Electrostatic Interactions and Protein Competition Reveal a Dynamic Surface in Gold Nanoparticle–Protein Adsorption
| Autor: | Mackenzie B. Davidson, Y. Randika Perera, Ailin Wang, Nicholas C. Fitzkee |
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| Rok vydání: | 2016 |
| Předmět: |
In situ
biology Chemistry Lysine Nanoparticle 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology Electrostatics 01 natural sciences Article 0104 chemical sciences Surfaces Coatings and Films Electronic Optical and Magnetic Materials Crystallography General Energy Adsorption Ubiquitin biology.protein Biophysics Physical and Theoretical Chemistry 0210 nano-technology Conjugate Protein adsorption |
| Zdroj: | The Journal of Physical Chemistry C. 120:24231-24239 |
| ISSN: | 1932-7455 1932-7447 |
| DOI: | 10.1021/acs.jpcc.6b08469 |
| Popis: | Gold nanoparticle– (AuNP–) protein conjugates are potentially useful in a broad array of diagnostic and therapeutic applications, but the physical basis of the simultaneous adsorption of multiple proteins onto AuNP surfaces remains poorly understood. Here, we investigate the contribution of electrostatic interactions to protein–AuNP binding by studying the pH-dependent binding behavior of two proteins, GB3 and ubiquitin. For both proteins, binding to 15-nm citrate-coated AuNPs closely tracks with the predicted net charge using standard pKa values, and a dramatic reduction in binding is observed when lysine residues are chemically methylated. This suggests that clusters of basic residues are involved in binding, and using this hypothesis, we model the pKa shifts induced by AuNP binding. Then, we employ a novel NMR-based approach to monitor the binding competition between GB3 and ubiquitin in situ at different pH values. In light of our model, the NMR measurements reveal that the net charge, binding association constant, and size of each protein play distinct roles at different stages of protein adsorption. When citrate-coated AuNPs and proteins first interact, net charge appears to dominate. However, as citrate molecules are displaced by protein, the surface chemistry changes, and the energetics of binding becomes far more complex. In this case, we observed that GB3 is able to displace ubiquitin at intermediate time scales, even though it has a lower net charge. The thermodynamic model for binding developed here could be the first step toward predicting the binding behavior in biological fluids, such as blood plasma. |
| Databáze: | OpenAIRE |
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