![Blotting Compass for Molecular Probes](https://upload.wikimedia.org/wikipedia/commons/3/33/Blotting_Compass_for_Molecular_Probes.png)
A blot, in
molecular biology
Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and physi ...
and
genetics
Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar wor ...
, is a method of transferring
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
s,
DNA or
RNA
Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
onto a carrier (for example, a
nitrocellulose
Nitrocellulose (also known as cellulose nitrate, flash paper, flash cotton, guncotton, pyroxylin and flash string, depending on form) is a highly flammable compound formed by nitrating cellulose through exposure to a mixture of nitric acid and ...
,
polyvinylidene fluoride
Polyvinylidene fluoride or polyvinylidene difluoride (PVDF) is a highly non-reactive thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride.
PVDF is a specialty plastic used in applications requiring the highest pur ...
or
nylon
Nylon is a generic designation for a family of synthetic polymers composed of polyamides ( repeating units linked by amide links).The polyamides may be aliphatic or semi-aromatic.
Nylon is a silk-like thermoplastic, generally made from petro ...
membrane). In many instances, this is done after a
gel electrophoresis
Gel electrophoresis is a method for separation and analysis of biomacromolecules ( DNA, RNA, proteins, etc.) and their fragments, based on their size and charge. It is used in clinical chemistry to separate proteins by charge or size (IEF ...
, transferring the molecules from the gel onto the
blotting membrane, and other times adding the samples directly onto the membrane. After the blotting, the transferred proteins, DNA or RNA are then visualized by colorant staining (for example, silver staining of proteins),
autoradiograph
An autoradiograph is an image on an X-ray film or nuclear emulsion produced by the pattern of decay emissions (e.g., beta particles or gamma rays) from a distribution of a radioactive substance. Alternatively, the autoradiograph is also available ...
ic visualization of
radiolabelled
Isotopic labeling (or isotopic labelling) is a technique used to track the passage of an isotope (an atom with a detectable variation in neutron count) through a reaction, metabolic pathway, or cell. The reactant is 'labeled' by replacing specific ...
molecules (performed before the blot), or specific labelling of some proteins or
nucleic acid
Nucleic acids are biopolymers, macromolecules, essential to all known forms of life. They are composed of nucleotides, which are the monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main cl ...
s. The latter is done with
antibodies
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
or
hybridization probe
In molecular biology, a hybridization probe (HP) is a fragment of DNA or RNA of usually 15–10000 nucleotide long which can be radioactively or fluorescently labeled. HP can be used to detect the presence of nucleotide sequences in analyzed RN ...
s that bind only to some molecules of the blot and have an
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
joined to them. After proper washing, this enzymatic activity (and so, the molecules we search in the blot) is visualized by incubation with proper reactive, rendering either a colored deposit on the blot or a
chemiluminescent
Chemiluminescence (also chemoluminescence) is the emission of light (luminescence) as the result of a chemical reaction. There may also be limited emission of heat. Given reactants A and B, with an excited intermediate ◊,
: + -> lozenge - ...
reaction which is registered by photographic
film
A film also called a movie, motion picture, moving picture, picture, photoplay or (slang) flick is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, feelings, beauty, or atmosphere ...
.
Southern blot
A
Southern blot
A Southern blot is a method used in molecular biology for detection of a specific DNA sequence in DNA samples. Southern blotting combines transfer of electrophoresis-separated DNA fragments to a filter membrane and subsequent fragment detecti ...
is a method routinely used in molecular biology for detection of a specific
DNA sequence in DNA samples. Southern blotting combines transfer of electrophoresis-separated DNA fragments to a filter membrane and subsequent fragment detection by probe hybridization.
Western blot
A
western blot
The western blot (sometimes called the protein immunoblot), or western blotting, is a widely used analytical technique in molecular biology and immunogenetics to detect specific proteins in a sample of tissue homogenate or extract. Besides detect ...
is used for the detection of specific proteins in complex samples. Proteins are first separated by size using electrophoresis before being transferred to an appropriate
blotting matrix A blotting matrix, in molecular biology and genetics, is the substrate onto which macromolecules, such as proteins, are transferred in a blot method. The matrices are generally chemically modified paper filters or microporous membrane filters. In a ...
(usually
polyvinylidene fluoride
Polyvinylidene fluoride or polyvinylidene difluoride (PVDF) is a highly non-reactive thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride.
PVDF is a specialty plastic used in applications requiring the highest pur ...
or
nitrocellulose
Nitrocellulose (also known as cellulose nitrate, flash paper, flash cotton, guncotton, pyroxylin and flash string, depending on form) is a highly flammable compound formed by nitrating cellulose through exposure to a mixture of nitric acid and ...
) and subsequent detection with antibodies.
Far-western blot
Similar to a
western blot
The western blot (sometimes called the protein immunoblot), or western blotting, is a widely used analytical technique in molecular biology and immunogenetics to detect specific proteins in a sample of tissue homogenate or extract. Besides detect ...
, the
far-western blot
The far-western blot, or far-western blotting, is a molecular biological method based on the technique of western blot to detect protein-protein interaction ''in vitro''. Whereas western blot uses an antibody probe to detect a protein of interest, ...
uses
protein–protein interaction
Protein–protein interactions (PPIs) are physical contacts of high specificity established between two or more protein molecules as a result of biochemical events steered by interactions that include electrostatic forces, hydrogen bonding and th ...
s to detect the presence of a specific protein immobilized on a blotting matrix. Antibodies are then used to detect the presence of the protein–protein complex, making the Far-Western blot a specific case of the Western blot.
Southwestern blot
A
southwestern blot
The southwestern blot, is a lab technique that involves identifying as well as characterizing DNA-binding proteins by their ability to bind to specific oligonucleotide probes. Determination of molecular weight of proteins binding to DNA is also ...
is based on
Southern blot
A Southern blot is a method used in molecular biology for detection of a specific DNA sequence in DNA samples. Southern blotting combines transfer of electrophoresis-separated DNA fragments to a filter membrane and subsequent fragment detecti ...
and is used to identify and characterize DNA-binding proteins by their ability to bind to specific oligonucleotide probes.
The proteins are separated by gel electrophoresis and are subsequently transferred to nitrocellulose membranes similar to other types of blotting.
Eastern blot
The
eastern blot
The eastern blot, or eastern blotting, is a biochemical technique used to analyze protein post-translational modifications including the addition of lipids, phosphates, and glycoconjugates. It is most often used to detect carbohydrate epitopes. Thu ...
is used for the detection of specific posttranslational modifications of proteins. Proteins are separated by gel electrophoresis before being transferred to a blotting matrix whereupon posttranslational modifications are detected by specific substrates (cholera toxin, concanavalin, phosphomolybdate, etc.) or antibodies.
Far-eastern blot
The
far-eastern blot The far-eastern blot, or far-eastern blotting, is a technique for the analysis of lipids separated by high-performance thin layer chromatography ( HPTLC). When executing the technique, lipids are transferred from HPTLC plates to a PVDF membrane for ...
is for the detection of lipid-linked
oligosaccharide
An oligosaccharide (/ˌɑlɪgoʊˈsækəˌɹaɪd/; from the Greek ὀλίγος ''olígos'', "a few", and σάκχαρ ''sácchar'', "sugar") is a saccharide polymer containing a small number (typically two to ten) of monosaccharides (simple sugar ...
s.
High-performance thin-layer chromatography
High-performance thin-layer chromatography (HPTLC) is an enhanced form of thin-layer chromatography (TLC). A number of enhancements can be made to the basic method of thin-layer chromatography to automate the different steps, to increase the r ...
is first used to separate the lipids by physical and chemical characteristics, then transferred to a blotting matrix before the oligosaccharides are detected by a specific binding protein (i.e. antibodies or lectins).
Northern blot
The
northern blot
The northern blot, or RNA blot,Gilbert, S. F. (2000) Developmental Biology, 6th Ed. Sunderland MA, Sinauer Associates. is a technique used in molecular biology research to study gene expression by detection of RNA (or isolated mRNA) in a sample.K ...
is for the detection of specific RNA sequences in complex samples. Northern blotting first separates samples by size via gel electrophoresis before they are transferred to a blotting matrix and detected with labeled RNA probes.
Reverse northern blot
The
reverse northern blot The reverse northern blot is a method by which gene expression patterns may be analyzed by comparing isolated RNA molecules from a tester sample to samples in a control cDNA library. It is a variant of the northern blot in which the nucleic acid imm ...
differs from both northern and Southern blot in that DNA is first immobilized on a blotting matrix and specific sequences are detected with labeled RNA probes.
Dot blot
A
dot blot
A dot blot (or slot blot) is a technique in molecular biology used to detect proteins. It represents a simplification of the western blot method, with the exception that the proteins to be detected are not first separated by electrophoresis. Inste ...
is a special case of any of the above blots where the analyte is added directly to the blotting matrix (and appears as a "dot") as opposed to separating the sample by electrophoresis prior to blotting.
List of blots
*
Southern blot
A Southern blot is a method used in molecular biology for detection of a specific DNA sequence in DNA samples. Southern blotting combines transfer of electrophoresis-separated DNA fragments to a filter membrane and subsequent fragment detecti ...
for DNA
*
northern blot
The northern blot, or RNA blot,Gilbert, S. F. (2000) Developmental Biology, 6th Ed. Sunderland MA, Sinauer Associates. is a technique used in molecular biology research to study gene expression by detection of RNA (or isolated mRNA) in a sample.K ...
for RNA
*
reverse northern blot The reverse northern blot is a method by which gene expression patterns may be analyzed by comparing isolated RNA molecules from a tester sample to samples in a control cDNA library. It is a variant of the northern blot in which the nucleic acid imm ...
for RNA
*
western blot
The western blot (sometimes called the protein immunoblot), or western blotting, is a widely used analytical technique in molecular biology and immunogenetics to detect specific proteins in a sample of tissue homogenate or extract. Besides detect ...
for proteins
*
far-western blot
The far-western blot, or far-western blotting, is a molecular biological method based on the technique of western blot to detect protein-protein interaction ''in vitro''. Whereas western blot uses an antibody probe to detect a protein of interest, ...
for
protein–protein interaction
Protein–protein interactions (PPIs) are physical contacts of high specificity established between two or more protein molecules as a result of biochemical events steered by interactions that include electrostatic forces, hydrogen bonding and th ...
s
*
eastern blot
The eastern blot, or eastern blotting, is a biochemical technique used to analyze protein post-translational modifications including the addition of lipids, phosphates, and glycoconjugates. It is most often used to detect carbohydrate epitopes. Thu ...
for
post-translational modification
Post-translational modification (PTM) is the covalent and generally enzymatic modification of proteins following protein biosynthesis. This process occurs in the endoplasmic reticulum and the golgi apparatus. Proteins are synthesized by ribosome ...
*
far-eastern blot The far-eastern blot, or far-eastern blotting, is a technique for the analysis of lipids separated by high-performance thin layer chromatography ( HPTLC). When executing the technique, lipids are transferred from HPTLC plates to a PVDF membrane for ...
for
glycolipid
Glycolipids are lipids with a carbohydrate attached by a glycosidic (covalent) bond. Their role is to maintain the stability of the cell membrane and to facilitate cellular recognition, which is crucial to the immune response and in the connec ...
s
*
dot blot
A dot blot (or slot blot) is a technique in molecular biology used to detect proteins. It represents a simplification of the western blot method, with the exception that the proteins to be detected are not first separated by electrophoresis. Inste ...
See also
*
Immunoscreening Immunoscreening is a method of biotechnology used to detect a polypeptide produced from a cloned gene. The term encompasses several different techniques designed for protein identification, such as Western blotting, using recombinant DNA, and analyz ...
References
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Molecular biology
Laboratory techniques