Abstract: Analytical reagents and mass spectrometry-based methods using these reagents for the rapid, and quantitative analysis of proteins or protein function in mixtures of proteins. The methods employ affinity labeled protein reactive reagents having three portions: an affinity label (A) covalently linked to a protein reactive group (PRG) through a linker group (L). The linker may be differentially isotopically labeled, e.g., by substitution of one or more atoms in the linker with a stable isotope thereof. These reagents allow for the selective isolation of peptide fragments or the products of reaction with a given protein (e.g., products of enzymatic reaction) from complex mixtures. The isolated peptide fragments or reaction products are characteristic of the presence of a protein or the presence of a protein function in those mixtures. Isolated peptides or reaction products are characterized by mass spectrometric (MS) techniques.

Abstract: A system for automatically performing liquid chromatography analysis of low volume liquid chemical samples at nanosecond flow rates using an analysis column that integrates a pre-concentration trapping column and a chromatography separation column terminating at an electrospray nozzle of an online mass spectrometer. The analysis column consists of a capillary having an inside diameter of between 75 and 125 microns packed throughout with a porous bed of micron particles. A branch outlet positioned 10 to 16 centimeters upstream from the nozzle divides the analysis column into an upstream pre-concentration trap and a downstream separation column. An autosampler delivers low volume liquid samples to the upstream inlet via a two-position valve. Feed connections couple the autosampler to upstream inlet when the valve is open to inject a liquid sample into the pre-concentration trap at a maximum loading flow rate in the range from 0.5 to 50 microliters/minute.

Abstract: Analytical reagents and mass spectrometry-based methods using these reagents for the rapid, and quantitative analysis of proteins or protein function in mixtures of proteins. The methods employ affinity labeled protein reactive reagents having three portions: an affinity label (A) covalently linked to a protein reactive group (PRG) through a linker group (L). The linker may be differentially isotopically labeled, e.g., by substitution of one or more atoms in the linker with a stable isotope thereof. These reagents allow for the selective isolation of peptide fragments or the products of reaction with a given protein (e.g., products of enzymatic reaction) from complex mixtures. The isolated peptide fragments or reaction products are characteristic of the presence of a protein or the presence of a protein function in those mixtures. Isolated peptides or reaction products are characterized by mass spectrometric (MS) techniques.