FAQ: Based on my application, should I use the NEBExpress® Cell-free E. coli Protein Synthesis System (NEB #E5360) or the PURExpress® In Vitro Protein Synthesis Kit (NEB #E6800)? 

The NEBExpress® Cell-free E. coli Protein Synthesis System and PURExpress In Vitro Protein Synthesis Kit are both suited for high yield protein synthesis of a variety of protein targets, under the control of T7 RNA Polymerase.  Both products offer convenient reaction analysis by SDS-PAGE or by direct assay.  Both systems are compatible with plasmid and linear DNA templates; mRNA can also be used as a template.

PURExpress is a reconstituted system and therefore provides a more defined reaction environment with minimal nuclease and protease activity.  Downstream applications such as directed protein evolution, translation studies and protein/protein interactions are particularly suited to PURExpress.  PURExpress is also ideal for applications where components of the translational machinery are selectively left out (PURExpress Δ (aa, tRNA) Kit, PURExpress Δ RF123 Kit, PURExpress Δ Ribosome Kit), including non-natural amino acid incorporation, radiolabeling and ribosome studies. In PURExpress, all protein components (except ribosomes) are recombinant and His-tagged allowing for reverse purification. 

The NEBExpress® Cell-free E. coli Protein Synthesis System is preferable to isolate proteins that are His-tagged. In addition, it has a lower cost per reaction, making it more easily scalable to large volume applications. 

To compare PURExpress and the NEBExpress® Cell-free E. coli Protein Synthesis System by application, reference the application chart under the tools and resources tab.