Isotopic Methylation
Isotopic Methylation - Related Videos
02:31
Elements: Chemical Symbols and Isotopes
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A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is used to indicate one atom of mercury (microscopic domain) or to label a container of many atoms of the element mercury (macroscopic domain). Some symbols are derived from the common English name of the element; others are abbreviations of the name in another language — Latin, Greek or German. For example, the symbol for aluminum (common name)...
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Methylation at CpG dinucleotides is a chemical modification of DNA hypothesized to play important roles in regulating gene expression. In particular, the methylation of clusters of methylation sites, called “CpG islands”, near promoters and other gene regulatory elements may contribute to the stable silencing of genes, for example, during epigenetic processes such as genomic imprinting and X-chromosome inactivation. At the same time, aberrant CpG methylation has been shown to be associated with...
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DNA Stable-Isotope Probing (DNA-SIP)
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DNA stable-isotope probing is a cultivation-independent method to identify and characterize active communities of microorganisms that are capable of utilizing specific substrates. Assimilation of substrate enriched in heavy isotope leads to incorporation of labelled atoms into microbial biomass. Density gradient ultracentrifugation retrieves labelled DNA for downstream molecular analyses.
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Methylated DNA Immunoprecipitation
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Isotopes
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Elements have a set number of protons that determines their atomic number (Z). For example, all atoms with eight protons are oxygen; however, the number of neutrons can vary for atoms of the same element. The sum of the number of protons and the number of neutrons is the mass number (A). Atoms with the same atomic number but different mass numbers are called isotopes. Elements can have multiple isotopes, for example, carbon-12, carbon-13, and carbon-14.An element's atomic mass, or weight, is a...
FAQs
The labeled methionine is converted into S-adenosylmethionine, or SAM, which supplies the labeled methyl group for transfer reactions. When a methyltransferase moves that group onto a biological molecule, the isotope becomes a measurable marker of the reaction. Tracking this sequence connects precursor use with methyl-group incorporation into the resulting product.
Methyltransferases control which biological molecules receive the labeled methyl group. Their activity can place the label on DNA, RNA, proteins, lipids, or small molecules, allowing researchers to examine enzyme specificity alongside methyl-transfer activity. Comparing labeled products therefore provides information about both the reaction and the molecular targets selected by the enzyme.
Isotope incorporation marks methyl groups formed during the experiment, whereas pre-existing methyl groups lack that newly introduced label. This distinction lets researchers assess newly formed modifications rather than measuring total methylation alone. The resulting measurements can clarify reaction rates, product formation, and changes in methyl-transfer activity within a biological system.
Stable and radioactive isotope labels provide two forms of traceable methyl groups, but the source material identifies different detection approaches for following them. Researchers can measure incorporation with mass spectrometry or nuclear magnetic resonance, while autoradiography is also available for radioactive labeling. The selected label and detection method determine how methylated products and reaction progress are monitored.
A typical workflow begins by supplying labeled methionine, followed by its conversion to labeled SAM. A methyltransferase then transfers the labeled group to its molecular target. Researchers analyze the resulting isotope incorporation using mass spectrometry, nuclear magnetic resonance, or autoradiography, depending on the label and experimental design. These measurements reveal products, rates, or pathway movement.
The approach is useful when researchers need to follow methyl-transfer activity across biological molecules or pathways. Applications include examining epigenetic regulation, enzyme specificity, cellular metabolism, and disease-associated changes in methylation. By identifying labeled products and measuring incorporation, experiments can connect methylation changes with particular reactions and help trace movement through metabolic pathways.