Protocol

Bulk 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

This protocol can be used to concentrate bulk proteins from large volumes of solution. Few proteins precipitate when the concentration of ammonium sulfate in the solution is <25% saturation, whereas a concentration of ~75% saturation at 4ºC is high enough to precipitate most proteins. Higher concentrations of ammonium sulfate (up to 100% saturation) increase the density of the protein suspension, making it more difficult to recover the protein by centrifugation.

MATERIALS

Reagents

Ammonium sulfate (analar grade)

Resuspension buffer

This buffer is used to resuspend the concentrated protein after ammonium sulfate precipitation. The choice of buffer will depend on the subsequent application.

Solution . . . [Full Text of this Article]

Equipment

METHOD