Determination of crystallographic intensities from sparse data.

Area of Science:

• Structural Biology
• Crystallography
• Biophysics

Background:

• X-ray serial microcrystallography collects diffraction data from microcrystals.
• Radiation damage limits X-ray photon counts per frame, especially for small crystals.
• Sparse data frames, too weak for orientation determination, are typically discarded.

Purpose of the Study:

• To demonstrate that sparse diffraction data frames, unorientable on a per-frame basis, can be effectively utilized in crystallography.
• To challenge the assumption that sparse frames limit microcrystal size analysis in serial microcrystallography.

Main Methods:

• Application of the Extended Maximum Likelihood (EMC) algorithm to sparse crystallographic data.
• Reconstruction of 3D diffraction intensity from unoriented sparse data frames.
• Proof-of-principle experiment using a 1.35 kDa molecule crystal.

Main Results:

• Successful reconstruction of 3D diffraction intensity from sparse data frames.
• Demonstration that data too sparse for per-frame orientation can be merged effectively.
• Validation of the EMC algorithm's utility for processing sparse crystallographic data.

Conclusions:

• Serial microcrystallography is not fundamentally limited by X-ray source fluence.
• Complete data sets are feasible even with limited photon counts per frame.
• This method opens possibilities for analyzing smaller microcrystals and using lower-fluence X-ray sources.