Phosphorylation nucleoside hydroxyls

Phosphorus oxide chloride trimethyl phosphate Preferential phosphorylation of nucleoside hydroxyls... 

Acetylation of hydroxyl groups and esterification of carboxyl groups have been observed ia a limited number of cases but, ia geaeral, have ao preparative advantage over chemical methods. By comparison, phosphorylation has been useful ia the preparatioa of modified purine and pyrimidine mononucleotides from their corresponding nucleosides, eg, 6-thioguanosiae [85-31-4] (51) (97). 

Spleen exonuclease is active on the 5 -OH oligonucleotides of both the ribo and the deoxyribo series. These are sequentially split from the 5 -OH end with formation of 3 -mononucleotides. It has been suggested that an enzyme-product intermediate may exist in the form of nucleoside-3 -phosphoryl-enzyme complex (3) since transfer of nucleoside-3 -phosphate to available 5 -hydroxyl functions (or other alcoholic functions) occurs at high substrate (or acceptor) concentrations 15, 18). 

Structures of three common ribonucleotides (a) and four common deoxyribonucleotides (b). See Table 23.1 for alternative names and for names of the corresponding bases and nucleosides. The ribonucleotides contain a ribose sugar, whereas the deoxyribonucleotides have a deoxyribose that lacks a hydroxyl group at C-2 of the pentose. In all cases the phosphoryl group is attached... 

Phosphorylation. This reagent selectively phosphorylates the terminal 5 -hydroxyl group of nucleosides, even in the presence of a 3 -hydroxyl group. The... 

Nucleotides are nucleosides that have been phosphorylated on the 5 -hydroxyl group. One, two, or three phosphates can be added. Nucleotides are generally named by appending monophosphate, diphosphate, or triphosphate to the end of the name of the corresponding nucleoside, and the names are typically abbreviated. The suffixes -MP, -DP, and -TP correspond to mono-, di-, and triphosphate, respectively. Examples of 2 -deoxyadenosine 5 -diphosphate or ADP (6.13) and uridine 5 -monophosphate or UMP (6.14) are shown in Figure 6.5. 

DNA polymerases catalyze DNA synthesis in a template-directed manner (Box 16). For most known DNA polymerases a short DNA strand hybridized to the template strand is required to serve as a primer for initiation of DNA synthesis. Nascent DNA synthesis is promoted by DNA polymerases by catalysis of nucleophilic attack of the 3 -hydroxyl group of the 3 -terminal nucleotide of the primer strand on the a-phosphate of an incoming nucleoside triphosphate (dNTP), leading to substitution of pyrophosphate. This phosphoryl transfer step is promoted by two magnesium ions that stabilize a pentacoordinated transition state by complex-ation of the phosphate groups and essential carboxylate moieties in the active site (Figure 4.1.1) [2],... 

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