PUB - Publikationen an der Universität Bielefeld

Driving small molecules, such as DNA, electrophoretically through a nanometre-sized pore provides single-molecule sensitivity and analytical properties (e.g. sequencing) without prior molecular amplification and necessity for labeling. Theoretical and experimental investigations indicate that the forces, which contribute to this translocation process, depend on an interplay of ionic screening and hydrodynamics. Therefore, it is of essential importance to study and characterize these threading forces to gain a deeper understanding of the underlying mechanisms. Utilizing optical tweezers, the experimental results presented here have expanded the force measurements in solid-state nanopores to include a surface modification by a lipid bilayer coating. It was demonstrated that the DNA threading forces increased by 80 % compared to an uncoated nanopore of the same size. Thus, these findings led to a more comprehensive theoretical description of polyelectrolyte dynamics in the highly confined environment of a nanopore. In addition, a fundament of preparation techniques was explored and established, to demonstrate that it is possible to produce nanopore-spanning and thus, freestanding lipid bilayer membranes. It was shown that these lipid bilayers were stable for hours and suitable for the incorporation of α-hemolysin (a pore-forming protein). Furthermore, free translocation experiments with DNA-oligomers through this biological pore were conducted successfully. Based on this technological fundament, it will be feasible to conduct optical tweezers threading force measurements on these bio-logical pores, in order to provide prospective influential insights, as well as additional contributions to an unambiguous theoretical model.