Purify and Conjugate Antibodies in a Single Workflow

Isoform_Antibodies_LinkedInAntibodies labeled with small molecules such as fluorophore, biotin or drugs play a critical role in various areas of biological research,drug discovery and diagnostics. There are several limitations to current methods for labeling antibodies including the need for purified antibodies at high concentrations and multiple buffer exchange steps.

In a recent publication, a method (on-bead conjugation) is described that addresses these limitations by combining antibody purification and conjugation in a single workflow. This method uses high capacity-magnetic Protein A or Protein G beads to capture antibodies directly from cell media followed by conjugation with small molecules and elution of conjugated antibodies from the beads.

Using a variety of fluorophores the researchers show that the on-bead conjugation method is compatible with both thiol- and amine-based chemistry.

This method enables simple and rapid processing of multiple samples in parallel with high-efficiency antibody recovery. It is further shown that recovered antibodies are functional and compatible with downstream applications.

Literature Cited

Nidhi, N. et al. (2015) On-bead antibody-small molecule conjugation using high-capacity magnetic bead J. Immunol. Methods  http://dx.doi.org/10.1016/j.jim.2015.08.008

Screening for Protein Activity Using Cell-Free Expression

The analysis of functional protein typically requires lengthy laborious cell based protein expression that can be complicated by the lack of stability or solubility of the purified protein. Cell free protein expression eliminates the requirement for cell culture thus providing quick access to the protein of interest (1).

The HaloTag® Technology provides efficient, covalent and oriented protein immobilization of the fusion protein to solid surfaces (2).

A recent publication demonstrated the feasibility of using cell free expression and the HaloTag technology to express and capture a fusion protein for the rapid screening of protein kinase activity (3). The catalytic subunit of human cAMP dependent protein kinase was expressed in a variety of cell free expression formats as a HaloTag fusion protein. The immobilized cPKA fusion protein was assayed directly on magnetic beads in the active form and was shown to be inhibited by known PKA inhibitory compounds.

Therefore this unique combination of protein expression and capture technologies can greatly facilitate the process of activity screening and characterization of potential inhibitors

References
ResearchBlogging.org

  1. Zhao, K.Q. et al. (2007) Functional protein expression from a DNA based wheat germ cell-free system. J. Struc. Funct. Genomics. 8, 199-208.
  2. Los, G.V. and Wood, K. (2007) The HaloTag: A novel technology for cell imaging and protein analysis. Meth. Mol. Biol. 356, 195-208
  3. Leippe DM, Zhao KQ, Hsiao K, & Slater MR (2010). Cell-free expression of protein kinase a for rapid activity assays. Analytical chemistry insights, 5, 25-36 PMID: 20520741