Pyrimidine nucleotides, irradiation

Yields of Destruction of Base Components of Various Purine and Pyrimidine Nucleotides on Irradiation of Their Aqueous Solutions (2 x 10 iM, pH = 7.0) with X-Rays (200 kV) in the Presence of Oxygen... 

Zhang Z-Y, Kuwabara M, Yoshii G (1983) ESR and spin-trapping study of room-temperature radicals in y-irradiated polycrystalline pyrimidine nucleotides. Radiat Res 93 213-231... 

It is well known that basic functions and a-carbon atoms can react readily with nucleotide bases. This is well demonstrated in the photo-cross-linking of 1-propyIamine to 1,3-dimethyluracil both the amino group and the a-carbon form adducts with the pyrimidine ring. Irradiation of solutions of cysteine and uracil give 5-/S-cysteine-6-hydrouracil 5-heteroadducts have also been identified after irradiation of thymine and cysteine. With purines, the C-8 position of adenosine as well as of guanosine can photo-cross-link to 2-propanol. ... 

Comparatively little was previously known about photoaddition reactions to unsaturated substrates of different structure. Elements of water add to the A5 6 in the pyrimidine ring of 1,3-dimethyluracil (CXXXYII)301 and probably of nucleosides and nucleotides of cytosine261,307 upon irradiation with ultraviolet light to give products such as CXXXVIII. CXXXVIII reverts to CXXXVII under the influence of acid, alkali, or heat. 

Upon uv irradiation pyrimidine bases in adjacent nucleotides of a DNA strand become covalently cross-linked. The cross-linking occurs mostly between two thymines to form a thymine dimer (Fig. 16-19). The thymine dimer causes a structural distortion within the DNA chain and represents a physical impediment to replication and transcription. 

Sutherland and co-workers have obtained activated pyrimidine ribonucleotides from cyanamide, cyanoacetylene, glycolaldehyde, glyceraldehyde, and inorganic phosphate in a reaction that bypassed free ribose. The synthesis yielded activated ribonucleotide P-ribocytidine-2 ,3 -cyclic phosphate as a major product and several co-products [17]. Prolonged irradiation of this mixture by 254 nm UV-light caused the destruction of various co-products and the partial conversion of P-ribocytidine-2 ,3 -cyclic phosphate into P-ribouridine-2 ,3 -cyclic phosphate. The authors concluded that there must be some (photo)protective mechanism functioning with the two natural nucleotides but not with other pyrimidine nucleosides and nucleotides [17]. 

Pyrimidines and their oxo-derivatives have attracted immense interest due to their structural resemblance with the nucleotide bases, which is perhaps the reason behind their extensive biological activities, dos Anjos and coworkers have reported a new eco-fiiendly multicomponent methodology for the synthesis of 6-oxo-2,4-diaryl-l,6-dihydro-pyrimidine-5-carbonitriles 43 and 4-amino-2,6-diaryl-pyrimidine-5-caibonitriles 45 using microwave irradiation (2013TL(54)3462). These compounds were found to possess significant analgesic activity. In this protocol, aromatic aldehydes 40 were reacted with ethyl cyanoacetate 42 and benzamidine... 

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