Physics (Internal)

SPECIAL CONDENSED MATTER BIOPHYSICS SEMINAR

This event is part of the Biophysics/Condensed Matter Seminar Series.

Abstract:
We are able to form and then image 10-100 nm diameter droplets of water
on a silicon nitride surface by irradiating a 100-200 nm thick column of
bulk water with a focussed electron beam of a transmission electron
microscope. The bulk water is enclosed in a liquid cell microfabricated
from silicon with thin silicon nitride windows and sealed from the
vacuum of the TEM. The droplets form by a process that resembles
spinodal decomposition. Various types of electron-beam dependent
dynamics are observed including droplet movement, collision and merging
of droplets, spontaneous and reversible appearance and disappearance of
droplets. These movements take place on silicon nitride rendered
hydrophilic by glow discharge. The liquid cells were developed to image
protein assemblies in room temperature liquid water. We have imaged a
crystalline bundle of actin filaments, the acrosomal process, at 120 kV
to a resolution of 2.7 nm. Surprisingly, radiation damage by the
electron beam is less in room temperature bulk water than in vitreous
ice cooled to liquid nitrogen temperatures.