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:

 

Donor Acceptor Förster Radius
(Å)		 Excitation Wavelength
[nm]		 Emission Wavelengths [nm]
Donor Acceptor
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.

 The energy transfer (FRET) between a Seta-633 (donor)-labeled antibody and a Seta-670 (acceptor)-labeled antigen

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]		 Buy
                   
K1-204
K1-204
SeTau-380-NHS
SeTau-380-NHS 		NH2 • • Water 270 23,800 480 56 32.5
K5-3222
K5-3222
Seta-580-NHS
Seta-580-NHS 		NH2 • PB 7.4 578 90,000 602 55
K7-1500
K7-1500
Q535
Q535 		• • • • • • Toluene 542 15,000
K7-547
K7-547
SeTau-405-NHS
SeTau-405-NHS 		NH2 • • PB 7.4 405 13,800 518 80 9.3
K7-567
K7-567
SeTau-405-Azide
SeTau-405-Azide 		triple-CC • • PB 7.4 405 13,800 518 80 9.3
K8-1342
K8-1342
Seta-670-NHS
Seta-670-NHS 		NH2 • • • • PB 7.4 667 180,000 688 7 0.42
K7-545
K7-545
SeTau-425-NHS
SeTau-425-NHS 		NH2 • • • PB 7.4 425 4,200 545 39 26.2
K8-1346
K8-1346
Seta-670-Azide
Seta-670-Azide 		triple-CC • • • • PB 7.4 667 180,000 686 7
K8-1357
K8-1357
Square-680-NHS
Square-680-NHS 		NH2 • • • • MeOH 668 208,000 690 10
K8-1384
K8-1384
Seta-700-NHS
Seta-700-NHS 		NH2 • • • • • PB 7.4 687 177,000 703 6
K7-1510
K7-1510
Q435
Q435 		• • • Toluene 435 15,900 0 0
K8-1641
K8-1641
Seta-632-Maleimide
Seta-632-Maleimide 		SH • PB 7.4 633 270,000 642 5
K8-1642
K8-1642
Seta-632-NHS
Seta-632-NHS 		NH2 • PB 7.4 632 280,000 641 6
K8-1649
K8-1649
SQ-740-NHS
SQ-740-NHS 		NH2 • • • • PB 7.4 740 44,000 0 0
K8-1663
K8-1663
Seta-633-NHS
Seta-633-NHS 		NH2 • • PB 7.4 633 250,000 644 7 0.25
K8-1672
K8-1672
Seta-646-NHS
Seta-646-NHS 		NH2 • PB 7.4 646 207,000 656 10 0.38
K8-1682
K8-1682
Seta-660-di-NHS
Seta-660-di-NHS 		NH2 • • PB 7.4 661 220,000 672 11 0.9
K8-1696
K8-1696
Seta-633-Azide
Seta-633-Azide 		triple-CC • • PB 7.4 633 250,000 644 7
K8-1902
K8-1902
SQ-565-NHS
SQ-565-NHS 		NH2 • • Water 560 22,000 0 0
K8-1922
K8-1922
SQ-780-NHS
SQ-780-NHS 		NH2 • • • • • • • MeOH 782 115,000 0 0
K8-3335
K8-3335
Seta-555-NHS
Seta-555-NHS 		NH2 • PB 7.4 555 155,000 570 7
K8-3345
K8-3345
Seta-555-DBCO
Seta-555-DBCO 		N3 • PB 7.4 555 155,000 570 7
K8-3346
K8-3346
Seta-555-Azide
Seta-555-Azide 		triple-CC • PB 7.4 555 155,000 570 7
K8-5036
K8-5036
Seta-650-Maleimide
Seta-650-Maleimide 		SH • • PB 7.4 652 200,000 672 28
K8-5045
K8-5045
Seta-650-DBCO
Seta-650-DBCO 		N3 • • PB 7.4 653 200,000 674 28
K8-5046
K8-5046
Seta-650-Azide
Seta-650-Azide 		triple-CC • • PB 7.4 651 200,000 671 28
K8-7045
K8-7045
Seta-750-DBCO
Seta-750-DBCO 		N3 • • • PB 7.4 754 234,000 782 21
K8-7046
K8-7046
Seta-750-Azide
Seta-750-Azide 		triple-CC • • • PB 7.4 750 200,000 779 22
K8-7055
K8-7055
Seta-780-NHS
Seta-780-NHS 		NH2 • • • PB 7.4 777 215,000 807 1.2
K9-4119
K9-4119
SeTau-665-NHS
SeTau-665-NHS 		NH2 • • • PB 7.4 664 160,000 712 53 3.1
K9-4142
K9-4142
SeTau-647-di-NHS
SeTau-647-di-NHS 		NH2 • • PB 7.4 650 200,000 694 65 3.2
K9-4148
K9-4148
SeTau-647-Maleimide
SeTau-647-Maleimide 		SH • • PB 7.4 648 200,000 692 45 3.2
K9-4149
K9-4149
SeTau-647-NHS
SeTau-647-NHS 		NH2 • • PB 7.4 649 200,000 695 61 3.2
K8-3402
K8-3402
Zy3-NHS
Zy3-NHS 		NH2 • PB 7.4 549 150,000 564 4 0.3
K8-5402
K8-5402
Zy5-NHS
Zy5-NHS 		NH2 • PB 7.4 647 250,000 665 27 1
K8-5422
K8-5422
Zy5.5-NHS
Zy5.5-NHS 		NH2 • • • PB 7.4 676 190,000 694 23 1
K8-3403
K8-3403
Zy3-Maleimide
Zy3-Maleimide 		SH • PB 7.4 549 150,000 564 4 0.3
K8-5403
K8-5403
Zy5-Maleimide
Zy5-Maleimide 		SH • PB 7.4 647 250,000 665 27 1
K8-5423
K8-5423
Zy5.5-Maleimide
Zy5.5-Maleimide 		SH • • • PB 7.4 676 190,000 694 23 1
K8-1388
K8-1388
Seta-700-di-NHS
Seta-700-di-NHS 		NH2 • • • • • PB 7.4 688 180,000 704 11
K8-1341
K8-1341
Seta-670-Maleimide
Seta-670-Maleimide 		SH • • • • PB 7.4 667 180,000 688 7
K8-1671
K8-1671
Seta-646-Maleimide
Seta-646-Maleimide 		SH • PB 7.4 647 210,000 657 8
K4-205
K4-205
Seta-375-NHS
Seta-375-NHS 		NH2 • PB 7.4 372 24,500 476 86 3.1
K7-548
K7-548
SeTau-405-Maleimide
SeTau-405-Maleimide 		SH • • PB 7.4 405 13,800 518 51 9.1
cl-APC
cl-APC
Crosslinked APC
Crosslinked APC 		• • • PB 7.4 650 700,000 662
R-PE
R-PE
Lyophilized R-PE
Lyophilized R-PE 		• • PB 7.4 565 1,960,000 573
K8-7522
K8-7522
Seta-750-NHS
Seta-750-NHS 		NH2 • • • PB 7.4 753 230,000 780 14
K8-3003
K8-3003
Seta-470-Maleimide
Seta-470-Maleimide 		SH • • • Water 469 50,000 521 1.9
K8-7402
K8-7402
Zy7-NHS
Zy7-NHS 		NH2 • • • PB 7.4 749 200,000 774 13 0.57
K7-544
K7-544
SeTau-425-Maleimide
SeTau-425-Maleimide 		SH • • • PB 7.4 425 4,200 545 39 26.2
K4-225
K4-225
Seta-385-NHS
Seta-385-NHS 		NH2 • PB 7.4 384 25,000 512 78

 

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