On the chemical abnormality of Hb "Alexandra", a fetal hemoglobin variant.

H UMAN FETAL HEMOGLOBIN consists of two unlike pairs of polypeptide chains, i.e., a2y2. While the detection of an a-chain variant may not present serious difficulties, since the abnormal fetal hemoglobin will be replaced by the adult type, the y-chain variants are transitory and their study is limited by time, shortage of blood and their rarity. Identification of the y-chain anomaly has been possible in the recently described hemoglobins FTexas ,1,2 FTexas II and FHU1I.4 In other previous reports, suggestive cvidence for placing the anomaly on the y-chain is available for hemoglobins “Alexandra” 5,6,7 and “Aegina,” 8 FROm5,9 Fwarren o and FH0115tOfl.1’ Of these, Hbs “Aegina” and FRoma move faster than normal Hb F in electrophoresis at pH 8.4; the other variants move slower displaying towards Hb F a relative mobility similar to either that of Hb S to Hb A ( Hbs “Alexandra,” Fwarren and F110118 0 ) of that of Hb C to Hb A ( Hbs FHun and FTeXSS I and II). The Hb “Alexandra” which was observed in this laboratory in 1958 has never been refound since then, though numerous cord blood samples have been examined. Hb “Alexandra” constituted 10-15 per cent of the whole pigment and moved as a faint band between Hb S and Hb A2 in electrophoresis at pH 8.4 ( Fig. 1 ) . The aim of this paper is to present the fingerprinting of this fetal variant.