ChromoBlog

Flag®-tag (or DYKDDDDK-tag) is a commonly used short peptide tag for multiple applications such as immunoprecipitation (IP), protein purification, immunofluorescence, and Western blotting (WB). In this blog, we provide an introduction to the IP of Flag®-tagged proteins from cellular extracts. Using our DYKDDDDK Fab-Trap™ as an example, we elaborate on the different steps of IP and highlight the controls that help you achieve the best result in your experiment.

Different antibody formats can be used in IP applications, including full-length antibodies, Fab-fragments, and Nanobodies. ChromoTek’s Fab-Trap™ is an IP reagent based on an antibody Fab-fragment. In this blog, we elaborate on the basic principle and advantages of Fab-fragment based reagents for IP. More simply, we ask “Why is the Fab-Trap™ Fab-ulous?”

Immunoprecipitation (IP) is a technique used to isolate a protein from a cellular extract. The protein of interest (POI) is recognized by a specific antibody (Ab) conjugated to beads. Different antibody formats can be used in IP, e.g., a full-length Ab, a Fab-fragment, or a Nanobody. Below, we discuss the advantages and limitations of the different Ab formats.

ChromoTek and Proteintech recently launched Nanobodies against the SARS-CoV-2 virus. These Nanobody clones were originally developed by the group of Ulrich Rothbauer at the Natural and Medical Sciences Institute, Reutlingen, Germany. In our guest blog, Teresa Wagner and Ulrich Rothbauer discuss the development of these Nanobodies and why Nanobodies are versatile alternatives to classical antibodies in SARS-CoV-2 research.

Co-immunoprecipitation (Co-IP) describes the isolation of a protein and its binding partners from a cell extract using a Nanobody or antibody that is bound to beads. The protein, that directly interacts with the Nanobody, or antibody beads is called “bait”. The binding partner that is indirectly precipitated is called “prey”.

Co-IP describes the immunoprecipitation of a protein of interest and its interacting partners.

1. What is Flag-Tag?

1. What is GFP?

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Protein abundance is crucial for immunoprecipitation

During an immunoprecipitation (IP), the protein of interest (POI) is pulled down with a specific antibody or Nanobody conjugated to beads such as agarose or magnetic agarose. Unbound sample content, for example, other proteins, cell debris, and lipids, is removed by washing, while the precipitated protein is enriched on the beads.