1 research outputs found
Apparent Anomalous Diffusion in the Cytoplasm of Human Cells: The Effect of Probes’ Polydispersity
This
work, based on <i>in vivo</i> and <i>in vitro</i> measurements, as well as <i>in silico</i> simulations,
provides a consistent analysis of diffusion of polydisperse nanoparticles
in the cytoplasm of living cells. Using the example of fluorescence
correlation spectroscopy (FCS), we show the effect of polydispersity
of probes on the experimental results. Although individual probes
undergo normal diffusion, in the ensemble of probes, an effective
broadening of the distribution of diffusion times occursî—¸similar
to anomalous diffusion. We introduced fluorescently labeled dextrans
into the cytoplasm of HeLa cells and found that cytoplasmic hydrodynamic
drag, exponentially dependent on probe size, extraordinarily broadens
the distribution of diffusion times across the focal volume. As a
result, the <i>in vivo</i> FCS data were effectively fitted
with the anomalous subdiffusion model while for a monodisperse probe
the normal diffusion model was most suitable. Diffusion time obtained
from the anomalous diffusion model corresponds to a probe whose size
is determined by the weight-average molecular weight of the polymer.
The apparent anomaly exponent decreases with increasing polydispersity
of the probes. Our results and methodology can be applied in intracellular
studies of the mobility of nanoparticles, polymers, or oligomerizing
proteins