Merck, 803499-100MG, PEG4-SPDP (PEGylated, long-chain SPDP crosslinker)

General description
SPDP-type reagents have an amine-reactive N-hydroxysuccinimide (NHS) ester at one end and a suflhydryl-reactive 2-pyridyldithiol group at the opposite end. PEG4-SPDP has a 4-unit polyethylene glycol spacer arm, which confers greater solubility to the crosslinker and linked proteins compared to crosslinkers having only hydrocarbon spacers. Pyridyldithiol reagents produce disulfide-containing linkages that can be cleaved with reducing agents such as dithiothreitol (DTT). Crosslinking experiments with SPDP reagents are not limited to those involving proteins. Any of a variety of molecules with primary amines and sulfhydryl groups can be modified or crosslinked using an SPDP reagent.
Features and Benefits

• Reactive groups: NHS ester and pyrirdyldithiol
• Efficient amine conjugation—NHS ester provides effective conjugation to lysines, N-termini of peptides and other primary amines
• Reversible sulfhydryl conjugation—pyridyldithiol group enables disulfide linkage with reduced cysteines and other sulfhydryl groups, providing a stable but cleavable bond
• Polyethylene glycol—PEG groups are flexible, non-immunogenic, hydrophilic, and often enhance the solubility of attached molecules
• Spacer arm—connects primary amines and sulfhydryl targets at distances up to 25.7 angstroms; compare to PEG12-SPDP (54.1 angstroms)

Disclaimer
This product is sensitive to moisture. The vial is packaged in a resealable bag with a desiccant to reduce exposure to moisture. After cold storage, equilibrate the vial to room temperature before opening to reduce condensation inside the vial. Make fresh solutions. Storage of stock solutions is not recommended. After use, return the vial to the resealable bag. Close the bag and store the product at the recommended temperature.