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On the correlation between the main-chain and side-chain atomic displacement parameters (B values) in high-resolution
1Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India.
Summary
Correlation coefficients for atomic displacement parameters in proteins vary widely. Their distribution depends on refinement software and protocols, impacting strategies for X-ray diffraction studies.
Area of Science:
- Structural Biology
- Crystallography
- Computational Biology
Background:
- Atomic displacement parameters (B values) describe atomic motion in protein structures.
- Correlation coefficients (CCs) between main-chain and side-chain B values range from 0.5-1.0 in high-resolution protein structures.
Purpose of the Study:
- To investigate the factors influencing the distribution of CCs between atomic displacement parameters.
- To understand the impact of refinement software and protocols on B-value correlations.
Main Methods:
- Analysis of correlation coefficients (CCs) between B values of main-chain and side-chain atoms.
- Examination of the relationship between CCs and the mean difference in B values of Calpha and Cbeta atoms.
- Comparison of CC distributions across different refinement packages (X-PLOR, PROLSQ, TNT).
Main Results:
- CC distribution is linked to the mean difference in B values between Calpha and Cbeta atoms.
- High CCs correlate with frequent occurrences of consecutive Calpha atoms with high B values.
- CC distribution patterns are dependent on the refinement package used, indicating variations in B-value constraint handling.
Conclusions:
- Differences in refinement packages (X-PLOR, PROLSQ, TNT) influence B-value correlation patterns.
- Variations within the same refinement package suggest the impact of specific protocols and weighting schemes.
- Understanding these B-value distribution features is crucial for refining atomic displacement parameters in protein X-ray diffraction and developing validation tools.