期刊
BIOPHYSICAL JOURNAL
卷 90, 期 3, 页码 1098-1106出版社
CELL PRESS
DOI: 10.1529/biophysj.105.070672
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资金
- NHGRI NIH HHS [R01 HG003713, R01-HG003713-01] Funding Source: Medline
- OCPHP CDC HHS [P41-PR05969] Funding Source: Medline
We have explored the electromechanical properties of DNA on a nanometer-length scale using an electric field to force single molecules through synthetic nanopores in ultrathin silicon nitride membranes. At low electric fields, E < 200 mV/10 nm, we observed that single-stranded DNA can permeate pores with a diameter >= 1.0 nm, whereas double-stranded DNA only permeates pores with a diameter >= 3 nm. For pores <3.0 nm diameter, we find a threshold for permeation of double-stranded DNA that depends on the electric field and pH. For a 2 nm diameter pore, the electric field threshold is similar to 3.1 V/10 nm at pH = 8.5; the threshold decreases as pH becomes more acidic or the diameter increases. Molecular dynamics indicates that the field threshold originates from a stretching transition in DNA that occurs under the force gradient in a nanopore. Lowering pH destabilizes the double helix, facilitating DNA translocation at lower fields.
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