Protein-Labeling Reagents

While dansyl chloiide today seems like a common fluorophore, its Introduction by Professor Weber represented a fundamental change in the paradigm of fluorescence spectroscopy. One of Professor Weber s main contributions was the introduction of molecular considerations Into fluorescence spectrosetpy. The dansyl group is solvent sensitive, and one is thus forced to consider its interactions with its local environment. Professor Wfeber recognized that proteins could be labeled with fluorophores, which in turn reveal information about the proteins and their interactions with other molecules. The probes which the Professor developed are still in widespread use, including dansyl chloride, ANS, TNS, and Prodan derivatives. 

One common use of fluorescein and rhodamine is for labeling of antibodies. A witfe variety of fluorescein- and rhodamine-Iabeled immunoglobulins are commercially available, and these proteins are frequently used in fluores- 

One problem widi fluorescein is its t ency to self-quench. It is well known that the brightness of fluorescein- 

As a result, die dyes transfer to each odier widi a FOrster distance of about 57 A. 

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Acceptor group within the protein Labeling reagent (carrying a radioactive isotope)... 

This is a protein labeling reagent which readily reacts with amines and other nucleophilic functional groups. This reagent has been used, for example, to study the glucagon receptor in hepatocyte plasma membranes lodosulfanilic acid... 

It is a protein labeling reagent which preserves the charge on the protein and is relatively stable in aqueous media Succinic anhydride... 

K. Stroffekova, C. Proenza, K. Beam, The protein-labeling reagent FLASH-EDT2 binds not only to CCXXCC motifs but also non-specifically to endogenous cysteine-rich proteins, Pflugers Arch. 

The first series of metallo-carbonyl protein labeling reagents was designed from the popular Bolton-Hunter radio-iodination reagent 48 intended for antibody radiolabeling [85]. 

Fluorescent labeling requires care. Unless the protein is completely labeled, which requires heroic effort, incomplete labeling converts each protein into a complex mixture of reaction products. We find that the use of FQ as the labeling reagent and the use of an SDS-containing buffer produces extremely high-efficiency separations of labeled proteins. 

Khalfan, H., Abuknesha, R., Rand-Weaver, M., Price, R.G., and Robinson, D. (1986) Aminomethyl cou-marin acetic acid A new fluorescent labeling reagent for proteins. Histochem. /. 18, 497-499. 

Several fluorine-18-labelled reagents for coupling to peptides and proteins have been described (Fig. 8). Most of them were designed for coupling with the amino function of an amino acid residue (A/-terminal a-NH2 or internal lysine E-NH2) or... 

Fig. 8. Fluorine-18-labelled reagents for coupling with peptides and proteins via amino or carboxylic acid functions.

Dissolve or buffer-exchange the antibody at 4 mg protein/mL in PBS devoid of amine-, thiol-, and carbonyl-containing additives, since these components will also react with the labeling reagent. Do not cover or cap the container. 

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