Nucleotides. Nucleotide: structure, mass, length, sequence Name of DNA nucleotides

Nucleotides are complex biological substances that play a key role in many biological processes. They serve as the basis for building DNA and RNA and, in addition, are responsible for protein synthesis and genetic memory, being universal sources of energy. Nucleotides are part of coenzymes, take part in carbohydrate metabolism and lipid synthesis. In addition, nucleotides are components of active forms of vitamins, mainly of group B (riboflavin, niacin). Nucleotides contribute to the formation of natural microbiocenosis, provide the necessary energy for regenerative processes in the intestine, affect the maturation and normalization of the functioning of hepatocytes.

Nucleotides are low molecular weight compounds consisting of nitrogenous bases (purines, pyrimidines), pentose sugar (ribose or deoxyribose) and 1-3 phosphate groups.

The most common monophosphates are involved in metabolic processes: purines - adenosine monophosphate (AMP), guanosine monophosphate (GMP), pyrimidines - cytidine monophosphate (CMP), uridine monophosphate (UMP).

What caused the interest in the problem of the content of nucleotides in baby food?

Until recently, it was believed that all the necessary nucleotides are synthesized inside the body, and they were not considered as essential nutrients. It was assumed that dietary nucleotides mainly have a "local effect", determining the growth and development of the small intestine, lipid metabolism and hepatic function. However, recent studies (materials of the ESPGAN session, 1997) have shown that these nucleotides become necessary when the endogenous supply is insufficient: for example, in diseases accompanied by energy deficiency - severe infections, diseases of consumption, as well as in the neonatal period, during the rapid growth of the child , in immunodeficiency states and hypoxic injuries. At the same time, the total volume of endogenous synthesis decreases and becomes insufficient to meet the needs of the body. Under such conditions, the intake of nucleotides with food "saves" the body's energy costs for the synthesis of these substances and can optimize tissue function. So, doctors have long advised to use liver, milk, meat, broths, i.e. foods rich in nucleotides, as food after long-term illnesses.

Supplemental nutritional supplementation of nucleotides is essential when feeding infants. Nucleotides were isolated from human milk about 30 years ago. To date, 13 acid-soluble nucleotides have been identified in human milk. It has long been known that the composition of human milk and milk of different animal species is not identical. However, for many years it was customary to pay attention only to the main food components: proteins, carbohydrates, lipids, minerals, vitamins. At the same time, the nucleotides in human milk differ significantly, not only in quantity, but also in composition, from the nucleotides in cow's milk. So, for example, orotate, the main nucleotide in cow's milk, which is contained in significant amounts even in adapted milk mixtures, is not present in human milk.

Nucleotides are a component of the non-protein nitrogen fraction of breast milk. Non-protein nitrogen is responsible for approximately 25% of the total nitrogen in breast milk and contains amino sugars and carnitine, which play a special role in the development of newborns. Nucleotide nitrogen may promote the most efficient protein intake in breastfed infants, who receive comparatively less protein than formula-fed infants.

It was found that the concentration of nucleotides in women's milk exceeds their content in blood serum. This suggests that the mammary glands of a woman synthesize an additional amount of nucleotides that enter breast milk. There are also differences in the content of nucleotides by stages of lactation. So, the largest number of nucleotides in milk is determined at the 2-4th month, and then their content after the 6-7th month begins to gradually decrease.

Early mature milk contains predominantly mononucleotides (AMP, CMP, GMP). Their number in late mature milk is higher than in colostrum, but less than in the milk of the first month of lactation.

The concentration of nucleotides in breast milk is an order of magnitude higher in winter than at similar feeding times in summer.

These data may indicate that in the cells of the mammary glands there is an additional synthesis of nucleotides, since in the first months of life incoming substances from the outside maintain the necessary level of metabolism and energy metabolism of the child. An increase in the synthesis of nucleotides in breast milk in winter is a protective mechanism: at this time of the year, the child is more susceptible to infection and vitamin and mineral deficiencies develop more easily.

As mentioned above, the composition and concentration of nucleotides in the milk of all mammalian species differ, but their number is always lower than in breast milk. This is apparently due to the fact that the need for exogenous nucleotides is especially high in defenseless cubs.

Breast milk is not only the most balanced product for the rational development of the child, but also a delicate physiological system that can change depending on the needs of the child. Breast milk will be comprehensively studied for a long time, not only its quantitative and qualitative composition, but also the role of individual ingredients in the functioning of the systems of a growing and developing organism. Formulas for artificial feeding of infants will also be improved and gradually become real “breast milk substitutes”. The data that breast milk nucleotides have a wider physiological significance for the growing and developing organism served as the basis for introducing them into infant formulas and approaching in concentration and composition to those in breast milk.

The next stage of research was an attempt to establish the effect of nucleotides introduced into infant formulas on fetal maturation and infant development.

The data on the activation of the child 's immune system turned out to be the most illustrative . As is known, IgG is recorded in utero, IgM begins to be synthesized immediately after the birth of a child, IgA is synthesized most slowly, and its active synthesis occurs by the end of the 2-3rd month of life. The effectiveness of their production is largely determined by the maturity of the immune response.

For the study, 3 groups were formed: children who received only breast milk, only formulas with nucleotides, and milk formulas without nucleotides.

As a result, it was found that children who received formulas with nucleotide supplements by the end of the 1st month of life and at the 3rd month had a level of immunoglobulin M synthesis, approximately equal to that of breastfed children, but significantly higher than in children receiving a simple mixture. Similar results were obtained in the analysis of the level of synthesis of immunoglobulin A.

The maturity of the immune system determines the effectiveness of vaccination, because the ability to form an immune response to vaccination is one of the indicators of immunity development in the first year of life. For example, we studied the level of production of antibodies to diphtheria in children who are on the "nucleotide" formula, breastfeeding and mixtures without nucleotides. Antibody levels were measured 1 month after the first and after the last vaccination. It was found that even the first indicators were higher, and the second ones were significantly higher in children who received mixtures with nucleotides.

When studying the effect of feeding with a mixture with nucleotides on the physical and psychomotor development of children, a tendency to better weight gain and a faster development of motor and mental functions was noted.

In addition, there is evidence that nucleotide supplementation promotes faster maturation of the nervous tissue, brain functions and visual analyzer, which is extremely important for premature and morphofunctionally immature children, as well as babies with ophthalmological problems.

Everyone knows the problems with the formation of microbiocenosis in young children, especially in the first months. These are the phenomena of dyspepsia, intestinal colic, increased flatulence. The consumption of "nucleotide" mixtures allows you to quickly normalize the situation, without the need for correction with probiotics. In children who received mixtures with nucleotides, dysfunction of the gastrointestinal tract, stool instability were less common, they tolerated the introduction of subsequent complementary foods more easily.

However, when using mixtures with nucleotides, it must be borne in mind that they reduce the frequency of stools, so they should be recommended with caution in children with constipation.

These mixtures may be of particular importance in children with malnutrition, anemia, as well as those who have undergone hypoxic disorders in the neonatal period. Mixtures with nucleotides help to solve a number of problems that arise when nursing premature babies. In particular, we are talking about poor appetite and low weight gain throughout the first year of life, in addition, the use of mixtures contributes to a more complete psychomotor development of babies.

Based on the foregoing, the use of mixtures with nucleotide additives is of great interest to us, doctors. We can recommend these mixtures to a large circle of children, especially since the mixtures are not medicinal. At the same time, we consider it important to point out the possibility of individual taste reactions in young children, especially when transferring a child from a regular mixture to a nucleotide-containing one. So, in some cases, even when using mixtures of one company, we noted negative reactions in the child, up to the refusal of the proposed mixture. However, all literary sources claim that nucleotides not only do not negatively affect the taste, but, on the contrary, improve them without changing the organoleptic properties of the mixture.

We present an overview of mixtures containing nucleotide additives and available on our market. These are whey mixtures from Frizland Nutrition (Holland) "Frisolak", "Frisomel", which contain 4 nucleotides identical to the nucleotides of human milk; whey mixture Mamex (Intern Nutrition, Denmark), NAN (Nestlé, Switzerland), Enfamil (Mead Johnson, USA), Similac formula plus mixture (Abbott Laboratories, Spain/USA). The number and composition of nucleotides in these mixtures are different, which is determined by the manufacturer.

All manufacturers are trying to choose the ratio and composition of nucleotides, bringing it as close as possible technically and biochemically to those of breast milk. It is quite clear that the mechanical approach is not physiological. Undoubtedly, the introduction of nucleotides into infant formulas is a revolutionary step in the production of breast milk substitutes, contributing to the maximum approximation to the composition of human breast milk. However, no mixture can yet be considered physiologically completely identical to this unique, universal and necessary product for the child.

Literature

1. Gyorgy. P. Biochemical aspects. Am.Y.Clin. Nutr. 24(8), 970-975.
2. Europan society for Pediatric Gastroenterology and Nutrition (ESPGAN). Committee on Nutrition: Guidelines on infant nutrition I. Recommendations on the composition of an adapted formula. Asta Paediatr Scand 1977; Suppl 262: 1-42.
3. James L. Leach, Jeffreu H. Baxter, Bruce E. Molitor, Mary B. Ramstac, Marc L\ Masor. All potentially available breast milk nucleotides during lactation // American Journal of Clinical Nutrition. - June 1995. - T. 61. - No. 6. - S. 1224-30.
4. Carver J. D., Pimental B., Cox WI, Barmess L. A. Dietary nucleotidi effects upon immune function in infants. Pediatrics 1991; 88; 359-363.
5. Wow. R., Stringel G., Thomas R. and Quan R. (1990) Effect of dietari nucleosides on growth and maturation of the developing gut in the rat. J. Pediatr. Gastroenterol. Nutr. 10, 497-503.
6. Brunser O., Espinosa J., Araya M., Gruchet S. and Gil A. (1994) Effect of dietari nucleotide suppementation on diarrhoeal disease in infants. Asta Paediatr. 883. 188-191.
7. Keshishyan E. S., Berdnikova E. K.//Mixtures with nucleotide additives for feeding children in the first year of life//Baby nutrition of the XXI century. - S. 24.
8. David. New technologies for improving baby food//Pediatrics. - 1997. - No. 1. - S. 61-62.
9. Keshishyan E. S., Berdnikova E. K. Mixtures with nucleotide additives for feeding infants. Expected effect//Pediatrics. Consilium medicum. - Appendix No. 2. - 2002. - S. 27-30.

E. S. Keshishyan, Doctor of Medical Sciences, Professor
E. K. Berdnikova
Moscow Research Institute of Pediatrics and Pediatric Surgery, Ministry of Health of the Russian Federation, Moscow

The human body contains a large number of organic compounds, without which it is impossible to imagine a stable course of metabolic processes that support the vital activity of all. One of these substances are nucleotides - these are phosphoric esters of nucleosides, which play a crucial role in the transmission of information data, as well as chemical reactions with the release of intracellular energy.

As independent organic units form the filling composition of all nucleic acids and most coenzymes. Let us consider in more detail what nucleoside phosphates are and what role they play in the human body.

What is a nucleotide made of. It is considered an extremely complex ester belonging to the group of phosphorus acids and nucleosides, which, according to their biochemical properties, are among the N-glycosides and contain heterocyclic fragments associated with glucose molecules and a nitrogen atom.

In nature, DNA nucleotides are the most common.

In addition, organic substances with similar structural characteristics are also distinguished: ribonucleotides, as well as deoxyribonucleotides. All of them, without exception, are monomeric molecules belonging to complex biological substances of the polymer type.

They form the RNA and DNA of all living beings, from the simplest microorganisms and viral infections to the human body.

The rest of the molecular structure of phosphorus among nucleoside phosphates forms an ether bond with two, three, and in some cases immediately with five hydroxyl groups. Almost without exception, nucleotides are among the essential substances that were formed from the residues of phosphoric acid, so their bonds are stable and do not break down under the influence of adverse factors of the internal and external environment.

Note! The structure of nucleotides is always complex and is based on monoesters. The sequence of nucleotides can change under the influence of stress factors.

Biological role

The influence of nucleotides on the course of all processes in the body of living beings is studied by scientists who study the molecular structure of the intracellular space.

Based on laboratory findings obtained as a result of many years of work by scientists from around the world, the following role of nucleoside phosphates is distinguished:

• a universal source of vital energy, due to which cells are nourished and, accordingly, the normal functioning of tissues that form internal organs, biological fluids, epithelial cover, and the vascular system is maintained;
• are transporters of glucose monomers in cells of any type (this is one of the forms of carbohydrate metabolism, when consumed sugar is transformed into glucose under the influence of digestive enzymes, which is carried to every corner of the body along with nucleoside phosphates);
• perform the function of a coenzyme (vitamin and mineral compounds that help provide cells with nutrients);
• complex and cyclic mononucleotides are biological conductors of hormones that spread along with the blood flow, and also enhance the effect of neuronal impulses;
• allosterically regulate the activity of digestive enzymes produced by pancreatic tissues.

Nucleotides are part of nucleic acids. They are connected by three and five bonds of the phosphodiester type. Geneticists and scientists who have devoted their lives to molecular biology continue laboratory research on nucleoside phosphates, so every year the world learns even more interesting things about the properties of nucleotides.

The sequence of nucleotides is a kind of genetic balance and the balance of the arrangement of amino acids in the DNA structure, a peculiar order of placement of ester residues in the composition of nucleic acids.

It is determined using the traditional method of sequencing the biological material selected for analysis.

T, thymine;

A - adenine;

G, guanine;

C, cytosine;

R – GA adenine in complex with guanine and purine bases;

Y, TC pyrimidine compounds;

K, GT nucleotides containing a keto group;

M - AC included in the amino group;

S - GC powerful, characterized by three hydrogen compounds;

W - AT are unstable, which form only two hydrogen bonds.

The sequence of nucleotides may change, and the designations in Latin letters are necessary in cases where the order of the ether compounds is unknown, is insignificant, or the results of primary studies are already available.

The greatest number of variants and combinations of nucleoside phosphates is characteristic of DNA. The symbols A, C, G, U are sufficient to write the essential compounds of RNA. The last letter designation is the substance uridine, which is found only in RNA. The symbolic sequence is always written without spaces.

Useful video: nucleic acids (DNA and RNA)

How many nucleotides are in DNA

In order to understand in as much detail as possible what is at stake, one should have a clear understanding of the DNA itself. This is a separate type of molecules that have an elongated shape and consist of structural elements, namely nucleoside phosphates. How many nucleotides are in DNA? There are 4 types of essential compounds of this type that are part of DNA. These are adenine, thymine, cytosine and guanine. All of them form a single chain, from which the molecular structure of DNA is formed.

The structure of DNA was first deciphered back in 1953 by American scientists Francis Crick and James Watson. One molecule of deoxyribonucleic acid contains two chains of nucleoside phosphates. They are placed in such a way that they look like a spiral twisting around its axis.

Note! The number of nucleotides in DNA is unchanged and limited to only four species - this discovery brought humanity closer to deciphering the complete human genetic code.

In this case, the structure of the molecule has one important feature. All nucleotide chains have the property of complementarity. This means that only essential compounds of a certain type are placed opposite each other. It is known that adenine is always located opposite thymine. No other substance other than guanine can be found opposite cytosine. Such nucleotide pairs form the principle of complementarity and are inseparable.

Weight and length

With the help of complex mathematical calculations and laboratory studies, scientists were able to establish the exact physical and biological properties of the essential compounds that form the molecular structure of deoxyribonucleic acid.

It is known that the length of one intracellular residue, consisting of amino acids in a single polypeptide chain, is 3.5 angstroms. The average mass of one molecular residue is 110 amu.

In addition, nucleotide-type monomers are also isolated, which are formed not only from amino acids, but also have ether components. These are DNA and RNA monomers. Their linear length is measured directly inside the nucleic acid and is at least 3.4 angstroms. The molecular weight of one nucleoside phosphate is in the range of 345 amu. These are the initial data that are used in practical laboratory work devoted to experiments, genetic studies and other scientific activities.

Medical designations

Genetics, as a science, developed back in the period when there were no studies of the DNA structure of humans and other living beings at the molecular level. Therefore, in the period of premolecular genetics, nucleotide bonds were designated as the smallest element in the structure of the DNA molecule. Both previously and at the present time, essential substances of this type were subject to. It could be spontaneous or induced, therefore, the term “recon” is also used to refer to nucleoside phosphates with a damaged structure.

To define the concept of the onset of a possible mutation in nitrogenous compounds of nucleotide bonds, the term "muton" is used. These designations are more in demand in laboratory work with biological material. They are also used by geneticists who study the structure of DNA molecules, the ways in which hereditary information is transmitted, how it is encrypted, and possible combinations of genes resulting from the fusion of the genetic potential of two sexual partners.

In contact with

Nucleotide– nucleoside + one or more phosphoric acid residues. Nucleoside- nitrogenous base and pentose molecule. The composition of nucleotides includes two purine bases (adenine and guanine) and 3 pyrimidine bases (thymine, uracil, cytosine). Sometimes there are minor nitrogenous bases: pseudouracil, methyluridine, methylcytosine, methyladenine.

Nomenclature:

Primary structure of NK- a polynucleotide chain with a strictly defined sequence of nucleotides interconnected by a 3'-5'-phosphodiester bond.

Properties of nucleotides: 1) acquire a negative charge 2) have bright

Pronounced acidic properties.

Features of the structure, function and distribution of DNA and RNA in the cell:

Localized mainly in the nucleus, also in mitochondria and chloroplasts	Located mainly in the cytoplasm
The structure includes A, T, G, C + deoxyribose + phosphoric acid residue.	The structure includes A, U, G, C + ribose + phosphoric acid residue
Double helix (6 types are known: A-E, Z, the predominant B-form)	Single-stranded (although it can fold to form "hairpins"). Has varieties (mRNA, mRNA, tRNA)
Vary in size (DNA usually consists of a large number of nucleotides)
1. Provides Protein Synthesis 2. Carrier of hereditary information	Provide protein synthesis
Obeys the rules of Chargaff	Doesn't obey Chargaff's rules

DNA primary structure analysis method (Sanger):

Based on the DNA polymerase reaction: isolation of DNA ® cutting it with restriction enzymes ® denaturation of DNA fragments and obtaining single-stranded molecules used as a template ® add a primer and substrates for DNA synthesis ® divide the mixture into four test tubes, add one of the stop nucleotides to each ( dideoxynucleotides) and DNA polymerase ® synthesis stops when DNA polymerase encounters a stop nucleotide ® after the end, in each tube there are fragments ending in a certain nucleotide ® fragments are separated by electrophoresis in agarose gel and analyzed.

Nucleotide

Nucleotides- natural compounds, from which, like bricks, chains are built. Also, nucleotides are part of the most important coenzymes (organic compounds of non-protein nature - components of some enzymes) and other biologically active substances, serve as energy carriers in cells.

The molecule of each nucleotide (mononucleotide) consists of three chemically distinct parts.

1. This is a five-carbon sugar (pentose):

Ribose (in this case, nucleotides are called ribonucleotides and are part of ribonucleic acids, or)

Or deoxyribose (nucleotides are called deoxyribonucleotides and are part of deoxyribonucleic acid, or).

2. Purine or pyrimidine nitrogen base linked to the carbon atom of a sugar, forms a compound called a nucleoside.

3. One, two or three phosphoric acid residues , attached by ether bonds to the sugar carbon, form a nucleotide molecule (in DNA or RNA molecules there is one phosphoric acid residue).

The nitrogenous bases of DNA nucleotides are purines (adenine and guanine) and pyrimidines (cytosine and thymine). RNA nucleotides contain the same bases as DNA, but thymine in them is replaced by uracil, which is similar in chemical structure.

Nitrogenous bases, and, accordingly, the nucleotides that include them, in the biological literature are usually denoted by initial letters (Latin or Ukrainian / Russian) in accordance with their names:
- - A (A);
- - G (G);
- - C (C);
- thymine - T (T);
- uracil - U (U).
The combination of two nucleotides is called a dinucleotide, several - an oligonucleotide, sets - a polynucleotide or nucleic acid.

In addition to the fact that nucleotides form DNA and RNA chains, they are coenzymes, and nucleotides bearing three phosphoric acid residues (nucleoside triphosphate) are sources of chemical energy, which is contained in phosphate bonds. The role of such a universal energy carrier as adenosine triphosate (ATP) is extremely important in all life processes.

Nucleotides are: nucleic acids (polynucleotides), the most important coenzymes (NAD, NADP, FAD, CoA) and other biologically active compounds. Free nucleotides in the form of nucleoside mono-, di- and triphosphate are found in significant amounts in cells. Nucleoside triphosphate - nucleotides containing 3 phosphoric acid residues, have energy-rich accumulation in macroergic bonds. ATP plays a special role - a universal energy accumulator. The high-energy phosphate bonds of nucleotide triphosphates are used in the synthesis of polysaccharides ( uridine triphosphate, ATP), proteins (GTP, ATP), lipids ( cytidine triphosphate, ATP). Nucleoside triphosphates are also substrates for the synthesis of nucleic acids. Uridine diphosphate is involved in carbohydrate metabolism as a carrier of monosaccharide residues, cytidine diphosphate (carrier of choline and ethanolamine residues) in lipid metabolism.

play an important regulatory role in the body cyclic nucleotides. Free nucleoside monophosphates are formed by synthesis or by hydrolysis of nucleic acids under the action of nucleases. Sequential phosphorylation of nucleoside monophosphates leads to the formation of the corresponding nucleotide triphosphates. The breakdown of nucleotides occurs under the action of nucleotidase (with the formation of nucleosides), as well as nucleotide pyrophosphorylase, which catalyze the reversible reaction of cleavage of nucleotides to free bases and phosphoribosyl pyrophosphate.

Nucleotides are phosphate esters of nucleosides.

Their chemical composition: nitrogenous base (A.O.) + pentose + phosphoric acid

Phosphoric esters are formed with the participation of hydroxyl groups of pentoses. The positions of the phosphoric ester groups are usually denoted using the designation ("), for example: 5 ", 3 "

Preliminary brief information: nucleotides play an extremely important role in the life of the cell.

Classification of nucleotides

Nucleotides made up of one molecule A.O, pentose, phosphoric acid, called mononucleotides. Mononucleotides may contain one phosphoric acid molecule, two or three phosphoric acid molecules connected to each other.

Combination of two mononucleotides called dinucleotide. IN The composition of a dinucleotide usually contains different nitrogenous bases or one other cyclic compound, for example, a vitamin ..

Cyclic mononucleotides play a special role in biochemical processes.

Nomenclature of mononucleotides.

Go to title nucleoside added based on the amount of phosphate residues, ʼʼ monophosphateʼʼ, ʼʼ diphosphateʼʼ, ʼʼ triphosphateʼʼ, indicating their position in the pentose cycle - digital designation of the place with a sign ("),

The position of the phosphate group in position (5") is the most common and typical, and therefore it can be omitted (AMP, GTP, UTP, d AMF, etc.)

The remaining positions are indicated necessarily (3 "- AMF, 2" - AMF, 3 "- d AMF)

5"-adenosine monophosphate

(5"- AMF or AMF)

Names of the most common nucleotides

nucleoside	nucleoside monophosphate	nucleoside diphosphate	nucleoside triphosphate
adenosine	5 "-Adenosine monophosphate (5" - AMP or AMP) 5 "-adenylic acid	5 "-adenosine diphosphate (5"-ADP or ADP)	5 "-adenosine triphosphate (5"-ATP or ATP)
adenosine	3"-adenosine monophosphate (3"-AMP) 3"-adenylic acid	not found in vivo	not found in vivo
guanosine	5 "-guanosine monophosphate (5" - GMF or GMF)	5 "-guanosine diphosphate (5" - HDF or HDF)	5 "-guanosine triphosphate (5" - GTP or GTP)
guanosine	3"-guanosine monophosphate (3"- GMP) 3"-guanilic acid	not found in vivo	not found in vivo
deoxy adenosine	5 "-deoxyadenosine monophosphate (5"- d AMF or d AMF)	5 "-deoxyadenosine diphosphate (5"- d ADFili d ADP)	5 "-deoxyadenosine triphosphate (5"- d ATFili d ATP)
uridine	5 "-uridine monophosphate (5" - UMF or UMF)	5 "-uridine diphosphate (5" - UDP or UDP)	5 "-uridine triphosphate (5" - UTP or UTP)
cytidine	5 "-cytidine monophosphate (5" - CMF or CMF)	5 "-cytidine diphosphate (5" - CDP or CDP)	5 "-cytidine triphosphate (5" - CTP or CTP)

Nucleotides formed with the participation of ribose can contain phosphoric acid residues in three positions (5", 3", 2"), and with the participation of deoxyribose - only in two positions (5", 3"), in position 2" there is no hydroxy group. This circumstance is very important for the structure of DNA.

The absence of a hydroxy group in the second position has two important consequences:

The polarization of the glycosidic bond in DNA decreases and it becomes more resistant to hydrolysis.

2-O-deoxyribose cannot undergo either epimerization or conversion to ketosis.

In the cell, nucleoside monophosphate is sequentially converted to diphosphate, and then to triphosphate.

For example: AMP ---> ADP ---> ATP

The biological role of nucleotides

Everything nucleoside diphosphates And nucleoside triphosphates belong to high-energy (macroergic) compounds.

Nucleoside triphosphates participate in the synthesis of nucleic acids, provide the activation of bioorganic compounds and biochemical processes that take place with the expenditure of energy. Adenosine triphosphate (ATP) is the most abundant macroergic compound in the human body. The content of ATP in the skeletal muscles of mammals is up to 4 g / kg, the total content is about 125 ᴦ. In humans, the rate of ATP metabolism reaches 50 kg/day. Hydrolysis of ATP produces adenosine diphosphate(ADP)

macroergic connections

ATP contains different types of chemical bonds:

N-β- glycosidic

Ester

Two anhydride (biologically macroergic)

In conditions in vivo hydrolysis of the macroergic bond of ATP is accompanied by the release of energy (about 35 kJ / mol), which provides other energy-dependent biochemical processes.

ATP + H2O - enzyme ATP hydrolase --> ADP + H3 PO4

In aqueous solutions ADP and ATP unstable . At 0 0 SATP is stable in water for only a few hours, and when boiled for 10 minutes.

Under the action of alkali, two terminal phosphates (anhydride bonds) are easily hydrolyzed, and the last one (ester bond) is difficult. During acid hydrolysis, the N-glycosidic bond is easily destroyed.

For the first time, ATP was isolated from muscles in 1929 ᴦ. K. Loman. Chemical synthesis carried out in 1948 ᴦ. A. Todd.

Cyclic nucleotides are mediators in the transmission of hormone signals by changing the activity of enzymes in the cell.

Οʜᴎ are formed from nucleoside triphosphates.

ATP - cyclase enzyme --> cAMP + H4 P2 O7

After the action is completed, hydrolysis of the cyclic nucleotide occurs. . Two compounds can be formed 5 "-AMP and 3" -AMP, but under biological conditions only 5 "-AMP is formed,

Cyclic adenosine monophosphate (cAMP)

11.5. Structure of nucleic acids

The primary structure of RNA and DNA is the sequential connection of nucleotides in a polynucleotide chain. The skeleton of a polynucleotide chain consists of carbohydrate and phosphate residues, heterocyclic nitrogenous bases are connected to carbohydrates through an N-β - glycosidic bond. From a biological point of view, triplets - blocks of nucleotides from three nitrogenous bases, each of which encodes an amino acid or has a certain signal function, are of the utmost importance.

The structure of the NC can be represented schematically:

5" 3" 5" 3" 5" 3"

phosphate -- pentose -- phosphate -- pentose -- phosphate -- pentose-OH

In the primary structure of DNA Start chains are determined by the pentose containing phosphate in position 5. Pentoses in the polynucleotide chain are connected via phosphate bonds 3 "→ 5". On the end chains in position 3 "- pentose OH- group remains free.

Higher order DNA structure - double helix

The scientific description of the secondary structure of DNA is one of the greatest discoveries of mankind in the twentieth century. Biochemist D. Watson and physicist F. Creek in 1953 proposed a model of the structure of DNA and the mechanism of the replication process. In 1962 ᴦ. they were awarded the Nobel Prize.

In a popular form, the story is described in James Watson's book ʼʼ The Double Helixʼʼ, M.: Mir, 1973. The book very interestingly describes the history of joint work, with humor and light irony of the author to such a significant event, the happy ʼʼculpritsʼʼ of which were two young scientists. Since the discovery of the structure of DNA, mankind has received a tool for the development of a new direction - biotechnology, protein synthesis by gene recombination (hormones in the medical industry receive insulin, erythropoietin, and many others).

Research contributed to the discovery of the structure of DNA E.Chargaff regarding the chemical composition of DNA. He found out:

The number of pyrimidine bases is equal to the number of purines

The amount of thymine is equal to the amount of adenine, and the amount of cytosine is equal to the amount

A = T G = C

A + G = T + C

A + C = T + G

These relationships are called Chargaff rules .

The DNA molecule consists of two twisted helices. The skeleton of each helix is ​​a chain of alternating residues of deoxyribose and phosphoric acid. The spirals are oriented in such a way that they form two unequal spiral grooves that run parallel to the main axis. These grooves are filled with proteins histones. Nitrogenous bases are located inside the helix, almost perpendicular to the main axis and form complementary pairs between the chains A…T and G…C.

The total length of DNA molecules in each cell reaches 3 cm. The average cell diameter is 10–5 m, the DNA diameter is only 2‣‣‣10–9 m.

The main parameters of the double helix:

* diameter 1.8 - 2nm,

* on one turn 10 nucleotides

* coil pitch height ~ 3.4 nm

* distance between two nucleotides 0.34 nm.

The bases are located perpendicular to the axis of the chain.

* direction of polynucleotide chains antiparallel

* communication between furanose cycles of deoxyribose through

phosphoric acid is carried from position 3` to position 5` in

each of the chains.

* The beginning of the chain - the hydroxyl group of the pentose is phosphorylated at the position

5`, the end of the chain is the free hydroxyl group of pentose in position 3`.

* In the composition of DNA and RNA, the nucleoside fragments are in the anti-conformation; the pyrimidine ring of purine is located to the right of the glycosidic bond. Only this position allows the formation of a complementary pair (see nucleotide formulas)

* There are three types of interactions between nitrogenous bases:

1. “Transverse”, complementary pairs of two chains are involved. A ʼʼcyclicʼʼ electron transfer occurs between two nitrogenous bases (T - A, U - C), an additional p-electron system is formed, which provides additional interaction and protects nitrogenous bases from unwanted chemical influences. Between adenine and thymine make two hydrogen bonds, and three hydrogen bonds between guanine and cytosine.

2. ʼʼ Vertical ʼʼ (stacking), due to stacking in “stacks”, nitrogenous bases of one chain are involved. ʼʼStacking interactionʼʼ has even more value in stabilizing the structure than the interaction in complementary pairs

3. Interaction with water plays an essential role in maintaining the spatial structure of the double helix, which adopts the most compact structure to reduce the surface of contact with water and directs hydrophobic heterocyclic bases into the interior of the helix.

Structure and composition of nucleoprotein complexes

Several types of interactions are involved in the binding of a nucleic acid to a protein:

electrostatic

Hydrogen bonds

hydrophobic

Real three-dimensional models of DNA, ribosomes, informosomes, and nucleic acids of viruses were built based on the results of X-ray diffraction analysis using computer simulation.

DNA histone proteins have pronounced basic properties and are distinguished by a high degree of evolutionary conservatism. According to the ratio of two basic amino acids lysine / arginine, they are divided into 5 classes: H1, H2A, H 2B, H3, H4

Nucleotides - concept and types. Classification and features of the category "Nucleotides" 2017, 2018.