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 (ELPs) 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 thermoresponsive materials. Further fundamental studies evaluating coacervative properties of novel nonlinear ELPs could present design concepts for new thermoresponsive materials. In this study, we prepared novel ELPs, cyclic (FPGVG) n (cyclo[FPGVG] n, n = 1-5), and analyzed their 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.