SHORT COMMUNICATION Hb MANAWATU [a37(C2)Pro!Leu]: A NEW MILDLY UNSTABLE MUTATION AT AN INVARIANT PROLINE RESIDUE Stephen O. Brennan, 1, * Campbell Sheen, 1 and Stephen Johnson 2 1 Molecular Pathology Laboratory, Canterbury Health Laboratories, P.O. Box 151, Christchurch, New Zealand 2 Haematology Laboratory, Medlab Central, Palmerston North Hospital, Palmerston North, New Zealand Hb Manawatu [a37(C2)Pro!Leu] was detected in a 28-year-old female of British descent. Stability tests gave the first indication of the presence of an abnormal Hb, the isopropanol test giving a strong precipitate by 5 mins. Her MCV and MCH were low at 74.0fL and 24.0pg, respectively, while other red cell indices were within the normal range (Hb 12.2 g=L, RBC 5.2610 12 =L, PCV 0.38 L=L, MCHC 31.7 g=dL). Hb F (measured by alkaline resistance) and Hb A 2 levels were normal at <1% and 2.7%, respectively. No Hb H bodies were detected and there was no indication of hemolysis, as evinced by a normal haptoglobin level of 1.4g=L and a normal reticulocyte count (57610 9 =L). Cellulose acetate electrophoresis at pH 8.6 was normal, as was the elution profile from cation exchange high performance liquid chromatography (HPLC) at pH 6.5. Electrospray ionization mass spectrometry (ESI=MS), [1] however, showed that some 20% of the a chain material had a mass of 15,144 Da compared to 15,126 Da for the normal a A chain (Fig. 1). The fact that the new signal was not resolved from the Na adduct of a A at þ22 Da meant that the actual mass increase associated with the putative substitution might be somewhat less than the measured þ18 Da. This was confirmed by examination of the re-dissolved (1% HCOOH) isopropanol precipitate which showed that the unstable Hb had a chains of mass 15,142 Da, 16 Da higher than normal (Fig. 1). * Corresponding author. Fax: þ(64 3) 3640545; E-mail: steve.brennan@chmeds.ac.nz 389 DOI: 10.1081=HEM-120016376 0363-0269 (Print); 1532-432X (Online) Copyright # 2002 by Marcel Dekker, Inc. www.dekker.com HEMOGLOBIN Vol. 26, No. 4, pp. 389–392, 2002 ©2002 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc. MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016