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FRET

Our FRET pairs have a broad range of Förster distances from 40 to 80 Angstrom. Examples of representative Seta dye FRET pairs with calculated Förster distances, excitation and emission wavelength of representative donors and acceptors are listed in the Table below.

 

Representative Seta dye FRET pairs:

 

DonorAcceptorFörster Radius
(Å)
Excitation Wavelength
[nm]
Emission Wavelengths [nm]
DonorAcceptor
68 – 70* 750 780
78 – 80* 633 – 650 695 780
70 – 75* 633 – 650 695
66 – 71* 633 – 650 670 780
71 – 75* 633, 635 695
55 – 65* 633 – 650 650 693
47 – 57* 633 – 650 670
50 – 58* 532 571 650
48 – 53* 532 571 648
44 – 49* 532 571 695
43 – 48* 532 571 693
Seta-750 (K8-7522) 43 – 49* 532 571 780
34 – 40* 532 571
62 – 70* 405 693 780
44 – 53* 404 520 571

* Varies with Q.Y. of the donor

We also encourage you to try out our free SETA-FRET software package for the calculation of Förster distances and overlap integrals.
Please contact us for specific FRET pairs with customized Förster Distances.

 

FRET is a process where energy from a luminescent molecule (the donor) that is in its electronically excited state is transferred to an acceptor molecule by dipole-dipole interaction. FRET occurs when donor and acceptor molecules are in close proximity (usually within 10 to 80 Angstroms). The acceptor molecule can either be another fluorescent dye or a non-fluorescent molecule. There are several parameters that play an important role for FRET to occur:

1) The absorption spectrum of the acceptor molecule must overlap the emission spectrum of the donor characterized by the overlap integral (J).

2) The orientation between the donor and acceptor molecule plays only a role for fixed donor and acceptor pairs, for free rotating donor acceptor pairs it can be considered a constant.

3) The quantum yield of the donor and the extinction coefficient of the acceptor.

 clip3

Plot showing the energy transfer between a Seta-633 (donor)-labeled antibody and a Seta-670 (acceptor)-labeled antigen. With increasing amounts of the antigen the donor fluorescence decreases and at the same time the acceptor fluorescence increases

 

Another characteristic parameter for a given FRET pair is the so called Förster Distance (R0). It is defined as the distance with a 50% energy transfer efficiency. The FRET efficiency drops dramatically as the distance between donor and acceptor exceeds the Förster distance, decreasing by the inverse sixth power of the distance between the donor and acceptor.

FRET is presently one of the most powerful technologies for studying molecular interactions in cellular environments. The 6th power dependence on the spatial separation of donor-acceptor pairs provides an extremely sensitive tool for the detection of protein interactions and even small conformational changes. The most precise way of measuring FRET is to measure the fluorescence lifetime of the donor. Only measurement of the donor fluorescence lifetime can reveal the details of the donor-acceptor distance distribution, dynamic changes of the distance, and the fraction of unlabeled acceptors. The energy transfer efficiency (E) represents the ratio of the photons transferred to the acceptor and the total of the absorbed photons by the donor.

FRET is highly efficient if the donor and acceptor are positioned within the Förster distance, which is typically 30-60 Angstroms. FRET is commonly used as a tool in automated real-time hybridization assays and PCR monitoring. FRET-based probes are also used to monitor DNA interactions in living cells and other applications such as:

Homogeneous Assays
Flow Cytometry
2P-FRET imaging

 

Dyes for Förster Resonance Energy Transfer Applications:

Excitation Light Sources Characteristics
Product Number
(Specs Sheet)
Product Name
(Product Info)
Target Group 380 405 436 488 532 594 635 650 680 700 750 780 Medium λ abs
[nm]
ε
[M –1
cm–1]
λ em
[nm]
QY
[%]
FLT
[ns]
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K1-204
K1-204
SeTau-380-NHS
SeTau-380-NHS
NH2 Water 270 23800 480 56 32.5
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K1-204
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K5-3222
K5-3222
Seta-580-NHS
Seta-580-NHS
NH2 PB 7.4 578 90000 602 55
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K5-3222
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K7-1500
K7-1500
Q535
Q535
Toluene 542 15000
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K7-1500
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K7-547
K7-547
SeTau-405-NHS
SeTau-405-NHS
NH2 PB 7.4 405 13800 518 80 9.3
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K7-547
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K7-567
K7-567
SeTau-405-Azide
SeTau-405-Azide
triple-CC PB 7.4 405 13800 518 80 8
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K7-567
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K8-1342
K8-1342
Seta-670-NHS
Seta-670-NHS
NH2 PB 7.4 667 180000 688 7 0.42
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K8-1342
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K7-545
K7-545
SeTau-425-NHS
SeTau-425-NHS
NH2 PB 7.4 425 4200 545 39 26.2
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K7-545
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K8-1346
K8-1346
Seta-670-Azide
Seta-670-Azide
triple-CC PB 7.4 667 180000 686 7 0.42
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K8-1346
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K8-1357
K8-1357
Square-680-NHS
Square-680-NHS
NH2 MeOH 668 208000 690 10
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K8-1357
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K8-1384
K8-1384
Seta-700-NHS
Seta-700-NHS
NH2 PB 7.4 687 177000 703 6
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K8-1384
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K7-1510
K7-1510
Q435
Q435
Toluene 435 15900 0 0
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K7-1510
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K8-1626
K8-1626
Seta-633-di-NHS
Seta-633-di-NHS
NH2 PB 7.4 635 192000 644 12 0.7
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K8-1626
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K8-1641
K8-1641
Seta-632-Maleimide
Seta-632-Maleimide
SH PB 7.4 633 270000 642 5
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K8-1641
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K8-1642
K8-1642
Seta-632-NHS
Seta-632-NHS
NH2 PB 7.4 632 280000 641 6 0.42
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K8-1642
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K8-1649
K8-1649
SQ-740-NHS
SQ-740-NHS
NH2 PB 7.4 740 44000 0 0
Product Number
K8-1649
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K8-1663
K8-1663
Seta-633-NHS
Seta-633-NHS
NH2 PB 7.4 633 250000 644 7 0.25
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K8-1663
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K8-1672
K8-1672
Seta-646-NHS
Seta-646-NHS
NH2 PB 7.4 646 207000 656 10 0.38
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K8-1672
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K8-1682
K8-1682
Seta-660-di-NHS
Seta-660-di-NHS
NH2 PB 7.4 661 220000 672 11 0.9
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K8-1682
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K8-1696
K8-1696
Seta-633-Azide
Seta-633-Azide
triple-CC PB 7.4 633 250000 644 7 0.25
Product Number
K8-1696
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K8-1902
K8-1902
SQ-565-NHS
SQ-565-NHS
NH2 Water 560 22000 0 0
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K8-1902
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K8-1922
K8-1922
SQ-780-NHS
SQ-780-NHS
NH2 MeOH 782 115000 0 0
Product Number
K8-1922
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K8-3335
K8-3335
Seta-555-NHS
Seta-555-NHS
NH2 PB 7.4 555 155000 570 7
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K8-3335
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K8-3345
K8-3345
Seta-555-DBCO
Seta-555-DBCO
N3 PB 7.4 555 155000 570 7
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K8-3345
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K8-3346
K8-3346
Seta-555-Azide
Seta-555-Azide
triple-CC PB 7.4 555 155000 570 7
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K8-3346
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K8-5036
K8-5036
Seta-650-Maleimide
Seta-650-Maleimide
SH PB 7.4 652 200000 672 28
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K8-5036
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K8-5045
K8-5045
Seta-650-DBCO
Seta-650-DBCO
N3 PB 7.4 653 200000 674 28 1
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K8-5045
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K8-5046
K8-5046
Seta-650-Azide
Seta-650-Azide
triple-CC PB 7.4 651 200000 671 28 1
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K8-5046
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K8-7045
K8-7045
Seta-750-DBCO
Seta-750-DBCO
N3 PB 7.4 754 234000 782 21
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K8-7045
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K8-7046
K8-7046
Seta-750-Azide
Seta-750-Azide
triple-CC PB 7.4 750 200000 779 22
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K8-7046
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K8-7055
K8-7055
Seta-780-NHS
Seta-780-NHS
NH2 PB 7.4 777 215000 807 1.2
Product Number
K8-7055
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K9-4119
K9-4119 new
SeTau-665-NHS
SeTau-665-NHS
NH2 PB 7.4 664 160000 712 53 3.1
Product Number
K9-4119
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K9-4142
K9-4142
SeTau-647-di-NHS
SeTau-647-di-NHS
NH2 PB 7.4 650 200000 694 65 3.2
Product Number
K9-4142
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K9-4148
K9-4148
SeTau-647-Maleimide
SeTau-647-Maleimide
SH PB 7.4 648 200000 692 63 3.2
Product Number
K9-4148
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K9-4149
K9-4149
SeTau-647-NHS
SeTau-647-NHS
NH2 PB 7.4 649 200000 695 61 3.2
Product Number
K9-4149
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K8-3402
K8-3402
Zy3-NHS
Zy3-NHS
NH2 PB 7.4 549 150000 564 4 0.3
Product Number
K8-3402
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K8-5402
K8-5402
Zy5-NHS
Zy5-NHS
NH2 PB 7.4 647 250000 665 27 1
Product Number
K8-5402
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K8-5422
K8-5422
Zy5.5-NHS
Zy5.5-NHS
NH2 PB 7.4 676 190000 694 23 1
Product Number
K8-5422
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K8-3403
K8-3403
Zy3-Maleimide
Zy3-Maleimide
SH PB 7.4 549 150000 564 4 0.3
Product Number
K8-3403
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K8-5403
K8-5403
Zy5-Maleimide
Zy5-Maleimide
SH PB 7.4 647 250000 665 27 1
Product Number
K8-5403
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K8-5423
K8-5423
Zy5.5-Maleimide
Zy5.5-Maleimide
SH PB 7.4 676 190000 694 23 1
Product Number
K8-5423
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K8-1388
K8-1388
Seta-700-di-NHS
Seta-700-di-NHS
NH2 PB 7.4 688 180000 704 11
Product Number
K8-1388
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K8-1341
K8-1341
Seta-670-Maleimide
Seta-670-Maleimide
SH PB 7.4 667 180000 688 7
Product Number
K8-1341
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$0.00
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K8-1671
K8-1671
Seta-646-Maleimide
Seta-646-Maleimide
SH PB 7.4 647 210000 657 8
Product Number
K8-1671
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$0.00
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K4-205
K4-205 new
Seta-375-NHS
Seta-375-NHS
NH2 PB 7.4 372 24500 476 86 3.1
Product Number
K4-205
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K7-548
K7-548
SeTau-405-Maleimide
SeTau-405-Maleimide
SH PB 7.4 405 13800 518 51 9.1
Product Number
K7-548
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cl-APC
cl-APC
Crosslinked APC
Crosslinked APC
PB 7.4 650 700000 662
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cl-APC
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R-PE
R-PE
Lyophilized R-PE
Lyophilized R-PE
PB 7.4 565 1960000 573
Product Number
R-PE
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K8-7522
K8-7522
Seta-750-NHS
Seta-750-NHS
NH2 PB 7.4 753 230000 780 14
Product Number
K8-7522
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$0.00
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K8-3003
K8-3003 new
Seta-470-Maleimide
Seta-470-Maleimide
SH Water 469 50000 521 1.9
Product Number
K8-3003
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$0.00
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K8-7402
K8-7402
Zy7-NHS
Zy7-NHS
NH2 PB 7.4 749 200000 774 13 0.57
Product Number
K8-7402
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K7-544
K7-544
SeTau-425-Maleimide
SeTau-425-Maleimide
SH PB 7.4 425 4200 545 39 26.2
Product Number
K7-544
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K4-225
K4-225 new
Seta-385-NHS
Seta-385-NHS
NH2 PB 7.4 384 25000 512 78
Product Number
K4-225
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