bluuebunny/crossref_metadata_2025_split huggingface dataset:
VECTORIAL ELECTRON TRANSPORT ACROSS LIPID VESICLE MEMBRANES DRIVEN BY TWO PHOTOREACTIONS. I. ETHYLENEDIAMINETETRAACETIC ACID AS AN ELECTRON DONOR via FLAVIN TRIPLET STATE IN THE INNER COMPARTMENT AND CYTOCHROME c AS AN ELECTRON ACCEPTOR FROM CHLOROPHYLL TRIPLET STATE IN THE OUTER COMPARTMENT
Authors: Zhao Zhan‐Gong , Tollin Gordon 
Published: January 2008

AbstractNegatively charged vesicle suspensions containing chlorophyll a (chl) dissolved in the lipid bilayer, flavin mononucleotide (FMN) and/or ethylenediaminetetraacetic acid (EDTA) enclosed in the inner compartment as electron sources and oxidized cytochrome c (cyt c[ox]) in the outer compartment as an electron acceptor have been studied using laser flash photolysis and steady‐state irradiation methods. Cytochrome c initially quenches the chl triplet state (3chl) generating the chlorophyll cation radical (chi+′) in the membrane. Reverse electron transfer from cyt c(red) to chl+. subsequently occurs in a kinetically biphasic reaction, with rate constants of 430 pT 30 and 21.9 pT 1.7 s−1 for the fast and slow phases, respectively. In the absence of FMN, reduction of chl+′ by EDTA in the inner compartment can be observed during steady‐state irradiation but not in a laser flash photolysis experiment. This is due to a low reaction yield, which is probably limited by the repulsive electrostatic interaction between EDTA and the negatively charged membrane. When FMN was enclosed together with EDTA in the inner Compartment, the reaction yield of vectorial electron transfer across the bilayer from EDTA to cyt c(oX) was increased by a factor of six during steadystate white light irradiation. Laser flash photolysis and steady‐state irradiation experiments using red and blue light excitation have demonstrated that the enhancement mechanism involves the formation of fully reduced FMN by blue light‐sensitized photooxidation of EDTA via the flavin triplet state, occumng simultaneously with red lightsensitized electron transfer to cyt c via the chlorophyll triplet state.
GENE EXPRESSION OF TEH B875 LIGHT‐HARVESTING PREPOLYPEPTIDES FROM RHODOSPIRILLUM RUBRUM IN ESCHERICHIA COLI
Authors: Ghosh Robin , Cornacchia Luigi , Bachofen Reinhard 
Published: January 2008

AbstractThe gene coding for the prepolypeptides of α and β, obtained as a 429 bp fragment from chromosomal DNA of Rhodospirillum rubrum S1 by polymerase chain reaction amplification, were cloned in tandem into the high‐level expression vector pOTSNco 12 for epxression in Escherichia coli. The vector pOTSNco 12 is a derivative of the pAS vector system, which contains the strong ΛPL promotor and is under tight control by the cI857 repressor encoded by the expression strain AR58. Induction of transcription from the ΛPL promotor is achieved by shifting the growth temperature from 32 to 42d̀C. Expression of the gene products was monitored by sodium dodecylsulfate polyacrylamide gel electrophoresis and western blotting. The expressed B875 light‐harvesting prepolypeptides were located in the E. coli inner membrane and could not be removed by washing with high salt. The amount of expressed B875 light‐harvesting prepolypeptides was estimated to be about 0.1% of the total soluble protein.
PHOTODYNAMIC DESTRUCTION OF LYSOSOMES MEDIATED BY NILE BLUE PHOTOSENSITIZERS
Authors: Lin Chi‐Wei , Shulok Janine R. , Kirley Sandra D. , Bachelder Cindy M. , Flotte Thomas J. , Sherwood Margaret E. , Cincotta Louis , Foley James W. 
Published: January 2008

AbstractPrevious studies have established that a number of Nile blue derivatives are potent photosensitizers and that they are localized primarily in the lysosomes. The present study examines whether the lysosome is a main target of the photocytotoxic action mediated by these sensitizers. Chosen for this study were NBS‐61 and sat‐NBS, which represented, respectively, derivatives with high and moderate degrees of lysosomal selectivity. Overall results indicated that both derivatives are very effective in mediating a photodestruction of lysosomes. This is indicated by the light‐and drug‐dose‐dependent losses of acid phosphatase staining particles, reduction of hexosaminidase in the lysosomecontaining subcellular fraction, and impairment of the lysosomes to take up and sequester acndine orange. Ultrastructurally, swollen and ruptured lysosomes were seen as one of the first evidences of cell damage mediated by these photosensitizers. However, the study also showed that sat‐NBS, which is less lysosomal selective, was less effective in mediating lysosomal destruction. Also, the degree of lysosomal destruction mediated by sat‐NBS did not parallel the degree of cytotoxicity generated. This implies that for derivatives that are not exclusively localized in the lysosome, other subcellular sites may also be damaged by the photodynamic action and may play a role in the photocytotoxic process.
PHOTOSENSITIZATION WITH ETIOBENZOCHLORINS AND OCTAETHYLBENZOCHLORINS
Authors: Kessel David , Morgan Alan 
Published: January 2008

AbstractThe photophysical and photobiological properties of a series of etiobenzochlorins were evaluated in cell culture using murine leukemia L1210 cells. In the series of agents tested, the chlorin‐(mono)sulfonate was the most efficacious, the tin chlorin somewhat less so and the tin chlorin‐sulfonate much less active. The parent chlorin was essentially inactive at the limit of solubility. Photodamage was assessed by measuring alterations in surface hydro‐phobicity (via a two‐phase partitioning procedure), amino acid transport and membrane potential. Additional information was provided from fluorescence microscopy, which was used to identify sites of sensitizer binding and effects of photodamage on the binding patterns of fluorescent probes specific for mitochondria, lysosomes and plasma membranes. Effects of photodamage on fluorescence lifetime distribution of the membrane probe trimethylamino‐diphenyl hexatriene were examined. The data obtained were consistent with localization of the parent etiobenzochlorin and tin derivative at lysosomal loci. the chlorin‐sulfonate at plasma and mitochondrial membranes and tin‐sulfonate at the cell surface.
INHIBITION OF 80 kDa PROTEIN PHOSPHORYLATION BY SHORT‐WAVELENGTH UV LIGHT IN NIH 3T3 CELLS
Authors: Shin Incheol , Yoon Yoo Sik , Kang Kewon , Park Sang Dai , Joe Cheol O. 
Published: January 2008

AbstractThe exposure of NIH 3T3 fibroblast cells to 254 nm UV radiation resulted in a temporary depression of DNA synthesis and inhibition of 80 kDa protein phosphorylation. This inhibition of protein phosphorylation was correlated with decreased protein kinase C activity in the membrane fractions of UV‐damaged cells. The inositol tnphosphate contents measured, by the competitive binding assay using bovine adrenal binding protein, showed 80% reduction in the fibroblasts treated with 15 J/m2 of UV light. The intracellular diacylglycerol concentration was also markedly reduced in UV‐damaged cells. The results suggest that UV light causes acute reductions of inositol triphosphate and diacylglycerol contents in cells along with decreases in membrane protein kinase C activity, which leads to the inhibition of phosphorylation of an acidic protein of 80 kDa.
ADRIAMYCIN RESISTANCE IN CHINESE HAMSTER FIBROBLASTS FOLLOWING OXIDATIVE STRESS INDUCED BY PHOTODYNAMIC THERAPY
Authors: Fisher Anita M. R. , Ferrario Angela , Gomer Charles J. 
Published: January 2008

AbstractPhotodynamic therapy (PDT) generates reactive oxygen species that are responsible for the initial cytotoxic events produced by this treatment. An extended (16 h) porphyrin incubation prior to light irradiation increased expression of the 75, 78 and 94 kDa glucose‐regulated stress proteins (GRP), as well as the cognate form of the 70 kDa heat shock protein. However, these stress proteins were not induced following isoeffective PDT doses using a short (1 h) porphyrin incubation protocol. In the current study, Chinese hamster fibroblasts were used to examine sensitivity to adjunctive PDT and adriamycin as previous reports indicate a correlation between stress protein synthesis and a decrease in adriamycin cytotoxicity. Treatments that either induced GRP (i.e. PDT with an extended porphyrin incubation or exposure to the calcium ionophore A23187) or did not induce GRP (i.e. PDT with a short porphyrin incubation or UV irradiation) were followed at increasing time intervals with a 1 h adriamycin incubation. A time‐dependent decrease in adriamycin cytotoxicity was observed when cells were first exposed to either of the PDT protocols or to A23187. Alterations in intracellular drug levels did not account for the change in adriamycin sensitivity. Likewise, intracellular glutathione concentrations and antioxidant enzyme activities were not significantly altered following PDT or A23187. Parameters associated with altered adriamycin sensitivity included a decrease in the percentage of S phase cells following PDT and A23187 as well as a depletion of intracellular ATP after PDT using the extended porphyrin incubation. These results demonstrate that PDT can be added to the growing list of diverse stresses producing transient resistance to adriamycin and that stress protein induction is not universally associated with all oxidative treatments inducing this resistance.
PHOTOACTIVE METHYLENE BLUE DYE DERIVATIVES SUITABLE FOR COUPLING TO PROTEIN
Authors: Motsenbocker M. , Masuya H. , Shimazu H. , Miyawaki T. , Ichimori Y. , Sugawara T. 
Published: January 2008

AbstractMethylene blue is a very strong photoactive dye that has an absorption peak (668 nm) that corresponds well to a popular low‐cost diode laser. However, it has not been used in photodynamic tumor therapy and immunodiagnostics because it cannot be covalently coupled to protein. Therefore, methylene blue derivatives having a succinimido or maleimido functional group were synthesized and coupled to antibody, serum albumin and transfemn proteins. Incorporation of dye into antibody protein at high ratios (more than three per molecule) caused precipitation and loss of antibody activity. Inclusion of one or more carboxylic acid residues in the methylene blue derivative before coupling to protein alleviated the precipitation problem, and up to 36 methylene blue dye molecules could be attached to an antibody fragment using bovine serum protein as a carrier. Methylene blue derivatives and protein complexes formed from them oxidized luminol when stimulated with red light. The new dye conjugates were used in an optically pumped chemiluminescence immunoassay for α‐fetoprotein. These compounds and techniques should also be useful for photodynamic tumor therapy where it is desired to attach a red‐absorbing photoactive dye to antibody protein.
In vitro PHOTODYNAMIC EFFECTS OF LYSYL CHLORIN p6: CELL SURVIVAL, LOCALIZATION AND ULTRASTRUCTURAL CHANGES
Authors: Leach Michael W. , Higgins Robert J. , Autry Susan A. , Boggan James E. , Lee Shwn‐Ji H. , Smith Kevin M. 
Published: January 2008

AbstractThe in vitro cell survival, localization and ultrastructural changes following irradiation were examined in 9L glioma cells sensitized with a new photosensitizer, lysyl chlorin p6 (LCP). In clonogenic assays, LCP was 10–100‐fold more phototoxic than photofrin II on a μg/mL basis. Lysyl chlorin p6 uptake was blocked when cells were incubated at 2°C. In view of the chemical properties of LCP, this finding indicates that uptake probably occurred through the endocytic pathway. Fluorescence studies showed LCP localized in a region of the endocytic compartment similar in size, shape and distribution to that labeled by lucifer yellow CH (LY), as well as localizing diffusely throughout the perinuclear cytoplasm. Cells stained with both LY and LCP, however, had distinctly separate regions of staining. Lysyl chlorin p6 localization differed from that of fluorescent probes labeling the mitochondria, Golgi apparatus and endoplasmic reticulum. Ultrastructural changes at both 2 and 30 min after laser irradiation were similar. Mitochondria were often condensed or swollen and also had constrictions and cytoplasmic invaginations. The Golgi apparatus, perinuclear space and rough endoplasmic reticulum (RER) were dilated. These data demonstrate that LCP localizes in a portion of the endosomal compartment, but that morphologic damage initially occurs in the mitochondria, Golgi apparatus and RER.
ROLE OF HYDROXYL‐BEARING AMINO ACIDS IN DIFFERENTIALLY TUNING THE ABSORPTION SPECTRA OF THE HUMAN RED AND GREEN CONE PIGMENTS
Authors: Merbs Shannath L. , Nathans Jeremy 
Published: January 2008

AbstractThe human red and green cone pigments differ at either 15 or 16 amino acids, depending upon which polymorphic variants are compared. Seven of these amino acid differences involve the introduction or removal of a hydroxyl group. One of these differences, a substitution of alanine for senne at position 80, was found previously to produce a 5 nm blue shift. To determine the role of the remaining six hydroxyl group differences in tuning the absorption spectra of the human red and green pigments, we have studied six site‐directed mutants in which single amino acids from the green pigment have been substituted for the corresponding residues in the red pigment. Blue shifts of 7 and 14 nm were observed upon substitution of phenylalanine for tyrosine at position 277 and alanine for threonine at position 285, respectively. Single substitutions at positions 65, 230, 233, and 309 produced spectral shifts of 1 nm or less. These data are in good agreement with a model based upon sequence comparisons among primate pigments and with the properties of site‐directed mutants of bovine rhodopsin. Nonadditive effects observed in comparing the absorption spectra of red‐green hybrid pigments remain to be explained.
THE EFFECT OF ACCEPTOR GROUP VARIATION ON THE SOLVATOCHROMISM OF DONOR‐ACCEPTOR FLUOROPHORES
Authors: Anstead Gregory M. , Carlson Kathryn E. , Kym Philip R. , Hwang Kwang‐Jin , Katzenellenbogen John A. 
Published: January 2008

Abstract The absorption and emission characteristics of five hydroxytetrahydrochrysenes substituted with acceptor groups (nitro, cyano, methylketone, 1° amide and methyl ester) (THC‐NO2, THC‐CN, THC‐COCH3, THC‐CONH2 and THC‐CO2CH3, respectively) were investigated in an extensive set of solvents. The order of absorption and fluorescence bathochromicity are: THC‐NO2 > THC‐COCH3 > THC‐CN ≥ THC‐CO2CH3 > THC‐CONH2 and THC‐NO2 >> THC‐COCH3 > THC‐CO2CH3 > THC‐CN > THC‐CONH2, respectively. The emission spectra of these compounds are sensitive to the solvent polarity (ET[30] scale) in the order: THC‐NO2 > THC‐COCH3 > THC‐CO2CH3 > THC‐CONH2 > THC‐CN. The response of the emission maxima of these compounds to the solvent polarity and hydrogen‐bond donor/acceptor properties (π*/α/β and acity/basity scales) was also determined. The emission energies of THC‐NO2 were most sensitive to π*, β, acity, and basity of the solvent; those of the amide were least sensitive to the solvent π*, β, and basity.The ground‐ and excited‐state dipole moments were determined by semiempirical molecular orbital calculations and the absorption/fluorescence solvent‐shift method, respectively. THC‐NO2 had the largest ground‐ and excitedstate moments. The ester and amide had the smallest ground‐ and excited‐state moments, respectively. In general, unsatisfactory results were obtained for correlations of the emission and absorption energies, fluorescence solvatochromism and the ground‐ and excited‐state dipole moments with the Hammett substituent constants of the five acceptor groups. Acceptable correlations were obtained for the absorption and emission energies and the fluorescence solvatochromism with the substituent constants if the cyano compound was excluded.
OXIDATION OF INDOLE‐3‐ACETIC ACID BY SONICATED NEUTROPHILS. PITFALLS IN CORRELATING EPR SIGNALS AND CHEMILUMINESCENCE
Authors: Escobar Jorge A. , Vásquez‐Vivar Jeannette , Cilento Giuseppe 
Published: January 2008

Abstract –The oxidation‐peroxidation of indole‐3‐acetic acid by sonicated neutrophils, unlike the horseradish peroxidase‐catalyzed process, features not only the skatole radical, but also a tertiary carbon‐centered radical in the electron paramagnetic resonance (EPR) spectrum. Moreover, emission occurs only in the red.From the present and earlier data it is concluded that the observation of the skatole radical does not necessarily indicate its involvement in the 1ΔgO2 generating process. Also unlikely is a correlation between the tertiary carbon‐centered radical and red emission.Our results indicate that in general great care must be taken in attempting to correlate EPR signals with chemi‐luminescence and with oxygen consumption.
In vitro PHOTODEGRADATION OF CHLORPROMAZINE
Authors: Broeke L. T. van den , Ouijja E. H. , Bojarski J. , Henegouwen G. M. J. Beyersbergen VAN 
Published: January 2008

AbstractThe in vitro photodecomposition of chlorpromazine (CPZ) was investigated with the aim to evaluate possible reactive determinants that could play a role in the occurrence of the in vivo‐observed photosensitivity. In view of the in vivo situation, CPZ was dissolved in low concentration in buffered aqueous solution (pH 7.4) or in dilute human serum and irradiated with low intensity (5–7 W m‐2) UV‐A and UV‐B. No distinct difference was found between UV‐A or UV‐B irradiation as far as photoproduct formation is concerned. This suggests the same degradation mechanism at both wavelength ranges. In buffered aqueous solution, irradiation of CPZ resulted in 65 and 90% 2‐hydroxypromazine (PZOH), 5 and 7% promazine (PZH) and 2 and 0% chlorpromazinesulfoxide (CPZSO) under aerobic and anaerobic conditions, respectively. In dilute human serum, there was only a shift in the PZH/PZOH ratio, probably as a result of H‐atom or electron donation by sulfur containing groups present in proteins. The results demonstrate that photodegradation of CPZ in vitro, under conditions relevant to the in vivo situation, proceeds almost entirely by dechlorination rather than by radical cation formation (the essential pathway of CPZSO production). Thus we conclude that the thiyl radical cation probably does not play a major role in the in vivo‐observed phototoxic reactions.
REDUCED PHOTOINACTIVATION OF 10‐DODECYL ACRIDINE ORANGE‐SENSITIZED YEAST CELLS AT HIGH FLUENCE RATES MEASUREMENTS AND COMPUTER SIMULATIONS
Authors: Keij Jan F. , Jansen Jan Th. M. , Schultz Frank W. , Visser Jan W. M. 
Published: January 2008

Abstract‐During the development of a photodamage cell sorter several photosensitizers were tested for their ability to photoinactivate more than 90% of the sensitized cells after a brief irradiation with a fluence of 10 kJ/m2. In pilot experiments, yeast cells sensitized with 10‐dodecyl acridine orange (DAO) were effectively photoinactivated after receiving a fluence of 10 kJ/m2 delivered in 8 s. However, when the same fluence was delivered in 3 μs during passage through a focused laser beam in the cell sorter, all cells survived.Computer simulations of the relevant photophysical and chemical reactions inside the irradiated cell were used to investigate the cause of this phenomenon. The results indicated that the absence of photoinactivation by DAO, after flash irradiations, was caused by the combined effects of (1) limited oxygen diffusion into the cell and (2) a reduced number of collisions between photosensitizer triplet and oxygen molecules during the irradiation due to saturation of the intracellular photosensitizer triplet concentration. The contributions of triplet‐triplet annihilation and triplet quenching by ground state photosensitizer molecules were found to be minimal and not significant. These findings indicate that Type II photosensitizers are incapable of rapid selective photoinactivation in cell sorters.
PHOTOPHYSICS OF THE FLUORESCENT Ca2+ INDICATOR QUIN‐2
Authors: Bergh Viviane Van den , Boens Noël , Schryver Frans C. De , Gallay Jacques , Vincent Michel 
Published: January 2008

AbstractThe photophysics of the complex forming reaction between Quin‐2 and Ca2+ were investigated using steady‐state and time‐resolved fluorescence measurements. The fluorescence decay traces were analyzed with global compartmental analysis yielding the following values for the rate constants at room temperature in aqueous solution with EGTA as Ca2+ buffer: k01= 8.6 times 108 s−1, k21= 1 times 1011M−1 s−1, k02= 8.8 times 107 s−1, k12= 4 times 104 s−1. k01 and k02 denote the respective deactivation rate constants of the Ca2+ free and bound forms of Quin‐2 in the excited state. The constant k21 represents the second‐order rate constant of binding of Ca2+ and Quin‐2 in the excited state while k12 is the first‐order rate constant of dissociation of the excited Ca2+:Quin‐2 complex. From the estimated values of k12 and k21 the dissociation constant Kd* in the excited state was calculated. It was found that pKd* (6.4) is slightly smaller than pKd (7.2). There was no interference of the excited‐state complex forming reaction with the determination of Kd. Intracellular Ca2+ concentrations can thus accurately be determined from fluorometric measurements using Quin‐2 as Ca2+ indicator.
PREFERENTIAL INHIBITION OF NUCLEOSOME ASSEMBLY BY ULTRAVIOLET‐INDUCED (6‐4)PHOTOPRODUCTS
Authors: Matsumoto Hideki , Takakusu Akira , Mori Toshio , Ihara Makoto , Todo Takeshi , Ohnishi Takeo 
Published: January 2008

AbstractWe reconstituted nucleosomes in vitro using two kinds of damaged pBR322 plasmid DNA carrying cyclobutane pyrimidine dimers (CPD) or (6‐4)photoproducts. The results indicate that nucleosome assembly is inhibited preferentially by (6‐4)photoproducts compared with CPD, suggesting that the regions carrying (6‐4)photoproducts retain their nucleosome‐free form, i.e. linker‐like conformation until completion of the repair processes.
INDUCTION OF SLOWLY DEVELOPING ALKALI‐LABILE SITES IN HUMAN P3 CELL DNA BY UVA AND BLUE‐ AND GREEN‐LIGHT PHOTONS: ACTION SPECTRUM
Authors: Peak Jennifer G. , Peak Meyrick. J. 
Published: January 2008

AbstractAction spectra (365–520nm) for the formation of DNA single‐strand breaks (SSB) and slowly developing alkali‐labile sites (SDALS) in human teratocarcinoma P3 cells in culture were determined. Induction of SDALS results from the absorption of blue‐ and green‐light photons. The spectrum has a broad peak that is maximal between 400 nm to 500 nm and declines sharply above and below these wavelength regions. Negligible yields of SDALS were produced by photons at wavelengths of 365 nm or shorter and at 520 nm or longer, whereas for SSB, the action increases with shorter wavelength throughout the whole spectral range studied. The configuration of the SDALS action spectrum suggests that the primary chromophore, and therefore possibly the photosensitizer, is a mixture of porphyrin and flavin residues.