Adsorption kinetics of an engineered gold binding Peptide by surface plasmon resonance spectroscopy and a quartz crystal microbalance.
ABSTRACT The adsorption kinetics of an engineered gold binding peptide on gold surface was studied by using both quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) spectroscopy systems. The gold binding peptide was originally selected as a 14-amino acid sequence by cell surface display and then engineered to have a 3-repeat form (3R-GBP1) with improved binding characteristics. Both sets of adsorption data for 3R-GBP1 were fit to Langmuir models to extract kinetics and thermodynamics parameters. In SPR, the adsorption onto the surface shows a biexponential behavior and this is explained as the effect of bimodal surface topology of the polycrystalline gold substrate on 3R-GBP1 binding. Depending on the concentration of the peptide, a preferential adsorption on the surface takes place with different energy levels. The kinetic parameters (e.g., K(eq) approximately 10(7) M(-1)) and the binding energy (approximately -8.0 kcal/mol) are comparable to synthetic-based self-assembled monolayers. The results demonstrate the potential utilization of genetically engineered inorganic surface-specific peptides as molecular substrates due to their binding specificity, stability, and functionality in an aqueous-based environment.
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ABSTRACT: The aim of this study was the development of a bifunctional protein crosslinker-based surface plasmon resonance (SPR) biosensor for rapid detection of aflatoxin B-1 (AFB(1)), a potent carcinogen. A fusion protein was obtained by genetically fusing gold binding protein (GBP) that binds strongly to gold surfaces to protein G (ProG) that interacts with the Fc portion of antibodies. It was used as a bifunctional crosslinker for rapid self-oriented immobilization of antibodies on gold substrates without any chemical treatment. SPR analyses demonstrated the binding of the GBP-ProG crosslinker to the gold surface was superior to that of an only ProG via currently used self-assembled monolayers of alkanethiol due to the GBP property. As a result, anti-AFB(1) antibodies were 36% more immobilized on the GBP-ProG layer than the ProG layer. When the GBP-ProG crosslinker-based SPR chips were fabricated with the best density (100 mu g/mL) of anti-AFB(1) antibodies, they could detect AFB(1) as low as 1 mu g/mL in both buffer and corn extracts and selectively detect it with negligible SPR responses in control toxins (zearalenone and ochratoxin A). These results mean the GBP-ProG is more useful than the thiolated chemical linkers for development of gold substrate-based immunosensors, and this GBP-ProG crosslinker-based immunosensor could detect small molecules effectively.Food Control 02/2014; 36(1):183-190. DOI:10.1016/j.foodcont.2013.08.038 · 2.82 Impact Factor
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ABSTRACT: Controllable 3D assembly of multicomponent inorganic nanomaterials by precisely positioning two or more types of nanoparticles to modulate their interactions and achieve multifunctionality remains a major challenge. The diverse chemical and structural features of biomolecules can generate the compositionally specific organic/inorganic interactions needed to create such assemblies. Toward this aim, we studied the materials-specific binding of peptides selected based upon affinity for Ag (AgBP1 and AgBP2) and Au (AuBP1 and AuBP2) surfaces, combining experimental binding measurements, advanced molecular simulation, and nanomaterial synthesis. This reveals, for the first time, different modes of binding on the chemically similar Au and Ag surfaces. Molecular simulations showed flatter configurations on Au and a greater variety of 3D adsorbed conformations on Ag, reflecting primarily enthalpically driven binding on Au and entropically driven binding on Ag. This may arise from differences in the interfacial solvent structure. On Au, direct interaction of peptide residues with the metal surface is dominant, while on Ag, solvent-mediated interactions are more important. Experimentally, AgBP1 is found to be selective for Ag over Au, while the other sequences have strong and comparable affinities for both surfaces, despite differences in binding modes. Finally, we show for the first time the impact of these differences on peptide mediated synthesis of nanoparticles, leading to significant variation in particle morphology, size, and aggregation state. Because the degree of contact with the metal surface affects the peptides ability to cap the nanoparticles and thereby control growth and aggregation, the peptides with the least direct contact (AgBP1 and AgBP2 on Ag) produced relatively polydispersed and aggregated nanoparticles. Overall, we show that thermodynamically different binding modes at metallic interfaces can enable selective binding on very similar inorganic surfaces and can provide control over nanoparticle nucleation and growth. This supports the promise of bionanocombinatoric approaches that rely upon materials recognition.Chemistry of Materials 09/2014; 26(17):4960-4969. DOI:10.1021/cm501529u · 8.54 Impact Factor