sulfoNHS

SulfoNHS, short for N-hydroxysulfosuccinimide, is a water-soluble sulfonated derivative of N-hydroxysuccinimide used to activate carboxyl groups for amide bond formation with primary amines. It is commonly employed in carbodiimide coupling strategies, most often in combination with EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide).

In aqueous media, a carboxyl group is first activated by EDC to form an O-acylisourea intermediate. This intermediate reacts with Sulfo-NHS to generate a sulfo-NHS ester, an amine-reactive intermediate. The sulfo-NHS ester then undergoes nucleophilic attack by a proximal or added amine to form a stable amide bond, releasing the Sulfo-NHS byproduct. The sulfonate group in Sulfo-NHS confers high water solubility, enabling conjugation reactions in aqueous buffers and reducing the need for organic solvents.

Applications of Sulfo-NHS esters include labeling proteins and peptides, attaching dyes or probes, immobilizing biomolecules on surfaces, and creating bioconjugates for research and diagnostic purposes. Reactions are typically performed under mild, near-physiological conditions and can be compatible with a range of buffers and pH values (often around pH 4.5–7.5).

Storage and handling: SulfoNHS is usually supplied as a dry powder and should be stored at low temperature, commonly -20°C or colder, in a dry environment to maintain activity. When dissolved for use, solutions should be prepared freshly and used promptly to minimize hydrolysis and loss of reactivity. As with other reactive NHS esters, appropriate safety precautions should be observed.