BackgroundCollenchyma has remained in the shadow of commercially exploited mechanical tissues such as wood and fibres, and therefore has received little attention since it was first described. ...However, collenchyma is highly dynamic, especially compared with sclerenchyma. It is the main supporting tissue of growing organs with walls thickening during and after elongation. In older organs, collenchyma may become more rigid due to changes in cell wall composition or may undergo sclerification through lignification of newly deposited cell wall material. While much is known about the systematic and organographic distribution of collenchyma, there is rather less information regarding the molecular architecture and properties of its cell walls.Scope and conclusionsThis review summarizes several aspects that have not previously been extensively discussed including the origin of the term ‘collenchyma’ and the history of its typology. As the cell walls of collenchyma largely determine the dynamic characteristics of this tissue, I summarize the current state of knowledge regarding their structure and molecular composition. Unfortunately, to date, detailed studies specifically focusing on collenchyma cell walls have not been undertaken. However, generating a more detailed understanding of the structural and compositional modifications associated with the transition from plastic to elastic collenchyma cell wall properties is likely to provide significant insights into how specific configurations of cell wall polymers result in specific functional properties. This approach, focusing on architecture and functional properties, is likely to provide improved clarity on the controversial definition of collenchyma.
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► We describe the recently reported syntheses of 3-difluoromethyl pyrazoles. ► We outline the use of FAR reagents as difluoromethyl-transfer reagents. ► We detail the influence of the ...reaction conditions on regioselectivity. ► We show applications for the preparation of agrochemical ingredients.
Fluorine, the most electronegative element plays nowadays a key role in pharmaceutical, agrochemical and material sciences. It has been estimated that the number of fluorinated compounds currently under development represents some 30–50% of the total active ingredients in development. The search for new active substances with improved efficacy, lower mammalian toxicity, more favourable environmental profile and lower cost is a truly challenging task for R&D chemists within the crop protection companies. The present review will give an overview on the synthesis of pyrazoles bearing novel fluorinated substituents.
Brown algal phlorotannins are structural analogs of condensed tannins in terrestrial plants and, like plant phenols, they have numerous biological functions. Despite their importance in brown algae, ...phlorotannin biosynthetic pathways have been poorly characterized at the molecular level. We found that a predicted type III polyketide synthase in the genome of the brown alga Ectocarpus siliculosus, PKS1, catalyzes a major step in the biosynthetic pathway of phlorotannins (i.e., the synthesis of phloroglucinol monomers from malonyl-CoA). The crystal structure of PKS1 at 2.85-Å resolution provided a good quality electron density map showing a modified Cys residue, likely connected to a long chain acyl group. An additional pocket not found in other known type III PKSs contains a reaction product that might correspond to a phloroglucinol precursor. In vivo, we also found a positive correlation between the phloroglucinol content and the PKS III gene expression level in cells of a strain of Ectocarpus adapted to freshwater during its reacclimation to seawater. The evolution of the type III PKS gene family in Stramenopiles suggests a lateral gene transfer event from an actinobacterium.
Since the first attempt to administer insulin orally in humans more than 90 years ago, the oral delivery of macromolecular drugs (> 1000 g/mol) has been rather disappointing. Although several ...clinical pilot studies have demonstrated that the oral absorption of macromolecules is possible, the bioavailability remains generally low and variable. This article reviews the formulations and biopharmaceutical aspects of orally administered biomacromolecules on the market and in clinical development for local and systemic delivery. The most successful approaches for systemic delivery often involve a combination of enteric coating, protease inhibitors and permeation enhancers in relatively high amounts. However, some of these excipients have induced local or systemic adverse reactions in preclinical and clinical studies, and long-term studies are often missing. Therefore, strategies aimed at increasing the oral absorption of macromolecular drugs should carefully take into account the benefit-risk ratio. In the absence of specific uptake pathways, small and potent peptides that are resistant to degradation and that present a large therapeutic window certainly represent the best candidates for systemic absorption. While we acknowledge the need for systemically delivering biomacromolecules, it is our opinion that the oral delivery to local gastrointestinal targets is currently more promising because of their accessibility and the lacking requirement for intestinal permeability enhancement.
We report herein the in situ generation of difluoromethoxylated ketenimines. This novel intermediate is readily obtained from the corresponding oxime through a Beckmann rearrangement. The reactivity ...potential of this species is demonstrated as it easily undergoes addition of various nucleophiles, with a great modularity of the starting oxime. The broad applicability of this transformation leads to a chemical library of original molecules bearing −OCHF2, an Emergent Fluorinated Group (EFG).
This paper studies the optimal fiscal treatment of assisted reproductive technologies (ART) in an economy where individuals differ in their reproductive capacity (or fecundity) and in their wage. We ...find that the optimal ART tax policy varies with the postulated social welfare criterion. Utilitarianism redistributes only between individuals with unequal fecundity and wages but not between parents and childless individuals. To the opposite, ex post egalitarianism (which gives absolute priority to the worst‐off in realized terms) redistributes from individuals with children toward those without children, and from individuals with high fecundity toward those with low fecundity, so as to compensate for both the monetary cost of ART and the disutility from involuntary childlessness resulting from unsuccessful ART investments. Under asymmetric information and in order to solve for the incentive problem, utilitarianism recommends to either tax or subsidize ART investments of low‐fecundity‐low‐productivity individuals at the margin, depending on the degree of complementarity between fecundity and ART in the fertility technology. On the opposite, ex post egalitarianism always recommends marginal taxation of ART.
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Surveying techniques such as terrestrial laser scanner have recently been used to measure surface changes via 3D point cloud (PC) comparison. Two types of approaches have been ...pursued: 3D tracking of homologous parts of the surface to compute a displacement field, and distance calculation between two point clouds when homologous parts cannot be defined. This study deals with the second approach, typical of natural surfaces altered by erosion, sedimentation or vegetation between surveys. Current comparison methods are based on a closest point distance or require at least one of the PC to be meshed with severe limitations when surfaces present roughness elements at all scales. To solve these issues, we introduce a new algorithm performing a direct comparison of point clouds in 3D. The method has two steps: (1) surface normal estimation and orientation in 3D at a scale consistent with the local surface roughness; (2) measurement of the mean surface change along the normal direction with explicit calculation of a local confidence interval. Comparison with existing methods demonstrates the higher accuracy of our approach, as well as an easier workflow due to the absence of surface meshing or Digital Elevation Model (DEM) generation. Application of the method in a rapidly eroding, meandering bedrock river (Rangitikei River canyon) illustrates its ability to handle 3D differences in complex situations (flat and vertical surfaces on the same scene), to reduce uncertainty related to point cloud roughness by local averaging and to generate 3D maps of uncertainty levels. We also demonstrate that for high precision survey scanners, the total error budget on change detection is dominated by the point clouds registration error and the surface roughness. Combined with mm-range local georeferencing of the point clouds, levels of detection down to 6mm (defined at 95% confidence) can be routinely attained in situ over ranges of 50m. We provide evidence for the self-affine behaviour of different surfaces. We show how this impacts the calculation of normal vectors and demonstrate the scaling behaviour of the level of change detection. The algorithm has been implemented in a freely available open source software package. It operates in complex 3D cases and can also be used as a simpler and more robust alternative to DEM differencing for the 2D cases.
Motile and non-motile (primary) cilia are nearly ubiquitous cellular organelles. The dysfunction of cilia causes diseases known as ciliopathies. The number of reported ciliopathies (currently 35) is ...increasing, as is the number of established (187) and candidate (241) ciliopathy-associated genes. The characterization of ciliopathy-associated proteins and phenotypes has improved our knowledge of ciliary functions. In particular, investigating ciliopathies has helped us to understand the molecular mechanisms by which the cilium-associated basal body functions in early ciliogenesis, as well as how the transition zone functions in ciliary gating, and how intraflagellar transport enables cargo trafficking and signalling. Both basic biological and clinical studies are uncovering novel ciliopathies and the ciliary proteins involved. The assignment of these proteins to different ciliary structures, processes and ciliopathy subclasses (first order and second order) provides insights into how this versatile organelle is built, compartmentalized and functions in diverse ways that are essential for human health.
A stereoselective method for the synthesis of axially chiral biaryl scaffolds by CH bond functionalization was accomplished using chiral sulfoxide both as the directing group enabling the ...regioselective activation of a CH bond and as the chiral auxiliary generating an asymmetric environment in the coordination sphere of the metal complex. We have demonstrated the directing ability of the p‐tolylsulfinyl group in promoting the Pd(II)‐catalyzed CH olefination of biphenyls.
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