Nucleic phosphate groups

Nucleic Acids. Phosphoms is an essential component of nucleic acids, polymers consisting of chains of nucleosides, a sugar plus a nitrogenous base, and joined by phosphate groups (43,44). In ribonucleic acid (RNA), the sugar is D-ribose in deoxyribonucleic acids (DNA), the sugar is 2-deoxy-D-ribose. 

Just as proteins are biopolymers made of amino acids, nucleic acids are biopolv-mers made of nucleotides joined together to form a long chain. Each nucleotide is composed of a nucleoside bonded to a phosphate group, and each nucleoside is composed of an aldopentose sugar linked through its anomeric carbon to the nitrogen atom of a heterocyclic purine or pyrimidine base. 

The DNA monomers are each completed by a phosphate group, —O—P032, covalently bonded to carbon atom 5 of the ribose unit to give a compound called a nucleotide (28). Because there are four possible nucleoside monomers (one for each base), there are four possible nucleotides in each type of nucleic acid. 

A nucleic acid polymer contains nucleotide chains in which the phosphate group of one nucleotide links to the sugar ring of a second. The resulting backbone is an alternating sequence of sugars and phosphates, as shown in... 

Certain kinds of metal ions bind to the DNA double strands by an electrostatic interaction with the phosphate group(s) or by complex formation with the sugar moiety or the nucleic... 

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. 

The nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), which carry embedded in their complex molecules the genetic information that characterizes every organism, are found in virtually all living cells. Their molecules are very large and complex biopolymers made up basically of monomeric units known as nucleotides. Thus DNA and RNA are said to be polynucleotides. The nucleotides are made up of three bonded (linked) components a sugar, a nitrogenous base, and one or more phosphate groups ... 

However, there are particular sites that can be modified on the bases, sugars, or phosphate groups of nucleic acids to produce derivatives able to couple with a second molecule. The chemistry is almost entirely unique to DNA and RNA work, but once mastered, the process of conjugation can be done with the same ease as with protein molecules. 

To modify the unique chemical groups on nucleic acids, novel methods have been developed that allow derivatization through discrete sites on the available bases, sugars, or phosphate groups (see Chapter 1, Section 3 for a discussion of RNA and DNA structure). These chemical methods can be used to add a functional group or a label to an individual nucleotide or to one or more sites in oligonucleotide probes or full-sized DNA or RNA polymers. 

Three types of monomers found in DNA, a nucleic acid, are the phosphate group, the deoxyribose group and a base. These are illustrated by... 

The nucleotides of RNA and DNA consist of three components a carbohydrate, a phosphate group and an organic nitrogenous base. There are two types of carbohydrate molecule in nucleic acids, both of which are D-pentoses, i.e. contain five carbon atoms. The carbohydrate in RNA is ribose, while DNA contains deoxyribose, which has a hydrogen atom instead of a hydroxyl group attached to the carbon in the 2 position (Figure 13.1). 

In ion-exchange chromatography nucleic acids are separated on the basis of the difference in charge. Each nucleic acid has a different net charge based on the number of phosphate groups in the molecule (base length) and the respective charges on the bases (base composition). The latter effect is relatively minor and so separation depends almost exclusively on size. Separation... 

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