Such high-quality lab-grade reagents coupled with high-tech equipment make lab life easier by avoiding multiple repetitions and saving time and money. These are extensively used in gel electrophoresis and western blot assays to monitor protein movement and quantify bands. Some of the most common and widely used include prestained, unstained, western blot, and fluorescent protein ladders. Protein ladders are available in different types. They move in the gel matrix based on their sizes (from largest protein to smallest protein), in the direction of negative to the positive electrode. Protein ladders are a mixture of proteins that act as points of reference during protein gel electrophoresis. *Note: It’s always recommended to refer to a manufacturer’s or company’s datasheet to learn more about the research uses or any detailed information on the commercially available protein ladders.įigure: An image showing gels and blots with fluorescent protein ladders. This makes it easier for researchers to visualize and quantify the protein bands. The light intensity of bands observed using fluorescent protein ladders is proportional to the concentration of proteins, i.e., the more the concentration of protein, the more light intensity of the bands. These ladders are popular among researchers because they only have a slight background interference, sensitivity, and an optimal linear dynamic range. The bands fluoresce when the light of a specific wavelength falls on them. They contain a mixture of proteins that are pre-stained with fluorescent dyes. Fluorescent Protein Laddersįluorescent protein ladders are used in SDS-PAGE gels or polyacrylamide gel electrophoresis (involving tris-glycine buffer). Unstained protein ladders allow the accurate estimation of proteins because, unlike prestained protein ladders, their movement in the gel matrix is not hindered by the binding of dyes.įigure: Visualization of western blots using different techniques after the complete transfer of western blot protein ladders on the membrane. On the membrane blot, they are visualized using Ponceau S or any other similar stains. The bands in the gel are most commonly visualized using Coomassie Brilliant Blue R-250 stains. They allow the formation of identifiable sharp bands in gels, leading to the accurate estimation of molecular weights of proteins Unstained protein ladders are a mixture of easy-to-purify proteins that are not stained with any color stains. Calculating the apparent molecular weight of proteins from the image of the membrane blot with a ladder by comparing it to the image obtained after staining proteins with antibodies.Western blot transfers to test the transfer efficiency of proteins on PVDF, nylon, or nitrocellulose membranes from protein gels. ![]() SDS-Polyacrylamide gel electrophoresis (or SDS-PAGE) to monitor protein separation.Prestained protein ladders have applications in: The storage buffer used for these ladders consists of a mixture of reagents like Tris citrate/phosphate, urea, sodium lauryl sulfate, DTT, EDTA, and 15% glycerol in different concentrations.įigure: An image of pre-stained protein ladders with different colors. They are supplied in a loading buffer for their direct loading in gel lanes. Most commercial prestained protein ladders are available as three-color protein standards with 10-12 prestained proteins. They are engineered so that they produce sharp, evenly-spaced proteins prestained with different colors, making it easier and simpler to estimate the approximate molecular weight of proteins. Prestained recombinant protein ladders: These are highly preferred ladders for research use.Researchers typically do not prefer these because they tend to produce indistinct broad bands. Prestained naturally-occurring protein ladders: These produce broad bands when stained with one or more colors and show variability in the amount and location of dyes binding to each protein.Prestained protein ladders typically come in two types: These bands make it easier to monitor the protein migration patterns and calculate the molecular weights of proteins. Prestained protein ladders have three highly-intensified colored reference bands of 25 kDa, 50 kDa, and 75 kDa (kilodaltons). They can have either all proteins prestained with one color, two or more proteins prestained in different colors, or all proteins prestained with different colors. Prestained protein ladders, as the name suggests, have protein mixtures prestained with colors. Common Types of Protein Ladder Prestained Protein Ladders Figure: A picture of protein electrophoresis with protein ladders in the first column of the immunoblot.
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