Lucifer Yellow iodoacetamide

One Lucifer Yellow derivative is available for labeling sulfhydryl-containing molecules. Lucifer Yellow iodoacetamide is a 4-ethyliodoacetamide derivative of the basic disulfonate aminonaph-thalimide fluorophore structure (Invitrogen). The iodoacetyl groups react with —SH groups in proteins and other molecules to form stable thioether linkages (Figure 9.42). 

Figure 9.42 Lucifer Yellow iodoacetamide can be used to label sulfhydryl-containing molecules, forming thioether bonds.

The spectral characteristics of Lucifer Yellow iodoacetamide produce luminescence at somewhat higher wavelengths than the green luminescence of fluorescein, thus the yellow designation in its name. The excitation maximum for the probe occurs at 426 nm and its emission at 530 nm. The rather large Stoke s shift makes sensitive measurements of emission intensity possible without interference by scattered excitation light. The 2-mercaptoethanol derivative of the fluorophore has an extinction coefficient at pH 7 of about 13,000 M cm-1 at 426nm. 

Figure 5.15 Anionic dyes used in saccharide sensing. All compounds are shown as purchased or prepared. MPTS = methoxypyrenetrisulfonic acid, trisulfonate PTCA = perylenetetracarboxylic acid, tetracarboxylate HPTS = hydroxypyrenetrisulfonic acid, trisulfonate APTS = amino-pyrenetrisulfonic acid, trisulfonate fluorescein-SA = fluorescein-5-(and-6-)sulfonic acid lucifer yellow-I = lucifer yellow iodoacetamide SR-B = sulforhodamine-B HPTS(Lys)3 = hydroxypyrenetri(lysine) sulfonamide TCPP = tetrakis(4-carboxyphenyl)porphine TSPP = tetrakis(4-sulfophenyl)porphine.

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