Measurement Of Phosphorus Content Research Articles

Measurement of phosphorus content in normal and osteomalacic rabbit bone by solid‐state 3D radial imaging

In osteomalacia decreased mineralization reduces the stiffness and static strength of bone. We hypothesized that hypomineralization in osteomalacic bone could be quantified by solid-state (31)P magnetic resonance imaging (SS-MRI). Hypomineralization was measured with a 3D radial imaging technique at 162 MHz (9.4T) in rabbit cortical bone of hypophosphatemic (HY) and normophosphatemic (NO) animals. The results were compared with those obtained by quantitative micro-CT (micro-CT) and (31)P solution NMR. 3D images of 277 microm isotropic voxel size were obtained in 1.7 hr with SNR approximately 9. Mineral content was lower in the HY relative to the NO group (SS-MRI: 9.48 +/- 0.4 vs. 11.15 +/- 0.31 phosphorus wet wt %, P < 0.0001; micro-CT: 1114.6 +/- 28.3 vs. 1175.7 +/- 23.5 mg mineral/cm(3); P = 0.003). T(1) was shorter in the HY group (47.2 +/- 3.5 vs. 54.1 +/- 2.7 s, P = 0.004), which suggests that relaxation occurs via a dipole-dipole (DD) mechanism involving exchangeable water protons, which are more prevalent in bone from osteomalacic animals.

Electron Spectroscopic Imaging of Chromatin

The analytical electron microscope technique called electron spectroscopic imaging (ESI) has a number of applications in the study of DNA:protein complexes. The method offers an intermediate level of spatial resolution forin vitrostructural studies of complexes that may be too large or heterogeneous to study by crystallography or magnetic resonance spectroscopy. An advantage of ESI is that the distribution of nucleic acids can be resolved in a nucleoprotein complex by mapping the element phosphorus, present at high levels in nucleic acid compared to protein. Measurements of phosphorus content together with mass determination allows estimates to be made of stoichiometric relationships of protein and nucleic acids in these complexes. ESI is also suited toin situstudies of nuclear structure. Mass-sensitive images combined with nitrogen and phosphorus maps can be used to distinguish nucleic acid components from nuclear structures that are predominantly protein based. Interactions between chromatin on the periphery of interchromatin granule clusters (IGC) with the protein substructure that connects the exterior of the IGC to its core can be studied with this technique. The method also avoids the use of heavy atom stains, agents required in conventional electron microscopy, that preclude the distinguishing of structures on the basis of their biochemical composition. The principles of ESI and technical aspects of the method are discussed.

Measurement of phosphorus content in silica layers

The phosphorus contents in the thin protective layers of P 2O 5 +SiO 2 on a number of silicon wafers were measured by using both PIXE and RBS techniques. Analyzing the two sets of data with the assumption of a uniform distribution of phosphorus in the oxide layer yielded an apparent discrepancy. It was found by computer simulation that the discrepancy could be removed by introducing nonconstant depth profiles of phosphorus in the analysis of the RBS data. A similar investigation also revealed that PIXE analysis was not sensitive to the phosphorus depth profile.

Phosphorus content of zooplankton from the Inland Sea of Japan

Measurements of phosphorus content were made for eleven species of copepods, two species of mysids, shrimps (including mysis stage) and chaetognaths, and one species ofNoctiluca, cirriped (naupliar stage) and crab (zoeal stage) from the Inland Sea of Japan. The body phosphorus content (P, inµg) is highly correlated to prosome length (L, inµm) for copepods, which is expressed as logP=2.90 ×logL−9.34. Mean phosphorus content expressed as percent of dry weight is 1.30% for copepods, 1.39% for mysids, 0.63% for a decapod shrimpAcetes japonicus, and 0.80% for chaetognaths.Noctiluca contains phosphorus of only 0.36%. The comparatively higher phosphorus content of suspension-feeding copepods may be related to the constant supply of phosphorus-rich phytoplankton in this region.

Collaborative Study of Automated Determination of Phosphorus in Meat Products

Abstract A collaborative study has been conducted on a modification of a previously reported automated method for phosphorus in meat products. Samples were dissolved in 1 + 1 sulfuric acid, cooled to room temperature, and presented to an AutoAnalyzer system. Digestion, dilution, and colorimetric measurement of phosphorus content were performed automatically. Six collaborators participated in the study, analyzing 8 different samples in duplicate. Results of the study were good, with an average range of 0.012% P, average standard deviation of ±0.0047, and average coefficient of variation of 2.32%. The method is recommended for adoption as official first action.