Nucleic acids phosphorus atoms

For various reasons, the generalizations mentioned above must be regarded as strictly provisional. Analyses utilizing formic acid indicate the presence of more than one phosphorus atom per purine or pyrimidine residue. This discrepancy, it is pointed out, could equally well result from an apparent deficiency of bases, due to error in the analytical technique.160 It is also necessary to consider that some nucleic acids are now known to contain more bases than was previously realized. Thus, 5-(hydroxymethyl)-cytosine is present in various viruses,181-182 and 5-methylcytosine occurs in various animal and plant deoxyribonucleic acids but is absent from those of microbial origin.17-160-1M- 184- 186 Certain microbial deoxyribonucleic acids also contain 6-methylaminopurine.186a Various bacteriophage deoxyribonucleic acids have been found to contain a component which is believed to consist of a D-glucoside186b of 5 -(hydroxymethyl)cytidylic acid. 

Radioactive isotopes provide a very convenient way of monitoring the fate or metabolism of compounds that contain the isotopes. When used in this way, the isotope is described as a tracer and compounds into which the radioactive atom has been introduced are said to be labelled or tagged. The labelled molecules need only comprise a very small proportion of the total amount of the unlabelled radioactive substance because they act in the same way as the non-radioactive substance but can be detected very much more easily. The varied applications of tracers in biochemistry range from studies of metabolism in whole animals or isolated organs to sensitive quantitative analytical techniques, such as radioimmunoassay. Phosphorus-32 is used in work with nucleic acids, particularly in DNA sequencing and hybridization techniques. In these instances the isotope is used as a means of visualizing DNA separations by autoradiographic techniques. 

Biomolecules are molecules found in living things. The major classes of biomolecules are proteins, carbohydrates, fats, and nucleic acids. All biomolecules contain carbon, hydrogen, and oxygen. Proteins also contain nitrogen and sometimes sulfur, and nucleic acids contain nitrogen and phosphorus. Other types of atoms may also be found in these compounds. 

Phosphorus is abundant on Earth, both as an element (the llth-most abundant atom in Earth s crust) and as phosphate. Meteorites hold a variety of phosphate-containing minerals and some phosphide minerals.10 Scientists at the University of Arizona have recently suggested that Fe3P, the mineral schreibersite, leads to the formation of phosphate and phosphite when corroded in water. Although phosphorylation of alcohols was not demonstrated, mechanistic considerations suggest that it should be possible. It is noteworthy that a clear prebiotic pathway for the chemical incorporation of phosphate into RNA or DNA has not been found. No nucleosides (nucleobases joined to sugars) have been reported from meteorites. Nor has evidence been found in any meteorite of the presence of nucleosides or nucleotides (nucleosides attached to phosphates). That suggests that nucleic acids were first formed as products of metabolism. 

Cleavage of nucleic acids refers to a reaction that results in the breakage of bonds in the phosphodiester backbone of a polynucleotide chain. There are two types of reactions resulting in the cleavage of either P-O or C-O bonds in the nucleic acid backboue (see Figure Id). Cleavage of the P-O bond occurs as a result of uucleophilic attack ou the phosphorus atom via either an intermolecular reaction with a H2O molecule hydrolysis) or an intramolecular reactiou involving the ribose 2 -OH transesterification). Of these two reactions, transesterification is specific to RNA (since DNA lacks a 2 -OH moiety) and can be catalyzed by many M- +... 

Phosphorus-32 is a commonly used radioactive nuclide in biochemical research, particularly in studies of nucleic acids. The half-life of phosphorus-32 is 14.3 days. What mass of phosphorus-32 is left from an original sample of 175 mg of Na332P04 after 35.0 days Assume that the atomic mass of 32P is 32.0. 

Phosphate. An ion consisting of a phosphorus atom and four oxygen atoms. Among other things, it is used in the constuction of nucleic acids. 

This substance belongs to the class of substances called the nucleic acids. A molecule of a nucleic acid consists of tens or hundreds of thousands of atoms of carbon, hydrogen, oxygen, nitrogen, and phosphorus joined together in a special way. 

The hydrolytic degradation of nucleic acids is catalyzed by nucleases, which are phosphodiesterases because they cleave the phosphodiesteric bonds hydrolytically (Linn et al., 1993). The cleavage can potentially occur on either side of the phosphorus atom, i.e. on the 3 -side (a) and the 5 -side (b) ... 

The most important elements to life are carbon, hydrogen, oxygen, and nitrogen — the CHON atoms — as well as sulfur and phosphorus. These elements are combined in hundreds of ways to construct the building blocks of life, such as carbohydrates, fats, proteins, and nucleic acids. 

A,group of three phosphate tetrahedra near the axis of the nucleic acid molecule. Oxygen atoms are indicated by full circles and phosphorus atoms by dashed circles. 

Hydrogen bonding is frequently crucial in determining the structure and properties of phosphorus compounds. In some of these compounds, however, the P atom itself may not be closely involved and the more important hydrogen bonds are formed by distant parts of the molecule. Notable examples of this situation are found in the nucleic acids, phosphoproteins and other bio polymers (Chapter 10). This section will be mostly concerned with relatively simple compounds where the P atom is separated by not more than a single atom from the participating H atom. 

Structure. The precise identification of the mode of linkage of the phosphate residues to adjacent ribose moieties in the nucleic acid chain has been established, primarily as a result of the development of ion-exchange 103) and paper 107) chromatographic methods. The basic structure for both types of nucleic acid is represented diagrammatically below (after Brown and Todd 160)) with the phosphorus atoms esterified at carbons... 

Besides phosphines and phosphites preferentially used as ligands in hydro-formylation, phosphoramidites have also been proposed. Phosphoramidites (sometimes also called phosphoroamidites) are a class of organic phosphorus compounds derived from phosphites in which the P-OR groups have been replaced by P-NR2 groups (Figure 2.31). Three different P-substituents produce a chiral (stereogenic) phosphorus atom. Phosphoramidites play a crucial role in the synthesis of nucleic acids [1] and have also been frequently considered as mono- or bidentate ligands in transition-metal catalysis [2]. 

Nucleic acids are formed by repeating units of three carbon atoms, (uie oxygen atom, a phosphorus atom and another oxygen atom. This backbone allows for the addition of pyrimidines and purines that form base pairs across two of these repeating units, resulting in the DNA double helix. 

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