Sulfhydryl-Reactive Fluorescein Derivatives

The iodoacetamido derivatives of fluorescein possess a sulfhydryl-reactive iodoacetyl group (Chapter 1, Section 4.2 and Chapter 2, Section 2.1) at either the 5- or 6-carbon position on their lower ring. The isomers are commercially available in purified form, since some reactivity and specificity differences between the 5- and 6-derivatives toward various sulfhydryl sites in proteins may be observed. Both iodoacetamido derivatives are among the most intense fluoro-phores available for labeling biomolecules due to high QY. 

The iodoacetamido derivatives of fluorescein possess a sulfhydryl-reactive iodoacetyl group (Chapter 1, Section 4.2, and Chapter 2, Section 2.1) at either the 5- or 6-carbon... 

SAMSA-fluorescein, 5- [2(and 3)-5-(acetylmercapto)-succinoyl]amino fluorescein, is a fluorescent probe containing a protected sulfhydryl group. In its protected state, the compound is unre-active. The acetyl-protecting group can be removed by treatment with dilute NaOH at pH 10.0 (Figure 9.9). The resulting free sulfhydryl derivative can be used to label thiol-reactive crosslinkers or to couple with sulfhydryl residues on proteins and other molecules. After activating... 

Extending the utility of fluorescence to various nonfluorophores is achieved via chemical derivatization methods, also termed labeling or tagging methods (Reaction 11.2). Numerous commercial fluorescent tags are available with disparate reactive functional groups. For example, derivatives of fluorescein, fluorescein isothiocyanate (FITC) are reactive toward nucleophiles such as amines and sulfhydryl groups. 

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