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    Settling behaviors of microplastic disks in water
    (2023) Yang, Ge; Yu, Zijian; Baki, Abul B. M.; Yao, Weiwei; Ross, Matthew S.; Chi, Wanqing; Zhang, Wenming
    Microplastic (MP) disks have not been studied for settling behaviors in aquatic environments, which affects the transport and fate of MPs. Therefore, settling experiments were conducted on MP disks of three shapes and four common-seen materials. Lighter MP disks (with density ρs = 1.038 g/cm3 and length l ≤ 5 mm) followed rectilinear vertical trajectories, while heavier MP disks (ρs = 1.161–1.343 g/cm3 and l = 5 mm) followed zigzag trajectories with oscillations and rotations. The mean terminal settling velocities of MP disks were 19.6–48.8 mm/s. Instantaneous settling velocities of heavier MP disks fluctuated. Existing formulas could not accurately predict the settling velocity of MP disks; thus, a new model was proposed with an error of 15.5 %. Finally, the Red - I* diagram (Red is the disk Reynolds number and I* is the dimensionless moment of inertia) was extended for MP disks to predict settling trajectories.
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    Ice, mountains, and people: applying a multi-proxy approach to reveal changes in Alberta’s alpine ecosystems through ice patch research
    (2023) Tirlea, Diana; Kristensen, Todd; Osicki, Aaron; Jensen, Britta; Williams, Krista; Caners, Richard; Lumley, Lisa; Woywitka, Robin
    Glacial archaeology has grown and progressed rapidly in recent decades with technological innovations and shifting socio-political issues. However, research on ice patches in the Canadian Rocky Mountains is in its infancy. While Holocene glacial ice retreat, advance, and morphology are well studied in Canada, ice patches in general tend to be understudied because of their limited geomorphological impact on landscapes. This oversight is concerning as their isolated nature, lower elevation, and small mass make ice patches even more susceptible to climate change than glaciers. The importance of documenting these features is heightened by a persisting but tenuous biological importance to a range of modern species. The lack of flow in ice patches also makes them excellent archives of palaeoenvironmental and organic-based cultural materials, as layers of ice and preserved contents are not as distorted as they may be by flow in glaciers.
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    Estimated discharge of microplastics via urban stormwater during individual rain events
    (2023) Ross, Matthew S.; Loutan, Alyssa; Groeneveld, Tianna M.; Molenaar, Danielle; Kroetch, Kimberly; Bujaczek, Taylor; Kolter, Sheldon; Moon, Sarah; Franczak, Brian C.
    Urban stormwater runoff is an important pathway for the introduction of microplastics and other anthropogenic pollutants into aquatic environments. Highly variable concentrations of microplastics have been reported globally in runoff, but knowledge of key factors within urban environments contributing to this variability remains limited. Furthermore, few studies to date have quantitatively assessed the release of microplastics to receiving waters via runoff. The objectives of this study were to assess the influence of different catchment characteristics on the type and amount of microplastics in runoff and to provide an estimate of the quantity of microplastics discharged during rain events. Stormwater samples were collected during both dry periods (baseflow) and rain events from 15 locations throughout the city of Calgary, Canada’s fourth largest city. These catchments ranged in size and contained different types of predominant land use. Microplastics were found in all samples, with total concentrations ranging from 0.7 to 200.4 pcs/L (mean = 31.9 pcs/L). Fibers were the most prevalent morphology identified (47.7 ± 33.0%), and the greatest percentage of microplastics were found in the 125–250 µm size range (26.6 ± 22.9%) followed by the 37–125 µm size range (24.0 ± 22.3%). Particles were predominantly black (33.5 ± 33.8%), transparent (22.6 ± 31.3%), or blue (16.0 ± 21.6%). Total concentrations, dominant morphologies, and size distributions of microplastics differed between rain events and baseflow, with smaller particles and higher concentrations being found during rain events. Concentrations did not differ significantly amongst catchments with different land use types, but concentrations were positively correlated with maximum runoff flow rate, catchment size, and the percentage of impervious surface area within a catchment. Combining microplastic concentrations with hydrograph data collected during rain events, we estimated that individual outfalls discharged between 1.9 million to 9.6 billion microplastics to receiving waters per rain event. These results provide further evidence that urban stormwater runoff is a significant pathway for the introduction of microplastics into aquatic environments and suggests that mitigation strategies for microplastic pollution should focus on larger urbanized catchments.
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    Editorial: multiscale modeling for the liver
    (2023) Ho, Harvey; Rezania, Vahid; Schwen, Lars Ole
    The liver is the central metabolic organ in the mammalian body. Hepatic functions need to be understood from a multiscale perspective, i.e., at the organism, organ, lobular, cellular, and molecular levels that can span vastly different timeframes, e.g., from milliseconds of molecular events to months or years of chronic disease formation (cf. Figure 1). Computational models coupled with experimental measurements and clinical observations provide a viable and cost-effective means to investigate hepatic function. The Research Topic collected some recent results, clinical observations, and updated reviews or perspectives; the seven contributions are briefed below.
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    Dual continuum upscaling of liver lobule flow and metabolism to the full organ scale
    (2022) Coombe, Dennis; Rezania, Vahid; Tuszynski, Jack A.
    The liver is the body’s primary metabolic organ and its functions operate at multiple time and spatial scales. Here we employ multiscale modelling techniques to describe these functions consistently, based on methods originally developed to describe reactive fluid flow processes in naturally-fractured geological sediments. Using a fully discretized idealized lobule model for flow and metabolism, a dual continuum approach is developed in two steps: 1) Two interacting continua models for tissue and sinusoids properties, followed by 2) further upscaled dual continua models leading to an averaged lobule representation. Results (flows, pressures, concentrations, and reactions) from these two approaches are compared with our original model, indicating the equivalences and approximations obtained from this upscaling for flow, diffusion, and reaction parameters. Next, we have generated a gridded dual continuum model of the full liver utilizing an innovative technique, based on published liver outline and vasculature employing a vasculature generation algorithm. The inlet and outlet vasculature systems were grouped into five generations each based on radius size. With a chosen grid size of 1 mm3, our resulting discretized model contains 3,291,430 active grid cells. Of these cells, a fraction is occupied vasculature, while the dominant remaining fraction of grid cells approximates liver lobules. Here the largest generations of vasculature occupy multiple grid cells in cross section and length. The lobule grid cells are represented as a dual continuum of sinusoid vasculature and tissue. This represents the simplest gridded dual continuum representation of the full liver organ. With this basic model, numerous full liver drug metabolism simulations were run. A non-reactive PAC (paclitaxel) injection case including only convective transfer between vasculature and tissue was compared with including an additional diffusive transfer mechanism. These two cases were then rerun with tissue reaction, converting injected PAC to PAC-OH (6-hydroxypaclitaxel). There was little transfer of PAC from vasculature to tissue without the addition of diffusive transfer, and this had a significant observable effect on internal PAC distribution in the absence of reaction, and also on the distribution of PAC-OH for the reactive cases.
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    Uranium surface processes with sandstone and volcanic rocks in acidic and alkaline solutions
    (2023) Kenney, Janice; Lezama-Pacheco, Juan; Fendorf, Scott; Alessi, Daniel S.; Weiss, Dominik J.
    Understanding the behaviour of uranium waste, for disposal purposes, is crucial due to the correlation between pH values and the disposal of distinct types of waste, with low level waste typically associated with acidic pH values, and higher and intermediate level waste commonly related to alkaline pH values. We studied the adsorption of U(VI) on sandstone and volcanic rock surfaces at pH 5.5 and 11.5 in aqueous solutions with and without bicarbonate (2 mM HCO3–) using XAS and FTIR. In the sandstone system, U(VI) adsorbs as a bidentate complex to Si at pH 5.5 without bicarbonate and as uranyl carbonate species with bicarbonate. At pH 11.5 without bicarbonate, U(VI) adsorbs as monodentate complexes to Si and precipitates as uranophane. With bicarbonate at pH 11.5, U(VI) precipitated as a Na-clarkeite mineral or remained as a uranyl carbonate surface species. In the volcanic rock system, U(VI) adsorbed to Si as an outer sphere complex at pH 5.5, regardless of the presence of bicarbonate. At pH 11.5 without bicarbonate, U(VI) adsorbed as a monodentate complex to one Si atom and precipitated as a Na-clarkeite mineral. With bicarbonate at pH 11.5, U(VI) sorbed as a bidentate carbonate complex to one Si atom. These results provide insight into the behaviour of U(VI) in heterogeneous, real-world systems related to the disposal of radioactive waste.
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    Estimated discharge of microplastics via urban stormwater during individual rain events
    (2023) Ross, Matthew S.; Loutan, Alyssa; Groeneveld, Tianna M.; Molenaar, Danielle; Kroetch, Kimberly; Bujaczek, Taylor; Kolter, Sheldon; Moon, Sarah; Huynh, Alan; Khayam, Rosita; Franczak, Brian C.
    Urban stormwater runoff is an important pathway for the introduction of microplastics and other anthropogenic pollutants into aquatic environments. Highly variable concentrations of microplastics have been reported globally in runoff, but knowledge of key factors within urban environments contributing to this variability remains limited. Furthermore, few studies to date have quantitatively assessed the release of microplastics to receiving waters via runoff. The objectives of this study were to assess the influence of different catchment characteristics on the type and amount of microplastics in runoff and to provide an estimate of the quantity of microplastics discharged during rain events. Stormwater samples were collected during both dry periods (baseflow) and rain events from 15 locations throughout the city of Calgary, Canada’s fourth largest city.
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    A specific dispiropiperazine derivative that arrests cell cycle, induces apoptosis, necrosis and DNA damage
    (2023) Liu, Victor P.; Li, Wai-Ming; Lofroth, Jack; Zeb, Mehreen; Patrick, Brian O.; Bott, Tina; Lee, Chow H.
    Dispiropiperazine compounds are a class of molecules known to confer biological activity, but those that have been studied as cell cycle regulators are few in number. Here, we report the characterization and synthesis of two dispiropiperazine derivatives: the previously synthesized spiro[2′,3]- bis(acenaphthene-1′-one)perhydrodipyrrolo-[1,2-a:1,2-d]-pyrazine (SPOPP-3, 1), and its previously undescribed isomer, spiro[2′,5′] bis(acenaphthene-1′-one)perhydrodipyrrolo-[1,2-a:1,2-d]-pyrazine (SPOPP-5, 2). SPOPP-3 (1), but not SPOPP-5 (2), was shown to have anti proliferative activity against a panel of 18 human cancer cell lines with IC50 values ranging from 0.63 to 13 μM. Flow cytometry analysis revealed that SPOPP-3 (1) was able to arrest cell cycle at the G2/M phase in SW480 human cancer cells. Western blot analysis further confirmed the cell cycle arrest is in the M phase. In addition, SPOPP-3 (1) was shown to induce apoptosis, necrosis, and DNA damage as well as disrupt mitotic spindle positioning in SW480 cells. These results warrant further investigation of SPOPP-3 (1) as a novel anti-cancer agent, particularly for its potential ability to sensitize cancer cells for radiation induced cell death, enhance cancer immunotherapy, overcome apoptosis-related drug resistance and for possible use in synthetic lethality cancer treatments.
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    Shortwave infrared hyperspectral imaging as a novel method to elucidate multi-phase dolomitization, recrystallization, and cementation in carbonate sedimentary rocks
    (2021) McCormick, Cole A.; Corlett, Hilary; Stacey, Jack; Hollis, Cathy; Feng, Jilu; Rivard, Benoit; Omma, Jenny E.
    Carbonate rocks undergo low-temperature, post-depositional changes, including mineral precipitation, dissolution, or recrystallisation (diagenesis). Unravelling the sequence of these events is time-consuming, expensive, and relies on destructive analytical techniques, yet such characterization is essential to understand their post-depositional history for mineral and energy exploitation and carbon storage. Conversely, hyperspectral imaging offers a rapid, non-destructive method to determine mineralogy, while also providing compositional and textural information. It is commonly employed to differentiate lithology, but it has never been used to discern complex diagenetic phases in a largely monomineralic succession. Using spatial-spectral endmember extraction, we explore the efficacy and limitations of hyperspectral imaging to elucidate multi-phase dolomitization and cementation in the Cathedral Formation (Western Canadian Sedimentary Basin). Spectral endmembers include limestone, two replacement dolomite phases, and three saddle dolomite phases. Endmember distributions were mapped using Spectral Angle Mapper, then sampled and analyzed to investigate the controls on their spectral signatures. The absorption-band position of each phase reveals changes in %Ca (molar Ca/(Ca + Mg)) and trace element substitution, whereas the spectral contrast correlates with texture. The ensuing mineral distribution maps provide meter-scale spatial information on the diagenetic history of the succession that can be used independently and to design a rigorous sampling protocol.
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    Basin scale evolution of zebra textures in fault-controlled, hydrothermal dolomite bodies: insights from the Western Canadian Sedimentary Basin
    (2023) McCormick, Cole A.; Corlett, Hilary; Clog, Matthieu; Boyce, Adrian; Tartèse, Romain; Steele-MacInnis, Matthew; Hollis, Cathy
    Structurally controlled dolomitization typically involves the interaction of high-pressure (P), high-temperature (T) fluids with the surrounding host rock. Such reactions are often accompanied by cementation and recrystallization, with the resulting hydrothermal dolomite (HTD) bodies including several ‘diagnostic’ rock textures. Zebra textures, associated with boxwork textures and dolomite breccias, are widely considered to reflect these elevated P/T conditions. Although a range of conceptual models have been proposed to explain the genesis of these rock textures, the processes that control their spatial and temporal evolution are still poorly understood. Through the detailed petrographical and geochemical analysis of HTD bodies, hosted in the Middle Cambrian strata in the Western Canadian Sedimentary Basin, this study demonstrates that a single genetic model cannot be applied to all the characteristics of these rock textures. Instead, a wide array of sedimentological, tectonic and metasomatic processes contribute to their formation; each of which is spatially and temporally variable at the basin scale. Distal to the fluid source, dolomitization is largely stratabound, comprising replacement dolomite, bedding-parallel zebra textures and rare dolomite breccias (non-stratabound, located only proximal to faults). Dolomitization is increasingly non-stratabound with proximity to the fluid source, comprising bedding-inclined zebra textures, boxwork textures and dolomite breccias that have been affected by recrystallization. Petrographical and geochemical evidence suggests that these rock textures were initiated due to dilatational fracturing, brecciation and precipitation of saddle dolomite as a cement, but significant recrystallization occurred during the later stages of dolomitization. These rock textures are closely associated with faults and carbonate-hosted ore deposits (e.g. magnesite, rare earth element and Mississippi Valley–type mineralization), thus providing invaluable information regarding fluid flux and carbonate metasomatism under elevated P/T conditions.
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    Mapping amorphous SiO2 in Devonian shales and the possible link to marine productivity during incipient forest diversification
    (2023) Corlett, Hilary; Feng, Jilu; Playter, Tiffany; Rivard, Benoit
    Silica cycling in the world’s oceans is not straightforward to evaluate on a geological time scale. With the rise of radiolarians and sponges from the early Cambrian onward, silica can have two depositional origins, continental weathering, and biogenic silica. It is critical to have a reliable method of differentiating amorphous silica and crystalline silica to truly understand biogeochemical and inorganic silica cycling. In this study, opal-A is mapped across the Western Canada Sedimentary Basin in the Late Devonian Duvernay Formation shales using longwave hyperspectral imaging alongside geochemical proxies that differentiate between crystalline and amorphous SiO2, during the expansion of the world’s early forests. Signaled by several carbon isotope excursions in the Frasnian, the punctata Event corresponds to the expansion of forests when vascular land plants develop seeds and deeper root networks, likely resulting in increased pedogenesis. Nutrients from thicker soil horizons entering the marine realm are linked to higher levels of primary productivity in oceans and subsequent oxygen starvation in deeper waters at this time. The results of this study reveal, for the first time, the spatial distribution of amorphous SiO2 across a sedimentary basin during this major shift in the terrestrial realm when forests expand and develop deeper root networks.
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    Far-ultraviolet dust extinction and molecular hydrogen in the diffuse Milky Way interstellar medium
    (2023) Putte, Dries Van De; Cartledge, Stefan; Gordon, Karl; Geoffrey, Chiekwero; Roman-Duval, Julia
    We aim to compare variations in the full-UV dust extinction curve (912–3000 Å), with the H I/H2/total H content along diffuse Milky Way sightlines, to investigate possible connections between ISM conditions and dust properties. We combine an existing sample of 75 UV extinction curves based on IUE and FUSE data, with atomic and molecular column densities measured through UV absorption. The H2 column density data are based on existing Lyman–Werner absorption band models from earlier work on the extinction curves. Literature values for the H I column density were compiled, and improved for 23 stars by fitting a Lyα profile to archived spectra. We discover a strong correlation between the H2 column and the far-UV extinction, and the underlying cause is a linear relationship between H2 and the strength of the far-UV rise feature. This extinction does not scale with H I, and the total H column scales best with A(V) instead. The carrier of the far-UV rise therefore coincides with molecular gas, and further connections are shown by comparing the UV extinction features to the molecular fraction. Variations in the gas-to-extinction ratio N (H) A(V) correlate with the UV-to-optical extinction ratio, and we speculate this could be due to coagulation or shattering effects. Based on the H2 temperature, the strongest far-UV rise strengths are found to appear in colder and denser sightlines.
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    Permafrost, geomorphic, and hydroclimatic controls on mercury, methylmercury, and lead concentrations and exports in Old Crow River, arctic western Canada
    (2022) Staniszewska, Kasia J.; Reyes, Alberto V.; Cooke, Colin A.; Miller, Brooklyn S.; Woywitka, Robin
    Permafrost degradation has been implicated as a dominant control on riverine mercury fluxes in arctic watersheds. However, the importance of permafrost thaw on fluxes of mercury, methylmercury, and trace metals such as lead—relative to other geomorphic and hydroclimatic controls—remains unclear. To investigate these controls, we conducted ~weekly water chemistry sampling at the mouth of the Old Crow River, a pristine, 13,900 km2 watershed in arctic Canada underlain entirely by continuous permafrost. Mercury, methylmercury, and lead concentrations were low on average (~ 2 ng/L, 0.04 ng/L, 0.8 μg/L, respectively), and peaked during the freshet (< 7 ng/L, 0.11 ng/L, 11 μg/L, respectively). The trace elements had strong positive association with suspended sediment, and were mobilized during periods of high discharge (freshet and rainfall). Summer time sampling of major tributaries and at thaw slumps revealed that trace element concentrations were not elevated downstream of thaw slumps or thermokarst lakes across the watershed. Ubiquitous thermokarst in the Old Crow basin did not result in anomalously high catchment-scale concentrations, fluxes, and yields of mercury, methylmercury, nor lead. Rather, warming-driven increases in precipitation and elevated discharge during freshet and rainfall promoted permafrost and talik river bank erosion. This erosion, which was controlled by landscape and geomorphic factors, supplied short-lived increases in particle-bound trace element flux.
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    A nanometric probe of the local proton concentration in microtubule-based biophysical systems
    (2022) Kalra, Aarat P.; Eakins, Boden B.; Vagin, Sergei I.; Wang, Hui; Patel, Sahil D.; Winter, Philip; Aminpour, Maral; Lewis, John D.; Rezania, Vahid; Shankar, Karthik; Scholes, Gregory D.; Tuszynski, Jack A.; Rieger, Bernhard; Meldrum, Alkiviathes
    We show a double-functional fluorescence sensing paradigm that can retrieve nanometric pH information on biological structures. We use this method to measure the extent of protonic condensation around microtubules, which are protein polymers that play many roles crucial to cell function. While microtubules are believed to have a profound impact on the local cytoplasmic pH, this has been hard to show experimentally due to the limitations of conventional sensing techniques. We show that subtle changes in the local electrochemical surroundings cause a double-functional sensor to transform its spectrum, thus allowing a direct measurement of the protonic concentration at the microtubule surface. Microtubules concentrate protons by as much as one unit on the pH scale, indicating a charge storage role within the cell via the localized ionic condensation. These results confirm the bioelectrical significance of microtubules and reveal a sensing concept that can deliver localized biochemical information on intracellular structures.
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    Scanning the auroral skies: the Athabasca University robotic telescope
    (2019) Cartledge, Stefan; Schofield, Ian; Connors, Martin; Langill, Phil
    The Athabasca University Robotic Telescope (AURT) is a moderate aperture (0.36 m) networked robotic telescope that supports teaching and research at Athabasca University, a pioneering and prominent distance learning university in Canada. This paper reviews the establishment and implementation of a robotic, Internet-based astronomical observatory whose development parallels and complements Athabasca University’s auroral observatory. We discuss the unique features and challenges of the northern observing environment, give examples of teaching and research activities underway at AURT, and discuss an investigation into dark sky conditions over the AURT site.
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    Multifractality nature of microtubule dynamic instability process
    (2021) Rezania, Vahid; Sudirga, Ferry C.; Tuszynski, Jack A.
    The irregularity of growing and shortening patterns observed experimentally in microtubules and their ensembles reflects a dynamical system that fluctuates stochastically between assembly and disassembly phases. The observed time series of microtubule lengths have been extensively analyzed to shed light on structural and dynamical properties of microtubules. Here, for the first time, Multifractal Detrended Fluctuation analysis (MFDFA) has been employed to investigate the multifractal and topological properties of both experimental and simulated microtubule time series. We find that the time dependence of microtubule length possesses true multifractal characteristics and cannot be described by mono-fractal distributions. Based on the multifractal spectrum profile, a set of multifractal indices have been calculated that can be related to the level of dynamical processes in microtubules. We also show that the resulting multifractal spectra for the simulated data might not be comparable with experimental data.
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    A new method for protein characterization and classification using geometrical features for 3D face analysis: an example of tubulin structures
    (2021) Di Grazia, Luca; Aminpour, Maral; Vezzetti, Enrico; Rezania, Vahid; Marcolin, Federica; Tuszynski, Jack A.
    This article reports on the results of research aimed to translate biometric 3D face recognition concepts and algorithms into the field of protein biophysics in order to precisely and rapidly classify morphological features of protein surfaces. Both human faces and protein surfaces are free-forms and some descriptors used in differential geometry can be used to describe them applying the principles of feature extraction developed for computer vision and pattern recognition. The first part of this study focused on building the protein dataset using a simulation tool and performing feature extraction using novel geometrical descriptors. The second part tested the method on two examples, first involved a classification of tubulin isotypes and the second compared tubulin with the FtsZ protein, which is its bacterial analog. An additional test involved several unrelated proteins. Different classification methodologies have been used: a classic approach with a support vector machine (SVM) classifier and an unsupervised learning with a k-means approach. The best result was obtained with SVM and the radial basis function kernel. The results are significant and competitive with the state-of-the-art protein classification methods. This leads to a new methodological direction in protein structure analysis.
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    Revealing and attenuating the electrostatic properties of tubulin and its polymers
    (2021) Kalra, Aarat P.; Patel, Sahil D.; Eakins, Boden B.; Riddell, Saralyn; Kumar, Pawan; Winter, Philip; Preto, Jordane; Carlson, Kris W.; Lewis, John D.; Rezania, Vahid; Tuszynski, Jack A.; Shankar, Karthik
    Tubulin is an electrostatically negative protein that forms cylindrical polymers termed microtubules, which are crucial for a variety of intracellular roles. Exploiting the electrostatic behavior of tubulin and microtubules within functional microfluidic and optoelectronic devices is limited due to the lack of understanding of tubulin behavior as a function of solvent composition. This work displays the tunability of tubulin surface charge using dimethyl sulfoxide (DMSO) for the first time. Increasing the DMSO volume fractions leads to the lowering of tubulin's negative surface charge, eventually causing it to become positive in solutions >80% DMSO. As determined by electrophoretic mobility measurements, this change in surface charge is directionally reversible, i.e., permitting control between −1.5 and + 0.2 cm2 (V s)−1. When usually negative microtubules are exposed to these conditions, the positively charged tubulin forms tubulin sheets and aggregates, as revealed by an electrophoretic transport assay. Fluorescence-based experiments also indicate that tubulin sheets and aggregates colocalize with negatively charged g-C3N4 sheets while microtubules do not, further verifying the presence of a positive surface charge. This study illustrates that tubulin and its polymers, in addition to being mechanically robust, are also electrically tunable.
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    All wired up: an exploration of the electrical properties of microtubules and tubulin
    (2020) Kalra, Aarat P.; Eakins, Boden B.; Patel, Sahil D.; Ciniero, Gloria; Rezania, Vahid; Shankar, Karthik; Tuszynski, Jack A.
    Microtubules are hollow, cylindrical polymers of the protein α, β tubulin, that interact mechanochemically with a variety of macromolecules. Due to their mechanically robust nature, microtubules have gained attention as tracks for precisely directed transport of nanomaterials within lab-on-a-chip devices. Primarily due to the unusually negative tail-like C-termini of tubulin, recent work demonstrates that these biopolymers are also involved in a broad spectrum of intracellular electrical signaling. Microtubules and their electrostatic properties are discussed in this Review, followed by an evaluation of how these biopolymers respond mechanically to electrical stimuli, through microtubule migration, electrorotation and C-termini conformation changes. Literature focusing on how microtubules act as nanowires capable of intracellular ionic transport, charge storage, and ionic signal amplification is reviewed, illustrating how these biopolymers attenuate ionic movement in response to electrical stimuli. The Review ends with a discussion on the important questions, challenges, and future opportunities for intracellular microtubule-based electrical signaling.
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    A revised shock history for the youngest unbrecciated lunar basalt – Northwest Africa 032
    (2020) Mijajlovic, Tatiana; Xue, Xie; Walton, Erin L.
    Northwest Africa (NWA) 032 is considered to be the youngest radiometrically-dated mare basalt, with concordant Rb-Sr and Sm-Nd ages of 2.947 ± 0.016 Ga and 2.931 ± 0.092, respectively [1]. These ages are ~175 Ma older than those from 40Ar39Ar (2.779 ± 0.014 Ga) [2]. NWA 032 contains a high modal abundance of pyroxene (50.7 vol%), plagioclase (29.4 vol%), and olivine (11.3 vol%) [3]. The texture is that of an unbrecciated olivine-pyroxene phyric basalt. Olivine phenocrysts are zoned with Mg rich cores (Fo34-50) and thin, discontinuous Fe-rich rims (Fo30). Fine grained (≤ 1μm) elongated, tapered plagioclase crystals (An80-90) are present within the groundmass, interspersed with pyroxene (En1-25Wo15-25) of similar shape and size. These two minerals occur in a plumose texture, radiating from a common nucleation point. Pyroxene may be categorized based on grain size as either groundmass (<1 μm), intermediate crystals (~50 μm) or larger phenocrysts (~100 μm) [3]. The mineralogy of NWA 032 makes it ideal for the study and classification of shock features based on the updated shock classification scheme [4], which relies on petrographic observations of deformation and transformation in olivine, pyroxene and plagioclase – the three most abundant minerals in NWA 032. A previous description of shock effects in NWA 032 allowed for a shock pressure estimate of ~40-60 GPa [3]; however, the shock state of plagioclase feldspar (shock-amorphized vs crystalline) was inconclusive, owing to the fine grain size of this mineral (≤1μm). The purpose of our study is to characterize the shock deformation and transformation effects in NWA 032 using a combination of field emission scanning electron microscopy (FESEM) and Raman spectroscopy, focusing on the shock state of feldspar, as well as characterizing the crystallization products of shock melting. The latter have been demonstrated as useful criteria to evaluate shock conditions [5]. Our results more tightly constrain the shock history experienced by NWA 032.