bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a Test System for Mutagenicity of Photosensitizers Using Drosophila melanogaster¶
Authors: Smijs Threes G. M. , Nivard Madeleine J. M. , Schuitmaker Hans J. 
Published: July 2010

ABSTRACTIn the past few years, there has been an increase in the application of photosensitizers for medical purposes. A good standardized test system for the evaluation of the mutagenic potentials of photosensitizers is therefore an indispensable device. In the standard Ames test, white light itself was proven to be mutagenic and the result influenced by the light source. Lack of a reliable positive control is another problem in many genotoxicity test systems used for the evaluation of mutagenicity of photosensitizers. Based on the validated somatic mutation and recombination test, known as SMART, and using Drosophila melanogaster, we developed the Photo‐SMART and demonstrated that methylene blue, known to induce photomutagenicity, can act as a positive control in the presented test system. The SMART scores for the loss of heterozygosity caused predominantly by homologous mitotic recombination. The Photo‐SMART can be used to detect photogenotoxicity caused by short‐lived photoproducts or by stable photoproducts or both. We demonstrated the Photo‐SMART to be a good standardized test system for the evaluation of mutagenic potentials of the photosensitizer 5,10,15‐tris(4‐methylpyridinium)‐20‐phenyl‐[21H,23H]‐porphine trichloride (TPP). We demonstrated that TPP was mutagenic using the Photo‐SMART. For hematoporphyrin, the results of the Photo‐SMART indicate the absence of mutagenicity.
Survival and Recovery of Yeast Cells After Simultaneous Treatment of UV Light Radiation and Heat¶
Authors: Kim Jin Kyu , Petin Vladislav G. , Tkhabisimova Marianna D. 
Published: July 2010

ABSTRACTCell survival, synergistic interaction, liquid‐holding recovery (LHR) kinetics and inactivation forms after the simultaneous treatment with UV light (254 nm) and various high temperatures were studied in diploid yeast cells Saccharomyces cerevisiae. The synergistic interaction was observed within a certain temperature range in which there was a temperature that maximizes the synergistic effect. The LHR study revealed that both the extent and the rate of recovery greatly decreased with the increase in exposure temperature. A quantitative approach describing the LHR process as a decrease in the effective radiation dose was used to estimate the probability of recovery per unit time and the irreversible component of damage. Using the experimental data obtained and the mathematical model described, it was shwon that the irreversible component, i.e. the fraction of cells incapable of recovery, increased with the exposure temperature, whereas the recovery constant, i.e. the probability of recovery per unit time, was independent of the exposure temperature. The increase in the irreversible component was accompanied by an increase in cell death without postirradiation division. It is concluded based on this that the synergistic interaction of UV light radiation and hyperthermia in yeast cells is not related to the impairment of the recovery process itself and that it may be attributed to an increased yield of the irreversible damage.
Personal solar UV Exposure Measurements Employing Modified Polysulphone with an Extended Dynamic Range†¶
Authors: Parisi Alfio V. , Kimlin Michael G. 
Published: July 2010

ABSTRACTPolysulphone dosimeters using a simple to use filter have been developed and tested to provide an extended dynamic measurement range of personal solar W exposures over an extended period (3 to 6 days). At a Southern Hemisphere subtropical site (27.6°S, 151.9°E), the dynamic range of the filtered polysulphone allowed measurements of erythemal exposures to approximately 100 minimum erythemal dose (MED) for a change in optical absorbance at 330 nm (AA330) of 0.35. In comparison, unfiltered polysulphone dosimeters were exposed to approximately 8 MED for the same AA330. The error associated with the use of the filtered polysulphone dosimeters is of the order of ±15%, compared with ±10% of the unfiltered variety. The developed filtered polysulphone dosimeter system allowed the measurement of erythemal UV exposures over 3 to 6 days at a subtropical site without the need to replace the dosimeters because of saturation. The results show that longer‐term measurement programs of personal solar UV have been made more feasible with the use of these polysulphone dosimeters with an extended dynamic range compared with unfiltered polysulphone dosimeters.
Kinetics and Mechanism of the Vitamin B2‐sensitized Photooxidation of Isoproterenol¶
Authors: Massad Walter A. , Bertolotti Sonia , Garcia Norman A. 
Published: July 2010

ABSTRACTThe sensitized photooxidation promoted by daylight‐absorbing compounds appears as a plausible course to produce the photodegradation of catecholamines. We report the kinetics and mechanism of vitamin B2 (reiboflavin [Rf])‐sensitized photooxidation of isoproterenol (Isoproterenol (Iso), a synthetic sympathomimetic drug structurally related to epinephrine, using water as a solvent. A week dark complex Rf‐Iso is formed, only detectable at relatively high Iso concentrations (>10 mM), with a mean value of 13 ± 3 M−1 for the apparent association constant. Under aerobic sensitizing conditions (Rf ∼ 0.02 mM and Iso ∼ 0.5 mM) two oxidative mechanisms operate, mediated by singlet molecular oxygen (O2(Δg)) and superoxide radical anion (O2•−). Our analysis shows that the main reaction pathway is an electron transfer‐mediated quaenching of Rf excited triplet state (3Rf*) by Iso. It produces the species Iso•+ and Rf•−. The latter, in a subsequent reaction path, generates O2•−, which is mainly responsible for Iso Photooxygenation. In a less‐important process, energy transfer of the 3Rf* to dissolved oxygen generates O2(Δg). The kinetic balance between chemical and physical quenching of O2(1Δg) by Iso indicates that the process is largely dominated by the physical, not chemical, interaction. The results, which can be extrapolated to an in vivo condition, show the susceptibility of Iso to undergo visible light‐induced photodegradation in the presence of dye sensitizers present in the environment.
Flexibility in Proteins: Tuning the Sensitivity to O2 Diffusion by Varying the Lifetime of a Phosphorescent Sensor in Horseradish Peroxidase¶
Authors: Nibbs Janna , Vinogradov Sergei A. , Vanderkool Jane M. , Zelent Bogumil 
Published: July 2010

ABSTRACTThe heme in horseradish peroxidase (HRP) was replaced by phosphorescent Pt‐mesoporphyrin IX (PtMP), which acted as a phosphorescent marker of oxygen quenching and allowed comparison with another probe, Pd‐mesoporphyrin IX (Khajehpour et al. (2003) Proteins 53, 656–666). Benzohydroxamic acid (BHA), a competitive inhibitor of the enzyme, was also used to monitor its effects on phosphorescence quenching. With the addition of BHA, in the presence of oxygen, the phosphorescence intensity of the protein increased. In contrast, the addition of BHA, in the absence of oxygen, reduced the phosphorescence intensity of the protein. Kd= 18 μM when BHA binds to PtMP‐HRP. The effect of BHA can be explained by two factors: (1) BHA reduces the accessibility of O2 to the protein interior and (2) BHA itself quenches the phosphorescence. Consistent with this, the oxygen quenching of the phosphorescence of PtMP‐HRP gave a quenching constant of kq= 234 mm Hg−1 s−1 in the absence of BHA and kq= 28.7 mm Hg−1 s−1 in the presence of BHA. The quenching rate of BHA is 4000 s−1. The relative quantum yield of the phosphorescence of the Pt derivative is about six times that of the Pd derivative, whereas the phosphorescence lifetime is approximately eight times shorter. The high quantum yield and suitable lifetime make Pt‐porphyrins appropriate as sensors of O2 diffusion and flexibility in heme proteins.
Virus Particles Monitored by Fluorescence Spectroscopy: A Potential Detection Assay for Macromolecular Assembly¶
Authors: Alimova Alexandra , Katz A. , Podder Rakhi , Minko Glenn , Wei Hul , Alfano R. R. , Gottlieb Paul 
Published: July 2010

ABSTRACTNative fluorescence spectroscopy was used for in situ investigations of two lipid‐containing bacteriophages from the cystovirus family as well as their Pseudomonad host cells. Both the viruses φ6 and φ12 and their bacterial host proteins contain the amino acid tryptophan (trp), which is the predominant fluorophore in UV. Within proteins, trp's structural environment differs, and the differences are reflected in their spectroscopic signatures. It was observed that the peak of the trp emission from both viruses was at 330 nm, a significantly shorter wavelength than trp in either the Pseudomonad host cells or the amino acid's chemical form. This allowed us to monitor the viral attachment process and subsequent lytic release of progeny virus particles by measurement of the trp emission spectra during the infection process. This work demonstrates that fluorescence may offer a novel tool to detect viruses and monitor viral infection of cells and may be part of a biodefense application.
Dermatological Risk of Indoor Ultraviolet Exposure from Contemporary Lighting Sources¶†‡§
Authors: Sayre Robert M. , Dowdy John C. , Poh‐Fitzpatrick Maureen 
Published: July 2010

ABSTRACTDiscussions of risks and implications of cutaneous exposure to indoor lighting, including hypothetical contribution to causality of melanoma, have mainly concentrated on ultraviolet (UV) A and B (UVA, UVB) spectral emissions from fluorescent bulbs. Only studies of quartz halogen lamps have suggested that users might sustain UVC‐induced injury. Examination of light sources in the home and school of a child with xeroderma pigmentosum revealed that several different types emitted surprising levels of UV. Our purpose was to assess the extent of UV emissions from a variety of commonly used light sources to identify potential dermatological risks. UV and visible spectral emissions of commercially obtained lamps of several types were measured using a calibrated spectral radiometer traceable to the National Institute of Standards and Technology. Indoor light sources including fluorescent, quartz halogen and even tungsten filament incandescent lamps provided UVA, UVB and sometimes UVC emissions. Intensities of some emissions were of similar magnitude to those in sunlight. Chronic exposure to indoor lighting may deliver unexpected cumulative UV exposure to the skin and eyes. Patients with UV‐exacerbated dermatoses should be cautioned about potential adverse reactions from indoor lighting.
Suppression of Different Phases of Systemic Contact Hypersensitivity by Urocanic Acid Oxidation Productsfn1
Authors: Kammeyer Arthur , Garssen Johan , Sleijffers Annemarie , van Loveren Henk , Eggelte Teunis A. , Bos Jan D. , Teunissen Marcel B. M. 
Published: July 2010

ABSTRACTOn exposure to UV‐B, the epidermal component trans‐urocanic acid (UCA) is not only photoisomerized into cis‐ UCA but will also, at least in part, be photooxidized into UCA oxidation products (UOPs). We hypothesized that UOPs can mimic UV‐induced systemic immunosuppression comparable to the suppressive properties already established for cis‐UCA. A crude mixture of UOPs showed a significant suppression of the sensitization phase of the systemic contact hypersensitivity (CHS) response to picryl chloride (PCI). Three of the UOPs were selected for this study: imidazole‐4‐carboxylic acid (ImCOOH), immidazole‐4‐carboxaldehyde (ImCHO) and imidazole‐4‐acetic acid (ImAc). Effects on the sensitization, elicitation and postelicitation phases of CHS to PCI in BALB/c mice were studied and compared with the effects of cis‐UCA. ImCHO was equally effective at suppressing the sensitization phase as cis‐UCA. The triplet combination of the imidazoles (1:1:1) showed more pronounced suppression than that induced by cis‐UCA. The most effective compounds for the suppression of the elicitation phase appeared to be ImAc and cis‐UCA. Significant suppression of the postelicitation phase was only obtained with the triplet combination of ImCHO, ImCOOH and ImAc, the combination that appeared to be effective at all three tested phases. Because these three UOPs are present in UV‐B‐exposed human stratum corvneum, these compounds may play a role in UV‐B‐induced immunosuppression.
Effects of UV‐B Irradiation on a Marine Microecosystem¶
Authors: Marangoni Roberto , Messina Nicola , Gioffré Domenico , Colombetti Giuliano 
Published: July 2010

ABSTRACTPurpose of this work was to study the effect of UV irradiation on a microecosystem consisting of several interacting species. The system chosen was of a hypersaline type, where all the species present live at high salt concentration; it comprises different bacteria; a producer, the photosynthetic green alga Dunaliella salina; and a consumer, the ciliated protozoan Fabrea salina, which form a complete food chain. We were able to establish the initial conditions that give rise to a selfsustaining microecosystem, stable for at least 3 weeks. We then determined the effect of UV irradiation on this microecosystem under laboratory‐controlled conditions, in particular by measuring the critical UV exposure for the two main components of the microecosystem (algae and protozoa) under UV‐B irradiances comparable to those of solar irradiation. In our experiments, we varied irradiance, total dose and spectral composition of the actinic light. The critical doses at irradiances of the order of 56 kJ/m2 (typical average daily irradiance in a sunny summer day in Pisa), measured for each main component of the microecosystem (algae and ciliates), turned out to be around 70 kJ/m2 for ciliates and 50 kJ/m2 for D. salina. By exposing microecosystems to daily UV‐B irradiances of the order of 8 kJ/m2 (typical average daily irradiance in a sunny winter day in Pisa), we found no effect at total doses of the order of the critical doses at high irradiances, showing that the reciprocity law does not hold. We have also measured a preliminary spectral‐sensitive curve of the UV effects, which shows an exponential decay with wavelength.
Characterization of the Fe(III)‐binding Site in Sepia Eumelanin by Resonance Raman Confocal Microspectroscopy¶
Authors: Samokhvalov Alexander , Liu Yan , Simon John D. 
Published: July 2010

ABSTRACTThe resonance Raman spectrum of Sepia eumelanin is discussed by analogy to model compounds containing catechol (CAT)‐like structural units. These data are then compared with the analogous data on Fe(III)‐enriched Sepia eumelanin. In contrast to the natural eumelanin, the Fe(III)‐enriched samples exhibit absorption features in the visible and near‐IR spectral regions, which are attributed to ligand‐to‐metal charge‐transfer (LMCT) bands. Resonance Raman spectra collected by exciting these LMCT bands reveal bands at 580 and 1470 cm−1; the intensity of these features increases wioth increasing Fe(III) content. The 580 and 1470 cm−1 bands are assigned to Fe‐OR stretching and ring deformation modes, respectively. These data further substantiate that the Fe(III)‐ melanin‐binding site in melanin is composed of CAT‐like structural units.
Photophysical Properties of Coumarin‐30 Dye in Aprotic and Protic Solvents of Varying Polarities¶
Authors: Senthilkumar Sadasivam , Nath Sukhendu , Pal Haridas 
Published: July 2010

ABSTRACTExperimental results on various photophysical properties of coumarin‐30 (C30) dye, namely, Stokes' shift (Δv), fluorescence quantum yield (τf), fluorescence lifetime (τf), radiative rate constant (kf) and nonradiative rate constant (knr), as obtained using absorption and fluorescence measurements have been reported. Though in most of the solvents the properties of C30 show more or less linear correlation with the solvent polarity function, Δf= [(ε ‐ 1)/(2ε+ 1) ‐ (n2 ‐ 1)/ (2n2+ l)], they show unusual deviations in nonpolar solvents at one end and in high‐polarity protic solvents at the other end. From the solvent polarity and temperature effect on the photophysical properties of the dye, following inferences have been drawn: (1) in nonpolar solvents, the dye exists in a nonpolar structure, where its 7‐NEt2 substituent adopts a pyramidal configuration and the amino lone pair is out of resonance with the benzopyrone π cloud; (2) in medium to higher polarity solvents, the dye exists in a polar intra‐molecular charge transfer structure, where the 7‐NEt2 group and the 1,2‐benzopyrone moiety are in the same plane and the amino lone pair is in resonance with the benzopyrone π cloud; (3) in protic solvents, the dye‐solvent intermolecular hydrogen bonding influences the photophysical properties of the dye; and (4) in high‐polarity protic solvents, the excited C30 undergoes a new activation‐controlled nonradiative deexcitation process because of the involvement of a twisted intra‐molecular charge transfer (TICT) state. Contrary to most other TICT molecules, the activation barrier for this deexcitation process in C30 is observed to increase with solvent polarity. A rational for this unusual behavior has been given on the basis of the solvent polarity‐dependent stabilization and crossing of relevant electronic states and the relative propensity of interconversion among these states.
The Fluorescence Properties of Hypocrellin B and its Amino‐substituted Derivative: Photinduced Intramolecular Proton Transfer and Photoinduced Intramolecular Electron Transfer¶
Authors: Xu Shangjie , Zhang Xiaoxing , Chen Shen , Zhang Manhua , Shen Tao 
Published: July 2010

ABSTRACTWe report on the emission spectra and emission quantum yields of a newly synthesized hypocrellin dye, Z‐demethoxy‐ 2,3‐ethylenediamino hypocrellin B (EDAHB), and its parent HB in different solvents of varying polarity. Our results demonstrate that EDAHB is one of the few dyes that exhibit highly solvent polarity‐dependent fluorescence in the useful region (680–730 nm). Therefore, it offers some applications in the biomedical field as a fluorescent probe molecule. The solvatochromic effect of EDAHB is proposed to be due to a distinct change in the dipole moment of the dye on excitation. A photoinduced intramolecular proton transfer and a photoinduced intramolecular electron transfer process are considered relevant for the fluorescence properties of HB and EDAHB, respectively.
Light Modulates Electric Phenomena in Hornet Cuticle¶
Authors: Ishay Jacob S. , Sverdlov Anna , Pertsis Vitaly , Gavrilov Yulla , Steinberg David 
Published: July 2010

ABSTRACTIn the cuticle of live social hornets, such as Vespa orientalis (Hymenoptera, Vespinae), endogenous electric effects are encountered, i.e. voltages of 100–200 mV under illumination and currents amounting to several microamperes on its subjection to darkness—clearly a process of charging and discharging. Of the various wavelengths of sunlight, UV was found to be the most contributory to the active cuticular voltage generation. Throughout the warm season of the yearthe–the active period in colonies of social hornets and wasps—colony members exit from the dark nest during the daytime and fly to the field under the hot sun for various foraging purposes, ultimately returning to the nest. Thus, each hornet, be it queen, worker or drone, probably undergoes daily cyclical process of electric charge and discharge in the exterior part of their integument, cuticle, which lasts up to 30–40 min. Such photoelectric phenomenon was detected in both live, ether‐anaesthetized hornets and dead hornets, albeit in the latter the electric values recorded were lower. The present study addresses the possible impact of the phenomenon on vespan daily life and also compares it with a parallel occurrence in electric fish.
Energy Dissipation Processes of singlet‐excited 1‐Hydroxyfluorenone and its Hydrogen‐bonded Complex with N‐methylimidazole¶
Authors: Sebök‐Nagy Krisztina , Biczók László , Morimoto Akimitsu , Shimada Tetsuya , Inoue Haruo 
Published: July 2010

ABSTRACTEffects of solvent, pH and hydrogen bonding with N‐methylimidazole (MIm) on the photophysical properties of 1‐hydroxyfluorenone (1HOF) have been studied. Fluorescence lifetime, fluorescence quantum yield and triplet yield measurements demonstrated that intersystem crossing was the dominant process in apolar media and its rate constant significantly diminished with increasing solvent polarity. The acceleration of internal conversion in alcohols paralleled the strength of intermolecular hydrogen bonding. The faster energy dissipation from the singlet‐excited state in cyclohexane was attributed to intramolecular hydrogen bonding. The pKa of 1HOF decreased from 10.06 to 5.0 on light absorption, and H3O+ quenched the singletexcited molecules in a practically diffusion‐controlled reaction. On addition of MIm in toluene, dual fluorescence was observed, which was attributed to reversible formation of excited hydrogen‐bonded ion pair. Rate constants for the various deactivation pathways were derived from the combined analysis of the steady‐state and the time‐resolved fluorescence results.
The Effects of the Substitution on the lmidazole Ligand on the Photochemical Properties of fac[Mn(CO)3(phen)(lmidazole)](SO3CF3) Complexes¶
Authors: Carlos Rose Maria , Neto Benedito S. Lima , Neumann Miguel G. 
Published: July 2010

ABSTRACTPhotochemical and photophysical data are reported for a series of fac‐[Mn(CO)3(phen)(Im‐R)](SO3CF3) complexes, where phen is 1,10‐phenanthroline and Im is imidazole. Intraligand and metal‐to‐ligand charge transfer (MLCT) transitions are observed in the electronic absorption spectra of these complexes and are sensitive to the nature of the ligand substituent. At room temperature the emission spectra show a clear progression from broad structureless MLCT to highly structured π‐π* emission on going from R = ‐H, ‐CH3, ‐C6H5, to ‐Metro, where Metro is 2‐methyl‐5‐nitroimidazole. Even at low temperatures the latter complexes show only the π‐π* emission. The trend in the photophysical properties found in the emission spectra parallels the changes in the photochemical properties with the electron‐donating or electron‐withdrawing power of the substituent on the imidazole ligand. Although MLCT irradiation of the complexes with R = ‐H, ‐CH3 leads to the mer‐[Mn(CO)3(phen)(Im‐R)]+ isomers, the complexes with the imidazole ligand substituted by ‐C6H5 or ‐Metro release the Im‐R ligand and produce the stereoretentive fac‐[Mn(CO)3(phen)(S)]+ complexes. The stereochemical fate and mechanistic implications of the photolysis reactions are discussed in terms of the nature of ligand substitution.
Isolation and Characterization of a Novel Cross‐link Lesion in d(CpC) Induced by One‐electron Photooxidation¶
Authors: Liu Zhenjiu , Gao Yuan , Zeng Yu , Fang Fang , Chi Dahn , Wang Yinsheng 
Published: July 2010

ABSTRACTRecently we reported the identification and characterization of a novel cross‐link lesion formed between two adjacent cytosines in d(CpC), which is the major product formed upon 365 nm photoirradiation of d(CpC) in the presence of 2‐methyl‐1,4‐naphthoquinone. In this study we discuss the isolation and structure characterization of another cross‐link lesion formed under the same irradiation condition. Electrospray ionization mass spectroscopy, tandem mass spectrometry and two‐dimensional nuclear Overhauser effect spectroscopy results demonstrate that the C6 carbon atom of the 5’cytosine and the N3 nitrogen atom of the 3’cytosine are covalently bonded. In addition, the 5’cytosine moiety deaminated and the C5 carbon atom in this cytosine is oxidized to a carbonyl group.