Longer-Lasting Electron-Based Microscopy of Single Molecules in Aqueous Medium

Area of Science:

• Materials Science
• Biophysics
• Electron Microscopy

Background:

• Electron microscopy of aqueous samples is limited by electron-induced damage, including water radiolysis and chemical degradation.
• Existing methods to mitigate damage, such as radical scavengers, have limitations.

Purpose of the Study:

• To investigate the use of deuterated water (D2O) in graphene liquid cells to improve sample stability during electron microscopy.
• To compare the effectiveness of D2O with traditional radical scavengers in mitigating electron-induced damage.

Main Methods:

• Transmission electron microscopy (TEM) experiments were conducted on aqueous liquid pockets within graphene liquid cells at room temperature.
• Experiments utilized common imaging conditions, varying electron voltage and dose.
• The stability of samples in D2O was compared to samples in H2O with radical scavengers.

Main Results:

• Deuterated water (D2O) significantly improved the stability of aqueous samples in graphene liquid cells.
• The lifetime of dissolved organic macromolecules increased by a factor of 2-5 in D2O compared to H2O.
• The appearance of radiolysis-induced bubbles was delayed by up to a factor of 10 in D2O.
• D2O increased sample longevity without compromising contrast critical for imaging weakly scattering molecules.

Conclusions:

• Deuterated water (D2O) is a superior method for enhancing sample stability in electron microscopy of aqueous samples compared to radical scavengers.
• The use of D2O enables longer observation times and better imaging of delicate organic macromolecules and biomolecules.
• This approach overcomes key limitations in electron-based microscopy of hydrated biological and organic samples.