Amperometric and polarographic study of the SH-activity of MEPRIN (alpha-mercapto-propionylglycine).
The SH-groups of alpha-mercapto-propionylglycine (MEPRIN) are remarkably stable in diluted solution either at room temperature or at 50 degrees C, even if storing takes place under air-bubbling. The SH-activity was measured by polarographic method and amperometric titration. Neutralization of the carboxyl group decreases the stability of the sulfhydryl groupings. Evaporation of neutralized solution leads to a 30--50 per cent decrease of SH-activity. Lyophilization reduces this loss by 10--15 per cent. Neutralization is best carried out in the absence of oxygen; in this case, 94 per cent of the sulfhydryl activity will persists, irrespective of the pH. The dissociation constant of MEPRIN-SH is pK' = 8.47. The SH-stability of the product is satisfactory when neutralized in nitrogen atmosphere to pH 3--5; a loss of only 5 per cent can be expected after storing in an oxygen-free 10(-3) molar solution for 144 hours. Between pH 6 and 8 this value is 31 per cent on the average, while at pH 9 it is more favorable again.
Amperometric and polarographic study of the SH-activity of MEPRIN (alpha-mercapto-propionylglycine). The SH-groups of alpha-mercapto-propionylglycine (MEPRIN) are remarkably stable in diluted solution either at room temperature or at 50 degrees C, even if storing takes place under air-bubbling. The SH-activity was measured by polarographic method and amperometric titration. Neutralization of the carboxyl group decreases the stability of the sulfhydryl groupings. Evaporation of neutralized solution leads to a 30--50 per cent decrease of SH-activity. Lyophilization reduces this loss by 10--15 per cent. Neutralization is best carried out in the absence of oxygen; in this case, 94 per cent of the sulfhydryl activity will persists, irrespective of the pH. The dissociation constant of MEPRIN-SH is pK' = 8.47. The SH-stability of the product is satisfactory when neutralized in nitrogen atmosphere to pH 3--5; a loss of only 5 per cent can be expected after storing in an oxygen-free 10(-3) molar solution for 144 hours. Between pH 6 and 8 this value is 31 per cent on the average, while at pH 9 it is more favorable again.