Direct Analysis of Intact Proteins Using the Advion Touch Express^™ Open Port Sampling Interface (OPSI) with the Advion expression^L Compact Mass Spectrometer

Introduction

Electrospray mass spectrometry (ESI-MS) is a versatile analytical tool for biomolecular protein analysis and proteomics. One important area is to study protein structure and composition in which peptides and proteins can be ionized with multiple charges via electrospray ionization. Based on the charge envelope, the molecular weight can be easily determined using manual or automated deconvolution.

Touch Express^™ is a new sampling device for mass spectrometry analysis using a technique developed by Gary Van Berkel and Vilmos Kertesz of Oak Ridge National Laboratory1 — the Open Port Sample Interface (OPSI). The OPSI incorporates an open port of continuous, low-volume solvent, flowing directly into the electrospray ion source of the mass spectrometer. Analysis is carried out by simply touching a sample to this port. This fast, versatile sample inlet paired with the expression^® Compact Mass Spectrometer (CMS) provides simple molecular weight determination of surfaces, solids and liquids.

Touch Express^™ OPSI is a direct analysis method for peptide and protein identification, introduced into the Advion expression^® CMS and ionized via the ESI source. The sample can be analyzed < 1 min, and the continuous flow of solvent by OPSI also saves chemists more time for their compound analysis without contamination issues when one system is shared by multiple users or when running back-to-back samples. The deconvolution feature implemented in Advion Data Express software can easily help chemist to predict uncharged mass of their target peptides or proteins based on their charge envelope. Three compounds: BSA, myoglobin (horse) and lysozyme, are used for demonstration.