Reactive and Photoreactive Cross-linkers

The cross-bridge of ABH consists of a benzoic acid derivative and thus provides a short spacer between conjugated molecules. After ABH modification of a glycoprotein and incubation with a potential target molecule, the solution may be photolyzed with 

Sulfosuccinimidyl-2-(w-azido-o-nitrobenzamido)-ethyl-l,3 -dithiopropionate (SAND) is a heterobifunctional reagent containing an amine-reactive sulfo-NHS ester at one end and a photoreactive phenylazide group on the other (Pierce). The presence of the sulfonate group on the NHS ring lends water solubility to the reagent due to its 

Sulfosuccinimidyl-2-(m-azido-o-nitro-ben2amido)-ethyl-1,3 -ditliiopropionate MW 570.52 18.5 A 

N-Succinimidyl-4(4-azidophenyl)l,3 -dithiopropionate (SADP) is a photoreactive heterobifunctional cross-linker that is cleavable by treatment with a disulfide reducing agent (Pierce). The cross-linker contains an amine-reactive NHS ester and a photoac-tivatable phenylazide group, providing specific, directed coupling at one end and nonselective insertion at the other end. 

SADP is hydrophobic and should be dissolved in organic solvent prior to addition of a small aliquot to an aqueous reaction. Concentrated stock solutions can be prepared in DMSO or DMF. Final concentration of the organic solvent in a cross-linking reaction should not exceed about 10% to prevent protein precipitation or denatura-tion. 

Sulfosuccinimidyl 4-(p-azidophenyl)butyrate (sulfo-SAPB) is a photoreactive heterobifunctional reagent containing an amine-reactive sulfo-NHS ester at one end (Pierce). 

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Of the following amine-reactive and photoreactive cross-linkers, the overwhelming majority use an aryl azide group as the photosensitive function. Only a few use alternative photoreactive chemical reactions, particularly perfluorinated aryl azide, benzophenone, or diazo compounds. For general background information on photoreactive cross-linkers see Das and Fox (1979), Kiehm and Ji (1977), Vanin and Ji (1981), Meijer et al., 1988), and Brunner (1993). 

Finally, the small amine-reactive and photoreactive cross-linker NHS-ASA (Chapter 5, Section 3.1) can be iodinated to provide a nondeavable radioactive conjugate. 

CONTENTS P. 5 =-4. Sulftiydryl-Reactive and Photoreactive Cross-linkers... 

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