SPDP-Modified Phosphatidylethanolamine Lipid Derivatives

Coupling via SPDP-Modified Phosphatidylethanolamine Lipid Derivatives 

2V-Succinimidyl 3-(2-pyridyldithio)propionate (SPDP) may be the most popular heterobifunctional cross-linking agent available, especially for protein conjugation (Chapter 5, Section 1.1). The activated NHS ester end of SPDP reacts with amine groups in proteins and other molecules to form an amide linkage (Fig. 355). The 

2-pyridyldithiol group at the other end reacts with sulfhydryl residues to form a disulfide linkage with sulfhydryl-containing molecules (Carlsson et al., 1978). 

The following protocol is a suggested method for coupling sulfhydryl-containing proteins to SPDP-activated vesicles. 

Prepare a 5 mg/ml liposome suspension containing a mixture of PCicholes-terol PG PDP-PE in molar ratios of 8 10 1 1. The emulsification may be done by any established method (Section 1). Suspend the vesicles in 50 mM sodium phosphate, 0.15 M NaCl, 10 mM EDTA, pH 7.2. 

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