Ribose-containing nucleotides

DNA contains all the cell s hereditary information. Upon cell division, each new cell receives a complete copy of its parents DNA. The sequence of the subunit nucleotides along the polymer chain holds this information. Nucleotides are made up of deoxyribose, phosphoric acid, and a purine or pyrimidine nitrogenous base. RNA is a polymer of ribose-containing nucleotides. Of the nitrogenous bases, adenine, guanine, and cytosine are... 

The interaction of borate and boronic acid with a number of ribose-containing nucleotides and cofactors such as NAD" ", NADH, adenosine triphosphate (ATP) and adenosine monophosphate (AMP) have been... 

Nucleic acids have two kinds of pentoses. The recurring deoxyribonucleotide units of DNA contain 2 -deoxy-D-ribose, and the ribonucleotide units of RNA contain D-ribose. In nucleotides, both types of pentoses are in their j3-furanose (closed five-membered ring) form. As Figure 8-3 shows, the pentose ring is not planar but occurs in one of a variety of conformations generally described as puckered. ... 

Assuming the existence of an RNA template, the polymerization of activated ribonucleotides into polymers containing 3, 5 -phosphodiester linkages proceeds readily. Using RNA homopolymers as templates, products of up to 50 bases in length have been observed,30 and when RNA heteropolymers are used as templates the reaction is faithful.31 These reactions can be catalyzed by a variety of metal ions,32 33 and seem to occur most easily with ribose-linked nucleotides.34 Short oligonucleotides can also serve as substrates for template-directed polymerization,35 36 and they... 

DNA contains the bases adenine (A), thymine (T), guanine (G), and cytosine (C). These bases are covalently attached to the deoxyribose phosphate to form nucleotides. The respective nucleotides are called deoxyadenylic acid (dA), deox)hhy-midylic acid (dT), deoxyguanylic acid (dG), and deoxycytidylic add (dC). The prefix "deoxy" indicates that the sugar is deoxyribose, rather than ribose. The word "acid" indicates that the ribose contains a covalently bound phosphoric acid group. 

Ribonucleic acid (RNA), like DNA, is a long unbranched polymer consisting of nucleotides joined by 3 -to-5 phosphodiester bonds (see Figure 4,3). The covalent structure of RNA differs from that of DNA in two respects. First, the sugar units in RNA are riboses rather than deoxyriboses. Ribose contains a 2 -hydroxyl group not present in deoxyribose. Second, one of the four major bases in RNA is uracil (U) instead of thymine (T). 

There is a complicated system of feedback inhibition for the production of purine-containing nucleotides. The final products, ATP and GTP, feed back to inhibit the first steps starting from ribose-5-phosphate. In addition, each intermediate, such as AMP or ADP, can also inhibit the first step. Also, each of the three forms for each nucleotide inhibit the committed reaction from IMP that eventually decides which purine nucleotide is made. 

Second Generation Antisense ONs. These contain nucleotides with alkyl modification at the 2 position of the ribose. 2 -0-methyl and 2 -0-methoxyethyl... 

Four important coenzymes contain nucleotides as part of their structures. We have already mentioned coenzyme A (for its structure, see page 312), which contains ADP as part of its structure. It is a biological acyl-transfer agent and plays a key role in fat metabolism. Nicotinamide adenine dinucleotide (NAD) is a coenzyme that dehydrogenates alcohols to aldehydes or ketones, or the reverse process It reduces carbonyl groups to alcohols. It consists of two nucleotides linked by the 5 hydroxyl group of each ribose unit. 

A nucleoside contains a base bonded to D-ribose or to 2 -deoxy-D-ribose. A nucleotide is a nucleoside with an OH group of the sugar bonded to phosphoric acid by an ester linkage. 

A novel nucleotide, dTTP-a-CHj [-0-P (=0)(CH3)0-ribose], containing an a-phosphorus as the methyl phosphonate is a substrate (17). TDTase incorporates the nucleotide only one or two times and also incorporates the chain-terminating 3 -fluoro-ddiT P-a-CHj (18). The methyl phosphonate-linked oligomers are resis-... 

A chain of nucleotides containing only deoxyribose as the sugar is a DNA. Similarly, RNA possesses chains nucleotides having only ribose as the sugar and is therefore a ribonucleic acid. 

Posttranslational modification of preformed polynucleotides can generate additional bases such as pseudouridine, in which D-ribose is linked to C-5 of uracil by a carbon-to-carbon bond rather than by a P-N-glycosidic bond. The nucleotide pseudouridylic acid T arises by rearrangement of UMP of a preformed tRNA. Similarly, methylation by S-adenosylmethionine of a UMP of preformed tRNA forms TMP (thymidine monophosphate), which contains ribose rather than de-oxyribose. 

The UMP nucleotide contains uracil, ribose, and one phosphate group. The structure of uracil and the hydrogen eliminated during the condensation appear in Figure 13-22. Here are the component parts, drawn in position to eliminate water molecules and link ... 

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). 

---