Cell-free protein expression systems have a wide range of applications across various fields of research and industry. The main applications include: 

Cell-free protein expression systems  can be broadly classified based on the source of the cellular extract used to power protein synthesis.

A cell-free protein expression system is a method of synthesizing proteins in vitro, using the necessary components extracted from cells rather than relying on living cells. By providing a DNA template, ribosomes, amino acids, enzymes, and other intracellular components in a test tube, scientists can directly produce proteins in an artificial environment.

When conducting various experiments, the required purity of  proteins can vary significantly depending on the specific goals, detection methods, and downstream applications. Below is a table summarizing the protein purity requirements for different types of experiments:

While affinity tags (e.g., His-tag, GST-tag) are commonly used to facilitate protein purification, there are scenarios where tag-free proteins are desired, especially for structural studies, therapeutic applications, or functional assays where the tag might interfere with the protein's activity. Here are several strategies to obtain tag-free proteins: