10-MV Accelerator Mass Spectrometer
LLNL's National Resource for Biomedical Accelerator Mass Spectrometry (BioAMS) was established to make AMS available to biomedical researchers who need to accurately measure very low levels of 14C. Located in the Center for Accelerator Mass Spectrometry (CAMS) and Physical and Life Sciences Directorate (PLS), this national user facility specializes in the biomedical uses of 14C and 3H, and also uses AMS to measure other isotopes, such as 41Ca, 10Be, 26Al, and 99Tc.
AMS as a Tool in the Biological Sciences
Over the last 20 years, AMS has evolved as a biomedical tool, offering the required sensitivity, selectivity, and precision to address questions that alternative methodologies have been unable to achieve in practice. AMS was originally applied in the life sciences to overcome limitations in detection sensitivity for studying the molecular damage caused by exposure to low levels of environmental carcinogens and pollutants. For example, AMS can be used to conduct metabolite analysis at the picomole to the attomole level and is also being used to identify macromolecular targets for drugs and toxic compounds.
The high sensitivity of AMS is allowing our collaborators to address important issues in nutrition, pharmacology, cell biology and comparative medicine. Studies using 14C-labeled agents show that activities as low as a few nCi/person can be used to assess metabolism, and activities as low as 100 nCi/person can be used to address macromolecular binding in the study of candidate drugs or toxicants. This level of radioactive dose is less than that from a single day's exposure to background ionizing radiation, or a chest x-ray. In most cases the dose is less than that received during a cross-country commercial airline flight.
The high sensitivity of AMS allows use of small samples of exfoliated tissues, isolated cell subpopulations, and precious tissues of human or animal origin. Sensitivity also enables quantitative study of ligand—macromolecule interactions at physiologically relevant concentrations, for studying effects such as hormones at low concentrations or where the receptor is present in low copy number, and for studying early events in the pathology of infection by labeling bacteria and viruses. The increased sensitivity also facilitates the use of compounds that are difficult to synthesize at high specific activity or cannot be used in large amounts. This Resource seeks to both develop the methods and instrumentation to make AMS a general use tool for biomedical researchers and to make it available for investigators needing access to techniques for the ultra-trace analysis of radioisotopes in biological studies.
Resource Analytical Equipment
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Resource facilities at LLNL include laboratories for sample preparation, chemical separations, physical analysis, and cell culture. These laboratories are equipped with fume hoods, a Nanopure water system, refrigerators, freezers, water baths, centrifuges, balances, vacuum dryers, incubators for cell culture and an autoclave.
One laboratory is dedicated to the conversion of samples to uniform solids for AMS measurement: filamentous graphite for 14C and titanium hydride for 3H. This laboratory contains ovens for sample oxidation and reductions, vacuum systems for gaseous sample transfer, and an oxy:acetylene torch for the sealing of quartz and Pyrex tubes under vacuum. An AAALAC-certified animal care facility is available.
Using BioAMS at LLNL
For more information about using the LLNL BioAMS Resource, please visit the BioAMS Web site.
Contact: Mila Shapovalov, firstname.lastname@example.org, 925-424-5232
The Technique of Accelerator Mass Spectrometry
AMS is a technique for measuring isotope ratios with high selectivity, sensitivity, and precision. In general, AMS separates a rare radioisotope from stable isotopes and molecular ions of the same mass using a variety of nuclear physics techniques. In the case of carbon, 14C ions are separated and counted as particles relative to 13C or 12C that are measured as an electrical current. The key steps of AMS allowing quantitative and specific measurement of isotopes are the production of negative ions from the sample to be analyzed, a molecular disassociation step to convert the negatively charged molecular ions to positively charged nuclei and the use of high energies (MeV) which allow for the identification of ions with high selectivity. See the BioAMS site for more information.