ENHANCEMENT OF THE EFFECTIVE RESOLUTION OF MASS-SPECTRA OF HIGH-MASS BIOMOLECULES BY MAXIMUM ENTROPY-BASED DECONVOLUTION TO ELIMINATE THE ISOTOPIC NATURAL-ABUNDANCE DISTRIBUTION

Although high-resolution Fourier transform ion cyclotron resonance mas s spectrometry can resolve individual isotopic masses for biomolecules of more than 100 ku, its effective mass accuracy is limited by the di stribution of naturally occurring rare isotopes (C-13, N-15, O-18, S-3 4, etc.). in this article, we compare least-squares and maximum entrop y methods for deconvolution of the isotopic natural abundance distribu tion to narrow the mass spectral isotopic abundance envelope for great ly enhanced effective mass resolution. We apply both methods to yield deconvolved high-resolution deuterium distributions for peptides and p roteins subjected to H/D exchange prior to electrospray Fourier transf orm ion cyclotron resonance mass analysis. In addition, we show that e ven unresolved isotopic envelopes from a quadrupole mass spectrometer can be narrowed for considerably improved resolution there as well. (C ) 1997 American Society for Mass Spectrometry.