Isotopes, stable biochemistry

Applications of isotopes in biochemistry have been manifold. Besides tracing pathways and following the rates of isotope uptake and their intracellular localization, labeling molecules in selected stable positions allowed studies to be made of reaction details, such as those in citrate... 

Matwiyoff, N. A. Walker, T. E. "Trends in the Use of Stable Isotopes in Biochemistry and Pharmacology" in Stable Isotopes in the Life Sciences (Proc. Symp. Leipzig, 1977) IAEA,... 

Some aspects of the biochemistry of metabolic processes affecting nutrients appear to have significant consequences for the expected behavior of stable carbon isotopes as tracers of diet. Specifically, we have seen that the simple model of a total scrambling of carbon atoms during endogenous biosynthesis is inconsistent with the expected pathways of some nutrients, whereas other isotopic records in ancient human tissues can be adequately accounted for by this model. 

Cannes, L.Z., Martinez del Rio, C., Koch, P. (1998). Natural abundance variations in stable isotopes and their potential uses in animal physiological ecology. Comparative Biochemistry and Physiology - Part A Molecular Integrative Physiology, Vol. 119, No. 3, pp. 725-737. (http //dx.doi.org/10.1016/S1095-6433(98)01016-2)... 

Tracer studies with stable isotopes have a long tradition in medical biochemistry. or 0 do not cause adverse physiological effects even at higher en-... 

The highly precise measurement of isotope ratios has a long tradition in organic geochemistry. Nowadays, the elucidation of stable isotope distributions is highly desirable in view of fundamental studies in biochemistry, nutrition, drug research and also in the authenticity assessment of food ingredients. 

We will not attempt to cover the specific mechanisms and complex biochemistry of calcification in different organisms, which have been reviewed in numerous articles (e.g., Degens, 1976 Watabe, 1981 Chave, 1984 Lowenstam and Weiner, 1989). Instead we will concentrate on observations of how biogenic carbonates reflect environmental conditions. These observations can be divided into the major areas of mineralogy, stable isotope ratios, and trace component concentration. The stable isotope and trace component chemistries have received substantially more attention during the last 25 years than has mineralogy. Inorganic phases are also discussed in this section as a means of comparison with skeletal materials. 

Watkins, N. K., Fitter, A. H., Graves, J. D. Robinson, D. (1996). Quantification using stable carbon isotopes of carbon transfer between C3 and C4 plants linked by a common mycorrhizal network. Soil Biology and Biochemistry, 28, 471-7. 

In 1970 the author moved to a new base in the University of Waikato, Hamilton, New Zealand. Here the glassblowing workshop services the School of Science, composed of Earth Sciences, Biological Sciences, Physics and Chemistry. Foreseeably Chemistry, which teaches organic, inorganic, physical and stable isotope chemistry, and in recent years, biochemistry, has made the greatest demand on the service. 

Our ability to detect minute amounts of radioisotopes makes them powerful tools for studying processes in biochemistry, medicine, materials science, environmental studies, and many other scientific and industrial fields. Such uses depend on the fact that isotopes of an element exhibit very similar chemical and physical behavior. In other words, except for having a less stable nucleus, a radioisotope has nearly the same chemical properties as a nonradioactive isotope of a given element. For example, the fact that " C02 is utilized hy a plant in the same way as "C02 forms the basis of radiocarbon dating. 

Stable isotopes of each of these elements have played important roles in elucidation of their chemistries. Specifically, and have been used as stable tracers for research on N-chemistry dealing with food and fiber production, metabolic pathways, and environmental control. Their value is ultimately limited because macroscopic amounts of carrier often exceed in situ concentrations (and therefore influence the biochemistry), and natural nitrogen isotope fractionation leads to variances in natural abundance. Nevertheless, stable tracers have been used effectively in many studies, including foflowing N-cycle processes in soils (1) and unraveling metabolic pathways (2,3). 

The possibihty to quantify in vivo biochemistry noninvasively using compounds labeled with radioactive isotopes is a milestone in medical imaging. The first production of the short-Kved positron emitting radionuchde was performed in 1934 (Crane and Lauritsen 1934). It was found that decays with a half-hfe of 20.4 min by positron emission to the stable nuchde... 

The capability of PTR-MS to detect stable isotopes is potentially a very useful tool to study the biological pathways in relation to plant volatiles. A well-studied example is the formation of C-isoprene (CsHg) during C02 fumigation, demonstrating the linkage between photosynthesis and isoprene emission in intact leaves from oak and cottonwood [16]. Despite the fact that the biochemistry of isoprene formation is known, the role of isoprene biosynthesis in plants is stiU not clear, especially in its relation to photosynthetic precursors in leaf chloroplasts. 

Brahme NM, Gonraler JE, Rolls JR, Messier EJ, Mitsak S, Hurley LH. Biosynthesis nf the tin-comycins. 1. Studies using stable isotopes on the biosynthesis of the propyl- and ethyi-L-hygric acid moieties of lincomycin A and B. J Am Chem Soc 1984 106 7873-7878. Argoudelis AD. Fox JA, Mason, DJ. Studies on the bk ymhesis of lincomyrin. II. Antibiotic U l 1,973, N-demethyl lincomycin. Biochemistry 1965 4 710-713. 

Nelson, B.C., Pfeiffer, C.M., Margolis, S.A., and Nelson, C.P., 2003. Affinity extraction combined with stable isotope dilution LC/MS for the determination of 5-methyltetrahydrofolate in human plasma. Analytical Biochemistry. 313 117-127. 

Monch, S., Netzel, M., Netzel, G., and Rychlik, M., 2010. Quantitation of folates and their catabolites in blood plasma, erythrocytes, and urine by stable isotope dilution assays. Analytical Biochemistry. 398 150-160. 

Pawlosky, R.J., Flanagan, V.P., and Pfeiffer, C.M., 2001. Determination of 5-methyltetrahydrofolic acid in human serum by stable-isotope dilution high-performance liquid chromatography-mass spectrometry. Analytical Biochemistry. 298 299-305. 

Ohki and Kainosho have reviewed various stable isotope labelling techniques for protein NMR spectroscopy. In addition, advances in sample preparation methods have been discussed. Progress in sample preparation methods is shown to promote novel labelling strategies for NMR analyses of proteins that previously could not be assessed by NMR. It has been shown that stable isotope aided NMR has great potential for applications in molecular biology, biochemistry, and protein science, as it is the only method that can detect the dynamic behaviour of each residue of a protein in solution. 

Gilker, CD., Pesola, G.R., and Matthews, D. (1992) A mass spectrometric method for measuring glycerol levels and enrichments in plasma using 13C and 2H stable isotopic tracers. Analytical Biochemistry, 5,172-178. 

Grostic, M.F. and Rinehart, K.L. (1971), Mass spectral studies employing stable isotopes in chemistry and biochemistry. In Mass Spectrometry, Techniques and Applications (ed. G.W.A. Milne), Wiley-Interscience, New York, p. 217. 

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