What is SPDP Crosslinker?

SPDP (SPDP Crosslinker) is a short-chain crosslinker for amine-to-sulfhydryl conjugation via NHS-ester and pyridyldithiol reactive groups that form cleavable (reducible) disulfide bonds with cysteine sulfhydryls. It is a glutathione cleavable ADC linker used for the antibody-drug conjugates (ADCs)

SPDP reagents are a unique group of amine and sulfhydryl reactive heterobifunctional crosslinkers. Whether it is intermolecular amine-amine or amine-sulfhydryl crosslinking, SPDP reagents generate disulfide bonds, which can be cleaved later with reducing agents such as dithiothreitol (DTT).

The amine-reactive moiety of the SPDP reagent is an N-hydroxysuccinimide (NHS) ester. The reaction is most often carried out in phosphate, carbonate/bicarbonate or borate buffers at pH 7-8. The reaction rate of hydrolytic degradation increases with pH, ​​for example, the half-life of NHS esters is several hours at pH 7 and less than 10 minutes at pH 9. As the NHS-ester reagents of SPDP have limited water solubility, they must first be dissolved in an organic solvent and then diluted into the reaction mixture.

The sulfhydryl-reactive moiety of the SPDP reagent is 2-pyridyl disulfide, which reacts optimally with sulfhydryl between pH 7 and 8.1. The reaction displaces the pyridine-2-thione group, the concentration of which can be determined by measuring the absorbance at 343 nm (see Additional Information section). The reaction buffer cannot contain thiols and disulfide reducing agents until the reaction requires quenching or reduction of the 2-pyridyl disulfide.

Two basic methods can be used to form cleavable crosslinks between proteins and SPDP reagents, depending on one or both proteins already possessing sulfhydryl groups (-SH) in addition to primary amines. Both coupling methods generate disulfide bonds in the spacer arms, which can be cleaved by reduction with dithiothreitol (DTT) or other reducing agents. In most cases, the crosslinks produced using SPDP reagents can be cleaved with 25 mM DTT at pH 4.5 without reducing the native protein disulfide bonds but if protection of the native disulfide bonds of the protein is not desired, it can be optimized at pH 7-9 The cleavage of DTT is performed efficiently.

SPDP PEG linker is a PEG reagent(crosslinker) , which have a reducible (cleavable) disulfide bond. Pyridyldithiol group enables disulfide linkage with reduced cysteines and other sulfhydryl groups, providing a stable but cleavable bond.

The containing polyethylene glycol (PEG) spacer arms offer greater solubility to the crosslinker and the linked proteins compared to crosslinkers having only hydrocarbon spacers. SPDP reagents produce disulfide-containing linkages that can be cleaved with reducing agents such as dithiothreitol (DTT).

AxisPharm offers a range of high purity SPDP PEG reagents with different linker lengths.Different kinds of PEG Reagents may be available by custom synthesis. Fast delivery – Overnight shipping.