bluuebunny/crossref_metadata_2025_split huggingface dataset:
Detailed Mechanism of Phenol‐Inhibited Peroxidase‐Catalyzed Oxidation of Indole‐3‐Acetic Acid at Neutral pH*
Authors: Krylov Sergey N. , Dunford H. Brian 
Published: January 2008

ABSTRACTThe inhibition of horseradish peroxidase (HRP)‐cata‐lyzed oxidation of indole‐3‐acetic acid (IAA) by a phenol, caffeic acid (CA), was studied using both a kinetic approach and computer simulation. The presence of CA resulted in a lag period in IAA oxidation. The lag period increased slowly with increasing [CA] until a critical concentration, [CA]cr, was reached, then it increased much faster when [CA] was greater than [CA]cr. The [CA]cr was proportional to [IAA] and did not depend upon [HRP]. Caffeic acid was oxidized by compound I and compound II of HRP with bimolecular rate constants (6.8 ± 107 and 2.1 ± 107M‐1s−l), which were much higher than the corresponding rate constants for IAA oxidation (2.3 ± 103 and 2.0 ± 102M−1s−1). Our experimental data show that CA inhibits IAA oxidation because it is able to compete effectively as a peroxidase substrate. A model based on a detailed mechanism of IAA oxidation was investigated using computer simulation. A rate constant driving nonenzymatic hydroperoxide formation in IAA solution was determined, 3.0 × 10−‐7 s−1. The model quantitatively describes the experimental results of this work and also qualitatively explains data published earlier. The critical inhibitor concentration is approximately equal to twice the concentration of hydroperoxide in IAA solution at the time of inhibitor addition. Therefore hydroperoxide Concentration can be calculated from the determination of critical inhibitor concentration.
Chemiluminescence Triggered by Hydrolase Activity in a Horseradish Peroxidase/H2O2‐Coupled Assay*
Authors: Campa Ana , Andrade Andrea de Castro , Catalani Luiz Henrique 
Published: January 2008

ABSTRACT2‐Methyl‐1‐propenyl acetate (MPA) was hydrolyzed by wheat lipase, pancreatic lipase, hydrolases and lipopro‐tein lipase from serum in a reaction that produces 2‐methyl‐1‐propenol. The latter was subsequently oxidized by horseradish peroxidase (HRP)/H2O2/O2 yielding triplet acetone that emits visible light. The integrated light emission was proportional to the units of lipase or volume of serum present. When pancreatic lipase was assayed, light emission was observed in the presence of bile salt as surfactant and chlorophyll a as light sensitizer. The potential application of this reaction in determinations of hydrolase/Iipase activities is discussed.
Development of Monoclonal Antibodies Against a Riboflavin‐Tryptophan Photoinduced Adduct: Reactivity to Eye Lens Proteins*
Authors: Diaz Marisol , Becker M. Ines , De Ioannes Alfredo E. , Silva Eduardo 
Published: January 2008

ABSTRACTWe describe here the development of monoclonal antibodies to the hapten tryptophan‐riboflavin, generated by irradiation of a solution of bovine serum albumin in the presence of riboflavin. The specificity of the three obtained monoclonal antibodies, named lE6, 5H5, 5AS all belonging to the IgGl isotype, was assessed by a competitive enzyme‐linked immunosorbent assay in the presence of an increasing concentration of the tryptophan‐riboflavin adduct, obtained from an irradiated riboflavin‐sensitized tryptophan solution. It was demonstrated that the tryptophan‐riboflavin antibodies react with the soluble proteins of the eye lens; this reaction was more intense in the old rat lenses as compared to the young ones, and a maximum binding of the antibodies was obtained with the soluble protein fraction from the human catar‐actous lens. By indirect immunofluorescence, a reactivity associated with the protein matrix, localized in the lens central zone, was observed. In the peripheral zone of the lens, where the younger cells are found, a marked im‐munofluorescent emission was observed on structures preferentially localized in the nuclei.
Photochemistry and Photobiology of Furocoumarin Hydroperoxides Derived from Imperatorin: Novel Intercalating Photo‐Fenton Reagents for Oxidative DNA Modification by Hydroxyl Radicals*
Authors: Adam Waldemar , Berger Maurice , Cadet Jean , Dall'Acqua Francesco , Epe Bernd , Frank Silvia , Rarnaiah Danaboyina , Raoul Sebastian , Saha‐Möller Chantu R. , Vedaldi Daniela 
Published: January 2008

ABSTRACTPhotochemical and photobiological properties of the im‐peratorin‐derived furocoumarin hydroperoxides la, la', 2a and 2a’have been investigated. Irradiation (350 nm) of the hydroperoxide 2a’afforded the alcohol 2b (2%), a diastereomeric mixture of the hydroxy epoxide 2c (40%; diastereomeric ratio = 80:20) and the epoxide 2d (8%). The formation of these products was rationalized in terms of homolysis of the hydroperoxide bond initiated by intramolecular energy transfer from the photoexcited furocoumarin chromophore. The quantum yields for the photolytic decomposition of hydroperoxides were estimated to be in the range of 0.03–0.85 and decreased in the order 2a ≫ 2a′≫ 1a′≥ 1a. The involvement of hydroxyl radicals in these reactions was established by trapping experiments with benzene and spectroscopic evidence was obtained by EPR spin trapping with 5,5‐di‐methylpyrroline‐N‐oxide. Fluorescence titration, DNA melting and linear dichroism studies of furocoumarins indicated that these compounds undergo efficient com‐plexation and also intercalation into the DNA. The binding parameters K (intrinsic binding constant) and l/n (frequency of binding sites) of complexes between furocoumarin derivatives and DNA were determined to be in the range of 3900–23 900 M‐l and 0.017–0.045. The pho‐toreaction of la’and lb’with 2′‐deoxyguanosine (dGuo) afforded exclusively 7,8‐dihydro‐8‐oxo‐2′‐deoxy‐guanosine (8‐oxodGuo), presumably through singlet oxygen, which was formed in a type II photooxidation process. In contrast, the hydroperoxide 2a oxidized dGuo to oxazo‐lone as major and 8‐oxodGuo as minor products through hydroxyl radicals, which were generated from 2a under photolytic conditions. Interestingly, the photoreactions of furocoumarins with salmon testes DNA showed that the highly reactive (φ= 0.85) hydroperoxide 2a is also most efficient in inducing the mutagenic DNA oxidation product 8‐oxodGuo. Hence, the novel furocoumarin hydroperoxide 2a constitutes the first intercalating photo‐Fen‐ton reagent and serves as convenient hydroxyl radical source for genotoxicity studies.
Pyrene Fluorescence in the Presence of Acrylic Acid‐Ethyl Methacrylate Copolymers: Effect of the Copolymer Composition in the Formation of Microdomains*
Authors: de Oliveira Vera A. , Tiera Marcio J. , Gehlen Marcelo H. , Neumann Miguel G. 
Published: January 2008

ABSTRACTThe properties of aqueous solutions of acrylic acid‐ethyl methacrylate (EMA) copolymers have been investigated using pyrene and pyrene pyrenebutyltrimethylammonium (PBTA) as probes. Static and dynamic fluorescence have been used to obtain information about the microenviron‐ments formed. Micropolarity studies using the I1/I3 ratio of the vibronic bands of pyrene show the formation of hydrophobic domains. At low pH the increase of the amount of ethyl methacrylate in the copolymers shows that aqueous microdomains are excluded from the core of the polymer, for the copolymers with high content of EMA low polarity microdomains are still present on the mac‐romolecular chain even at higher pH. The pH‐induced conformational transition indicates that the more hydro‐phobic copolymers adopt a more tightly coiled conformation. Compared to PAA, the decay times for both probes are increased twice for the polymer with 25% molar proportion of EMA. The fluorescence quenching of the probes by nitromethane depends on pH, copolymer composition and probe structure. The efficiency of quenching decreases with increase of the EMA proportion in the copolymers. Pyrene is more efficiently quenched than PBTA as a consequence of the latter being located in more internal (less accessible) sites of the polymer structure.
Photophysical and Aggregation Studies of t‐Butyl‐Substituted Zn Phthalocyanines
Authors: Fernández Daniel A. , Awruch Josefina , Dicelio Lelia E. 
Published: January 2008

ABSTRACTThree potential photosensitizers for photodynamic therapy: tetra‐t‐butyl phthalocyaninato Zn(II), tetrakis‐(1,1‐dimethyl‐2‐phthalimido)ethylphthalocyaninato Zn(II), and tetrakis‐(1,1‐dimethyl‐2‐amino)ethylphthalocyaninato Zn(II), have been studied in homogeneous organic media. Dimerization constants and monomer and dimer spectra have been determined. Fluorescence, triplet and singlet oxygen quantum yìelds were measured and the photo‐physical characterization of the triplet state was performed for the three dyes. These parameters were evaluated in connection with aggregation results.
Synthesis, Photoreactivity and Cytotoxic Activity of Caged Compounds of L‐Leucyl‐L‐Leucine Methyl Ester, an Apoptosis Inducer
Authors: Odaka Mitsuyo , Furuta Toshiaki , Kobayashi Yoshiro , Iwamura Michiko 
Published: January 2008

ABSTRACTI,‐Leucyl‐L‐leucine methyl ester (Leu‐Leu‐OMe), an apoptosis inducer in natural killer cells and macro‐phages, was caged with trans‐o‐hydroxycinnamoyl (3ad), trans‐o‐mercaptocinnamoyl (4) and o‐nitrobenzyl derivatives (5a, b), and the photochemical reactivity of these derivatives in phosphate‐buffered saline containing 1% dimethyl sulfoxide and their immunological properties were studied. All of the derivatives exhibited absorplion at wavelengths longer than the UVB region. Although 3a–d and 4 were expected to isomerize to a cis isomer, which thgn cyclizes intramolecularly to give Leu‐Leu‐OMe and a coumarin derivative, cyclization efficiency was not satisfactory except for 3a. However, 3a itself caused necrosis (cell swelling) of U937 cells (a myeloid cell line). In contrast, 5a and b released Leu‐Leu‐OMe quickly and efficiently and did not affect U937 cells. Although irradiated 5b induced necrosis, irradiated 3a and 5a induced apoptosis in these cells, as evidenced by a decrease in cell size.
Measurement of UVA Exposure to Solar Radiation
Authors: Wong J. C. F. , Parisi A. V. 
Published: January 2008

ABSTRACTExposure to solar UVA (320–400 nm) radiation can damage DNA and lead to skin disorders. Conventional dosim‐etry using a single piece of polysulfone or diglycol carbonate (CR‐39) cannot provide accurate measurement of the biologically effective irradiance for erythema for the UVA waveband. A package employing four dosimeters (polysulfone, nalidixic acid, 8‐methoxypsoralen and phe‐nothiazine) has been shown to be effective for use as a spectrum evaluator for evaluating the UVA source spectrum. In Brisbane, on a horizontal position, the spectrum evaluator requires about 5 min exposure in summer and about 20 min in winter. This amounts to about 10 mJ cm‐2 of erythemal UV radiation.
Structural and Functional Changes in Catalase Induced by Near‐UV Radiation
Authors: Zigman Seymour , Reddan John , Schultz Joanne B. , McDaniel Thurma 
Published: January 2008

ABSTRACTPart one of this study shows that exposure of purified beef liver catalase in buffered solutions to BL lamps that provide a mixture of 99% UVA and 1% UVB (to be labeled UVA) alters its chemistry and enzymatic activity. Thus, its spectral absorbance lost detail, it aggregated and exhibited a lower isoelectric point and its enzymatic activity was substantially reduced.These photochemically induced changes were increased by irradiation in phosphate buffer or in physiological medium (minimal essential medium) containing riboflavin and tryptophan. Neither α‐tocopherol nor de‐feroxamine were protective against these UVA‐induced changes in pure catalase.We further investigated the effect of UVA radiation on the activity of catalase in cultured lens epithelial cells and the protective effects of antioxidants. Cultured lens epithelial cells of rabbits and squirrels were exposed to near‐UV radiation with representation in the UVA region of 99% and 1% UVB. Catalase assays were done on ho‐mogenate supernatants of cells kept dark or UV exposed. In some instances, cells were cultured in medium containing a‐tocopherol or deferoxamine prior to UV radiation. Comparisons were made between UV‐exposed lens cell catalase activity when exposure was done with or without the antioxidants. The UVA radiation was strongly inhibitory to both rabbit and squirrel lens epithelial cell catalase activities. The range of fluxes of near UV radiation was compatible with that which could reach the lens from the sunlit environment. Catalase inactivation was lessened in cells preincubated with a‐tocopherol and deferoxamine. This suggests that both singlet oxygen and hydroxyl radical formation may be involved in near‐UV damage to lens epithelial cell catalase. Such inhibition of catalase by near‐UV would enhance H2O2 toxicity and stimulate SH oxidation so as to damage the lens.
Preprogrammed and Programmed Cell Death Mechanisms of Apoptosis: UV‐Induced Immediate and Delayed Apoptosis
Authors: Godar Dianne E. 
Published: January 2008

ABSTRACTEquitoxic doses (10% clonogenic survival) of UV radiation (UVR) from the three waveband regions, i.e. UVAl (340–400 nm), UVB (290–320 nm) and UVC (200–290 nm), were shown to induce immediate or delayed apoptosis in L5178Y‐R murine lymphoma cells. Membrane and DNA damage were shown to be the most probable initiators of UVAl‐induced immediate or UVR‐induced delayed apoptosis, respectively. These UV‐induced apop‐totic processes appeared to utilize two different “core” biochemical mechanisms; however, one core mechanism could be initiated at two distinct sites (e.g. membrane or DNA) and result in disparate kinetics. In an attempt to resolve this mechanistic issue, the dependence on mac‐romolecular synthesis of each UV‐induced apoptotic mechanism was investigated. In the absence of UVR, inhibition of either transcription (actinomycin D) or translation (cycloheximide) induced apoptosis in a concentration‐ and time‐dependent manner. These results suggest that an apoptotic mechanism exists that does not require macromolecular synthesis postinsult (constitutive). The UVR data demonstrate that UVAl‐induced immediate apoptosis utilizes this constitutive mechanism (preprogrammed), while UVR‐induced delayed apoptosis utilizes the well‐known inducible mechanism (programmed). Therefore, there are two different core biochemical mechanisms of apoptotic death available to each cell: preprogrammed (constitutive) and programmed (inducible) cell death.
Characterization of the Photosynthetic Activity of Platinized Chloroplasts: A Study Using Fluorescence and Photoacoustic Techniques
Authors: Supponeva Elena , Hotchandani Surat , Carpentier Robert 
Published: January 2008

ABSTRACTIn this report, the effect of platinization on the photosynthetic activity of the chloroplast membranes is studied. Oxygen evolution, fluorescence emission and thermal de‐activation processes are modified after platinization. It is shown that photosystem II activity is affected by the hydrogen purging involved in the platinization procedure as seen by the reduced rates of oxygen evolution and a decrease in variable fluorescence. Depletion of bicarbonate from photosystem II during purging is suggested to be responsible partly for the decreased electron transfer rates and for a lower half‐saturation light intensity required for energy storage as measured by photoacoustic spectroscopy. On the other hand, the electron sink created by the reduction of hydrogen at the acceptor side of photosystem I is shown to reoxidize efficiently the plas‐toquinone pool of photosystem II.
Assembly of Photosystem I and II during the Early Phases of Light‐Induced Development of Chloroplasts from Proplastids in Spirodela oligorrhiza
Authors: McCormac Dennis J. , Marwood Christopher A. , Bruce Doug , Greenberg Bruce M. 
Published: January 2008

ABSTRACTThe aquatic higher plant Spirodela oligorrhiza, which contains proplastids when grown in the dark, was used to study light‐dependent chloroplast development. Low‐temperature (77 K) and room temperature fluorescence were utilized in situ on whole plants to examine plastid development. The dark‐grown plants contain two 77 K fluorescence peaks, at 633 nm (F633) and at 657 nm (F657), with F633 dominating. The F657 species represents protochlorophyllide that is bound to protochloro‐phyllide oxidoreductase. It was rapidly phototrans‐formed to chlorophyllide (within 5 s) via a monomolec‐ular reaction. Free protochlorophyllide (F633) was converted to chlorophyllide during a 3 h exposure to light. Photosystem (PS) assembly in Spirodela could be detected 2 h after the plants were first exposed to light, with the PSII reaction center (77 K fluorescence at 684 nm) appearing slightly before the PSI reaction center (77 K fluorescence at 725 nm). After the first reaction centers were formed the antenna complexes were added; the light‐harvesting complex (LHC) I of PSI appeared after 8 h, and 47 kDa chlorophyll protein of PSII appeared between 12 h and 24 h. After 30 h of exposure to light, the plants acquired the ability to perform a light state transition, marking the appearance of functional LHCII complexes in the developing chloroplast. Finally, it was found that photosynthetic activity, as measured by room temperature chlorophyll fluorescence, accelerated con‐comitantly with detection of the antenna complexes. Therefore, although reaction centers are detected very early during the proplastid to chloroplast conversion, they may have little activity or be unstable until the antennae are present.
Lutetium Texaphyrin (PCI‐0123): A Near‐Infrared, Water‐Soluble Photosensitizer
Authors: Young S. W. , Woodburn K. W. , Wright M. , Mody T. D. , Fan Q. , Sessler J. L. , DOW W. C. , Miller R. A. 
Published: January 2008

ABSTRACTLutetium texaphyrin, PCI‐0123, is a pure, water‐soluble photosensitizer with a large broad absorption band centered at 732 nm. The compound was tested for photodynamic therapy (PDT) effectiveness in a murine mammary cancer model. The texaphyrin macrocycle as illustrated by magnetic resonance imaging and 14C‐radiolabeled texaphyrin studies was shown to be tumor selective; a tumor‐to‐muscle ratio of 10.55 was seen after 5 h. Lutetium texaphyrin, at a drug dose of 20 μmol/kg with irradiation 5 h postinjection at 150 J/cm2 and 150 mW/cm2, had significant efficacy (P < 0.0001) in treating neoplasms of moderate size (40 ± 14 mm3) and also had significant efficacy (P < 0.0001) in treating larger neoplasms (147 ± 65 mm3). The PDT efficacy was correlated with the time interval between PCI‐0123 administration and light exposure. A 100% cure rate was achieved when photoirradiation took place 3 h postinjection compared to 50% for 5 h using 10 μmol/kg and 150 J/cm2 at 150 mW/cm2. The PDT efficacy was attributable to the selective uptakehetention of the texaphyrin photosensitizer in addition to the depth of light penetration achievable at the 732 nm laser irradiation.
Early Diagnosis of Leptospirosis by Immunoglobulin M Immunoblot Testing
Authors: Doungchawee Galayanee , Kositanont Uraiwan , Niwetpathomwat Anuchai , Inwisai Tasanee , Sagarasaeranee Plyyonk , Haake David A. 
Published: January 2008

ABSTRACT
There is an urgent need for the development of serodiagnostic approaches with improved sensitivity for patients with acute leptospirosis. Immunoblots were performed on 188 sera collected from 74 patients with laboratory-confirmed early leptospiral infection to detect immunoglobulin M (IgM) antibodies to antigens pooled from 10 leptospiral strains prevalent in Thailand. Sera from patients with other febrile diseases served as controls. IgM reactivity to seven distinct antigens, with apparent molecular masses of 14 to 18, 19 to 23, 24 to 30, 32, 35/36, 37, and 41/42 kDa, was observed. The low-molecular-mass 14- to 18-kDa band was the most frequently detected antigen, being recognized in sera from 82.4% of patients during the first 3 days after the onset of symptoms. We evaluated the accuracy of the IgM immunoblot (IgM-IB) test by using reactivity to the 14- to 18-kDa band and/or at least two bands among the 19- to 23-, 24- to 30-, 32-, 35/36-, 37-, and 41/42-kDa antigens as the diagnostic criterion. The sensitivities of the IgM-IB test and the microscopic agglutination test (MAT) were 88.2% and 2.0%, respectively, with sera from patients 1 to 3 days after the onset of symptoms. In contrast, the IgM-IB test was positive with only 2/48 (4.2%) sera from patients with other febrile illnesses. The high sensitivity and specificity of the IgM-IB test for acute leptospirosis would provide greatly improved diagnostic accuracy for identification of patients who would benefit from early antibiotic intervention. In addition, the antigens identified by the IgM-IB test may serve as components of a rapid, accurate, point-of-care diagnostic test for early leptospirosis.
Immunological Responses and Long-Term Treatment Interruption after Human Immunodeficiency Virus Type 1 (HIV-1) Lipopeptide Immunization of HIV-1-Infected Patients: the LIPTHERA Study
Authors: Pialoux Gilles , Quercia Romina P. , Gahery Hanne , Daniel Nathalie , Slama Laurence , Girard Pierre-Marie , Bonnard Philippe , Rozenbaum Willy , Schneider Véronique , Salmon Dominique , Guillet Jean-Gérard 
Published: January 2008

ABSTRACTWe studied the time course of immunological and virological markers after highly active antiretroviral therapy (HAART) interruption in chronically human immunodeficiency virus type 1 (HIV-1)-infected patients immunized with an HIV lipopeptide preparation. In a prospective open pilot study, 24 HIV-1-infected HAART-treated patients with undetectable plasma viral loads (pVLs) and CD4+T-cell counts above 350/mm3were immunized at weeks 0, 3, and 6 with a candidate vaccine consisting of six HIV lipopeptides. At week 24, patients with pVLs of <1.7 log10copies/ml were invited to stop taking HAART. Antiretroviral therapy was resumed if the pVL rose above 4.47 log10copies/ml and/or if the CD4+cell count fell below 250/mm3. Immunological and virologic parameters were studied before and after HAART interruption. The median baseline and nadir CD4+cell counts were 482 (interquartile range [IQR], 195 to 826) and 313 (IQR, 1 to 481)/mm3, respectively. New specific CD8+cell responses to HIV-1 epitopes were detected after immunization in 13 (57%) of 23 assessable patients. Twenty-one patients were evaluated 96 weeks after HAART interruption. The median time to pVL rebound was 4 weeks (IQR, 2 to 6), and the median peak pVL was 4.26 (IQR, 3 to 5) log10copies/ml. Thirteen of these 21 patients resumed HAART a median of 60 weeks after immunization (IQR, 9.2 to 68.4 weeks), when the median pVL was 4.8 (IQR, 2.9 to 5.7) log10copies/ml and the median CD4+cell count was 551 (IQR, 156 to 778)/mm3. Eight patients were still off therapy at 96 weeks, with a median pVL of 4 (IQR, 1.7 to 4.6) log10copies/ml and a median CD4+cell count of 412 (IQR, 299 to 832)/mm3. No clinical disease progression had occurred. Despite the lack of a control arm, these findings warrant a randomized study of therapeutic vaccination with HIV lipopeptides followed by long-term HAART interruption in AIDS-free chronically infected patients.