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At least 991 records · Page 55Linked to original sources
PubMed2003

Inhibition study of adenosine deaminase by caffeine using spectroscopy and isothermal titration calorimetry.

Kinetic and thermodynamic studies were made on the effect of caffeine on the activity of adenosine deaminase in 50 mM sodium phosphate buffer, pH 7.5, using UV spectrophotometry and isothermal titration calorimetry (ITC). An uncompetitive inhibition was observed for caffeine. A graphical fitting method was used for determination of binding constant and enthalpy of inhibitor binding by using isothermal titration microcalorimetry data. The dissociation-binding constant is equal to 350 microM by the microcalorimetry method, which agrees well with the value of 342 microM for the inhibition constant that was obtained from the spectroscopy method. Positive dependence of caffeine binding on temperature indicates a hydrophobic interaction.

Adenosine Deaminase↗
PubMed1992

[The use of tapioca as coverage in viral titration].

Virus titration is an important step required on viral vaccines quality control. "Plaque assay", which employs several types of overlay media, is usually used on viral titrations. In this paper we describe the use of Tapioca as an overlay media. Firstly, the toxicity of Tapioca was tested on Vero cells inoculated or not with the Yellow Fever virus (YF) 17DD vaccine strain. Secondly, different batches of the 17DD virus using the Tapioca and Karaya gum as the overlay on Vero cells were tested when higher titres were obtained using Tapioca. Tapioca was also shown to be a suitable overlay to be used in thermostability and plaque reduction neutralization tests. Other systems could benefit from the use of Tapioca as an overlay, since it was possible to titer Measles virus in Vero cells. Tapioca is a cheap Brazilian product, is locally available, easy to use, and reliable. Its use is suggested.

Animals↗
PubMed2004

Coupling pH-stat and DO-stat titration to monitor degradation of organic substrates.

A combined titration methodology at constant pH and dissolved oxygen concentration to monitor the degradation of organics as carbon dioxide evolution rate (CER) and oxygen uptake rate (OUR) is presented. Equations necessary to assess CER from alkali titration rates and the instrument used to test the technique are described. Experiments were performed on samples of activated sludge from a domestic wastewater treatment plant using glucose and ethanol as substrates. OUR and CER were calculated for both substrates, as well as the respiratory quotient RQ = CER/OUR and biomass to substrate yields coefficients. RQ data for ethanol compared better with corresponding stoichiometric values than those for glucose.

Biodegradation, Environmental↗
PubMed2004

Cetylpyridinium tetrachlorozincate as standard for tenside titration. Analytical methods with 1,3-dibromo-5,5-dimethylhydantoin (DBH) in respect to environmental and economical concern, part 19.

The determination of the cationic active disinfectants benzalkonium chloride, benzethonium chloride, cetrimide, and cetylpyridinium chloride according to PH. EUR. 2002 resp. supplement 4.3/2003 can be improved using the DBH-method. By application of column extraction the iodide determination can be performed in the organic layer by visual indication. However, titration in aqueous solution with sodium dodecyl sulphate as titrant and methyl orange resp. bromophenol blue as indicator can be performed more simple. Cetylpyridinium tetrachlorozincate is recommended as a standard for tenside titration.

Azo Compounds↗
PubMedDate not supplied

[Sensitivity of methods of titration of the vaccine strain of porcine fever virus].

Methods of titration of the CS vaccine strain of classical swine fever virus were compared in vitro and vivo. The titration in the TL and PK-15 cell culture without cytopathic effect is based on the detection of virus antigen by labeled antibodies. The infection intensity in the cell culture virtually correlated with the antigenic and immunogenic activity of dry vaccine used for swine.

Animals↗
PubMed1975

[Use of coulometric titration for elucidating the mechanism of the oxidation of 6-APA alkaline breakdown products by halogens].

Penaldinic acid and penicillamine were formed on alkali decomposition (1 N NaOH) of 6-APA for 20 minutes at room temperature, penicillamine being completely oxidized to disulphide by the air oxygen. Coulometric titration of the alkali decomposition products showed that generated chlorine in 0.5 N HCl solution or bromine in a week acid solution of KBr oxidized them with participation of 7 electrones. Generated iodine did not practically oxidize the 6-APA decomposition products during the coulometric titration.

Bromine↗
PubMedDate not supplied

Determination of infectious bursal disease virus titration and neutralization endpoints using fluorogenic staining.

An automated method for determining infectious bursal disease virus (IBDV) titration and neutralization endpoints is described. The method employs the fluorogenic ester carboxyfluorescein-diacetate (CFDA) to stain cell monolayers in 96-well plates and a fluorescence-concentration analyzer. Titration results are compared with immunofluorescence and plaque assay titers. Virus-neutralization endpoint determination is objective, and the endpoints of replicate tests were equivalent or within one dilution of variability. Tests can be automatically screened as any percentage of a positive control or any standard deviation from a negative control.

Animals↗
PubMed1990

[Semiautomatic potentiometric titration of gastric juice].

Using commercial equipment manufactured in this country, the authors have assembled a unit for semiautomatic potentiometric titration and developed a method for such titration, permitting a rapid determination of free and bound HCl and the total acidity of the gastric juice. The equipment and method are recommended for wide use at laboratories of therapeutic institutions, of biologic factories manufacturing medicinal commercial gastric juice, and of research institutes.

Gastric Acidity Determination↗
PubMedDate not supplied

[2-site competitive immunoenzyme analysis based on monoclonal antibodies for the detection and titration of antihemagglutinating measles antibodies].

Using monoclonal antibodies (MCA) to measles virus (strain Leningrad-16) hemagglutinin, a competitive enzyme immunoassay (cEIA) was developed for the detection and titration of antihemagglutinating antibodies in human sera. Serum samples from children, collected in measles foci, were tested in cEIA, SP-EIA, HI, and PHA tests. The results evidence a high correlation of antihemagglutinin titres in cEIA and HI tests, the correlation coefficient of cEIA and PHA being 97.7%. The cEIA based on MCA to measles virus hemagglutinin is highly specific for the detection and titration of measles antihemagglutinins, it does not involve the use of simian erythrocytes. A significant advantage of this test system consists in the possibility of using unpurified antigen prepared from the infected cell lysate.

Antibodies, Monoclonal↗
PubMed1991

The mechanism of ATP hydrolysis by smooth muscle myosin and subfragments using steady state titration and 18O exchange.

The mechanisms of increases in the ATPase rates of smooth muscle acto-myosin, acto-heavy meromyosin (HMM) and acto-subfragment 1 (S1) were investigated using steady state titration and 18O exchange. Phosphorylation increased the phosphate release rates both from acto-myosin and acto-HMM. Steady state titration at high enzyme concentrations and 18O exchange at substoichiometric ATP concentrations showed that gizzard myosin was kinetically homogeneous, whereas HMM and S1 prepared by various published methods were heterogeneous. At high ATP concentrations, a small population of HMM and S1 hydrolyzed ATP with a low amount of oxygen exchange.

Adenosine Triphosphate↗
PubMed1977

[Calcium containing antacids and acid rebound. Testing with intragastric titration and extragastric measurement of pH].

Intragastric titration with the pH being measured extragastrically is a method both precise and highly qualified for clinical trials of antacids and quantitative analysis of gastric secretion. In 12 patients with duodenal ulcer, acid secretion was measured by intragastric titration both before and after adminstration of a Ca-Mg-containing antacid. Acid secretion was found to be significantly lower after administration of the Ca-Mg-containing antacid, a so-called acid rebound could not be demonstrated.

Adult↗
PubMed1975

Involvement of tyrosine and lysine residues of retinol-binding protein in the interaction between retinol and retinol-binding protein and between retinol-binding protein and prealbumin. Acetylation with N-acetylimidazole and alkaline titration.

The behavior of holo-retinol-binding protein (RBP) from human plasma at alkaline pH was examined by absorption and circular dichroism measurements. Between pH 7.5 and 11.7 the ionization of the phenolic hydroxyl groups is reversible. However, there is a gradual irreversible loss of retinol as the pH is raised. After 4 hours at pH 11.7, 13 percent of retinol is lost from retinol-RBP. Alkaline titration of apo-RBP was time-independent and reversible between pH 7.5 and 11.7. The titration data of the phenolic hydroxyl groups in apo-RBP could be fitted with a single theoretical ionization curve of 8.6 phenolic groups having an apparent pK of 11. Acetylation of retinol-RBP with 10-fold molar excess of N-acetylimidazole over tyrosine resulted in the acetylation of all lysine residues and in the acetylation of 0.9 to 1.3 tyrosyl residues per molecule (out of eight). Acetylation of retinol-RBP, APO-RBP, and retinol-RBP-prealbumin complex with 50-fold molar excess of N-acetylimidazole resulted, again, with all of the lysine residues being acetylated and between 1.8 and 2.8 tyrosyl residues per molecule being acetylated. The acetylation did not affect the interaction between retinol and RBP. However, acetylation disrupted the normal binding between retinol-RBP and prealbumin. Deacetylation of tyrosyl residues with hydroxylamine failed to restore the normal binding of retinol-RBP to prealbumin. This excludes the acetylated tyrosyl-residues from being involved in the binding between the two proteins.

Acetates↗
PubMed1975

Nuclear magnetic resonance titration curves of histidine ring protons. The effect of temperature on ribonuclease A.

The ionization constants of 3 of the histidine residues of ribonuclease A have beenobtained at 5 temperatures from the nuclear magnetic resonance titration curves of the imidazole C2 proton resonances. Thermodynamic parameters derived from the ionization constants indicate that histidine residues 105 and 119 are fairly well exposed to solvent, while histidine residue 12 is in a somewhat more restricted environment. Measurements of the low pH inflection present in the titration curve of histidine-12 yield a large negative entropy value, indicating that the group givine rise to this inflection is also buried.

Calorimetry↗
PubMed1989

[On the titration of vaccines against pleuropneumonia. A new approach to an old problem, preliminary studies].

A new technique is proposed for the titration of live vaccines against contagious bovine pleuropneumonia (CBPP). Presently, the one most widely used, combines a set of tenfold dilutions with the seeding of five tubes with samples taken from each of these latter. This technique is not very accurate or it requires a great number of tubes to increase its accuracy. The new technique starts with the same tenfold dilutions but after a relevant dilution, samples of 100 microliters are put into the eight wells of the first column of a microtitration plate and then with "glucose" medium. After a 6 to 9 days incubation time, the growth can be recorded by an indicator change of color. This technique is much faster and seems to be more precise. Furthermore the eight parallel titrations enable the results to be expressed by means and comparison of results can be statistically meaningful.

Animals↗
PubMed1989

Coulometric titration of total flavonoids in Sophora japonica L.

A method for the determination of total flavonoids in Sophora japonica L. by coulometric titration was developed. The titration was carried out in a mixture of 1 mol/L KBr--2 mol/L HCl (1:1) and bromine was generated at the anode, rutin reacted with two moles of bromine with an n value of 4. The advantages of this method are simple and rapid, it can be used to analyze small amount of sample.

Drugs, Chinese Herbal↗
PubMed1986

A comparison of titration methods for live avian encephalomyelitis virus vaccines.

Factors associated with the indirect fluorescent antibody test used for the titration of avian encephalomyelitis virus (AEV) in chick embryo brain cell cultures were examined for their influence on virus replication. It was found that virus should be inoculated onto semi-confluent cell cultures and adsorbed for two hours at room temperature. The cells should then be examined for fluorescence after five days' incubation. Using these conditions, the cell culture assay was compared with the embryo and chick assays for its ability to estimate the virus content of live commercial AEV vaccines. In most cases titres obtained by the chick assay were slightly, but not significantly, higher than those obtained in the cell culture assay, although the reliability of the chick assay was, at times, questionable. In all cases titres obtained in the embryo assay were low. It is recommended that the cell culture assay be adopted as the method of choice for titrating AEV vaccines because it is rapid, reproducible, specific and greatly reduces the requirement for experimental animals.

Animals↗
PubMed1988

[Titration curves (ph gradient electrophoresis) of SHV-1 and SHV-2 beta-lactamases and a new type].

The molecular structures of the SHV-1 (p 453) and SHV-2 (pBP 60-1) beta-lactamases and of a new enzyme, a SHV-2 like extended broad-spectrum beta-lactamase (86-4), were compared by analysis of their titration curves (pH gradient electrophoresis). The titration curves of SHV-1 and SHV-2, which have the same isoelectric points (pI = 7.7). were completely superimposable for the whole of the pH gradient (pH 3.5-10), indicating a close homology between the two proteins, with perhaps the substitution of several amino acids by ones having the same charge. The curves of SHV-1 (pI = 7.7) and the new SHV-2-like enzyme (pI = 6.98) indicated that a basic residue in SHV-1 has been replaced by an acidic residue in the new SHV-2-like enzyme. These results show that, like SHV-2, the new beta-lactamase is a variant of SHV-1, and that the structural differences are probably limited to a very small number of amino acid residues. Nevertheless, this new beta-lactamase (SHV-3) may have arisen directly from SHV-1, indirectly via SHV-2, or even from another beta-lactamase.

Electrophoresis, Polyacrylamide Gel↗
PubMed1987

[The mouse paw edema test for titrating Shigella toxin and antitoxin and for determining the safety of the anatoxin].

The method for the titration of Shigella dysenteriae I neurotoxin, toxoid prepared from this toxin and different antitoxic preparations in the mouse paw edema test has been developed. The quantitative determination of antitoxin is based on the neutralization test. The conditions of titration (the dilutions of the neurotoxin and the neutralization doses of the antitoxin), as well as criteria for the evaluation of the positive or negative results, have been established.

Animals↗