Studies on acetylated human hemoglobin

Preparations of human hemoglobin of various degree of acetylation have been made. The compounds are stable and are spectroscopically indistinguishable from normal hemoglobin in the visible region. The molecular weights appear to be reduced to about half that of normal hemoglobin at the higher degrees of acetylation. The isoelectric points are shifted downward to pH 3.5 - 5.0, depending on the degree of acetylation. Even at the highest degree of acetylation achieved (~80%), the protein still combines reversibly with oxygen. However the value of the coefficient n of the Hill equation is reduced below its normal value and is no longer independent of pH; also, the value of log p _{1 2} is always lower than that for normal hemoglobin and tends to be independent of pH; i.e., the Bohr effect is largely eliminated. The number of sulfhydryl groups titratable with p-mercuribenzoate is reduced to zero.