DMS Cross-linking to Phosphatidylethanolamine Lipid Derivatives

Conjugation via DMS Cross-linking to Phosphatidylethanolamine Lipid Derivatives 

B/s-imidoesters like DMS may be used to couple proteins to PE-containing liposomes by cross-linking with the amines on both molecules (Fig. 353). However, single-step cross-linking procedures using homobifunctional reagents are particularly subject to uncontrollable polymerization of protein in solution. Polymerization is possible because the procedure is done with the liposomes, protein, and cross-linker all in solution at the same time. 

The reaction is carried out in 0.2 M triethanolamine, pH 8.2. DMS should be the limiting reagent in the reaction to avoid blocking all amines on both molecules with only one end of the cross-linker, thus eliminating any conjugation. The amounts of total lipid and protein in solution may have to be adjusted to optimize each conjugation reaction and avoid precipitation of protein or aggregation of liposomes. 

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