Chemistry Reference
In-Depth Information
Figure 12.7 Streptavidin on mica-supported planar lipid bilayers.
(a) Streptavidin 2D crystals formed on bilayers of
DOPC
þ
DOPE
biotin. Scale bar, 30 nm. (b) Streptavidin on
-
bilayers of DPPC
biotin. Scale bar, 40 nm; imaging rate,
0.18 s/frame. (c) Streptavidin on bilayers of
DPPC
þ
DPPE
-
þ
DOPE
biotin. Scale bar, 40 nm; imaging rate,
-
0.18 s/frame.
dynamic nanostructures on living cells, currently an impossible task due to the
extremely soft nature of living cell membranes. To date, nc-AFM has been realized
only in a vacuum where cantilevers can have a large Q. However, the cantilevers
response speed decreases with increasing Q. Therefore, it is incompatible with high-
speed imaging. We require a non-contact condition that is compatible with canti-
levers having a small Q. Although still unproven, one possibility is the use of
ultrasonic interference between the cantilever tip and the sample by exciting them
ultrasonically at different frequencies f
1
and f
2
(f
1
, f
2
f
2
|, is
set close to the cantilevers resonant frequency. This con
guration (Figure 12.8) is
the same as that employed for scanning near-
f
c
). The difference, |f
1
eld ultrasound holography (SNFUH)
that has recently been developed for high-resolution sub-surface imaging [44].
