Microbial decomposition processes and vulnerable arctic soil organic carbon in the 21st century

Various levels of representations of biogeochemical processes in current biogeochemistry models contribute to a large uncertainty in carbon budget quantification. Here, we present an uncertainty analysis with a process-based biogeochemistry model, the Terrestrial Ecosystem Model (TEM), into which detailed microbial mechanisms were incorporated. Ensemble regional simulations with the new model (MIC-TEM) estimated that the carbon budget of the arctic ecosystems is 76.0±114.8&thinsp;Pg&thinsp;C during the 20th century, i.e., −3.1±61.7&thinsp;Pg&thinsp;C under the RCP 2.6 scenario and 94.7±46&thinsp;Pg&thinsp;C under the RCP 8.5 scenario during the 21st century. Positive values indicate the regional carbon sink while negative values are a source to the atmosphere. Compared to the estimates using a simpler soil decomposition algorithm in TEM, the new model estimated that the arctic terrestrial ecosystems stored 12&thinsp;Pg less carbon over the 20th century, i.e., 19 and 30&thinsp;Pg&thinsp;C less under the RCP 8.5 and RCP 2.6 scenarios, respectively, during the 21st century. When soil carbon within depths of 30, 100, and 300&thinsp;cm was considered as initial carbon in the 21st century simulations, the region was estimated to accumulate 65.4, 88.6, and 109.8&thinsp;Pg&thinsp;C, respectively, under the RCP 8.5 scenario. In contrast, under the RCP 2.6 scenario, the region lost 0.7, 2.2, and 3&thinsp;Pg&thinsp;C, respectively, to the atmosphere. We conclude that the future regional carbon budget evaluation largely depends on whether or not adequate microbial activities are represented in earth system models and on the sizes of soil carbon considered in model simulations.</p

KDM2B/FBXL10 targets c-Fos for ubiquitylation and degradation in response to mitogenic stimulation.

KDM2B (also known as FBXL10) controls stem cell self-renewal, somatic cell reprogramming and senescence, and tumorigenesis. KDM2B contains multiple functional domains, including a JmjC domain that catalyzes H3K36 demethylation and a CxxC zinc-finger that recognizes CpG islands and recruits the polycomb repressive complex 1. Here, we report that KDM2B, via its F-box domain, functions as a subunit of the CUL1-RING ubiquitin ligase (CRL1/SCF(KDM2B)) complex. KDM2B targets c-Fos for polyubiquitylation and regulates c-Fos protein levels. Unlike the phosphorylation of other SCF (SKP1-CUL1-F-box)/CRL1 substrates that promotes substrates binding to F-box, epidermal growth factor (EGF)-induced c-Fos S374 phosphorylation dissociates c-Fos from KDM2B and stabilizes c-Fos protein. Non-phosphorylatable and phosphomimetic mutations at S374 result in c-Fos protein which cannot be induced by EGF or accumulates constitutively and lead to decreased or increased cell proliferation, respectively. Multiple tumor-derived KDM2B mutations impaired the function of KDM2B to target c-Fos degradation and to suppress cell proliferation. These results reveal a novel function of KDM2B in the negative regulation of cell proliferation by assembling an E3 ligase to targeting c-Fos protein degradation that is antagonized by mitogenic stimulations

Superconducting Order Parameter in Bi-Layer Cuprates: Occurrence of π\pi Phase Shifts in Corner Junctions

We study the order parameter symmetry in bi-layer cuprates such as YBaCuO, where interesting $\pi$ phase shifts have been observed in Josephson junctions. Taking models which represent the measured spin fluctuation spectra of this cuprate, as well as more general models of Coulomb correlation effects, we classify the allowed symmetries and determine their associated physical properties. $\pi$ phase shifts are shown to be a general consequence of repulsive interactions, independent of whether a magnetic mechanism is operative. While it is known to occur in d-states, this behavior can also be associated with (orthorhombic) s-symmetry when the two sub-band gaps have opposite phase. Implications for the magnitude of $T_c$ are discussed.Comment: 5 pages, RevTeX 3.0, 9 figures (available upon request

Comparison of spin dynamics in YBa2Cu3O7-δ and La2-xSrxCuO4: Effects of Fermi-surface geometry

Neutron experiments have indicated that the structure factor S(q,ω) for the two cuprates YBa2Cu3O7-δ and La2-xSrxCuO4 has a different q dependence. Commensurate peaks at (π/a,π/a) are observed in the former case, whereas clearly incommensurate peaks are seen in the latter, for metallic hole concentrations. We attribute this contrasting q dependence to differences in the Fermi-surface geometry, obtained in band-structure approaches, and (for the YBaCuO system) also corroborated by photoemission experiments. Using a large Coulomb-U, Fermi-liquid-based scheme, we present results for the q,ω and temperature dependence of the neutron cross section as well as for the temperature dependence of the NMR relaxation, in both cuprate families at various hole concentrations. When antiferromagnetic quasiparticle interactions of moderate strength are included, these calculations compare favorably with experiment. It should be stressed that the Fermi-surface shape must be accurately represented in both systems in order to produce this good agreement with the neutron data. We conclude that the close correspondence found, thus far, between band-structure-derived spin dynamics and the detailed fermiology of both cuprates provides support for Fermi-liquid-based schemes. Furthermore, this correspondence suggests important constraints which should be included in theoretical schemes ranging from the marginal and nearly antiferromagnetic Fermi liquid to more exotic scenarios for the normal state. Within this context, it is extremely important to determine the characteristic energy scales of the Fermi liquid. Comparison of our calculations with the measured energy scales of the spin dynamics indicates that these are sufficiently low so that one can reconcile deviations from canonical behavior above Tc with a Fermi-liquid ground state. Explicit effects of these low-energy scales are discussed in the context of the quasiparticle lifetime as a function of frequency and temperature. Our detailed studies also yield predictions for future experiments which will help to test futher the validity of this approach

The Interaction between the First Transmembrane Domain and the Thumb of ASIC1a Is Critical for Its N-Glycosylation and Trafficking

Acid-sensing ion channel-1a (ASIC1a), the primary proton receptor in the brain, contributes to multiple diseases including stroke, epilepsy and multiple sclerosis. Thus, a better understanding of its biogenesis will provide important insights into the regulation of ASIC1a in diseases. Interestingly, ASIC1a contains a large, yet well organized ectodomain, which suggests the hypothesis that correct formation of domain-domain interactions at the extracellular side is a key regulatory step for ASIC1a maturation and trafficking. We tested this hypothesis here by focusing on the interaction between the first transmembrane domain (TM1) and the thumb of ASIC1a, an interaction known to be critical in channel gating. We mutated Tyr71 and Trp287, two key residues involved in the TM1-thumb interaction in mouse ASIC1a, and found that both Y71G and W287G decreased synaptic targeting and surface expression of ASIC1a. These defects were likely due to altered folding; both mutants showed increased resistance to tryptic cleavage, suggesting a change in conformation. Moreover, both mutants lacked the maturation of N-linked glycans through mid to late Golgi. These data suggest that disrupting the interaction between TM1 and thumb alters ASIC1a folding, impedes its glycosylation and reduces its trafficking. Moreover, reducing the culture temperature, an approach commonly used to facilitate protein folding, increased ASIC1a glycosylation, surface expression, current density and slowed the rate of desensitization. These results suggest that correct folding of extracellular ectodomain plays a critical role in ASIC1a biogenesis and function

Neutron scattering and superconducting order parameter in YBa2Cu3O7

We discuss the origin of the neutron scattering peak at 41 meV observed in YBa$_2$Cu$_3$O$_7$ below $T_c$. The peak may occur due to spin-flip electron excitations across the superconducting gap which are enhanced by the antiferromagnetic interaction between Cu spins. In this picture, the experiment is most naturally explained if the superconducting order parameter has $s$-wave symmetry and opposite signs in the bonding and antibonding electron bands formed within a Cu$_2$O$_4$ bilayer.Comment: In this version, only few minor corrections and the update of references were done in order to make perfect correspondence with the published version. RevTeX, psfig, 5 pages, and 3 figure

Theory of Neutron Scattering in the Normal and Superconducting State of YBCO

We analyze neutron experiments on \ybco at various stoichiometries in the superconducting state, within the context of a bi-layer theory which yields good agreement with the normal state Cu-NMR and neutron data as a function of \omega, q and T. A d-wave superconducting state exhibits peaks at q = ( \pi , \pi , \pi ) and sharp maxima as a function of \omega, at twice the gap frequency. This behavior may have been observed experimentally. The counterpart behavior for other choices of order parameter symmetry is discussed.Comment: uuencoded postscript file for the entire paper enclose