Seta-633 - a NIR fluorescence lifetime label for low-molecular-weight analytes.

We describe the photophysical properties of Seta-633, a commercially available near-infrared (NIR) dye, and its use as a fluorescent label to study the interaction between low-molecular-weight analytes and proteins using fluorescence lifetime as the readout parameter. In a model assay, we demonstrate that a biotinylated Seta-633 tracer binds to antibiotin with high specificity. Importantly, the lifetime of Seta-633-biotin increases about 1.

Near-infrared, dual-ratiometric fluorescent label for measurement of pH.

We describe the spectral properties of an amine-reactive, pH-sensitive, long-wavelength ratiometric fluorescent label having a pK(a) in the physiological pH range. The label exhibits its main absorption and emission in the near-infrared (NIR) region. On deprotonation, a blue shift of the excitation maximum is observed.