Fluorescence Reporting Based on FRET Between Conjugated Polyelectrolyte and Organic Dye for Biosensor Applications - Advanced Fluorescence Reporters in Chemistry and Biology - page 441

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Lysozyme Nontarget Protein

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Scheme 11 The lysozyme detection mechanism ( left ) and the chemical structure ( right ) of poly
[9,9-bis(4 0 -sulfonatobutyl)fluorene- co -alt-1,4-phenylene] sodium salt (5)

good emission spectral overlap with the absorption of FAM. The detection starts
with a solution composed of 5 and FAM-labeled lysozyme aptamer. Since both
the polymer and the aptamer are negatively charged, they separate from each
other because of electrostatic repulsion and FRET does not occur in solution
upon excitation of 5 at 370 nm. Thus, as shown in Fig. 10 , there is no FAM
emission initially. In the presence of lysozyme, the aptamer specifically binds to
lysozyme, forming a complex with net positive charge. As a result, electrostatic
attraction between 5 and the aptamer/lysozyme complex occurs to bring 5 and
dye into close proximity for FRET to light up the FAM emission (Fig. 10 ). In
the presence of nonspecific proteins, there is no recognition between the lyso-
zyme aptamer and proteins, and the aptamer surface charge remains negative.
The distance between the lysozyme aptamer and the polymer remains too far for