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An envelope-based approach for direct phase determination of macromolecular structures
1Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena 91125.
Acta Crystallographica. Section A, Foundations of Crystallography
|November 1, 1990
Summary
This study introduces a novel method to derive initial electron density distributions from diffraction data. The approach uses an eigenvalue equation to generate potential distributions, improving crystal structure analysis.
Area of Science:
- Crystallography
- Structural Biology
- Computational Chemistry
Background:
- Accurate initial electron density distribution is crucial for crystal structure determination.
- Traditional methods can be computationally intensive and prone to errors.
Purpose of the Study:
- To develop a direct method for deriving initial electron density distributions from observed diffraction data.
- To formulate the electron density derivation as an eigenvalue problem for efficient computation.
Main Methods:
- Maximizing the product of observed and calculated Patterson functions.
- Formulating the problem as an eigenvalue equation yielding eigendensities (eigenvectors).
- Selecting and combining eigendensities based on correlation coefficients.
Main Results:
- Demonstrated a direct method for obtaining electron density distributions.
- Achieved phase errors less than 60 degrees for strong low-resolution reflections in lysozyme.
- Developed an extension for crystal structures with non-crystallographic symmetry.
Conclusions:
- The eigenvalue-based method provides a direct and potentially more accurate way to derive initial electron density.
- This approach can reduce phase errors, aiding in crystal structure determination.
- The method is adaptable for complex crystal structures including non-crystallographic symmetry.