Soil organic matter (SOM) is correlated with reactive iron (Fe) in humid soils, but Fe also promotes SOM decomposition when oxygen (O
) becomes limited. Here we quantify Fe-mediated OM protection vs. ...decomposition by adding
C dissolved organic matter (DOM) and
Fe
to soil slurries incubated under static or fluctuating O
. We find Fe uniformly protects OM only under static oxic conditions, and only when Fe and DOM are added together: de novo reactive Fe
phases suppress DOM and SOM mineralization by 35 and 47%, respectively. Conversely, adding
Fe
alone increases SOM mineralization by 8% following oxidation to
Fe
. Under O
limitation, de novo reactive
Fe
phases are preferentially reduced, increasing anaerobic mineralization of DOM and SOM by 74% and 32‒41%, respectively. Periodic O
limitation is common in humid soils, so Fe does not intrinsically protect OM; rather reactive Fe phases require their own physiochemical protection to contribute to OM persistence.
Structural studies of human G protein-coupled receptors (GPCRs) have recently been accelerated through the use of a fusion partner that was inserted into the third intracellular loop. Using chimeras ...of the human β2-adrenergic and human A2A adenosine receptors, we present the methodology and data for the initial selection of an expanded set of fusion partners for crystallizing GPCRs. In particular, use of the thermostabilized apocytochrome b562RIL as a fusion partner displays certain advantages over previously utilized fusion proteins, resulting in a significant improvement in stability and structure of GPCR-fusion constructs.
► A method was developed for the selection of fusion domains for GPCR crystallization ► Apocytochrome b562RIL has advantages over previously utilized T4 lysozyme ► Diffraction quality crystals of two engineered GPCRs were successfully grown ► The method led to the crystal structure of the A2A adenosine receptor at 1.8 Å
Pharmacological responses of G protein-coupled receptors (GPCRs) can be fine-tuned by allosteric modulators. Structural studies of such effects have been limited due to the medium resolution of GPCR ...structures. We reengineered the human A 2A adenosine receptor by replacing its third intracellular loop with apocytochrome b⁵⁶² RIL and solved the structure at 1.8 angstrom resolution. The high-resolution structure allowed us to identify 57 ordered water molecules inside the receptor comprising three major clusters. The central cluster harbors a putative sodium ion bound to the highly conserved aspartate residue Asp 2.50 . Additionally, two cholesterols stabilize the conformation of helix VI, and one of 23 ordered lipids intercalates inside the ligand-binding pocket. These high-resolution details shed light on the potential role of structured water molecules, sodium ions, and lipids/cholesterol in GPCR stabilization and function.
Introduction: Systemic inflammation may be one of the mechanisms mediating the association between ambient air pollution and cardiovascular morbidity and mortality. Interleukin-6 (IL-6) and ...fibrinogen are biomarkers of systemic inflammation that are independent risk factors for cardiovascular disease. Objective: We investigated the association between ambient air pollution and systemic inflammation using baseline measurements of IL-6 and fibrinogen from controlled human exposure studies. Methods: In this retrospective analysis we used repeated-measures data in 45 nonsmoking subjects. Hourly and daily moving averages were calculated for ozone, nitrogen dioxide, sulfur dioxide, and particulate matter ≤ 2.5 µm in aerodynamic diameter ($PM_{2.5}$). Linear mixed-model regression determined the effects of the pollutants on systemic IL-6 and fibrinogen. Effect modification by season was considered. RESULTS: We observed a positive association between IL-6 and O₃ 0.31 SD per O₃ interquartile range (IQR); 95% confidence interval (CI), 0.08-0.54 and between IL-6 and SO₃ (0.25 SD per SO₂ IQR; 95% CI, 0.06-0.43). We observed the strongest effects using 4-day moving averages. Responses to pollutants varied by season and tended to be higher in the summer, particularly for O₃ and$PM_{2.5}$. Fibrinogen was not associated with pollution. Conclusions: This study demonstrates a significant association between ambient pollutant levels and baseline levels of systemic IL-6. These findings have potential implications for controlled human exposure studies. Future research should consider whether ambient pollution exposure before chamber exposure modifies IL-6 response.
Ferric iron (FeIII) solid phases serve many functions in soils and sediments, which include providing sorption sites for soil organic matter, nutrients, and pollutants. The reactivity of Fe solid ...phases depends on the mineral structure, including the overall crystallinity. In redox-active soils and sediments, repeated reductive dissolution with subsequent exposure to aqueous ferrous iron (Fe2+) and oxidative re-precipitation can alter Fe phase crystallinity and reactivity. However, the trajectory of Fe mineral transformation under redox fluctuations is unclear and has been reported to result in both increases and decreases in Fe phase crystallinity. Several factors such as water budget, organic matter input, redox dynamics as well as the initial Fe phase composition might play a role. The objective of our study was to examine if Fe minerals in soils that differ in porosity-dependent water leaching rate and initial Fe phase crystallinity, demonstrate distinct mineral transformations when subjected to redox fluctuations. We sampled paired plots of two soil types under similar management but with different water leaching rates and contrasting Fe oxide crystallinity — an Alisol rich in crystalline Fe phases and an Andosol rich in short-range-ordered (SRO) Fe phases. The two soils were either exposed to several decades of redox fluctuations during rice paddy cultivation (paddy) or to predominantly oxic conditions in neighboring vegetable gardens (non-paddy). Paddy soils are uniquely suited for this type of study because they are regularly submerged and develop regular redox fluctuations. We also incubated the non-paddy soils in the laboratory for one year through eight anoxic/oxic cycles and monitored the aqueous soil geochemistry. Mössbauer spectroscopy was then used to evaluate Fe mineral speciation in field soils (paddy and non-paddy) and laboratory incubations. In the field soils, we found that redox fluctuation had contrasting effects on Fe oxide crystallinity, with crystallinity being lower in the Alisol paddy soil and higher in the Andosol paddy soil than in their corresponding non-paddy controls. In the laboratory incubation experiment, Eh, pH and dissolved Fe2+ responded as anticipated, with elevated Fe2+ concentrations during the anoxic periods as well as low Eh and high pH. Mössbauer measurements suggest the fluctuating redox incubation was beginning to alter Fe oxide crystallinity along the same trajectory as observed in the field, but the changes were within the range of fitting errors. We propose that reductive dissolution of crystalline Fe oxides prevails in the soil rich in crystalline Fe oxides (Alisol) and that re-precipitation as SRO Fe oxides is favored by constrained leaching, which leads to the observed decrease in Fe oxide crystallinity. In the soil rich in SRO Fe phases (Andosol), preferential reductive dissolution of SRO Fe oxides coupled with stronger leaching of dissolved Fe2+ causes the observed relative increase in crystallinity of the remaining Fe oxides. The observed increase in Fe oxide crystallinity may further be a result of Fe(II)-catalyzed re-crystallization of SRO Fe oxides. These findings indicate that, besides other factors, the Fe mineral composition of the initial soil or sediment as well as the leaching rate likely influence the trajectory of Fe oxide evolution under alternating redox-conditions.
Opioids represent widely prescribed and abused medications, although their signal transduction mechanisms are not well understood. Here we present the 1.8 Å high-resolution crystal structure of the ...human δ-opioid receptor (δ-OR), revealing the presence and fundamental role of a sodium ion in mediating allosteric control of receptor functional selectivity and constitutive activity. The distinctive δ-OR sodium ion site architecture is centrally located in a polar interaction network in the seven-transmembrane bundle core, with the sodium ion stabilizing a reduced agonist affinity state, and thereby modulating signal transduction. Site-directed mutagenesis and functional studies reveal that changing the allosteric sodium site residue Asn 131 to an alanine or a valine augments constitutive β-arrestin-mediated signalling. Asp95Ala, Asn310Ala and Asn314Ala mutations transform classical δ-opioid antagonists such as naltrindole into potent β-arrestin-biased agonists. The data establish the molecular basis for allosteric sodium ion control in opioid signalling, revealing that sodium-coordinating residues act as 'efficacy switches' at a prototypic G-protein-coupled receptor.
The diversity of ownership of forestlands in the Northwoods Region and the absence of strong local land use regulations represent critical barriers to protecting the health of natural resources. Seen ...by policymakers as a viable land protection strategy, conservation easements represent a voluntary alternative to land use regulation for forest land conservation. However, landowner adoption for privately owned forest lands remains low in Wisconsin despite more than 16 million acres nationally held by nonprofit state, local, and national land trust organizations. Despite these successes, resistance exists from non-industrial private forest landowners to the adoption of conservation easements. This study explores these barriers using data collected from mail survey responses from 470 forest landowners in Wisconsin's Northwoods. A typology of landowners is developed based on attitudes toward the adoption of conservation easements, revealing that current interest among forest landowners is below 20%, and land trusts currently lack standing as trusted partners in forest land management.
OBJECTIVE:The aim of this study was to assess the impact of a new workers’ compensation medical assessment model on loss of earnings (LOE) benefits duration.
METHODS:A medical assessment model was ...introduced incorporating return to work planning and inclusion of the workerʼs treating physician. Impact of the program on LOE benefit duration was assessed using a quasi-experimental pre–post study design. Cox PH multivariable regression was adjusted for age, gender, injury severity, time to referral, and industry.
RESULTS:The study population comprised 3146 workers1794 assessed pre-intervention and 1574 assessed after introduction of the new model. There was a significant reduction in LOE benefit duration for workers assessed in the new model (hazard ratio 1.33, 95% confidence interval 1.23–1.43).
CONCLUSIONS:The probability of being off LOE benefits for workers assessed in the new program was 33% greater than for workers assessed in the prior program.
Beyond clay Rasmussen, Craig; Heckman, Katherine; Wieder, William R. ...
Biogeochemistry,
02/2018, Letnik:
137, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Improved quantification of the factors controlling soil organic matter (SOM) stabilization at continental to global scales is needed to inform projections of the largest actively cycling terrestrial ...carbon pool on Earth, and its response to environmental change. Biogeochemical models rely almost exclusively on clay content to modify rates of SOM turnover and fluxes of climate-active CO₂ to the atmosphere. Emerging conceptual understanding, however, suggests other soil physicochemical properties may predict SOM stabilization better than clay content. We addressed this discrepancy by synthesizing data from over 5,500 soil profiles spanning continental scale environmental gradients. Here, we demonstrate that other physicochemical parameters are much stronger predictors of SOM content, with clay content having relatively little explanatory power. We show that exchangeable calcium strongly predicted SOM content in water-limited, alkaline soils, whereas with increasing moisture availability and acidity, iron- and aluminum-oxyhydroxides emerged as better predictors, demonstrating that the relative importance of SOM stabilization mechanisms scales with climate and acidity. These results highlight the urgent need to modify biogeochemical models to better reflect the role of soil physicochemical properties in SOM cycling.
PDF
