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The hyperchromic effect is the striking increase in absorbance of DNA upon denaturation. The two strands of DNA are bound together mainly by the stacking interactions, hydrogen bonds and hydrophobic effect between the complementary bases. The hydrogen bond limits the resonance of the aromatic ring so the absorbance of the sample is limited as well.
In biochemistry, denaturation is a process in which proteins or nucleic acids lose folded structure present in their native state due to various factors, including application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent (e.g., alcohol or chloroform), agitation and radiation, or heat. [3]
Likewise, increasing salt concentrations helps diffuse negative repulsions between the phosphates in the DNA's backbone. This also leads to a rise in the DNA's melting temperature. Conversely, pH can have a negative effect on DNA's stability which may lead to a lowering of its melting temperature.
Nucleic acid thermodynamics is the study of how temperature affects the nucleic acid structure of double-stranded DNA (dsDNA). The melting temperature (T m) is defined as the temperature at which half of the DNA strands are in the random coil or single-stranded (ssDNA) state. T m depends on the length of the DNA molecule and its specific ...
The highest DNA adsorption efficiencies occur in the presence of buffer solution with a pH at or below the pKa of the surface silanol groups. The mechanism behind DNA adsorption onto silica is not fully understood; one possible explanation involves reduction of the silica surface's negative charge due to the high ionic strength of the buffer.
In the less extensive technique of equilibrium unfolding, the fractions of folded and unfolded molecules (denoted as and , respectively) are measured as the solution conditions are gradually changed from those favoring the native state to those favoring the unfolded state, e.g., by adding a denaturant such as guanidinium hydrochloride or urea.
Denaturation Mapping is a form of optical mapping, first described in 1966. It is used to characterize DNA molecules without the need for amplification or sequencing . It is based on the differences between the melting temperatures of AT-rich and GC-rich regions. [ 1 ]
Most solutions also have an antioxidant, as oxidized phenol damages the nucleic acids. For RNA purification, the pH is kept at around 4, which retains RNA in the aqueous phase preferentially. For DNA purification, the pH is usually near 7, at which point all nucleic acids are found in the aqueous phase.