bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photodynamic Action: From Paramecium to Photochemotherapy*
Authors: Spikes John D. 
Published: January 2008

SUMMARYIt has been a most interesting and often exciting experience to have been involved in the study of photodynamic reactions during this period of rapid expansion of research and the development of so many promising applications of photosensitized reactions to biomedical problems. As indicated above, the present level of activity is overwhelming at times. I should probably not admit it, but occasionally, after going through masses of new literature, I become a bit nostalgic, and reminisce a little on the earlier days when the study of photodynamic reactions was a quiet, noncompetitive, relaxing and gentlemanly pursuit.
Investigations of the Enhancer Effect of a High‐Salt Concentration Medium on the Luminol Chemiluminescent Reaction
Authors: Collaudin Agnès Berger , Blum Loïc J. 
Published: January 2008

AbstractThe enhancer effect of a high‐salt concentration medium on the luminol chemiluminescence reaction catalyzed by either soluble or immobilized peroxidase has been investigated. Some widely used salts were tested at high concentration (up to 3 mol L): potassium chloride, sodium chloride, ammonium sulfate and calcium chloride. The magnitude of the light intensity enhancement depends on the nature of the salt and on the form of the peroxidase, i.e. free in solution or immobilized. The enhancement is observed whether the catalyst of the chemiluminescence reaction is peroxidase or ferricyanide. Both the enhanced or nonenhanced luminol chemiluminescence spectra have a maximum wavelength emission at around 425 nm. The results reported in this study are in favor of an action of the salts on the nonenzymatic steps of the luminol chemiluminescence reaction rather than a modification of the enzymatic process.
Photobiological Properties of Methylene Violet*
Authors: Morrison Harry , Mohammad Taj , Kurukulasuriya Ravi 
Published: January 2008

AbstractThe interaction of methylene violet (MV) and 4‐bromo‐methylene violet (BrMV) with calf thymus and super‐coiled φX174 phage RF I DNA is reported. Measurements employing UV‐visible absorption spectroscopy and equilibrium dialysis give evidence for the formation of complexes by each dye with DNA in the dark. They covalently bind to DNA, and MV nicks DNA, when the nucleic acid/dye mixtures are irradiated with visible light in a deoxygenated environment. Quantum efficiencies for singlet oxygen formation are 0.27 and 0.25 for MV and BrMV, respectively. A higher value (0.49) is observed for 4‐iodomethyIene violet (IMV).SummaryThe MV and BrMV interact with DNA in the dark to form complexes that are observable by absorption and emission spectroscopy and by equilibrium dialysis. When mixtures of the dyes and DNA are irradiated with visible light, both incorporation of the dye into the nucleic acid and nicking of the DNA are observed. These dyes generate singlet oxygen with quantum yields ranging from 0.25 for MV to 0.49 for IMV.
Blue Light‐induced Acidification of the Medium and the Uptake of Nitrate in a Nitrate‐starved Chlorella
Authors: Kamiya Akio 
Published: January 2008

AbstractWhen cells of nitrate‐starved Chlorella kessleri (Fott et Novakova, no. 211‐11h) were suspended in phosphate buffer containing nitrate, they could barely take up nitrate in the dark. The addition of glucose resulted in the initiation of nitrate uptake by Chlorella. Irradiation with blue light stimulated the uptake of nitrate about two‐fold as compared with those of glucose‐treated cells and the acidification of the suspension medium, which, after 60‐90 min of blue irradiation, turned to alkalinization. These effects of blue light on the uptake of nitrate and pH changes were also observed in nitrate‐starved colorless (Fott et Novakova, no. 9.80) and yellow (Fott et Novakova, no. 211‐11h/20) mutants of C. kessleri. Staurosporine and K252a, potent inhibitors of protein kinase C, inhibited the blue light‐induced acidification of the medium and nitrate uptake. The data are discussed with regard to transduction of the signal for blue light‐induced acidification and nitrate uptake.
Kinetics and Yield of Singlet Oxygen Photosensitized by Hypericin in Organic and Biological Media
Authors: Ehrenberg Benjamin , Anderson Jamey L. , Foote Christopher S. 
Published: January 2008

AbstractThe spectroscopy and photophysics of the photosensitizer hypericin when in homogeneous solutions and when bound to liposomes were studied. Hypericin was found to partition efficiently into DMPC liposomes, with a binding constant of 58 (mg lipid/mL)−1. In these liposomes the singlet oxygen production quantum yield was 0.43 ± 0.09. To determine the deactivation constant of singlet oxygen in lipid bilayers for the first time, we calculated extrapolated values from its quenching by DMPC and lecithin in homogeneous solutions and obtained decay times of 36.4 and 12.2 μs, respectively. We also measured the quenching of singlet oxygen, sensitized by hypericin in DMPC liposomes, by NaN3, diphenyl isobenzofuran and H2,O: D2O mixtures and explained the results on the basis of singlet oxygen diffusing rapidly out of the lipid bilayer into the aqueous medium. The observed temperature effect on the lifetime of singlet oxygen of about 50% over a 15°C range in liposome suspension contrasts with a 3% change in a homogeneous solution in 1‐nonanol and is explained by the temperature effect on the diffusion out of the liposome. A strong pH effect was observed, indicating that the deprotonated species formed above about pH 10 is a much weaker photosensitizer of singlet oxygen than the native, protonated species.
Preferential Relative Porphyrin Enrichment in Solar Keratoses upon Topical Application of ^‐Aminolevulinic Acid Methylester
Authors: Fritsch Clemens , Homey Bernhard , Stahl Wilhelm , Lehmann Percy , Ruzicka Thomas , Sies Helmut 
Published: January 2008

AbstractTopically applied δ‐aminolevulinic acid is used efficiently for the treatment of solar keratoses by photodynamic therapy. Recent animal studies suggest that porphyrin sensitization of epithelial tissue is improved by using esters rather than free δ‐aminolevulinic acid. The present study examines porphyrin metabolite formation after topical application of δ‐aminolevulinic acid or δ‐aminolevulinic acid methylester in human solar keratoses versus adjacent normal skin. Levels of total porphyrins, porphyrin metabolites and protein were measured in skin samples excised after 1 and 6 h. Higher levels of porphyrins were observed in solar keratoses than in normal skin with both substances. Maximum porphyrin levels were present in solar keratoses treated with δ‐aminolevulinic acid for 6 h. However, the ratio of porphyrins in solar keratoses versus adjacent normal skin was higher with 8‐aminolevulinic acid methylester. The pattern of porphyrins showed no significant difference between normal and afflicted skin, protoporphyrin being predominant. The results suggest that application of free δ‐aminolevulinic acid may be more effective in sensitizing solar keratoses. However, treatment with 8‐aminolevulinic acid methylester leads to a preferential enrichment of porphyrins within lesional skin.
Photoinduced Charge Separation in Reverse Micelles Prepared with Benzylhexadecyldimethylammonium Chloride (BHDC). The Electron‐Transfer Reaction between Pyrene and N,N‐Dimethylaniline*
Authors: Borsarelli Claudio D. , Cosa Juan J. , Previtali Carlos M. 
Published: January 2008

AbstractLaser flash photolysis was used to investigate the formation of radical ions produced in the quenching of the pyrene‐N,N'‐dimethylaniline exciplex by reverse micelles made with benzylhexadecyldimethylammonium chloride (BHDC) dispersed in benzene or chlorobenzene. The radical ion quantum yields, φion, were determined as a function of BHDC concentration and the amount of water dispersed. They were strongly dependent on the composition of the media. The charge separation was more effective in the BHDC‐benzene than in the BHDC‐chlorobenzene system. The results are discussed in terms of the properties of the micellar interface and the fast exchange of material produced by collisions between reverse micelles.
4‐Terf‐Butylperoxymethyl‐9‐Methoxypsoralen as Intercalating Photochemical Alkoxyl‐Radical Source for Oxidative DNA Damage
Authors: Adam Waldemar , Arnold Markus A. , Grimm Günther N. , Saha‐Mölter Chantu R. , Dall'Acqua Francesco , Miolo Gorgia , Vedaldi Daniela 
Published: January 2008

AbstractWe describe the synthesis of a novel psoralen peroxide 1 that generates on irradiation (350 nml alkoxyl radicals, namely tert‐butoxyl radicals, as confirmed by electron spin resonance studies with the spin trap 5,5‐dimethyl‐pyrroline‐N‐oxide. The radical source intercalates into the DNA, which has been demonstrated by linear‐flow‐dichroism measurements. Thus, the alkoxyl radicals are formed advantageously directly in the DNA matrix. In supercoiled pBR322 DNA, the generation of strand breaks by the photochemically or metal‐catalyzed generated alkoxyl radicals is demonstrated. Photosensitization by the psoralen chromophore was excluded because similar substances that do not release radicals caused no DNA damage, nor were the photoproducts of the peroxide 1 active. With calf thymus DNA, 8‐oxoGua and small amounts of guanidine‐releasing products, e.g. oxazolone, were observed. However, in these reactions the photoproduct also displayed some DNA‐oxidizing capacity.
Comparison of the Time‐resolved Absorption and Phosphorescence from the Tryptophan Triplet State in Proteins in Solution
Authors: Gershenson Anne , Gafni Ari , Steel Duncan 
Published: January 2008

ABSTRACTMeasurement of the room temperature Trp triplet state lifetime in proteins by time‐resolved phosphorescence can provide valuable information on the structure and dynamics of proteins in solution. Our time‐resolved absorption measurements on the long‐lived states resulting from electronic excitation of the chromophore demonstrate the presence of more complex behavior than revealed by time‐resolved phosphorescence. To provide additional insight into this behavior, a comparative study of time‐resolved transient absorption and time‐resolved phosphorescence of proteins in solution was carried out. The results show that the time evolution of the long‐lived states observed through transient absorption often differs considerably from that observed in time‐resolved phosphorescence. In some proteins, the presence of competing reactions complicates the interpretation of the transient absorption measurements (which may affect the phosphorescence yield). A more complete characterization of these processes will likely prove useful in the study of protein structure and dynamics in solution.
Flavodoxin as an Electronic Donor in Photosynthetic Inorganic Nitrogen Assimilation by Iron‐deficient Chlorella fusca Cells
Authors: Vigara A. Javier , Inda Luis A. , Vega José M. , Gómez‐Moreno Carlos , Peleato M. Luisa 
Published: January 2008

ABSTRACTTwo ferredoxin‐dependent enzymes involved in the photosynthetic assimilation of nitrogen, nitrite reductase (EC 1.7.7.1) and glutamate synthase (EC 1.4.7.1) from Chlorella fusca have been shown to use either ferredoxin or flavodoxin (from the same organism) as electron donor. Nitrite reductase showed Km, values of 13.8 ± 0.9 μM for ferredoxin and 30.4 ± 7.8 μM for flavodoxin. Glutamate synthase exhibited a Km of 6.6 ± 1.2 μM for ferredoxin compared to a calculated Km of 22.4 ± 6.4 μM for flavodoxin.
PUVA‐Induced Cell Mortality in NCTC 2544 Keratinocytes: Is It Related to the Microenvironmental Properties of the Excited States of Psoralens?
Authors: Sousa Cristina , Melo Teresa Sá e , Mazière Jean‐Claude , Santus René 
Published: January 2008

ABSTRACTThe phototoxic effect of psoralen (PSO), 5‐methoxypsoralen (5MOP), 8‐methoxypsoralen (8MOP) and 4,5′,8‐trimethylpsoralen (TMP) has been compared on the NCTC 2544 keratinocyte cell line in terms of cell mortality and lipid peroxidation. The order of effectiveness for cell photokilling is TMP, 5MOP >> 8MOP, PSO, whereas a little lipid peroxidation is observed for the four psoralens under study. Oxygen‐independent membrane damage seem to play a key role in the lethal photodamage because the biological effectiveness of the most hydrophobic lipid‐soluble psoralens, TMP and 5MOP, is about an order of magnitude higher than that of the more water‐soluble 8MOP and PSO. In relation to this hypothesis, and in contrast to 8MOP, TMP is readily extracted from cells by ethyl acetate, a good membrane solvent, as shown by GC/MS analysis on cell extracts. The results are discussed in terms of the highly microenvironment‐dependent photophysical properties of psoralens. By the measure of the intracellular psoralen concentration, the neutral red uptake and the lipid peroxidation products, this work provides evidence that PUVA therapy‐mediated cell mortality is a lipid peroxidation‐independent phenomenon.
A Resin‐bound Photosensitizer for Aqueous Photooxidations
Authors: Prat Ferran , Foote Christopher S. 
Published: January 2008

ABSTRACTA new resin‐bound photosensitizer for aqueous photooxidations has been prepared. This product allows the sensitizer to be easily removed from the solution by a simple filtration. Its efficiency has been tested with two different substrates.
Protection Against UV‐Induced Reactive Intermediates in Human Cells and Mouse Skin by Glutathione Precursors: A Comparison of N‐Acetylcysteine and Glutathione Ethylester
Authors: Steenvoorden David P. T. , Hasselbaink Danny M. , van Henegouwen Gerard M. J. Beijersbergen 
Published: January 2008

ABSTRACTBecause glutathione (GSH) plays a central part in the endogenous defense against UV radiation, an increase in GSH might provide photoprotection. Two agents that increase GSH levels were investigated. Cultured human cells and mouse skin were treated with N‐acetylcysteine (NAC) and glutathione ethylester (GSH‐Et). After 30 min, the GSH level was determined by HPLC. Photoprotection was assessed by testing the ability of the thiols to scavenge UV‐induced reactive intermediates in the same models. As compared to control cells, NAC and GSH‐Et increased intracellular GSH in vitro to maximally 144% and 174% respectively. In vitro protection (maximum 23% for NAC and 21% for GSH‐Et) did not correlate to the intracellular GSH level but to the concentration of the thiols in the medium. Invivo, epidermal GSH was increased to maximally 163% of the control level by NAC and 1234% by GSH‐Et. The maximum in vivo photoprotection provided by GSH‐Et was 55%, similar to what was found previously for NAC. Again, the protection seemed more closely correlated to the thiol dose than to the GSH level. The study showed that the protection against UV‐induced reactive intermediates depends on a general antioxidant action of these thiols, rather than only on their role as GSH precursors.
Effect of Self‐association and Protein Binding on the Photochemical Reactivity of Triarylmethanes. Implications of Noncovalent Interactions on the Competition between Photosensitization Mechanisms Type I and Type II
Authors: Bartlett Jeremy A. , Indig Guilherme L. 
Published: January 2008

AbstractWe have explored the photochemical behavior of cationic triarylmethane dye monomers and dimers free in solution and noncovalently bound to bovine serum albumin (BSA) and examined how self‐association and the formation of host‐guest complexes involving biopolymers and photosensitizers affect the competition between the photosensitization type I and type II mechanisms. Our results have clearly indicated that tri‐para ‐substituted triarylmethane dyes bind efficiently to albumin as monomers and dimers and, interestingly, that the formation of dye aggregates in aqueous solutions is actually assisted by the protein. Protein‐assisted dye aggregation takes place under conditions of high biopolymer loading (high [dye]/[protein] ratios), as attested by the appearance of a hypsochromically shifted absorption band (H‐band) that overlaps with the spectral shoulder of the respective dye monomer. As predicted by the molecular exciton theory, the intersystem crossing efficiency in H‐type dimers is expected to be higher than in the respective dye monomers, and photoinduced electron transfer events are intrinsically favored in dye aggregates as a result of the physical contact between donor and acceptor. We have found that when triarylmethanes are noncovalently bound to BSA their photoreactivity undergoes a remarkable enhancement, and that the photooxidation mechanism type I is particularly favored in the macromolecular environment. A comparative examination of the behavior of triarylmethane dyes with that of methylene blue have shown that in the case of methylene blue the binding phenomenon also favor the type I mechanism.
Oxidation of Chiral 1,4‐Cyclohexadienes: A Comparison of Chemically and Photochemically Generated Singlet Oxygen1O2(1Δg)
Authors: Nardello V. , Aubry J. M. , Linker T. 
Published: January 2008

AbstractChiral alkyl‐substituted 2,5‐cyclohexadiene‐l‐carboxyIic acids la‐c have been oxidized in water and in methanol with singlet oxygen, 1O2 (1Δg), generated either photochemically or chemically from the catalytic system hydrogen peroxide/sodium molybdate. These methods were compared in terms of chemo‐, regio‐ and diastereoselec‐tivities and the chemical (kT) and physical (kq) quenching rate constants of 1O2 were determined. The ratio of the cis and trans isomers of the hydroperoxides 2a‐c is not influenced by the source of 1O2 but, on the other hand, it depends slightly on the solvent and greatly on the steric hindrance of the substituents linked to the chiral carbon. The results may be interpreted on the basis of the successive formation of an exciplex and a perepoxide that evolves either by giving the final allylic hydroperoxide or by dissociating into the starting substrate and singlet or triplet oxygen.
Long‐Range Electron Transfer in Rigid 310‐Helical Oligopeptides Containing Redox Cyclic a‐Amino Acids
Authors: Lang Kamil , Kuki Atsuo 
Published: January 2008

AbstractIntrahelical photoinduced electron transfer processes (ET) in conformationally restricted oligopeptides have been studied by nanosecond time‐resolved transient spectroscopy. The helical peptides were constructed from ste‐rically hindered a‐aminoisobutyric acid (Aib) and two cyclic a‐amino acids (Aib class) bearing electron acceptor and donor side chains (DkNap, ThQx). This helical backbone design provides high conformation stability, as previously demonstrated, and yields reliable 310‐helical architectures in solution. The forward ET between ThQx and 3DkNap is followed by a slow back ET thus giving rise to an accumulation of the charge‐separated ion pairs for hundreds of nanoseconds. We demonstrate the modulation of electronic interactions by the number of intervening Aib residues separating acceptor‐donor side chains and propose modifications of the peptide framework by inclusion of a non‐Aib amino acid residue. These well‐defined and sterically stable frameworks are suited for the precise evaluation of intrahelical electron transfer processes mediated by peptides.
Lifetime Quenching of the Fluorophore: A Signature of Magnetic Field Maximization
Authors: Aichf Sanjukta , Basu Samita 
Published: January 2008

AbstractThe fluorescence lifetime quenching of the fluorophores in the presence of quenchers were measured with the variation of solvent polarity (e) for the two donor‐acceptor (D‐A) pair, JV‐ethyl carbazole‐1,4 dicyanobenzene and pyrene‐N,N‐dimethylaniline. We observed that maximum quenching of lifetimes occurred at the ε where maximum magnetic field effects had been achieved for both the pairs. The importance of the nature of the ex‐ciplex and the distance between D and A in magnetic field maximization has also been elucidated.
Chirality and Spectroscopic Changes Induced by the Recognition of Ethyl 5‐Amino‐2‐methyl‐1,2‐dihydro‐3‐phenylpyrido[3,4‐b]pyrazin‐7‐yl Carbamate Analogs by Tubulin
Authors: Peyrot V. , Barbier P. , Sarrazin M. , Briand C. , Andreu J. M. 
Published: January 2008

AbstractThe two chiral isomers of ethyl 5‐amino‐2‐methyl‐l,2‐di‐hydro‐3‐phenylpyrido[3,4‐b]pyrazin‐7‐yl carbamate, NSC 613863 (R‐isomer)‐(+) and NSC 613862 (S‐isomer)‐(‐) (CI980) and the three achiral analogs NSC 330770 (2‐de‐methylated analog A), NSC 337238 and C179 are potent microtubule inhibitors. These ligands interact with tubulin overlapping the colchicine binding site. This study addresses the effects of recognition by tubulin on the conformational properties of the ligands. The near‐UV CD (circular dichroism) band of the R‐isomer was suppressed, while that of the S‐isomer displayed a more intense negative band when these compounds were bound to tubulin. Interestingly, the three other initially achiral compounds became optically active upon binding to tubulin; particularly, analog A exhibited a negative CD band on the order of magnitude of chiral compounds. The CD changes are reversible, highly specific and actually permit measuring the binding of the ligands by tubulin. These CD changes are compatible with the deformation of the bound ligands. Fluorescence emission is strongly enhanced and blue shifted upon binding to tubulin. Water among a solvent series had a specific solvent effect, except on the 1,2‐dehydro analogs NSC 337238 and C179, suggesting hydrogen bonding to Nl. The emission of tubulin‐bound R‐isomer, S‐isomer and analog A could be mimicked by solvent viscosity, supporting the notion that the intramolecular rotation between the pyridopyrazine and phenyl rings is frozen upon binding.
The Effects of pH and Ionic Strength on the Aggregation of Bacteriochlorophyll c in Aqueous Organic Media: The Possibility of Two Kinds of Aggregates
Authors: Ishii Takasada , Uehara Kaku , Ozaki Yukihiro , Mimuro Mamoru 
Published: January 2008

AbstractThe aggregation behavior of two homologs of bacteriochlorophyll c (BChl c) in various media was investigated for the effects of pH and salt, and the corresponding structures were analyzed by Fourier transform (FT)‐IR spectroscopy. R‐[P, E] BChl cF (31‐R‐form of BChl c with a propyl group at the C‐8 position and an ethyl group at the C‐12 position) and R‐[E, E] BChl cF (31‐R‐form of BChl c with two ethyl groups at positions C‐8 and C‐12) were isolated from the green sulfur bacterium Chloro‐bium limicola. Aggregates of each homolog showed a pH‐dependent shift of the absorption maximum; at low pH, the peak moved to the red. This tendency was also revealed by circular dichroic spectra. A similar red shift of the peak was also induced by a high concentration of salt (NaCl) or buffer for both homologs. The FT‐IR spectrum indicates that at low pH, both homologs formed a rather amorphous aggregate. On the other hand, a regular structure of R‐[P, E] BChl cF was indicated in an acetone‐water mixture. This structure was stabilized by a triangular interaction among three pigment molecules through the Mg‐OH (3>) O = C (131) linkage. This structure was not found for R‐[E, E] BChl cF. These results indicate that the replacement of the side chain at the C‐8 position on the macrocycle induces a change in aggregation behavior. A possible heterogeneity of the in vivo rod structure of chlorosomes in green sulfur bacteria is discussed based on the above results.
Selective Photocleavage of DNA and RNA by Anthraquinone Derivatives: Targeting the Single‐Strand Region of Hairpin Structures
Authors: Fernandez‐Saiz Maria , Henderson Paul T. , Wilson W. David , Schuster Gary B. 
Published: January 2008

AbstractA tetracationic anthraquinone derivative (27AQS2) binds to hairpin DNA and RNA. Ultraviolet irradiation of the bound quinone causes cleavage in the loop region of both oligonucleotides and at guanines in the stem region of the DNA hairpin. The absence of observable strand cleavage at guanines in the RNA hairpin suggests that either aniline treatment does not cause cleavage at damaged guanines in RNA or that radical cation migration does not occur readily in RNA duplexes. The ability to target the single‐stranded regions of DNA and RNA structures is an important property of this photonuclease.