3 research outputs found
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
Generating in-Plane Orientational Order in Multilayer Films Prepared by Spray-Assisted Layer-by-Layer Assembly
We present a simple
yet efficient method for orienting cellulose
nanofibrils in layer-by-layer assembled films through spray-assisted
alignment. While spraying at 90° against a receiving surface
produces films with homogeneous in-plane orientation, spraying at
smaller angles causes a macroscopic directional surface flow of liquid
on the receiving surface and leads to films with substantial in-plane
anisotropy when nanoscale objects with anisotropic shapes are used
as components. First results with cellulose nanofibrils demonstrate
that such fibrils are easily aligned by grazing incidence spraying
to yield optically birefringent films over large surface areas. We
show that the cellulosic nanofibrils are oriented parallel to the
spraying direction and that the orientational order depends for example
on the distance of the receiving surface from the spray nozzle. The
alignment of the nanofibrils and the in-plane anisotropy of the films
were independently confirmed by atomic force microscopy, optical microscopy
between crossed polarizers, and the ellipsometric determination of
the apparent refractive index of the film as a function of the in-plane
rotation of the sample with respect to the plane of incidence of the
ellipsometer
Spray-Deposited Anisotropic Assemblies of Plasmonic Nanowires for Direction-Sensitive Strain Measurement
The development of nanoscale composites with hierarchical
architecture
and complex anisotropies enables the fabrication of new classes of
devices. Stretchable strain sensors have been developed in the past
for applications in various fields such as wearable electronics and
soft robotics, yet the sensing capacities of most of these sensors
are independent of the direction of deformation. In the present work,
we report on the preparation of a direction-sensitive strain sensor
using the anisotropic optical properties of a monolayer of oriented
plasmonic 1D nano-objects. Grazing incidence spraying (GIS) is used
for depositing a monolayer of in-plane aligned silver nanowires with
a controlled density on a deformable and transparent substrate. Using
the selective excitation of transverse and longitudinal localized
plasmon resonance modes of silver nanowires by polarized UV–visible–NIR
spectroscopy, we show that the macroscopic anisotropic properties
of the monolayer upon stretching are highly dependent on the stretching
direction and light polarization. Measuring the polarized optical
properties of the anisotropic thin films upon stretching thus allow
for retrieving both the local strain and the direction of the deformation
using a simple model