Synthesis and aggregation behavior of biohybrid amphiphiles composed of a tripeptidic head group and a polystyrene tail

• DOI: 10.1039/b816615c
• Publication Date: 2009-03-04T14:01:13Z
• Authors: A. (Ton) J. Dirks; Sander S. van Berkel; Helene I. V. Amat...; Floris P. J. T. R...; Jeroen J. L. M. C...; Roeland J. M. Nolte
• Keywords: METIS-263215; Synthetic Organic Chemistry; Bio-Organic Chemistry; 01 natural sciences; Physical Organic Chemistry; 0104 chemical sciences

The modular synthesis and self-assembly behavior of a set of peptide-polymer hybrid amphiphiles is described. Gly-Gly-Arg derivatives were conjugated to one of the ends of hetero-telechelic polystyrene (PS) via either the Cu-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) reaction or conventional peptide coupling chemistry. Both conjugation strategies proved to be efficient and they were also applied sequentially to create a biohybrid ABA-type triblock copolymer, which can be considered as a macromolecular bolaamphiphile. In the synthesis of the regularly-shaped peptide-PS amphiphiles (i.e. AB-type) two polymer lengths (n = 21 and n = 49) were employed having additional variations in their end group composition. As expected, the structural variations were demonstrated not to influence the self-assembly behavior of the biohybrids in water, and comparable vesicles were formed in all cases. At the air/water interface, the structural variations had a greater impact on the self-assembly of the biohybrids, especially for the phase transition from gas to liquid because it is dominated by steric interactions between the polymer chains. In a condensed phase (which closely resembles the situation in a bilayer vesicle), the packing of various biohybrids was found to be comparable. The interfacial self-assembly behavior of the bolaamphiphile (n = 21) was also studied and this compound probably formed multi-layered structures on the water surface. In aqueous solution the bolaamphiphile formed spherical aggregates similar to the regular peptide-PS amphiphiles. Although these assemblies appeared to be vesicular, their exact nature remains unclear.