| 1. |
- Shumilova, Oleksandra, et al.
(författare)
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Simulating rewetting events in intermittent rivers and ephemeral streams : A global analysis of leached nutrients and organic matter
- 2019
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Ingår i: Global Change Biology. - : WILEY. - 1354-1013 .- 1365-2486. ; 25:5, s. 1591-1611
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Tidskriftsartikel (refereegranskat)abstract
- Climate change and human pressures are changing the global distribution and the extent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico-chemical changes (preconditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experimentally simulated, under standard laboratory conditions, rewetting of leaves, riverbed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative characteristics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dissolved substances during rewetting events (56%-98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contributed most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached OM. The opposite pattern was found in the arid zone. Environmental variables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached substances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying events.
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| 2. |
- Costello, David M., et al.
(författare)
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Global patterns and controls of nutrient immobilization on decomposing cellulose in riverine ecosystems
- 2022
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Ingår i: Global Biogeochemical Cycles. - : John Wiley & Sons. - 0886-6236 .- 1944-9224. ; 36:3
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Tidskriftsartikel (refereegranskat)abstract
- Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low-nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low-nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature-dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature. Collectively, we demonstrated that exogenous nutrient supply and immobilization are critical control points for decomposition of organic matter.
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| 3. |
- Megido, Loerto, et al.
(författare)
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Understanding and utilizing the biomolecule/nanosystems interface: Soft materials and coatings for controlled drug release
- 2017
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Ingår i: Nanotechnologies in Preventive and Regenerative Medicine: An Emerging Big Picture. - 9780323480642 ; , s. 244-260
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Combining biomolecules with materials used in medicine allows for local control of the biological response and can be used for modulating the host immune response, a major challenge in the efficacy of many medical devices. In Subchapter 3.1, we will review different methods used to attach biomolecules to materials, focusing on protein conjugation methods. We will begin by describing noncovalent immobilization strategies, including encapsulation within biomaterials and adsorption to material surfaces. We will then discuss strategies to covalently attach biomolecules to materials via the use of specific functional groups, thus enhancing the stability of the interaction. Finally, we will describe emerging methods to site specifically immobilize biomolecules to materials such that proteins are presented in an oriented manner, improving their overall functionality. Throughout the subchapter, we will emphasize the advantages and disadvantages of each technique, successes achieved, as well as the challenges remaining in this growing field.During last years, increasing development of nanoparticles as targeted drug delivery agents, has led to a wide amount of studies involving their characterization to the application as novel therapeutic agents. Hence, the nanoparticles interact with biological environments when they enter in the human body, and then proteins bind to the nanomaterial surface forming the protein corona. Protein corona has a great relevance in the interaction and function of the nanoparticle-drug conjugates. In fact, its characterization is one of the main challenges for nanoscience development. Herein, it is reviewed the main proteomic methods described for quantify and qualify the protein corona formed around nanoparticles to better understand the process of interaction with the biological media, and to decipher key parameters to control the effects of the protein corona.In Subchapter 3.3, the structure and working principles of coatings for controlled drug release in oral drug administration are presented. The release mechanisms, including diffusion, dissolution, osmotic pumping, and swelling are described. The soft materials used in the majority of controlled drug release formulations are natural and synthetic polymers. They are presented here and examples of specific polymers applied in controlled release formulations are provided. There is also a section containing characterization of soft materials using in situ electron microscopy for studying water transport through coatings at high-spatial resolution. The reason for this is that the detailed properties and release mechanisms of the controlled release depend on the material nanostructure. The in situ characterization gives access not only the information about the nanostructure but also the direct correlation between structure and properties on different length scales. Finally, an overview of the present major challenges and future possibilities concerning controlled drug release formulations is presented.Targeting cancer cells with functional nanoprobes possessing a targeting drug unit and an imaging moiety carries great potential for early detection, accurate diagnosis, and targeted therapy of various diseases. Given their nanoscopic dimensions, ultrasmall particles ( < 100nm) are in general well suited for interactions with the cells; however, the current challenge of the nanomedicine is to transform inorganic nanoparticles of metals (e.g., gold) or metal oxide (e.g., magnetite) into signal-generating vectors. Engineered nanostructures can act as vehicles for a large number of signaling centers and/or targeting units thereby offering unique opportunity to enhance the sensitivity by locally enhancing the density of signal groups. For this purpose, creation of surface groups enabling chemical attachment of antibodies or other targeting biomolecules are essential that will allow the delivery of therapeutic payloads to the diseased sites. Multimodal nanoprobes functionalized with different diagnostic and therapeutic options within a single nanoparticle followed by their functionalization with organic ligands and biomolecules can provide specific uptake and high sensitivity toward anatomical information. However, the vision of making clinical theranostics a routine clinical procedure is encumbered by limited stability of complex nanoparticles in biological milieu and lack of standardization of therapy response. Despite the widely acclaimed advantages of integrating diagnostic imaging, drug delivery, and therapeutic monitoring in a single nanotheranostic probe, the clinical utilization of engineered nanoprobes demands concerted efforts in the domains of nanoparticle and surface chemistry/charge, new chelator ligands, pharmaceutical technology, radioactive labeling of nanovectors, biokinetics, and pharmacodynamics of nanoprobes, and biological tests (cell tests and animal models).
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| 4. |
- Tiegs, Scott D., et al.
(författare)
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Global patterns and drivers of ecosystem functioning in rivers and riparian zones
- 2019
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Ingår i: Science Advances. - Washington : American Association of Advancement in Science. - 2375-2548. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth's biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented "next-generation biomonitoring" by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.
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