Water sorption and vapor-phase deuterium exchange studies on methemoglobin CC, SC, SS, AS, and AA

Five hemoglobins whose genetic relationship to one another involves one set of alleles, hemoglobins CC, SC, SS, AS, and AA, were studied in the Met form. Two different investigations were conducted at 28 degrees C on these methemoglobins within a McBain gravimetric sorption system: sorption of H(2)O vapor and vapor-phase deuterium-hydrogen exchange. For each of the five samples there was close agreement between the per cent hydration of polar sites as determined from sorption studies and the maximum per cent of labile hydrogens that were exchanged during the vapor-phase deuterium exchange study. Both studies measured a slight increase in the number of polar sites accessible to H(2)O or D(2)O vapor for those samples in which the substituent in the sixth position from the N-terminus of the two beta-chains had a positively charged side chain and a slight decrease for those in which the substituent had a negatively charged side chain. The in-exchange of deuterium for hydrogen occurred at a faster observed rate than the out-exchange of hydrogen for deuterium.