Molecular mass measurement of polymerase chain reaction products amplified from human blood DNA by electrospray ionization mass spectrometry.

We report here on the first analysis of polymerase chain reaction (PCR) products amplified from a small amount of human blood DNA by electrospray ionization mass spectrometry (ESI-MS). Adenomatous polyposis coli (APC) gene fragment of about 50 base pairs (bp) with a relative molecular mass (M(r)) of approximately 15,000 u was amplified from human blood DNA by PCR. The accurate molecular mass of the PCR products was determined with an accuracy of approximately 0.005% by ESI-MS. The amount of DNA used was only 100 ng (approximately 50 zmol; the theoretically required amount of blood is therefore less than 1 microliter for PCR). The ESI-MS measurement of the PCR products proved to be a new accurate, sensitive and fast tool for gene diagnosis.