475

54 6. Mutagenic substances and factors that alter the structure of nucleic acids. Mutagenic effects of HNO 2  on the structure of nucleic acids. 7. Nucleoproteins. Definition, examples. Test-control on the topic «Chemistry of nucleic acids». Homework exercises. 1. Write formulas of purine and pyrimidine nitrogen bases in lactim-lactam form. 2. Write the schemes of formation and formulas of purine nucleosides: ad- enosine, guanosine, deoxyadenosine and deoxyguanosine. 3. Write the schemes of formation and formula of pyrimidine nucleosides: uridine, cytidine, deoxythymidine, deoxycytidine. 4. Write schemes for the formation and formula of purine 5’-nucleotides: adenosine monophosphate, guanosine monophosphate, deoxyadenosine mono- phosphate and deoxyguanosine monophosphate. 5. Write schemes for the formation and formula of pyrimidine 5’-nucleo- tides: uridine monophosphate, cytidine monophosphate, deoxythymidine mo- nophosphate, deoxycytidine monophosphate. 6. Write the ATP formulas, note the ester bonds. 7. Write formulas of cyclic nucleotides: 3’, 5’-cAMP, 3’, 5’-cGMP. 8. Write a schemes of the formation and formulas of dinucleotides formed from: a) AMP and UMP; b) dGMP and dTMP; c) GMP and CMP; d) dCMP and dAMP; e) CMP and UMP; f) AMP and GMP. Laboratory work. Hydrolysis of yeast nucleoproteins and determination of protein, nitrogenous bases, ribose, phosphoric acid in the hydrolyzate. Experiment 1. Biuret reaction to protein. Place 5–6 drops of yeast hydrolyzate in a test tube. Add an equal volume of 10% NaOH solution and add 1–2 drops of CuSO 4  solution. What are you observing? Write the conclusion from the experience. Experiment 2. Test for purine bases . Mix 1 ml of yeast hydrolyzate with ammonia solution to alkaline reaction in the test tube. Test the reaction with a litmus test. Add 0.5 ml of ammonia solution of AgNO 3. What are you observing? During the reaction, a silver salt of the purine base is formed: N N N N O O H H H + AgNO 3 H H O O N N N N Ag + HNO 3