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Encyclopedia > Melting temperature

The dissociation of a double-stranded DNA molecule is often referred to as melting because it occurs quickly once a certain temperature has been reached. For multiple copies of a specific DNA molecule (usually synthesized by polymerase chain reaction), the melting temperature (Tm) is defined as the temperature at which 50% of that same DNA molecule species form a stable double helix and the other 50% have been separated to single strand molecules. The melting temperature depends on both the length of the molecule, and the specific nucleotide sequence composition of that molecule. The Double-Helix are an alien race in the Wing Commander science fiction series. ... Polymerase chain reaction (PCR) is a molecular biology technique, invented in 1985 by Kary B. Mullis,[1] for enzymatically replicating DNA without using a living organism, such as E. coli or yeast. ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ...

Contents


Methods

Several formulas are used to calculate Tm values[1][2]. Some formulas are more accurate in predicting melting temperatures of DNA duplexes.[3]


Wallace method

The fastest and less accurate Wallace method is suitable for oligos less than 18mers in length by counting the frequency of each nucleotide base. Oligonucleotides are short sequences of nucleotides (RNA or DNA), typically with twenty or fewer base pairs. ...

Tm = 2(A + T) + 4(G + C)

The determination of Tm for DNA extracted from organisms was originally designed to determine the GC content of the DNA using the UV absorbance profile as a function of temperature [4][5][6].


References

  1. ^ Breslauer, K.J. et al. (1986) Proc. Natl. Acad. Sci. USA. 83, 3746-3750. (pdf)
  2. ^ Rychlik, W. et al. (1990) Nucleic Acids Res. 18, 6409-6412.
  3. ^ Owczarzy R., Vallone P.M., Gallo F.J., Paner T.M., Lane M.J. and Benight A.S. (1997) Predicting sequence-dependent melting stability of short duplex DNA oligomers. Biopolymers 44, 217-239. (pdf)
  4. ^ Mandel, M. and J. Marmur (1968) Methods in Enzymology 12 Nucleic Acids B, 195-206. For long chain DNA polymers CsCl density gradient analysis
  5. ^ Meselson, M. F. W. Stahl and J. Vinograd (1957) Proc. Natl. Acad. Sci. USA. 43, 581-588 yields values which correlate with the melting temperatures
  6. ^ Mandel, M. C., Schildkraut and J. Marmur (1968) Methods in Enzymology 12 Nucleic Acids B: 184-195. Where failures to correlate the buoyant density and the melting temperature arise (as in many bacteriophage DNAs) unusual bases have been found replacing all or part of one of the nucleotides in the genome.

See also

Irreversible egg protein denaturation and loss of solubility, caused by the high temperature (while cooking it) In biochemistry, denaturation is a structural change in biomolecules such as nucleic acids and proteins, such that they are no longer in their native state, and their shape which allows for optimal activity. ... Hybridisation is the process of combining complementary, single-stranded nucleic acids into a single molecule. ... Wikipedia does not yet have an article with this exact name. ... The melting point of a solid is the temperature at which it changes state from solid to liquid. ... A primer is a nucleic acid strand, or a related molecule that serves as a starting point for DNA replication. ...

External links


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Melting temperature - Wikipedia, the free encyclopedia (312 words)
The dissociation of a double-stranded DNA molecule is often referred to as melting because it occurs quickly once a certain temperature has been reached.
melting temperature depends on both the length of the molecule, and the specific nucleotide sequence composition of that molecule.
Where failures to correlate the buoyant density and the melting temperature arise (as in many bacteriophage DNAs) unusual bases have been found replacing all or part of one of the nucleotides in the genome.
  More results at FactBites »

 
 

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