Fig. 4.
Correlation between post Cu2+-peak heights and DEA/NO concentrations. (A) NO time traces observed with the NO electrode with 50, 200, 400, and 1000 nM DEA/NO in the presence of GSH. Individual traces were shifted horizontally and vertically for clarity. (B) Peak heights observed with a range of DEA/NO concentrations between 50 nM and 1 µM (n=3). Peak heights correspond to the amount of GSNO formed at the time of CuSO4 addition. See main text and the supplementary material for details. Data were fitted (dashed lines) to the equation [NO]peak=C2·[DEA/NO]C1, in which C1 and C2 are variables. The fit is linear with C1 close to 1 (1.14±0.02), suggesting a linear relationship between peak height and DEA/NO concentration. The apparent absolute correlation between observed peak heights and DEA/NO concentrations (1 µM NO for 1 µM DEA/NO) is accidental: it does not reflect a one-to-one correlation between NO and GSNO, because DEA/NO can produce more than 1 equivalent of NO. Experimental conditions: 1 µM DEA/NO, 2 mM GSH, 4 mM CuSO4, 1000 U/ml SOD, 0.1 mM DTPA, 5 mM MgCl2, and 50 mM TEA (pH 7.4) in 0.5 ml at 37 °C.