New APEX® Kits

IgG primary antibodies are usually available only in small quantities, can be expensive, and are packaged with stabilizing proteins such as bovine serum albumin (BSA). These stabilizing proteins can interfere with the amine-reactive reagents used to covalently attach a fluorescent label. Unfortunately, procedures to remove these stabilizing proteins may cause significant loss of antibody.

The APEX® Antibody Labeling Kits (Table 1) provide a convenient means of directly labeling a small amount of IgG antibody (10–20 µg) with a fluorescent label or biotin-XX moiety, while allowing you to easily remove contaminants (such as BSA) without losing antibody. These kits include all the reagents required to perform five separate IgG antibody labeling reactions using one of the superior Molecular Probes® fluorescent labels or biotin-XX. Additional APEX® kit configurations are now available, allowing you to select from Alexa Fluor®, Oregon Green® 488, or Pacific Blue™ fluorescent labels, or biotin-XX, a unique Molecular Probes® product that provides a 14-atom spacer between the antibody and the biotin moiety.

Table 1. Spectral Characteristics and Applications of the Labels Available in the APEX® Antibody Labeling Kits.
Fluorophore or Biotin Label
 Ex/Em * Application
Alexa Fluor® 488
496/519
Imaging or flow cytometry
Alexa Fluor® 555
555/565
Imaging
Alexa Fluor® 568
578/603
Imaging
Alexa Fluor® 594
590/617
Imaging
Alexa Fluor® 647
650/665
Imaging or flow cytometry
Oregon Green® 488
496/524
Imaging or flow cytometry
Pacific Blue™
416/451
Imaging or flow cytometry
Biotin-XX
NA
Imaging or flow cytometry
* Fluorescence excitation (Ex) and emission (Em) maxima, in nm.
† Newest additions to the APEX® Antibody Labeling Kit product line.

Easy Labeling Procedure

The APEX® labeling procedure is ingeniously easy. The kits contain pipette tips preloaded with a solid-phase resin that captures the antibody (Figure 1); simply apply the amine-reactive fluorescent label or biotin-XX moiety and your IgG antibody of choice to the resin. A fluorescent or biotin-XX–conjugated IgG antibody is formed, and the conjugate is then eluted from the resin using elution buffer. The IgG antibody conjugate is ready for use in an imaging or flow cytometry assay in as little as 2.5 hours, with minimal hands-on time. The typical yield of conjugated IgG antibody from the APEX® kits ranges from 40 to 80%.

APEX® antibody labeling tip 
Figure 1. Diagram of an APEX® antibody labeling tip.

 Time and Effort Without Sacrificing Performance

Using directly labeled antibodies eliminates the background fluorescence commonly observed when secondary antibodies bind nonspecifically to the sample. In addition, directly labeled antibodies allow you to use more than one same-species antibody in a single staining experiment. Effective conjugation of IgG antibodies using APEX® antibody labeling technology is demonstrated in Figure 2.

Effective conjugation of IgG antibody
Figure 2. Effective conjugation of IgG antibody with or without BSA. Bovine pulmonary artery endothelial (BPAE) cells were fixed and permeabilized, then (left panel) treated with mouse anti–α-tubulin, detected with secondary antibody (goat anti-mouse) labeled using the APEX® Biotin-XX Kit, and counterstained with Alexa Fluor® 488 Streptavidin (green fluorescence); or (right panel) treated with mouse anti–α-tubulin, and detected with secondary antibody (goat anti-mouse) labeled using the APEX® Alexa Fluor® 568 kit (red fluorescence) in the presence of 1% BSA. Nuclei were stained with blue-fluorescent DAPI.

Antibody and Protein Labeling Kits for Diverse Applications

In addition to the APEX® antibody labeling kits, we offer several antibody and protein labeling kits that use our superior Alexa Fluor® fluorescent dyes or Qdot® nanocrystals. Each type of kit has been optimized for a specific application (Table 2). Monoclonal antibody labeling kits, Qdot® antibody conjugate kits, SAIVI™ antibody labeling kits, and Zenon® IgG labeling kits are also available. Learn more about our diverse selection of labeling technologies at APEX® Antibody Labeling Kits.

Table 2. Molecular Probes® Antibody and Protein Labeling Kits.
Amount of IgG
Product Key Features
<1–20 µg
Zenon® IgG Labeling Kits
  • Labeled IgG antibodies ready to use in 10 min
  • Isotype-specific labeling
  • Fast, noncovalent attachment of label
  • Labeling compatible with stabilizing proteins such as BSA
10–20 µg
APEX® Antibody Labeling Kits
  • Labeled IgG antibodies ready to use in 2.5 hr (~15 min hands-on time)
  • Covalent attachment of label
  • Labeling compatible with stabilizing proteins such as BSA
20–100 µg
Microscale Protein Labeling Kits
  • Labeled antibodies or other proteins ready to use in 2 hr (~30 min hands-on time)
  • Covalent attachment of label
  • Optimized for proteins between 10 and 150 kDa, including IgG antibodies (~150 kDa)
  • Stabilizing proteins must be removed from sample before labeling
100 µg
Monoclonal Antibody Labeling Kits
  • Labeled IgG antibodies ready to use in 90 min (~15 min hands-on time)
  • Covalent attachment of label
  • Optimized for IgG antibodies (~150 kDa)
  • Stabilizing proteins must be removed from sample before labeling
  • Designed to label polyclonal and monoclonal IgG antibodies
300 µg
Qdot® Antibody Conjugation Kits
  • Label antibodies with the very bright and extremely photostable Qdot® nanocrystals
  • Covalent attachment of Qdot® nanocrystal
  • Optimized for IgG antibodies (~150 kDa)
  • Eight different Qdot® nanocrystals are available
1 mg
Protein Labeling Kits
  • Labeled antibodies ready to use in 2 hr (~30 min hands-on time)
  • Covalent attachment of label
  • Optimized for IgG antibodies (~150 kDa)
  • Stabilizing proteins must be removed from sample before labeling
0.3–5 mg
SAIVI™ Antibody Labeling Kits
  • Labeled IgG antibodies ready to use in 90 min (~10 min hands-on time)
  • Covalent attachment of Alexa Fluor® near-IR labels
  • Optimal degree of labeling for in vivo imaging applications
  • Labeled antibodies ready for use in applications that require azide-free reagents, such as live-cell imaging or direct injection into animals
For Research Use Only. Not intended for any animal or human therapeutic or diagnostic use.