Fluorescently Labeled Peptides and Amino Acids

Bachem AG is a leading provider of the fluorescently labeled peptides and amino acids that are finding increasing applications in biochemical and biological studies, both in vitro and in living cells.

Typical applications for these labeled peptides include the Fluorescence (or Förster) Resonance Energy Transfer (FRET) analysis of receptor-ligand interactions, protein-protein interactions and the cleavage of substrate molecules.

Bachem can now supply peptides labeled with Tide Fluor^™ dyes and, optional, Tide Quencher^™ dye-labeled peptides that combine the cost advantages of classic fluorescent tags while out-performing proprietary dyes.

Peptides and Amino Acids Labeled with Dyes and Quenchers

Fluorescent labeled probes and quenchers must meet a series of high technical and scientific requirements that include efficient excitation light absorption and high yield of energy emission by the donor label (dye) as well as a good energy absorption by the acceptor (quencher), in order to reach a high signal-to-noise ratio. This is particularly important under physiological conditions that demand low dye concentrations. Furthermore, the dyes should have a high photo-stability, in order to minimize bleaching caused by exposure with high light intensities, used for example in microscopy. The choice of fluorescent dye and quencher is also subject to cost pressures since proprietary dyes that can fulfill all the scientific requirements are usually expensive.

Bachem has now extended its product portfolio with Tide Fluor^™ dyes that can be combined with Tide Quencher^™ dye-labeled peptides, both developed by partner AAT Bioquest, Inc. These combine the cost advantages of classic fluorescent tags with the performance of proprietary dyes, even outperforming the latter in the relevant characteristics.

Tide Fluor^™ Dyes promote more efficient absorption of excitation light from common light sources with significantly stronger fluorescence and higher photo-stability, than most conventional or proprietary dyes. Furthermore, Tide Fluor^™ dyes are available with improved water solubility (TFWS).

Also in comparison to the majority of classic and proprietary quenchers, Tide Quencher™ labels possess significantly higher absorption strength and superior quenching efficiency and are also available with improved TFWS.

Tide Fluor dye and Tide Quencher dye-labled peptides

Tide Fluor^™ dyes and Tide Quencher^™ dye labeled peptides are available as:

• Carboxylic acids
• Maleimido-, azido- and alkyne- derivatives
• Active esters (NHS)
• Amines

They include the following new Bachem products:

For optimum results in FRET analysis, the Tide Fluor^™ dyes should be combined with the proprietary quenchers of the Tide Quencher^™ (TQ) range. The emission spectra of the Tide Fluor^™ dyes have a great overlap with the excitation spectra of the recommended Tide Quencher^™ acceptors, leading to an efficient quenching process. Suggested combinations of Tide Tide Fluor^™ dyes with Tide Quencher^™ peptides and their compatibility with other dyes are listed in Tables 1 and 2 below.

The Bachem Custom Synthesis Team can provide detailed advice on custom peptide modification of dye labeled peptides.

Use of Tide Quencher^™ Labels in FRET analysis

Bachem has proved efficacy of Tide Fluor fluorescent dye in a a Förster Resonance Energy Transfer (FRET) analysis of uptake of Amyloid β-Protein (1-42) by J774 macrophages, obtained from BALB/c mice. The Amyloid β-Protein (1-42) was labeled with Tide Fluor^™ 5WS fluorescent dye to enable visualization. The cells were displayed in bright field imaging overlaid with the green fluorescent channel of the peptides.

Results were captured on video showing fluorescent particle aggregates appearing and the cells starting to internalize them with subsequent particle aggregates becoming visible intracellularly. Ultimately, every cell has taken up some particles that are visible as little green spots inside the cells. As uptake by the macrophages continues, green particles further accumulate within the cells and are visualized as green material intracellularly (see Resources below).

Resources

Click on Aβ42 Tide Fluor™ 5 WS Uptake to watch video.
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