Direct targeting of human plasma for matrix-assisted laser desorption/ionization and analysis of plasma proteins by time of flight-mass spectrometry

✍ Scribed by Ya Jin; Takashi Manabe

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 891 KB
• Volume: 26
• Category: Article
• ISSN: 0173-0835
• DOI: 10.1002/elps.200410421

✦ Synopsis

Abstract

A method to analyze human plasma proteins without fractionation, directly applying a plasma‐matrix mixture on the target plate of a matrix‐assisted laser desorption/ionization‐time of flight‐mass spectrometer (MALDI‐TOF‐MS), has been described. Peaks of ionized plasma proteins could not be detected applying a mixture of an undiluted plasma sample and a matrix solution, but they appeared when the plasma was diluted before mixing with the matrix. Tenfold diluted plasma provided well‐resolved protein peaks in the m/z range from 4000 to 30 000. The addition of a simple post‐crystallization washing procedure performed on the target plate further improved the quality of mass spectra. We numbered 58 peaks in the range of 4–160 kDa and 32 out of which were assigned to the plasma protein species which have been reported. Especially high sensitivity and resolution were obtained in the region < 30 kDa, where multiple isoforms of apolipoprotein A‐I, apolipoprotein A‐II, apolipoprotein C‐I, apolipoprotein C‐II, apolipoprotein C‐III, and transthyretin could be assigned. Various post‐translational modifications are involved in the isoforms, e.g., proteolytic cleavage, glycosylation and chemical modifications. This method will become complementary with the present electrophoretic techniques, especially for the analysis of low‐molecular‐mass proteins.