Synthesis and application of peptide dendrimers as protein mimetics

The multiple antigenic peptide (MAP) is a novel approach to preparing peptide immunogens. The MAP consists of an inner core matrix built up of a large layer of Lys residues and a surface of peptide chains attached to the core matrix. Because of its dendrimeric structure, MAP can be very useful as a template for assembling potential peptide surfaces. Two methods for preparing MAP systems are described in this unit. The direct approach for preparing MAP systems is presented in the first two protocols, including the procedure for b-butyloxycarbonyl (Boc) chemistry and the procedure for 9 -fluorenylmethyloxycarbonyl (Fmoc) chemistry. An indirect approach for preparing MAP systems, in which peptide and core matrix are synthesized separately and conjugated by several ligation methods, is then described. The cMAP approach is also executed using either the direct or indirect approach, but requires an additional cyclization step to constrain the peptides after synthesis. The synthesis of cMAP is described, and the preparation of cyclic peptides is illustrated. A support protocol describes the ninhydrin assay to assess the completeness of the coupling reaction. In most cases, MAP systems can be used directly after simple dialysis or desalting. Some immunological studies, however, require purified MAPs. Additional support protocols describe MAP system purification by dialysis and high-performance gel-filtration chromatography.