Microscale Protein Labeling Kits conveniently label small amounts (20–100 μg) of purified protein or antibodies with a bright, photostable Alexa Fluor® dye or biotin-XX.
  • Convenient—labeled proteins ready in 2 hours, requiring approximately 30 minutes actual hands-on time
  • Versatile—label proteins with molecular weights between 12 and 150 kDa, including IgG antibodies (~150 kDa) and quantities ranging from 20–100 µg
  • Reliable—protein conjugates with stable attachment of fluorescent labels or haptens

Microscale Protein Labeling Kit selection guide

Flow cytometry
Cat. No.
Alexa Fluor® 488

Alexa Fluor® 555

Alexa Fluor® 594

Alexa Fluor® 647


Biotin-XX (includes additional biotin quantitation assay)

Ex/Em = Fluorescence excitation and emission maxima, in nm.
Find more information about Alexa Fluor® dyes and other fluorophores in the Fluorophore Selection Guide

How Microscale Protein Labeling Kits work

The Microscale Protein Labeling Kits use an amine-reactive fluorophore or biotin to covalently attach the label to the protein or IgG antibody. Once formed, the covalent bond between the label and the protein is extremely stable; you are using the same chemistry we use to prepare our own primary and secondary conjugates.

Unlike our other antibody labeling kits, these kits have been optimized for labeling proteins between 12 and 150 kDa, and so have utility in labeling antibodies as well as other proteins in that size range.

Any stabilizing proteins (e.g., BSA), must be removed prior to the labeling reaction. Convenient spin columns purify the labeled protein (Figure 1) with yields between 60 and 90%, depending on the molecular weight of the starting material. The entire labeling and purification procedure can be completed in as little as 2 hours—everything needed to perform three conjugations is provided in the kits.

Need to label other antibody amounts?

IgG amount Attachment of label Products
<1–20 µg Site-specific Zenon® Antibody Labeling Kits
<100 µg Site-specific SiteClick™ Antibody Labeling Kits
10–20 µg Conventional covalent APEX® Antibody Labeling Kits
20–100 µg Conventional covalent Microscale Protein Labeling Kits
100 µg Conventional covalent Antibody Labeling Kits
1 mg Conventional covalent Protein Labeling Kits
0.5–3 mg Conventional covalent SAIVI™ Rapid Antibody Labeling Kits