The traditional method to visualize protein ladders on Western blots is to use prestained protein ladders which remain visible when transferred to the blotted membrane. Other home-made protein ladders have tackled the problem of detecting protein ladders on Western blots. Doucet and Beauregard produced a protein ladder by disulfide crosslinking a 11 kD designer protein via oxidation in solution 1. There are a few reported examples of home-made protein ladders. These improvements have come at an increased expense with most commercially available unstained ladders costing about US$ 1.00 per lane. 25, 50 kD) and with optional features such as prestaining with dyes for visibility during electrophoresis and on Western blots. Such ladders have been replaced more recently by recombinant ladders with rounded molecular weights (e.g. ![]() These native protein ladders were commercially available and relatively inexpensive at about US$ 0.10 per lane. As such, protein ladders constitute critical reference reagents when expressing, purifying or analyzing proteins.Įarly protein ladders were comprised of readily available proteins such as lysozyme (14 kD), soybean trypsin inhibitor (21 kD), carbonic anhydrase (31 kD), ovalbumin (45 kD), serum albumin (67 kD) and phosphorylase b (97 kD). They provide molecular weight standards to estimate the size of proteins separated by gel electrophoresis like SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis). Protein ladders or molecular weight markers are among the most commonly used reagents in biochemistry experiments. coli and affinity protein purification, and to research laboratories desiring positive controls for recombinant protein expression and purification. These Penn State Protein Ladder expression plasmids also constitute useful reagents for teaching laboratories to demonstrate recombinant expression in E. 50 ml of culture is sufficient to produce 20,000 lanes of individual ladder protein or 3750 lanes of each set of coexpressed ladder proteins. For more efficient production, we have created two polycistronic expression vectors which coexpress the 10, 30, 50, 100 kD proteins or the 20, 40, 60, 80 kD proteins. We have also constructed plasmids to express 150 and 250 kD proteins. Each protein migrates appropriately on SDS-PAGE gels, is expressed at very high levels (10–50 mg per liter of culture), is easy to purify via histidine tags and can be detected directly on Western blots via engineered immunoglobulin binding domains. The system includes plasmids which express 10, 15, 20, 30, 40, 50, 60, 80 and 100 kD proteins in E. Compatible with chemiluminescent substrates and fluorescent secondary antibodies (not recommended for antibodies labeled with fluors in the 500–550 nm channel).We have created the Penn State Protein Ladder system to produce protein molecular weight markers easily and inexpensively (less than a penny a lane). Western blotting: detection of the nine unstained bands via the detection method used for the target protein.The protein standard is supplied in a ready-to-use format for direct loading onto gels no need to heat, reduce, or add sample buffer prior to use.Ĭompare and view all other protein standards and ladders › The MagicMark XP Standard is compatible with most western kits and substrates (chemiluminescent, chromogenic, and fluorescent). ![]() The IgG binding site binds the primary or secondary antibody used for detection of the target protein, allowing direct visualization of the standard on the western blot. MagicMark XP Western Protein Standard consists of nine recombinant proteins (20–220 kDa), each of which contains an IgG binding site.
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