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Related Experiment Videos

Ab initio direct methods: practical advice for getting beyond the first 300 atoms.

D A Langs1

  • 1Medical Foundation of Buffalo, NY 14203, USA.

Acta Crystallographica. Section D, Biological Crystallography
|January 1, 1993
PubMed
Summary

Direct methods can solve large crystal structures (>300 atoms) when data quality is high and phase relationships are favorable. Careful evaluation and computational resources are key for successful phasing.

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Area of Science:

  • Crystallography
  • Structural Biology
  • Biophysics

Background:

  • Direct methods are a primary tool for solving crystal structures.
  • However, their applicability diminishes with increasing molecular complexity.
  • Phasing large molecular structures (>300 atoms) remains a significant challenge.

Purpose of the Study:

  • To provide guidelines for evaluating the feasibility of direct methods for large structures.
  • To identify key factors influencing successful phasing outcomes.
  • To encourage practitioners by demonstrating occasional successes with challenging datasets.

Main Methods:

  • Analysis of crystallographic data quality and derivation of E values.
  • Assessment of phase relationships and their stability.

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  • Prognostic evaluation for recognizable solutions using post-mortem case studies.
  • Review of computational resource requirements and practitioner effort.

    • Main Results:

    • Not all crystallographic datasets are amenable to direct phasing.
    • Data quality, phase relationships, and a favorable a priori prognosis are critical.
    • Large structures (>300 atoms) can occasionally be solved with current methods.
    • Success depends on adequate computational power and persistent effort.

    Conclusions:

    • Direct methods can be applied to large molecular structures under specific conditions.
    • A thorough pre-analysis of data and expected outcomes is essential.
    • Success is achievable with careful planning, sufficient resources, and dedicated effort.