Native gel electrophoresis Under native PAGE conditions, polypeptides retain their higher-order structure and often retain enzymatic activity and interaction with other polypeptides. The migration of proteins depends on many factors, including size, shape, and native charge. The resolution of nondenaturing electrophoresis is generally not as high as that of SDS-PAGE, but the technique is useful when the native structure or enzymatic activity of a protein must be assayed following electrophoresis. One straightforward approach to native electrophoresis is to omit the SDS and reducing agent (DTT) from the standard Laemmli SDS protocol. Prepare the gels as described above, but do not put SDS or DTT in the sample buffer, do not heat the samples, and prepare the gel and tank buffer solutions without SDS.