Active Conformation Control of Unfolded Proteins by Hyperthermal Collision with a Metal Surface

The
physical and chemical properties of macromolecules like proteins
are strongly dependent on their conformation. The degrees of freedom
of their chemical bonds generate a huge conformational space, of which,
however, only a small fraction is accessible in thermal equilibrium.
Here we show that soft-landing electrospray ion beam deposition (ES-IBD)
of unfolded proteins allows to control their conformation. The dynamics
and result of the deposition process can be actively steered by selecting
the molecular ion beam’s charge state or tuning the incident
energy. Using these parameters, protein conformations ranging from
fully extended to completely compact can be prepared selectively on
a surface, as evidenced on the subnanometer/amino acid resolution
level by scanning tunneling microscopy (STM). Supported by molecular
dynamics (MD) simulations, our results demonstrate that the final
conformation on the surface is reached through a mechanical deformation
during the hyperthermal ion surface collision. Our experimental results
independently confirm the findings of ion mobility spectrometry (IMS)
studies of protein gas phase conformations. Moreover, we establish
a new route for the processing of macromolecular materials, with the
potential to reach conformations that would be inaccessible otherwise.