Different blotting methods are offered to identify distinctive proteins and also nucleic mountain sequences. Southern, northern, and western blot protocols room similar, and also begin with electrophoretic separation that protein and also nucleic acid fragments on a gel, which room then moved to a membrane (nitrocellulose membrane, polyvinylidene difluoride (PVDF) membrane, etc.) wherein they space immobilized. This permits radiolabeled or enzymatically labeled antibody or DNA probes to tie the immobilized target, and the molecules of interest may then be visualized with various methods. Blotting methods are selected based upon the target molecule: DNA, RNA, or protein. (Figure 1, Table 1).

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Southern Blot

Southern blots are provided to determine the identity, size, and abundance of specific DNA sequences. The southern blot protocol begins with DNA extraction from the cell or tissues, which is then enzymatically spend to develop DNA fragments. The fragments are separated by dimension on one agarose or polyacrylamide gel via electrophoresis. Smaller pieces will migrate farther ~ above the gelatin than larger ones. Following electrophoresis, the DNA ~ above the gelatin is moved to a nylon membrane. The membrane is incubated through a nucleic acid probe that has a succession homologous to the target sequence and also is labeled v radioactivity, fluorescent dye, or an enzyme capable of generating a chemiluminescent signal. Hybridization of complementary sequences occurs throughout incubation, and the unhybridized probe is eliminated by washing with buffer. The totally hybridized labeling probe molecules will remain bound come the blot. Detection techniques differ based upon the probe label; radiolabeled probes are visualized through X-ray movie or phosphorimaging, and also enzymatically labeled probes are visualized through chemiluminescent substrate.

Southern blot protocol

DNA isolationRestriction digestion: digest the DNA with a border enzyme, and also if necessary, concentrate digested DNA.Gel electrophoresis: prepare an agarose gel and either TAE or TBE buffer (buffer selection will count on the duration of the run and also the size of the DNA fragments). Load samples into wells and include a DNA molecular load marker. Operation the gel.Transfer:Place the gel in a container v denaturing solution, and also wash twice for 15 minutes on a shaker.Rinse with water, then wash with neutralization solution.During the ahead step, begin to prepare Whatman document and nylon membrane for the transfer.Assemble the deliver apparatus v the membrane, Whatman paper, and also gel and also transfer in SSC or SSPE buffer.When transfer is complete, cross-link DNA in a cross-linker, climate rinse the membrane.Pre-hybridization (blocking):Blocking to reduce non-specific binding come the membrane. Prepare the pre-hybridization equipment and include sample DNA. Remove the blot indigenous the cross-linker, add the pre-hybridization solution and incubate.Hybridization:Prepare the probe mixture (a complementary DNA strand) and buffer.Remove the pre-hybridization solution and incubate the blot through the probe (incubation times will certainly vary depending on the application).Following incubation, execute a low-stringency wash adhered to by a high-stringency to wash to refine the DNA.Probe detection:Rinse the membrane, carry to a container with blocking solution and incubate.Discard prevent solution, replace with antibody solution and also incubate.Discard antibody solution, to wash the membrane.Follow manufacturer directions for chemiluminescent detection.

Northern Blot

Northern blots are provided to recognize the identity, size, and also abundance of particular RNA sequences. Northern blot protocols start with RNA isolation, and separation methods vary relying on RNA size. Huge RNAs space separated through electrophoresis ~ above a formaldehyde agarose gelatin or glyoxal agarose gel, which prevents normal base paring and maintains RNA in a denatured state. Little RNAs space separated ~ above a denaturing (urea) polyacrylamide gel. The RNA is then transferred from the gelatin to a nylon membrane i beg your pardon is climate incubated through a radioactively or nonisotopically labeled RNA, DNA, or oligodeoxynucleotide probe. The unhybridized probe is eliminated by washing v buffer. Radiolabeled probes space visualized v X-ray film, and also enzymatically labeling probes room visualized with chemiluminescence.

Northern blot protocol

RNA isolationElectrophoresis:For a formaldehyde agarose gel: prepare the gel and also insert the gelatin tray into the apparatus. Fill with MOPS buffer, fill the samples and also include a molecular weight marker. Operation the gel, climate trim the gel before blotting.For a glyoxal agarose gel: prepare the gel and also insert the gel tray right into the apparatus. Fill through MOPS buffer, prepare samples and also load into wells together with RNA ladder.For a denaturing polyacrylamide gel: actors the gel, and mount that in the electrophoresis unit. Prepare samples, load into the gel, and run v TBE running buffer.Transfer:For a formaldehyde agarose gel or glyoxal agarose gel: wash the gel in SSC, climate assemble the move unit with the gel, filter paper, and also nylon membrane. Once transfer is complete, location the membrane in a UV cross-linker.For a denaturing polyacrylamide gel: assemble the move unit including gel, filter paper, and nylon membrane ensuring they room flooded v TBE. Once transfer is complete, location the membrane in a UV cross-linker to settle the RNA come the membrane.Pre-hybridization (blocking):Pre-hybridize the membrane in hybridization solution.Hybridization:Add probe come the hybridization solution and incubate.Wash the membrane in low-stringency washes to remove hybridization solution and unhybridized probe, and also high-stringency washes come remove partially hybridized molecules.Follow manufacturer directions for chemiluminescent detection.

Western Blot


Western blots are supplied to identify the identity, size, and also abundance of specific proteins within a sample. The western blot protocol starts with sample lysate ready from tissue or cell society and separation top top a polyacrylamide gelatin via electrophoresis. The be separate proteins are then transferred to a nitrocellulose or polyvinylidene difluoride (PVDF) membrane. The membrane is incubated through a blocking certified dealer to stop nonspecific binding, adhered to by incubation through a primary antibody to bind the protein of interest. There are two detection methods, direct and indirect. Direct detection (Figure 2) counts on a labeled major antibody, whereas indirect detection needs a primary antibody directed against the target protein, and also a secondary antibody directed versus the immunoglobin course or subclass that the main antibody’s species (Figure 3). Image methods encompass colorimetric assays in i beg your pardon a fancy precipitate is produced, chemiluminescence, and also fluorescence.

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Western blot protocol

Prepare lysate native cell society or tissue.Sample preparation:Determine the protein concentration of each sample through a protein quantification assay (ie. Bradford assay).Add an equal volume of 2X Laemmli sample buffer to each sample.Some samples may need come be reduced or denatured, this is achieved by boil samples in buffer.Electrophoresis:Prepare one SDS-PAGE gel, load samples together with molecular weight marker.Run the gelatin in running buffer.Transfer:Following electrophoresis, rally the deliver unit consisting of the gel, PVDF or nitrocellulose membrane, and also filter paper.Transfer the proteins to the membrane v transfer buffer.Antibody Staining (indirect detection):Prepare prevent buffer and also incubate the membrane to reduce non-specific binding.Incubate the membrane with major antibody diluted in blocking buffer.Wash the membrane in TBST, and incubate through conjugated second antibody diluted in impede buffer.Wash the membrane in TBST.Follow manufacturer directions because that chemiluminescent detection.