Overview

Fluorescent tags or probes are ideal for many imaging and diagnostic applications. Applications for fluorescent peptides range from the study of in vivo biomedical imaging, localization studies, peptide-protein interactions, enzyme activity assays, or development of novel disease models. Fluorochrome-conjugated peptides can be visualized by fluorescence microscopy or other fluorescence visualization techniques. Fluorophores can be covalently attached to either the N- or C-terminus, although conjugation to the N-terminus is recommended. Labeling can also be achieved indirectly by using a biotinylated amino acid.FRET pairs, consisting of an acceptor and quencher, can either be attached internally or externally. Internal attachment of FRET pairs is recommended for longer sequences.

  • Fluorescent Modifications

  • Applications

  • Case studies

Fluorescent Modifications for Peptides

GenScript offers numerous fluorescent tags for peptides, and our repertoire is being expanded continuously. Listed below are a few of our most commonly used modifications:

Name Excitation (nm) Emission (nm) Emission color Application Fields
7-Methoxycoumarin-4-acetic acid
328
393
Blue
In vitro imaging
Subcellular localization
Confocal microscopy
Flow cytometry
FITC-Ahx
494
521
Green
FAM
495
520
Green
Cy3
555
570
Yellow
5-Carboxytetramethylrhodamine (TMR)
542
568
Orange
Cy5
646
662
Red
Cy5.5
673
707
Near-infrared
In vitro imaging
Subcellular localization
In vivo optical imaging
Angiography
Cy7
750
773
Near-infrared

FRET pairs

Fluorescence resonance energy transfer (FRET) is a mechanism that describes the energy transfer between two fluorophores. Since FRET efficiency is partly based on distance between a donor and acceptor molecule, this technique is commonly used for studying enzyme efficiency, protein-protein interactions, or other molecular dynamics (Fig 1).

FRET mechanism

Fig 1. FRET mechanism for protease studies. When the peptide remains intact, the acceptor molecule will quench the donor molecule, and no fluorescence will be detected. If the sequence is cleaved by protease activity, the acceptor will no longer quench the donor, and a fluorescent signal will be detected.

Below are the most commonly used FRET pairs:

Donor Acceptor
Name
Excitation (nm)
Emission (nm)
Name
Excitation (nm)
Emission (nm)
Cy2
490
510
Cy3
555
570
FITC
494
521
TRITC
557
576
FAM
495
520
Cy3
555
570
FAM
495
520
Texas Red
589
615
FAM
495
520
Cy5
646
662
Cy3
555
570
Cy5
646
662
EDANS
335
493
DABCYL
453
-
Glu(EDANS)-NH2
335
493
DABCYL
453
-
MCA
328
393
DNP
348
-
Abz
330
420
DNP
348
-
Abz
330
420
Tyr (3-NO2)
360
-

Quotations and Ordering

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