Membrane-Embedded Channel of Bacteriophage Phi29 DNA-Packaging Motor for Translocation and Sensing of Double-Stranded DNA - Nanopores: Sensing and Fundamental Biological Interactions - page 93

a

pH = 2

b

pH = 7
Conductance: 2.73 ± 0.07 nS Conductance: 2.50 ± 0.11 nS

c

pH = 12

Conductance: 2.78 ±0.12 n S

Fig. 4.9 Current traces showing connector insertion accompanied by DNA translocation (20 bp
dsDNA) through the channel under (a)pH2;(b) pH 7; and (c) pH 12 in presence of 1 M NaCl at a
constant voltage of 75 mV. Figures reproduced with permissions from: Ref. [ 43 ], # The Royal
Society of Chemistry

of more liposomes to the chamber. The occurrence of such events can be minimized
simply by diluting the connector reconstituted liposomes.
DNA can also collide with the pore without actually traversing through it
giving rise to non-specific blockade events. This is especially prevalent in longer
length DNA, since an optimum conformation is necessary before the trans-
location can start. However, once the translocation starts, the likelihood of DNA
to diffuse back against the potential gradient is extremely unlikely.

4.5.5 Quantitative PCR Verifying the Translocation of dsDNA

To verify that the current blockade events were indeed the translocation of dsDNA
through the connector channels, quantitative PCR (Q-PCR) using the SYBR Green
kit (Bio-Rad) was used to quantify the translocation of DNA under a constant