Fig. 4.

Titration of cNP with NO at pH 5.5 and 7.4. (A) Change in absorption at 437 nm (pH 5.5), plotted against total NO concentration and fitted to a mutually depleting model (see methods), yielding $K_{\mathrm{d}}=70\pm 30\text{nM}$ (n = 3). Inset: difference spectra. (B) Change in absorption at 437 nm (pH 7.4), plotted against the free NO concentration and fitted to a simple hyperbola, yielding $K_{\mathrm{d}}=4.4\pm 1.7\mu \mathrm{M}$ (n = 5). Inset: difference spectra.