Abstract
Isoelectrofocusing and high performance liquid chromatographic methods were used to study an abnormal hemoglobin present in a Black male infant and his mother. The variant, named Hb Sinai-Baltimore, focused slightly behind Hb A and separated incompletely from Hb A by cation exchange high performance liquid chromatography, while the separation of the βA and βX chains by reversed phase high performance liquid chromatography was complete. The variant was identified through an analysis of peptides in a tryptic digest of the isolated βX chain and by sequencing of amplified DNA which included the β-globin gene. The Val→Gly replacement at position βl8 (codon 18; GTG→GGG) or at the last position of the A helix decreases the stability of the variant without affecting the hematological parameters of its carrier. The propositus was a compound heterozygote for Hb Sinai-Baltimore and Hb S; the relative quantities of the two variant chains were somewhat different from those of the βX and βA chains in the mother with the simple Hb Sinai-Baltimore heterozygosity. An uncertainty about the α-globin gene status in the child prevented a further evaluation of these differences.