Reference visible spectra for the hemoglobin species expected to be involved in the reaction with nitrite corresponding to A) bHb, C) Thb and E) RHb. Panels B, D and F show representative spectral changes in the reaction of hemoglobin and nitrite for bHb, THb and RHb respectively. Experiments were performed using 30μM hemoglobin and 750μM nitrite with the exception of RHb where 250μM nitrite was used instead. Fractional saturations were bHb: 0.45, THb: 0.4 and RHb: 0.49. Spectra were collected every 30 seconds for 15 minutes. In the interest of clarity, only data collected every 4 minutes is shown in the graph. Inserts show respective residual plots obtained from fitting the experimental data to the reference spectra.