Voltage Dependence Of Frequency Research Articles

Interaction of Cucurbituril Molecular Containers with the Aerolysin Nanopore for Molecular Recognition

Cucurbit[n]urils (CBn) are molecular containers which form complexes with various guest molecules, such as amino acids and peptides. Here we report the ionic current block and reversible binding of different CBn of sizes n=5, n=6, n=7 and n=8 with the aerolysin (Ael) protein nanopore. CBn molecular containers enter the Ael nanopore exclusively from the extracellular cap domain and under a trans negative voltage. We attempt to relate differential effects of the electrolytes KCl, NaCl, CsCl and LiCl and of the ionic strength on the voltage-dependence of frequency and dwell-time. Notably, the current blockade frequency as well as the current blockade duration increase with increasing the magnitude of applied voltage. Our results suggest that CBn behave as positively charged molecular containers and trans negative voltage promotes their blocking the Ael pore lumen for up to several seconds. Our approach could be used for rapid and real-time probing of the abilities of different CBn to form host-guest complexes with various guest molecules.

On the Frequency-Voltage Dependence Profile of Complex Dielectric, Complex Electric Modulus and Electrical Conductivity in Al/ZnO/p-GaAs Type Structure at Room Temperature

On the Frequency-Voltage Dependence Profile of Complex Dielectric, Complex Electric Modulus and Electrical Conductivity in Al/ZnO/<i>p</i>-GaAs Type Structure at Room Temperature

Electrophoresis and Electroosmosis in Aerolysin and Hemolysin Nanopores

Voltage-dependent interaction of macromolecules with biological nanopores can arise from electroosmotic (EOF) or electrophoretic (EPF) forces. Both poly(ethylene-glycol) (PEG), and cyclodextrins (β- and α-CD, respectively) block the ionic current through α-hemolysin (αHL) and Aerolysin (AeL) pore-forming proteins with well-documented voltage-dependence. Here, we attempt to relate differential effects of the electrolytes KCl and LiCl on the voltage-dependence of frequency and dwell-time of blocks to the relative contributions of EOF and EPF.For AeL, irrespective of electrolyte, blocks by α-CD only occurred from the pore's cis-side and with trans-positive voltages. Blocks in LiCl were much longer than those in KCl (11ms vs. 760μs at 90mV) but dwell times showed a positive, linear voltage dependence in both cases (LiCl:6fold/100mV; KCl:3fold/100mV). In KCl, cis-side PEG blocked AeL with trans-negative voltages only.1 Surprisingly, in LiCl, blocks occurred only at trans-positive voltages and at more than 1000 fold PEG-concentration but we still are in a very diluted regime. Blocks were shorter than in KCl by a factor of 5 (60 vs. 320μs at 100mV), but frequency (3fold/100mV) and dwell time (2fold/100mV) depended linearly on voltage, reminiscent of the behavior of α-CD in both electrolytes.Linear voltage dependence of block frequency might indicate dominance of EOF for pore entry of PEG in LiCl and for α-CD generally, while an exponential voltage-dependence would be expected for an electrophoretic force. Indeed, for PEG in KCl, which may be positively charged due to K+-chelation (see Ref.1 for discussion), we found an exponential increase in frequency for blocks of AeL and αHL with increasing trans-negative and trans-positive voltages, respectively. We cannot, however, exclude voltage and ion-dependent effects on the binding reaction, which, rather than partitioning, may be rate-limiting for the electrophysiologically detectable blockages.(1)Baaken, G.; et al. ACS Nano 2015, 6443-6449