Controllable Self-Assembly And Catalytic Conversion Of Small Biomolecules

To functionalize and high-efficiently utilize the small biomolecules, aromatic peptide and monosaccharide were chose as model molecules in this thesis. Since it is difficult to use these molecules directly, we employed two pathways to transform them to functional nanomaterials and high-value chemicals. The first one is "self-assembly" way for peptide-based biomolecules by regulating the assembly process. The other one is "catalytic conversion" way for sugars through enzymatic and chemical catalysis process.(1) Interface controlled self-assembly of diphenylalanine (FF):Different surfaces were used to regulate the FF self-assembly. We found that FF could self-assemble into a core-branched nanostructure in H2O. The resulting pre-assemblies further assembled into nanofibers and microvesicles on the glass surface and microporous membrane, respectively. Our results reveal a hierarchical and interface-induced assembly behavior of FF, meanwhile, a new structure of FF assemblies was obtained.(2) Solvent and surface controlled self-assembly of diphenylalanine:Our results show that the structural transition of microtubes assembled in H2O into nanofibers can be easily achieved by introducing CH3CN as co-solvent. Furthermore, the synergism of solvent and surface make it more facile and efficient to obtain the high-uniform assemblies. We proposed that hydrogen-bond donor/acceptor ability may be the major determinants for the supramolecular arrangement of FF, while surface tension may play an important role in the structural transition.(3) Synthetic reaction driven self-assembly:Amino acids was chose as building units, a new pathway, named reaction-assembly, for preparing peptide-based hydrogels was designed. In the reaction-assembly process, the Fmoc-peptides were synthesized by chemical reaction, meanwhile, the resulting Fmoc-peptides was assembled into hydrogels via non-covalent interactions. The structure of hydrogels is similar with that obtained from traditional assembly pathway using pure Fmoc-peptides as starting materials.(4) Polysaccharide controlled self-assembly of Fmoc-diphenylalanine (Fmoc-FF): Here konjac glucomannan (KGM) is proposed as a stabilizer for preparing Fmoc-FF/KGM hybrid hydrogel. Results show that the hybrid hydrogel has much higher stability compared to Fmoc-FF hydrogel alone, which may be attributed to the branched chains, a high water-absorption capacity, and the abundant -OH groups of the KGM. Moreover, docetaxel was chosen to study the release behavior. The sustained and controlled drug release from this hybrid hydrogel was achieved by varying the concentrations of KGM and beta-mannanase.(5) Enzymatic hydrolysis of lignocellulose into sugars:A process was designed to pretreat lignocellulose by using formic acid and aqueous ammonia based on corn cobs. The pretreated corn cobs were then hydrolyzed into sugars by cellulases. This process was demonstrated to fractionate lignocellulose to cellulose, hemicellulose and lignin. It also provides a high cellulose digestibility, thus resulting in a high yield of sugars.(6) Understanding the key factors that limit cellulose hydrolysis:After different pretreatments, cellulose hydrolysis and measurements of physicochemical characteristics were performed in this work. Partial least squares was then applied to seek the key factors limiting the cellulose digestion. Results show that the most important factor for cellulose digestion was accessible interior surface area, followed by delignification and the destruction of the hydrogen bonds.(7) Catalytic conversion of glucose into 5-hydroxymethylfurfural (5-HMF):Here a new catalytic system featuring the integration of enzymatic and acid catalysis has been developed for the conversion of glucose into 5-HMF. In this process, borate-assisted isomerase was used to convert glucose into fructose, leading to high fructose yield. The resulting sugar mixtures were dehydrated in water-butanol media to produce 5-HMF.