High-Resolution 2D 1H−15N NMR Characterization of Persistent Structural Alterations of Proteins Induced by Interactions with Silica Nanoparticles

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Abstract
The binding of protein to solid surfaces often induces changes in the structure, and to investigate these matters we have selected two different protein−nanoparticle systems. The first system concerns the enzyme human carbonic anhydrase II which binds essentially irreversibly to the nanoparticles, and the second system concerns human carbonic anhydrase I which alternate between the adsorbed and free state upon interaction with nanoparticles. Application of the TROSY pulse sequence has allowed high-resolution NMR analysis for both of the protein−nanoparticle systems. For HCAII it was possible to observe spectra of protein when bound to the nanoparticles. The results indicated that HCAII undergoes large rearrangements, forming an ensemble of molten globule-like structures on the surface. The spectra from the HCAI−nanoparticle system are dominated by HCAI molecules in solution. A comparative analysis of variations in intensity from 97 amide resonances in a 1H−15N TROSY spectrum revealed the effects from interaction with nanoparticle on the protein structure at amino acid resolution.