High-efficiency liquid-scintillation counting of 14C-labelled material in aqueous solution and determination of specific activity of labelled proteins.
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ABSTRACT:
SUBMITTER: Hall TC
PROVIDER: S-EPMC1207196 | biostudies-other | 1965 Sep
REPOSITORIES: biostudies-other
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Project description:1. A method of assaying (14)C in ketone bodies present in blood by using liquid-scintillation counting is described. 2. d(-)-beta-Hydroxy[(14)C]butyrate is converted quantitatively into [(14)C]acetoacetate by means of a coupled oxidoreduction reaction involving NAD(+), d(-)-beta-hydroxybutyrate dehydrogenase and malic dehydrogenase in the presence of a high concentration of oxaloacetate. 3. [(14)C]Acetoacetate is decarboxylated to acetone and carbon dioxide which are trapped separately in a double-well flask and counted subsequently. 4. The method permits the determination of (14)C activity in the individual ketone bodies and allows the activity in the carboxyl carbon atoms of acetoacetate or of d(-)-beta-hydroxybutyrate to be assayed separately from the activity in the remainder of the molecule. 5. Recoveries of (14)C-labelled ketone bodies added to blood approach 100% with good reproducibility in replicate analyses.
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Project description:An informal bilateral comparison of (14)C liquid scintillation (LS) counting at the National Research Council of Canada (NRC) and the National Institute of Standards and Technology (NIST) has been completed. Two solutions, one containing (14)C-labeled sodium benzoate and one containing (14)C-labeled n-hexadecane, were measured at both laboratories. Despite observed LS cocktail instabilities, the two laboratories achieved accord in their standardizations of both solutions. At the conclusion of the comparison, the beta spectrum used for efficiency calculations was identified as inadequate and the data were reanalyzed with different inputs, improving accord.
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Project description:Stable suspensions of eutectic gallium indium (EGaIn) liquid metal nanoparticles form by probe-sonicating the metal in an aqueous solution. Positively-charged molecular or macromolecular surfactants in the solution, such as cetrimonium bromide or lysozyme, respectively, stabilize the suspension by interacting with the negative charges of the surface oxide that forms on the metal. The liquid metal breaks up into nanospheres via sonication, yet can transform into rods of gallium oxide monohydroxide (GaOOH) via moderate heating in solution either during or after sonication. Whereas heating typically drives phase transitions from solid to liquid (via melting), here heating drives the transformation of particles from liquid to solid via oxidation. Interestingly, indium nanoparticles form during the process of shape transformation due to the selective removal of gallium. This dealloying provides a mechanism to create indium nanoparticles at temperatures well below the melting point of indium. To demonstrate the versatility, we show that it is possible to shape transform and dealloy other alloys of gallium including ternary liquid metal alloys. Scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDS) mapping, and X-ray diffraction (XRD) confirm the dealloying and transformation mechanism.
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Project description:PurposeThe implementation of photon-counting detectors is widely expected to be the next breakthrough in X-ray computed tomography (CT) instrumentation. A small number of prototype scanners equipped with direct-conversion detectors based on room-temperature semiconductors, such as CdTe and CdZnTe (CZT), are currently installed at medical centers. Here, we investigate the feasibility of using silicon photomultiplier (SiPM)-based scintillation detectors in photon-counting computed tomography (PCCT) scanners, as a potential alternative to CdTe and CZT detectors.MethodsWe introduce a model that allows us to compute the expected energy resolution as well as the expected pulse shape and associated rate capability of SiPM-based PCCT detectors. The model takes into account SiPM saturation and optical crosstalk, because these phenomena may substantially affect the performance of SiPM-based PCCT detectors with sub-mm pixels. We present model validation experiments using a single-pixel detector consisting of a 0.9 × 0.9 × 1.0 mm3 LuAP:Ce scintillation crystal coupled to a 1 × 1 mm2 SiPM. We subsequently use the validated model to compute the expected performance of the fast scintillators LYSO:Ce, LuAP:Ce, and LaBr3 :Ce, coupled to currently available SiPMs, as well as to a more advanced SiPM prototype with improved dynamic range, for sub-mm pixel sizes.ResultsThe model was found to be in good agreement with the validation experiments, both with respect to energy resolution and pulse shape. It shows how saturation progressively degrades the energy resolution of detectors equipped with currently available SiPMs as the pixel size decreases. Moreover, the expected pulse duration is relatively long (~200 ns) with these SiPMs. However, when LuAP:Ce and LaBr3 :Ce are coupled to the more advanced SiPM prototype, the pulse duration improves to less than 60 ns, which is in the same order of magnitude as pulses from CdTe and CZT detectors. It follows that sufficient rate capability can be achieved with pixel sizes of 400 μm or smaller. Moreover, LaBr3 :Ce detectors can provide an energy resolution of 11.5%-13.5% at 60 keV, comparable to CdTe and CZT detectors.ConclusionsThis work provides first evidence that it may be feasible to develop SiPM-based scintillation detectors for PCCT that can compete with CdTe and CZT detectors in terms of energy resolution and rate capability.
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