Dedicated to Professor Julius Rebek, Jr. on the occasion of his 60th birthday Recent advances in stochastic DNA sensing technologies, [1] especially those that exploit the transmembrane protein pore a-hemolysin (a-HL), have led to the realization that rapid single-molecule DNA sequencing may be feasible. [2] As part of an ongoing study to better ascertain the nucleobase recognition capacity of a-HL and its potential utility in DNA sequencing, we report herein methods for capturing single-stranded DNA-poly(ethylene glycol) (DNA-PEG) hybrid molecules inside the a-HL pore. The DNA-a-HL rotaxanes were characterized at the single-species level by electrophysiological techniques and display a stable and reversible two-state switching capacity that depends on the applied potential, the orientation, and the method of threading and capture used.
Staphyloccocus aureus a-HL forms large heptameric protein pores in lipid bilayers. Its crystal structure shows a mushroom-shaped assembly with a central channel approximately 10 nm long with a diameter of 1.5 nm at the narrowest point. [3] Macrocyclic adapters have been shown to lodge inside and modify the conductance characteristics of the a-HL pore. This approach has been used to devise stochastic sensors for a range of small organic molecules. [4] In addition, the pore structure of a-HL can accommodate PEG molecules, which can be used either to measure the pore size [5] or in a-HL-based biosensors for protein recognition. [6] Nucleic acids
[*] Dr.