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Map-likelihood phasing.
1Bioscience Division, Mail Stop M888, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. terwilliger@lanl.gov
Acta Crystallographica. Section D, Biological Crystallography
|November 22, 2001
Summary
Maximum-likelihood density modification provides accurate crystallographic phase probabilities, minimizing bias. This technique enhances electron-density map quality for improved macromolecular structure determination.
Area of Science:
- Crystallography
- Structural Biology
- Biophysics
Background:
- Maximum-likelihood density modification is a recently developed technique.
- It allows calculation of phase probabilities based on electron-density map likelihood, separate from prior phase calculations.
Purpose of the Study:
- To demonstrate the accuracy and low bias of phase-probability distributions calculated solely from the map-likelihood function.
- To explore the application of this method in various crystallographic scenarios.
Main Methods:
- Utilizing the map-likelihood function to calculate phase-probability distributions.
- Implementing prime-and-switch phasing to mitigate model bias.
- Applying the technique to datasets with solvent content as low as 30%.
Main Results:
- Phase-probability distributions derived from map-likelihood alone are highly accurate.
- These distributions exhibit minimal bias towards initial phases.
- The method is effective even with limited prior phase information or low solvent content.
Conclusions:
- Map-likelihood phasing offers a robust method for accurate phase determination in macromolecular crystallography.
- It has broad potential applications including unbiased phase calculation, iterative model building, and ab initio structure determination.
- The prime-and-switch technique effectively removes model bias, leading to more reliable electron-density maps.