The T7 Sample System is designed to facilitate the optimization of individual gene expression by offering four unique in vitro translation systems to evaluate. The system consists of samples of: TNT T7 Quick for PCR DNA, TNT T7 Quick Coupled Transcription/Translation System, TNT Coupled Wheat Germ Extract System and E. coli T7 S30 Extract System for Circular DNA. All of the coupled systems utilize RNA generated by a T7 phage promoter. Criteria such as post-translational modifications, ionic optimization and detection methods (i.e., non-isotopic) should be considered when choosing an in vitro system. In some cases only direct experimental results will confirm which system is best for specific genes.