Collective behaviour of hemoglobin in dense solutions

The formation of radical pairs of spin-labelled hemoglobin molecules (beta-93 cysteine) in a mixture with unlabelled hemoglobin of concentrations higher than the critical one [(5.7 less than c less than 6.3) mM/sigma per heme] is due to some kind of long-range order characterizing these solutions. Labelled molecules induce pertubation in an unlabelled hemoglobin solution of concentration higher than the critical one. The collective behaviour of unlabelled molecules gives rise to the formation of radical pairs of spin-labelled hemoglobin molecules. Such behaviour is dependent on the ligand bound at the heme iron (carbonmonoxide, oxygen, or water.)