NO measurements ). Moreover, the • NOscavenging efficiency of 2-(4-Carboxyphenyl)-4,5-dihydro-4,4,5,5-tetramethyl-1H-imidazol-1-yloxy-3oxide potassium salt (C-PTIO), employed as a standard • NO-scavenging compound was found to be lower than that of any tested compound at the same concentration. These observations were comparable to those of the • NO concentrations released from different concentrations of DETA-NO (supplementary fig. ). Furthermore, in the absence of any • NO-donor, slight changes in the voltage signals within the range of 0-0.008 V were detected following the injection of each compound to the culture medium (supplementary fig. ). This confirms the specificity of the observed decay in voltage in the presence of • NO to its scavenging, not to the tested compounds themselves. In addition, each tested solution was purged with nitrogen, which caused a drop in the readings, confirming the specificity of the recorded voltage to • NO. Moreover, the release of • NO from DETA-NO, newly added to incubated culture medium containing each of these compounds, was evaluated. This was found to be insensitive to hemin solution incubated for 16 hours, while the longer incubation periods caused a significant inhibition of • NO-release (data not shown). Next, the influence of temperature, culture medium, and its components on the • NO-scavenging by the different compounds was evaluated. Here, each compound was diluted to 20, 100 and 1000 μM in the FBS-containing medium and incubated for 16 and 40 hours at 37 o C. This was followed by the testing of the scavenging efficiency of the concentration 8 μM from each solution for • NO released from 300 μM DETA-NO. Generally, the rate of • NO-release in the incubated medium only was lower than that observed when DETA-NO was added to non-incubated medium. Moreover, the • NO-scavenging efficiency of freshly diluted hemin and H-Tyra in medium was found to be inhibited with prolonged