Membrane-protein binding measured with solution-phase plasmonic nanocube sensors
1] Howard Hughes Medical Institute, University of California, Berkeley, California, USA.  Department of Chemistry, University of California, Berkeley, California, USA.  Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA. Nature Methods
(Impact Factor: 32.07).
10/2012; 9(12). DOI: 10.1038/nmeth.2211
We describe a solution-phase sensor of lipid-protein binding based on localized surface plasmon resonance (LSPR) of silver nanocubes. When silica-coated nanocubes are mixed in a suspension of lipid vesicles, supported membranes spontaneously assemble on their surfaces. Using a standard laboratory spectrophotometer, we calibrated the LSPR peak shift due to protein binding to the membrane surface and then characterized the lipid-binding specificity of a pleckstrin homology domain protein.
Available from: Aditi Das
- "In addition to SPR, plasmonic biosensing can be accomplished by localized surface plasmon resonance (LSPR) and extraordinary optical transmission (EOT). In LSPR, the electric field near metal nanoparticles is amplified resulting in strong scattering spectra ideal for applications in protein biosensing (Anker et al., 2008; Baciu et al., 2008; Wu et al., 2012 ). Unlike SPR, which uses a metallic thin film and prism system, LSPR does not require a complex system in order to couple the light source to the metal dielectric interface (Haes and Van Duyne, 2004). "
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ABSTRACT: Cytochrome P450s are the primary enzymes involved in phase I drug metabolism. They are an important target for early drug discovery research. However, high-throughput drug screening of P450s is limited by poor protein stability and lack of consistent measurement of binding events. Here we present the detection of substrate binding to cytochrome P450-2J2 (CYP2J2), the predominant P450 in the human heart, using a combination of Nanodisc technology and a nanohole plasmonic sensor called nanoplasmonic Lycurgus cup array (nanoLCA). The Nanodisc, a nanoscale membrane bilayer disc, is used to stabilize the protein on the metallic plasmonic surface. Absorption spectroscopy of seven different substrates binding to CYP2J2 in solution showed that they are all type I, resulting in shifting of the protein bands to lower wavelengths (blue shift). Detection on the nanoLCA sensor also showed spectral blue shifts of CYP2J2 following substrate binding. Finite Difference Time Domain (FDTD) electromagnetic simulation suggested that the blue shift on the nanoLCA is because of the hybridization of plasmon polariton Bloch wave and the electronic resonance of the heme group of CYP2J2. We found the plasmonic properties of the nanoLCA sensor to be highly reproducible, which allowed comparisons among the different substrates at different concentrations. Further, due to the unique spectral properties of the nanoLCA sensor, including the transmission of a single color, we were able to perform colorimetric detection of the binding events. These results indicate that a resonance plasmonic sensing mechanism can be used to distinguish between different substrates of the same binding type at different concentrations binding to P450s and that the nanoLCA sensor has the potential to provide consistent high-throughput measurements of this system.
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Available from: Andrea Armani
- "In waveguide interferometer sensors, where the detection signal is typically a change in optical power, an increase in power results in an improved signal-to-noise ratio . In surface plasmon or resonant cavity based sensors, an increase in power corresponds to a narrower resonance linewidth, improving the resolution of the measurement . Therefore, it is critical that the surface functionalization does not decrease the optical power confined within the device. "
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ABSTRACT: Whispering gallery mode optical microcavities have significantly impacted the field of label-free optical biodetection. By combining the evanescent field generated by the microcavity with biomimetic surface chemistries, it is now possible to use the microcavities as not only biosensors, but as analytical tools to explore fundamental chemical and physical interactions of biomolecules and biomaterials. Here, we review the recent advancements of these applications from a surface chemistry perspective. For example, surface chemistries can be generated from a standard coating perspective, where active molecules, such as laser or fluorescent dyes can be embedded in a biomaterial matrix. Alternatively, direct and reverse grafting techniques can be used to tether biomolecules of interest to the surface to tune the surface properties (hydrophobicity/hydrophilicity, protein adsorption, cell adhesion, etc.). Finally, we discuss how to apply advancements in biomimetic chemistry from other sensor approaches to these devices to continue the development of new analytical tools. All of these developments rely on a firm understanding of how proper surface chemistries can be merged with whispering gallery mode optical microcavities to achieve not just a platform, but a precisely defined tool for a given application.
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ABSTRACT: This review paper presents the overview of processes involved in transformation of organic-coated silver nanoparticles (AgNPs) in biological systems and in the aquatic environment. The coating on AgNPs greatly influences the fate, stability, and toxicity of AgNPs in aqueous solutions, biological systems, and the environment. Several organic-coated AgNPs systems are discussed to understand their stability and toxicity in biological media and natural water. Examples are presented to demonstrate how a transformation of organic-coated AgNPs in an aqueous solution is affected by the type of coating, pH, kind of electrolyte (mono- or divalent), ionic strength, organic ligands (inorganic and organic), organic matter (fulvic and humic acids), redox conditions (oxic and anoxic), and light. Results of cytotoxicity, genotoxicity, and ecotoxicity of coated AgNPs to food chain members (plants, bacteria, and aquatic and terrestrial organisms) are reviewed. Key factors contributing to toxicity are the size, shape, surface coating, surface charge, and conditions of silver ion release. AgNPs may directly damage the cell membranes, disrupt ATP production and DNA replication, alternate genes expressions, release toxic Ag+ ion, and produce reactive oxygen species to oxidize biological components of the cell. A progress made on understanding the mechanism of organic-coated AgNPs toxicity using different analytical techniques is presented.
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