Title
Solvent-Free Lipase-Catalyzed Synthesis: Unique Properties of Enantiopure D- and L- Polyaspartates and Their Complexation
Author
Yu Zhang, Bo Xia, Yanyan Li, Yuanyuan Wang, Xianfu Lin, Qi Wu
Year
2016
Journal
Biomacromolecules
Abstract
Amino acids are attractive monomers for the large-scale preparation of chiral polyamides. For enzymatic polymerization of amino acids using protease in aqueous environment as the catalysis system, one main restriction is oligomer formation, usually along with other displayed advantages. Herein we developed an efficient solvent-free lipase-catalyzed polymerization of diethyl d- or l-aspartate, providing chiral d- and l-polyaspartates with an average degree of polymerization (DPavg) up to 60 and having about 96% β-linkages. Additionally, their distinct chemical and physical properties were characterized by circular dichroism (CD) spectra, X-ray powder diffraction (XRD), microscopic observation, and thermal analysis. Poly(β-d-AspEt) and Poly(β-l-AspEt) showed vertically mirrored negative and positive CD signals, high crystallinity, and entirely different microscopic morphology. They are thermal stable while having different decomposition (Td), melting (Tm), and cold crystallization temperatures (Tcc), respectively. Our results also showed that the complexation of enantiopure d- and l-polyaspartates was not stereocomplex but homocomplex.
Instrument
J-815
Keywords
Circular dichroism, Thermodynamics, Stereochemistry, Biochemistry