Abstract: Elastin-like polypeptides (ELPs) as novel thermal-sensitive biomaterials have a broad application prospect in drug delivery, tissue engineering and protein isolation and purification. It is essential for precise control and rapid biosynthesis of ELPs with specific phase transition characteristics. Technology of recursive directional ligation by plasmid reconstruction was used to successfully construct recombinant plasmids pET28-ELP25, pET28-ELP50 and pET28-ELP100 as valine as guest amino acid of ELPs. Then, the recombinant plasmids were transformed into Escherichia coli BL21(DE3), respectively. After cultures of recombinant strains under self-induced medium, SDS-PAGE results showed that ELPs were successfully soluble over-expressed in E. coli system, and the expression level was over 30% of total cell proteins. ELP25, ELP50 and ELP100 were separated and purified by three rounds of inverse transition cycling (ITC). Thermal turbidimetry was used for measurement of phase transition temperature (Tt) of ELPs. Analysis of phase transition characteristics revealed that the Ttof ELPs was negatively correlated with polypeptide concentration, ionic strength and molecular weight of ELPs. The results provide a theoretical basis for further recombinant expression of thermal-sensitive polypeptide biomaterials with required phase transition characteristic.

Key words: elastin-like polypeptides, recursive directional ligation by plasmid reconstruction; inverse transition cycling, phase transition temperature