Nucleic adenine

Volkov, S.N. Conformational transitions and the mechanism of transmission of long-range effects in DNA. Preprint ITP-88-12E, Kiev (1988) 22 Krumhansl, J.A., Alexander, D.M. Nonlinear dynamics and conformational exitations in biomolecular materials. In Structure and dynamics nucleic acids and proteins. (Clementi, E., Sarma, R.H., eds) Adenine Press, New York (1983) 61-80... 

Any one nucleotide, the basic building block of a nucleic acid, is derived from a molecule of phosphoric acid, a molecule of a sugar (either deoxyribose or ribose), and a molecule of one of five nitrogen compounds (bases) cytosine (C), thymine (T), adenine (A), guanine (G), uracil (U). 

Cellular Protein Biosynthesis. The process of cellular protein biosynthesis is virtually the same in all organisms. The information which defines the amino acid sequence of a protein is encoded by its corresponding sequence of DNA (the gene). The DNA is composed of two strands of polynucleotides, each comprising some arrangement (sequence) of the four nucleotide building blocks of the nucleic acids adenine (A), thymine (T),... 

The sugars are typically ribose (ribonucleic acids, RNA), or 2-deoxyribose (deoxyribonucleic acids, DNA). There are five common bases in nucleic acids adenine (A) thymine (T) uracil (U) cytosine (C) and guanine (G). DNA polymers incorporate the four bases. A, T, C, and G, and RNA, the set A, U, C, and G. 

After 1900, genetic research—but not research on nucleic acids—blossomed. Nucleic acids were difficult to work with, hard to purify, and, even though they were present in all cells, did not seem to be very interesting. Early analyses, later shown to be inconect, were interpreted to mean that nucleic acids were polymers consisting of repeats of some sequence of adenine (A), thymine (T), guanine (G), and cytosine (C) in a 1 1 1 1 ratio. Nucleic acids didn t seem to offer a rich enough alphabet from which to build a genetic dictionary. Most workers in the field believed proteins to be better-candidates. 

Adenine (6-amino purine) and guanine (2-amino-6-oxy purine), the two common purines, are found in both DNA and RNA (Figure 11.4). Other naturally occurring purine derivatives include hypoxanthlne, xanthine, and uric acid (Figure 11.5). Flypoxanthine and xanthine are found only rarely as constituents of nucleic acids. Uric acid, the most oxidized state for a purine derivative, is never found in nucleic acids. 

Another property of pyrimidines and purines is their strong absorbance of ultraviolet (UV) light, which is also a consequence of the aromaticity of their heterocyclic ring structures. Figure 11.8 shows characteristic absorption spectra of several of the common bases of nucleic acids—adenine, uracil, cytosine, and guanine—in their nucleotide forms AMP, UMP, CMP, and GMP (see Section 11.4). This property is particularly useful in quantitative and qualitative analysis of nucleotides and nucleic acids. 

As is well-known, nucleic acids consist of a polymeric chain of monotonously reiterating molecules of phosphoric acid and a sugar. In ribonucleic acid, the sugar component is represented by n-ribose, in deoxyribonucleic acid by D-2-deoxyribose. To this chain pyrimidine and purine derivatives are bound at the sugar moieties, these derivatives being conventionally, even if inaccurately, termed as pyrimidine and purine bases. The bases in question are uracil (in ribonucleic acids) or thymine (in deoxyribonucleic acids), cytosine, adenine, guanine, in some cases 5-methylcytosine and 5-hydroxymethylcyto-sine. In addition to these, a number of the so-called odd bases occurring in small amounts in some ribonucleic acid fractions have been isolated. 

Amine bases in nucleic acids can react with alkylating agents in typical Sjsj2 reactions. Look at the following electrostatic potential maps, and tell which is the better nucleophile, guanine or adenine. The reactive positions in each are indicated. 

Kinoshita, Imoto etal.11 14) synthesized other anionic models, 5 (APVP), CPVP, UPVP, TPVA, HPVA, THPVA, and 6 (AMPPVA), by the polymer reaction of N-eoupled(2-dihydrogenphosphate)-ethylderivatives of nucleic acid bases (or adenosine-5 -phosphate, AMP) with polyvinylaleohol. A, C, U, T, H, and TH denote adenine, cytosine, uracil, thymin, hypoxanthine, and theophylline, respectively. The authors reported the apparent hypochromities of 3 to 16% for many kinds of mixtures of the models and DNA or RNA, as compiled in Table 1. However, for the mixtures APVA + RNA, HPVA + RNA HPVA + DNA, THPVA + RNA, CPVA + DNA and CPVA + RNA, no hypochromicity was detected. 

Nucleic acids are anionic under the neutral conditions. Thus, the syntheses of model compounds of the opposite charge are interesting for the discussion of electrostatic contributions in specific interactions of nucleic acids. We have tried to synthesize cationic models by the Menschutkin reaction of poly-4-vinylpyridine with 9-(2-chlo-roethyl)adenine, l-(2-chloroethyl)thymine, and 7-(2-chloroethyl)theophylline15,16 The obtained polymers are poly l-[2-(adenin-9-yl)ethyl]-4-pyridinioethylene chloride 7(APVP), poly l-[2-(thymin-l-yl)ethyl]-4-pyridinioethylene chloride 8 (TPVP), and poly l-[2-(theophyllin-7-yl)ethyl]-4-pyridiniothylene chloride 9 (THPVP), respectively. 

In relation to separation of nucleotides, Hoffman61 found that adenine nucleotides interacted most strongly with cycloheptaamylose, presumably by inclusion of the base within the cavity of cyclodextrin. When epichlorohydrin-cross-linked cycloheptaamylose gel was used as a stationary phase for nucleic acid chromatography, adenine-containing compounds were retarded most strongly. 

Small quantities of additional purines and pyrimidines occur in DNA and RNAs. Examples include 5-methyl-cytosine of bacterial and human DNA, 5-hydroxy-methylcytosine of bacterial and viral nucleic acids, and mono- and di-N-methylated adenine and guanine of... 

Purines — These molecules have basic skeletons of purine heterocycles. Adenine and guanine, intrinsic components of nucleic acids, are also ubiquitous molecules. Related molecules are isoguanine, xanthine, and uric acid. 

Seasonal variations in the metabolic fate of adenine nucleotides prelabelled with [8—1-4C] adenine were examined in leaf disks prepared at 1-month intervals, over the course of 1 year, from the shoots of tea plants (Camellia sinensis L. cv. Yabukita) which were growing under natural field conditions by Fujimori et al.33 Incorporation of radioactivity into nucleic acids and catabolites of purine nucleotides was found throughout the experimental period, but incorporation into theobromine and caffeine was found only in the young leaves harvested from April to June. Methy-lation of xanthosine, 7-methylxanthine, and theobromine was catalyzed by gel-filtered leaf extracts from young shoots (April to June), but the reactions could not be detected in extracts from leaves in which no synthesis of caffeine was observed in vivo. By contrast, the activity of 5-phosphoribosyl-1-pyrophosphate synthetase was still found in leaves harvested in July and August. 

Since nucleic acids and enzymes play such a large role in chromosome replication during mitosis, a considerable amount of research has been conducted in this area to control viruses. On the molecular level, analogues of nucleic acids are capable of forming complexes with adenine, cytosine, uracil, thymine, and guanine. Through complexation, these nucleic acid analogues are potential inhibitors of biosyntheses that require nucleic acids as templates. 

The most important product of the hexose monophosphate pathway is reduced nicotinamide-adenine dinucleotide phosphate (NADPH). Another important function of this pathway is to provide ribose for nucleic acid synthesis. In the red blood cell, NADPH is a major reducing agent and serves as a cofactor in the reduction of oxidized glutathione, thereby protecting the cell against oxidative attack. In the syndromes associated with dysfunction of the hexose monophosphate pathway and glutathione metabolism and synthesis, oxidative denaturation of hemoglobin is the major contributor to the hemolytic process. 

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. 

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