Identificationof CoordinatePairsof Polypeptides:A Techniquefor Screening of PutativePrecursorProductPairsin 2D Gels

izedquantificationof individualproteins,providesa sensitive and accurate approach to detection of small differencesin the proteinpattern.As an extensionof “oue, ” a data base system for the analysis of two-dimensionalelectrophoretic gels,we reporthere on a screeningalgorithmfordetectionof certainpost-translationalmodificationevents. It is based on the assumptionthat, if there is a post-translationalmodifica-tion of a protein in the transition between two functional statesof a biologicalsystem, in manycasesthesumof the proteinconcentrationof a precursor-productpair in one is equivalentto that in the other. In additionto the identification of candidate pairs with a precursor-product relationship, cues to the nature of the post-translationalmodificationthat mightrelatethem mightalso be derivedfromcomparisonsof the isoelectric point and apparent molecular mass. Thi