Dye to Peptide Conjugation

Peptides are short chain amino acids that perform numerous functions as chemical messengers, hormones, cellular mediators, highly specific stimulators and inhibitors, as well as novel therapeutic treatments for various diseases including Alzheimer’s and cancer. Due to the emerging solid-phase peptide synthesis technologies, synthetic peptides have now been widely used in biochemistry, molecular biology, and pharmaceutical areas. Dye-labeled peptides are powerful tools to investigate cellular structure, analyze receptor-ligand or protein-protein interactions, study cellular transport, and measure enzymatic activity via FRET analysis.

Tide Fluor™ Dyes

Our Tide Fluor™ dyes are superior peptide labeling dyes with improved characteristics for labeling and detection. The enhanced brightness, photostability and water solubility of Tide Fluor™ dyes significantly outperforms classic peptide labeling dyes and Alexa Fluor® dyes.

Tide Quencher™ Dyes

Tide Quencher™ dyes are non-fluorescent acceptors for synthesizing longer wavelength FRET probes. Displaying excellent FRET efficiency, Tide Quencher™ dyes are designed to pair with corresponding Tide Fluor™ dyes to guarantee optimum results in FRET analysis.

Classic Peptide Labeling Dyes

AAT Bioquest offers classic peptide labeling dyes in a variety of chemical reactivities, as well as conjugated to peptide substrates for enzyme activity assays. Choose from our comprehensive portfolio of:

  • Coumarin and coumarin derivatives
  • Fluorescein dyes
  • Rhodamine dyes
  • Cyanine dyes

FRET Donor/Acceptor Dyes

In addition to Tide Fluor™ and Tide Quencher™ FRET pairs, we offer various combinations of classic donor and acceptor dyes. Develop FRET peptides for measuring enzyme activity, receptor-ligand interactions, colocalization studies and much more.

Peptide Labeling Strategies

Labeled peptides can prepared by either modifying isolated peptides or by incorporating the label during solid-phase synthesis. Common strategies for labeling peptides with fluorophores include:

  1. Labeling during peptide synthesis – dyes that can withstand unblocking procedures can be incorporated onto the amino terminus of the peptide chain.
  2. N-terminal modification: N-terminus refers to the free amine group (-NH2) at the start of a protein or polypeptide chain. It can be modified co- or post-translationally using amine-reactive succinimidyl ester fluorophores.
  3. Lysine residues: the ε-amino group of lysine residues can be modified using amine-reactive succinimidyl ester fluorophores.
  4. C-terminal modification: C-terminus refers to the carboxyl group (-COOH) at the end of a protein or polypeptide chain. It can be modified post-translationally typically after C-terminal amidation.
  5. Synthetic peptides can be covalently labeled by thiol-reactive protein labels. Thiol-reactive protein labels may be used if a cysteine is available on the peptide chain.
  6. Unnatural amino acids could be incorporated in peptide chains during synthesis, and then labeled with dyes or other probes through bioorthogonal reactions, for example, azide and alkynes based reactions, and ketone-aldehyde reaction.


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