The origin of protein sidechain order parameter distributions.

Area of Science:

• Biophysics
• Structural Biology
• Computational Chemistry

Background:

• Previous studies indicated multimodal distributions for NMR order parameters of protein side chains.
• These distributions suggested distinct "classes" of motion, but lacked a clear molecular-level explanation.

Purpose of the Study:

• To re-evaluate the multimodal distribution of NMR order parameters for protein side chains.
• To provide a physical explanation for these observed distributions using molecular dynamics simulations.

Main Methods:

• Analysis of an expanded dataset of published NMR order parameter data.
• Molecular dynamics (MD) simulations of protein dynamics.

Main Results:

• The analysis confirmed a multimodal distribution of NMR order parameters.
• Evidence for three distinct "classes" of motion was found to be weak.
• A simple physical explanation for the observed distributions was derived from MD simulations.

Conclusions:

• The multimodal distribution of protein side chain NMR order parameters is a real phenomenon.
• Molecular dynamics simulations offer a valuable tool for understanding the physical basis of these distributions.
• This work enhances the interpretation of NMR dynamics data in structural biology.