bluuebunny/crossref_metadata_2025_split huggingface dataset:
GroESL proteins facilitate binding of externally added inducer by luxR protein‐containing E. coli cells
Authors: Adar Y. Y. , Ulitzur S. 
Published: May 2005

AbstracthtpR− (rpoH, σ32 minus) strain of E. coli harbouring the whole lux system of Vibrio fischeri is very dim. We have recently shown that GroESL proteins fully recover the expression of the lux system in this strain. This work has been undertaken to study our assumption that the GroESL proteins stabilize the LuxR protein, thus enhancing the formation of LuxR–Inducer complex. E. coli htpR− cells harbouring the luxR gene were unable to bind extracellularly added inducer, while late logarithmically growing htpR+ strain bound small quantities of the inducer. Reduction in the nutrient content of the growth medium resulted in a large increase in the capability of these cells to bind the inducer. htpR+ or htpR− E. coli strains harbouring both the luxR and the groESL genes bound large quantities of the inducer. The molecular and ecological significance of these results is discussed.
Mechanisms of inhibition of chemiluminescence in the oxidation of luminol by sodium hypochlorite
Authors: Arnhold J. , Mueller S. , Arnold K. , Sonntag K. 
Published: May 2005

AbstractTwo different mechanisms of inhibition of chemiluminescence in the oxidation of luminol by sodium hypochlorite were found. Most substances investigated in these experiments acted by scavenging NaOCI. This mechanism was independent of the concentration of hydrogen peroxide and the incubation time between luminol and inhibitors. The most potent inhibitors were substances containing SH groups. Compounds with amino groups as a target for HOCI/OCI− to yield chloramines were much less effective inhibitors. Another mechanism of inhibition was found for catalase. It depended on the presence of hydrogen peroxide in the incubation medium and the incubation time between luminol and catalase. The enzyme inhibited the luminescence by removing H2O2 at molar concentrations much smaller than those found for all other inhibitors. Our results confirm the present models of the mechanism of generation of luminescence in luminol oxidation.
Improvements to enhanced horseradish peroxidase detection sensitivity
Authors: Motsenbocker M. A. , Kondo K. 
Published: May 2005

AbstractAt very low horseradish peroxidase (HRP) concentrations, the enhanced chemiluminescence reaction is often characterized by a lag time between initiation of the reaction and beginning of light output. In this study, four treatments of luminol solution were examined in an effort to remove the lag time and to improve chemiluminescence light output. Addition of ammonium persulphate stimulated light output more than tenfold. Ultraviolet irradiation and photoactive dye pretreatment of luminol solution both increased light output fourfold. Luminol purity was the most important factor affecting detection sensitivity. Recrystallization of luminol from base improved the detection limit 13‐fold although there was an improvement in the detection limit from 13 attomoles per millilitre to 5 attomoles per millilitre with highly purified luminol when photoactive dye pretreatment was utilized. The results are consistent with a simple interference mechanism whereby enhancer radicals produced by the enzyme are preferentially quenched by contaminants present in the luminol, in the enhancer and in the solvent used to dissolve the enhancer. Consumption of these interferences prior to light emission results in a lag time and a less favourable HRP detection limit.
Apyrase immobilized on paramagnetic beads used to improve detection limits in bioluminometric ATP monitoring
Authors: Nyrén Pål 
Published: May 2005

AbstractA novel technique that is useful for the control of the luminescence output in a bioluminometric assay has been developed. The method relies on the immobilization on paramagnetic beads of an enzyme that is capable of catalysing the hydrolysis or oxidation of the substrate for the luminescence reaction. This technique has been used for control of the level of ATP in the luciferin‐luciferase system. Biotinylated apyrase was bound to streptavidin coated paramagnetic beads and added to the assay mixture. The level of ATP in the reaction mixture was then conveniently controlled using an external magnet. The possible use of this approach in other systems, such as the bacterial luciferase–oxidoreductase is discussed.
Commercially available luminometers and imaging devices for low‐light level measurements and kits and reagents utilizing bioluminescence or chemiluminescence: Survey update 2
Authors: Stanley Philip E. 
Published: May 2005

AbstractThis survey was completed in December 1993 and includes products not covered in the luminometer survey (Jan 1992: Stanley PE, J Biolumin Chemilumin 1992; 7:77–108 and 7:157–69), kits and reagent survey (Nov 1992: Stanley PE, J Biolumin Chemilumin 1993; 8:51–63), update 1 (June 1993, luminometers, kits and reagents, Stanley PE, J Biolumin Chemilumin 1993; 8:237–40). Technical details are provided together with company address and contact information.
Photon emission from chemically perturbed yeast cells
Authors: Rajfur Zenon 
Published: May 2005

AbstractPhoton emission (PE) from yeast cells Saccharomyces cerevisiae strain SP‐4 in normal conditions and in conditions perturbed by the addition of formaldehyde was investigated using single‐photon counting equipment. PE from yeast cells, growing in a standard nutrient medium (YPG) then centrifuged and resuspended in a phosphate buffer (pH = 6.5), was measured in the presence of oxygen or argon. The solution of formaldehyde (2%) was injected into the sample. The intensity of PE increased and reached a maximum, then slowly decreased to a level which was higher than the PE level without the perturbing factor. The kinetics of PE was found to be strongly dependent upon the presence of oxygen. The model of formation and recombination of free radicals was tested. The results indicate that PE can arise during the recombination reactions of free radicals like R⋅ + R⋅, RO⋅ + RO⋅, RO⋅2 + RO which are formed in the enzymatic oxidative reactions.
Imaging of chemiluminescent reactions in mesoscale silicon‐glass microstructures
Authors: Kricka Larry J. , Ji Xiaoying , Nozaki Osamu , Wilding Peter 
Published: May 2005

AbstractChemiluminescent reactions in mesoscale analytical structures (chips) containing micrometer‐sized interconnecting channels and chambers (pL‐nL total volume) were imaged. The chips were fabricated by bonding Pyrex glass to etched pieces of silicon using a high‐temperature diffusive bonding technique. In initial experiments light emission from an enhanced chemiluminescent horseradish peroxidase reaction and from a peroxyoxalate reaction contained in straight channels (300 μm wide × 20μ deep; volume 70.2 nL) and open chambers (812 μm wide, 400 μm deep, 5.2 mm long) linked by channels (100μm wide, 20 μm deep) to an exit and entry port were studied using a specially modified microplate holder and an Amerlite microplate luminometer. Light emission from more complex structures (two chambers interconnected by a branching channel 100 μm wide, 20 μm deep) filled with a solution containing alkaline phosphatase, Emerald, and CSPDTM was imaged using a Photometrics Star 1 CCD camera. Detailed investigation of the detection and spatial resolution of the signal was performed on a Berthold Luminograph LB 980 using both the enhanced chemiluminescent horseradish peroxidase reaction and a peroxyoxalate reaction. We successfully resolved light emission from silicon structures with dimensions 100 μm wide and 20 μm deep. These simple silicon structures served as models for more complex designs that will be used for simultaneous multi‐analyte assays in which an imaging system resolves and quantitates light emission from different locations on a silicon‐glass analytical device.
Imaging reactive oxygen species in asthma
Authors: Vachier Isabelle , Doucen Christian Le , Loubatière Jacques , Damon Marcelle , Térouanne Béatrice , Nicolas Jean‐Claude , Chanez Pascal , Godard Philippe 
Published: May 2005

AbstractInflammatory processes in asthma are characterized by an infiltration of inflammatory cells including mononuclear phagocytes. It has been observed that mononuclear phagocytes, alveolar macrophages and blood monocytes, release higher quantities of reactive oxygen species in asthmatic patients than in healthy subjects. Chemiluminescence assays were developed to measure the superoxide anion and the other reactive oxygen species. The chemiluminescence response was first analysed with a luminometer, which made it possible to study cells in suspension before and after PMA‐stimulation. Secondly a video‐imaging camera was used in experiments on adherent cells before and after stimulation with PMA and/or specific stimulus IgE/anti‐IgE. Both techniques showed that human alveolar macrophages, blood monocytes, PMN and lymphocytes were spontaneously primed in vivo and were more easily stimulated in asthma. Analysis of adherent cells in vitro may provide give information on the physiological condition of adherent cells in vivo.
Targeting of aequorin for calcium monitoring in intracellular compartments
Authors: Brini Marisa , Pasti Lucia , Bastianutto Carlo , Murgia Marta , Pozzan Tullio , Rizzuto Rosario 
Published: May 2005

AbstractWe have recently developed a new method for monitoring Ca2+ concentrations in defined cell compartments. The cDNA encoding the Ca2+‐sensitive photoprotein aequorin has been modified in order to include specific targeting sequences and expressed in eukaryotic cells; the recombinant protein, specifically located inside the cells, has allowed the direct study of mitochondrial and nuclear Ca2+ concentrations in living cells. The principles, and the application, of this new methodology are discussed in this article.
Chimeric receptors as a tool for luminescent measurement of biological activities of steroid hormones
Authors: Jausons‐Loffreda N. , Balaguer P. , Roux S. , Fuentes M. , Pons M. , Nicolas J.‐C. , Gelmini S. , Pazzagli M. 
Published: May 2005

AbstractSome applications of chimeric cellular models are presented to study the biological activities of steroid hormones. We have used several chimeric constructs encoding the DNA binding domain of Gal4 yeast protein fused to the hormone binding domain of various steroid receptors (MR, PR, GR and ER). Interactions of these chimeric receptors with a 17‐mer DNA sequence, specific for Gal‐4, control expression of the firefly luciferase as a reporter gene. Stable transfected cell lines expressing the firefly luciferase under the control of different steroids were established and an efficient and easy sub‐cloning was allowed with the help of an imaging system using a single‐photon‐counting camera. In the cell lines obtained, the bioluminescent response can be easily measured and thus used to measure specific biological activities of steroid agonists or antagonists. We observed that the responses are effector‐concentration‐dependent and their biological activities will be compared to those of native receptors.
Measurement of endogenous and TNFα‐mediated H2O2 production in supernatants of SK‐N‐SH neuroblastoma cells with an enhanced chemiluminescence assay
Authors: Carmine T. C. , Bruchelt G. , Hahn T. , Niethammer D. 
Published: May 2005

AbstractA sensitive peroxidase‐dependent luminol‐enhanced chemiluminescence (ECL) assay for determination of hydrogen peroxide (H2O2) generation by tumour cells was established. This test system allows determination of H2O2 in concentrations as low as 25 pmol (50nmol/L) and yields results which are comparable to those obtained using a less sensitive photometric method and a previously described scopoletin flurorescence assay. After 3h incubation time 104SK‐N‐SH neuroblastoma cells released 60° 5 pmol H2O2 in the supernatant and this level was significantly (p<0.025) increased by about 70% in the presence of 5pmol (100 ng/mL) recombinant tumour necrosis factor α (TNFα). In contrast, H2O2 production was slightly reduced by TNFα at a very low concentration of 0.5 fmol (0.01 ng/mL).
Comparison of MTT and ATP‐based assays for the measurement of viable cell number
Authors: Petty Russell D. , Sutherland Lesley A. , Hunter Elizabeth M. , Cree Ian A. 
Published: May 2005

AbstractCell viability assays are widely used to assess the effect of chemotherapeutic drugs and other agents on cell lines and have shown promise for the prediction of tumour chemosensitivity. In this study we have compared two viability assays using Daudi and CCRF‐CEM cell lines over a range of 1500–100,000 cells/well of a microplate. The ATP assay was able to detect the lower limit of 1563 cells/well with luminescence values at least 100× background readings, while the MTT assay could not detect less than 25,000 cells/well above background readings. The ATP assay also showed better reproducibility and sensitivity when cells were grown in microtitre plates over several days, and is particularly useful for the measurement of viability with low cell numbers.
Enhanced chemiluminescent sandwich enzyme immunoassay for hen egg lysozyme
Authors: Rauch Pavel , Poplstein Martin , Hochel Igor , Fukal Ladislav , Ferri Elida , Abagnato Carlo Alberto , Girotti Stefano , Roda Aldo 
Published: May 2005

AbstractA sensitive chemiluminescent sandwich‐type enzyme immunoassay for hen egg lysozyme was developed. The assay was performed on polystyrene microtitre plates using immobilized specific polyclonal rabbit antibody against lysozyme, a peroxidase conjugate and the H2O2/luminol‐enhanced chemiluminescence detection reagent. The chemiluminescent signal was detected using either a microplate luminometer, or photographic film in a camera luminometer. The detection limit for lysozyme was 0.3 ng/mL, and this was three times lower than that obtained using a colorimetric method with H2O2 and o‐phenylendiamine as substrates. Recovery of the assay was 97–112% and the relative standard deviation ranged from 3.6% to 10.3%. The immunoassay overcame interference from the food sample matrix when lysozyme, used as a bacteriostatic agent, was measured.
4‐phenylylboronic acid: A new type of enhancer for the horseradish peroxidase catalysed chemiluminescent oxidation of luminol
Authors: Kricka Larry J. , Ji Xiaoying 
Published: May 2005

Abstract4‐Phenylylboronic acid enhances the light emission from the horseradish peroxidase catalysed oxidation of luminol by hydrogen peroxide. Optimization studies showed that the greatest enhancement was obtained using micromolar concentrations of the new enhancer. The largest degree of enhancement was found with the basic isoenzyme of horseradish peroxidase (Type VIA), and lesser degrees of enhancement were obtained with Type VII and Type IX horseradish peroxidase. The enhancer was also effective in the peroxidase catalysed oxidation of isoluminol by peroxide.
Luminol‐enhanced chemiluminescence after reaction of hydroperoxides with opsonized zymosan
Authors: Heinle Helmut , El Dessouki Jasmin 
Published: May 2005

AbstractLuminol‐enhanced chemiluminescence (LEC) is very sensitive in detecting free radicals but relatively insensitive for hydroperoxides (hydrogen peroxide, tert‐butyl hydroperoxide). However, in the presence of opsonized zymosan (often used for stimulation of phagocytic cells) hydroperoxides also induce LEC, suggesting that free radicals are produced under these conditions. Therefore careful interpretation with respect to the nature of the reactive species is necessary when LEC is used for characterization of zymosan‐induced phagocytosis. We studied the properties of zymosan‐induced LEC under different test conditions and with various inhibitors. Typical radical scavengers, e.g. nordihydroguaiaretic acid and superoxide dismutase, are strong inhibitors, indicating the importance of the superoxide anion. This system is useful for drug testing with respect to antioxidative or radical scavenging activity.
The roles of the two highly unstable components F and P involved in the bioluminescence of euphausiid shrimps
Authors: Shimomura Osamu 
Published: May 2005

AbstractBioluminescence of euphausiids takes place when a fluorescent tetrapyrrole F and a highly unstable protein P react in the presence of oxygen. A previous study on the euphausiid Meganyctiphanes norvegica indicated that F acts as a catalyst and P is consumed in the luminescence reaction, differing from the luminescence system of dinoflagellates in which a tetrapyrrole luciferin, nearly identical to F, is enzymatically oxidized in the presence of dinoflagellate luciferase. In the present study, P was extracted from Euphausia pacifica as well as from M. norvegica, then purified separately by affinity chromatography on a column of biliverdin–Sepharose 4B, completing the whole process in less than 5h. The samples of P obtained from both species had a molecular weight of 600,000, a purity of about 80%, and a specific activity 50–100 times greater than that previously found. The activity of P rapidly decreased in solutions, even at 0°C, and the inactivation of P derived from M. norvegica was more than four times faster than that derived from E. pacifica. The kinetics of the luminescence reaction was investigated with F and P whose concentrations were systematically varied. The reaction was characteristically slow and involved two different reaction rates; the turnover number at 0°C was 30/h for the initial 20 min and 20/h after the initial 1 h. The total light emitted in a 50‐h period indicated that the bioluminescence quantum yield of F was about 0.6 at 0°C, and P recycled many times in the luminescence reaction. Thus, the present results conclusively show that F is a luciferin and P is a luciferase of an unusually slow‐working type, contrary to early report.
Chemiluminescent immunoassay (CLIA) for the detection of brucellosis and tularaemia antigens
Authors: Vidžiūnaité R. , Mikulskis P. , Kulys J. 
Published: May 2005

AbstractThe detection of brucellosis and tularaemia infection agents is of particular interest for medical practice. The possibility of using enhanced chemiluminescence reactions for the determination of these agents is studied in this work.Light intensity depends on both the conjugate concentration used and the conditions at which the adsorption was performed. Optimal conditions for these test‐systems were: ∼ 20 μg/mL of Ig and 200 μg/mL (titre 1:20) of conjugate. As is seen from the chemiluminescent and spectrophotometric results the lowest determined concentrations are 10 and 30 ng/mL (for brucellosis) and 1 and 5 ng/mL (for tularaemia), respectively. Calibration curves in the antigen concentrations ranging from 10 to 2500 ng/mL (for brucellosis) and from 1 to 500 ng/mL (for tularaemia) are observed. Optical density depends linearly on the logarithm of the antigen concentration from 30 to 5000 ng/mL (for brucellosis) and from 5 to 250 ng/mL (for tularaemia).The results obtained permit the conclusion that the chemiluminescence method can be used in enzyme immunoanalysis for brucellosis and tularaemia antigens.
A blue chemiluminescence in the reaction of umbelliferone with hypochlorite
Authors: Slawinska Danuta , Slawinski Janusz 
Published: May 2005

AbstractA strongly fluorescing 7‐hydroxycoumarin (umbelliferone, U) oxidized in dilute (10 μmol/L‐0, 1 mol/L) aqueous solution with CIO− or CIO− + H2O2 (but not with H2O2 alone) produces a strong chemiluminescence (CL). Light emission kinetics depends on the pH of solution (4.0–10.5) and the reaction has a low activation energy Ea = 31 ± 2 kJ/mol (285–310 K). The spectrum covers the fluorescence of umbelliferone (400–550 nm, λmax 460nm). No red emission typical of 1Δg, 1Σ+g (O2)2 is observed either in the umbelliferone +CIO− or the umbelliferone +CIO− + H2O2 solution. The possible mechanism of CL and concomitant degradative oxidation of umbelliferone is discussed.
Evaluation of Jansson's method for resolving overlapped gas chromatographic peaks
Authors: Crilly Paul Benjamin 
Published: May 2005

AbstractIn a previous paper,1 Jansson's method was used to deconvolve overlapped gas chromatographic peaks. It was found that this method gave improved performance over conventional techniques such as perpendicular drop and shoulder quantitation.2,3 This paper will present the results of a comprehensive test of Jansson's method using several sample mixtures. These results will be compared to what can be obtained by using shoulder quantitation, perpendicular drop or an instrument with a longer column. A relatively large number of tests will be performed for each of the four mentioned methods of peak resolution, so there will be a reasonable statistical basis for the goodness of Jansson's method to resolve fused gas chromatographic peaks for a given set of instrument conditions. A brief review of Jansson's method and the modeling of a gas chromatographic process will also be presented.
Partial least squares analysis with cross‐validation for the two‐class problem: A Monte Carlo study
Authors: Ståhle Lars , Wold Svante 
Published: May 2005

AbstractA method for statistical analysis of two independent samples with respect to difference in location is investigated. The method uses the partial least squares projections to latent structures (PLS) with cross‐validation. The relation to classical methods is discussed and a Monte Carlo study is performed to describe how the distribution of the test‐statistic employed depends on the number of objects, the number of variables, the percentage variance explained by the first PLS‐component and the percentage missing values. Polynomial approximations for the dependency of the 50 per cent and the 5 per cent levels of the test‐statistic on these factors are given. The polynomial for the 50 per cent level is complicated, involving several first‐, second‐ and third‐degree terms, whereas the polynomial for the 5 per cent level is dependent only on the number of objects and the size of the first component. A separate Monte Carlo experiment indicates that a moderate difference in sample size does not affect the distribution of the test‐statistic. The multi‐sample location problem is also studied and the effect of increasing the number of samples on the test‐statistic is shown in simulations.
An evaluation of SIMCA. Part 2 — classification of pyrolysis mass spectra of pseudomonas and serratia bacteria by pattern recognition using the SIMCA classifier
Authors: Dröge J. B. M. , Rinsma W. J. , Van 'T Klooster H. A. , Tas A. C. , Van Der Greef J. 
Published: May 2005

AbstractAs part of a critical evaluation of the pattern recognition method SIMCA, three data sets containing pyrolysis mass spectra from bacteria were analysed using the SIMCA classifier. Each set consisted of two classes, Pseudomonas and Serratia bacteria, each class containing ten mass spectra and each mass spectrum having 285 spectral features.The results indicate that for these py‐MS data sets, with low object/feature ratio, the SIMCA classifier produces satisfactory results at the first classification level. At the second level, however, the classification results are not reliable, even after deleting outliers. A comparison of the cross‐validation method and Malinowski's indicator function for the determination of the number of significant principal components showed that the cross‐validation method is less stable and therefore less reliable than the indicator function.