Orthophosphate diester

Some of the more readily mineralised forms of P in a soil development sequence were recently identified by a P-nmr technique . Orthophosphate diesters, including phospholipids, and phosphonates, but not orthophosphate monoesters, appeared able to supply plant-available P in these mainly undisturbed New Zealand tussock grassland ecosystems, given soil and climatic conditions favourable to P mineralisation. Similarly, orthophosphate diesters were more readily mineralised than monoesters in an old grassland soil after 21 y of bare fallowing, because the diesters declined sharply during this period. ... 

Figure 11.2 Dominant groups of P found in DOP (phosphonates, phosphate monoesters, orthophosphate, phosphate diesters, pyrophosphates, and tri- and tetrapolyphosphates) in oceanic waters. (Modified from Kolowith et al. 2001.)...

Although the characterization of DOP in rivers and estuaries has been largely ignored, some work in the Mississippi River indicated that the composition of SNP primarily consisted of diester and monoester phosphates, phosphonates, orthophosphates, and/or tri- and tetrapolyphosphates. 

Many organisms can store orthophosphate or polyphosphates. In plants, inositol hexaphos-phate (IHP) can form a major storage compound for phosphorus, particularly in seeds. Although relatively low in concentration, diesters may contribute to short-term bioavail-able pool more than monoesters. Compared to monoesters, diesters are more accessible to microbial attack. This fraction was shown to be rapidly made available to plants. 

Nuclear magnetic resonance, especially NMR, offers a powerful means of characterizing and identifying individual phosphorus species in soils and sediments. In the case of waters, there is usually the need for preconcentration, and interferences may arise because of the corresponding increase in concentration of paramagnetic substances. However, if these difficulties are resolved, NMR provides a qualitative means of detecting the presence of functionally different phosphorus groups, such as phosphonates, orthophosphates, orthophosphate mono-and diesters, and pyrophosphates, within a sample. 

Figure 22 shows the pho hate profiles of freeze-dried saliva resuspended in a buffer solution. The top spectrum was obtained from a patient with a history of dental caries and relatively good oral hygenic habits. The principal signal arises from salivary inorganic orthophosphate. The other resonances arise from various phosphomono- and diesters. The monoester resonance band appears at 3.95 ppm and corresponds to approximately 43% of the... 

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