Melting temperature, of DNA

Note 1. Rojphsic is calculated by assuming spherical molecule according to Roipkre = (3/5) (3Mv/4itNA)  

fffo values have been corrected for the hydration, (1 + where is the volume of water of hydration per unit volume of anhydrous macromolecules. 

From Ro.apt G.gphere soidf/f values Lysozyme, catalase and myoglobin are not strictly spherical but their overall shape is not far from spherical, whereas myosin, DNA and TMV are nonspherical. 

DNA molecule is linearly related to its %G + C (Marmur and Doty, 1962) by = 69.3 + 0.41 (%G + C) at 0.2 M Na . Knowledge of is essential in various aspects of DNA function and analyses. Predicted Tm for any oligonucleotides can be obtained from www.genseloligos.com/Calculation/calculation.html. 

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Not only the melting temperature of DNA but also its density in solution is dependent on relative G C content. G C-rich DNA has a significantly higher density than A T-rich DNA. Furthermore, a linear relationship exists between the buoyant densities of DNA from different sources and their G C content... 

Inclusion of formamide is essential for lowering the melting temperature of DNA. It is necessary to perform denaturation and hybridization of probe and chromosomal DNA at a lower temperature to ensure preservation of chromosomal architecture. Similarly, inclusion of formamide in the stringency washes increases the stringency without having to increase the temperature... 

Schildkraut, C. (1965) Dependence of the melting temperature of DNA on salt concentration. Biopolymers, 3, 195-208. 

Finally, the use of oligonucleotides as substrates may provide a mechanism for preferentially replicating RNA templates. The oligomers in a prebiotic mix that contained a larger proportion or ribose residues should have annealed more readily to an RNA template than those oligonucleotides that contained fewer ribose-linked bases. Duplexes formed solely from RNA are more stable than duplexes in which one of the strands contains even only a minor chemical modification, namely, ribose to deoxyribose.65 In addition, acyclic residues are found to decrease significantly the melting temperature of DNA duplexes in which they are included.66... 

Fig. 1.6 Examples of alkaloids that intercalate DNA. Intercalation increases the melting temperature of DNA relevant values are shown in parentheses.

Inclusion of formamide in the HM mix and posthybridization washes lowers the melting temperature of DNA. Denaturation, hybridization, and stringency washes in formamide, therefore, helps preserve the architecture of the chromosomes, by lowering the denaturation and stringency washing temperature. 

Using the melting behaviour of DNA-antibiotic complexes as a criterion of binding a drastic increase in the melting temperature of DNA was observed in the... 

Heat causes the DNA strands to separate (denature). The melting temperature of DNA Increases with the percentage of G C base pairs. Under suitable conditions, separated complementary nucleic acid strands will renature. 

The melting temperature of DNA is related to the base composition, particularly the G-C/A-T pair ratio. The G-C pairs are held together by three hydrogen bonds whereas the A-T pairs are held by only two such bonds, and a greater proportion of the more strongly bound G-C pairs, if present, leads to a higher value of and an increase in density which is normally -1.7 g/cm (Figure 10.47). 

Melting temperature of DNA. Conformationeil change of DNA was monitored by optical absorption at 260 nm as a function of temperature... 

Fig. 3.17 Data for Example 3.1 showing the variation of the melting temperature of DNA molecules with the fraction of C-G base pairs. All the samples also contain 1.0 X 10 mol dm ...

Short-chain alcohols showed the same behavior. The melting temperature of DNA decreases in water/methanol solutions [65]. Furthermore, the midpoint of the solvent denaturation decreased in the order methanol, ethanol and propanol that is, the secondary structure stability was lowered as the length of the aliphatic chain was increased [65]. Following the same line, in another contribution it was realized that an increase in the number or size of alkyl substituents on amides, ureas, carbamates and alcohols increased the denaturating effectiveness towards DNA [61]. The contribution of non-specific hydrophobic interactions to DNA denaturation was then brought up, and in fact it is not surprising that these small hydrophobic molecules... 

The fact that the melting temperature of DNA depends on its base sequence is a good indication of the importance of the nearest neighbors for the stability of the helix [74], and it is normally attributed to the stacking interactions between adjacent bases. 

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