The radicals ABTS• + were generated by the addition
of 2.45 mM potassium persulfate to an 7 mM ABTS solution prepared
in phosphate-buffered saline (PBS, pH 7.4) and allowing the mixture
to stand in darkness at room temperature for at least 12 h before use.
The ABTS + stock solution was adjusted with PBS to an absorbance of
0.7 (±0.02) at 734 nm in a 1 cm cuvette at 25 °C (Lambda 25 UV, VIS
spectrophotometer, Perkin Elmer Instruments, Madrid, Spain).