Biology isotope ratio measurements

Kumar N, Anderson RF, Mortlock RA, Froelich PN, Kubik P, Dittrich-Hannen B, Suter M (1995) Increased biological productivity and export production in the glacial southern ocean. Nature 378 675-680 Malinovsky D, Stenberg A, Rodushkin I, Andren H, Ingri J, Ohlander B, Baxter DC (2003) Performance of high resolution MC-ICP-MS for Fe isotope ratio measurements in sedimentary geologic materials. J Anal... 

Precise and accurate isotope analyses by mass spectrometry have attained growing importance in the last few years due to instrumental improvements with respect to sensitivity, detection limits, precision and accuracy.1 As mentioned before, because the isotope abundances of several elements are not constant and vary as a result of nuclear, biological, chemical, geochemical and physical processes, isotope ratio measurements are required for different research and application fields. Isotope ratio measurements are therefore necessary for elements with two or more isotopes for inves-... 

For direct isotope ratio measurements on solid samples, laser ablation ICP-MS (LA-ICP-MS) is applied to an increasing extent in geology, geochronology, biology and environmental research.6... 

An analytical procedure has been proposed for precise uranium isotope ratio measurements in a thin uranium layer on a biological surface by LA-ICP-MS using a cooled laser ablation chamber.125 One drop of uranium isotope standard reference materials NIST, 350, NIST 930, of our isotopic laboratory standard CCLU 500 (20p.l, U concentration 200 ng 1) and of uranium with natural isotopic pattern were deposited on the leaf surface and analyzed by LA-ICP-MS at well defined laser crater diameters of 10, 15, 25 and 50 p.m. A precision for measurements of isotope ratios in the range of 2.1-1.0% for 235U/238U in selected isotope standards was observed whereby the precision and the accuracy of isotope ratios compared to the non-cooled laser ablation chamber was improved.125... 

A similar set of experiments was performed to test our ability to precisely characterize strontium isotopes. For the archaeological chemistry of biological remains, strontium isotopes are useful for testing dietary hypotheses and for examining differences in place of birth and place of residence. To test the precision of strontium isotope ratio measurement using TOF-ICP-MS, we made glass fusion beads using NIST Strontium Carbonate Standard SRM 987 and... 

So far, in this chapter, individual techniques have been taken into account that have been used in the elucidation of the geographical origin of foods. It has been seen how trace element profiling and heavy isotope ratio measurements reflect the underlying geohydrological environment on which the food was produced. However, it has been shown how quite a wide range of chemical and biological... 

The principle of the isotope dilution analysis (IDA) is described in Section 6.4. Due to its advantages as a definitive and accurate analytical method for the determination of element concentration via isotope ratio measurements, IDA is being increasingly applied in mass spectrometry, especially in ICP-MS and LA-ICP-MS as one of the most frequently used techniques. For example, the isotope dilution technique is employed in species analysis in biological systems, " e.g., for the determination of mercury species in tuna material,or in aquatic systems. Further applications of the isotope dilution technique are the determination of selenomethionine in human blood serum by capillary HPLC-ICP (ORC) MS ° or sulfur speciation in gas oil, diesel or heating fuel by LA-ICP-MS. Evans and co-workers have reported on the high accuracy analysis of sulfur in diesel fuel by IDA. ICP-SFMS has been employed for Si species analysis in biological or clinical samples and... 

Using the criteria that abimdances are altered by at least twofold, 12 proteins of interest were identified in the nucleus and 15 in the plasma membrane of mitoxantrone-resistant MCF-7 cells. These are listed in Tables 13.1 and 13.2. Experimental variation in Table 13.1 is based on isotope ratio determinations of peptides from at least three gels, each from three separate cultures, thus incorporating both biological variability and experimental uncertainty. Experimental variation in Table 13.2 is based on isotope ratios measured for multiple peptides for each protein, from three separate cultures. 

Less expensive and less precise Instrumentation can be used for meaningful Isotope ratio measurements within biological sampling uncertainties However ... 

Mass Spectrometry with electron impact ionization (EIMS). Mass i ectrometers wit electron impact ionization are widely used in biomedical research, primarily for identification and quantitation of organic molecules. Adaptation of EIMS to isotope ratio measurements of minerals has, therefore, considerable appeal for investigators Interested in using stable mineral Isotopes as biological tracers. 

Described herein Is a convenient, accurate, sensitive and rapid method for measuring stable Isotopes of selenium In biological materials A rapid sample preparation technique Is used which does not require perchloric acid, with Its associated dangers Based on Isotope dilution techniques and Isotope ratio measurements, the method employs one enriched stable Isotope as the Internal standard and another as the metabolic tag This permits the quantitative measurement of the enriched tracer, unenrlched (natural) selenium present with It, and total selenium In the samples Some examples of the type of Information that can be obtained with these techniques will be described ... 

The technique based on laser-induced breakdown coupled to mass detection, which should thus be designated LIB-MS, is better known as laser plasma ionization mass spectrometry (LI-MS). The earliest uses of the laser-mass spectrometry couple were reported in the late 1960s. Early work included the vaporization of graphite and coal for classifying coals, elemental analyses in metals, isotope ratio measurements and pyrolysis [192]. Later work extended these methods to biological samples, the development of the laser microprobe mass spectrometer, the formation of molecular ions from non-voIatile organic salts and the many multi-photon techniques designed for (mainly) molecular analysis [192]. 

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