Dithiobis(succinimidyl Propionate)

Lomant’s Reagent, also known as DSP (Dithiobis(succinimidyl Propionate)), is a membrane-permeable, thiol-cleavable, homobifunctional crosslinking reagent. It contains amine-reactive N-hydroxysuccinimide (NHS) ester groups at both ends of an 8-atom spacer arm. The NHS esters react specifically with primary amines at pH 7–9, forming stable amide bonds that covalently link proteins or other amine-containing molecules. The central disulfide bond within the spacer is cleavable under reducing conditions using agents such as Dithiothreitol (DTT), Tris(2-carboxyethyl)phosphine (TCEP), or 2-Mercaptoethanol, allowing reversible cross-linking for downstream analyses.

Although insoluble in water, DSP can be dissolved in polar aprotic solvents such as N,N-Dimethylformamide (DMF) or Dimethyl Sulfoxide (DMSO). Its membrane permeability enables cross-linking of intracellular proteins, stabilizing weak or transient protein–protein interactions for study. It can also be used to fix protein complexes in tissues for immunostaining, immobilize proteins on amine-coated surfaces, or generate bioconjugates for biochemical assays.

A related crosslinker, 3,3’-Dithiobis(sulfosuccinimidylpropionate) (DTSSP, or Sulfo-DSP), shares a similar 8-atom spacer and homobifunctional NHS ester chemistry. The primary distinction is that DTSSP is water-soluble and membrane-impermeable due to the sulfonate groups, making it selective for labeling extracellular or cell surface proteins without penetrating membranes.

This combination of structural features—spacer length, cleavable disulfide bond, and membrane permeability—makes Lomant’s Reagent versatile for studying both intra- and extracellular protein interactions, mapping protein complexes, and creating reversible bioconjugates.

References:

1. Lomant, A.J. and Fairbanks, G. (1976) J. Mol. Biol. 104, 243-261.
2. Tavers, R.C., et al. (1982) J. Biol. Chem. 257, 10708-10714.
3. Park, L.S., et al. (1986) J. Biol Chem. 261, 205-210.