Phosphorus relaxation times

Cade-Menun, B.J., Liu, C.W., Nunlist, R. and McColl, J.C. (2002) Soil and litter phosphorus-31 nuclear magnetic resonance spectroscopy extractants, metals and phosphorus relaxation times. Journal of Environmental Quality 31, 457 65. 

Section III establishes how the NOE method could be used to analyze the rotamer distribution about the a,S,e bonds (and to some extent, the bonds of the sugar ring), but that the method is not at all applicable to )ff,y-bond analysis in oligonucleotides. In this section, I show how it is possible to approach the p,y distribution problem by interpretation of phosphorus relaxation times, and I show how this method can be used in conjunction with the phosphorus chemical-shift correlations of Gorenstein (1981). 

First of all we have three problems where the structure is known. Here you are asked to calculate coupling constants between phosphorus and carbon or hydrogen (Problem 36) and relaxation times T for carbon nuclei (Problem 37) and phosphorus nuclei (Problems 38a and 38b). Note that the equation you will require for Tj calculations can be found in Fig. 10 on p. 19... 

Investigations on solid samples have been reported for a rather large variety of compounds generally using phosphorus resonance but in some cases proton, fluorine, boron and even 23Na resonances (1969 217) and relaxation time measurements have been used. Phosphides, and especially simple or mixed paramagnetic phosphides, have often been... 

The T relaxation agent increased the sensitivity of the NMR instrument by decreasing several of the mono- and diester phosphate relaxation times by factors of 2-5. In this way the delay time between scans was decreased (43). This change permits an increase in the number of scans observed per unit time. Although the presence of ferric ions creates the potential for precipitation of phosphorus-iron complexes, the addition of a large molar excess of ethylenediaminetetraacetate (EDTA) relative to ferric ions prevented precipitation, even over a large pH region (44). 

Using phosphorus and proton Tl data it was shown that the dipole-dipole mechanism is mainly responsible for relaxation of 31P in orthophosphorous acid. A pH dependence of the 31P relaxation was observed. The maxima in the plot of 31P relaxation times vs. pH were attributed to the presence of the individual ions PO4, HPOJ and H2PO " (Morgan and Van Wazer, 1975). The 31P relaxation in cyclic metaphosphates was shown to be independent of pH but sensitive to the counter-ion used in this study (Glonek et al., 1976). 

Relaxation, CIDNP, and N.Q.R.—Relaxation. Phosphorus-31 and carbon-13 relaxation times are reported for dimethyl methylphosphonate. The mobility of phosphazene polymers has been studied using P spin-lattice relaxation parameters. The structure and mobility of polycrystalline nitrilotrimethylphos-phonic acid was estimated by line shape analysis. Molecular interactions of guanosine monophosphate and ATP have been studied through their relaxation properties. ... 

In nucleotides the positions of (spin = 1/2) resonances in NMR spectra depend on the charges on the phosphates and therefore change with pH. The intracellular pH in vivo can therefore be measured. Furthermore, atoms bound to phosphorus yield upfield shifts of the P signals, and the enzymatic reaction between O-labeled ADP and 0-labeled orf/io-phosphate in cells can be followed by P-NMR. A useful property of the nucleus (spin = 5/2) is the drastic shortening of P relaxation times leading to line broadening to the point where the P signal may virtually disappear. In this context, it is also of importance that... 

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