VMXm - A sub-micron focus macromolecular crystallography beamline at Diamond Light Source

Area of Science:

• Structural Biology
• Biophysical Chemistry
• X-ray Crystallography

Background:

• Macromolecular crystallography (MX) is crucial for determining protein structures.
• Collecting high-quality data from microcrystals (<10 µm) presents significant challenges.
• Existing beamlines often struggle with small crystal signal-to-noise ratios.

Purpose of the Study:

• Introduce VMXm, a novel beamline optimized for microcrystal rotation data collection.
• Enhance signal-to-noise and crystal lifetime for microcrystal X-ray diffraction.
• Enable exploration of measurements at the physical limits of MX.

Main Methods:

• Utilized a fully focused beam (0.3 × 2.3 µm) with tuneable energy (6-28 keV) and high flux.
• Housed crystals in a vacuum chamber to minimize air scatter.
• Employed plunge-cooling on cryo-electron microscopy grids and in-vacuo scanning electron microscopy for sample visualization.

Main Results:

• Achieved optimized rotation data collection from microcrystals down to below 1 µm.
• Improved signal-to-noise ratios through vacuum containment and reduced cryo-protectant.
• Prolonged microcrystal lifetime by exploiting photoelectron escape.

Conclusions:

• VMXm significantly advances the capabilities for studying microcrystals using X-ray crystallography.
• The beamline's design pushes the boundaries of structural determination for challenging biomacromolecular samples.
• VMXm provides unprecedented opportunities for high-resolution structural biology research.