b'Protein ladder considerationsTypically, protein ladders or standards are included during gel electrophoresis for protein molecular weight estimation (sizing) after separation (if not performing western blotting) or after the detection step (when performing western blotting). Protein ladders can also be used to monitorUse our interactive protein ladder selection tool to transfer efficiencies, although only qualitatively. In this use,find the most appropriate ladder for your application prestained ladders are the recommended choice (Table 9)and gel system. because they are visible on the membrane post-transfer. Special-purpose protein ladders designed specifically for western blots (Table 9) enable easy and convenient protein molecular weight estimation directly on western blots or indirectly by using various blotting detection systems (e.g., chemiluminescent, fluorescent, or chromogenic). The protein markers consist of recombinant proteins with an IgG binding site. These IgG binding sites bind the primary or secondary antibody used for detection of the target protein, allowing visualization of the standard on the western blot.Table 9. Protein ladder selection guide.MW range Product No. of proteins RangeLow PageRuler Unstained Low Range Protein Ladder 8 3.4100 kDaUnstained Broad PageRuler Unstained Protein Ladder 14 10200 kDaHigh HiMark Unstained Protein Standard 9 40500 kDaLow PageRuler Prestained Protein Ladder 10 10170 kDaPrestained Broad PageRuler Plus Prestained Protein Ladder 9 10250 kDaHigh HiMark Pre-stained Protein Standard9 30460 kDaLow Spectra Multicolor Low Range Protein Ladder 6 1.740 kDaMulticolorBroad Spectra Multicolor Broad Range Protein Ladder 10 10260 kDaprestainedHigh Spectra Multicolor High Range Protein Ladder 8 40300 kDaiBright Prestained Protein Ladder10 11-250 kDaWestern BroadMagicMark XP Protein Standard9 20220 kDaPageRuler Prestained NIR Protein Ladder 10 11250 kDaSpecialty Broad BenchMark Fluorescent Protein Standard7 11155 kDaIEF Marker 31013 pI 31021'