Biochemistry

CHAPTER 5. CHEMISTRY OF NUCLEIC ACIDS GENERAL CHARACTERISTICS Nucleic acids were discovered in 1868 by the Swiss chemist F.Misher. The scientist isolated these substances from the nuclei of cells and called them nuclein (from lat. Nucleus - the nucleus). However, a more detailed study of these compounds was carried out only at the end of the 40s of our century. Chemists P.Levin, E.Chargaff, J.Watson, F.Crick, B.V.Kedrovsky, A.M.Belozersky, A.S.Spirin and others made a great contribution to deciphering the composition and role of nucleic acids. Nucleic acids are a class of polymers responsible for storing and transmitting genetic information , as well as its implementation in the synthesis of cellular proteins . They are the universal components of all living organisms. Nucleic acids are white substances, in the free state, poorly soluble in water, but good in the form of salts and alkali metals. These compounds have a high molecular weight (millions of Da), contain about 15 % nitrogen and 10% phosphorus, have pronounced acidic properties (due to phosphoric acid) and, at physiological pH, carry a high negative charge, which is why they are mobile in an electric field. Chemical composition and structure A nucleic acid molecule is a polynucleotide consisting of a large number of mononucleotides. Mononucleotides can be located in different ways in the polynucleotide molecule, which determines the diversity of nucleic acids in nature. Each mononucleotide consists of a nitrogenous base (purine or pyrimidine), a carbohydrate - pentose (ribose or deoxyribose) and phosphoric acid. Mononucleotides are designated by the name of the nitrogenous base included in their composition: cytidine monophosphate (CMP) or cytidine monophosphoric acid; uridine monophosphate (UMF) or uridine monophosphoric acid; adenosine monophosphate (AMP) or adenosine monophosphoric acid; guanosine monophosphate (GMF) or guanosine monophosphoric acid. Of the nitrogen bases, two purine bases (purine derivatives) - adenine (6- aminopurine) and guanine (2-amino-6-hydroxypurin) and three pyrimidine (pyrimidine derivatives) - thymine (5-methyluracil), cytosine (2- hydroxy-6- aminopyrimidine) and uracil (2,6-hydroxypyrimidine), which are contained in the ketoform in the composition of nucleic acids. 116