(A) Reaction of oxyHb with nitrite at nitrite/oxyHb molar ratio of 2/1 followed continuously for 20 h. OxyHb concentration 30 µM, nitrite 60 µM, PBS, 37 °C, pH 7.4, absorption spectra were recorded every 5 min, for clarity only spectra taken in 2 h intervals are plot. Directions of changes in absorption spectra of hemoglobin (black lines) in time are marked by arrows. The residuals between MLR analysis using set of absorption spectra from (B) are plot as gray lines. (B) Standard absorption spectra of pure oxyHb, metHb and ferrylHb used in MLR analysis.