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Viscous HR™

Viscous HR™ (High Resolution) is a modestly water soluble viscosity probe specifically designed for fluorescence-based viscosity measurements in aqueous media. Viscous HR™ shows both a fluorescence emission and lifetime dependence on solution / media viscosity (and subsequently the temperature dependence on viscosity), making it ideal for your aqueous viscosity applications, particularly for water-like viscosity values, i.e, 0.4 – 2 cP and beyond.


The lifetime of Viscous HR™ is also viscosity dependent, making it ideal for FLIM, Fluorescence Lifetime Imaging Microscopy.

Viscous HR

Figure 1. (A) Absorption spectrum recorded for Viscous HR™ dissolved in water and in glycerol. (B) Excitation-Emission intensity Map (EEM) recorded for Viscous HR™ dissolved in glycerol at +5 °C.


Figures 1A shows the absorbance spectrum of Viscous HR™ in both water and glycerol. The probe can readily be excited from 260-400 nm.

Figure 1B shows the 3D spectra (excitation-emission intensity map) of Viscous HR™ in air equilibrated glycerol at 5 °C. The emission maxima is centered around 440 nm.

Similar to Ursa BioScience’s other viscosity probes, the emission intensity increases as the viscosity of solution (or cell, extra cellular media, polymer solution etc) also increases, which is also readily changing as a function of temperature Figures 2A. Figure 2B shows the linear response of Viscous HR™ emission intensity to water viscosity. The excitation wavelength was 320 nm.

Viscous HR

Figure 1. (A)Emission spectra recorded for Viscous HR™ dissolved in glycerol at temperatures from +5 °C to +70 °C. The excitation wavelength was 320 nm. (B) Integrated fluorescence spectra, as shown in panel A, plotted as function of glycerol viscosity. (c) Same as panel B but data for Viscous HR™ dissolved in water.






Viscous HR™ dissolved at the same concentrations in neat glycerol (left cuvette) and in water (right cuvette). The cuvettes are placed on an UV light box and illuminated from below.