Probing the binding modes and dynamics of histidine on fumed silica surfaces by solid-state NMR
| Autor: | Chengchen Guo, Michael Cao, Haley L. Swanson, J. Bennett Addison, Gregory P. Holland |
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| Rok vydání: | 2020 |
| Předmět: |
Materials science
Proton Magnetic Resonance Spectroscopy General Physics and Astronomy Protonation 02 engineering and technology 010402 general chemistry 01 natural sciences Adsorption Magic angle spinning Bound water Histidine Carbon-13 Magnetic Resonance Spectroscopy Physical and Theoretical Chemistry Density Functional Theory Fumed silica Aqueous solution Nitrogen Isotopes Chemical shift Water Hydrogen Bonding Silicon Dioxide 021001 nanoscience & nanotechnology 0104 chemical sciences Models Chemical Solid-state nuclear magnetic resonance Nanoparticles Physical chemistry Protons 0210 nano-technology |
| Zdroj: | Physical Chemistry Chemical Physics. 22:20349-20361 |
| ISSN: | 1463-9084 1463-9076 |
| Popis: | Silica nanoparticles can be designed to exhibit a diverse range of morphologies (e.g. non-porous, mesoporous), physical properties (e.g. hydrophobic, hydrophilic) and a wide range of chemical and biomolecular surface functionalizations. In the present work, the adsorption complex of histidine (His) and fumed silica nanoparticles (FSN) is probed using thermal analysis (TGA/DTG) and a battery of solid-state (SS) NMR methods supported by DFT chemical shift calculations. Multinuclear (1H/13C/15N) one- and two-dimensional magic angle spinning (MAS) SSNMR experiments were applied to determine site-specific interactions between His and FSN surfaces as a function of adsorption solution concentration, pH and hydration state. By directly comparing SSNMR observables (linewidth, chemical shift and relaxation parameters) for His-FSN adsorption complexes to various crystalline, amorphous and aqueous His forms, the His structural and dynamic environment on FSN surfaces could be determined at an atomic level. The observed 13C and 15N MAS NMR chemical shifts, linewidths and relaxation parameters show that the His surface layer on FSN has a significant dependence on pH and hydration state. His is highly dynamic on FSN surfaces under acidic conditions (pH 4) as evidenced by sharp resonances with near isotropic chemical shifts regardless of hydration level indicating a non-specific binding arrangement while, a considerably more rigid His environment with defined protonation states is observed at near neutral pH with subtle variations between hydrated and anhydrous complexes. At near neutral pH, less charge repulsion occurs on the FSN surface and His is more tightly bound as evidenced by considerable line broadening likely due to chemical shift heterogeneity and a distribution in hydrogen-bonding strengths on the FSN surface. Multiple His sites exchange with a tightly bound water layer in hydrated samples while, direct interaction with the FSN surface and significant chemical shift perturbations for imidazole ring nitrogen sites and some carbon resonances are observed after drying. The SSNMR data was used to propose an interfacial molecular binding model between His and FSN surfaces under varying conditions setting the stage for future multinuclear, multidimensional SSNMR studies of His-containing peptides on silica nanoparticles and other nanomaterials of interest. |
| Databáze: | OpenAIRE |
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