Dehydration effects on the heme environment of nitric oxide hemoglobin.

Our aim is to study the binding of nitric oxide to human hemoglobin with different water contents. The binding is investigated using electron paramagnetic resonance (EPR), considering the paramagnetic character of the nitric oxide hemoglobin derivative. The EPR spectra obtained are made up of two types of spectrum whose proportions vary with the decrease in hydration down to about 0.25 g H2O per g protein, and are constant below this value. The two types of spectrum are interpreted as two possible configurations of the heme pocket in different populations of nitric oxide hemoglobin.