Design And Synthesis Of Potassium-Selective Helical Structures

Molecular recognition is the basis of the living system activities.They are mainly achieved through intermolecular or intramolecular interactions.Non-covalent interactions not only control the three-dimensional structure of biomacromolecules?such as proteins and DNA?,but also play a key role in biological functions.Biomacromolecules can perform their complex biological duties effectively by adopting a special compact conformation of thermodynamics and kinetically.The function of these advanced structures has become an important goal for chemists.The chemical bionic methods to simulate the high-order structure and function of the life system,and thus further understand the relationships between structure and function in the life system,which has become a hot topic in recent years.Helix is a typical model of bionic structure.In recent years,great progress has been made in the biomimetic study of helical structures.The diversity of chemical structures has been brought into full play in the design and preparation of helical structures.These abundant helical structures show important applications in molecular recognition,transmembrane transport,chiral separation,sensing,and catalysis.Based on the development of helical structure,this dissertation will focus on the helix structure with potassium selectivity:?1?design and synthesis of helical molecule with internal cavity to achieve selective recognition and regulation of potassium ion;?2?helical polymer channel is designed to achieve selective recognition and transmembrane transport of potassium ion.Specifically,we use pyridine derivatives,quinoline derivatives,and oxadiazoles as monomers to design and synthesize aromatic helical structures,develop helical molecular capsule with potassium ion binding and release capabilities,and prepare potassium-selective transmembrane-transport abilities of helical polymer channel.1.A Switchable Helical Capsule for Encapsulation and Release of Potassium IonHelical receptors have received widespread attention.We can design a helix with potassium binding ability.Utilizing the dynamic regulation of the helical structure,the encapsulation and release of potassium ions can be realized through controlling the folding and unfolding of the helical structure.The control of potassium ion encapsulation and release enables us to develop intelligent bionic transmembrane helical channels.In view of these assumptions,we designed a helical moleculear capsule with quinoline,1,3,4-oxadiazole,and a pyridine derivative as monomers.The quinoline groups at both ends act as capping groups,and the central pyridine and oxadiazole form distinctly cavity structure,while the introduction of the pyridine group can be protonated and deprotonated to regulate the entire helical structure through pH.The crystal structure shows that the cavity diameter of the helical molecular capsule is about 0.6 nm,and the UV-vis and NMR titration deduced that the binding constant of the helical capsule to K⁺is about 3000 M^-1,and various characterization techniques such as CD,UV-vis and NMR indicate that pH can effectively regulate the unfolding and refolding process of the helical molecular capsule,accompanied by the binding and release of potassium ion.2.Potassium Ion Channel Constructed from Helical PolymerThe crystal structure shows that there is a fixed angle between the pyridine group and the two adjacent oxadiazoles and it is folded helically along a single direction.Therefore,we can design and synthesize helical polymer with potassium ion recognition ability based on this structural feature.Our research group recently discovered that the relevant oligomers can achieve selective transport of potassium ion.The synthesis of helical polymer through the selection of structural sequences and the construction of helical polymer channel with potassium-selective transmembrane transport have become important work in this area.We have prepared rigid helical polymer channel by optimizing the conditions for the synthesis of helical polymer.By means of bionic transmembrane studies,we have found that the new type of helical polymer have significant potassium ion recognition and selective transport capabilities.This is an important step in the field of helical polymer biomimetic channels.