Carlos Pascual

VISIBLE CHEMILUMINESCENCE ASSOCIATED WITH THE REACTION BETWEEN METHEMOGLOBIN OR OXYHEMOGLOBIN WITH HYDROGEN PEROXIDE

Abstract Visible chemiluminescence is emitted in the irreversible deactivation of hemoglobin or methemoglobin with excess H2O2. The emission takes place in two phases. The most intense one lasts a few seconds and is followed by a second phase of lower intensity that remains for longer periods. This second phase presents chaotic or sustained oscillations. Free radicals are implicated in the luminescent process since the emission can be reduced by free radical scavengers such as 6‐hydroxy‐2,5,7,8,‐tetramethylchroman‐2‐carboxylic acid (Trolox) or ascorbic acid. These additives lead to a delay in reaching the maximum intensity, which can be related to their consumption, implying substantial recycling of the hemoprotein. Chemiluminescence is also observed in the oxidation of hemin by H2O2, suggesting a role for the heme group in the processes leading to the excited state production. The lower intensity observed in the presence of hemin can be related to the contribution of the globin chains.

On the Use of the Quenching of Luminol Luminescence to Evaluate Sod Activity

Addition of horseradish peroxidase to a luminol solution (pH = 9.4) produces a burst of light followed by a steady luminescence that lasts for several minutes. This steady-state luminescence is readily quenched by SOD, with a Q1/2 concentration (the additive concentration needed to decrease by one-half the emitted luminescence intensity) of c.a. 4 ng/ml (14 mU/ml). The luminescence intensity decrease can then be employed to evaluate SOD activity in SOD-containing samples. However, the light intensity can also be quenched by additives, such as Trolox, that are able to trap luminol-derived intermediates. It is proposed that double quenching experiments must be performed in order to be able to relate the observed effect of an additive to its SOD-like activity.

Genetic and biochemical studies of phosphomannose isomerase deficient mutants ofSaccharomyces cerevisiae

SummaryThree mannose-negative mutants ofSaccharomyces cerevisiae have been isolated. These mutants showed growth inhibition when mannose was added to a growth medium containing glycerol or fructose.Crosses between wild type mutants showed segregation of 2+/2−. Crosses between the mutants themselves showed that they were closely linked.Two mutants (XM3 and D2) showed characteristics of allelic structural alteration of phosphomannoseisomerase. Mutant D4 had a deficiency of phosphomannoseisomerase activity, but with a normal thermostability. Revertants from D4 had a normal thermostability.

A New Luminol Sensitized Chemiluminescence Method for Determination of Superoxide Dismutase

Abstract A new, simple, rapid and economic chemiluminescent Method Msa developed -for determination of superoxide dismutase (SOD). The method is based on the inhibition by SOD of the chemi luminescence signal produced in the reaction between luminol and horseradish peroxidase (HRP) which liberates superoxide anion. The peak value of the chemi luminescence produced in the reaction is linearly related to the HRP concentration while the effect of luminal concentration on the reaction shows a hyperbolic function which fits an enzyme substrate mechanism of the Michaelis-Menten type. A straight line was obtained when the reciprocals of the chemiluminescence intensity values were plotted vs different concentrations of SOD standards and this served as the calibration curve. Erythrocytes hemolyzate prepared from 27 blood samples containing different concentrations of SOD was used to compare this method with the conventional spectrophotometric cytochrome c method which was used as reference. The correlation coeffic...