PROTEIN IDENTIFICATION AT THE LOW FEMTOMOLE LEVEL FROM SILVER-STAINEDGELS USING A NEW FRITLESS ELECTROSPRAY INTERFACE FOR LIQUID-CHROMATOGRAPHY MICROSPRAY AND NANOSPRAY MASS-SPECTROMETRY

Conventional capillary liquid chromatography/mass spectrometry (LC/MS) typically employs low mu l/min how rates with gas/liquid sheath to en hance spray stability. Over the past several years a number of reports have demonstrated success with electrospray (ES) interface designs op timized for submicroliter/min hows which have clear advantages in term s of enhancement of detection Limit, lower sample consumption, and abi lity to accommodate a wider range of buffer conditions. We report here a fritless electrospray inter-face (FESI) design that is inexpensive and robust and can be operated and adapted to accommodate a variety of applications for submicroliter/min flow rates. The novelty of this in terface revolves around the use of a fritless microcapillary column an d precolumn application of electrospray voltage at a microtee junction to achieve stable microspray and nanospray flow rates. This sheathles s FESI device eliminates postcolumn dead volume since small particles (less than or equal to 10 mu m) are packed directly into laser-pulled fused silica capillary needles from which a spray originates. For anal ysis of proteins/peptides in solution, low femtomole sensitivity has b een achieved (attomoles for selected-ion monitoring), while low nanogr am sensitivity was attained for proteins derived from in-gel-digested silver-stained bands from 1-D and 2-D gels, Several applications for t andem MS protein/peptide identification using LC-microspray, LC-nanosp ray, or infusion nanospray are presented, (C) 1998 Academic Press.