Dansyl chloride
Encyclopedia
Dansyl chloride or 5-naphthalene-1-sulfonyl chloride is a reagent that reacts with primary amino group
s in both aliphatic and aromatic amines to produce stable blue- or blue-green–fluorescent
sulfonamide adducts. Dansyl chloride is widely used to modify amino acids; specifically, protein sequencing
and amino acid
analysis. It can also be used to label hydroxyl and carboxylic acid functional groups.
Dansyl chloride may also be denoted DNSC. Likewise, a similar derivative, dansyl amide
is known as DNSA.
In addition, these protein-DNSC conjugates are sensitive to their immediate environment. This, in combination with their ability to accept energy (as in fluorescence resonance energy transfer
) from the amino acid tryptophan
, allows this labeling technique to be used in investigating protein folding and dynamics.
The fluorescence of these sulfonamide
adducts can be enhanced by adding cycloheptaamylose. Dansyl chloride is unstable in dimethyl sulfoxide
, which should never be used to prepare solutions of the reagent.
The extinction coefficient of dansyl derivatives are important for measuring their concentration in solution. Dansyl chloride is one of the simplest sulfonamide derivatives, so it commonly serves as a starting reagent for the production of other derivatives. Exotic derivatives may have very different extinction coefficients, but others, such as dansyl amide
, are similar to dansyl chloride in absorption and fluorescence characteristics. But even for dansyl chloride, there are a variety of extinction coefficient values that have been reported. Some of the values are used to estimate the extent of success in attempts to conjugate the dye to a protein. Other values may be used to determine a precise concentration of a stock solution. See the table below for specific values and their uses.
For all of the studies below, the absorption value is always taken at the maximum that appears between 310 nm and 350 nm. The peak is broad, so the measurement is not very sensitive. However, trivial errors due to wavelength calibration of the spectrophotometer can be avoided by taking the value at the maximum instead of strictly using 330 nm.
Amine
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...
s in both aliphatic and aromatic amines to produce stable blue- or blue-green–fluorescent
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
sulfonamide adducts. Dansyl chloride is widely used to modify amino acids; specifically, protein sequencing
Protein sequencing
Protein sequencing is a technique to determine the amino acid sequence of a protein, as well as which conformation the protein adopts and the extent to which it is complexed with any non-peptide molecules...
and amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
analysis. It can also be used to label hydroxyl and carboxylic acid functional groups.
Dansyl chloride may also be denoted DNSC. Likewise, a similar derivative, dansyl amide
Dansyl amide
Dansyl amide is a reactive fluorescent dye that is used in biochemistry and chemistry to label substances with the fluorescent dansyl group. It is also produced as a side-product in the labelling of amino acids with dansyl chloride....
is known as DNSA.
In addition, these protein-DNSC conjugates are sensitive to their immediate environment. This, in combination with their ability to accept energy (as in fluorescence resonance energy transfer
Fluorescence resonance energy transfer
Förster resonance energy transfer , also known as fluorescence resonance energy transfer, resonance energy transfer or electronic energy transfer , is a mechanism describing energy transfer between two chromophores.A donor chromophore, initially in its electronic excited state, may transfer energy...
) from the amino acid tryptophan
Tryptophan
Tryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG...
, allows this labeling technique to be used in investigating protein folding and dynamics.
The fluorescence of these sulfonamide
Sulfonamide
Sulfonamide or sulphonamide may refer to:*Sulfonamide – the sulfonamide functional group. *Sulfonamide – the group of sulfonamide antibacterial drugs....
adducts can be enhanced by adding cycloheptaamylose. Dansyl chloride is unstable in dimethyl sulfoxide
Dimethyl sulfoxide
Dimethyl sulfoxide is an organosulfur compound with the formula 2SO. This colorless liquid is an important polar aprotic solvent that dissolves both polar and nonpolar compounds and is miscible in a wide range of organic solvents as well as water...
, which should never be used to prepare solutions of the reagent.
The extinction coefficient of dansyl derivatives are important for measuring their concentration in solution. Dansyl chloride is one of the simplest sulfonamide derivatives, so it commonly serves as a starting reagent for the production of other derivatives. Exotic derivatives may have very different extinction coefficients, but others, such as dansyl amide
Dansyl amide
Dansyl amide is a reactive fluorescent dye that is used in biochemistry and chemistry to label substances with the fluorescent dansyl group. It is also produced as a side-product in the labelling of amino acids with dansyl chloride....
, are similar to dansyl chloride in absorption and fluorescence characteristics. But even for dansyl chloride, there are a variety of extinction coefficient values that have been reported. Some of the values are used to estimate the extent of success in attempts to conjugate the dye to a protein. Other values may be used to determine a precise concentration of a stock solution. See the table below for specific values and their uses.
For all of the studies below, the absorption value is always taken at the maximum that appears between 310 nm and 350 nm. The peak is broad, so the measurement is not very sensitive. However, trivial errors due to wavelength calibration of the spectrophotometer can be avoided by taking the value at the maximum instead of strictly using 330 nm.
| Species | Extinction Coefficient [M−1·cm−1] | Notes |
|---|---|---|
| DNSC-protein | 3300 | Use for DNSC-protein conjugates; Used to determine degree of labeling in chymotrypsin and ovalbumin |
| DNSC | 4350 | In bicarbonate buffer; maximum is shifted to ~315 nm |
| DNSC | 4550 | In water; peak shifted to 312 nm |
| DNSA | 4050 | In 60% ethanol; Measured at 329 nm |
| DNSC | 4000 | Conditions are not given; no reference to the source of this value |