Pyrimidines polynucleotides

The results do display a parallelism in reaction for the two pyrimidine polynucleotides. This parallelism is to that described earlier in static interactions of arginine-rich and lysine-rich proteinoids with polynucleotides 57). This parallelism suggests for the dipeptides a synthetic mechanism in which one kind of amino acid is bound by the polynucleotide while the other amino acid is reacted with the bound one. 

Thermodynamic and kinetic studies have demonstrated that the alternating purine-pyrimidine polynucleotide poly(dA-dT) folds into smaller duplexes which melt independently of each other in solution (16,17). The NMR spectrum should be considerably simplified since all base pairs are structurally equivalent due to the symmetry of the alternating purine-pyrimidine duplex. 

Phosphodiester Linkage The sugar-phosphate backbone of nucleic acids can be probed at the phosphodiester linkage by 31p NMR spectroscopy. There are only two kinds of phosphodiester linkages in alternating purine-pyrimidine polynucleotides, namely dA dT and dT dA in poly(dA-dT). 

The purine(3 -5 Ipyrimidine and the pyrimidine(3 -5 )purine phosphodiester linkages are partially resolved in the proflavine and daunomycin intercalation complexes with poly(dA-dT) with the phosphodiester at the intercalation site shifting to low field. This suggests that these intercalating agents exhibit a sequence specificity in their complexes with alternating purine-pyrimidine polynucleotides. 

Jones GDD, O NeiU P. Kinetics of radiation-induced strand break formation in single-stranded pyrimidine polynucleotides in the presence and absence of oxygen a time-resolved light-scattering study. Int J Radiat Biol. 1991 59 1127-1145. 

A problem that has not been resolved so far is that only pyrimidine polynucleotides can serve as templates for base-pair-directed nucleotide synthesis. 

RNA is relatively resistant to the effects of dilute acid, but gentle treatment of DNA with 1 mM HCl leads to hydrolysis of purine glycosidic bonds and the loss of purine bases from the DNA. The glycosidic bonds between pyrimidine bases and 2 -deoxyribose are not affected, and, in this case, the polynucleotide s sugar-phosphate backbone remains intact. The purine-free polynucleotide product is called apurinic acid. 

The photochemistry of the polynucleotides has been elucidated primarily by studies of the photochemical behavior of the individual pyrimidine and purine bases (the ribose and phosphate groups would not be expected to undergo photochemical reactions in this wavelength range). These studies have shown the pyrimidines (cytosine and thymine) to be roughly ten times more sensitive to UV than the purines (adenine and guanine.) Thus we would expect most of the photochemistry of the nucleic acids to result from the action of light on the pyrimidines. 

Deoxyribonucleic acids readily undergo hydrolysis whereby purine bases are removed to give a derived polynucleotide originally named thymic acid, but now often called apurinic acid. Hydrolysis may be carried out with dilute mineral acid, but recently apurinic acids have been prepared by fission at room temperature with an acidic, ion-exchange resin.236 Under carefully controlled conditions, removal of the purines can be performed quantitatively without destroying the polynucleotide nature of the material and without altering the inter-pyrimidine ratios of the original material.23 ... 

Base Sequence The sequence of purines and pyrimidines in nudeic adds and polynucleotides. It is also called nucleotide or nucleoside sequence. [NIH]... 

Proteins Polynucleotides Poiypeptides -+ RCH(NH2)COOH — amino acids Nucieotides —purine and pyrimidine RCOOH RCH2OHCOOH RCH2OH RCH3. RCH2NH2 bases NHJ, CO2, HS-, CH4, HPO , peptides, amino acids, urea, phenols, indole, fatty acids, mercaptans... 

Mononucleotide Building blocks of polynucleotides. Composed of a phosphate group linked to a five carbon sugar which is linked to a purine or pyrimidine base. 

The presence of small quantities of methylated purine and pyrimidine bases in nucleic acid of micro-organisms and animals has been widely documented. The methyl group is transferred from N-adenosylmethionine to these bases, and methylation occurs at the polynucleotide level rather than by transfer to the acid-... 

The question of energy transfer is introduced also by the fact that polynucleotides frequently exist not only in single-strand forms but also entirely or partially as double-strand helices in which pyrimidine residues on one chain are hydrogen bonded to purine residues on the other chain. The reactivity of the pyrimidine residue can be strongly affected by the presence of its purine partner. An example of this will be found further on. 

If, however, aerated solutions of polynucleotides containing any one of a variety of dyes are exposed to light of a wavelength absorbed by the dye, guanine (18) is selectively oxidized. Adenine (19) is unaffected, and the effect on the pyrimidines is, for most dye sensitizers, slight or nil. 

Bases, Nucleosides, and Nucleotides. The relationship of these components of a nucleic acid or polynucleotide is shown in Chart 10. The numbering of the pyrimidine (uracil) and the purine (adenine) shown is the IUPAC nomenclature used by Chemical Abstracts, and... 

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