Aminonaphthalimide fluorophore

One Lucifer Yellow derivative is available for labeling sulfhydryl-containing molecules. Lucifer Yellow iodoacetamide is a 4-ethyliodoacetamide derivative of the basic disulfonate aminonaphthalimide fluorophore structure (Molecular Probes). The io-doacetyl groups react with —SH groups in proteins and other molecules to form stable thioether linkages (Fig. 240). 

Compound 1 is poorly fluorescent because the emission has to compete with photoinduced electron transfer (PET)45 7 from the yV-arylaza-15-crown-5 ether receptor to the aminonaphthalimide fluorophore across the dimelhy-lene spacer. This receptor" successfully binds Na+ at the concentrations found in normal blood and is sufficiently selective against other ions like K" " and H" "." ... 

Another excellent example is Qian s 9 [46] with high selectivity in sensing. This was from a 2,6-bis(aminomethyl)pyridine receptor and also functions in neutral aqueous solution. Two aminonaphthalimide fluorophores are incorporated within this classic PET system. 

Recently, proton sponge was used as a fluorescent indicator for protons257. By incorporating the residue of 1 into the structure of the known fluorophore, 4-aminonaphthalimide, the researchers designed the fluorescent switch 274, whose synthesis was conducted in 5 steps with overall yield ca 10%. 

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