Elsevier

Micro and Nano Engineering

Volume 3, May 2019, Pages 31-36
Micro and Nano Engineering

Research paper
Microfabricated silicon chip as lipid membrane sample holder for serial protein crystallography

https://doi.org/10.1016/j.mne.2019.03.002Get rights and content
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Highlights

  • A concept for a sample holder for serial femtosecond crystallography under electrophysiological conditions is presented.

  • A simplified prototype has been realized in silicon and SU-8 technology

  • Impedance spectroscopy proved to be suitable for characterization of lipid bilayers formed within the device.

  • Lipid bilayers form within minutes on silicon nitride membranes with perforations of 0.2–12 μm in diameter.

Abstract

Rapid progress in protein crystallography techniques at X-ray free electron lasers (X-FELs) requires the development of new methods for sample delivery. Recording dynamic changes in protein structures is one of the aims. To assess protein dynamics, sample holders for crystallography need to become active devices, providing possibilities to induce in situ changes of the protein conformation during the experiments. We propose an integrated device for crystallographic studies on 2D crystals of membrane proteins. The conceptual device can support physiological conditions and provide a platform for electrophysiological measurements, as well as for electrical stimulation during the diffraction experiments at X-FELs. This allows for triggering conformational changes in membrane proteins, ultimately permitting to take series of crystallographic snapshots of the dynamic behavior of proteins. The device integrates a microfabricated silicon chip between two microfluidic transport layers. We demonstrate the fabrication of the device, describe its key components and show the method of sample loading and lipid bilayer formation with the use of the microfluidic delivery system. Electrochemical impedance spectroscopy (EIS) has been used to characterize the properties of lipid bilayers formed in the microfabricated silicon nitride support. Minimizing the sample consumption, mimicking physiological conditions during crystallographic data collection and an interface for electrochemical characterization and addressing protein 2D crystals are the key properties of the proposed device.

Keywords

Protein crystallography
X-ray free electron laser
Perforated silicon nitride membrane
Microfluidics
Black lipid membrane
Electrochemical impedance spectroscopy

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