Dansyl chloride

Dansyl chloride, also known as 5-(dimethylamino)naphthalene-1-sulfonyl chloride, is a fluorescent probe used extensively in biochemistry and chemistry for labeling amino acids, amines, and other compounds containing primary or secondary amine groups. Its popularity stems from its high fluorescence quantum yield and the fact that the fluorescence is sensitive to the environment, making it a versatile tool for studying biomolecular interactions.

Properties

Dansyl chloride is characterized by its bright yellow color and is soluble in organic solvents such as acetone, ethanol, and dimethyl sulfoxide (DMSO). Upon reaction with amine groups, it forms stable dansyl derivatives that can be excited at wavelengths around 340 nm, emitting fluorescence at approximately 500-548 nm. This property allows for the detection and quantification of dansyl-labeled molecules using fluorescence spectroscopy.

Applications

Dansyl chloride is widely used in peptide and protein research to analyze the amino acid composition of peptides and proteins. It is also employed in the study of protein folding and protein-protein interactions through fluorescence resonance energy transfer (FRET) techniques. Additionally, dansyl chloride has applications in pharmacology for drug discovery and in environmental science for tracing organic pollutants.

Synthesis and Reactivity

The synthesis of dansyl chloride involves the sulfonation of 1-amino-5-naphthol with chlorosulfonic acid, followed by treatment with dimethylamine. Dansyl chloride reacts with primary and secondary amines to form sulfonamide bonds, releasing hydrochloric acid (HCl) as a byproduct. This reaction is typically carried out in an organic solvent under basic conditions to neutralize the HCl formed.

Safety

Handling of dansyl chloride requires caution as it is a corrosive substance and can cause burns upon contact with skin or eyes. It is also a potential respiratory irritant and should be used in a well-ventilated area or under a fume hood. Appropriate personal protective equipment (PPE) such as gloves and safety glasses should be worn when handling this chemical.

See Also

• Fluorescence spectroscopy
• Amino acid analysis
• Protein-protein interactions
• Fluorescent probe