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A pegylated SPDP crosslinker for reversible disulfide conjugation between amines and sulfhydryls.

Pierce PEG4-SPDP

Thermo Scientific Pierce PEG4-SPDP is a multifunctional crosslinker for protein conjugation via amine-to-amine or amine-to-sulfhydryl crosslinks that contain a 4-unit polyethylene glycol (PEG) group and a reducible (cleavable) disulfide bond.

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.


  • Efficient amine conjugationNHS ester provides effective conjugation to lysines, N-termini of peptides and other primary amines
  • Reversible sulfhydryl conjugationpyridyldithiol 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)

Product Details:

2-Pyridyldithiol-tetraoxatetradecane-N-hydroxysuccinimide; PEG4-SPDP
Chemical structure of PEG4-SPDP crosslinking reagent.

Conjugation of SPDP reagents to primary amines reactions via the NHS ester is most commonly performed at pH 7 to 8 in phosphate, carbonate/bicarbonate or borate buffer. Other buffers that do not contain primary amines (or thiols or disulfide reducing reagents – see the sulfhydryl reactivity discussion) are also effective.

Reaction with the sulfhydryl-reactive pyridyldithio group can be performed with (simultaneously) or following the amine reaction, and it occurs optimally at pH 7 to 8. The reaction results in pyridine-2-thione displacement, the concentration of which can be determined by measuring the absorbance at 343nm. Reaction buffers must be free of thiols and disulfide reducing agents until quenching or reduction of the 2-pyridyldithio is desired.

Properties of PEG4-SPDP.
Chemical name 2-pyridyldithiol-tetraoxatetradecane-N-hydroxysuccinimide (simplified)
Molecular formula C23H33N3O9S2
Molecular weight 559.65
Spacer arm length 25.7 Å
Form straw to amber colored oil
Solubility dissolve 2mg in 179µL DMSO or DMF to make 20mM stock for each use
Reactive groups: NHS ester, reacts with primary amines
  Pyridyl disulfide, reacts with sulfhydryls

Product References:

Crosslinker Application Guide -- search for recent literature references for this product

Related Resources:

Overview of crosslinking
Chemistry of crosslinking
PEGylation technical guide

Related Products:

Crosslinkers at a glance (selection guide)
Other SPDP-type Reagents
PEGylation Reagents

Ordering Information
Product # Description Pkg. Size Instructions MSDS CofA Price
26128 PEG4-SPDP
Formulation: 2-Pyridyldithiol-tetraoxatetradecane-N-hydroxysuccinimide; amber oil liquid
Sufficient For: 179mL of typical 1X (1mM) reaction solution, or approx. 50 uses at 2mg reagent per use
100mg Product Instructions for product #26128 PEG4-SPDP MSDS for product #26128 PEG4-SPDP Certificate of Analysis for product #26128 PEG4-SPDP $267.00

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Instructions | MSDS | CofA
Product Instructions | MSDS | CofA  

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