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

The 6xHis tag, also known as polyhistidine tag, His6 tag and/or hexa histidine tag, is an amino acid motif consisting of at least 6 histidine residues fused to the carboxyl (C-) or amino (N-) terminus of a target protein in transfected cells. This tag is most commonly used in the production of recombinant proteins since the string of histidine residues binds to several types of immobilized ions (such as nickel, cobalt and copper) under specific buffer conditions to allow for the simple detection and purification of His-tagged proteins.

Agarose beads are small spherical beads of agarose gel which are commonly used in gel filtration or molecular size exclusion chromatography and biomolecular purification and immobilization. These beads act as porous gel to filter mixtures of molecules based on their individual sizes. And since these beads are easy to activate, they can also be used to bind biomolecules in a reversible or irreversible manner. In addition, their inert nature and unique internal surface area can also be activated for ligand attachment, making them the ideal basis for various affinity chromatography beads such as protein A and G, and glutathione.

Basically, spectrophotometry is one of the most widely used analytical procedures in biochemistry. It is commonly used to estimate the level of an analyte in solution and is ideal for simple routine determination of small quantities of materials. This method is based on the two laws of light absorption by solutions, namely Lambert's Law and Beer's Law.

Tagging your protein of interest can be extremely useful since it simplifies the purification protocol, improves the yield and solubility of your protein of interest and promotes the proper folding of their fusion partners. Due to their versatility, affinity tags (peptide sequences that are appended to the target protein) are recognized as one of the most powerful tools that can be used for basic biological research and in structural and functional proteomics as well.