Atomic-scale Propagated Brownian Fluctuations from Protein Molecules to Single Nanoparticles

Yuji C. Sasaki

Biomedical Group, Spring-8/JASRI, JST/CREST SASAKI-team, 1-1-1 Kouto, Mikazuki-cho, Sayou-gun, Hyougo-ken 679-5198, Japan



The main themes of protein engineering research focus on controlling molecular functions and improving molecular physical and chemical stability. Modern synthetic organic chemistry and biogenetics offer the opportunity to modify arbitrary sites on a protein molecule, and recently, inorganic nanomaterials have sparked intense interest for their molecule-like characteristics. However, researches on hybrid functional molecules containing inorganic nanomaterials as building blocks are scarce due to the lack of structural fluctuations in inorganic matters. Undoubtedly, the most fundamental characteristic of functional proteins is conformational fluctuations for recognizing ligands and other molecules. Here, we report propagated Brownian fluctuations of single nanoparticles that are specifically linked to Actin filaments in several aqueous conditions using super-high accuracy single-molecular measurements, we called, Diffracted X-ray Tracking (DXT). As a result, the fluctuations of the Actin filaments were precisely propagated to a labeled single nanoparticle through the single covalent bond. For example, in these DXT measurements, the observed motions in the presence of Mg2+ ions under the one-to-one labeling reaction between the labeled gold nanoparticles and the cysteine sites in G-actin are more condensed than those in the presence of Ca2+ ions. Consistent with these structural differences, Ca-F-actin was significantly known more flexible than Mg-F-actin.