| Abstract
| - Quantification of mixture components from their composite optical or mass spectra is a common need inanalytical chemistry. We encountered the need whenapplying a combination of enzymatic digestion with nuclease P1 and tandem mass spectrometry to a mixture ofisomeric photomodified oligodeoxynucleotides. In theprocedure, we collisionally activated the [M − H]- or [M+ Na − 2H]- ion of trinucleotide triphosphates, whichwere extricated enzymatically from the larger, damagedoligodeoxynucleotides, and we measured the relativeabundances of characteristic fragment ions. The resultssometimes yield curved calibrations for plots of therelative fragment ion abundances in the product ionspectra of isomers versus their relative amounts. Wedeveloped a normalized linear model, which brings understanding to the nonlinear plots and allows quantification of the mixture components from their compositespectra. The outcome demonstrates a general quantification procedure and shows that different yields for generating fragment ions from different constituents of themixture cause the curved calibration lines.
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