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Use of the minimal function for partial structure development in direct methods
D A Langs1, R Miller, H A Hauptman
1Medical Foundation of Buffalo, NY 14203.
Summary
The novel shake-and-bake procedure significantly enhances molecular fragment recycling. This method is highly effective even with low-resolution data and imperfect initial models, improving crystallographic structure determination.
Area of Science:
- Structural biology
- Crystallography
- Computational chemistry
Background:
- Molecular fragment recycling is crucial for solving complex crystallographic structures.
- Traditional methods like tangent-formula recycling have limitations with imperfect models and low-resolution data.
Purpose of the Study:
- To evaluate the efficacy of the shake-and-bake procedure for molecular fragment recycling.
- To compare the performance of shake-and-bake against traditional tangent-formula methods.
Main Methods:
- The shake-and-bake procedure, based on the minimal function, was applied to molecular fragment recycling.
- Performance was assessed based on the probability of obtaining a solution from correctly positioned fragments.
- Tolerance to root-mean-square (r.m.s.) model errors was evaluated.
Main Results:
- The shake-and-bake method demonstrated high effectiveness in molecular fragment recycling.
- Fragments constituting as little as 5% of scattering power had a 50% success rate per trial.
- The procedure tolerated r.m.s. model errors exceeding 0.5 Å, significantly more than traditional methods.
Conclusions:
- Shake-and-bake is a robust and effective procedure for molecular fragment recycling.
- It outperforms traditional methods in challenging crystallographic applications, including those with pseudosymmetric molecules or low-resolution data.