Thermo Scientific Pierce PEG4-SPDP is a multifunctional protein conjugate for protein conjugation via amine-amine or amine-thiol cross-linking. Cross-linking agent (containing 4-unit polyethylene glycol (PEG) groups and a reducible (cleavable) disulfide bond).

Features of PEG4-SPDP:

•Efficient amine coupling—NHS Ester Yes Efficient coupling of lysine, the N terminus of peptides and other primary amines
• Reversible sulfhydryl coupling—pyridyl disulfideThe group is able to form disulfide bonds with reduced cysteine and other sulfhydryl groups, providing stable but cleavable bonds
• Polyethylene glycol—PEG groups are flexible , non-immunogenic, hydrophilic, often enhances the solubility of the linked molecule
• Spacer—can ligate primary amine and sulfhydryl targets up to 25.7 Angstroms; with PEG12-SPDP (54.1 angstrom),

SPDP-based reagents contain amine-reactive N- Hydroxysuccinimide (NHS) ester containing a thiol-reactive 2-pyridyldisulfide group at the other end. PEG4-SPDP has a 4-unit polyethylene glycol spacer arm, which allows greater solubility of the cross-linker and connexin than cross-linkers with only hydrocarbon spacers. Pyridyldisulfide reagents produce disulfide-containing bonds that can be cleaved using reducing agents such as dithiothreitol (DTT). Cross-linking experiments with SPDP reagents are not limited to those involving proteins. Any molecule with primary amine and sulfhydryl groups can be modified or cross-linked using SPDP reagents.

Coupling of SPDP reagents by reaction of NHS esters with primary amines is typically performed in phosphate, carbonate/bicarbonate or borate buffers at pH 7 to 8. Other buffers that do not contain primary amines (or thiol or disulfide reducing reagents—see discussion of thiol reactivity) are also effective.

Reaction with thiol-reactive pyridyldisulfide groups is carried out simultaneously with or after the amine reaction, preferably at a pH of 7 to 8. The reaction produces pyridine-2-thione substitution, the concentration of which can be determined by measuring the absorbance at 343 nm. Reaction buffers must be free of thiol and disulfide reducing agents until quenching or reduction of 2-pyridyldisulfide is required.

Product References:
Crosslinking Agent Application Guide -- Search the latest references for this product

Related Products< br>PEG12-SPDP (PEGylated, long-chain SPDP cross-linker)
< a href="https://www.thermofisher.cn/order/catalog/product/21857">SPDP (succinimide 3-(2-pyridyldithio)propionate)