Tandem mass tags
Encyclopedia
Tandem mass tags are chemical labels used for mass spectrometry
(MS)-based quantification and identification of biological macromolecule
s such as protein
s, peptides and nucleic acids. TMT belongs to a family of reagents referred to as isobaric mass tags
. They provide an alternative to gel- or antibody
-based quantification but may also be used in combination with these and other methods.
The tags contain four regions, namely a mass reporter region (M), a cleavable linker region (F), a mass normalization region (N) and a protein reactive group (R). The chemical structures of all the tags are identical but each contains isotopes substituted at various positions, such that the mass reporter and mass normalization regions have different molecular mass
es in each tag. The combined M-F-N-R regions of the tags have the same total molecular weights and structure so that during chromatographic
or electrophoretic
separation and in single MS mode, molecules labelled with different tags are indistinguishable. Upon fragmentation in MS/MS mode, sequence information is obtained from fragmentation of the peptide back bone
and quantification data are simultaneously obtained from fragmentation of the tags, giving rise to mass reporter ions.
Proteome Sciences Plc have the patents for TMT technology. These patents have broad coverage of all tandem mass tag technology.
of TMT tags are publicly available through the unimod database at unimod.org and hence, mass spectrometry software
such as Mascot
are able to account for the tag masses. Additionally, as of version 2.2, Mascot
has the capability to quantify using TMT and other isobaric mass tags without the use of additional software.
Mass spectrometry
Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of charged particles.It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical structures of molecules, such as peptides and...
(MS)-based quantification and identification of biological macromolecule
Macromolecule
A macromolecule is a very large molecule commonly created by some form of polymerization. In biochemistry, the term is applied to the four conventional biopolymers , as well as non-polymeric molecules with large molecular mass such as macrocycles...
s such as protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s, peptides and nucleic acids. TMT belongs to a family of reagents referred to as isobaric mass tags
Isobaric labeling
Isobaric labeling is a mass spectrometry strategy used in quantitative proteomics. Peptides or proteins are labeled with various chemical groups that are isobaric, or the same in mass, but which fragment during tandem mass spectrometry to yield reporter ions of different mass...
. They provide an alternative to gel- or antibody
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
-based quantification but may also be used in combination with these and other methods.
Versions
There are currently three varieties of TMT available:- TMTzero – a non-isotopically substituted core structure
- TMTduplex – an isobaric pair of mass tags with a single isotopic substitution
- TMTsixplex – an isobaric set of six mass tags with five isotopic substitutions
The tags contain four regions, namely a mass reporter region (M), a cleavable linker region (F), a mass normalization region (N) and a protein reactive group (R). The chemical structures of all the tags are identical but each contains isotopes substituted at various positions, such that the mass reporter and mass normalization regions have different molecular mass
Molecular mass
The molecular mass of a substance is the mass of one molecule of that substance, in unified atomic mass unit u...
es in each tag. The combined M-F-N-R regions of the tags have the same total molecular weights and structure so that during chromatographic
Chromatography
Chromatography is the collective term for a set of laboratory techniques for the separation of mixtures....
or electrophoretic
Gel electrophoresis
Gel electrophoresis is a method used in clinical chemistry to separate proteins by charge and or size and in biochemistry and molecular biology to separate a mixed population of DNA and RNA fragments by length, to estimate the size of DNA and RNA fragments or to separate proteins by charge...
separation and in single MS mode, molecules labelled with different tags are indistinguishable. Upon fragmentation in MS/MS mode, sequence information is obtained from fragmentation of the peptide back bone
Peptide bond
This article is about the peptide link found within biological molecules, such as proteins. A similar article for synthetic molecules is being created...
and quantification data are simultaneously obtained from fragmentation of the tags, giving rise to mass reporter ions.
Proteome Sciences Plc have the patents for TMT technology. These patents have broad coverage of all tandem mass tag technology.
Identification and quantification of TMT-labeled peptides
The structuresChemical structure
A chemical structure includes molecular geometry, electronic structure and crystal structure of molecules. Molecular geometry refers to the spatial arrangement of atoms in a molecule and the chemical bonds that hold the atoms together. Molecular geometry can range from the very simple, such as...
of TMT tags are publicly available through the unimod database at unimod.org and hence, mass spectrometry software
Mass spectrometry software
Mass spectrometry software is software used for data acquisition, analysis, or representation in mass spectrometry.- MS/MS peptide identification :...
such as Mascot
Mascot (software)
Mascot is a software search engine that uses mass spectrometry data to identify proteins from primary sequence databases.Many research facilities utilize Mascot, either by private or public server for database searching....
are able to account for the tag masses. Additionally, as of version 2.2, Mascot
Mascot (software)
Mascot is a software search engine that uses mass spectrometry data to identify proteins from primary sequence databases.Many research facilities utilize Mascot, either by private or public server for database searching....
has the capability to quantify using TMT and other isobaric mass tags without the use of additional software.
See also
- Protein mass spectrometryProtein mass spectrometryProtein mass spectrometry refers to the application of mass spectrometry to the study of proteins. Mass spectrometry is an important emerging method for the characterization of proteins. The two primary methods for ionization of whole proteins are electrospray ionization and matrix-assisted laser...
- Quantitative proteomicsQuantitative proteomicsThe aim of quantitative proteomics is to obtain quantitative information about all proteins in a sample. Rather than just providing lists of proteins identified in a certain sample, quantitative proteomics yields information about differences between samples. For example, this approach can be used...
- ICATIsotope-coded affinity tagIsotope-coded affinity tags are a gel-free method for quantitative proteomics that relies on chemical labeling reagents. These chemical probes consist of three general elements: a reactive group capable of labeling a defined amino acid side chain , an isotopically coded linker, and a tag for the...
- iTRAQITRAQIsobaric tags for relative and absolute quantitation are a non-gel-based technique used to quantify proteins from different sources in a single experiment. It uses isotope-coded covalent tags...
- Label-free quantitation
- SILACSilacSILAC is a technique based on mass spectrometry that detects differences in protein abundance among samples using non-radioactive isotopic labeling. It is a popular method for quantitative proteomics.-Procedure:Two populations of cells are cultivated in cell culture...
- ICAT