Protein labeling and tethering kit (cysteine)


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This kit applies cysteine–maleimide chemistry to attach DNA handles to your protein of interest for subsequent highresolution, singlemolecule optical tweezers measurements of protein folding and conformational changes. We recommend this labeling procedure over ybbR labeling, considering that it requires the absence of functional native cysteine residues on the protein of interest. For the DNA handles, two choices are available. The short handles (529 bp) will result in the highest force resolution, while the long handles (1506 bp) allow a more straightforward tethering procedure. 

For labeling, maleimide-modified oligonucleotides react with specifically incorporated cysteines in the protein. These oligonucleotides then anneal with the complementary 5’-overhangs of two DNA handles.

The kit also includes purified and functionalized adenosine kinase (AdK) that can be used as a control protein for each step of the labeling procedure.

Our protein labeling and tethering kit (cysteine) relieves you from costs and time that are typically required for personnel training, troubleshooting, experiment optimization, and custom application development. 

In case either additional protein labelings with oligonucleotides or additional measurements with handles are required, either maleimide-oligonucleotides or DNA handles can be ordered in separate packages. 

The kit enables 2 protein labelings with oligonucleotides (allowing up to 40 experimental sessions on the C-Trap per labeled protein) and supplies DNA handles for 10 experimental sessions on the C-Trap.

Estimated 1-3 weeks delivery time

Additional information

Short or long handles

Short DNA handles (529 bp), Long DNA handles (1506 bp)


Maleimide-modified oligonucleotides:

40 μl, 2 vials. Oligonucleotides for protein labeling using maleimide–cysteine chemistry. Store at -80°C.

Biotinylated and digoxigenin-labeled DNA handles (529 bp or 1506 bp):

45 μl, 1 vial. Handles mix (50/50) with an overhang that anneals with the maleimide-modified oligonucleotides. Store at -80°C.

TCEP (10 mM):

5 μl, 2 vials. Reducing agent. Store at -80°C.

6xHis AdK control protein (cysteine):

40 μl | 0.5 μg/μl (20 μM). Store at -80°C.

Streptavidin-coated polystyrene beads (⌀ 1.0–1.4 μm):

12 μl | 1% (w/v). Beads in PBS with 3 mM sodium azide, with a specific diameter (e.g., 1.2 μm) within the given range. Store at +4°C.

Anti-digoxigenin-coated polystyrene beads (⌀ 0.7–0.9 μm):

60 μl | 0.1% (w/v). Beads in PBS with 3 mM sodium azide, with a specific diameter (e.g., 0.8 μm) within the given range. Store at +4°C.

Product Resources

Want to learn more?

See our Protein Folding and Conformational Changes application notes.

Want to use this product in practice?

Find out more about the C-Trap here.

Download the Full Specifications or View the Experimental Protocols