Numerous techniques have been developed to prepare immunoliposomes based on the nucleophilic reactivity of free amine groups of proteins or peptides. However, the most common, versatile and straightforward activation chemistry for creating reactive acylating reagents and labeling peptides/proteins is to form NHS ester with primary amines. A single step nucleophilic substitution reaction between NHS ester derivative and alpha amines at the N terminal or the beta amines of lysine side chains leads to the formation of a stable amide bond. N-Hydroxysuccinimide (NHS) esters of DSPE-PEG-NHS liposomes react with the primary amine groups on the peptides, proteins, antibodies or other functional ligands for targeted drug delivery applications. The nucleophilic attack of the amine groups on the NHS-activated carbonyl group of the DSPE-PEG-NHS results in the elimination of the NHS group and formation of amide linkage. Immunodox-NHS is a PEGylated product. For other amine reactive (PEGylated and non-PEGyalated products) and also Immunodox products suitable for other types conjugation methods see here.