Background Rejection with SPCE

These spectra demonstrate that the background from fluorophores distal from the metal can be suppressed by observing the SPCE, and suppressed further by observation of the SPCE with surface plasmon KR excitation. The fact that only fluorophores in proximity to the metal couple to surface plasmons opens up new possibilities for assays. The i etics of binding and conformational changes on the surface can be observed without a change in the quantum yield of the fluorescent probe. 

Measurement of DNA hybridization is now a central component of biotechnology and medical diagnostics. A variety of approaches are available to detect DNA hybridization including the use of intercalating fluorophores [36-37], dyes which bind to double stranded (ds) DNA [38-39], fluorescence resonance energy transfer [40-41], and excimer formation [42], In all these methods hybridization is detected by a change in the emission spectral properties of the probe which occurs upon formation of double-stranded DNA, typically an increased quantum yield of the fluorophore. 

Another advantage of SPCE is effective rejection of the emission from fluorophores more distant from the metal. This suppression occurs by two mechanisms, the decreased efficiency of coupling at larger distances from the metal and selective excitation near the metal when using the Kretschmann configuration. 

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