About nucleic acid
Nucleic acid definition
Nucleic acid the biomacromolecule formed by the polymerization of nucleotide monomers is the most basic and important component of biological cells. It is generally believed that biological evolution begins with nucleic acid, because only nucleic acid can replicate itself in all living matter. Today it is known that nucleic acids are the storage and transmitter of biological genetic information. The blueprint of an organism is encoded in its nucleic acid molecule.
Nucleic acids are a class of biopolymers, and are an essential component of all known life forms.
Nucleic acid is a general term for deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
Nucleic acids are composed of nucleotides, and nucleotide monomers are composed of 5-carbon sugars, phosphate groups, and nitrogen-containing bases. If the 5-carbon sugar is ribose, the polymer formed is RNA; if the 5-carbon sugar is deoxyribose, the polymer formed is DNA.
Nucleic acid structure
The primary structure of nucleotides refers to the arrangement order of the nucleotides or deoxynucleotides constituting the nucleic acid from the 5′ end to the 3′ end, that is, the nucleotide sequence. Since the difference between nucleotides is the difference in bases, the primary structure of a nucleic acid is its base sequence.
Nucleic acid molecules are usually very large. In fact, DNA molecules may be the largest single biomolecule known. But there are also relatively small nucleic acid molecules.
Nucleic acid molecules range in size from 21 nucleotides (small interfering RNA) to large chromosomes (human chromosome 1 is a single molecule containing 247 million base pairs  )
Nucleic acid types
Nucleotides are the basic units that make up nucleic acids, that is, the monomers that make up a nucleic acid molecule. A nucleotide molecule is composed of a molecule of nitrogen-containing bases, a molecule of five-carbon sugar and a molecule of phosphoric acid. According to the difference of five carbon sugars, nucleic acids can be divided into two categories: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
Nucleic acid function
DNA: Not only is it a basic genetic material, but also plays an important role in the biosynthesis of protein, so it plays a decisive role in a series of major life phenomena such as growth, inheritance, mutation, etc.
RNA: As genetic material: only in RNA viruses; not as genetic material: in DNA control protein synthesis process. mRNA is a direct template for protein synthesis, tRNA can carry specific amino acids, rRNA is a component of ribosome; catalytic effect: a kind of enzyme.
Nucleic acid research
Nucleic acid test
The nucleic acid detection substance is a viral nucleic acid. Nucleic acid detection is to find the nucleic acid of foreign viruses in the patient's respiratory tract specimens, blood or feces to determine whether it is infected by the new coronavirus. Therefore, once the nucleic acid is detected as "positive", it can prove that there is a virus in the patient.
Principles of nucleic acid testing
All organisms contain nucleic acids except prions. Nucleic acids include deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The new coronavirus is a virus containing only RNA. The specific RNA sequence in the virus distinguishes the virus from other pathogens. Markers.
Nucleic acid hybridization
Nucleic acid hybridization: the process of complementary nucleotide sequences (DNA and DNA, DNA and RNA, RNA and RNA, etc.) forming non-covalent bonds through Watson-Crick base pairing, thereby forming stable homologous or heteroduplex molecules, known as nucleic acid molecular hybridization technology, also known as nucleic acid hybridization.
The principle is the theory of nucleic acid denaturation and renaturation. That is, double-stranded nucleic acid molecules are untwisted under certain physical and chemical factors, and after conditions are restored, double-stranded structures can be formed according to the law of base pairing. Hybridization is usually performed on a supporting membrane, so it is also called nucleic acid blot hybridization.
According to the different samples, it is divided into Southern blot hybridization and Northern blot hybridization.
Nucleic acid extraction
Nucleic acid extraction principles and requirements
1. Ensure the integrity of the primary structure of nucleic acids
2. Eliminate the contamination of other molecules (such as RNA interference when extracting DNA)
3. There should be no organic solvents and high concentrations of metal ions that inhibit enzymes in the nucleic acid sample
4. Reduce macromolecules such as proteins, polysaccharides and lipids as much as possible
Nucleic acid extraction system
The acid extraction system needs to apply the matching nucleic acid extraction reagents to automatically complete the extraction of sample nucleic acids.
Nucleic acid extractor, also known as nucleic acid purification instrument, is an instrument that uses matching nucleic acid extraction reagents to automatically complete sample nucleic acid extraction. Apparatuses that have only been popularized in recent years.
Nucleic acid extraction methods
Concentrated salt method: Separate the two by using RNA and DNA with different solubility in salt solution
Organic solvent extraction method: Organic solvent is used as a protein denaturant, while inhibiting the degradation of nuclease Density gradient centrifugation method: Separate various contents using the principle of different contents and different densities
Adsorption material combination method:
1. Siliceous material: high salt and low PH combined with nucleic acid, low salt and high PH eluted
2. Anion exchange resin: low salt and high PH combined with nucleic acid, high salt and low PH eluted
3. Magnetic beads: Different groups can be adsorbed on the magnetic beads to absorb different targets, so as to achieve the purpose of separation
Nucleic acid extraction steps
The main steps of nucleic acid extraction include:
① Cell breaking and nucleic acid release;
②Isolation and purification of nucleic acid;
③The three main steps of nucleic acid concentration, precipitation and washing.