Lifetime 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
                             
K6-207
K6-207
3-DAB
3-DAB
Toluene 445 9,700 582 43 EtOH 460 8,600 665 22 4.0
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 7.4 657 182,000 676 3 0.27 2g/L BSA 679 182,000 696 45 3.56
K8-1405
K8-1405
Square-650-pH-Carboxy
Square-650-pH-Carboxy
PB 5.6 653 135,000 671 16 1.17 pH 9.0 535 48,000 663 9 0.53

Probes such as Square-660-Carboxy show large changes in FLT upon binding to either proteins or cell-surfaces. Square-660-Carboxy is water-soluble but with a strong affinity for hydrophobic regions of biomolecules. Its lifetime increases from 0.27 ns (free in solution) up to 3.56 ns in presence of 6 mg/mL BSA and 3.32 ns when covalently bound to BSA.

Comparison of the frequency responses of   Square-660-Carboxy before and after binding to BSA
Comparison of the frequency responses of
  Square-660-Carboxy before and after binding to BSA.
(τfree = 270 ps; τBSA bound = 3.32 ns)
Comparison of the intensity decays of Square-660-Carboxy before and after binding to BSA
Comparison of the intensity decays of
Square-660-Carboxy before and after binding to BSA.
(τfree = 270 ps; τBSA bound = 3.32 ns)

Square-650-pH-Carboxy is a NIR probe that exhibits a pKa around 7 and is therefore useful for measurement of pH changes in the physiologically relevant pH range from pH 6.5 to pH 8. Importantly both forms (protonated as well as unprotonated) are fluorescent and they exhibit different lifetimes which makes this compound also useful for lifetime-based applications (see Figure below). For more information about these dyes we refer you to the specs sheet of Square-650-pH-Carboxy and the published literature.

Frequency–response curves (phase angle and demodulation) of the Square-650-pH-IgG conjugate (D/P = 0.8) at pH 2.0 and pH 9.0
Frequency–response curves (phase angle and demodulation)
of the Square-650-pH-IgG conjugate (D/P = 0.8) at pH 2.0 and pH 9.0
pH dependent changes in Phase Angles of Square-650-pH at 100 MHz
pH dependent changes in Phase Angles
of Square-650-pH at 100 MHz

For more information about lifetime probes we refer you to lifetime applications.

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