ACCURATE BASE COMPOSITION OF DOUBLE-STRAND DNA BY MASS-SPECTROMETRY

An accurate molecular weight (M(r)) assignment for a double-strand (ds ) DNA determines or greatly restricts the possible number of each of i ts four bases, while the compositions for its two single-strand (ss) c omponents can also be derived from their M(r) values. For a ds 64-mer (39 kDa), the ss-MI values (+/-0.5 Da) of its high-resolution mass spe ctrum from an electrospray ionization/Fourier transform instrument yie ld only the correct ds- and ss-base compositions. Literature mass spec tra of lower mass accuracy show that such data can also restrict their possible composition assignments, with further discrimination using t he abundance vs. base composition of small fragment ions from the diss ociation of the ss molecular ions. (C) 1996 American Society for Mass Spectrometry.