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Intensity Probes

Excitation Light Sources Characteristics Characteristics
Product Number
(Specs Sheet)
Product Name
(Product Info)
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]
Medium λ abs
[nm]
ε
[M–1
cm–1]
λ em
[nm]
QY
[%]
FLT
[ns]
Buy
                             
K35
K35
K35
K35
Toluene 410 10000 495 60 EtOH 430 13200 552 0.01
K6-207
K6-207
3-DAB
3-DAB
Toluene 445 9700 582 43 EtOH 460 8600 665 22 4.0
K6-208
K6-208
2-DAB
2-DAB
Toluene 464 3600 551 31 EtOH 480 2900 670 1.1
K8-1350
K8-1350
Square-670-Carboxy
Square-670-Carboxy
PB 7.4 656 676 1.7 0.29 6g/L BSA 673 693 29
K8-1351
K8-1351
Square-660-Carboxy
Square-660-Carboxy
PB 7.4 657 182000 676 3 0.27 2g/L BSA 679 182000 696 45 3.56
K8-1355
K8-1355
Square-680-Carboxy
Square-680-Carboxy
PB 7.4 654 138000 670 1 1g/L BSA 688 168000 708 62
K8-1440
K8-1440
Square-670
Square-670
pH 7.4 659 677 0.09 1 g/L BSA 683 702 50
K8-1443
K8-1443
Square-730
Square-730
CHCl3 728 166000 757 46 1g/L BSA 722 745
K8-1500
K8-1500
Square-655
Square-655
PB 7.4 622 177000 644 0.09 1 g/L BSA 652 188,000 672 80
K9-4145
K9-4145
SeTau-633-Ethyl-Ester
SeTau-633-Ethyl-Ester
CHCl3 634 88000 683 68
K9-4150
K9-4150
SeTau-647
SeTau-647
PB 7.4 647 211000 693 59 3.1 PB 7.4 647 211000 693 59 3.1
K8-3010
K8-3010 new
Square-460
Square-460
PB 7.4 467 50000 515 0.9 6g/L BSA 469 512 8.6
K8-1405
K8-1405
Square-650-pH-Carboxy
Square-650-pH-Carboxy
PB 5.6 653 135000 671 16 1.17 pH 9.0 535 48000 663 9 0.53
K8-1610
K8-1610
Square-635-Carboxy
Square-635-Carboxy
pH 7.4 634 180000 646 9 pH 12.0 520 - - -
K8-1665
K8-1665
Seta-635-pH-di-Carboxy
Seta-635-pH-di-Carboxy
PB 7.4 640 188000 656 33 1.8 pH 12.0 519 - - -
K8-1365
K8-1365
Seta-670-pH-di-Carboxy
Seta-670-pH-di-Carboxy
PB 6.0 672 93000 694 19 pH 11.5 535 - - -
K6-1037
K6-1037
K37
K37
Toluene 434 29500 540 49 Cholesterol in water 540
K8-2100
K8-2100 new
YOSeta-1 (1mM solution in DMSO)
YOSeta-1 (1mM solution in DMSO)
dsDNA 492 98800 509 52
K8-1389
K8-1389 new
Seta-700-NHS
Seta-700-NHS
PB 7.4 688 162000 703 14 IgG D/P=1 694 710 18

new Staining of double-stranded DNA: YOSeta-1 is a cell-impermeant fluorescent dye used for staining of double-stranded DNA (same dye as YOYO® 1). The free YOSeta-1 dye has a very low fluorescence quantum yield but the QY increases several thousand times upon binding to double-stranded DNA (see specs sheet). The probe is available as a 1 mM solution in DMSO.

Absorption and emission spectrum of YOSeta-1 in presence of dsDNA

Absorption and emission spectrum of YOSeta-1 in presence of dsDNA

Measurement of changes in lipid bilayer hydration in cells: Square-670 is as an effective red emitting fluorescent probe for examining membrane-related processes, e.g. drug-influenced changes in bilayer hydration [18​].

Protein analysis: Dyes such as Square-655 and Square-680 exhibit a substantial fluorescence intensity increase (up to 190 times) in the presence of BSA. Fluorescence enhancement of the dyes in the presence of other albumins (HSA and ovalbumin) is lower (40 times). The large fluorescence enhancement in presence of proteins makes them valuable dyes for the visualization and quantification of proteins in gel-electrophoresis applications.

Fluorescence intensity of Square-655 vs. BSA concentration
Fluorescence intensity of Square-655 vs.
BSA concentration

Square dyes are the most sensitive dyes on the market for the detection of proteins. The protein-bound forms of Square dyes exhibit absorption and emission maxima between 640 and 750 nm, very high extinction coefficients between 104,000–208,000 M–1cm–1 and quantum yields as high as 80%.

Squaraine-Rotaxane imaging probes for live and fixed cells: Our fluorescent rotaxane probes exhibit extremely high chemical and photochemical stability and are therefore well suited for imaging applications. They also exhibit very high 2-photon action cross sections in the order of several thousand GM.

Z-projection of a neuron filled with a squaraine rotaxane-labeled peptide
Z-projection of a neuron filled with a squaraine rotaxane-labeled peptide

SeTau-633 is a carboxylic acid ethyl ester derivative that passively penetrates cell membranes. Once inside these residue are hydrolyzed by esterases thereby forming carboxyl groups that are cell-impermeable.

SeTau-647 is a highly water-soluble fluorescent probe with several negative charges and therefore will not passively penetrate the cell-menbrane. This probe is very photostable and has a quantum yield of 60% in water.

Reactive versions (NHS-esters and maleimides) for covalent attachment to different biomolecules to target specific cellular locations for in vitro and in vivo optical imaging are also available. Images stained with these probes are stable for hundreds of hours:

[B.D. Smith et al. Squaraine Rotaxanes: Superior Substitutes for Cy-5 in Molecular Probes for Near-Infrared Fluorescence Cell Imaging. Angew. Chem. 2007, 119, 5624 –5627].

pH-measurement in cells: Probes such as Square-650-pH-Carboxy exhibit pKa’s in the physiologically relevant pH range and are therefore useful to measure the intercellular pH changes in cells. For more information about this dye we refer you to the specs sheet of Square-650-pH-Carboxy  and the published literature.

Fluorescence spectrum of Square-650-pH-Carboxy vs. pH
Fluorescence spectrum of Square-650-pH-Carboxy vs. pH
Titration curve for Square-650-pH-Carboxy
Titration curve for Square-650-pH-Carboxy

Em-vs-pH

Titration curves for Square-635Seta-635-pH and Seta-670-pH in presence of dsDNA

Additional pH-probes with pKa's in the alkaline pH-range are listed under pH-sensing applications.

Albumin Determination: K35 and Square-655 are a fluorescent probes for determination of albumin binding sites in plasma and serum [19, 20]. The fluorescence intensity of these probes significantly increases in presence of albumin.

Probes for the evaluation of cryoprotection:

Cryoprotectors (CPs) are important reagents that help to prevent biological matter such as blood, tissues and cells from degradation during low-temperature storage. Fluorescent dyes are useful tools to investigate the interaction of CPs with biological species. Long-term and low temperature storage of cells is an important process for biomedical research and transplantation medicine. Biomembranes are cellular structures that are strongly affected by the freeze-thawing process.

The freeze-thawing experiments with yeast cells using cryoprotectors have demonstrated that 2-DAB and 3-DAB are fluorescent probes that enable not only to distinguish damaged from undamaged cells, but also allow quantitative estimation of the extent of damage by the cryogenic treatment. These fluorescent probes are therefore very useful to quickly assess the effects of cryopreservation on cells using fluorescence imaging.

Saccharomyces Cerevisiae cells stained with 3-DAB before undergoing the cycle cryoprotection
Saccharomyces Cerevisiae cells stained with 3-DAB
before undergoing the cycle cryoprotection
Saccharomyces Cerevisiae cells stained with dye 3-DAB after freeze-thawing undergoing the cycle cryoprotection. Partially damaged cells exhibit brighter fluorescence as compared to living cells
Saccharomyces Cerevisiae cells stained
with dye 3-DAB after freeze-thawing undergoing
the cycle cryoprotection. Partially damaged
cells exhibit brighter fluorescence as
compared to living cells

See also Fluorescence Imaging, NIR Fluorescence Imaging and Fluorescence Lifetime Imaging.

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