Glutaraldehyde Coupling to Phosphatidylethanolamine Lipid Derivatives

Conjugation via Glutaraldehyde Coupling to Phosphatidylethanolamine Lipid Derivatives 

Glutaraldehyde is among the earliest homobifunctional cross-linkers employed for protein conjugation (Chapter 4, Section 6.2). It reacts with amine groups through several routes, including the formation of Schiff base Unkages, which can be reduced 

Liposomes containing PE residues can be reacted with glutaraldehyde to form an activated surface possessing reactive aldehyde groups. A two-step glutaraldehyde reaction strategy is probably best when working with liposomes, since precipitated protein would be difficult to remove from a vesicle suspension. 

The following protocol describes the two-step method wherein the fiposome is glutaraldehyde-activated, purified away from excess cross-linker, and then coupled to a protein by reductive amination (Fig. 352). 

Prepare a liposome suspension, containing PE, at a total lipid concentration of 5 mg/ml in 0.1 M sodium phosphate, 0.15 M NaCl, pH 6.8, Maintain all lipid-containing solutions under an inert gas atmosphere. Degas all buffers and bubble them with nitrogen or argon prior to use. 

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