Figure 1

<p>Daily precipitation (bars) and daily mean air temperature (line) in 2010 and 2011 (A). Data are from the eddy tower adjacent (approximately 100 m) to the experimental site. Seasonal variations of soil temperature (B) and water content (C) at topsoil layer (0–10 cm) in response to carbon addition (+60%) and water addition (+30%) in the temperate steppe of northeastern China. Insets represent the two seasonal mean values of soil temperature (ST) and water content (SWC). Vertical bars indicate standard errors of means (n = 6). Difference lowercase letters indicate statistically significant differences (<i>P</i><0.05). A = ambient condition (control), C = carbon addition, W = water addition, CW = combined carbon and water additions.</p

Responses of aboveground biomass carbon (C) and nitrogen (N), root biomass C and N, peak aboveground biomass of grass and forb and the grass: forb ratio to carbon addition (+60%) and water addition (+30%) in 2010 and 2011 in temperate steppe of northeastern China.

<p>Vertical bars indicate standard errors of means (n = 6). Difference lowercase letters indicate statistically significant differences (<i>P</i><0.05). A = ambient condition (control), C = carbon addition, W = water addition, CW = combined carbon and water additions.</p

The total biomass phospholipid fatty acids (PLFAs), percentages of fungal and bacterial PLFAs to the total biomass PLFAs, and the ratio of fungal to bacterial PLFAs as influenced by carbon addition (+60%) and water addition (+30%) in temperate steppe of northeastern China.

<p>Values show the monthly means from June to September in the growing season. Vertical bars indicate standard errors of means (n = 6). Difference lowercase letters indicate statistically significant differences (<i>P</i><0.05). A = ambient condition (control), C = carbon addition, W = water addition, CW = combined carbon and water additions.</p

Influence of Water on Protein Transitions: Morphology and Secondary Structure

Fibrous protein secondary structural transitions are affected by bound water. A family of specially designed recombinant spider silk-like block copolymers with a gradient of block length, hydrophobilicity, and degree of crystallinity was biosynthesized and characterized to demonstrate the effect of water on the protein structural transitions. These proteins were inspired by the genetic sequences found in the dragline silk of <i>Nephila clavipes</i>, comprising an alanine-rich hydrophobic block, A, a glycine-rich hydrophilic block, B, and a C-terminus or a His-tag, H. Because the A-block is hydrophobic and the B-block is hydrophilic, the spider silk-like block copolymers behave as amphiphilic molecules and self-assemble into various structures in water solution. We employ time-resolved Fourier transform infrared (FTIR) spectroscopy to assign the origin of specific secondary structural transitions during heating. A transition from random coils to β-turns dominates during a lower temperature glass transition (of plasticized protein) mediated by the removal of bound water. Once the protein is in the dry solid state, further heating causes the now-dry protein to undergo the glass transition to the liquid state through conversion of α-helices into β-turns. The structural transitions during protein glass transitions are intrinsic to the amorphous region of protein and are hardly affected by protein hydrophobicity, block length, or crystallinity. The self-assembly morphology of the spider silk-like block copolymers, investigated by scanning electron microscopy, indicates that the large-scale morphology is stable during heating through both the lower and upper temperature glass transitions

Results (<i>F</i>-values) of Four-way ANOVAs on the effects of carbon addition (C), water addition (W), sampling date (D), year (Y), and their interactions on soil temperature (ST), soil water content (SWC), microbial biomass C (MBC), microbial biomass N (MBN), microbial activity (SMA), metabolic quotient (<i>q</i>CO₂), soil inorganic N (IN), soil total PLFAs (TP), contribution of soil fungal PLFAs (F) and bacterial PLFAs (B), and the ratio of fungal to bacterial PLFAs (F: B).

*<p>, **, <i>and</i> ***<i>represent significant at P<0.05, 0.01, and 0.001, respectively.</i></p

Modeling and Experiment Reveal Structure and Nanomechanics across the Inverse Temperature Transition in <i>B. mori</i> Silk-Elastin-like Protein Polymers

Silk and elastin are exemplary protein materials that exhibit exceptional material properties. Silk is uniquely strong, surpassing engineering materials such as Kevlar and steel, while elastin has exquisite flexibility and can reversibly fold into a more structured form at high temperatures when many other proteins would unfold and denature. This phenomenon in elastin is termed the inverse temperature transition. It is a reversible, controllable process that motivates applications in drug delivery, shape change materials, and biomimetic devices. Silk-elastinlike protein polymers (SELPs), which combine repeating <i>B. mori</i> silk and elastin blocks, have been introduced as biologically inspired materials that combine the distinctive properties of the component parts to achieve strong and extensible, tunable biomaterials. Here, we considered a single SELP sequence to examine temperature transition effects at the molecular scale. SELP molecular models were created using Replica Exchange Molecular Dynamics, an accelerated sampling method, and confirmed in experiment by comparing secondary structure distributions. A molecular collapse of the SELP molecule was observed with increased temperature in both molecular simulation and experiment. Temperature-specific differences were observed in the mechanical properties and the unfolding pathways of the polypeptide. Using the Bell–Evans model, we analyzed the free energy landscape associated with molecular unfolding at temperatures below and above the transition temperature range (<i>T</i>_t) of the polypeptide. We found that at physiological pulling rates, the energy barrier to unfold SELPs was counterintuitively higher above <i>T</i>_t. Our findings offer a foundational perspective on the molecular scale mechanisms of temperature-induced phase transition in SELPs, and suggest a novel approach to combine simulation and experiment to study materials for multifunctional biomimetic applications

Influence of Water on Protein Transitions: Thermal Analysis

We have developed a methodology using advanced thermal analysis to characterize the role of water in a specially synthesized family of recombinant spider silk-like block copolymers. These proteins were inspired by the genetic sequences found in the dragline silk of <i>Nephila clavipes</i>, comprising an alanine-rich hydrophobic block, A; a glycine-rich hydrophilic block, B; and a C-terminus or a His-tag, H. This family of proteins serves as a model system in which the hydrophobicity is controlled by A and B block lengths, allowing systematic comparison of water effects within the family. Temperature-modulated differential scanning calorimetry and thermogravimetric analyses were employed to capture the glass to rubber transition, <i>T</i>_g, in water-cast protein films. Modeling of the solid and liquid state heat capacity baselines allows us to determine the critical role played by bound water which plasticizes and stabilizes the protein through interchain bonding. In samples containing bound water, two sequential glass transitions, <i>T</i>_g(1) and <i>T</i>_g(2), were observed during heating. The lower temperature glass transition, <i>T</i>_g(1), is related to conformational change induced by bound water removal, the hydrophobicity of the protein sequences, and the crystallinity of the protein. The higher temperature glass transition, <i>T</i>_g(2), is characteristic of the dry protein. The binding energy of water to protein compares favorably to ligand–water binding affinities. The energy absorbed by evaporating water depends upon the volume fraction of the hydrophilic B-block

Proline, soluble sugar, [K⁺], [Na⁺] and K⁺/ Na⁺in <i>Leymus chinensis</i> at large scale longitudinal gradient in northeast China.

<p>Values are means (± SE) of 30–35 replications. Values with the same letters indicate no significant difference between sites (site/site) within each physiological property (P>0.05).</p

Anatomical variations in <i>Leymus chinensis</i> at large scale longitudinal gradient in northeast China.

<p>Values are means (± SE) of 25–30 replications. Values with the same letters indicate no significant difference between sites (site/site) within each anatomical property (P > 0.05).</p

Variations of leaf thickness (a) and leaf mass per unit area (LMA) (b) in <i>Leymus chinensis</i> along large-scale longitudinal gradient and their correlations with annual precipitation (c, d) and elevation (e, f) at the gradient in northeast China.

<p>Bars are means (± SE) of 25–30 replications. Bars with the same lowercase letters indicate no statistically significant differences (P > 0.05).</p