Hemoglobin F Lódź (G gamma I 44 Ser replaced by Arg). A newly identified variant from an American infant of Polish descent.

An electrophoretically slowly migrating hemoglobin variant was identified in a neonate of Polish parents from a cord blood hemoglobin survey. Structural analysis of the gamma chain of the mutant hemoglobin, with fractionation of the tryptic peptides by means of high-performance liquid chromatography, demonstrated a substitution of serine-44 by arginine. Glycine was identified at position 136 of the gamma chain and isoleucine at position 75. Serine residue 44 appears not to be a heme contact site, but as a result of the substitution in this mutant hemoglobin, the possibility exists for formation of a salt bridge between the arginine and a heme propionate group. The infant's hematologic findings suggested the possibility of mild hemolysis, but these changes may have been due to isoimmune disease.