Kinetic Stabilization of Blue-Emissive Anthracenes: Phenylene Bridging Works Best.
Ontology highlight
ABSTRACT:
SUBMITTER: Nathusius M
PROVIDER: S-EPMC9293334 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:The cubic blue phases of liquid crystals are fascinating and technologically promising examples of hierarchically structured soft materials, comprising ordered networks of defect lines (disclinations) within a liquid crystalline matrix. We present large-scale simulations of their domain growth, starting from a blue phase nucleus within a supercooled isotropic or cholesteric background. The nucleated phase is thermodynamically stable; one expects its slow orderly growth, creating a bulk cubic phase. Instead, we find that the strong propensity to form disclinations drives the rapid disorderly growth of a metastable amorphous defect network. During this process, the original nucleus is destroyed; reemergence of the stable phase may therefore require a second nucleation step. Our findings suggest that blue phases exhibit hierarchical behavior in their ordering dynamics, to match the hierarchy in their structure.
| S-EPMC2922121 | biostudies-literature
Project description:There are many item selection methods proposed for computerized adaptive testing (CAT) applications. However, not all of them have been used in computerized multistage testing (ca-MST). This study uses some item selection methods as a routing method in ca-MST framework. These are maximum Fisher information (MFI), maximum likelihood weighted information (MLWI), maximum posterior weighted information (MPWI), Kullback-Leibler (KL), and posterior Kullback-Leibler (KLP). The main purpose of this study is to examine the performance of these methods when they are used as a routing method in ca-MST applications. These five information methods under four ca-MST panel designs and two test lengths (30 items and 60 items) were tested using the parameters of a real item bank. Results were evaluated with overall findings (mean bias, root mean square error, correlation between true and estimated thetas, and module exposure rates) and conditional findings (conditional absolute bias, standard error of measurement, and root mean square error). It was found that test length affected the outcomes much more than other study conditions. Under 30-item conditions, 1-3 designs outperformed other panel designs. Under 60-item conditions, 1-3-3 designs were better than other panel designs. Each routing method performed well under particular conditions; there was no clear best method in the studied conditions. The recommendations for routing methods in any particular condition were provided for researchers and practitioners as well as the limitations of these results.
| S-EPMC6373851 | biostudies-literature
Project description:Nonvolatile room-temperature luminescent molecular liquids are a new generation of organic soft materials. They possess high stability, versatile optical properties, solvent-free fluid behaviour and can effectively accommodate dopant dye molecules. Here we introduce an approach to optimize anthracene-based liquid materials, focussing on enhanced stability, fluorescence quantum yield, colour tunability and processability, with a view to flexible electronic applications. Enveloping the anthracene core in low-viscosity branched aliphatic chains results in stable, nonvolatile, emissive liquid materials. Up to 96% efficient energy-transfer-assisted tunable emission is achieved by doping a minute amount of acceptor dye in the solvent-free state. Furthermore, we use a thermoresponsive dopant to impart thermally controllable luminescence colours. The introduced strategy leading to diverse luminescence colours at a single blue-light excitation can be an innovative replacement for currently used luminescent materials, providing useful continuous emissive layers in developing foldable devices.
| S-EPMC3709479 | biostudies-literature
Project description:Reversibly switchable fluorescent proteins (RSFPs) enable advanced fluorescence imaging, though the performance of this imaging crucially depends on the properties of the labels. We report on the use of an existing small binding peptide, named Enhancer, to modulate the spectroscopic properties of the recently developed rsGreen series of RSFPs. Fusion constructs of Enhancer with rsGreen1 and rsGreenF revealed an increased molecular brightness and pH stability, although expression in living E. coli or HeLa cells resulted in a decrease of the overall emission. Surprisingly, Enhancer binding also increased off-switching speed and resistance to switching fatigue. Further investigation suggested that the RSFPs can interconvert between fast- and slow-switching emissive states, with the overall protein population gradually converting to the slow-switching state through irradiation. The Enhancer modulates the spectroscopic properties of both states, but also preferentially stabilizes the fast-switching state, supporting the increased fatigue resistance. This work demonstrates how the photo-physical properties of RSFPs can be influenced by their binding to other small proteins, which opens up new horizons for applications that may require such modulation. Furthermore, we provide new insights into the photoswitching kinetics that should be of general consideration when developing new RSFPs with improved or different photochromic properties.
| S-EPMC5618663 | biostudies-literature
Project description:Micronutrient deficiencies (MNDs) occur as a result of insufficient intake of minerals and vitamins that are critical for body growth, physical/mental development, and activity. These deficiencies are particularly prevalent in lower-and middle-income countries (LMICs), falling disproportionately on the poorest and most vulnerable segments of the society. Dietary diversity is considered the most effective method in reducing this deficiency but is often a major constraint as most foods rich in micronutrients are also expensive and thereby inaccessible to poorer members of society. In recent years, affordable commodities such as staple foods (e.g., cereals, roots, and tubers) and condiments (e.g., salt and oil) have been targeted as "vehicles" for fortification and biofortification. Despite efforts by many countries to support such initiatives, there have been mixed experiences with delivery and coverage. An important but little understood driver of success and failure for food fortification has been the range of business models and approaches adopted to promote uptake. This review examines the different models used in the delivery of fortified food including complementary foods and biofortified crops. Using a keyword search and pearl growing techniques, the review located 11,897 texts of which 106 were considered relevant. Evidence was found of a range of business forms and models that attempt to optimise uptake, use, and impact of food fortification which are specific to the 'food vehicle' and environment. We characterise the current business models and business parameters that drive successful food fortification and we propose an initial structure for understanding different fortification business cases that will offer assistance to future designers and implementors of food fortification programmes.
| S-EPMC6683040 | biostudies-literature
Project description:Visible emission colloidal quantum dots (QDs) have shown promise in optical and optoelectronic applications. These QDs are typically composed of relatively expensive elements in the form of indium, cadmium, and gallium since alternative candidate materials exhibiting similar properties are yet to be realized. Herein, for the first time, we report red green blue (RGB) photoluminescences with quantum yields of 18% from earth-abundant lead sulfide (PbS) QDs. The visible emissive property is mainly attributed to a high degree of crystallinity even for the extremely small QD sizes (1-3 nm), which is realized by employing a heterogeneous reaction methodology at high growth temperatures (>170 °C). We demonstrate that the proposed heterogeneous synthetic method can be extended to the synthesis of other metal chalcogenide QDs, such as zinc sulfide and zinc selenide, which are promising for future industrial applications. More importantly, benefiting from the enlarged band gaps, the as-prepared PbS solar cells show an impressive open circuit voltage (∼0.8 V) beyond that reported to date.
| S-EPMC6003545 | biostudies-literature
Project description:Theoretical calculations suggest that small daily reductions in energy intake can cumulatively lead to substantial weight loss, but experimental data to support these calculations are lacking. We conducted a 1-year randomized controlled pilot study of low (10%) or moderate (30%) energy restriction (ER) with diets differing in glycemic load in 38 overweight adults (mean +/- s.d., age 35 +/- 6 years; BMI 27.6 +/- 1.4 kg/m(2)). Food was provided for 6 months and self-selected for 6 additional months. Measurements included body weight, resting metabolic rate (RMR), adherence to the ER prescription assessed using (2)H(2)(18)O, satiety, and eating behavior variables. The 10%ER group consumed significantly less energy (by (2)H(2)(18)O) than prescribed over 12 months (18.1 +/- 9.8%ER, P = 0.04), while the 30%ER group consumed significantly more (23.1 +/- 8.7%ER, P < 0.001). Changes in body weight, satiety, and other variables were not significantly different between groups. However, during self-selected eating (6-12 months) variability in % weight change was significantly greater in the 10%ER group (P < 0.001) and poorer weight outcome on 10%ER was predicted by higher baseline BMI and greater disinhibition (P < 0.0001; adj R(2) = 0.71). Weight loss at 12 months was not significantly different between groups prescribed 10 or 30%ER, supporting the efficacy of low ER recommendations. However, long-term weight change was more variable on 10%ER and weight change in this group was predicted by body size and eating behavior. These preliminary results indicate beneficial effects of low-level ER for some but not all individuals in a weight control program, and suggest testable approaches for optimizing dieting success based on individualizing prescribed level of ER.
| S-EPMC2869203 | biostudies-literature
Project description:p53 is a homotetrameric tumor suppressor protein that is found to be mutated in most human cancers. Some of these mutations, particularly mutations to R337, fall in the tetramerization domain and cause defects in tetramer formation leading to loss of function. Mutation to His at this site has been found to destabilize the tetramer in a pH-dependent fashion. In structures of the tetramerization domain determined by crystallography, R337 from one monomer makes a salt bridge with D352 from another monomer, apparently helping to stabilize the tetramer. Here we present molecular dynamics simulations of wild-type p53 and the R337His mutant at several different pH and salt conditions. We find that the 337-352 salt bridge is joined by two other charged side chains, R333 and E349. These four residues do not settle into a fixed pattern of salt bridging, but continue to exchange salt-bridging partners on the nanosecond time scale throughout the simulation. This unusual system of fluid salt bridging may explain the previous finding from alanine scanning experiments that R333 contributes significantly to protein stability, even though in the crystal structure it is extended outward into solvent. This extended conformation of R333 appears to be the result of a specific crystal contact and, this contact being absent in the simulation, R333 turns inward to join its interaction partners. When R337 is mutated to His but remains positively charged, it maintains the original interaction with D352, but the newly observed interaction with E349 is weakened, accounting for the reduced stability of R337H even under mildly acidic conditions. When this His is deprotonated, the interaction with D352 is also lost, accounting for the further destabilization observed under mildly alkaline conditions. Simulations were carried out using both explicit and implicit solvent models, and both displayed similar behavior of the fluid salt-bridging cluster, suggesting that implicit solvent models can capture at least the qualitative features of this phenomenon as well as explicit solvent. Simulations under strongly acidic conditions in implicit solvent displayed the beginnings of the unfolding process, a destabilization of the hydrophobic dimer-dimer interface. Computational alanine scanning using the molecular mechanics Poisson-Boltzmann surface area method showed significant correlation to experimental unfolding data for charged and polar residues, but much weaker correlation for hydrophobic residues.
| S-EPMC2104543 | biostudies-literature
Project description:The impact of disulfide bonds on protein stability goes beyond simple equilibrium thermodynamics effects associated with the conformational entropy of the unfolded state. Indeed, disulfide crosslinks may play a role in the prevention of dysfunctional association and strongly affect the rates of irreversible enzyme inactivation, highly relevant in biotechnological applications. While these kinetic-stability effects remain poorly understood, by analogy with proposed mechanisms for processes of protein aggregation and fibrillogenesis, we propose that they may be determined by the properties of sparsely-populated, partially-unfolded intermediates. Here we report the successful design, on the basis of high temperature molecular-dynamics simulations, of six thermodynamically and kinetically stabilized variants of phytase from Citrobacter braakii (a biotechnologically important enzyme) with one, two or three engineered disulfides. Activity measurements and 3D crystal structure determination demonstrate that the engineered crosslinks do not cause dramatic alterations in the native structure. The inactivation kinetics for all the variants displays a strongly non-Arrhenius temperature dependence, with the time-scale for the irreversible denaturation process reaching a minimum at a given temperature within the range of the denaturation transition. We show this striking feature to be a signature of a key role played by a partially unfolded, intermediate state/ensemble. Energetic and mutational analyses confirm that the intermediate is highly unfolded (akin to a proposed critical intermediate in the misfolding of the prion protein), a result that explains the observed kinetic stabilization. Our results provide a rationale for the kinetic-stability consequences of disulfide-crosslink engineering and an experimental methodology to arrive at energetic/structural descriptions of the sparsely populated and elusive intermediates that play key roles in irreversible protein denaturation.
| S-EPMC3728334 | biostudies-literature
Project description:Nanopore sequencing ground study, extreme environment study and International Space Station (ISS) study
| PRJEB41406 | ENA