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VRDye Protein Labeling Kits

VRDye™ Protein Labeling Kits label antibodies and other proteins for applications such as flow cytometry, microscopy, immunohistochemistry, and other applications where fluorophore-conjugated antibodies are required. VRDye labeling kits are cost-effective alternatives to expensive, time-consuming, custom antibody labeling services. The High MW kits are optimized for labeling 1 mg of an IgG antibody. The High MW-Microscale kits are optimized for labeling 100 µg of an IgG antibody. These kits may also be used to label proteins spanning the molecular weight range of 50 kDa to 200 kDa.

VRDye labeling kits are based on a simple conjugation protocol that uses fast, spin column cleanup with resulting purity equivalent to purification by dialysis. Raise the pH of the preservative-free protein solution with the provided buffer, combine it with the appropriate amount of water-soluble amine-reactive IRDye, and separate the labeled conjugate from the free dye using the included spin columns. Labeling and purification are complete in approximately 2 hours.

The visible dyes included in these kits are activated with N-hydroxysuccinimide (NHS) esters, which is the most commonly used reactive group for labeling proteins. NHS esters react with primary amines, forming stable, covalent bonds.

Table 1. Properties of Visible NHS Dyes

Dye Absmax Emmax ε(M-1cm-1) MW (g/mole) CF*
IRDye 650 648 655 230,000 1097 0.03
VRDye 549 550 575 150,000 1040 .07
VRDye 490 491 515 73,000 1011 0.11

*CF is a correction factor for the absorbance of the dye at Absmax to the absorbance of the protein at 280 nm.

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