Seasonal variations of soil microbial biomass carbon (C) and nitrogen (N), soil microbial activity and microbial metabolic quotient (<i>q</i>CO₂) in the 0 - 10 cm soil layer 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 two growing seasons. 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 soil organic carbon (C), total nitrogen (N) and inorganic N content to carbon addition (+60%) and water addition (+30%) during the two growing seasons 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

Results (<i>F</i>-values) of Three-way ANOVAs on the effects of carbon addition (C), water addition (W), year (Y), and their interactions on soil organic C (SOC), soil total N (TN), aboveground biomass C (ABC) and N (ABN), root biomass C (RBC) and N (RBN), grass biomass (GB), forb biomass (FB) and the ratio of grass to forb biomass (GB: FB).

*<p> <i>represents significant at P<0.05.</i></p

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

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

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

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

Single-Nucleobase-Resolved Nanoruler Determines the Surface Energy Transfer Radius on the Living Cell Membrane

Investigations about surface energy transfer radius (r0) are limited to the aqueous solution system, and it is quite limited on experimental values of r0 between dyes and the corresponding gold particle (AuNP) sizes, especially for living cell systems. Hence, the selection of suitable AuNP-dye pairs is restricted when designing nanometal surface energy transfer (NSET) strategies in analytical sciences. Here, we developed a single-nucleobase-resolved NSET strategy to in situ measure the r0 value between a specific dye and different-sized AuNPs on the living cell membrane. Using the aptamer-dye complex (XQ-2d-nTA-FAM) and antiCD71 antibody-coupled AuNP conjugate (Au@antiCD71) as two working elements to bind two different sites on CD71 receptors on living cell membranes, we modified the nTA spacer between FAM and the terminal of aptamer to change the distance (r) from FAM to AuNP center and further adjusted the quenching efficiency (Φ) between them. Different r0 values of various AuNP-FAM pairs in living cells are determined by this in situ detection strategy. Based on this single-nucleobase-resolved NSET strategy, we established a simple and efficient universal method for measuring r0 in the living cell system, which greatly expanded the selection range of AuNP-dye pairs during the construction of the NSET model at the nanoscale