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Peptide Tags

From the basic research on the structure and function of the protein to the development of the expression and purification process of functional protein, affinity tags have become an important and effective tool for the purification of recombinant proteins. Affinity tags are so named because they are often used in affinity purification: a technique for purifying proteins from cell lysate. By attaching an affinity tag to your protein of interest, it can be pulled out of the solution via chemical or physical interactions with an immobilized substrate. The exact affinity chromatography method is dependent on the specific tag used.


The affinity-tag systems always have the following features:

-- One-step adsorption purification

-- A minimal effect on the tertiary structure and biological activity

-- Easy and specific removal to produce the native protein

-- Simple and accurate assay of the recombinant protein during purification

-- Applicability to several different proteins


KMD Bioscience can provide synthesis of the following peptide tags but are not limited to:


Flag tag

* Flag tag (DYKDDDDK) is a common, well-characterized hydrophilic tag. It is always used in conjunction with antibodies in protein pull-downs to study protein interactions. Flag tag can be incorporated on N-, C- or internal positions of the target protein.

HA tag

* HA tag (YPYDVPDYA) is derived from the human influenza hemagglutinin (HA) molecule corresponding to amino acids 98-106, and it is an ideal tag for co-IP and western blots, with small interference to the function of the protein. HA tag has been extensively used as a general epitope tag in expression vectors.


* PolyHis tags are widely used for protein purification due to their small size and stable binding. Although tags can range from 2–10 histidine residues, the most common His-tag is the 6x-His tag, or hexatag, which contains six histidine residues. Histidine forms coordination bonds with immobilized transition metal ions, and this property can be utilized for protein purification. Cobalt and zinc columns are available for immobilized metal affinity chromatography (IMAC), but nickel columns are usually used. As His-tags are short peptide sequences, they rarely affect the properties of the fused protein, although the optimal placement of the tag is protein specific.

Myc tag

* Myc tag (EQKLISEEDL) is a small, immunoreactive tag, and can be placed at the N- or C- terminus. Myc tag is a popular epitope tag for detecting the expression of recombinant proteins in yeast, bacteria, insect, and mammalian cell systems.


* Glutathione-S-transferase (GST) is a protein consisting of 211 amino acids and has a molecular weight of ~26 kDa.  Native GST is responsible for protecting the cell against noxious compounds and oxidative stress. A major property of GST is its affinity for the tripeptide, glutathione, which can be utilized in affinity chromatography.  When a solution containing GST is run through a column lined with immobilized glutathione, the GST binds to the glutathione, separating it from the rest of the solution. It is recommended to use near-neutral buffers for optimum binding of GST to the immobilized glutathione. Once bound, GST can be eluted with 10 mM glutathione, which is a mild eluent and aids retention of the fused protein function. 

Strep tag

* As it is 8 amino acids in length (WRHPQFGG), it is also unlikely to affect protein function, and it binds reversibly to the same pocket as biotin. This means that proteins fused to the Strep tag can be efficiently purified using streptavidin resins and eluted using biotin in mild buffer conditions.


Our Services:


KMD Bioscience is experienced in the preparation of labeled fusion proteins. Our scientific team has extensive practical experience in the usage of tags, and we have expressed and purified many peptides labeled fusion proteins in yeast and mammalian cells. Spacers can also be used to separate the label from the peptide if necessary. Experimental processes and quality are under strict control. Products delivered are supported by:  

-- HPLC chromatogram

-- Mass spec analysis

-- Synthesis report

-- Certificate of Analysis


How to Order?

If you have any questions regarding our services or products, please feel free to contact us by E-mail: or Tel: +86-400-621-6806;