When does temperature matter for ecosystem respiration?

The temperature response of ecosystem processes is key to understand and predict impacts of climate change. This is especially true for respiration, given its high temperature sensitivity and major role in the global carbon cycle. However, similar intrinsic temperature sensitivity for respiration does not mean comparable temperature effects across ecosystems and biomes because non-temperature factors can be more important. Here we analyzed soil and sediment respiration data and found that in temperature ranges corresponding to high latitude mean temperatures, absolute respiration rates are more sensitive to non-temperature factors than to projected direct temperature effects. However, at higher temperatures (>20 °C) the direct effect of temperature mediated by temperature sensitivity will likely be more important over changes in non-temperature factors in shaping how respiration change over time. This supports past suggestions that the relatively small projected temperature increase at low (tropical) latitudes may have a large direct impact on absolute respiration. In contrast, absolute respiration rates at high (boreal/arctic) latitudes will likely be more sensitive on the development of the non-temperature factors than on the direct effects of the large projected temperature increase there.

Features of the temperature regime effect on the duration of the crops vegetation period in Southern Ukraine

When modeling the prognostic changes in the temperature regime over the territory of Ukraine, the data of the research project for modeling the regional climate and assessing the consequences of its change (CORDEX) were used. The climate projection structure is based on a series of global climatic models (GCM) developed within the framework of CMIP5 project. The influence of the temperature factors on passing the phenological phases and oats yield in the South of Ukraine, implementing the RCP4.5 and RCP8.5 climate scenarios and comparing them with the long-term data is analyzed. As a result of the analysis of the changes in the temperature regime it was revealed that it will be warming the plants vegetation period. The probable change in the oats yield in the southern part of Ukraine under the conditions of climate change using the crop formation model was considered. It is assumed that by 2050 the timing of sowing and germinating the seedlings will be shifted to an earlier date, and the oats yield will increase by 1.26-1.32 times.

Computational Insight into the Rope-Skipping Isomerization of Diarylether Cyclophanes

The restricted rotation of chemical bonds may lead to the formation of stable, conformationally chiral molecules. While the asymmetry in chiral molecules is generally observed in the presence of one or more stereocenters, asymmetry exhibited by conformational chirality in compounds lacking stereocenters, called atropisomerism, depends on structural and temperature factors that are still not fully understood. This atropisomerism is observed in natural diarylether heptanoids where the length of the intramolecular tether constrains the compounds to isolable enantiomers at room temperature. In this work, we examine the impact tether length has on the activation free energies to isomerization of a diarylether cyclophane substructure with a tether ranging from 6 to 14 carbons. Racemization activation energies are observed to decay from 48 kcal/mol for a 7-carbon tether to 9.2 kcal/mol for a 14-carbon tether. Synthetic efforts to experimentally test these constraints are also presented. This work will likely guide the design and synthesis of novel asymmetric cyclophanes that will be of interest in the catalysis community given the importance of atropisomeric ligands in the field of asymmetric catalysis.

Coarse snapshots of oxygen-dissociation intermediates of a giant hemoglobin elucidated by determining the oxygen saturation in individual subunits in the crystalline state

Cooperative oxygen binding of hemoglobin (Hb) has been studied for over half a century as a representative example of the allostericity of proteins. The most important problem remaining to be solved is the lack of structural information on the intermediates between the oxygenated and deoxygenated forms. In order to characterize the intermediate structures, it is necessary to obtain intermediate-state crystals, determine their oxygen saturations and then determine the oxygen saturations of each of their constituent subunits, all of which are challenging issues even now. Here, intermediate forms of the 400 kDa giant Hb from the tubeworm Oligobrachia mashikoi are reported. To overcome the above problems without any artificial modifications to the protein or prosthetic groups, intermediate crystals of the giant Hb were prepared from fully oxygenated crystals by a soaking method. The oxygen saturation of the crystals was measured by in situ observation with a microspectrophotometer using thin plate crystals processed by an ultraviolet laser to avoid saturation of absorption. The oxygen saturation of each subunit was determined by occupancy refinement of the bound oxygen based on ambient temperature factors. The obtained structures reveal the detailed relationship between the structural transition and oxygen dissociation. The dimer subassembly of the giant Hb shows strong correlation with the local structural changes at the heme pockets. Although some local ternary-structural changes occur in the early stages of the structural transition, the associated global ternary-structural and quaternary-structural changes might arise at about 50% oxygen saturation. The models based on coarse snapshots of the allosteric transition support the conventional two-state model of Hbs and provide the missing pieces of the intermediate structures that are required for full understanding of the allosteric nature of Hbs in detail.

A method for intuitively extracting macromolecular dynamics from structural disorder

Macromolecular dynamics manifest as disorder in structure determination, which is subsequently accounted for by displacement parameters (also called temperature factors, or B-factors) or alternate conformations. Though B-factors contain detailed information about structural dynamics, they are the total of multiple sources of disorder, making them difficult to interpret and thus little-used in structural analysis. We report here an analytical approach for decomposing molecular disorder into a parsimonious hierarchical series of contributions, providing an intuitive basis for quantitative structural-dynamics analysis. We demonstrate the decomposition of disorder on example SARS-CoV-2 and STEAP4 structures, from both crystallographic and cryo-electron microscopy data, and reveal how understanding of the macromolecular disorder leads to deeper understanding of molecular motions and flexibility, and suggests hypotheses for molecular mechanisms.

Modeling the underlying environmental factors of milky sea case and luminous bacteria presence in Java Southern Sea in 2019

The milky sea is one of the unique natural phenomena caused by the presence of luminous Vibrio bacteria in marine ecosystems. Recently a milky sea has been reported frequently included in the Java Southern Sea. Simultaneously, numerous remote sensing based approaches have been developed to detect the presence of luminous bacteria and the milky sea. Despite this state of the art, the information of detrimental factors of the marine bioluminescence was still limited. Then this research aims to model the underlying environmental factors causing the milky sea and luminous bacteria presence in the Java Southern Sea in 2019. The remote sensing assessment for the period of July 29-August 6, 2019 shows that the magnitude of bioluminescence measured in radiance was having a maximum value of 255 nanoW/cm2/sr and an average of 107 nanoW/cm2/sr/day (95%CI: 71.9 to 142 nanoW/cm2/sr/day). The milky sea size increased and reached its peak with a size of 44,124 km2 and then declined. The average milky sea size was 37,942 km2 (95% CI: 33,400 to 42,500 km2) and increased with average rate of 16.01% (95%CI: 5.41% to 26.66%). While Akaike Information Criterion (AIC) indicates that the best model to infer the relationship of bacterial bioluminescence with its environmental factors contained Chlorophyll a followed by sea surface temperature factors with AICc values of 101.16 (AICweight: 0.50) and 101.95 (AICweight: 0.34). This indicates that low temperature and high plankton cells is the limiting factors of the bacterial bioluminescence.

Theoretical Study on a Novel Temperature Breakpoint Cyclic Operation to Enhance Desiccant Packed Bed Performance

In a conventional desiccant packed bed dehumidification, the adsorption and desorption operations switched at a constant cycle. However, this Conventional Steady Cyclic (CSC) operation was not performed well under disturbances. Therefore, a Temperature Breakpoint Cyclic (TBC) operation is proposed. A numerical model of the desiccant packed bed dehumidification system has been constructed and validated. The model was then used to assess the desiccant packed bed dehumidification performances in term of moisture removal capacity (MRC) and dehumidification coefficient of performance (DCOP) under various cycle times and temperature factors. The calculation results showed that under CSC, larger amounts of energy were required in the desorption operation, while the TBC exhibited higher performances in term of both MRC and DCOP. Notably, at a high regeneration temperature, the MRC of the TBC was 10% higher than the CSC’s; moreover, the DCOP of the TBC was twice higher than the CSC’s. In other words, at high recovery temperature, both operations exhibited comparable capacities while the energy cost was halved under TBC operation.

Quantifying Radial Growth Response of Pinus Yunnanensis to Climate Change and Drought Event at Different Altitudes and Ages in the Jinsha River Basin

Background The relative influence of climate change and drought events on tree growth at different altitude and tree ages remains insufficiently understood in the Jinsha River Basin, southwest China, limiting prediction of forest adaptability to high-frequency droughts and climate change. We conducted a dendroecological study to explore and quantify the dominant climate factors that determining radial growth of Pinus yunnanensis trees of different ages and at different altitudes, to evaluate their resilience to drought events. Results Radial growth of P. yunnanensis at high elevations is typically limited by low temperatures, the explanatory rate of temperature factors on growth increased from 23.6–59.7% with altitude. Tree growth at low elevations is more sensitive to moisture factors, the explanatory rate of moisture factors on growth decreased from 76.4–40.3% with altitude. The young and mature trees are more prone to moisture factors than middle-age and near-mature trees, the young and near-mature trees are more prone to temperature factors than middle-age and mature trees. The older trees usually showed less drought resistance and recovery than the young and middle-age trees. The resistance and recovery of P. yunnanensis weakened with the increased frequency of drought events. Tree resistance and resilience was highly dependent on the average pre-drought growth, whereas the recovery showed weak or no significant relationships with average pre-drought growth. Conclusion Our study demonstrates that radial growth of P. yunnanensis trees showed age- and altitude-specific demand for energy and moisture. P. yunnanensis trees at different altitudes and ages are differentially adapted to varying levels of climate stress and display different strategies to withstand the effects of drought with altitude and ages.