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. Author manuscript; available in PMC: 2015 Apr 1.
Published in final edited form as: Free Radic Biol Med. 2014 Jan 25;69:129–135. doi: 10.1016/j.freeradbiomed.2014.01.020

Fig. 1.

Fig. 1

Sulfhydryl oxidase assays of bovine serum. Panel A shows the homovanillic acid (HVA) assay in phosphate buffer, pH 7.5, containing 1 mM EDTA using 5 μL of fetal (FBS), newborn (NBS) and adult bovine sera (DBS) in a total assay volume of 150 μL (see Methods). The inset provides rates corrected for the protein content of the samples (see Methods). Panel B represents the Amplex UltraRed assay with increasing concentrations of recombinant human QSOX1. The inset shows the linearity of initial rates, corrected for the non-enzymatic background oxidation of thiols, as a function enzyme concentration. Panel C shows the Amplex UltraRed assay using 5 μL of fetal, newborn and adult bovine sera in the presence of 0.5% Tween 80 (see Materials and Methods). Control assays without serum are represented by CON. Two additional controls, lacking either DTT, or both DTT and serum, showed no detectable increase in fluorescence over the measurement period (data not shown). The inset presents initial rates normalized to the protein concentration of the serum samples.