The advent
of high-speed atomic force microscopy (HS-AFM)
has opened
a novel research field for the dynamic analysis of single unlabeled
bio-molecules. The integration of a non-disturbing buffer exchange system,
allowing
the gradual change of the environmental conditions during HS-AFM operation,
provides a breakthrough towards the performance of structural titration
experiments. Analyzing membrane proteins in membranes and under controlled
exposure to environmental stimuli, we report conformational changes of a
transporter in response to substrates,
of receptors and of ion channels
upon ligand
binding.
Altogether,
we showcase the unique potential of HS-AFM, providing ~1nm lateral, ~0.1nm
vertical and ~100ms temporal resolution, for visualizing
the dynamics of membrane
proteins, label-free
and in close-to-native conditions.