LifeTein Modifications: Fluorophores

Usually, the dyes such as Biotin, FITC can be introduced either N-terminally or C-terminally. We recommend N terminus modification for higher success, shorter turnaround time and easier operation from LifeTein. The reason is that the peptides are synthesized from C terminus to N terminus. So the N terminus modification is the last step in the SPPS protocol and no more specific coupling steps are required. On the contrary, the C terminus modification needs additional steps and is usually more complex.

Most dyes are large aromatic molecules so the incorporation of such bulky molecules may help to avoid interactions between the label and the peptide. This will help to maintain the peptide conformation and its biological activity. It is recommended to include a flexible spacer such as Ahx, which is a 6 carbon linker, to make the fluorescent label more stable. Otherwise FITC could be easily linked to a cysteine thiol moiety or the amino group of lysine at any position.

Click to see the comprehensive fluorophore list including absorption and emission peak values.

Case Study:

Client requested a very hydrophobic 68 amino acid peptide (85% purity) with FITC modification at the N terminus. The peptide was successfully synthesized in 4 weeks.

HPLC Results:

MS Results:

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