Protein identification at the low femtomole level from silver-stained gels 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 enhance spray stability. Over the past several years a number of reports have demonstrated success with electrospray (ES) interface designs optimized for submicroliter/min hows which have clear advantages in terms of enhancement of detection Limit, lower sample consumption, and ability 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 interface revolves around the use of a fritless microcapillary column and precolumn application of electrospray voltage at a microtee junction to achieve stable microspray and nanospray flow rates. This sheathless 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 analysis of proteins/peptides in solution, low femtomole sensitivity has been achieved (attomoles for selected-ion monitoring), while low nanogram sensitivity was attained for proteins derived from in-gel-digested silver-stained bands from 1-D and 2-D gels, Several applications for tandem MS protein/peptide identification using LC-microspray, LC-nanospray, or infusion nanospray are presented, (C) 1998 Academic Press.