Protocol

Fractional Precipitation of Proteins by Ammonium Sulfate

This protocol was adapted from "Concentrating Solutions of Protein," in Appendix 3 of Purifying Proteins for Proteomics (ed. Simpson). Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, USA, 2004.

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INTRODUCTION

Proteins with surface patches that are easily dehydrated precipitate at lower ammonium sulfate concentrations than those with a tightly bound solvation shell. Once the concentration at which the target protein precipitates is known, fractional precipitation with ammonium sulfate can be used as an early step in a purification protocol. A pilot experiment should be performed using a small volume (10-20 ml) of the protein solution to ascertain the range of ammonium sulfate concentrations over which the target protein precipitates.

MATERIALS

Reagents

Ammonium sulfate (analar grade)

Resuspension buffer

This buffer is used to resuspend the concentrated protein after ammonium sulfate precipitation. . . . [Full Text of this Article]

METHOD