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of nanoplatforms as essential intermediates in nascent cell adhesion.
67
Since raft association with a variety of membrane proteins other than LFA-
1 has been documented, we proposed that hotspots regions enriched with
raft components and functional receptors may constitute a prototype of
nanoscale inter-receptor assembly and correspond to a generic mechanism
to offer cells with privileged areas for rapid cellular function and responses
to the outside world.
(a)
(b)
Figure 9.6.
(a) Dual-colour confocal image of the integrin receptor LFA-1 (red) and
GPI-anchored proteins (green) on the cell membrane of monocytes. The large extent
of yellow patches on the image resulting from the lack of suficient spatial resolution
suggests colocalization of LFA-1 and GPIs. (b) Dual-colour super-resolution NSOM
demonstrates that in the resting state, LFA-1 and GPIs do not colocalize at the
nanometre scale and reside in different nanocompartments of the cell membrane.
Image adapted with permission from Ref. 67. © (2009) National Academy of Sciences,
USA.
9.4 FUTURE PROSPECTS IN NSOM
The examples summarized in this chapter clearly illustrate the potential of
NSOM as a quantitative microscopy tool for biological imaging. Nevertheless,
the technical complexities associated with NSOM have limited so far its
widespread use in the biological community. In turn, far-ield super-resolution
approaches are gaining increasing importance in the last two to three years.
From the technical point-of-view, one of the major challenges of NSOM is the
fabrication of bright, robust and truly nanometre-sized probes required for
high resolution. In aperture-type of illumination NSOM, only a small fraction
(10
) of the light coupled to the ibre is emitted through the aperture,
resulting in low transmission. Together with the inite skin depth of the metal,
the practical resolution is thus constrained to ~50 nm. Fortunately, recent
4
to 10
6
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