NuPAGE Bis-Tris Gel Performance Data

Neutral-pH buffers in NuPAGE Bis-Tris Gels deliver sharp straight bands. During separation, NuPAGE Bis-Tris Gels operate close to pH 7. In the Laemmli system, the gel is run at basic pH (pH ~9.5). At high pH the residual unpolymerized acrylamide can react with cysteine and lysine residues of the proteins being separated. This may affect downstream analysis such as western blot transfer. At the neutral pH of NuPAGE Bis-Tris Gels, these reactions take place several orders of magnitude more slowly than at the basic pH of tris-glycine gels, resulting in sharper bands and better resolution.

Sample preparation is a crucial step in successful protein analysis. The pH of the traditional Laemmli-style sample buffer changes from 6.8 to 5.2 when heated at 100°C. This lower pH is known to induce aspartyl-prolyl (Asp-Pro) peptide bond cleavage, which leads to protein degradation. By maintaining a >7.0 pH environment, the Invitrogen NuPAGE LDS Sample Buffer preserves protein integrity by minimizing this Asp-Pro cleavage. As seen below, the sample integrity is maintained throughout electrophoresis with the Invitrogen NuPAGE system; protein degradation is seen in samples prepared with Laemmli (tris-glycine) sample buffer. The Invitrogen NuPAGE Antioxidant running buffer additive greatly minimizes protein oxidation during electrophoresis and keeps reduced protein bands sharp and clear.