Quantification of ammonia binding sites in Davison (Type 3A) zeolite desiccant : a solid-state Nitrogen-15 MAS NMR spectroscopy investigation.

The quantitative analysis of ammonia binding sites in the Davison (Type 3A) zeolite desiccant using solid-state {sup 15}N MAS NMR spectroscopy is reported. By utilizing 15N enriched ammonia ({sup 15}NH{sub 3}) gas, the different adsorption/binding sites within the zeolite were investigated as a function of NH{sub 3} loading. Using {sup 15}N MAS NMR multiple sites were resolved that have distinct cross-polarization dynamics and chemical shift behavior. These differences in the {sup 15}N NMR were used to characterize the adsorption environments in both the pure 3A zeolite and the silicone-molded forms of the desiccant

Hybrid Lipids Inspired by Extremophiles and Eukaryotes Afford Serum‐Stable Membranes with Low Leakage

This paper presents a new hybrid lipid that fuses the ideas of molecular tethering of lipid tails used by archaea and the integration of cholesterol groups used by eukaryotes, thereby leveraging two strategies employed by nature to increase lipid packing in membranes. Liposomes comprised of pure hybrid lipids exhibited a 5–30‐fold decrease in membrane leakage of small ions and molecules compared to liposomes that used only one strategy (lipid tethering or cholesterol incorporation) to increase membrane integrity. Molecular dynamics simulations reveal that tethering of lipid tails and integration of cholesterol both reduce the disorder in lipid tails and time‐dependent variance in area per lipid within a membrane, leading to tighter lipid packing. These hybrid lipid membranes have exceptional stability in serum, yet can support functional ion channels, can serve as a substrate for phospholipase enzymes, and can be used for liposomal delivery of molecules into living cells.Hybrid synthetic lipids with dramatically reduced leakage properties incorporate many structural features used by Nature to generate stable membranes. Covalent attachment of cholesterol groups to membrane‐spanning tetraether lipids makes it possible to generate stable liposomes with low permeability, while retaining the possibility to support functional biomolecules and deliver liposome‐encapsulated molecules to living cells.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137415/1/chem201701378.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137415/2/chem201701378-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137415/3/chem201701378_am.pd

Structural characterization of nanofiber silk produced by embiopterans (webspinners)

Embiopterans produce silken galleries and sheets using exceptionally fine silk fibers in which they live and breed. In this study, we use electron microscopy (EM), Fourier-transform infrared (FT-IR) spectroscopy, wide angle X-ray diffraction (WAXD) and solid-state nuclear magnetic resonance (ssNMR) techniques to elucidate the molecular level protein structure of webspinner (embiid) silks. Silks from two species Antipaluria urichi and Aposthonia ceylonica are studied in this work. Electron microscopy images show that the fibers are about 90–100 nm in diameter, making webspinner silks among the finest of all known animal silks. Structural studies reveal that the silk protein core is dominated by β-sheet structures, and that the protein core is coated with a hydrophobic alkane-rich surface coating. FTIR spectra of native embiid silk shows characteristic alkane CH2 stretchings near 2800–2900 cm−1, which decrease approximately 50% after washing the silk with 2 : 1 CHCl3 : MeOH. Furthermore, 13C ssNMR data shows a significant CH2 resonance that is strongly affected by the presence of water, supporting the idea that the silk fibers are coated with a hydrocarbon-rich layer. Such a layer is likely used to protect the colonies from rain. FTIR data also suggests that embiid silks are dominated by β-sheet secondary structures similar to spider and silkworm silk fibers. NMR data confirms the presence of β-sheet nanostructures dominated by serine-rich repetitive regions. A deconvolution of the serine Cβ NMR resonance reveals that approximately 70% of all seryl residues exist in a β-sheet structure. This is consistent with WAXD results that suggest webspinner silks are 70% crystalline, which is the highest crystalline fraction reported for any animal silks. The work presented here provides a molecular level structural picture of silk fibers produced by webspinners

Tools for characterizing biomembranes : final LDRD report.

A suite of experimental nuclear magnetic resonance (NMR) spectroscopy tools were developed to investigate lipid structure and dynamics in model membrane systems. By utilizing both multinuclear and multidimensional NMR experiments a range of different intra- and inter-molecular contacts were probed within the membranes. Examples on pure single component lipid membranes and on the canonical raft forming mixture of DOPC/SM/Chol are presented. A unique gel phase pretransition in SM was also identified and characterized using these NMR techniques. In addition molecular dynamics into the hydrogen bonding network unique to sphingomyelin containing membranes were evaluated as a function of temperature, and are discussed

Satellite-derived increases in net primary productivity across North America, 1982-1998

We used a new 17‐year, high spatial resolution satellite record and a carbon cycle model to explore how changing net primary productivity (NPP) contributed to a proposed carbon (C) sink in North America. We found a small but significant increase in NPP, 0.03 Pg C yr^(−2) or 8% over 17 years, that could explain a substantial fraction of the C sink. The largest increases occurred in the central and southeastern United States, eastern Canada, and northwestern North America, and were consistent with NPP trends derived from forest inventories and crop yields. Interannual NPP variability was small, implying that the large interannual variability in the C sink found in previous studies were driven by changes in heterotrophic respiration

Selective One-Dimensional \u3csup\u3e13\u3c/sup\u3eC-\u3csup\u3e13\u3c/sup\u3eC Spin-Diffusion Solid-State Nuclear Magnetic Resonance Methods to Probe Spatial Arrangements in Biopolymers including Plant Cell Walls, Peptides, and Spider Silk

© 2020 American Chemical Society. All rights reserved. Two-dimensional (2D) and 3D through-space 13C-13C homonuclear spin-diffusion techniques are powerful solid-state nuclear magnetic resonance (NMR) tools for extracting structural information from 13C-enriched biomolecules, but necessarily long acquisition times restrict their applications. In this work, we explore the broad utility and underutilized power of a chemical shift-selective one-dimensional (1D) version of a 2D 13C-13C spin-diffusion solid-state NMR technique. The method, which is called 1D dipolar-assisted rotational resonance (DARR) difference, is applied to a variety of biomaterials including lignocellulosic plant cell walls, microcrystalline peptide fMLF, and black widow dragline spider silk. 1D 13C-13C spin-diffusion methods described here apply in select cases in which the 1D 13C solid-state NMR spectrum displays chemical shift-resolved moieties. This is analogous to the selective 1D nuclear Overhauser effect spectroscopy (NOESY) experiment utilized in liquid-state NMR as a faster (1D instead of 2D) and often less ambiguous (direct sampling of the time domain data, coupled with increased signal averaging) alternative to 2D NOESY. Selective 1D 13C-13C spin-diffusion methods are more time-efficient than their 2D counterparts such as proton-driven spin diffusion (PDSD) and dipolar-assisted rotational resonance. The additional time gained enables measurements of 13C-13C spin-diffusion buildup curves and extraction of spin-diffusion time constants TSD, yielding detailed structural information. Specifically, selective 1D DARR difference buildup curves applied to 13C-enriched hybrid poplar woody stems confirm strong spatial interaction between lignin and acetylated xylan polymers within poplar plant secondary cell walls, and an interpolymer distance of ∼0.45-0.5 nm was estimated. Additionally, Tyr/Gly long-range correlations were observed on isotopically enriched black widow spider dragline silks

Howard's War on Terror: A Conceivable, Communicable and Coercive Foreign Policy Discourse

This article explores the relationship between language and political possibility. It is argued that John Howard’s language from 11 September 2001 to mid 2003 helped to enable the ‘War on Terror’ in an Australian context in three principal ways. Firstly, through contingent and contestable constructions of Australia, the world and their relationship, Howard’s language made interventionism conceivable. Secondly, emphasising shared values, mateship and mutual sacrifice in war, Howard embedded his foreign policy discourse in the cultural terrain of ‘mainstream Australia’, specifically framing a foreign policy discourse that was communicable to ‘battlers’ and disillusioned ‘Hansonites’. Thirdly, positioning alternatives as ‘un-Australian’, Howard’s language was particularly coercive, silencing potential oppositional voices

Satellite-derived increases in net primary productivity across North America, 1982-1998

We used a new 17‐year, high spatial resolution satellite record and a carbon cycle model to explore how changing net primary productivity (NPP) contributed to a proposed carbon (C) sink in North America. We found a small but significant increase in NPP, 0.03 Pg C yr^(−2) or 8% over 17 years, that could explain a substantial fraction of the C sink. The largest increases occurred in the central and southeastern United States, eastern Canada, and northwestern North America, and were consistent with NPP trends derived from forest inventories and crop yields. Interannual NPP variability was small, implying that the large interannual variability in the C sink found in previous studies were driven by changes in heterotrophic respiration

phot1 inhibition of ABCB19 primes lateral auxin fluxes in the shoot apex required for phototropism

It is well accepted that lateral redistribution of the phytohormone auxin underlies the bending of plant organs towards light. In monocots, photoreception occurs at the shoot tip above the region of differential growth. Despite more than a century of research, it is still unresolved how light regulates auxin distribution and where this occurs in dicots. Here, we establish a system in Arabidopsis thaliana to study hypocotyl phototropism in the absence of developmental events associated with seedling photomorphogenesis. We show that auxin redistribution to the epidermal sites of action occurs at and above the hypocotyl apex, not at the elongation zone. Within this region, we identify the auxin efflux transporter ATP-BINDING CASSETTE B19 (ABCB19) as a substrate target for the photoreceptor kinase PHOTOTROPIN 1 (phot1). Heterologous expression and physiological analyses indicate that phosphorylation of ABCB19 by phot1 inhibits its efflux activity, thereby increasing auxin levels in and above the hypocotyl apex to halt vertical growth and prime lateral fluxes that are subsequently channeled to the elongation zone by PIN-FORMED 3 (PIN3). Together, these results provide new insights into the roles of ABCB19 and PIN3 in establishing phototropic curvatures and demonstrate that the proximity of light perception and differential phototropic growth is conserved in angiosperm

Potential climatic transitions with profound impact on Europe

We discuss potential transitions of six climatic subsystems with large-scale impact on Europe, sometimes denoted as tipping elements. These are the ice sheets on Greenland and West Antarctica, the Atlantic thermohaline circulation, Arctic sea ice, Alpine glaciers and northern hemisphere stratospheric ozone. Each system is represented by co-authors actively publishing in the corresponding field. For each subsystem we summarize the mechanism of a potential transition in a warmer climate along with its impact on Europe and assess the likelihood for such a transition based on published scientific literature. As a summary, the ‘tipping’ potential for each system is provided as a function of global mean temperature increase which required some subjective interpretation of scientific facts by the authors and should be considered as a snapshot of our current understanding. <br/