MALDI-ISD Mass Spectrometry Analysis of Hemoglobin Variants: a Top-Down Approach to the Characterization of Hemoglobinopathies.

ABSTRACT: Hemoglobinopathies are the most common inherited disorders in humans and are thus the target of screening programs worldwide. Over the past decade, mass spectrometry (MS) has gained a more important role as a clinical means to diagnose variants, and a number of approaches have been proposed for characterization. Here we investigate the use of matrix-assisted laser desorption/ionization time-of-flight MS (MALDI-TOF MS) with sequencing using in-source decay (MALDI-ISD) for the characterization of Hb variants. We explored the effect of matrix selection using super DHB or 1,5-diaminonaphthalene on ISD fragment ion yield and distribution. MALDI-ISD MS of whole blood using super DHB simultaneously provided molecular weights for the alpha and beta chains, as well as extensive fragmentation in the form of sequence defining c-, (z + 2)-, and y-ion series. We observed sequence coverage on the first 70 amino acids positions from the N- and C-termini of the alpha and beta chains in a single experiment. An abundant beta chain N-terminal fragment ion corresponding to ?c34 was determined to be a diagnostic marker ion for Hb S (?6 Glu?Val, sickle cell), Hb C (?6 Glu?Lys), and potentially for Hb E (?26 Glu?Lys). The MALDI-ISD analysis of Hb S and HbSC yielded mass shifts corresponding to the variants, demonstrating the potential for high-throughput screening. Characterization of an alpha chain variant, Hb Westmead (?122 His?Gln), generated fragments that established the location of the variant. This study is the first clinical application of MALDI-ISD MS for the determination and characterization of hemoglobin variants.

SUBMITTER: Theberge R 

PROVIDER: S-EPMC4496427 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature