Journal
NANO LETTERS
Volume 11, Issue 3, Pages 1098-1105Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nl103994w
Keywords
Nanoparticle; localized surface plasmon resonance; conformational change; ion sensor; calcium detection
Categories
Funding
- National Science Foundation [EEC-0647560, CHE-0911145, DMR-0520513, BES-0507036]
- National Cancer Institute [1 U54 CA119341-01]
- Ruth L. Kirschstein National Research Service [5 F32 GM077020]
- George W. Beadle Postdoctoral Fellowship
- Ryan Fellowship
- Direct For Mathematical & Physical Scien
- Division Of Chemistry [0911145] Funding Source: National Science Foundation
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The versatile optical and biological properties of a localized surface plasmon resonance (LSPR) sensor that responds to protein conformational changes are illustrated. The sensor detects conformational changes in a surface-bound construct of the calcium-sensitive protein calmodulin. Increases in calcium concentration induce a 0.96 nm red shift in the spectral position of the LSPR extinction maximum (lambda(max)). Addition of a calcium chelating agent forces the protein to return to its original conformation and is detected as a reversal of the lambda(max) shift. As opposed to previous work, this work demonstrates that these conformational changes produce a detectable shift in lambda(max) even in the absence of a protein label, with a signal:noise ratio near 500. In addition, the protein conformational changes reversibly switch both the wavelength and intensity of the resonance peak, representing an example of a bimodal plasmonic component that simultaneously relays two distinct forms of optical information. This highly versatile plasmonic device acts as a biological sensor, enabling the detection of calcium ions with a biologically relevant limit of detection of 23,mu M, as well as the detection of calmodulin-specific protein ligands.
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