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JBS Black Light

Fluorescent Crystal Dye

1-Anilinonaphthalene-8-sulfonic acid

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Structural formula of JBS Black Light (Fluorescent Crystal Dye, 1-Anilinonaphthalene-8-sulfonic acid)
Structural formula of JBS Black Light

For in vitro use only!

Shipping: shipped at 4 °C

Storage Conditions: store at 4 °C
store dark

Shelf Life: 12 months

Molecular Formula: C16H13NO3S

Molecular Weight: 299.35 g/mol

CAS#: 82-76-8

Form: supplied as 9 mM solution in water containing 1 % (w/v) Glycerol

Spectroscopic Properties: λabs 375 nm, λem 480 nm (Fluorescence excitation and emission maxima of 1-anilino- naphthalene-8-sulfonic acid bound to bovine serum albumin)

JBS Black Light is a nonspecific fluorescent crystal dye suitable for the detection of protein crystals in crystallization trials [1].

It has been demonstrated that the addition of small amounts of a non-specific fluorescent dye to the protein sample directly before crystallization yields a significantly enhanced fluorescence signal [1].

The signal can be exploited to contrast protein crystals above background artifacts and enables the detection of microcrystals, even if they are located under a protein skin. Further, it can be used to differentiate protein crystals from salt crystals since the latter show no significant fluorescence. Beside the examination of crystallization trials, JBS Black Light can be also used to visualize and identify crystals within a cryo loop.

JBS Black Light is non-fluorescent in water. It only becomes fluorescent when bound to hydrophobic regions of the protein. Thus, it is a sensitive indicator of protein folding, conformational changes and other processes that alter the exposure of the protein sample to the surrounding solvent.

An investigation of 10 proteins has revealed that the addition of low concentrations of fluorescent dye (μM to nM) has no significant effect upon the crystallization behavior of proteins. Only in one case an increased tendency to protein precipitation has been observed at a final dye concentration of 9 mM. This could be omitted by choosing lower dye concentrations [1].

Using a low-power broad bandpass UV-light source, significant fluorescence signals could be observed in the range of 9 mM to 9 μM dye concentration in the protein sample. Applying longer exposure times, this could be decreased to values as low as 0.9 nM [1].


  • You may use the stock solution as is or prepare a favoured dilution of JBS Black Light in water, i.e. 1:10 or 1:100.
  • Add the aliquots of JBS Black Light to your protein sample in a ratio of 1:10 immediately prior to crystallization.
  • Perform your crystallization experiment as usual.
  • Store the crystallization plates in the dark or cover them with aluminium foil since the dye is degradable by visible light.
  • Visualize your crystallization plates under a fluorescence microscope with a low-power broad bandpass UV-light source. (A filter removing emission wavelength below 490 nm should be used to remove signals caused by native protein fluorophores.)

Selected References:
[1] Groves et al. (2007) A method for the general identification of protein crystals in crystallization experiments using a noncovalent fluorescent dye. Acta Cryst. D 63:526.