Organic Solvent‐Free Enzymatic Transformation of Poly(ϵ‐caprolactone) into Repolymerizable Oligomers in Supercritical Carbon Dioxide

The enzymatic transformation of poly(ϵ‐caprolactone) (PCL) into repolymerizable oligomers in supercritical carbon dioxide (scCO₂) using an enzyme was carried out in order to establish a sustainable chemical recycling system for PCL, which is a typical biodegradable synthetic plastic. The enzymatic conversion of PCL beads having an M̄_n of 110 000 using Candida antarctica lipase (lipase CA) in scCO₂ containing small amounts of water quantitatively afforded CL oligomers at 40°C. The CL oligomers were readily repolymerized using the same enzyme to produce high‐molecular weight PCL.     

Efficient Multiple Domain Ligation for Proteins Using Asparaginyl Endopeptidase by Selection of Appropriate Ligation Sites Based on Steric Hindrance

Three domain fragments of a multi-domain protein, ER-60, were ligated in two short linker regions using asparaginyl endopeptidase not involving denaturation. To identify appropriate ligation sites, by selecting several potential ligation sites with fewer mutations around two short linker regions, their ligation efficiencies and the functions of the ligated ER-60s were examined experimentally. To evaluate the dependence of ligation efficiencies on the ligation sites computationally, steric hinderances around the sites for the ligation were calculated through molecular dynamics simulations. Utilizing the steric hindrance, a site-dependent ligation potential index was introduced as reproducing the experimental ligation efficiency. Referring to this index, the reconstruction of ER-60 was succeeded by the ligation of the three domains for the first time. In addition, the new ligation potential index well-worked for application to other domain ligations. Therefore, the index may serve as a more time-effective tool for multi-site ligations.