Shaped Laser Pulses for Microsecond Time-Resolved Cryo-EM: Outrunning Crystallization during Flash Melting

Area of Science:

• Cryo-electron microscopy
• Biophysics
• Materials science

Background:

• Vitrification of water is essential for cryo-electron microscopy (cryo-EM).
• Laser-induced heating of amorphous solid water (ASW) can lead to crystallization, potentially affecting protein dynamics in microsecond time-resolved cryo-EM.
• Current heating rates may not be sufficient to avoid crystallization during laser melting.

Purpose of the Study:

• To investigate methods for preventing crystallization in amorphous solid water (ASW) during laser-induced heating.
• To determine the critical heating rate required to outrun crystallization in ASW.
• To enhance the capabilities of microsecond time-resolved cryo-EM by optimizing laser heating protocols.

Main Methods:

• Utilizing shaped microsecond laser pulses to achieve higher heating rates.
• Employing time-resolved electron diffraction experiments to monitor ASW phase transitions.
• Analyzing the effects of rapid heating on amorphous ice structure.

Main Results:

• Shaped microsecond laser pulses can significantly increase heating rates.
• The critical heating rate for preventing crystallization in ASW was determined to be approximately 10^8 K/s.
• This method effectively outruns crystallization during laser melting of vitreous ice.

Conclusions:

• Shaped microsecond laser pulses offer a straightforward approach to avoid crystallization in ASW during laser melting.
• Achieving higher heating rates is crucial for the advancement of microsecond and potentially nanosecond time-resolved cryo-EM.
• This technique provides a valuable tool for studying dynamic processes in biological macromolecules with cryo-EM.