Prestained Protein Ladder

•  Broad MW range (10-250 kD)
• Dual-Color or Tri-Color
• Precise molecular weights (MWs) 
• Clear and sharp bands
• Optimized membrane binding affinity
• High storage stability
• Compatible with NIR fluorescent system

BMD prestained protein ladder PM201 and three other popular ladders were compared with two unstained protein MW standards on a 4-15% gradient gel. As shown, two prestained ladders (#26616 and #26619) showed obvious inconsistency with the unstained protein MW standards (#26630) from the SAME manufacturer (lane 4, 5 vs lane 2). These two prestained ladders are even inconsistent with each other although they are both from Thermo (lane 4 vs lane 5). Generally, unstained protein MW standards are more precise than prestained ladders. By calibrating with the two unstained MW standards, one can find that four bands of Thermo’s ladders (100 kD, 35 kD, 15 kD, and 10 kD) and two bands of Bio-Rad’s ladder (75 kD and) are imprecise. Remarkably, there were no significant imprecise bands in  BMD prestained ladder (lane 6).

*Normally, prestained ladders usually have lot-to-lot variation. This evaluation only represented the tested lots. BMD prestained ladders have very small lot-to-lot varieties. 

As shown is a typical stability testing result. Dyes only slightly faded, and no protein degradation occurred even after one-month storage at 37 ˚C. BMD ladders can be stored at -20℃ for years and at -80℃ permanently.

  The images were derived from a single experiment. All bands except orange and magenta ones are well compatible with NIR fluorescent imaging system. 

Ladders No. (left to right): 

PM201, PM301, PM202, PM302, PM111, PM203, PM204 

  Three indicated prestainedladders (5 μl for each) were electrophoresed and transferred to a PVDF membrane. Pictures were taken after membrane transfer (0-hour washing), 3-hour washing, and overnight washing by TBS/T buffer. The picture of 0-hour washing (left panel) showed that BioRad's161-0375 was the least robust prestained ladder among the three competitors. After 3-hour washing, the band of 10 kD in Thermo’s #26619 and the bands of 10 kDand 25 kD in BioRad’s #161-0375 were barely visible (middle panel). After overnight washing, the band of 10 kD in Thermo’s #26619 and the bands of 70k, 25 kD, and 10 kD in BioRad’s #161-0375 completely disappeared (right panel). Remarkably, all bands of PM302 were still legible after the overnight washing process indicating the highest average membrane binding affinity among these three competitors.

Prestained protein’s migration during electrophoresis depends not only on the protein itself but also on the coupled dye. Therefore, Prestained ladders usually show different migration patterns in different electrophoresis systems. The MWs of BMD ladders were originally calibrated in Tris gel/Tris-Glycine   

buffer system (Table A). Migration shifts of these ladders in other electrophoresis systems were shown in Table B-D for rough references. We highly recommend specifically calibrating their MWs by unstained protein MW standard in any system other than Trisgel/Tris-Glycine buffer system.