INTEGRATED MULTICHANNEL MICROCHIP ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY - ANALYSIS OF PEPTIDES FROM ON-CHIP TRYPTIC DIGESTION OF MELITTIN

In continuation of our work to develop an integrated multichannel micr ochip interfaced to electrospray mass spectrometry (ESI-MS), this pape r demonstrates one of several applications of this approach in monitor ing tryptic digestion products, The multichannel microchip allowed int egration of sample preparation onto the microchip to facilitate the an alysis process, Melittin was selected as a model oligopeptide because it possesses a cluster of four adjacent basic residues,which enable pr obing the site specificity of trypsin as a function of digest times. R eactions were performed on-chip in different wells for specific time p eriods and then analyzed by infusion from the microchip by ESI-RIS, us ing leucine enkephalin as internal standard. The rate of formation and disappearance of the molecular ion and individual fragments was follo wed for a melittin to trypsin concentration ratio of 300:1. The result s indicate the potential of integrating enzymatic reactions with multi channel microchip ESI-MS for automated optimization of reaction condit ions while consuming only small amounts of sample. (C) 1997 by John Wi ley & Sons, Ltd.