NuPAGE® Bis-Tris gels are precast polyacrylamide gels designed to give optimal separation of small to medium-sized proteins during gel electrophoresis. NuPAGE® Bis-Tris gels have a neutral pH environment that minimizes protein modifications resulting in sharper bands without typical gel "smiling" (Figure 1). NuPAGE® Bis-Tris gels can be used for sequencing, mass spectrometry, and any other application in which protein integrity is crucial.

NuPAGE® Bis-Tris gels are designed to allow:

  • Separation of a wide range of molecular weight proteins
  • Preservation of protein sample integrity
  • Faster run times (completed in as little as 35 minutes)
  • A longer shelf life (16 months* at room temperature without loss of performance)
  • Using gels from another company? Use the product selection guide to find our equivalent

*from date of manufacture

See the Bis-Tris gel migration charts

Choose the right NuPAGE® Bis-Tris gel

Number of wells Gel thickness Gel percentage Gel sizes

Find the right minigel using our interactive gel selection tool.

All of our mini gels will run in the XCell SureLock® Mini-Cell as well as our new Mini Gel Tank.

Figure 1. Side-by-side comparison of Bis-Tris gels.


A. Bio-Rad Criterion™ XT 4-12% Bis-Tris Gel w/ MOPS, and B. NuPAGE® Novex 4–12% Bis-Tris Midi Gel w/ MOPS. Each lane contains 5 µL Mark12™ Unstained Standard.

Getting started with NuPAGE® Bis-Tris gels

Get optimal separation of your proteins by choosing the right combination of gel and running buffer. Available concentrations, sizes, and buffer systems are given below.

Polyacrylamide concentrations
NuPAGE® Bis-Tris mini gels are available in 3 different polyacrylamide concentrations: 10%, 12%, and 4–12% gradient. We also offer 8% gels in the midi gel format.

Gel sizes
NuPAGE® Bis-Tris gels are available as mini gels (10 cm x 10 cm) and midi gels (8.7 cm x 13.3 cm). Both mini gels and midi gels are available with 1.0 mm gel thickness. The 1.5 mm gel thickness is only available with the mini gel format. For loading volumes, see Recommended Well Loading Volumes & Sample Loads.

Buffering systems
NuPAGE® Bis-Tris gels are Bis-Tris-HCl buffered (pH 6.4) and have an operating pH of about 7.0. All of the gels can be run using either NuPAGE® MES SDS or NuPAGE® MOPS SDS running buffer to obtain different separation ranges.

Protein size

Proteins (14–200 kDa)
Use NuPAGE® Bis-Tris Gels with NuPAGE® MOPS SDS Running Buffer to resolve proteins (14–200 kDa).

Small molecular weight proteins (2–200 kDa)
Use NuPAGE® Bis-Tris Gels with NuPAGE® MES SDS Running Buffer to resolve small molecular weight proteins (2–200 kDa).

The NuPAGE® Bis-Tris discontinuous buffer system involves three ions:

  • Chloride (–) from the gel buffer and serves as a leading ion due to its high affinity to the anode relative to other anions in the system. The gel buffer ions are Bis-Tris+ and Cl– (pH 6.4).
  • MES or MOPS (–) serve as the trailing ion in the running buffer. The running buffer ions are Tris+, MOPS-/MES–, and dodecylsulfate- (pH 7.3–7.7).
  • Bis-Tris (+) is the common ion present in the gel buffer and running buffer. The combination of the lower pH gel buffer (pH 6.4) and the running buffer (pH 7.3–7.7) results in a significantly lower operating pH of 7 during electrophoresis.

Novex® Bis-Tris gel migration charts

Figure 2. Migration patterns of Mark12™ Unstained Standard on NuPAGE® Bis-Tris Gels and NuPAGE® Tris-Acetate Gels. For optimal results, protein bands should migrate within the yellow shaded areas.