ORCID Profile
0000-0002-5371-0730
Current Organisation
James Cook University
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Publisher: Springer Science and Business Media LLC
Date: 04-03-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9JA00361D
Abstract: SpinChem™ ion exchange chromatography (IEC) for subsequent MC-ICP-MS isotope analyses – revolutionizing s le throughput in isotope geochemistry, literally.
Publisher: American Geophysical Union (AGU)
Date: 12-2019
DOI: 10.1029/2019JB017599
Abstract: Recognizing existing materials that can act as proxies for Earth's building blocks, and understanding the accretionary pathway taken during Earth's growth, persist as outstanding issues in need of resolution. In Mahan, Siebert, Blanchard, Badro, et al. (2018, 0.1029/2018JB015991 ), we conducted diamond anvil cell (DAC) Cu metal‐silicate partitioning experiments and coupled these results with a large complement of literature data to characterize Cu metal‐silicate partitioning during Earth's core formation and accretion history. The Comment of Jennings, Wade, and Llovet (2019, 0.1029/2018JB016930 ) contends that secondary X‐ray fluorescence, originating from the Cu holders that experiments are routinely welded to (“lift‐out” grids), compromises the novel Cu partitioning data of Mahan, Siebert, Blanchard, Badro, et al. (2018) beyond utility. To dispel these concerns and further validate our data, we have (i) investigated secondary X‐ray fluorescence effects in a Cu‐free experiment and provided a matrix‐matched data correction, and (ii) rewelded a DAC experiment from a Cu grid to a Mo grid for a comparison of compositional analyses and Cu partitioning results. Secondary fluorescence results, in fact much like the simulated results in Jennings, Wade, and Llovet (2019), indicate that this effect is essentially equal in the metal and silicate phases and therefore has no actual impact on Cu metal‐silicate partition coefficients. Moreover, Cu concentrations and partition coefficients determined using the Mo grid are statistically indistinguishable from that determined using the Cu grid. All results decisively illustrate that while secondary X‐ray fluorescence must be considered where absolute concentrations are the final objective, it has had no meaningful impact on the partitioning data and observations of Mahan, Siebert, Blanchard, Badro, et al. (2018).
Publisher: Elsevier BV
Date: 03-2020
Publisher: Oxford University Press (OUP)
Date: 02-09-2020
DOI: 10.1039/D0MT00134A
Abstract: Biometals play a critical role in both the healthy and diseased brain's functioning. They accumulate in the normal aging brain, and are inherent to neurodegenerative disorders and their associated pathologies. A prominent ex le of this is the brain accumulation of metals such as Ca, Fe and Cu (and more ambiguously, Zn) associated with Alzheimer's disease (AD). The natural stable isotope compositions of such metals have also shown utility in constraining biological mechanisms, and in differentiating between healthy and diseased states, sometimes prior to conventional methods. Here we have detailed the distribution of the biologically relevant elements Mg, P, K, Ca, Fe, Cu and Zn in brain regions of Göttingen minipigs ranging in age from three months to nearly six years, including control animals and both a single- and double-transgenic model of AD (PS1, APP/PS1). Moreover, we have characterized the Ca isotope composition of the brain for the first time. Concentration data track rises in brain biometals with age, namely for Fe and Cu, as observed in the normal ageing brain and in AD, and biometal data point to increased soluble amyloid beta (Aβ) load prior to AD plaque identification via brain imaging. Calcium isotope results define the brain as the isotopically lightest permanent reservoir in the body, indicating that brain Ca dyshomeostasis may induce measurable isotopic disturbances in accessible downstream reservoirs such as biofluids.
Publisher: Oxford University Press (OUP)
Date: 2022
Abstract: Natural stable metal isotopes have shown utility in differentiation between healthy and diseased brain states (e.g. Alzheimer's disease, AD). While the AD brain accumulates some metals, it purges others, namely K (accompanied by increased serum K, suggesting brain–blood transferal). Here, K isotope compositions of Göttingen minipig brain regions for two AD models at midlife are reported. Results indicate heavy K isotope enrichment where amyloid beta (Aβ) accumulation is observed, and this enrichment correlates with relative K depletion. These results suggest preferential efflux of isotopically light K+ from the brain, a linkage between brain K concentrations and isotope compositions, and linkage to Aβ (previously shown to purge cellular brain K+). Brain K isotope compositions differ from that for serum and brain K is much more abundant than in serum, suggesting that changes in brain K may transfer a measurable K isotope excursion to serum, thereby generating an early AD biomarker.
Publisher: Elsevier BV
Date: 2018
Publisher: Proceedings of the National Academy of Sciences
Date: 06-08-2018
Abstract: We present time-anchored elemental abundance data for some of the Solar System’s first solids by tracking Pb−Pb dated chondrule compositions. Volatile element contents generally rise, while redox conditions (based on chondrule Mn/Na ratios) decline beginning ∼1 My after Solar System formation (∼4,567 Ma). These results reflect a continued rise in volatile element contents and their fugacities during chondrule recycling, and early water influx to the inner Solar System followed by its express removal. These observations support the early formation of Mars under oxidizing condition and Earth’s protracted growth under more reducing conditions in an environment increasing in volatile contents with time, while also calling into question the coupling of water and volatile elements during Solar System evolution.
Publisher: Oxford University Press (OUP)
Date: 17-05-2023
Abstract: Potassium (K) is an essential electrolyte for cellular functions in living organisms, and disturbances in K+ homeostasis could lead to various chronic diseases (e.g. hypertension, cardiac disease, diabetes, and bone health). However, little is known about the natural distribution of stable K isotopes in mammals and their application to investigate bodily homeostasis and/or as biomarkers for diseases. Here, we measured K isotopic compositions (δ41K, per mil deviation of 41K/39K from the NIST SRM 3141a standard) of brain, liver, kidney, and red blood cells (RBCs) from 10 mice (five females and five males) with three different genetic backgrounds. Our results reveal that different organs and RBCs have distinct K isotopic signatures. Specifically, the RBCs have heavy K isotopes enrichment with δ41K ranging from 0.67 to 0.08‰, while the brains show lighter K isotopic compositions with δ41K ranging from −1.13 to −0.09‰ compared to the livers (δ41K = −0.12 ± 0.58‰) and kidneys (δ41K = −0.24 ± 0.57‰). We found that the K isotopic and concentration variability is mostly controlled by the organs, with a minor effect of the genetic background and sex. Our study suggests that the K isotopic composition could be used as a biomarker for changes in K+ homeostasis and related diseases such as hypertension, cardiovascular, and neurodegenerative diseases.
Publisher: Elsevier BV
Date: 2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1JA00294E
Abstract: The development of collision-cell multi-collection inductively-coupled-plasma mass-spectrometers has revolutionized K isotope chemistry, improving the sensitivity by over a factor of 10 compared to that of older generation instruments.
Publisher: Elsevier BV
Date: 08-2018
Publisher: Elsevier BV
Date: 03-2018
Publisher: American Geophysical Union (AGU)
Date: 10-2018
DOI: 10.1029/2018JB015991
Publisher: Oxford University Press (OUP)
Date: 2018
DOI: 10.1039/C8MT00179K
Abstract: For the first time, the distribution of Zn isotopes and numerous bio-metals has been measured in minipig organs and blood (anatomical diagram © IPGP).
No related grants have been discovered for Brandon Mahan.