Phosphate bridging

Nucleotides can be linked together into oligonucleotides through a phosphate bridge at the 5 position of one ribose unit and the 3 position of another. The purine bases, adenine and guanine, have two heterocyclic rings, while the pyrimidines cytosine, thymine, and uracil have one. The structure of adenosine monophosphate is shown in Figure 11. 

Analogues of Dinucleoside Di(Tri)phosphates and Oligonucleotides with a Di(Tri)phosphate Bridge... 

Corrano and co-workers have characterized phosphate ester species with a mixed donor heteroscorpionate tripod zinc species 452 Krebs and co-workers synthesized purple acid phosphatase mimics including a structurally characterized FemZnn phosphate bridged dimeric species.453... 

Cyclic nucleotides are like regular nucleotides (the things in DNA/RNA) except that the phosphate bridges the 3 and 5 hydroxyl group within... 

In 1984 Sargeson and coworkers [31] have detected that the dinuclear, p-nitrophenyl phosphate-bridged cobalt(III) complex 1 rapidly hydrolyzes in water at pH 10 and 25 °C (k = 2 x 10 2 s-1). Based on a detailed kinetic investigation the authors suggest intramolecular attack of coor-... 

Chin at al. have also demonstrated [52] notable bimetallic cooperativ-ity with the same substrate by the Cu(II) complex 34. The dimer complex is 26 times more active (at pH = 7 and T = 298 K) than the corresponding mononuclear species 35. Based on the crystal structure of the dibenzyl phosphate bridged complex, the authors have proposed double Lewis-acid activation, as in the preceding case. 

In Scheme 19, it is shown that the radical-cation 117 can either be attacked by the nucleophile water (reactions 182 and 183), or by the nucleophile phosphate (reactions 184 and 185) of the phosphoric ester that is still attached to the radical-cation. Because the formation of the radical-cations is fast, the phosphate-bridged radicals 120 and 121, formed in reactions 184 and 185, may be in equilibrium with 117 and with one another. They are probably unstable, and rapidly revert to 117 before they can undergo radical-radical reactions. 

Next, we examined the structural requirement for the confronting phosphate bridge in the methylation. The CPV system as described previously was employed. 

Phosphates bridge dinuclear metal centers in the active sites of some phosphoes-terases [1-3]. Dinuclear metal complexes should be able to provide double Lewis acid activation for hydrolyzing phosphates. To quantify double Lewis acid activation for cleaving phosphate diesters, we studied the reaction of 24 (Figure 6.16), which has... 

Table 5.3-1. Pt-Pt bond lengths in Pt2+ compounds. Sulfato and phosphate bridged compounds...

EXAFS studies of A. vinelandii bacterioferritin have shown that there are fewer Fe-Fe contacts in the mineral core than occur with native horse ferritin, and those that do occur are at a greater interatomic distance. Moreover, the EXAFS data showed that the core iron of bacterioferritin had 5 to 6 phosphorus atoms no more than 3.17 A distant, thus supporting a model for the core of an amorphous Fe(III)-phosphate complex in which some of the phosphate bridges Fe(III) ions and some of it is nonbridging. 

Photophysical properties are more thoroughly investigated with the phosphate-bridged complexes (112). Three phosphate-bridged com-... 

The fundamental units of nucleic acid, are nucleotides, nucleic acids, and polynucleotides in which the nucleotides are linked by phosphate bridges. Upon extensive heating in the presence of water (hydrolysis), nucleic acids yield amixture of purines and pyrimidines, (i-ribose or (i-deoxyribose, and phosphoric acid. Nucleic acids are subdivided into... 

Spermine was converted into the corresponding 0-(2-cyanoethyl)-(N,N-diisopro-pyOphosphoramidite block 223a for incorporation at the 5 -end of DNA. It was also coupled to the 2 of ara-U through a phosphate bridge, leading to the... 

Nucleic acid. A polymer of nucleotide subunits linked by phosphate bridges the nucleotides contain purine or pyrimidine bonded to ribose or deoxyribose (see chemical glossary). Nucleic acids form the basis for the genetic code in all living things. 

Another type of triply bonded species is represented by the purple and unusually air-stable, Csj[M02(HPO4)4(H2O)2], prepared by the reaction of K4MoClg.2H20 and CsCl in aqueous H3PO4. Here the cation has the dinuclear structure more commonly found in the divalent carboxylates (see below) and the M=M bond is supported by phosphate bridges. 

Glycoinositolphosphoryl ceramides (GIPCs) belong to a class of glycosphingolipids that are distinguished from the classical GSL already described in that they contain their sugar portion linked to ceramide via an inositol phosphate bridge. 

---