Affinity tags such as biotin can be used for
- The detection of suitably tagged peptides (e.g. with labeled antibodies)
- The separation of tagged peptides from untagged ones (e.g. with tethered antibodies)
The tags can be small organic molecules like biotin (which binds strongly and non-covalently to streptavidin) or a short peptide sequence. The most prominent examples for peptide sequences used as tags are epitope tags like the Flag tag, the HA tag and the Myc tag. For all tags, antibodies are commercially available. See below for respective sequences.
JPT routinely synthesizes tagged peptides carrying various tags. The tags are usually attached at the N-terminus or the C-terminus (via lysine or cysteine), but in principle can be positioned anywhere. All tags can be separated from the peptide by a variety of different so called linkers or spacer molecules of varying length and polarity. If desired, the linkers can also be made cleavable, e.g. by reduction of sensitive disulfide bonds. Have a look at a list of available linker / spacer / PEGylations. Here is a representation of frequently incorporated tags.
|Affinity Tag||Structure / Sequence||Binding Partner / Comment|
(oxidation resistant, reversible)
|Flag tag||DYKDDDDK||Anti flag antibody|
|HA tag||YPYDVPDYA||Anti HA antibody|
|Myc tag||EQKLISEEDL||Anti Myc antibody|
For intracellular delivery, peptides can be attached to cell-penetrating peptides (CPPs). Examples of frequently used CPPs are the poly-Arg or the Tat-sequence. Cell penetrating peptides can be attached to many positions within a peptide drug or to small molecules.
|Tat (47-57)||YGRKKRRQRRR||Cell-penetrating peptide|
JPT is also able to provide you with a wide range of reactive labels attached to peptides. Examples are the introduction of
- Azides (reaction with alkines – click chemistry)
- Maleimides (reaction with thiols, e.g. Cys)
- Thiols (reaction with maleimides)
- Cys(Pys/Npys) (reaction with thiols to form disulfides)
Some representative structures are shown here:
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