Purines adenines

Avery s paper prompted other biochemists to rethink their ideas about DNA One of them Erwin Chargaff of Columbia University soon discovered that the distribution of adenine thymine cytosine and guanine differed from species to species but was the same within a species and within all the cells of a species Perhaps DNA did have the capacity to carry genetic information after all Chargaff also found that regardless of the source of the DNA half the bases were purines and the other half were pyrimidines Significantly the ratio of the purine adenine (A) to the pyrimidine thymine (T) was always close to 1 1 Likewise the ratio of the purine guanine (G) to the pyrimidine cyto sine (C) was also close to 1 1 For human DNA the values are... 

The primary stmcture of DNA is based on repeating nucleotide units, where each nucleotide is made up of the sugar, ie, 2 -deoxyribose, a phosphate, and a heterocycHc base, N. The most common DNA bases are the purines, adenine (A) and guanine (G), and the pyrimidines, thymine (T) and cytosine (C) (Fig. 1). The base, N, is bound at the I -position of the ribose unit through a heterocycHc nitrogen. 

As indicated in Chapter 11, the base pairing in DNA is very specific the purine adenine pairs with the pyrimidine thymine the purine guanine pairs with the pyrimidine cytosine. Further, the A T pair and G C pair have virtually identical dimensions (Figure 12.10). Watson and Crick realized that units of such similarity could serve as spatially invariant substructures to build a polymer whose exterior dimensions would be uniform along its length, regardless of the sequence of bases. 

The sugar component in RNA is ribose, and the sugar in DNA is 2 -deoxy-ribose. (The prefix 2 -deoxv indicates that oxygen is missing from the 2 position of ribose.) DNA contains four different amine bases, two substituted purines (adenine and guanine) and two substituted pyrimidines (cytosine and thymine). Adenine, guanine, and cytosine also occur in RNA, but thymine is replaced in RNA by a closely related pyrimidine base called uracil. 

A with T the purine adenine (A) always pairs with the pyrimidine thymine (T)... 

Fludarabine is an analog of the purine adenine. It interferes with DNA polymerase to cause chain termination and inhibits transcription by its incorporation into RNA. Fludarabine is dephosphorylated rapidly and converted to 2-fluoro-Ara-AMP (2-FLAA), which enters the cells and is phosphorylated to 2-fluoro-Ara-ATP, which is cytotoxic. Fludarabine is converted rapidly to 2-FLAA. The pharmacokinetics of 2-FLAA... 

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. 

Such enzymes catalyse the condensation of specific compounds, accompanied by the breakdown of a pyrophosphate bond in adenosine triphosphate (10.64). Adenosine is the condensation product of a pentose (D-ribofuranose) and a purine (adenine). Scheme 10.15 shows the action of glutamine synthetase on a mixture of L-glutamic acid (10.65) and... 

A sequence, in general, is the relative order of base pairs, whether in a fragment of a protein, DNA, a gene, a chromosome, or an entire genome. DNA is composed of two antiparallel strands of deoxynucleotides held together by hydrogen bonds between purine (adenine, A and guanine, G) and pyrimidine (thymidine, T uracil, U and cytosine, C) bases. 

Nucleotide A subunit of DNA or RNA consisting of a purine (adenine and guanine) or a pyrimidine base [thymine (DNA only), uracil (RNA only) and cytosine], a phosphate molecule, and a sugar molecule (deoxyribose in DNA and ribose in RNA). 

Figure 9.13 A glycosylamine. Adenosine is a nucleoside and is an example of a glycosylamine in which the nitrogen atom of the purine, adenine, is linked directly to carbon 1 of /3-D-ribofuranose.

The electrochemical reductions of purine, adenine, and related compounds involve two consecutive steps as shown in Scheme 138 for adenine [251]. 

After the nucleic acid purines adenine and guanine, the next most prominent purine in our everyday lives is probably caffeine. Caffeine, in the form of beverages such as tea, coffee, and cola, is one of the most widely consumed and socially accepted natural stimulants. Closely related structurally are theobromine and theophylline. Theobromine is a major constituent of cocoa, and related chocolate products. Caffeine is also used medicinally,... 

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... 

Our laboratory conducted the most extensive investigation of the 2,4,1-benzodiazaborines reported to date. We focused attention on l-hydroxy-lff-2,4,l-benzoxazaborine (50a), 1,2-dihydro-l-hydroxy-2,4,l-benzodiazaborine (50b), and 3-amino-l,2-dihydro-l-hydroxy-2,4,l-benzodiazaborine (50c) because their peripheries so closely matched the pyrimidine ring ones of the naturally occurring purines adenine, hypoxanthine, and guanine, respectively <94JA7597>. 

The similarity in the pyrimidine ring of pteridines and pterins, especially to the purines adenine and guanosine, undoubtedly makes them good templates for inhibitor design as these examples show. Another enzyme for which inhibition by pteridines has been established is xanthine oxidase <1999BBA387>. In this case, the limitation on structure for inhibitors in the pteridine series was that there should be no substituent on C-7 and that the pteridines should be fully conjugated. The best inhibitors (ICso 0.1 xM) were 6-formylpterin and 6-hydroxylumazine. 

Many biologically important heterocyclic compounds have fused (condensed) ring systems. In particular, the purines adenine and guanine are found in DNA (with cytosine, 5-methylcytosine, and thymine) and also in RNA (with cytosine and uracil). 

Compounds based on the purine structure are classified as purines. Adenine is one of the two purines found in DNA and RNA. The other is guanine. Adenine and guanine are called bases in reference to DNA and RNA. A nucleic acid base attached to ribose forms a ribonucleoside. Adenine combined with ribose produces the nucleoside adenosine. When an oxygen atom is removed from the second carbon of ribose, the sugar unit formed is... 

Purine. A heterocyclic ring structure with varying functional groups. The purines adenine and guanine are found in both DNA and RNA. 

Moorthy PN, Hayon E (1975) Free-radical intermediates produced from the one-electron reduction of purine, adenine and guanine derivatives in water. J Am Chem Soc 97 3345-3350 Mori M, Teshima S-l, Yoshimoto H, Fujita S-l, Taniguchi R, Hatta H, Nishimoto S-l (2001) OH Radical reaction of 5-substituted uracils pulse radiolysis and product studies of a common redox-ambivalent radical produced by elimination of the 5-substituents. J Phys Chem B 105 2070-2078 Morin B, Cadet J (1995) Chemical aspects of the benzophenone-photosensitized formation of two lysine - 2 -deoxyguanosine cross-links. J Am Chem Soc 117 12408-12415 Morita H, Kwiatkowski JS,TempczykA(1981) Electronic structures of uracil and its anions. Bull Chem Soc Jpn 54 1797-1801... 

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