The chemical composition of nucleic acids.

elements of nucleic acids are C, H, O, N, P, etc., and < Compared with the "> protein", the composition has two characteristics: first, nucleic acids generally do not contain elements S, and second, the content of P elements in nucleic acids is more and constant, about 9 to 10%. Therefore, the classical method of nucleic acid quantitative determination is to measure the P content to represent the nucleic acid amount.

2, chemical composition and basic units

nucleic acid hydrolyzed can get a lot ofnucleotides so nucleotides are the basic units of nucleic acids. Nucleic acids are polynucleotides formed by the polymerization of many single nucleotides. Nucleotides can be hydrolyzed to produce nucleotides and phosphoric acids, and nucleotides can be further hydrolyzed to produce nitrous oxide and nitrogen-containing bases (Figure 15-1).

Figure 15-1 nucleic acid composition

the bases in the nucleotides are nitrogen-containing hybrids, respectively, they belong to the nicotine derivatives and zirconium derivatives. The purine in nucleotides is mainly cytosine (guanine, G) and adenine (adenine, A), pyrimidine (pyrimidine) is mainly cytosine (cytosine, C), uracil (U) and thymine (thymine, T). BOTH DNA and RNA contain ostrich (G), adenine (A), and cytosine (C); Their chemical structure can be shown in the illustration. the ketones and aminos in the five bases of the

nucleic acids are located next to the nitrogen atoms in the base ring, and structural changes between ketone monools or amino ammonia can occur. This mutual variation structure plays an < role in the > andevolution of the genetically modified gene.

< some nucleic acids >< also contain modified bases > (or rare bases, unusual com ponents), which are mostly derived from methylation or other chemical modifications in different parts of the above-mentioned pyridine or alkali. In general, the content of these bases in nucleic acids is rare, and the distribution in various types of nucleic acids is not equal. Modified bases in DNA are found mainly in phagesDNA, such as 5-methyl cytosine (m5C), 5-hydroxymedocytosine hm5C; TRNA contains the most modified bases, such as 1-thyroid adenine (m1A), 2,21 methyl ostrich (m22G) and 5,6-dihydrourialine (DHU).

and the ring contain conjugated double bonds, which have a strong absorption of UV light at wavelengths of about 260nm. This characteristic of the base is often used for qualitative and quantitative analysis of bases, nucleotides, nucleotides and nucleic acids.

nucleic acids have ribose and deoxyribose, respectively, present in ribonucleotides and DNA nucleotides. In order to distinguish it from the base label, the C-atom number of the sugar is usually added with the word """ as C1', which represents the first carbon atom of the sugar.

Glycosin is connected by glycoside bonds with niacin or nicotine, usually C1' of glycosine and N9 of niacin.

< hydroxyl and phosphoric acid in >in the nucleosides of the >p class" "tt1" became nucleotides by connecting with phosphate bonds. Most of the nucleotides in the organism are phosphates on the C5' hydroxyl of nuclear or DNA, forming 5' nucleotides. Nucleotides produce nucleosides of dphosphate and triphosphate nucleosides in 5' further phosphate. In addition to AMP, for example, there are two forms of adenosine diphosphate (ADP, adenosine 5'-diphosphate) and adenosine triphosphate (ATP, adenosine 5'-triphosphate). The phosphates and triphosphates of nucleotides are mostly intermediates of nucleotides related to metabolism or regulatory substances of enzyme activity and metabolism, as well as intermediates of nucleotides related to metabolism or regulatory substances of enzyme activity and metabolism, as well as important forms of physiological energy storage and supply. < the form of nucleotides and > in the form of p class "tt1". They are mainly 3', 5'-cyclic adenotides (cAMP, adenosine 3', 5'-cyclicmonophosphate) and 3', 5'-cyclinated bird nucleotides (cGMP, guanosine 3', 5'-cyclicphosphosphate, the chemical structure is as follows. Cyclic nucleotides play an important role in the regulation of intracular metabolism and cross-cell membrane signals.

Table 15-1 nucleotides and the corresponding nucleotides, base names in English-language control table

nucleotides	nucleotides	base
adenosines (AMP)	adenosine	adenosine (A)
adenosine monophosphate	adenosine	adenine.
deoxynucleotides (dAMP
deoxydenosine monophosphate	deoxyadenosine
bird nucleotides (GMP	bird	ostrich (gMP	G)
guanosine monophosphate	guanosine	guanine
deoxygenation bird nucleotide (dGMP)
doxyguanosine monophosphate	. deoxyguanosine
CMP	cytosine	cytosine (C)
cytidine monophosphate	cytidine	cytosine
cytosine
dCMP	deoxycytide
deoxycytidine monophosphate	deoxycytidine
thoracic nucleotides (TMP/dTMP	thoracic glycosides	thymusine (T)
thymidine. monophate	thymidine	thymine
ureasides (UMP	ureasides	uridine
(U)	uridine	uracil

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