3.4 SIM
SIM is an SRN modality that achieves spatial resolution enhancement by
projecting light patterns over a fluorescent sample (Figure 2e)
(Gustafsson, 2000). The known structure of such patterns allows for
efficient deconvolution of the PSF and improved lateral resolution to
120 nm. Although the resolution improvement achieved with SIM is not as
high as that achieved with STED and SMLM techniques, its main advantage
is the ability to obtain fast imaging of dynamic processes and high
compatibility with the imaging of live samples. In GPCR research, SIM
has been used to localise βArrestin-2 in the membrane inside and outside
of clathrin-coated pits (Eichel et al., 2016) and detect the
differential segregation of activated β2AR molecules phosphorylated by
GPCR kinases (GRKs) and protein kinase A (Shen et al., 2018). SIM can be
used with a variety of fluorescent sensors, which increases the
flexibility of the experimental system design (Wang et al., 2019).