The Mechanism And Application Of The Co-Assembly Of Hairpin Peptide And Organic Acid

Polypeptide is a compound formed by the dehydration and condensation of two or more amino acid molecules,and it is also an intermediate product of protein hydrolysis.Peptide self-assembly refers to the process of spontaneously forming ordered assemblies under the action of various non-covalent forces.In recent years,researches have been conducted on various types of peptides with molecular structural characteristics,including amphiphilic peptides,ion-complementary peptides,cyclic peptides,hairpin peptides,amyloid and derivatives,and so on.Among them,β-hairpin is a kind of polypeptide molecule containing a turn structure.It first folds intramolecularly due to charge shielding during self-assembly,adoptsβ-sheet conformation,and hydrophilic amino acid residues are distributed on one side to form On the hydrophilic surface,hydrophobic amino acid residues are distributed on the other side to form a hydrophobic surface,which then self-assembles into a one-dimensional nanostructure through hydrophobic interaction.In this paper,hairpin peptides are used as model molecules to study the effects of the addition of different cofactors such as metal ions and dibasic organic acids on the molecular structure and morphology of hairpin peptides.And further explore the potential of cofactors and hairpin peptide assemblies Applications include the construction of hydrogel materials and simulated enzymes,and the performance of hydrogel materials and the catalytic reaction activity of simulated enzymes have been evaluated.The research content includes the following aspects:（1）Takingβ-hairpin peptide CBHH（Ac-VKVKVHVHV^DPPTHVHVKVKV-NH₂）as the research object,the self-assembly behavior of CBHH in aqueous solution under different p H values was first investigated.The CD results showed that with the increase of p H,the structure of CBHH in aqueous solution gradually change from random coil toβ-sheet structure.At the same time,we investigated the regulation of the assembly ofβ-hairpin peptide CBHH by adding three organic acids（succinic acid,malic acid,tartaric acid）with different numbers of hydroxyl groups.Through CD and AFM,we found that the organic acid under p H=4.0,The addition of acid can promote the transformation ofβ-hairpin peptide CBHH from a random coil structure to aβ-sheet structure.The AFM results show that the addition of organic acid can induce the transformation of CBHH from disordered short fibers to ordered fibers,which is expressed in terms of fiber length and increase in width.In addition,we introduced theβ-hairpin peptide HHK（Ac-VKVHVHV^DPPTHVHVKV-NH₂）.Compared with CBHH,HHK lacks a pair of hydrophilic and hydrophobic amino acids,and its folding and assembly require greater driving force,but the addition of organic acids can also regulate the assembly behavior of HHK.The above work provides a new idea for us to explore the regulation of hydroxyl groups on peptide folding and assembly.（2）The nanofiber network is the basis for the formation of hydrogel materials.We used the polypeptide CBHH as a template and added organic acids for co-assembly to prepare a series of hydrogels.The study found that at p H=5.7,the addition of succinic acid and malic acid can induce the CBHH solution to form a hydrogel material,while tartaric acid has no obvious effect.Under the condition of p H=7.0,the addition of organic acid can significantly improve the mechanical strength of CBHH hydrogel,and it has good shear recovery performance and temperature resistance under certain conditions.Cytotoxicity experiments show that,compared with CBHH,the hydrogel material prepared after adding organic acid has good compatibility with NIH-3T3 cells.（3）The introduction of metal ions has studied its effect on the assembly ofβ-hairpin peptide CBHH.It is found that the addition of Zn²⁺and Cu²⁺can form a metal ion coordination effect with CBHH at p H=5.0,thereby promoting the correct folding and assembly of CBHH.Therefore,we used the coordination of metal ions and CBHH to construct an artificial metalloenzyme,and selected the hydrolysis reaction of p-nitrophenyl acetate as the model reaction.The study found that,compared with CBHH,our artificial metalloenzyme co-assembled with Cu²⁺and Zn2⁺andβ-hairpin peptide CBHH has higher catalytic activity.We found that adding a certain concentration of salt ions（Na Cl）,increasing the system temperature and p H can significantly improve the catalytic activity of artificial metalloenzymes.Finally,we investigated the effect of the introduction of hydroxyl groups on the catalytic activity through the co-assembly of CBHH and organic acid.We found that the addition of organic acid did not have a significant effect on the catalytic activity of CBHH,but we successfully prepared a catalytic activity.The hydrogel materials further improve the application of hydrogel materials.