NADH. Activity with NADH was partially restored by incubation of the irradiated enzyme with FAD or FMN.
REPAIR OF 8‐METHOXYPSORALEN INDUCED DNA INTERSTRAND CROSS‐LINKS IN Tetrahymena thermophila
Authors: Nielsen Peter Eigil , Køosber Lars
Published: July 2010

Abstract— The protozoan Tetrahymena thermophila was treated with 8‐methoxypsoralen in combination with long wavelength ultraviolet irradiation and the DNA‐repair response was studied. Following the treatment a lag‐period in cell proliferation was observed, the duration of which was proportional to the amount of psoralen used, and both swelling and deformation of the cells were observed. The treatment with 3 μg 8‐methoxypsoralen/mℓ and a light dose of 8 kJ m‐2 resulted in a 10‐fold decrease in DNA and RNA synthesis activity, while the protein synthesis was only moderately affected. Using the same conditions the lag‐period was 30 h, and during this time the psoralen induced DNA interstrand cross‐links were removed. Alkaline elution experiments showed that the repair process involves DNA single strand scissions, whereas no double strand DNA scissions were detected.
PHOTOTAUTOMERISM OF LUMICHROME IN METHANOL‐ACETIC ACID MIXTURES. A STEADY‐STATE AND TIME‐RESOLVED FLUORESCENCE STUDY
Authors: Koziolowa A. , Visser A. J. W. G. , Koziol J.
Published: July 2010

Abstract— Fluorescence lifetimes of 3‐methyllumichrome dual fluorescence at 440 nm (alloxazinic) and 520 nm (isoalloxazinic) and of 1,3‐dimethyllumichrome, which is unable to phototautomerize, at the same wavelengths have been measured in methanol‐acetic acid mixtures. The fluorescence decays of both lumichromes studied are exponential and the phototautomeric fluorescence of 3‐methyllumichrome is created within approximately 50 ps. From the initial values of about 0.9 ns (alloxazinic) and 6.4 ns (isoalloxazinic) in 5% acetic acid the lifetimes shorten considerably with increasing acid concentration reaching 0.2 ns for 1,3‐dimethyllumichrome and 80 ps for the alloxazinic and 2.4 ns for the isoalloxazinic form of 3‐methyllumichrome in pure acid. Static and dynamic fluorescence quenching constants were estimated. The differences in the quenching rate and equilibrium constants of both lumichromes are interpreted in terms of different equilibria of hydrogen bond formation in ground and excited state as influenced by steric effects of the methyl substituent at the N‐l position in 1,3‐dimethyl. The hydrogen bonding atN–10 of 3‐methyllumichrome with acetic acid is a prerequisite for additional hydrogen bonding at N‐l enabling excited state proton transfer.
PURINE PHOTOPRODUCTS*
Authors: Duker Nahum J. , Gallagher Patricia E.
Published: July 2010

Abstract— DNA purine modifications by ultraviolet irradiation have not been as extensively studied as those of pyrimidines. However, a number of such reactions have been identified. These include photochemical addition of amino acids, photoalkylation by alcohols, amines and other compounds, photochemical activation of procarcinogens to mutagenic electrophiles, and formation of covalent linkages between DNA purines and adjacent bases. The recent characterization of two adenine‐adenine di‐adducts and the finding of endonucleases from two sources that incise ultraviolet‐irradiated DNA at purine photoproducts indicate the possible biological importance of these moieties.
THE PHOTOCHEMISTRY OF p‐AMINOBENZOIC ACID
Authors: Shaw Anthony A. , Wainschel Larry A. , Shetlar Martin D.
Published: July 2010

Abstract— We have studied the photoreactions occurring when p‐aminobenzoic acid (PABA), a component of some sunscreens, is irradiated in aqueous solution. These studies were carried out in the presence and absence of oxygen, using light of Λ= 254 nm as well as light of wavelengths greater than 290 nm. In deoxygenated solution between pH 7.5 and 11.0, we found two photoproducts that were identified as 4‐(4′‐aminophenyl)aminobenzoic acid (I) and 4‐(2′‐amino‐5′‐carboxy‐phenyl)aminobenzoic acid (V); we used H and 13C NMR, electron impact mass spectrometry and synthesis by an independent route to identify each of these compounds. Rapid discoloration of the photolyzed sample was observed when PABA was irradiated in aerated solution. Although a number of products were detected under these conditions, the three most abundant stable compounds have been isolated and identified as 4‐amino‐3‐hydroxybenzoic acid, 4‐aminophenol and 4‐(4′‐hydroxyphenyl)aminobenzoic acid (IV). The latter compound was shown to result from rapid photo‐induced oxidation of I in the presence of oxygen. Even in the presence of trace amounts of oxygen, the yield of I was significantly reduced in favor of IV. Studies of the thermal oxidation of I, coupled with evidence gathered from studies of the photochemistry of incompletely deoxygenated PABA solutions, indicate that 4‐(2,5‐cyclohexadien‐4‐one)iminobenzoic acid (III) is an intermediate on the pathway between I and IV.

Qualitatively, we found that the photochemical reactions resulting from irradiation of PABA solutions with Λ= 254 nm light and light with Λ > 290 nm were the same. The quantum yields for formation of I and V are highly pH dependent, both being less than 10–4 at pH 7 and rising steadily to values greater than 10–3 at pH 11. The detailed pH dependence suggests that the deprotonated PABA radical cation may be an important intermediate entering into the reactions forming I and IV.
RADIATIONLESS DEACTIVATION AND FLUORESCENCE OF SELECTED PYRIDONES
Authors: Guzzo Anthony V. , Nelson David A.
Published: July 2010

Abstract— Numerous 3‐position derivatives of 2‐hydroxy pyridine, also known as 2‐pyridone, were synthesized and their optical absorption and fluorescence spectra examined. The quantum yield of emission varied from near zero to near unity depending on the kind of substitution made and the solvent. Data are presented that argue for the π‐π* nature of the first excited state in all cases. It was concluded that intramolecular hydrogen bonding controls the extent of internal conversion and hence the amount of fluorescence. It is proposed that this hydrogen bonding suppresses the low energy out of plane vibrations necessary for internal conversion as required by the proximity effect. From studies of the temperature dependence of the emissions, it appeared that the energy separation of the first two excited states, in all cases ˜12.6 ± 2 kJ/mol (3000 ± 500 cal/mol), is not correlated to the extent of relaxation
ROOM‐TEMPERATURE PHOSPHORESCENCE FROM AZURIN DERIVATIVES. PHOSPHORESCENCE QUENCHING IN OXIDIZED NATIVE AZURIN
Authors: Klemens Frank K. , McMillin David R.
Published: July 2010

Abstract— The tryptophan phosphorescence from a series of derivatives of Pseudomonas aeruginosa azurin has been monitored at 30°C in pH 8.5 buffer solution. The phosphorescence lifetimes fall in the range of 230–270 ms for deoxygenated solutions of derivatives containing Cd(II), Cu(I), Co(II), Ni(II), Hg(II) or apoazurin. A weak signal with a lifetime of ca 130 ms is observed from solutions of oxidized native azurin, but this component is ascribed to a modified form of azurin in solution, i.e. protein heterogeneity, on the basis of the unique sensitivity to quenching by dioxygen. Aside from this minor component, the tryptophan phosphorescence in the Cu(II) protein appears to be fully quenched. The quenching is assigned an electron‐transfer mechanism involving transient reduction of the metal center. The same mechanism is deemed to be responsible for fluorescence quenching in oxidized native azurin as well. These observations are of interest because aromatic groups like tryptophan may be conduits for physiological electron‐transfer processes involving the copper center.
A HIGHLY REACTIVE HETEROATOM ANALOG OF RETINAL AND ITS INTERACTION WITH BACTERIORHODOPSIN
Authors: Birnbaum Dov , Seltzer Stanley
Published: July 2010

Abstract— C18 formate ester (5) [2‐(6‐methyl‐8‐(2,6,6‐trimethyl‐1‐cyclohexen‐1‐yl)‐3E,5E,7E‐octatrienyl formate], a highly reactive analog of retinal, was synthesized and its interaction with bacterioopsin studied. The formate ester, in the absence of purple or bleached membrane, undergoes very rapid reaction (tl/2= 0.9 min) in neutral buffer but with membrane present it diffuses more rapidly into the membrane where it reacts slowly. Incorporation of 5 in the membrane results in a 38 nm (3900 cm‐1) red shift which remains after reconstitution with retinal. Similar experiments with the corresponding C18 alcohol (4) results in a red shift, but this absorption blue shifts upon reconstitution with retinal. Washing the formate ester‐treated membrane with bovine serum albumin or the corresponding lyophilized preparation with hexane, treatments that remove retinal oxime, fails to remove the UV‐visible absorption, suggesting that a covalent bond between the C18 moiety and a nucleophilic group of the protein has probably formed.
RESONANCE‐ENHANCED CARS SPECTROSCOPY OF BILIPROTEINS. INFLUENCE OF AGGREGATION and LINKER PROTEINS ON CHROMOPHORE STRUCTURE IN ALLOPHYCOCYANIN (Mastigocladus laminosus)
Authors: Schneider S. , Prenzel C.‐J. , Brehm G. , Gottschalk L. , Zhao K.‐H. , Scheer H.
Published: July 2010

Abstract— Resonance‐enhanced coherent anti‐Stokes Raman spectra (CARS) are reported for monomers and for trimers with and without linker proteins of allophycocyanin isolated from Mastigocladus laminosus. The CARS spectrum of the monomer is independent of the presence of linker proteins and is very similar to that of phycocyanin monomers indicating that the equivalent chromophores exhibit like structures in both biliproteins. Large differences are, however, observed between the spectra of phycocyanin trimers and those of allophycocyanin trimers with or without linker proteins (Lc8,9). The observed differences between monomer and trimer spectra are consistent with a change of the α‐chromophore‐protein arrangement upon aggregation without linker. If linker proteins are present in the trimer, then additional geometry changes of the β‐chromophores are induced; these could relate to a transition from the 15Z‐anti to 15Z‐syn conformation.
PROTECTION AGAINST ULTRAVIOLET‐B RADIATION‐INDUCED LOCAL and SYSTEMIC SUPPRESSION OF CONTACT HYPERSENSITIVITY and EDEMA RESPONSES IN C3H/HeN MICE BY GREEN TEA POLYPHENOLS
Authors: Katiyar Santosh K. , Elmets Craig A. , Agarwal Rajesh , Mukhtar Hasan
Published: July 2010

Abstract— Exposure of skin to UV radiation can cause diverse biological effects, including induction of inflammation, alteration in cutaneous immune cells and impairment of contact hypersensitivity (CHS) responses. Our laboratory has demonstrated that oral feeding as well as topical application of a poly‐phenolic fraction isolated from green tea (GTP) affords protection against the carcinogenic effects of UVB (280–320 nm) radiation. In this study, we investigated whether GTP could protect against UVB‐induced immunosuppression and cutaneous inflammatory responses in C3H mice. Immunosuppression was assessed by contact sensitization with 2,4‐dinitrofluorobenzene applied to UVB‐irradiated skin (local suppression) or to a distant site (systemic suppression), while double skin‐fold swelling was used as the measure of UVB‐induced inflammation. Topical application of GTP (1–6 mg/animal), 30 min prior to or 30 min after exposure to a single dose of UVB (2 kj/m2) resulted in significant protection against local (25–90%) and systemic suppression (23–95%) of CHS and inflammation in mouse dorsal skin (70–80%). These protective effects were dependent on the dose of GTP employed; increasing the dose (1–6 mg/animal) resulted in an increased protective effect (25–93%). The protective effects were also dependent on the dose of UVB (2–32 kJ/m2). Among the four major epicatechin derivatives present in GTP, (‐)‐epigallocatechin‐3‐gallate, the major constituent in GTP, was found to be the most effective in affording protection against UVB‐caused CHS and inflammatory responses. Our study suggests that green tea, specifically polyphenols present therein, may be useful against inflammatory dermatoses and immunosuppression caused by solar radiation.
Induction of Chromosome Aberrations and Delayed Genomic Instability by Photochemical Processes
Authors: Limoli Charles L. , Day Joseph P. , Ward John F. , Morgan William F.
Published: July 2010

Exponentially growing cells cultured in medium containing bromodeoxyuridine, then exposed to UVA light in the presence of the dye Hoechst 33258, show significant levels of DNA strand breaks and base damage. This dye–bromodeoxyuridine–UVA photolysis treatment is markedly cytotoxic. We now demonstrate that exposure of cells to the agents used in photolysis leads directly to the formation of chromosome aberrations. Furthermore, we demonstrate that this photochemical treatment induces delayed chromosomal instability in clonal populations derived from single progenitor cells surviving photolysis. These results suggest that photolysis‐induced DNA damage leads to chromosome rearrangements that could account for the observed cytotoxicity. Furthermore, in those cells surviving photolysis, the delayed effects of this treatment can be observed several generations after exposure and are manifested as compromised genomic integrity.
Photophysics of Melatonin in Different Environments
Authors: Rath1 M. C. , Mahal H. S. , Mukherjee T.
Published: July 2010

Abstract— Melatonin (N‐acetyl‐5‐methoxytryptamine) is a naturally occurring hormone with a structural resemblance to tryptophan. Its fluorescence is solvent dependent and strongly quenched in the presence of oxygen. Fluorescence quenching in aqueous and organic solutions have been studied in the presence of different quenchers. A 1: 1 inclusion complex formation between melatonin and different cyclodextrins in aqueous solution has been observed. The effects of microheterogeneous media provided by cyclodextrins, micelles and reverse micelles on the fluorescence characteristics of melatonin have been investigated. The water‐soluble inorganic quenchers like KBr and KI were unable to quench the fluorescence of melatonin dissolved in a microemulsion consisting of surfactant + cyclohexane + 1‐propanol + water, whereas the organic quenchers like CC14 and CHC13 were able to quench the fluorescence with a rate constant (on the order of 108 dm3 mol−1 s−1) quite similar to that in neat organic solvents.
Inhibition of Various Steps in the Replication Cycle of Vesicular Stomatitis Virus Contributes to Its Photoinactivation by AIPcS4 or Pc4 and Red Light
Authors: Moor Anne C. E. , Compel Angeline E. Wagenaars‐van , Hermanns Ralph C. A. , van der Meulen Jannes , Smit Jolanda , Wilschut Jan , Brand Anneke , Dubbelman Tom M. A. R. , VanSteveninck John
Published: July 2010

Abstract— Vesicular stomatitis virus (VSV) was used as a model virus to study the processes involved in photoinactivation by aluminum phthalocyanine tetrasulfonate (AlPcS4) or silicon phthalocyanine HOSiPcOSi(CH3)2(CH2)3N(CH3)2 (Pc4) and red light. Previously a very rapid decrease in the intracellular viral RNA synthesis after photodynamic treatment was observed. This decrease was correlated to different steps in the replication cycle. Binding of VSV to host cells and internalization were only slightly impaired and could be visualized by electron microscopy. The capability of the virus to fuse with membranes in an acidic endosomal environment was studied using both pyrene‐labeled liposomes and a hemolysis assay as a model. These tests indicate a rapid decrease of fusion capacity after AlPcS4 treatment, which correlated with the decrease in RNA synthesis. For Pc4 treatment no such correlation was found. The fusion process is the first step in the replication cycle, affected by AlPcS4 treatment, but also in vitro RNA polymerase activity was previously shown to be inhibited. Inactivation of VSV by Pc4 treatment is apparently caused by damage to a variety of viral components. Photodynamic treatment of virus suspensions with both sensitizers causes formation of 8‐oxo‐7,8‐dihydroguanosine in viral RNA as measured by HPLC with electrochemical detection. This damage might be partly responsible for inhibition of the in vitro viral RNA polymerase activity by photodynamic treatment.
Characterization of Protein Complexes Containing Nucleoside Diphosphate Kinase with Characteristics of Light Signal Transduction through Phytochrome in Etiolated Pea Seedlings
Authors: Ogura Takahiro , Tanaka Norifumi , Yabe Naoto , Komatsu Setsuko , Hasunuma Kohji
Published: July 2010

Abstract— At 5 days after sowing of pea seeds in darkness, intact seedlings were either irradiated with red light for 40 s at 50 μmol/m2/s at the third internode or with red light as above and then with far‐red light for 180 s at 0.4 μmol/m2/s, and the stems were sectioned from below the hook (mainly the third internodes) and placed in liquid N2 in a mortar. The samples were well ground, and after the addition of extraction buffer, homogenates were centrifuged to prepare the crude membrane and soluble fractions. Red‐light irradiation increased the phosphorylation of an 18 kDa protein, while far‐red‐light irradiation decreased it. The 18 kDa protein (formerly 15 kDa protein) was identified as nucleoside diphosphate kinase (EC 2.4.6) (NDP kinase) by western blotting using an NDP kinase‐specific antibody. The membrane and the soluble fractions of the red‐light‐irradiated samples were separated by native polyacrylamide gel electrophoresis. The protein complexes prepared from the membrane and soluble fractions differed in their mobilities, as determined by two‐dimensional electrophoresis and nonequilibrium pH gradient electrophoresis. The major protein spots from both samples were cut out from the gel and tested for NDP kinase and protein kinase activity. Both protein preparations showed NDP kinase activity and changes from nucleoside diphosphates and deoxynucleoside diphosphates to nucleoside triphosphates and deoxynucleoside triphosphates in the presence of [γ‐32P]ATP. Both preparations showed protein kinase phosphorylation of myelin basic protein (MBP) rather than histone H1 as protein substrates, suggesting that NDP kinase possesses a function similar to that of MAP kinase.
Detection of Dysplastic Lesions by Fluorescence in a Model of Chronic Colitis in Rats After Local Application of 5‐Amlnolevullnic Acid and its Esterified Derivatives¶
Authors: Endlicher Esther , Rümmele Petra , Hausmann Florian , Rath Heiko C. , Knüchel Ruth , Krieg Rene C. , Schölmerich Jürgen , Messmann Helmut
Published: July 2010

5‐Aminolevulinic acid (ALA) and ALA ester‐induced protoporphyrin IX (PPIX) fluorescence are used for photodynamic diagnosis and therapy with promising results. The aim of the present study was to investigate the detection of dysplastic lesions by fluorescence after topical application of ALA and different esterified derivatives in a model of chronic colitis in rats. In female CD rats chronic colitis was induced by oral application of 5% dextrane sulfate sodium. ALA was used at different concentrations (0.072 and 0.036 mol/L). ALA‐methylester (m‐ALA), ALA‐hexylester (h‐ALA) and ALA‐benzylester (b‐ALA) were used at a concentration of 0.003, 0.002 and 0.002 mol/L, respectively. Fluorescence was examined under blue light, and histological findings of fluorescent and nonfluorescent biopsy specimens were recorded. Using ALA at a concentration of 0.072 mol/L, all dysplastic lesions (8/8) showed fluorescence (sensitivity 100%). Specificity was low at 57%. Reducing the concentration to 0.036 mol/L resulted in a sensitivity of only 56% (5/9) with an increase in specificity to 76%. On using h‐ALA, sensitivity was 60% (3/5) with a specificity of 51%. Using m‐ALA and b‐ALA, sensitivity values were 25% and 33%, and values for specificity were 62% and 63%, respectively. Despite a low number of dysplastic lesions, the results of this study indicate that ALA ester‐induced PPIX fluorescence has the potential for the detection of premaligant lesions but was not superior to ALA. ALA esters were used in 18‐ to 36‐fold lower concentrations compared with ALA.
The Spatial Distribution of Optical Properties in the Ultraviolet and Visible in an Aquatic Ecosystem¶
Authors: Bracchini Luca , Loiselle Steven , Dattilo Arduino Massimo , Mazzuoli Stefania , Cózar Andrés , Rossi Claudio
Published: July 2010

In aquatic ecosystems, the UV and visible radiation environment is strongly influenced by variation in the chemical and physical parameters of the ecosystems. In shallow lakes, highly heterogeneous water characteristics produce a wide variety of optical environments. Such ecosystems require analysis approaches that consider a potential variability. In this study, 77 stations were used to characterize the optical properties of a shallow lake (open water surface 54 km2). The vertical attenuation of solar radiation at 305,313,320 and 340 nm and at photosynthetically active radiation was measured during the seasonal cycle. Dissolved organic matter (DOM), turbidity, fluorescence, pH, temperature, conductance and dissolved oxygen were simultaneously measured. The spatial variation of the extinction spectra of the dissolved fraction at each sampling station was also measured and analyzed between 270 and 400 nm. The spatial heterogeneity of the lake was examined by determining the distributions of the attenuation coefficients and biooptical parameters at high spatial resolution and describing the distributions in a series of maps. The methodology permitted a quantitative description of the interaction between solar radiation and aquatic ecosystems as well as a spatial classification of the dominating processes within the lake. This included the determination of the role played by DOM loading and changing chemical properties within the lake optical environment.
Binding, aggregation and photochemical properties of methylene blue in mitochondrial suspensions
Authors: Gabrielli Dino , Belisle Eduardo , Severino Divinomar , Kowaltowski Alicia J. , Baptista Mauricio S.
Published: July 2010

Methylene Blue (MB) has well‐established photochemical properties and has been used in a variety of photochemical applications including photodynamic therapy. Despite the fact that most of MB's cytotoxic effects in cells are attributed to mitochondrial damage, the interactions of this dye with mitochondria and the consequent effects on photochemical properties have not yet been fully determined. We monitored MB binding, aggregation and its ability to release singlet oxygen (1O2) on irradiation when interacting with mitochondrial suspensions. MB actively binds to mitochondria and enters the matrix in a manner stimulated by the mitochondrial proton potential and by the increase in mitochondrial concentrations. The greater accumulation of MB in mitochondria with elevated proton potentials or those treated with high concentrations of MB results in the formation of MB dimers, previously shown to be less effective generators of 1O2. Accumulation of MB within mitochondria with high membrane potentials also results in the reduction of MB to the photochemically inactive leuco‐MB. Indeed, irradiation of mitochondria with high proton potentials in the presence of MB results in the generation of approximately half the quantity of 1O2 compared with 1O2 generated in mitochondria with low proton potentials. These differences in photochemical properties should influence the cytotoxic effects of photodynamic treatment in the presence of MB.
Photodynamic Characterization and In Vitro Application of Methylene Blue‐containing Nanoparticle Platforms¶
Authors: Tang Wei , Xu Hao , Kopelman Raoul , Philbert Martin A.
Published: July 2010

This article presents the development and characterization of nanoparticles loaded with methylene blue (MB), which are designed to be administered to tumor cells externally and deliver singlet oxygen (1O2) for photodynamic therapy (PDT), i.e. cell kill via oxidative stress to the membrane. We demonstrated the encapsulation of MB, a photosensitizer (PS), in three types of sub‐200 nm nanoparticles, composed of polyacrylamide, sol‐gel silica and organically modified silicate (ORMOSIL), respectively. Induced by light irradiation, the entrapped MB generated 1O2), and the produced 1O2 was measured quantitatively with anthracene‐9, 10‐dipropionic acid, disodium salt, to compare the effects of different matrices on 1O2 delivery. Among these three different kinds of nanoparticles, the polyacrylamide nanoparticles showed the most efficient delivery of 1O2 but its loading of MB was low. In contrast, the sol‐gel nanoparticles had the best MB loading but the least efficient 1O2 delivery. In addition to investigating the matrix effects, a preliminary in vitro PDT study using the MB‐loaded polyacrylamide nanoparticles was conducted on rat C6 glioma tumor cells with positive photodynamic results. The encapsulation of MB in nanoparticles should diminish the interaction of this PS with the biological milieu, thus facilitating its systemic administration. Furthermore, the concept of the drug‐delivering nanoparticles has been extended to a new type of dynamic nanoplatform (DNP) that only delivers 1O2. This DNP could also be used as a targeted multifunctional platform for combined diagnostics and therapy of cancer.
WST11, A Novel Water‐soluble Bacteriochlorophyll Derivative; Cellular Uptake, Pharmacokinetics, Biodistribution and Vascular‐targeted Photodynamic Activity Using Melanoma Tumors as a Model¶
Authors: Mazor Ohad , Brandis Alexander , Plaks Vicki , Neumark Eran , Rosenbach‐Belkin Varda , Salomon Yoram , Scherz Avigdor
Published: July 2010

WST11 is a novel negatively charged water‐soluble palladiumbacteriochlorophyll derivative that was developed for vascular‐targeted photodynamic therapy (VTP) in our laboratory. The in vitro results suggest that WST11 cellular uptake, clearance and phototoxicity are mediated by serum albumin trafficking. In vivo, WST11 was found to clear rapidly from the circulation (t1/2= 1.65 min) after intravenous bolus injection in the mouse, whereas a longer clearance time (t1/2= 7.5 min) was noted in rats after 20 min of infusion. The biodistribution of WST11 in mouse tissues indicates hepatic clearance (t1/2= 20 min), with minor (kidney, lung and spleen) or no intermediary accumulation in other tissues. As soon as 1 h after injection, WST11 had nearly cleared from the body of the mouse, except for a temporal accumulation in the lungs from which it cleared within 40 min. On the basis of these results, we set the VTP protocol for a short illumination period (5 min), delivered immediately after WST11 injection. On subjecting M2R melanoma xenografts to WST11‐VTP, we achieved 100% tumor flattening at all doses and a 70% cure with 9 mg/kg and a light exposure dose of 100 mW/cm2. These results provide direct evidence that WST11 is an effective agent for VTP and provide guidelines for further development of new candidates.
Effects of Short‐ and Long‐term Ultraviolet B Irradiation on the Immune System of the Common Carp (Cyprinus carpio)¶
Authors: Markkula S. Eveliina , Salo Harri M. , Immonen Anu K. , Jokinen E. Ilmari
Published: July 2010

Carp (Cyprinus carpio) were repeatedly exposed to 0, 60, 120 and 240 mJ/cm2 ultraviolet B (UVB) radiation three times in 1 week (short‐term exposure) or 12 times in 4 weeks (long‐term exposure). The effect of UVB on the functioning of the carp immune system was studied on day 2 after the final irradiation. After short‐term UVB exposure, the whole‐blood respiratory burst and cytotoxic activity were markedly enhanced, with parallel responses in both the number of circulating granulocytes and in the plasma cortisol concentration of the fish. These changes were not detectable after long‐term exposure. The respiratory burst by head kidney granulocytes was suppressed dose dependently after both exposures, but cytotoxic activity was not affected. Exposure to UVB also modulated lymphocyte functions: nonstimulated and PHA‐stimulated proliferation of head kidney lymphocytes in vitro was enhanced by both short‐term and long‐term exposure. LPS‐stimulated proliferation was not affected by exposure nor was the number of immunoglobulin‐secreting cells in the head kidney. In long‐term exposure, the highest dose reduced the level of plasma IgM. This study indicates that UVB irradiation induces immunomodulation in the blood and head kidney of the carp and that the effects of short‐ and long‐term exposure differ from each other. The results emphasize the potentially harmful impact of increased solar UVB radiation on fish immune functions.
Encuentros Latinoamericanos de Fotoquímica y Fotobiología (ELAFOT): The Latin‐American Photochemical and Photobiological Community¶
Authors: Braslavsky Silvia E. , Simon John D.
Published: July 2010

The photochemical and photobiological researchers in Latin American meet biannually at a regional meeting known as Encuentros Latinoamericanos de Fotoquímica y Fotobiología (ELAFOT). The goals of this series of meetings are to discuss leading scientific work, to become acquainted with the latest research findings in the discipline, to exchange ideas, to initiate collaborations between groups and to strengthen the scientific interactions between young researchers and senior experts from the region and from developed countries. During 8–12 November 2004, the eighth such meeting took place in La Plata, Argentina. In this introduction we present a brief history of the ELAFOT meetings and a summary of the most recent gathering and the papers presented in this Symposium‐in‐Print.
Porphyrin‐fullerene C60 Dyads with High Ability to Form Photoinduced Charge‐separated State as Novel Sensitizers for Photodynamic Therapy¶
Authors: Milanesio M. Elisa , Alvarez M. Gabriela , Rivarola Viviana , Silber Juana J. , Durantini Edgardo N.
Published: July 2010

The photodynamic activities of a porphyrin‐C60 dyad (P‐C60) and its metal complex with Zn(II) (ZnP‐C60) were compared with 5‐(4‐acetamidophenyl)‐10,15,20‐tris(4‐methoxyphenyl)‐porphyrin (P), both in homogeneous medium‐bearing photooxidizable substrates and in vitro on the Hep‐2‐human‐larynx‐carcinoma cell line. This study represents the first evaluation of dyads, with a high capacity to form a photoinduced charge‐separated state, to act as agents to inactivate cells by photodynamic therapy (PDT). Absorption and fluorescence spectroscopic studies were performed in toluene and N,N‐dimethylformamide (DMF). The emission of the porphyrin moiety in the dyads is strongly quenched by the attached fullerene C60 moiety. The singlet molecular oxygen, O2(1Δg), productions (φΔ) were determined using 9,10‐dimethylanthracene (DMA). The values of φΔ were strongly dependent on the solvent's polarity. Comparable φΔ values were found for dyads and P in toluene, while O2(1Δg) production was significantly diminished for the dyads in DMF. In more polar solvent, the stabilization of charge‐transfer state takes place, decreasing the efficiency of porphyrin triplet‐state formation. Also, both dyads photosensitize the decomposition of L‐tryptophan in DMF. In biological medium, no dark cytotoxicity was observed using sensitizer concentrations ≤1 μM and 24 h of incubation. The uptake of sensitizers into Hep‐2 was studied using 1 μM of sensitizer and different times of incubation. Under these conditions, a value of ∼1.5 nmol/106 cells was found between 4 and 24 h of incubation. The cell survival after irradiation of the cells with visible light was dependent upon light‐exposure level. A higher photocytotoxic effect was observed for P‐C60, which inactivates 80% of cells after 15 min of irradiation. Moreover, both dyads keep a high photoactivity even under argon atmosphere. Thus, depending on the microenvironment where the sensitizer is localized, these compounds could produce biological photodamage through either an O2(1Δg)‐mediated photoreaction process or a free‐radicals mechanism under low oxygen concentration. These results show that molecular dyads, which can form a photoinduced charge‐separated state, are a promising model for phototherapeutic agents, with potential applications in cell inactivation by PDT.
Confocal Fluorescence Imaging of Photosensitized DNA Denaturation in Cell Nuclei¶
Authors: Bernas Tytus , Asem Elikplimi K. , Robinson J. Paul , Cook Peter R. , Dobrucki Jurek W.
Published: July 2010

The double‐stranded helical structure of DNA is maintained in part by hydrogen bonds between strands and by stacking interactions between adjacent purine and pyrimidine bases in one strand. The transition (denaturation) from a double‐stranded (ds) to a single‐stranded (ss) form can be induced in isolated DNA or fixed cells by exposure to elevated temperatures, alkali or acids, aprotic or nonpolar solvents or some drugs. We report here that DNA denaturation can occur in situ in cell nuclei as a result of interaction between light and an intercalated dye, acridine orange or ethidium bromide. This DNA photodenaturation was probed using metachromatic properties of acridine orange and imaged by fluorescence confocal microscopy. Furthermore, an empirical kinetic model was developed to separate changes of acridine orange luminescence intensities caused by photobleaching from those that were a result of DNA denaturation. We investigated the influence of oxygen on these phenomena and propose a mechanism by which photodenaturation may occur.
Optimization of DNA Extraction from a Scleractinian Coral for the Detection of Thymine Dimers by Immunoassay†
Authors: Banaszak Anastazia T.
Published: July 2010

Ultraviolet (UV)‐B is known to cause DNA damage, principally by the formation of thymine dimers, but little research has been conducted in coral reef environments where UV doses are high. The majority of tropical reef‐dwelling corals form a mutualistic symbiosis with the dinoflagellateSymbiodiniumbut few studies have been conducted onin situDNA damage in corals and none have investigated the symbiotic components separately. The aim of this research was to quantify DNA damage in both the coral host and the dinoflagellate symbiont. The first step in this investigation was to optimize the extraction of DNA from the host,Porites astreoides, as well as the symbiont. The optimization was divided into a series of steps: the preservation of the samples, separation of the coral tissue from the skeleton, separation of the host tissue from the algal cells to prevent cross contamination as well as the extraction and purification of genomic DNA from the algae that are located intracellularly within the invertebrate animal tissue. The best preservation method was freezing at low temperatures without ethanol. After scraping with a razor blade, the coral tissue can be divided into host and algal components and the DNA extracted using modifications of published techniques yielding DNA suitable for the quantification of thymine dimer formation using antibodies. Preliminary data suggest that inP. astreoidescollected from 1 m depth, thymine dimers form approximately 2.8 times more frequently in the host DNA than in the DNA of its symbionts.
Reactions of Cl•/Cl2•− Radicals with the Nanoparticle Silica Surface and with Humic Acids: Model Reactions for the Aqueous Phase Chemistry of the Atmosphere
Authors: Caregnato Paula , Gara Pedro D. , Bosio Gabriela N. , Mártire Daniel O. , Gonzalez Mónica C.
Published: July 2010

Reactions of chlorine radicals might play a role in aqueous aerosols where a core of inorganic components containing insulators such as SiO2 and dissolved HUmic‐LIke Substances (HULIS) are present. Herein, we report conventional flash photolysis experiments performed to investigate the aqueous phase reactions of silica nanoparticles (NP) and humic acid (HA) with chlorine atoms, Cl•, and dichloride radical anions, Cl2•−. Silica NP and HA may be taken as rough models for the inorganic core and HULIS contained in atmospheric particles, respectively. Both Cl• and Cl2•− were observed to react with the deprotonated silanols on the NP surface with reaction rate constants, k ± σ, of (9 ± 6) × 107 M−1 s−1 and (7 ± 4) × 105 M−1 s−1, respectively. The reaction of Cl• with the surface deprotonated silanols leads to the formation of SiO• defects. HA are also observed to react with Cl• and Cl2•− radicals, with reaction rate constants at pH 4 of (3 ± 2) × 1010 M−1 s−1 and (1.2 ± 0.3) × 109 M−1 s−1, respectively. The high values observed for these constants were discussed in terms of the multifunctional heterogeneous mixture of organic molecules conforming HA.
The Effect of Chronic Ultraviolet Radiation on the Human Immune System†
Authors: Norval Mary , McLoone Pauline , Lesiak Aleksandra , Narbutt Joanna
Published: July 2010

A single or a limited number of UVR exposures is recognized to suppress cell‐mediated immunity in human subjects. The complex pathway leading from the absorption of photons by chromophores in the skin to the generation of T regulatory cells has been, at least partially, elucidated. However, the effect of repeated UV exposures on immune responses and associated mediators is not well studied, particularly to assess whether they lead, first, to the development of photoprotection so that these immune changes are reduced or no longer occur, and, secondly, to the development of photoprotection against the normal downregulation of immunity induced by a high UV dose. For almost all the parameters evaluated in this review—epidermal DNA damage/erythema, urocanic acid, Langerhans and dendritic cells, natural killer cells, macrophages, mast cells, contact and delayed hypersensitivity responses—none, aside from epidermal DNA damage/erythema and macrophage phagocytic activity, show convincing evidence of photoadaptation or, where appropriate, photoprotection. It is concluded that repeatedly irradiating individuals with UVR is likely to continue to result in downregulation of immunity.
The D. C. Juvenile Court: Social Agency Or A Court Of Law?
Authors: Bamford Barbara
Published: July 2010

The D C Bar Journal sponsored a legal writing competition at Catholic University Law School. The following is an excerpt from the winning paper reprinted from the March‐April 1968 issue of the D C Bar Journal of the Bar Association of the District of Columbia
Regulation of the
Marinomonas mediterranea
Antimicrobial Protein Lysine Oxidase by
l
-Lysine and the Sensor Histidine Kinase PpoS
Authors: Molina-Quintero Luisa R. , Lucas-Elío Patricia , Sanchez-Amat Antonio
Published: July 2010

Some Gram-negative bacteria express a novel enzyme with lysine-ε-oxidase (LOD) activity (EC 1.4.3.20). The oxidation of
l
-Lys generates, among other products, hydrogen peroxide, which confers antimicrobial properties to this kind of enzyme and has been shown to be involved in cell death during biofilm development and differentiation. In addition to LOD, the melanogenic marine bacterium
Marinomonas mediterranea
, which forms part of the microbiota of the marine plant
Posidonia oceanica
, expresses two other oxidases of biotechnological interest, a multicopper oxidase, PpoA, with laccase activity and a tyrosinase named PpoB, which is responsible for melanin synthesis. By using both
lacZ
fusions with the
lodAB
promoter and quantitative reverse transcription-PCR (qRT-PCR), this study shows that the hybrid sensor histidine kinase PpoS regulates LOD activity at the transcriptional level. Although PpoS also regulates PpoA and PpoB, in this case, the regulatory effect cannot be attributed only to a transcriptional regulation. Further studies indicate that LOD activity is induced at the posttranscriptional level by
l
-Lys as well as by two structurally similar compounds,
l
-Arg and meso-2,6-diaminopimelic acid (DAP), neither of which is a substrate of the enzyme. The inducing effect of these compounds is specific for LOD activity since PpoA and PpoB are not affected by them. This study offers, for the first time, insights into the mechanisms regulating the synthesis of the antimicrobial protein lysine-ε-oxidase in
M. mediterranea
, which could be important in the microbial colonization of the seagrass
P. oceanica
.
Detection of New
cry
Genes of
Bacillus thuringiensis
by Use of a Novel PCR Primer System
Authors: Noguera Pedro A. , Ibarra Jorge E.
Published: July 2010

On the basis of the known
cry
gene sequences of
Bacillus thuringiensis
, three sets of primers were designed from four conserved blocks found in the delta-endotoxin-coding region. The primer pairs designed amplify the regions between blocks 1 and 5, 2 and 5, and 1 and 4.
In silico
analyses indicated that 100% of the known three-domain
cry
gene sequences can be amplified by these sets of primers. To test their ability to amplify known and unknown
cry
gene sequences, 27 strains from the CINVESTAV (LBIT series) collection showing atypical crystal morphology were selected. Their DNA was used as the template with the new primer system, and after a systematic amplification and sequencing of the amplicons, each strain showed one or more
cry
-related sequences, totaling 54 different sequences harbored by the 27 strains. Seven sequences were selected on the basis of their low level of identity to the known
cry
sequences, and once cloning and sequencing of the complete open reading frames were done, three new
cry
-type genes (primary ranks) were identified and the toxins that they encode were designated Cry57Aa1, Cry58Aa1, and Cry59Aa1 by the
B. thuringiensis
Toxin Nomenclature Committee. The rest of the seven sequences were classified Cry8Ka2, Cry8-like, Cry20Ba1, and Cry1Ma1 by the committee. The crystal morphology of the selected strains and analysis of the new Cry protein sequences showed interesting peculiarities.
Quantitative PCR Assay for
Mycobacterium pseudoshottsii
and
Mycobacterium shottsii
and Application to Environmental Samples and Fishes from the Chesapeake Bay
Authors: Gauthier D. T. , Reece K. S. , Xiao J. , Rhodes M. W. , Kator H. I. , Latour R. J. , Bonzek C. F. , Hoenig J. M. , Vogelbein W. K.
Published: July 2010

Striped bass (
Morone saxatilis
) in the Chesapeake Bay are currently experiencing a very high prevalence of mycobacteriosis associated with newly described
Mycobacterium
species,
Mycobacterium pseudoshottsii
and
M. shottsii.
The ecology of these mycobacteria outside the striped bass host is currently unknown. In this work, we developed quantitative real-time PCR assays for
M. pseudoshottsii
and
M. shottsii
and applied these assays to DNA extracts from Chesapeake Bay water and sediment samples, as well as to tissues from two dominant prey of striped bass, Atlantic menhaden (
Brevoortia tyrannus
) and bay anchovy (
Anchoa mitchilli
).
Mycobacterium pseudoshottsii
was found to be ubiquitous in water samples from the main stem of the Chesapeake Bay and was also present in water and sediments from the Rappahannock River, Virginia.
M. pseudoshottsii
was also detected in menhaden and anchovy tissues. In contrast,
M. shottsii
was not detected in water, sediment, or prey fish tissues. In conjunction with its nonpigmented phenotype, which is frequently found in obligately pathogenic mycobacteria of humans, this pattern of occurrence suggests that
M. shottsii
may be an obligate pathogen of striped bass.
Combined Gel Probe and Isotope Labeling Technique for Measuring Dissimilatory Nitrate Reduction to Ammonium in Sediments at Millimeter-Level Resolution
Authors: Stief Peter , Behrendt Anna , Lavik Gaute , De Beer Dirk
Published: July 2010

Dissimilatory NO
3
−
reduction in sediments is often measured in bulk incubations that destroy
in situ
gradients of controlling factors such as sulfide and oxygen. Additionally, the use of unnaturally high NO
3
−
concentrations yields potential rather than actual activities of dissimilatory NO
3
−
reduction. We developed a technique to determine the vertical distribution of the net rates of dissimilatory nitrate reduction to ammonium (DNRA) with minimal physical disturbance in intact sediment cores at millimeter-level resolution. This allows DNRA activity to be directly linked to the microenvironmental conditions in the layer of NO
3
−
consumption. The water column of the sediment core is amended with
15
NO
3
−
at the
in situ
14
NO
3
−
concentration. A gel probe is deployed in the sediment and is retrieved after complete diffusive equilibration between the gel and the sediment pore water. The gel is then sliced and the NH
4
+
dissolved in the gel slices is chemically converted by hypobromite to N
2
in reaction vials. The isotopic composition of N
2
is determined by mass spectrometry. We used the combined gel probe and isotopic labeling technique with freshwater and marine sediment cores and with sterile quartz sand with artificial gradients of
15
NH
4
+
. The results were compared to the NH
4
+
microsensor profiles measured in freshwater sediment and quartz sand and to the N
2
O microsensor profiles measured in acetylene-amended sediments to trace denitrification.