Direct structural and dynamic characterization of protein conformers in solution is highly desirable but currently impractical. Herein, we developed a single molecule gold plasmonic nanopore system for observation of protein allostery, enabling us to monitor translocation dynamics and conformation transition of proteins by ion current detection and SERS spectrum measurement, respectively. Allosteric transition of calmodulin (CaM) was elaborately probed by the nanopore system. Two conformers of CaM were well-resolved at a single-molecule level using both the ion current blockage signal and the SERS spectra. The collected SERS spectra provided structural evidence to confirm the interaction between CaM and the gold plasmonic nanopore, which was responsible for the different translocation behaviors of the two conformers. SERS spectra revealed the amino acid residues involved in the conformational change of CaM upon calcium binding. The results demonstrated that the excellent spectral characterization furnishes a single-molecule nanopore technique with an advanced capability of direct structure analysis.

More anomalous transport behaviors have been observed with the rapid progress in nanofabrication technology and characterization tools. The ions/molecules inside nanochannels can act dramatically different from those in the bulk systems and exhibit novel mechanisms. Here, we have reported the fabrication of a nanodevice, covalent organic frameworks covered theta pipette (CTP), that combine the advantages of theta pipette (TP), nanochannels framework, and field-effect transistors (FETs) for controlling and modulating the anomalous transport. Our results show that ammonia, a weak base, causes a continuous supply of ions inside covalent organic framework (COF) nanochannels, leading to an abnormally high current depending on the ionic/molecular size and the pore size of the nanochannel. Furthermore, CTP can distinguish different concentrations of ammonia and have all of the qualities of a nanosensor.