The Protein Man's Blog | A Discussion of Protein Research

Recombinant proteins are useful for studying biological processes and the structure of protein. Selecting an appropriate expression system is a crucial factor to produce correctly folded protein. Factors to consider when choosing an expression system include:

Biotinylation, also known as biotin tagging/labeling, is the process of attaching biotin to a protein molecule and other macromolecules. Considering its high affinity to avidin and streptavidin (with a dissociation constant of around 10 ^-15 M, biotin-avidin/streptavidin interaction is one of the strongest non-covalent interactions existing in nature), its high specificity and fast on-rate, this technique is perfectly suited for isolating and purifying proteins and protein complexes, as well as identifying protein-protein interactions and post-translational events.  

Affinity purification, also called affinity chromatography, is a laboratory technique used for purifying protein or protein complexes within a biochemical mixture. Unlike other chromatography-based purification methods which separate molecules based on size (i.e., gel filtration or size-exclusion chromatography) or strength of ionic interaction with a solid phase material (i.e., ion exchange chromatography), affinity purification works by manipulating certain molecular properties and specific binding interactions between molecules to purify the protein of interest.

A restriction enzyme (restriction endonuclease) is a special enzyme that recognizes a specific sequence of nucleotides and cleaves DNA at that specific site (restriction site or target sequence). These enzymes, which are usually found in bacteria and other prokaryotes, are considered as one of the most important tools in recombinant DNA technology since they can easily cut DNA into fragments and/or join DNA molecules from different genomes so researchers can identify and characterize genes and examine gene expression and regulation.