11 Search Results

Target of rapamycin (TOR) and sucrose non-fermenting 1–related protein kinase 1 (SnRK1) are conserved regulators of plant growth and metabolism and are often portrayed as functionally antagonistic under nutrient limitation. However, how this relationship operates across different nutrient contexts remains poorly defined. Here, we generated an Arabidopsis dual-reporter line that enables simultaneous monitoring of TOR and SnRK1 activities and profiled their dynamics under carbon and nitrogen perturbations. We found that TOR and SnRK1 activities\r\noverall exhibit a negative relationship during the transition from carbon starvation to carbon abundance; however, their temporal dynamics during that transition do not support a strictly inversemore » correlation. Under dark conditions, TOR activity is gradually repressed, while SnRK1 is initially repressed in the early hours and subsequently activated during extended darkness. During nitrogen starvation, TOR activity is progressively repressed, whereas SnRK1 is activated during early hours and then becomes repressed. In vitro, recombinant SnRK1a1 directly\r\ninhibits the activity of immunoprecipitated TOR (IP-TOR), whereas IP-TOR does not directly affect SnRK1a1 activity. Together, these results support a nutrient dependent model in which TOR and SnRK1 are coordinated primarily by cellular metabolic status.\r\n« less

Thermally triggered depolymerization has traditionally been viewed through the lens of sustainability and recycling, not as a constructive tool for materials design. Herein, we show that selective, thermally triggered depolymerization to gaseous monomer serves as a solvent-free strategy for generating porosity in nanostructured polymer materials, offering a means to bypass the mass transport limitations inherent in conventional solution-based etching. As a demonstration platform, we employed polymerization-induced microphase separation (PIMS) to generate disordered bicontinuous block copolymer structures with embedded depolymerizable domains. By incorporating a methacrylate block susceptible to thermal depolymerization within a cross-linked, depolymerization-resistant styrenic matrix, we developed a process wemore » term depolymerization etching of polymerization-induced microphase separations (DEPIMS). This approach enables highly selective and efficient domain removal via reversion to monomer to produce mesoporous materials with high surface areas (>200 m²/g). Subsequent surface functionalization yielded mesoporous adsorbents with tunable uptake kinetics and among the highest dye adsorption capacities reported for PIMS-derived materials, demonstrating the adaptability of the DEPIMS platform for chemical separations. DEPIMS can also be extended to a gram-scale, one-pot approach to yield mesoporous materials with recoverable monomer in under 12 h. These findings reposition thermal depolymerization from a sustainability tool to a broadly enabling strategy for scalable, on-demand fabrication of functional nanostructured materials.« less

Certain microalgal species, such as Scenedesmus obliquus strain HTB1, thrive under high CO₂ concentrations, making them promising for carbon sequestration to mitigate climate change. Isolated from the Baltimore Inner Harbor, HTB1 grows faster with 10 % CO₂ than with ambient air. To investigate its responses to salinity and elevated CO₂, two experiments were conducted. In the first, HTB1 was cultured at seven different salinities (0, 17.5, 20, 22.5, 25, 27.5, and 30 ppt) (parts per thousand) under ambient air. Higher salinity caused cell shrinkage, color changes from green to pale white, reduced pigments like zeaxanthin, lutein, and chlorophyll b, butmore » increased canthaxanthin. Growth declined significantly above 22.5 ppt. The second experiment compared HTB1's response to salinity (0, 10, 20 ppt) under air and 10 % CO₂. Cultures under 10 % CO₂ showed minimal color changes, while those under air shifted from green to brown, with salinity having less inhibitory effects on growth under elevated CO₂. Interestingly, lutein and canthaxanthin levels rose with salinity in 10 % CO₂. These findings indicate that elevated CO₂ mitigates salt stress in HTB1, reducing its impact on growth and promoting adaptive pigment changes. This study sheds light on how salinity and CO₂ interact to influence HTB1's morphology, growth, and pigment composition, enhancing our understanding of its resilience and potential applications.« less

Molecules based on benzimidazolone-dioxazine are known as blue/violet pigments and have been commercialized for decades. However, unfavorable solubility limits the application of these structures as building blocks of conjugated polymers despite their low band gaps. Herein, a series of donor–acceptor conjugated polymers containing soluble benzimidazolone-dioxazine structures as the acceptors and oligothiophene as donors are synthesized and investigated. With increasing numbers of thiophene rings, the steric hindrance diminishes and high molecular weight polymers can be achieved, leading to an improved performance in organic field effect transistor devices. The hole mobility of polymers with three to six thiophene units is in themore » order of 10^-1 cm2 V^-1 s ^-1. Among all the polymers, polymer P3 with three thiophene units between benzimidazolone-dioxazine structures shows the best hole mobility of 0.4 cm2 V^-1 s ^-1. Grazing-incidence wide-angle X-ray scattering results reveal that the high mobility of organic field-effect transistors (OFETs) can be accredited by matched donor–acceptor packing in the solid thin films.« less

Defect engineering through elemental doping is an efficient way to boost the performance of semiconductor photocatalysts. For this work, transition-metal (TM) doped titanate nanowires (TNWs) were prepared via ion-exchange over the titanate precursors and demonstrated for the Rhodamine B (RhB) degradation under ultraviolet (UV) light irradiation. The ion-exchange of selective ions (V⁵⁺, Cr³⁺, Ni²⁺, and Zn²⁺) with protons from pristine TNWs resulted in the hierarchical meso-porosity of nanowires with large pores of ~5–20 nm by TM doping and small pores of ~3.6–4.5 nm inherited from pristine TNWs, which facilitates the mass transfer while maintaining high surface area and active sites.more » Meanwhile, the TM intercalation partially reduces the Ti⁴⁺ to Ti³⁺ and narrows the optical bandgap, which, together with oxygen vacancies and superoxide radicals from pristine TNWs, enhance the adsorption and photocatalytic degradation performance of RhB. This work helps to elucidate the effects of transition-metal doping and provides a rational strategy towards high performance titanate-based photocatalysts for efficient and sustainable wastewater treatment.« less

Here for the first time, we combined Monte-Carlo and nonphotochemical hole burning (NPHB) master equation approaches to allow for ultra-high resolution (<0.005 cm^-1, smaller than the typical homogeneous line widths at 5 K) simulations of the NPHB spectra of dimers and trimers of interacting pigments. These simulations reveal significant differences between the zero-phonon hole (ZPH) action spectrum and the site-distribution function (SDF) of the lowestenergy state. The NPHB of the lowest-energy pigment, following the excitation energy transfer (EET) from the higher-energy pigments which are excited directly, results in the shifts of all excited states. These shifts affect the ZPH actionmore » spectra and EET times derived from the widths of the spectral holes burned in the donor-dominated regions. The effect is present for a broad variety of realistic anti-hole functions and it is maximal at relatively low values of inter-pigment coupling (V ≤ 5 cm^-1) where the use of the Förster approximation is justified. These findings need to be considered in interpreting various optical spectra of photosynthetic pigment-protein complexes for which SDFs (describing the inhomogeneous broadening) are often obtained directly from the ZPH action spectra. Water-soluble chlorophyll-binding protein (WSCP) was considered as an example.« less

Here we provide an analysis of the pigment composition of reconstituted wild type CP29 complexes. The obtained stoichiometry of 9 ± 0.6 Chls a and 3 ± 0.6 Chls b per complex, with some possible heterogeneity in the carotenoid binding, is in agreement with 9 Chls a and 3.5 Chls b revealed by the modeling of low-temperature optical spectra. We find that ~50% of Chl b614 is lost during the reconstitution/purification procedure, while Chls a are almost fully retained. The excitonic structure and the nature of the low-energy (low-E) state(s) are addressed via simulations (using Redfield theory) of 5 Kmore » absorption and fluorescence/nonresonant hole-burned (NRHB) spectra obtained at different excitation/burning conditions. We show that, depending on laser excitation frequency, reconstituted complexes display two (independent) low-E states (i.e., the A and B traps) with different NRHB and emission spectra. The red-shifted state A near 682.4 nm is assigned to a minor (~10%) subpopulation (Sub. II) that most likely originates from an imperfect local folding occurring during protein reconstitution. Its lowest energy state A (localized on Chl a604) is easily burned with λ_B = 488.0 nm and has a red-shifted florescence origin band near 683.7 nm that is not observed in native (isolated) complexes. Prolonged burning by 488.0 nm light reveals a second low-E trap at 680.2 nm (state B) with a fluorescence origin-band ~681 nm which is also observed when using a direct lowfluence excitation near 650 nm. The latter state is mostly delocalized over the a611, a612, a615 Chl trimer, and corresponds to the lowest energy state of the major (~90%) subpopulation (Sub. I) which exhibits a lower hole-burning quantum yield. Thus, we suggest that major Sub. I correspond to the native folding of CP29, whereas the red-shift of the Chl a604 site energy observed in the minor Sub. II occurs only in reconstituted complexes.« less

Vision is the dominant sensory modality in many organisms for foraging, predator avoidance, and social behaviors including mate selection. Vertebrate visual perception is initiated when light strikes rod and cone photoreceptors within the neural retina of the eye. Sensitivity to individual colors, i.e., peak spectral sensitivities (λ_max) of visual pigments, are a function of the type of chromophore and the amino acid sequence of the associated opsin protein in the photoreceptors. Large differences in peak spectral sensitivities can result from minor differences in amino acid sequence of cone opsins. To determine how minor sequence differences could result in large spectralmore » shifts we selected a spectrally-diverse group of 14 teleost Rh2 cone opsins for which sequences and λ_max are experimentally known. Classical molecular dynamics simulations were carried out after embedding chromophore-associated homology structures within explicit bilayers and water. These simulations revealed structural features of visual pigments, particularly within the chromophore, that contributed to diverged spectral sensitivities. Statistical tests performed on all the observed structural parameters associated with the chromophore revealed that a two-term, first-order regression model was sufficient to accurately predict λ_max over a range of 452–528 nm. The approach was accurate, efficient and simple in that site-by-site molecular modifications or complex quantum mechanics models were not required to predict λ_max. These studies identify structural features associated with the chromophore that may explain diverged spectral sensitivities, and provide a platform for future, functionally predictive opsin modeling.« less

Plants and microbes secrete mucilage into soil during dry conditions, which can alter soil structure and increase contact angle. Structured soils exhibit a broad pore size distribution with many small and many large pores, and strong capillary forces in narrow pores can retain moisture in soil aggregates. Meanwhile, contact angle determines the water repellency of soils, which can result in suppressed evaporation rates. Although they are often studied independently, both structure and contact angle influence water movement, distribution, and retention in soils. Here drying experiments were conducted using soil micromodels patterned to emulate different aggregation states of a sandy loammore » soil. Micromodels were treated to exhibit contact angles representative of those in bulk soil (8.4° ± 1.9°) and the rhizosphere (65° ± 9.2°). Drying was simulated using a lattice Boltzmann single-component, multiphase model. In our experiments, micromodels with higher contact angle surfaces took 4 times longer to completely dry versus micromodels with lower contact angle surfaces. Microstructure influenced drying rate as a function of saturation and controlled the spatial distribution of moisture within micromodels. In conclusion, lattice Boltzmann simulations accurately predicted pore-scale moisture retention patterns within micromodels with different structures and contact angles.« less