ABC Spotlight on single-molecule detection
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EDITORIAL
ABC Spotlight on single-molecule detection Günter Gauglitz 1 Received: 20 July 2020 / Accepted: 21 July 2020 # The Author(s) 2020
More than 50 years ago, key historical experiments started to detect single molecules using transmission electron microscopy. It began with DNA molecules and proteins, later on came globulin protein molecules in aqueous solution which was more difficult, but allowed measuring the biological molecules in their native state by using fluorescent tags. In the following decades, a large number of methods were developed using super-resolution imaging, near-field scanning microscopy, photo-activated localization microscopy, stimulated depletion microscopy, or superresolution fluorescence microscopy [1]. Recently, the trends in single-molecule bioanalytical detection with regard to labelbased far-field single-molecule imaging, label-free near-field detection of single-molecule interactions, and the suitability for single-molecule clinical assays have been reviewed [2], demonstrating that‚ at these expected very low concentrations, widefield capturing in label-based single-molecule assays has potential and now it is already used in commercially available kits. From the beginning of this century, two different approaches regarding the application of single-molecule detection emerged. In one approach, the focus was on monitoring and characterizing a single biological molecule at an interface such as a membrane, measuring cell signaling processes at the membrane or interactions of a single molecule with other molecules. With this approach, the behavior of single molecules in the surroundings or even in cells was in the focus to study dynamics and structure dependence on interactions [3]. Thus, experiments of molecular motors or molecular machines and cell signaling‚ as well as protein dynamics and protein folding‚ were published. As an example, the manipulation of DNA molecules by motor proteins at the single-molecule level is shown [4]. Localization as a tool to restrict effects to extremely small areas created the idea of tailoring nanopores to separate and characterize single molecules. It is
* Günter Gauglitz [email protected] 1
Institute for Theoretical and Physical Chemistry, Eberhard-Karls-University, Tübingen, Germany
considered to be promising to get fundamental knowledge in transport kinetics in glycomics and DNA sequencing [5]. Recently, a nanopore sequencer using protein nanopores has been achieved to sequence a single-molecule base without DNA synthesis or amplification [6]. Furthermore, plasmonic properties of nanoparticles can be used either for information about the interaction of single molecules on these nanoparticles with ligands [7] or allow surface-enhanced Raman spectroscopy [8]. For the characterization of processes in cells, nanoelectrochemistry can also be used, e.g., nanoresolved SECM (scanning electrochemical microscopy). This nanoelectrochemistry can reach high sensitivity, even down to the single-molecule level, and can be used to study sin
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