Isotope-selective technique

Complementary to other methods that constimte a basis for the investigation of molecular dynamics (Raman scattering, infrared absorption, and neutron scattering), NIS is a site- and isotope-selective technique. It yields the partial density of vibrational states (PDOS). The word partial refers to the selection of molecular vibrations in which the Mossbauer isotope takes part. The first NIS measurements were performed in 1995 to constitute the method and to investigate the PDOS of... 

In summary, NIS provides an excellent tool for the study of the vibrational properties of iron centers in proteins. In spectroscopies like Resonance Raman and IR, the vibrational states of the iron centers are masked by those of the protein backbone. A specific feature of NIS is that it is an isotope-selective technique (e.g., for Fe). Its focus is on the metal-ligand bond stretching and bending vibrations which exhibit the most prominent contributions to the mean square displacement of the metal atom. 

Benzoates. The selective debenzoylation of sucrose octabenzoate [2425-84-5] using isopropylamine in the absence of solvents caused deacylation in the furanose ring to give 2,3,4,6,1/3/6 -hepta- and 2,3,4,6,1/6 -hexa-O-benzoyl-sucroses in 24.1 and 25.4% after 21 and 80 hours, respectively (54). The unambiguous assignment of partially benzoylated sucrose derivatives was accompHshed by specific isotopic labeling techniques (54). Identification of any benzoylated sucrose derivative can thus be achieved by comparison of its C-nmr carbonyl carbon resonances with those of the assigned octabenzoate derivative after benzoylation with 10 atom % benzoyl—carbonyl chloride in pyridine. 

NRA is an effective technique for measuring depth profiles of light elements in solids. Its sensitivity and isotope-selective character make it ideal for isotopic tracer experiments. NRA is also capable of profiling hydrogen, which can be characterized by only a few other analytical techniques. Future prospects include further application of the technique in a wider range of fields, three-dimensional mapping with microbeams, and development of an easily accessible and comprehensive compilation of reaction cross sections. 

A dual isotope labeling technique [85] has been used to measure membrane permeability in plant cells, based on the selective permeabiHty of the membranes of living cells to tritiated water and carbon-14 labeled mannitol. Kieran [29] showed that the results of the dual isotope labeling and Evan s Blue staining methods correlated well as indicators of cell viability however, the latter was preferable in terms of reagent cost and ease of analysis. 

Braden B, Haisch M, Duan LP et al (1994) Clinically feasible stable-isotope technique at a reasonable price - analysis of 13C02/12C02-abundance in breath samples with a new isotope selective nondispersive infrared spectrometer. Zeitschrift fur Gastroenterologie 32(12) 675-678... 

The reverse isotope dilution technique can be applied for accurate determination of the Mg contents in a sample, sample, on applying equation 7, by measuring the isotope ratio of a selected pair of stable isotopes, in a weighed mixmre of the sample with an isotopically enriched CRM. The average atomic masses m and the isotopic ratios R of Mg in the enriched CRM and in nature are known. The method was applied for determination of Mg in plant material using a CRM isotopically enriched with Mg, measuring with an ICP/MS instruments. ... 

Am with a half-life of ti = 432 a has to be determined in waste and environmental samples by mass spectrometry. The determination of 238Pu (ti 88 a) at the trace level is difficult in the presence of uranium due to isobaric interference with 238 U+ in mass spectra measured by ICP-MS or LA-ICP-MS. Therefore the application of a sensitive and selective technique such as RIMS or AMS is advantageous. The determination of 238Pu for plutonium isotope analysis in irradiated... 

Other mass spectrometric techniques such as RIMS and AMS possess high isotope selectivity for extreme ultratrace and isotope analysis of, in particular, radiotoxic isotopes ( C, "Ca, Sr, Tc, Pb, U and plutonium isotopes) in the environment, in cosmochemistry, radiodating, nutrition and biomedical research. RIMS has become as an nltrasensitive and selective analytical technique for the determination of extremely low isotope abundances. In spite of the excellent analytical features of RIMS (detection limit for isotopes 10 atoms per sample) and exciting applications for the determination of extremely low abundances and isotope ratios of long-lived radionuclides, such as all plutonium isotopes (including Pu), U or " Ca, but no commercial instrument is available on the analytical market. 

As a highly selective and very sensitive isotopic analytical technique, accelerator mass spectrometry (AMS) is able to determine radionuchdes ( °Be, C1, A1, Tc, Np, Pu... 

MS or LA-ICP-MS. Therefore the application of a sensitive and selective technique such as RIMS or AMS is advantageous. The determination of Pu for plutonium isotope analysis in irradiated... 

Imai, T., Guto, H., Matsumura, H., and Yasuda, S., 1999, Determination of the distribution and reaction of polysaccharides in wood cell-walls by the isotope tracer techniques. VIII. Selective radiolabeling of xylan in mature cell walls of magnolia Magnolia kobus DC) and visualization of its distribution by microautoradiography. J. Wood Sci. 45 164-169. 

This isotope cluster technique [61] was used to facilitate the identification of omeprazole metabolites in rat urine [62]. Omeprazole is a selective inhibitor of gastric acid secretion and is used in the treatment of acid-related disorders. A 1 1 mixture of natural [ 5]-omeprazole and labelled [ S]-omeprazole was administered to a rat. More than 40 related substances were found in the LC-MS chromatogram of the rat urine sample. All these compounds were related to omeprazole, because they showed the expected isotopic cluster (two peaks of similar height two m/z units apart). The summed background-subtracted mass spectrum of the entire sample is shown in Figure 10.9. This spectrum represents a good overview of the metabohc pattern and the metabolic routes omeprazole is involved in. 

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