Enhancement of self-aggregation properties of linear elastin-derived short peptides by simple cyclization: strong self-aggregation properties of cyclo[FPGVG]_n, consisting only of natural amino acids

Elastin-like peptides (ELP) consist of distinctive repetitive sequences, such as (VPGVG)_n, exhibit temperature-dependent reversible self-assembly (coacervation), and have been considered to be useful for the development of thermo-responsive materials. Further fundamental studies evaluating coacervative properties of novel nonlinear ELPs could present design concepts for new thermo-responsive materials. In this study, we prepared novel ELPs, cyclic (FPGVG)_n (cyclo[FPGVG]_n, n = 1-5), and analyzed its self-assembly properties and structural characteristics. Cyclo[FPGVG]_n (n = 3-5) demonstrated stronger coacervation capacity than the corresponding linear peptides. The coacervate of cyclo[FPGVG]₅ was able to retain water-soluble dye molecules at 40°C, which implied that cyclo[FPGVG]₅ could be employed as a base material of DDS (Drug Delivery System) matrices and other biomaterials. The results of molecular dynamics simulations and circular dichroism measurements suggested that a certain chain length was required for cyclo[FPGVG]_n to demonstrate alterations in molecular structure that were critical to the exhibition of coacervation.