Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 4 of 4
Full-Text Articles in Entire DC Network
Interplay Of Hydrogen Bonds And N→Π* Interactions In Proteins, Gail J. Bartlett, Robert W. Newberry, Brett Vanveller, Ronald T. Raines, Derek N. Woolfson
Interplay Of Hydrogen Bonds And N→Π* Interactions In Proteins, Gail J. Bartlett, Robert W. Newberry, Brett Vanveller, Ronald T. Raines, Derek N. Woolfson
Brett VanVeller
Protein structures are stabilized by multiple weak interactions, including the hydrophobic effect, hydrogen bonds, electrostatic effects, and van der Waals interactions. Among these interactions, the hydrogen bond is distinct in having its origins in electron delocalization. Recently, another type of electron delocalization, the n→π* interaction between carbonyl groups, has been shown to play a role in stabilizing protein structure. Here we examine the interplay between hydrogen bonding and n→π* interactions. To address this issue, we used data available from high-resolution protein crystal structures to interrogate asparagine side-chain oxygen atoms that are both acceptors of a hydrogen bond and donors of …
Iron Oxidation Stimulates Organic Matter Decomposition In Humid Tropical Forest Soils, Steven J. Hall, Whendee L. Silver
Iron Oxidation Stimulates Organic Matter Decomposition In Humid Tropical Forest Soils, Steven J. Hall, Whendee L. Silver
Steven J. Hall
Humid tropical forests have the fastest rates of organic matter decomposition globally, which often coincide with fluctuating oxygen (O2) availability in surface soils. Microbial iron (Fe) reduction generates reduced iron [Fe(II)] under anaerobic conditions, which oxidizes to Fe(III) under subsequent aerobic conditions. We demonstrate that Fe (II) oxidation stimulates organic matter decomposition via two mechanisms: (i) organic matter oxidation, likely driven by reactive oxygen species; and (ii) increased dissolved organic carbon (DOC) availability, likely driven by acidification. Phenol oxidative activity increased linearly with Fe(II) concentrations (P < 0.0001, pseudo R2 = 0.79) in soils sampled within and among five tropical forest sites. A similar pattern occurred in the absence of soil, suggesting an abiotic driver of this reaction. No phenol oxidative activity occurred in soils under anaerobic conditions, implying the importance of oxidants such as O2 or hydrogen peroxide (H2O2) in addition to Fe(II). Reactions between Fe(II) and H2O2 generate hydroxyl radical, a strong nonselective oxidant of organic compounds. We found increasing consumption of H2O2 as soil Fe(II) concentrations increased, suggesting that reactive oxygen species produced by Fe(II) oxidation explained variation in phenol oxidative activity among samples. Amending soils with Fe(II) at field concentrations stimulated short-term C mineralization by up to 270%, likely via a second mechanism. Oxidation of Fe(II) drove a decrease in pH and a monotonic increase in DOC; a decline of two pH units doubled DOC, likely stimulating microbial respiration. We obtained similar results by manipulating soil acidity independently of Fe(II), implying that Fe(II) oxidation affected C substrate availability via pH fluctuations, in addition to producing reactive oxygen species. Iron oxidation coupled to organic matter decomposition contributes to rapid rates of C cycling across humid tropical forests in spite of periodic O2 limitation, and may help explain the rapid turnover of complex C molecules in these soils.
When Wet Gets Wetter: Decoupling Of Moisture, Redox Biogeochemistry, And Greenhouse Gas Fluxes In A Humid Tropical Forest Soil, Steven J. Hall, William H. Mcdowell, Whendee L. Silver
When Wet Gets Wetter: Decoupling Of Moisture, Redox Biogeochemistry, And Greenhouse Gas Fluxes In A Humid Tropical Forest Soil, Steven J. Hall, William H. Mcdowell, Whendee L. Silver
Steven J. Hall
Upland humid tropical forest soils are often characterized by fluctuating redox dynamics that vary temporally and spatially across the landscape. An increase in the frequency and intensity of rainfall events with climate change is likely to affect soil redox reactions that control the production and emissions of greenhouse gases. We used a 24-day rainfall manipulation experiment to evaluate temporal and spatial trends of surface soil (0–20 cm) redox-active chemical species and greenhouse gas fluxes in the Luquillo Experimental Forest, Puerto Rico. Treatments consisted of a high rainfall simulation (60 mm day-1), a fluctuating rainfall regime, and a control. Water addition …
Emerging Technologies For Non-Invasive Quantification Of Physiological Oxygen Transport In Plants, P. Chaturvedi, M. Taguchi, S. L. Burrs, B. A. Hauser, W.W. A.W. Salim, Jonathan C. Claussen, E. S. Mclamore
Emerging Technologies For Non-Invasive Quantification Of Physiological Oxygen Transport In Plants, P. Chaturvedi, M. Taguchi, S. L. Burrs, B. A. Hauser, W.W. A.W. Salim, Jonathan C. Claussen, E. S. Mclamore
Jonathan C. Claussen
Oxygen plays a critical role in plant metabolism, stress response/signaling, and adaptation to environmental changes (Lambers and Colmer, Plant Soil 274:7-15, 2005; Pitzschke et al., Antioxid Redox Signal 8:1757-1764, 2006; Van Breusegem et al., Plant Sci 161:405-414, 2001). Reactive oxygen species (ROS), by-products of various metabolic pathways in which oxygen is a key molecule, are produced during adaptation responses to environmental stress. While much is known about plant adaptation to stress (e.g., detoxifying enzymes, antioxidant production), the link between ROS metabolism, O2 transport, and stress response mechanisms is unknown. Thus, non-invasive technologies for measuring O2 are critical for understanding the …