Universal Relation between Instantaneous Diffusivity and Radius of Gyration of Proteins in Aqueous Solution

Protein conformational fluctuations are highly complex and exhibit long-term correlations. Here, molecular dynamics simulations of small proteins demonstrate that these conformational fluctuations directly affect the protein's instantaneous diffusivity D-I. We find that the radius of gyration R-g of the proteins exhibits 1/f fluctuations that are synchronous with the fluctuations of D-I. Our analysis demonstrates the validity of the local Stokes-Einstein-type relation D-I proportional to 1/(R-g + R-0), where R-0 similar to 0.3 nm is assumed to be a hydration layer around the protein. From the analysis of different protein types with both strong and weak conformational fluctuations, the validity of the Stokes-Einstein-type relation appears to be a general property.

Automated summary

The study demonstrates that protein conformational fluctuations directly affect the diffusion properties, showing synchronous fluctuations with diffusivity. The radius of gyration of proteins exhibits 1/f fluctuations. The validity of the Stokes-Einstein-type relation appears to be a general property based on analysis of different protein types.