Effect of chloride on oxygen binding to crystals of hemoglobin Rothschild (.beta.37 Trp .fwdarw. Arg) in the T quaternary structure

Oxygen binding to crystals of hemoglobin Rothschild (β37 Trp→Arg) in the T quaternary structure has been investigated by polarized absorption microspectrophotometry. These crystals were grown from poly(ethylene glycol) solutions containing low concentrations of salt. In the absence of chloride, they have a significantly higher oxygen affinity than crystals of human hemoglobin A grown in a similar manner, and exhibit Hill coefficients lower than 1. There is no Bohr effect from pH 6 to 9. We have found that chloride decreases the oxygen affinity of Hb Rothschild crystals, an effect which is absent in crystals of HbA