Characterization of Hemoglobin Variants by MALDI-TOF MS Using a Polyurethane Membrane as the Sample Support

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Abstract
A new method for the sampling and off-site analysis of hemoglobin variants by mass spectrometry is reported. This technique uses a nonporous polyurethane membrane as the collection device and transportation medium of a blood sample for analysis. The same membrane is then used as the MALDI-TOF MS sample support for mass spectrometric analysis. Minimal invasive sample collection is afforded by collecting less than 1 μL of blood using a common lancet device. MALDI-TOF MS is performed directly on the membrane, after washing off the interfering plasma components, followed by the addition of matrix. This reduces the time of analysis and prevents sample loss. Enzymatic digestion can be performed directly on the membrane, using in this case trypsin, allowing for further characterization of the sample. The method is much less invasive compared to drawing blood with a syringe. The sample may be transported to the laboratory by regular mail, and thus the method can serve remote locations. We demonstrate the procedure by characterizing the Hb Shepherds Bush hemoglobin variant, b74(E18)Gly→Asp.