Patent ID: 6974702

Claim:
A method for identifying at least one endogenous molecule that differs in abundance between a first cell population and a second cell population, comprising: (a) comparing a first Fourier Transform Mass Spectrometry (FTMS) peak profile obtained from the first cell population with a second FTMS peak profile obtained from the second cell population, wherein the first peak profile and the second peak profile are obtained independently; (b) identifying at least one peak that differs in intensity in the first FTMS peak profile relative to the second FTMS peak profile, which said at least one peak corresponds to at least one molecule that differs in abundance between a first cell population and a second cell population; and (c) identifying said at least one molecule that differs in abundance between the first cell population and the second cell population either directly from mass-to-charge (m/z) ratio of said at least one peak or through additional fragmentation of said at least one molecule; thereby at least one molecule that differs in abundance between a first cell population and a second cell population is identified.