Research And Application Of Self-assembly Behavior Of Short Peptides Induced By Enzyme And Small Molecule In Confined Space

Molecular self-assembly is a common phenomenon in the evolution of nature.The formation of nucleic acids,proteins,cells and even life is achieved by self-assembly,and most self-assembly activities in living organisms take place in a variety of confined environments,such as cells,lipid membranes,enzyme capsules,vesicles,micelle biological organic framework and so on.The short peptide molecule is essentially a low molecular weight bioactive protein,which has become a current research focus due to its inherent biocompatibility,biodegradability and low immunogenicity.As a building block for the "bottom-up" fabrication of supramolecular nanomaterials,the basis of the assembly of short peptide molecules is the synergy of various intermolecular interaction forces,which can be modulated by some commonly used kinetic parameters,including pH,temperature,metal ions,enzymes and small organic molecules.Based on this,from the perspective of bionics,we change the covalent bond,non-covalent bond,and assembly environment,trigger molecular self-assembly activities with mild biological stimulation,and explore the influence of the confined space on the self-assembly of short peptides by simulating the localized environment in organisms.First,a series of Fmoc-modified dipeptides and amino acids were designed to explore the catalytic effect of thermolysin.The results from experiments and computational simulation showed that the hydrophobicity and sequence of amino acids had significant correlation with thermolysin catalytic reactions including binding capacity and catalytic efficiency.Depending on the substrate design,thermolysin could catalyze the reaction towards hydrolysis or condensation.Taking advantage of the bidirectional catalytic actions of thermolysin,a two-step reaction was designed to modify the sequence of Fmoc-dipeptide from Fmoc-YL-COOH to Fmoc-YY-NH2 with gel-sol-gel transition.Second,in order to to mimic the self-assembly of molecules triggered by enzyme in nature,thermolysin-catalyzed short peptide condensation reactions was applied to the confined space of AAO templates.During the whole process,different spatial structure and pore size of AAO templates were chosen to investigate their effects on the self-assembly of short peptides.Meanwhile,short peptides with various sequences were also tested to reveal the influence of molecule-self on the self-assembly in confined environment.In addition,several Fmoc-amino acids with different hydrophobic properties were selected to investigate the effect of L-NH2 on the assembly of Fmoc-amino acid.The study showed that L-NH2 and Fmoc-amino acids formed new hydrogen bonds to change the morphology and secondary structure of the assembly,and transformed from an irregular morphology to crystalline structure with regular morphology accompanying solid-solid phase transformation.At last,the capillaries with different pore diameters were used as confined space to study the self-assembly of Fmoc-amino acids under the control of L-NH2,and the short peptides formed assembly similar to the extracellular matrix through the adsorption of the capillary wall,thus promoting the formation of the cell layer similar to tubular structure.