Protein orientation in time-dependent electric fields: orientation before destruction.

Area of Science:

• Biophysics
• Structural Biology
• Computational Chemistry

Background:

• Proteins possess electric dipole moments enabling interaction with external electric fields.
• Controlling protein orientation is crucial for techniques like single-particle imaging (SPI) using X-ray Free-Electron Lasers (XFELs).
• Previous theoretical models assumed constant or step-function electric fields, unlike realistic smooth pulses.

Purpose of the Study:

• To investigate the orientation of gas-phase proteins using time-dependent electric fields.
• To determine the minimal electric field strength required for protein orientation.
• To assess the structural integrity of proteins during electric field exposure.

Main Methods:

• Ab initio simulations to estimate protein bond-breaking field strength (45 V/nm).
• Classical molecular dynamics simulations of ubiquitin in time-dependent electric fields.
• Analysis of protein structure preservation during orientation.

Main Results:

• The minimal electric field strength for orienting ubiquitin within 10 ns is approximately 0.5 V/nm.
• Protein structures remained intact until orientation was achieved, irrespective of field strength.
• A principle termed "orientation before destruction" was observed, where orientation precedes structural damage.

Conclusions:

• Time-dependent electric fields offer a viable method for orienting gas-phase proteins.
• Low electric fields (around 0.5 V/nm) are sufficient for rapid protein orientation.
• The "orientation before destruction" principle suggests that protein structure can be preserved during controlled orientation, enhancing SPI applications.