1,721,003 research outputs found
Effetti di ioni metallici fortemente inquinanti sull'attività enzimatica: indagini microcalorimetriche
No full textAmperometric characterization of diaphorase from Bacillus stearothermophilus immobilized on different membrane surface
No full textMicrocalorimetric study on the system adenosine-5'-triphosphate/sodium potassium adenosine-5'-triphosphatase. Part 2: a new calorimetric method for the 5' ATP assay in standards and real samples
No full textMicrocalorimetric study on the system adenosine - 5'- triphosphate / sodium, potassium adenosine - 5' triphosphatase. Part 1: new determination of the catalytic activity of Na+,K+ ATPase
No full textDETERMINATION OF THE UREASE ACTIVITY AND RELATIVE INHIBITION IN THE PRESENCE OF SOME METAL IONS: A MICROCALORIMETRIC STUDY
No full textBatch microcalorimetry has been employed to obtain a calibration curve for the enzymatic activity of urease in solution.
This method is simplier, more reliable and easier to handle than the more common techniques (spectrophotometry and potentiometry), because it is based on direct investigation of the enzymatic reaction.
By comparison with calorimetric studies employing the thermistor combined with the immobilized, enzyme, this method also allows the catalytic activity to be measured.
Variations in the urease activity in the presence of nine metal ions [Hg(II), Ag(I), Cu(II),Zn(II), Cd(II), Ni(II), Co(II), Mn(II) and Mg(II)] are also described.
A graphic method has been devised for immediate identification of the minimum inhibitor concentration,determining the start, 50% and complete inhibition of ureasic activity
Simultaneous assay for aspartate aminotransferase and guanase in human serum by high-performance liquid chromatography
No full textA simple high-performance liquid chromatography (HPLC) assay for the simultaneous determination of guanase and aspartate aminotransferase (AST) activities in a single serum sample is described. The method is based on direct detection of enzymatically formed products xanthine and glutamate, respectively. The procedure is sensitive, precise (C.V. below 2% for guanase and 3% for AST), suitable for routine purposes and requires only 100 mu l of sample. Kinetic measurements have shown the guanase activity to have an apparent Michaelis constant of 24.5 mu M and the AST activity of 11.1 and 0.18 mM for aspartate and oxoglutarate, respectively, at 37 degrees C in Tris-HCl buffer (pH 7.5)
Spectrophotometric study of the reaction between cobalt(II)-dipeptide complexes and molecular oxygen
No full textThe influence of pH and ligand structure on the reaction
of cobalt(II) complexes with various dipeptides and molecular
oxygen was examined. The minimum pH value
required for the formation of dioxygen adducts was found
to be about 6.5. This value should be related to amidic
deprotonation of dipeptides, which seems to occur in the
examined systems at particularly low values. The location
and steric hindrance of the side chains of the dipeptides
have a strong influence on the reaction rate. The presence
of a substituent group on the N-terminal amino acid
promotes oxygen coordination, while, when the substituent
group ts on the C-terminal residual, a decrease of
reaction rate is observed.
A stabilizing effect of the aromatic ring on the dioxygen
adducts is found only when the substituent is in the
C-terminal position, and seems to be independent of the
presence of additional coordinating groups.
Some information regarding the mechanism of the
irreversible decomposition of the cobalt(II) complexes has
been obtained by studying the effect of pH and ligand
structure on the reaction rate
Microcalorimetric and spectrophotometric investigation on cobalt(II)-bromide system in ethanol
No full textComplex formation of 4,9-diazadodecane-1,12-diamine with copper(II) and zinc(II) ions in aqueous solution
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