His Tag is one of the most common amino acid tags used to produce recombinant proteins. It is usually 6 to 9 histidine residues fused to the N- or C- terminus of the recombinant protein.

The XpressCheck His Tag test strip is a competitive lateral flow assay-based technique for the rapid detection of His tagged proteins. The assay has a simple procedure and can be completed within 2 minutes without any instrument. The strip can be applied directly to unpurified samples in cell lysis buffer or cell culture medium (with or without PBS). It is also compatible with samples in water or different buffers such as PBS, Tris, or HEPES etc.

The test strip can be used to qualitatively detect the expression of His tagged proteins. With serial diluted samples the assay can also be carried out in a semi-quantitative manner to determine the concentration of the His tagged protein. It is an ideal tool for protein expression evaluation, optimization and colony selection. The detection limit of the strip is about 0.2 µM, corresponding to 10 µg/mL for a protein with a molecular weight of 50 kDa.

XpressCheck is a patent pending technique with improved sensitivity, compatibility, ease of use and shelf-life compared to traditional lateral flow products.