Anion, pyrophosphate

The situation with phosphoric anhydrides is similar. The phosphorus atoms of the pyrophosphate anion are electron-withdrawing and destabilize PPj with respect to its hydrolysis products. Furthermore, the reverse reaction, reformation of the anhydride bond from the two anionic products, requires that the electrostatic repulsion between these anions be overcome (see following). 

The reaction proceeds via attack by a phosphate oxygen of glucose-l-phosphate on the a-phosphorus of UTP, with departure of the pyrophosphate anion. The reaction is a reversible one, but—as is the case for many biosynthetic reactions —it is driven forward by subsequent hydrolysis of pyrophosphate ... 

Other important biological manifestations of phosphorus include the pyrophosphate anion, P207 or PPi, and inositol 1,4,5-triphosphate, IP3. Pyrophosphate anions can arise through the following reaction ... 

Pyrophosphate (also known as diphosphate) or 1 207" . The conjugate base of pyrophosphoric acid (or, diphosphoric acid), H4P2O7 (having pi a values, at 25°C, of 0.85, 1.96, 6.60, and 9.41). Crystals of tetrasodium pyrophosphate (mp = 988°C) are very soluble in water. The pyrophosphate anion hydrolyzes to orthophosphate however, the rate of hydrolysis is much slower than that of pyrophosphoric acid. The hydrated form of tetrasodium pyrophosphate exhibits a shght degree of efflorescence. 

Quinaxoline-containing monomer 14 was electrochemically polymerized to yield a polythiophene that changed from a yellow to orange color upon the addition of fluoride or pyrophosphate anions (Aldakov and Anzenbacher 2004). Analyte binding could be detected spectroscopically and electrochemically. 

The structure of the active component, manganese pyrophosphate, has been reported in the literature (24). It is layer like with planes of octahedrally coordinated Hn ions being separated by planes of pyrophosphate anions (P20y ). Examination of models of this compound gave calculated Hn-Hn thru space distances of 3.26 and 3.45 angstroms, a metal-metal distance close to that found for binuclear dibridged peroxo- and superoxo- complexes of cobalt ( ). 

Not only hydrogen ions are relatively strongly bound to the pyrophosphate anion. Thus, for example, the salt BasPaCh, which is not easily soluble in water, is brought into solution by an excess of pyrophosphate. Furthermore, electrometric and conductimetric studies have established (16,I4O) that most polyvalent cations and also the T1+ ion (265) are bound in complexes of various sorts. Quantitative studies show that the formation constants for the calcium complexes of the P2O74- ion have values which are about a power of ten smaller than those for the corresponding complexes of the triphosphate anion (I48). (For data, see Section IV.B.S.)... 

C. This dependence is attributed to the differing sensitivity to hydrolysis of the various pyrophosphate anions (44, 60) which can be differentiated by their infrared spectra (208). 

Transketolase is one of several enzymes that catalyze reactions of intermediates with a negative charge on what was initially a carbonyl carbon atom. All such enzymes require thiamine pyrophosphate (TPP) as a cofactor (chapter 10). The transketolase reaction is initiated by addition of the thiamine pyrophosphate anion to the carbonyl of a ketose phosphate, for example xylulose-5-phosphate (fig. 12.33). The adduct next undergoes an aldol-like cleavage. Carbons 1 and 2 are retained on the enzyme in the form of the glycol-aldehyde derivative of TPP. This intermediate condenses with the carbonyl of another aldolase. If the reactants are xylulose-5-phosphate and ribose-5-phosphate, the products are glyceraldehyde-3-phosphate and the seven-carbon ketose, sedoheptulose-7-phosphate (see fig. 12.33). 

Extended dipyrrolyl quinoxalines 31-34 were synthesized by Anzenbacher et al. [31] and displayed strong selectivity for F" and pyrophosphate anions (HP207 ). Addition of these anions to the solutions of 31-34 in CH2C12 in all cases resulted in the decrease of absorptions at 400-450 nm concurrent with the appearance of strong bands around 500-550 nm. 

The P207 dimer pyrophosphate anion consists of two P04 units sharing one oxygen atom that is called the bridging oxygen Ob. The other oxygen atoms are called non-bridging or terminal (Ot). Theoretical XPS valence band spectra based on two different cluster models are shown and compared to the respective... 

A synthetic method for the synthesis of 8-vinyl adenosine 5 -di and triphosphate (243a b) has been developed. This procedure eliminates unwanted depurination side-reactions under acidic conditions by introduction of acetyl protecting groups at the 2 and 3 positions of adenosine. The di- and triphosphate esters were obtained by treatment of the adenylic acid with phosphate and pyrophosphate anions.6,6-Bicyclic pyiimidopyridazin-7-one nucleoside triphosphate (244) was synthesized by nucleophilic ring-opening and rearrangement of a furanopyridine nucleoside in the presence of anhydrous hydrazine. 

Formation of succinic semialdehyde-thiamine pyrophosphate anion and Michael... 

Formation of succinic semialdehyde-thiamine pyrophosphate anion and Michael addition to isochorismate (compound (5) + (13) (14))... 

Yoon and co-workers have reported a series of mono- and bis-functionalized anthracenes and described their colorimetric and fluorescent properties for the sensing of both fluoride and pyrophosphate anions. The authors appended either phenylurea or p-nitrophenylurea groups through the l-position (for the mono-functionahzed derivatives 21a and 21b) and the 1- and 8-position (for the bis-functionaUzed derivative 22a and 22b) of the anthracene [34]. 

The biogeneses of cyclic and polycyclic terpenes are usually assumed to involve intermediate carbenium ions, but evidence for this in vivo was given only in some specific cases. In the simple case of monocyclic monoterpenes such as limonene the allylic cation remaining after separation of the pyrophosphate anion cyclizes to a cyclohexyl cation which is deprotonated to (/ )- or (5)-limonene. 

The non-classical version of the intermediate carbenium ion (also referred to as a carbonium ion) resulting upon dissociation of the pyrophosphate anion from famesylpyrophosphate explains the cyclization to several cyclic carbenium ions as demonstrated for some sesquiterpenes (Fig. 3). Additional diversity arises from 1,2-hydride and 1,2-alkyl shifts (Wagner-Meerweest rearrangements) sbA sigmatropic reactions (COPE rearrangements) on the one hand, and on the other hand from the formation of diastereomers and enantiomers provided that the cyclizations generate new asymmetric carbon atoms (Fig. 3)... 

The biogenesis of pimarane, the parent compound of many polycyclic diterpenes, is assumed to arise from Ko-geranylgeranylpyrophosphate After dissociation of the pyrophosphate anion, the remaining acyclic allylic cation undergoes a 1,3-sigmatropic hydrogen shift and thereby cyclizes to a monocyclic carbenium ion which, itself, isomerizes to the ionic precursor of the pimarane skeleton. 

Mash, E. A., G. M. Gurria, and C. D. Poulter, Famesylpyrophos-phate synthetase. Evidence for a rigid geranyl cation-pyrophosphate anion pair, J. Am. Chem. Soc., 103, 3927-3929 (1981). 

Inorganic mono or dihydrogen phosphate anions are sometimes represented as Pi and acid pyrophosphate anions as PPi. 

The rate and route of hydrolysis of P-O-P linkages in inorganic condensed phosphates, although enzyme sensitive, is usually influenced mostly by factors such as pH, temperature and concentration. The simplest hydrolysis reaction is that of pyrophosphate anions (3.95). 

Crystalline pyrophosphates show a range of P/O/P angles between 120% and 180% moreover, the central P-O-(P) distance is usually a little greater than the P-0 terminal (5.122). Pyrophosphate anions can exhibit different configurations in the solid state. These arise on rotation of the tetrahedra about the connecting P-O-P linkages (Figure 5.14). 

Crystalline alkali metal salts Li4P20g -4H20, Na4P20g I8H2O and K4P20g have been reported [22]. Sparingly soluble Ba, Pb and Zn salts can be obtained by double decomposition from an aqueous solution of the potassium salt. The perdiphosphate anion, like the pyrophosphate anion, will form complexes stable at room temperature in neutral or basic solution, but under acid conditions, rapid hydrolysis takes place to yield permonophosphoric acid. 

Pyrophosphates such as Na2H2P207 can be used to counteract the blackening of raw potato or apple juice. This is a deterioration which arises from the oxidation of diphenolic compounds in the presence of heavy metal ions. The latter are removed by complexing with the pyrophosphate anions. 

The pyrophosphate anion can capture an electron to produce the unsymmetrical radical... 

A restriction on spin-spin splitting is that equivalent nuclei do not couple with each other. The pyrophosphate anion (14.24a) shows only a single P line peak, and phosphorus NMR chanical shifts can be quite useful in this way to demonstrate the equivalence of different P atoms in symmetrical molecules. 

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