Fig. 1. (A) Reference spectra depicting the millimolar extinction coefficients of zebrafish oxygenated hemoglobin (oxyHb), methemoglobin (metHb), nitrosylhemoglobin (HbNO) and deoxygenated hemoglobin (deoxyHb) as function of wavelength at pH 7.3. (B) Representative result from the nonlinear least-squares curve-fitting procedure. The black curve shows the experimental spectrum of the diluted hemolysate from a nitrite-exposed zebrafish, and the red curve gives the fitted curve. The estimated millimolar concentrations of oxyHb, metHb, HbNO and deoxyHb in the cuvette, and the error on the parameter values, are shown in the insert.