Hb Ashburton [β12(A9)Thr → Pro; HBB: c.37A > C], a novel, mildly unstable variant and the first substitution identified at codon 12.

We report the identification of a novel, slightly unstable hemoglobin (Hb) variant [β12(A9)Thr → Pro; HBB: c.37A > C] that came to our attention during Hb A1C ion exchange chromatography where it migrated as a trailing shoulder on the Hb A0 peak. On electrospray ionization mass spectrometry (ESI MS), this electrophoretically silent variant was detected as an unresolved β component with a 2 Da decrease in average β chain mass.