| Porphyrins have been developed as powerful tools for applications in various fields owing to their advantageous properties of strong light absorption,high emission,and rich coordination chemistry.The interactions of tetrapyrrolic systems with metal ions are a subject of intensive studies,detailed mechanisms for both metal insertion and metal exchange in the tetrapyrrolic systems are still not well established.Therefore,it is necessary to study the formation and dissociation process of metalloporphyrin complex at the single-molecular level.Nanopore detection technology can observe the process of dissociation,binding and other intermediate processes during the analyte pass through the nanopore.Which have received extensive attention by studying the interaction between molecules and chemical reaction processes to obtain information on the dynamic behavior and internal structure of single molecules.Due to its advantages of simplicity,selectivity,and rapid response,it is widely used in DNA sequencing,DNA damage,metal ions,nucleic acid detection,protein secondary structure,reaction kinetic process monitoring,and other fields.In this work,The mechanism of protonation and metallation of meso-substituted5,10,15,20-tetrakis(4-sulfonatophenyl)-porphyrin(TPPS)was studied at the single molecule level by using α-HL nanopore,and the high sensitivity and selectivity of copper ions were achieved.The main research content are as follows:1.Study on the mechanism of the protonation of TPPS based on α-HL nanoporePorphyrins,is known,to be the amphoteric compounds,i.e.having both basic(N-bases)and acidic(weak NH-acids)properties.At p H < p Ka protons are prone to form protonated porphyrins,resulting in changes in the structure of porphyrins.α-HL protein nanopore was used as the adapter,analyzing the specific current blocking response signal,we can clearly distinguish between free-base(H2P),mono-cation(H3P+),and dication(H4P2+).The whole protonation mechanism was studied on the single-molecule level by using α-HL.Compared with the traditional methods,this method can overcome the shortcomings the overlap of spectroscopy due to different degrees of protonation,providing a new platform for the study of the protonation of porphyrins and their derivatives.2.Study on the mechanism of the metallization of TPPS based on α-HL nanoporeIn this experiment,α-HL protein nanopore was used as the adapter.Once Cu2+ was added from the cis chamber,and the formation and dissociation of Cu2+-TPPS can be successfully observed.Due to the different pathways of metal ions into the porphyrin ring cavity,the configuration of the Cu2+-TPPS complexes is different,and different current blocking signals are caused by different ways of interacting with the α-HL protein nanopores,thus realizing the understanding mechanism of metalloporphyrin at the single-molecular level.In addition,the intermediate(SAT complex)was captured in the process,which provided a new method for revealing the mechanism of porphyrin metallization.3.Nanopore sensor platform for detection of Cu2+ using TPPS as a recognition probe.In this section,organic small molecule TPPS was selected as a molecular probe,and α-HL protein nanopore was used as a reactor to achieve real-time detection of metal ion copper.In addition,we also investigated the effect of interference ions on the detection of Cu2+ ion(Mg2+,Al3+,Ca2+,Cr3+,Mn2+,Fe2+,Fe3+,Co2+,Ni2+,Zn2+,Ag+,Cd2+,Ba2+,Pd2+,Hg2+,and Pb2+).This promising sensing platform enables rapid and accurate detection of Cu2+ with a low detection limit(16 n M).Experiments of running water demonstrated the present method could be extended to Cu2+ detection in real samples.This investigation has also provided a methodology of designing and constructing nanopore biosensors with excellent selectivity and specificity for determination of biologically and environmentally relevant analytes by using desirable molecular recognition probes... |
PDF Full Text Request