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FRET Substrates

Full name of FRET is Fluorescence Resonance Energy Transfer, it is a distancedependent dipole-dipole interaction without the emission of a photon, which results in the transfer of energy from an initially excited donor molecule to an acceptor molecule. FRET allows the detection of molecular interactions in the nanometer range. We usually label FRET peptides with a donor molecule and an acceptor (quencher) molecule and in most cases, the donor and acceptor pairs are two different dyes. When the FRET is terminated (by separating donor and acceptor), we can detect an increase of donor fluorescence. When both the donor and acceptor dyes are fluorescent, the transferred energy is emitted as light of longer wavelength so that the intensity ratio change of donor and acceptor fluorescence can be measured. The transferred energy from a fluorescent donor is converted into molecular vibrations if the acceptor is a non-fluorescent dye (quencher). The fluorophore and quencher molecules must be close to each other (approximately 10-100 Å) and the absorption spectrum of the quencher must overlap with the emission spectrum of the fluorophore in order for efficient FRET quenching to take place. We need to compare carefully of the donor’s fluorescence spectrum with the quencher’s absorption spectrum when designing a donor-quencher FRET system. HongTide has extensive knowledge in the synthesis of peptide FRET substrates. We offer a wide range of FRET substrates to suit your research needs.

How FRET take place

FRET caspase-1 substrate

TR-FRET(Time-resolved FRET)
In TR-FRET, the donor molecule is a Lanthanide metal such as Europium (Eu) whose fluorescence is longer-lived than a conventional fluorophore instead of a fluorescent dye. It is characterized by a large stokes shift, providing a high signal-to-noise ratio due to minimal crosstalk between excitation and emission wavelengths. TR-FRET allows setting flexible, reliable and sensitive assays, adaptable to high-throughput, with fewer false positive/false negative results. Metal chelates such as DOTA, NOTA, etc. are usually to be used to binds to lanthanide metals. We can custom synthesize any dota-peptide for use in your other TR applications.
Table of Common FRET Pairs

DONOR (FLUOROPHORE)

Trp (Tryptophan)

Trp (Tryptophan)

Mca (7-Methoxycoumarin-4-yl)acetyl)

Abz (2-Aminobenzoyl)

Abz (2-Aminobenzoyl)

Abz (2-Aminobenzoyl)

EDANS (5-[(2-Aminoethyl) amino]naphthalene-1-sulfonic acid)

Lucifer Yellow

FITC (Fluorescein isothiocyanate)

Dansyl (5-(Dimethylamino) naphthalene-1-sulfonyl)

5-TAMRA (Carboxytetramethyl rhodamine)

Eu(III) Chelate

EM COLOR

EX (NM)

280nm

280nm

325nm

320nm

320nm

320nm

340nm

430nm

490nm

342nm

547nm

340nm

EM (NM)

360nm

360nm

392nm

420nm

420nm

420nm

490nm

520nm

520nm

562nm

573nm

613nm

ACCEPTOR (QUENCHER)

Dnp (2,4-Dinitrophenyl)

4-Nitro-Z (4-Nitro-benzyloxycarbonyl)

Dnp (2,4-Dinitrophenyl)

pNA (para-Nitroaniline)

3-Nitro-Tyr (3-Nitro-tyrosine)

4-Nitro-Phe (4-Nitro-phenylalanine)

Dabcyl (4-(4-Dimethylaminophenylazo)benzoyl)

Dabsyl (4-(4-Diethylaminophenylazo)-benzenesulfonyl)

Dnp (2,4-Dinitrophenyl)

4-Nitro-Phe (4-Nitro-phenylalanine)

QSY7

QSY-7

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