Stiff‐stilbene, a sterically restricted fused ring analogue of stilbene, has been regularly used as a model compound in theoretical studies of stilbene photoisomerization. Lately, owing to its ...excellent photoswitching properties, it is increasingly being applied to reversibly control the properties and function of chemical as well as biological systems. Stiff‐stilbene photoswitches possess a number of advantageous properties including a high quantum yield for photoisomerization and a high thermal stability. Furthermore, they undergo a large geometrical change upon isomerization and their synthesis is straightforward. Herein, we provide an overview of the basic properties of stiff‐stilbene and of recent applications in supramolecular chemistry, catalysis, and biological systems.
Stiff‐stilbene is increasingly applied to reversibly control the properties and function of chemical as well as biological systems. In this Minireview an overview is provided of the basic properties of this promising photoswitch, which is followed by a survey of recent applications.
The performance of seven operational high-resolution satellite-based rainfall products - Africa Rainfall Estimate Climatology (ARC 2.0), Climate Hazards Group InfraRed Precipitation with Stations ...(CHIRPS), Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN), African Rainfall Estimation (RFE 2.0), Tropical Applications of Meteorology using SATellite (TAMSAT), African Rainfall Climatology and Time-series (TARCAT), and Tropical Rainfall Measuring Mission (TRMM) daily and monthly estimates - was investigated for Burkina Faso. These were compared to ground data for 2001-2014 on a point-to-pixel basis at daily to annual time steps. Continuous statistics was used to assess their performance in estimating and reproducing rainfall amounts, and categorical statistics to evaluate rain detection capabilities. The north-south gradient of rainfall was captured by all products, which generally detected heavy rainfall events, but showed low correlation for rainfall amounts. At daily scale they performed poorly. As the time step increased, the performance improved. All (except TARCAT) provided excellent scores for Bias and Nash-Sutcliffe Efficiency coefficients, and overestimated rainfall amounts at the annual scale. RFE performed the best, whereas TARCAT was the weakest. Choice of product depends on the specific application: ARC, RFE, and TARCAT for drought monitoring, and PERSIANN, CHIRPS, and TRMM daily for flood monitoring in Burkina Faso.
The linkage of two identical binding motifs by a molecular photoswitch has proven to be a straightforward and versatile strategy to control substrate binding affinity by light. Stimulus control of ...binding properties in artificial receptors is partly inspired by the dynamic behavior of proteins and is highly attractive as it could, for example, improve extraction processes and allow (de)activation of membrane transport on demand. This feature article summarizes the development and design principles of molecular tweezers containing a molecular photoswitch as the core unit. Besides the control of binding affinity by isomerization, the effect of substrate binding on the isomerization behavior is discussed where data is available. While the latter often receives less attention, it could be of benefit in the future creation of multi-stimuli-controlled molecular switching and machine-like systems.
Molecular rotary motors Roke, Diederik; Wezenberg, Sander J.; Feringa, Ben L.
Proceedings of the National Academy of Sciences - PNAS,
09/2018, Letnik:
115, Številka:
38
Journal Article
Recenzirano
Odprti dostop
The field of synthetic molecular machines has quickly evolved in recent years, growing from a fundamental curiosity to a highly active field of chemistry. Many different applications are being ...explored in areas such as catalysis, self-assembled and nanostructured materials, and molecular electronics. Rotary molecular motors hold great promise for achieving dynamic control of molecular functions as well as for powering nanoscale devices. However, for these motors to reach their full potential, many challenges still need to be addressed. In this paper we focus on the design principles of rotary motors featuring a double-bond axle and discuss the major challenges that are ahead of us. Although great progress has been made, further design improvements, for example in terms of efficiency, energy input, and environmental adaptability, will be crucial to fully exploit the opportunities that these rotary motors offer.
There is a need for a new, less invasive breast reconstruction option for patients who undergo mastectomy in their breast cancer treatment.
To investigate quality of life (QoL) among patients ...undergoing a new breast reconstruction technique, autologous fat transfer (AFT), compared with that among patients undergoing implant-based reconstruction (IBR).
The BREAST trial was a randomized clinical trial conducted between November 2, 2015, and October 31, 2021, performed in 7 hospitals across the Netherlands. Follow-up was 12 months. Referrals could be obtained from general practitioners and all departments from participating or nonparticipating hospitals. The patients with breast cancer who had undergone mastectomy and were seeking breast reconstruction were screened for eligibility (radiotherapy history and physique) by participating plastic surgeons. Patients receiving postmastectomy radiotherapy were excluded.
Breast reconstruction with AFT plus expansion or 2-phased IBR. Randomization was done in a 1:1 ratio.
The statistical analysis was performed per protocol. The predefined primary outcome was QoL at 12 months after final surgery. This was measured by the BREAST-Q questionnaire, a validated breast reconstruction surgery questionnaire. Questions on the BREAST-Q questionnaire are scored from 0 to 100, with a higher score indicating greater satisfaction or better QoL (depending on the scale). Secondary outcomes were breast volume and the safety and efficacy of the techniques.
A total of 193 female patients (mean SD age, 49.2 10.6 years) 18 years or older who desired breast reconstruction were included, of whom 91 patients in the AFT group (mean SD age, 49.3 10.3 years) and 80 in the IBR group (mean age, 49.1 11.0 years) received the allocated intervention. In total, 64 women in the AFT group and 68 women in the IBR group completed follow-up. In the IBR group, 18 patients dropped out mainly due to their aversion to implant use while in the AFT group 6 patients ended their treatment prematurely because of the burden (that is, the treatment being too heavy or tiring). The BREAST-Q scores were higher in the AFT group in all 5 domains and significantly higher in 3: satisfaction with breasts (difference, 9.9; P = .002), physical well-being: chest (difference; 7.6; P = .007), and satisfaction with outcome (difference, 7.6; P = .04). Linear mixed-effects regression analysis showed that QoL change over time was dependent on the treatment group in favor of AFT. The mean (SD) breast volume achieved differed between the groups (AFT: 300.3 111.4 mL; IBR: 384.1 86.6 mL). No differences in oncological serious adverse events were found.
This randomized clinical trial found higher QoL and an increase in QoL scores over time in the AFT group compared with the IBR group. No evidence was found that AFT was unsafe. This is encouraging news since it provides a third, less invasive reconstruction option for patients with breast cancer.
ClinicalTrials.gov Identifier: NCT02339779.
Oceanic Anoxic Event 2 (Cenomanian–Turonian: ca 94 Ma) represents a major palaeoceanographic phenomenon that took place during an interval of extreme global warmth when large amounts of organic ...matter entered the marine burial record, probably triggered by increased availability of nutrients for planktonic biota. Three sections (Eastbourne, Sussex, UK; Raia del Pedale, Campania, Italy; and Tarfaya, Morocco) recording this event illustrate the influence on marine geochemistry of mafic volcanic rock‐seawater interaction, anoxia to euxinia, and re‐oxygenation and cooling during the so‐called ‘Plenus Cold Event’. The Eastbourne section represents the organic‐lean epicontinental pelagic deposits of the English Chalk; the Raia del Pedale section represents a shallow‐water platform carbonate on the Tethyan continental margin, also largely devoid of organic matter; and the Tarfaya core represents an Atlantic margin site where cyclically bedded organic‐rich sediments were well developed. Correlation between all three sections is readily achieved by biostratigraphy and carbon‐isotope stratigraphy (δ13Ccarb and δ13Corg) over the Oceanic Anoxic Event 2 interval, represented by a characteristic broad positive carbon‐isotope excursion. The stratigraphic range of the Plenus Cold Event, defined by the presence, in two discrete levels, of boreal fauna and an excursion to heavier oxygen‐isotope values in the English Chalk, can be identified in Raia del Pedale and Tarfaya by using the carbon‐isotope curve as a correlative tool. Similarly, a section in southern France allows its co‐existing osmium‐isotope excursion to relatively unradiogenic values to be placed in the context of the Oceanic Anoxic Event in all three analysed sections. A fall to lower osmium‐isotope values clearly pre‐dated the onset of Oceanic Anoxic Event 2, as defined by the initial rise in carbon‐isotope values, allowing the putative magmatic/mafic event as a trigger for the Oceanic Anoxic Event. An initial drop in sulphur‐isotope ratios (δ34SCAS) at Eastbourne correlates with the osmium‐isotope curve, suggesting that isotopically light sulphur could have been derived from a mafic igneous source. Re‐oxygenation of sediments of all three investigated sections during the Plenus Cold Event is variably illustrated by change in cerium:calcium, iodine:calcium, molybedenum:calcium and uranium:calcium ratios, according to the redox behaviour of the elements in question and whether controls on seawater chemistry were local or global in nature. Changes in molybdenum‐isotope ratios from Tarfaya and portions of the sulphur‐isotope curve from Eastbourne and Raia del Pedale also indicate the probable presence of more oxygen‐rich bottom waters during the Plenus Cold Event. Oxidation by such waters of previously deposited organic‐rich shales, as well as loss of anoxic/euxinic sinks, is credited with temporarily enriching global seawater in a range of other redox‐sensitive trace metals (for example, V, Cr, Co, Ni, Cu, Zn and Cd) during ongoing basalt‐seawater interaction indicated by persistent relatively non‐radiogenic osmium‐isotope seawater values. However, early diagenetic enrichment of manganese in the English Chalk over much of the Oceanic Anoxic Event interval is broadly correlative in time with relatively low osmium‐isotope values in sections elsewhere: a relationship that may be due to the lack of affinity of manganese with carbon‐rich shales, hence allowing relatively elevated concentrations of the element in marine waters to persist during leaching of mafic rocks, unlike other redox‐sensitive species. The calcium‐isotope and lithium‐isotope ratios from Eastbourne and Raia del Pedale indicate an increase in global weathering during the initial phase of Oceanic Anoxic Event 2, and the shift in strontium isotopes and osmium isotopes to more unradiogenic values during the event suggests that not only construction but also destruction of one or more Large Igneous Provinces was probably a proximal cause of this major palaeoceanographic phenomenon by elevating nutrient levels and planktonic productivity in large tracts of the world ocean. Globally widespread carbon burial and silicate weathering are both identified as important mechanisms for drawing down atmospheric carbon dioxide that, in the absence of overwhelming volcanogenic replenishment of this greenhouse gas during the early phase of Oceanic Anoxic Event 2, caused the Plenus Cold Event.
This study is the first of its kind to quantify possible effects of climate change on rice production in Africa. We simulated impacts on rice in irrigated systems (dry season and wet season) and ...rainfed systems (upland and lowland). We simulated the use of rice varieties with a higher temperature sum as adaptation option. We simulated rice yields for 4 RCP climate change scenarios and identified causes of yield declines. Without adaptation, shortening of the growing period due to higher temperatures had a negative impact on yields (−24% in RCP 8.5 in 2070 compared with the baseline year 2000). With varieties that have a high temperature sum, the length of the growing period would remain the same as under the baseline conditions. With this adaptation option rainfed rice yields would increase slightly (+8%) but they remain subject to water availability constraints. Irrigated rice yields in East Africa would increase (+25%) due to more favourable temperatures and due to CO2 fertilization. Wet season irrigated rice yields in West Africa were projected to change by −21% or +7% (without/with adaptation). Without adaptation irrigated rice yields in West Africa in the dry season would decrease by −45% with adaptation they would decrease significantly less (−15%). The main cause of this decline was reduced photosynthesis at extremely high temperatures. Simulated heat sterility hardly increased and was not found a major cause for yield decline. The implications for these findings are as follows. For East Africa to benefit from climate change, improved water and nutrient management will be needed to benefit fully from the more favourable temperatures and increased CO2 concentrations. For West Africa, more research is needed on photosynthesis processes at extreme temperatures and on adaptation options such as shifting sowing dates.
In the Sahel zone in West Africa, temperature rise will lead to large rice yield declines. However, more investigation to understand the response of rice plants to extreme temperatures and adaptation options is needed. In East Africa temperature rise leads to new opportunities for rice the colder highlands
In recent decades, there have been substantial increases in crop production in sub-Saharan Africa (SSA) as a result of higher yields, increased cropping intensity, expansion of irrigated cropping ...systems, and rainfed cropland expansion. Yet, to date much of the research focus of the impact of climate change on crop production in the coming decades has been on crop yield responses. In this study, we analyse the impact of climate change on the potential for increasing rainfed cropping intensity through sequential cropping and irrigation expansion in central Benin. Our approach combines hydrological modelling and scenario analysis involving two Representative Concentration Pathways (RCPs), two water-use scenarios for the watershed based on the Shared Socioeconomic Pathways (SSPs), and environmental water requirements leading to sustained streamflow. Our analyses show that in Benin, warmer temperatures will severely limit crop production increases achieved through the expansion of sequential cropping. Depending on the climate change scenario, between 50% and 95% of cultivated areas that can currently support sequential cropping or will need to revert to single cropping. The results also show that the irrigation potential of the watershed will be at least halved by mid-century in all scenario combinations. Given the urgent need to increase crop production to meet the demands of a growing population in SSA, our study outlines challenges and the need for planned development that need to be overcome to improve food security in the coming decades.
Elucidating the role of molecular stochasticity in cellular growth is central to understanding phenotypic heterogeneity and the stability of cellular proliferation. The inherent stochasticity of ...metabolic reaction events should have negligible effect, because of averaging over the many reaction events contributing to growth. Indeed, metabolism and growth are often considered to be constant for fixed conditions. Stochastic fluctuations in the expression level of metabolic enzymes could produce variations in the reactions they catalyse. However, whether such molecular fluctuations can affect growth is unclear, given the various stabilizing regulatory mechanisms, the slow adjustment of key cellular components such as ribosomes, and the secretion and buffering of excess metabolites. Here we use time-lapse microscopy to measure fluctuations in the instantaneous growth rate of single cells of Escherichia coli, and quantify time-resolved cross-correlations with the expression of lac genes and enzymes in central metabolism. We show that expression fluctuations of catabolically active enzymes can propagate and cause growth fluctuations, with transmission depending on the limitation of the enzyme to growth. Conversely, growth fluctuations propagate back to perturb expression. Accordingly, enzymes were found to transmit noise to other unrelated genes via growth. Homeostasis is promoted by a noise-cancelling mechanism that exploits fluctuations in the dilution of proteins by cell-volume expansion. The results indicate that molecular noise is propagated not only by regulatory proteins but also by metabolic reactions. They also suggest that cellular metabolism is inherently stochastic, and a generic source of phenotypic heterogeneity.
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