Hydrogels are adequate systems for investigating biological structural material formation as they mimic a wide range of biomineralization conditions. Previous studies focused on the influence of ...single-component gel systems in the growth of calcite aggregates and their microstructure characteristics. In this work, we investigate the effects of hydrogel mixtures (gelatin/agarose), in the presence and absence of Mg in the growth medium, on calcite aggregate formation, hydrogel incorporation in the calcite, mode of crystallite assembly, and hierarchical mineral organization. We find marked differences between aggregates developed in gel mixtures with increased content of either gelatin or agarose. The presence of Mg, in addition to the gel incorporation, strongly influences the local lattice deformation within the aggregates. The mode of local deformation (homogeneous or localized) is closely related to the size, distribution, and crystallographic co-orientation of subunits within the aggregate. An increase in agarose induces homogeneous distribution of local deformation within the aggregates and formation of a graded mineral arrangement (archetypical spherulites), while an increase in gelatin leads to differentiation of the center and rim portions within the same aggregate. On a higher hierarchical level, when all subunits of an aggregate are considered, both agarose and gelatin evoke the formation of polycrystals.
Poor nutritional status leads to multiple adverse outcomes, but few studies have assessed its role as a risk factor for incident frailty and death in community-dwelling older adults. Hence, the aim ...of this paper is to assess the role of nutritional status using the Global Leadership Initiative on Malnutrition (GLIM) criteria in the risk of frailty and mortality in Spanish community-dwelling older adults.
We used data from two waves (waves 2 (2011–2013) and 3 (2015–2017)) from the Toledo Study of Healthy Ageing, which is an observational, prospective cohort (average follow-up = 3.18 years) of 1660 older (≥65 years) adults living in the community. Nutritional status categories were defined according to the GLIM criteria, which uses a two-step approach. First, screening for malnutrition risk. Once positive, individuals were classified as malnourished according to some phenotypic (body mass index, grip strength and unintentional weight loss) and etiologic (disease burden/inflammation and reduced food intake or assimilation) criteria. Frailty was assessed using both the Frailty Index (FI) and Frailty Trait Scale (FTS). Mortality data was obtained through the National Death Index.
From the 1660 older adults, 248 participants (14.04%) were classified as ‘at malnutrition risk’ (AMR) and 209 (12.59%) as malnourished (MN). AMR and MN subjects were older and with worse functional status (frailer). Adjusted cross-sectional analysis showed an association between nutritional status and frailty by both FI and FTS. Adjusted longitudinal analyses showed that AMR was associated with higher risk of frailty, using both the FTS (OR: 1.262; 95% CI: 1.078–1.815) and the FI (OR: 1.116; 95% CI: 1.098–1.686), while being malnourished was associated with higher mortality risk (OR: 1.748; 95% CI: 1.073–2.849), but not with incident frailty at follow-up period.
Nutritional status, assessed through GLIM, predicts in a dose-dependent manner the risk of frailty and death. Being at malnutrition risk predicts the risk of becoming frail at follow-up period, whereas being malnourished predicts mortality. These findings highlight the importance of assessing the nutritional status of community-dwelling older adults to identify the ones at risk of developing frailty or death and inform targeted nutrition-focused interventions.
Bacterial microcompartments (BMC) are complex macromolecular assemblies that participate in varied chemical processes in about one fourth of bacterial species. BMC-encapsulated enzymatic activities ...are segregated from other cell contents by means of semipermeable shells, justifying why BMC are viewed as prototype nano-reactors for biotechnological applications. Herein, we undertook a comparative study of bending propensities of BMC hexamers (BMC-H), the most abundant shell constituents. Published data show that some BMC-H, like β-carboxysomal CcmK, tend to assemble flat whereas other BMC-H often build curved objects. Inspection of available crystal structures presenting BMC-H in tiled arrangements permitted us to identify two major assembly modes with a striking connection with experimental trends. All-atom molecular dynamics (MD) supported that BMC-H bending is triggered robustly only from the arrangement adopted in crystals by BMC-H that experimentally form curved objects, leading to very similar arrangements to those found in structures of recomposed BMC shells. Simulations on triplets of planar-behaving hexamers, which were previously reconfigured to comply with such organization, confirmed that bending propensity is mostly defined by the precise lateral positioning of hexamers, rather than by BMC-H identity. Finally, an interfacial lysine was pinpointed as the most decisive residue in controlling PduA spontaneous curvature. Globally, results presented herein should contribute to improve our understanding of the variable mechanisms of biogenesis characterized for BMC, and of possible strategies to regulate BMC size and shape.
Arrays of MS2 binding sites are placed into mRNAs and are commonly used to visualize the localization of mRNAs in vivo by the expression of an MS2-GFP fusion protein. In Saccharomyces cerevisiae, we ...observed that arrays of MS2 binding sites inhibit 5' to 3' degradation of the mRNA in yeast cells and lead to the accumulation of a 3' mRNA fragment containing the MS2 binding sites. This accumulation can be dependent on the binding of the MS2 stem loops (MS2-SL) by MS2 coat proteins (MCPs). Since such decay fragments can still bind MCP-GFP, the localization of such mRNA fragments can complicate the interpretation of the localization of full-length mRNA in vivo.
Graphene plasmons provide a suitable alternative to noble-metal plasmons because they exhibit much tighter confinement and relatively long propagation distances, with the advantage of being highly ...tunable via electrostatic gating. Here, we propose to use graphene plasmons as a platform for strongly enhanced light–matter interactions. Specifically, we predict unprecedented high decay rates of quantum emitters in the proximity of a carbon sheet, observable vacuum Rabi splittings, and extinction cross sections exceeding the geometrical area in graphene nanoribbons and nanodisks. Our theoretical results provide the basis for the emerging and potentially far-reaching field of graphene plasmonics, offering an ideal platform for cavity quantum electrodynamics, and supporting the possibility of single-molecule, single-plasmon devices.
We investigate the interplay between quenching and strong coupling in systems that include a collection of quantum emitters interacting with a metal nanoparticle. By using detailed numerical ...simulations and analytical modeling, we demonstrate that quantum emitters can exhibit strong coupling with the particle dipole resonance at distances at which the quenching to nonradiative channels is expected to dominate the dynamics. These results can be accounted for in terms of the pseudomode character of the higher multipole modes of the nanoparticle and the corresponding reduction of the induced loss rate. These findings expand the current understanding of light-matter interaction in plasmonic systems and could contribute to the development of novel quantum plasmonic platforms.
Two highly porous γ-aluminas, a commercial catalyst obtained from the calcination of boehmite and a highly mesoporous product obtained from amorphous aluminum (oxy)hydroxide via a sol–gel-based ...process were investigated by 27Al nuclear magnetic resonance (NMR), transmission electron microscopy (TEM), and atomic pair distribution function (PDF) analysis of synchrotron powder diffraction data. NMR data showed for both materials a distribution of tetrahedrally and octahedrally coordinated Al at a 0.30:0.70 ratio, which is typical for γ-aluminas. TEM studies revealed that rod-shaped particles with about 5nm in thickness are the building blocks of the porous structure in both materials. These particles often extend to a length of 50nm in the commercial catalyst and are considerably shorter in the sol–gel-based material, which has a higher surface area. Refinement of PDFs revealed the presence of a ~1nm scale local structure and the validity of a tetragonal average structure for both materials. This tetragonal average structure contains a substantial fraction of non-spinel octahedral Al atoms. It is argued that the presence of local structure is a general feature of γ-alumina, independent of precursor and synthesis conditions. The concentration of “non-spinel” Al atoms seems to correlate with surface properties, and increases with increasing pore size/surface area. This should have implications to the catalytic properties of porous γ-alumina.
Boehmite-derived and sol–gel synthesized porous γ-Al2O3 possess identical structural properties, featuring a nm scale local structure and a tetragonal average structure. Display omitted
•Porous γ-Al2O3 generally possesses a nm-scale local structure.•The tetragonal average structure contains a substantial fraction of “non-spinel” Al atoms.•The concentration of “non-spinel” Al atoms correlates with surface properties.
A key step in creating efficient and long-lasting catalysts is understanding their deactivation mechanism(s). On this basis, the behavior of a series of Pd/corundum materials during several hydrogen ...adsorption/desorption cycles was studied using temperature-programmed desorption coupled with mass spectrometry and aberration-corrected transmission electron microscopy. The materials, prepared by impregnation and by sputtering, presented uniform well-dispersed Pd nanoparticles. In addition, single atoms and small clusters of Pd were only detected in the materials prepared by impregnation. Upon exposure to hydrogen, the Pd nanoparticles smaller than 2 nm and the single atoms did not present any change, while the larger ones presented a core–shell morphology, where the core was Pd and the shell was PdH x . The results suggest that the long-term activity of the materials prepared by impregnation can be attributed solely to the presence of small clusters and single atoms of Pd.
Molecular mechanisms of shade tolerance in plants Martinez‐Garcia, Jaime F.; Rodriguez‐Concepcion, Manuel
The New phytologist,
August 2023, 2023-08-00, 20230801, Letnik:
239, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Summary
Shade tolerance is an ecological concept used in a wide range of disciplines, from plant physiology to landscaping or gardening. It refers to the strategy of some plants to persist and even ...thrive in environments with low light levels because of the shade produced by the vegetation proximity (e.g. in the understory). Shade tolerance influences the organization, structure, functioning, and dynamics of plant communities. However, little is known about its molecular and genetic basis. By contrast, there is a good understanding on how plants deal with the proximity of other plants, a divergent strategy used by most crops to respond to vegetation proximity. While generally shade‐avoiding species strongly elongate in response to the proximity of other plants, shade‐tolerant species do not. Here we review the molecular mechanisms that control the regulation of hypocotyl elongation in shade‐avoiding species as a reference framework to understand shade tolerance. Comparative studies indicate that shade tolerance is implemented by components also known to regulate hypocotyl elongation in shade‐avoiding species. These components, however, show differential molecular properties that explain how, in response to the same stimulus, shade‐avoiding species elongate while shade‐tolerant ones do not.
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