Biomedical Engineering Reference
In-Depth Information
Fig. 1.34
Controllable moving of two biomolecule-water mixtures together. The
light greenlines
(linked hexagons) represent the SWNT. The colored spheres inside SWNT are the atoms of the
peptide. The
white spheres
outside the SWNT are the external charges (each has a value of
C
0.5
e
)
and the
red
-
white dots
are the water molecules
in the text (Ace-GNNQQNY-NMe) for demonstration. Each external charge has a
value of
C
0.5
e
. The counterion with a value of
1
e
is constrained at the edge of
the box.
There are many factors affecting the manipulation. First, let us discuss the
influence of the quantity of the external charge on the manipulation. Thermal
fluctuation will sometimes make the manipulation unsuccessful, but for
q
D˙
1.0
e
,
this is a rare event. When
q
D˙
0.5
e
, we have observed that the peptide-water
mixture follows the external charge in 8 of the 11 simulations for the same systems
with different initial conditions. In the cases where
q
D˙
0.33
e
and
˙
0.25
e
,the
peptide-water mixture has low probabilities to follow the external charge.
Second, we have found that the speed of the external charge has a remarkable
influence on the manipulation. When the speed of the external charge increases
from 1 to 10 m/s, only one successful manipulation is observed in ten simulations
with different initial conditions. We expect that as the speed of the external charge
decreases, the probabilities for these unsuccessful cases decrease. Usually, the speed
of the AFM/STM tip is within the magnitudes from 1 nm/s to 1 m/s. Considering
that the speed of the external charge in our simulation is up to 1 m/s, the rate
