What Is a Nucleic Acid?

Nucleic acid is a class of biopolymers and is an essential constituent of all known life forms.

Nucleic acids are made up of many

Nucleic acid denaturation

Under the action of certain physical and chemical factors, the phenomenon that the hydrogen bond between bases in a space structure such as a double helix of a nucleic acid is broken and becomes a single strand is called denaturation.

Common physical and chemical factors that cause nucleic acid denaturation are heating, acid, alkali, urea and formamide. During the denaturation process, the spatial conformation of the nucleic acid is destroyed, and the physical and chemical properties are changed. Due to the base exposure inside the double helix molecule, its A260 value will increase greatly. The increase of the A260 value has a certain proportional relationship with the degree of melting. This relationship is called the hyperchromic effect. If the DNA solution is slowly heated and its A260 value is measured at different temperatures, an "S" shaped DNA melting curve can be obtained. It can be seen from the DNA melting curve that DNA denaturation is performed within a relatively narrow temperature.

Before the A260 value started to rise, the DNA was a double helix structure, and some base pairs in the molecules in the rising region began to break. The value increased with the increase of temperature. There were still a small number of base pairs in the flat upper part to make two The strands are also bound together, and this state is maintained until the critical temperature, at which time the last base pair of the DNA molecule is broken, and the two complementary strands are completely separated. Generally, the temperature at which the DNA solution A260 rises to half of the maximum value during heating denaturation is called the melting temperature (Tm) of the DNA. Tm is a useful parameter for studying nucleic acid denaturation. The Tm is generally between 85 and 95 ° C, and the Tm value is directly proportional to the GC content in the DNA molecule.

Nucleic acid renaturation

The process of denaturing DNA under the proper conditions to re-form two separate single strands into double-helix DNA is called renaturation. When heat-denatured DNA is slowly cooled, it is called annealing. DNA renaturation is a very complicated process. There are many factors that affect the rate of DNA renaturation: high DNA concentration, fast renaturation; large DNA molecules renaturate slowly; high temperature will denature DNA, and too low temperature will make mismatching impossible to separate Wait. The best renaturation temperature is Tm minus 25 , which is generally around 60 . The ionic strength is generally above 0.4mol / L.

Nucleic acid hybridization

Single-stranded nucleic acid molecules from different sources with complementary sequences are grouped together based on the principle of base pairing, called nucleic acid hybridization. Hybridization can occur between DNA-DNA, RNA-RNA, and DNA-RNA. Hybridization is one of the techniques commonly used in molecular biology research. It can be used to analyze the structure, location and gene expression of gene tissues. Commonly used hybridization methods include Southern blotting, Northern blotting, and insitu hybridization.