Toward the Synthesis of Rimarikiamide A

<p>Rimarikiamide A is a linear diterpenoid marine natural product featuring an unusual taurine structural moiety. Rimarikiamide A was isolated from the sea sponge Latrunculia brevis found in the Rimariki Islands in northern New Zealand, and was shown to elicit low μM cytotoxicity against HL-60 cells. Unfortunately, only 400 μg of rimarikiamide A was isolated from 700 g of sea sponge, making the characterisation of the two chiral centres impossible by spectroscopic means. To explore the full potential of rimarikiamide A as a therapeutic agent, the molecule must be synthesised in a stereoselective manner or from a starting material of known stereochemistry, fully characterised, and tested for biological activity. A Barbier coupling of two terpene units is required early in the proposed synthesis of Rimarikiamide A, and previous attempts have failed to generate the desired linear product. In this work, the suitability of a titanium-mediated Barbier coupling was investigated, and proved successful for the generation of the desired linear product.</p>

Toward the Synthesis of Rimarikiamide A

<p>Rimarikiamide A is a linear diterpenoid marine natural product featuring an unusual taurine structural moiety. Rimarikiamide A was isolated from the sea sponge Latrunculia brevis found in the Rimariki Islands in northern New Zealand, and was shown to elicit low μM cytotoxicity against HL-60 cells. Unfortunately, only 400 μg of rimarikiamide A was isolated from 700 g of sea sponge, making the characterisation of the two chiral centres impossible by spectroscopic means. To explore the full potential of rimarikiamide A as a therapeutic agent, the molecule must be synthesised in a stereoselective manner or from a starting material of known stereochemistry, fully characterised, and tested for biological activity. A Barbier coupling of two terpene units is required early in the proposed synthesis of Rimarikiamide A, and previous attempts have failed to generate the desired linear product. In this work, the suitability of a titanium-mediated Barbier coupling was investigated, and proved successful for the generation of the desired linear product.</p>

Phenotypic distribution and selection response for linear-product gene-environment interaction in quantitative traits

Gene-environment interaction is often described by linear phenotypic plasticity but has recently also been expressed as function of the product of genotype and environmental variables. While this model can be fitted in a multiple regression scenario, little has been written on the distribution of the product of breeding values and environment, GE, its expected moments, and the theoretical impact on phenotypic selection. Here we will explore these topics introducing the distribution for GE, its mean and variance, and its expected impact of lowering realized heritability due to is increasing the phenotypic variance.

A New Conceptual ‘Cylinder’ Framework for Sustainable Bioeconomy Systems and Their Actors

Concepts for sustainable bioeconomy systems are gradually replacing the ones on linear product chains. The reason is that continuously expanding linear chain activities are considered to contribute to climate change, reduced biodiversity, over-exploitation of resources, food insecurity, and the double burden of disease. Are sustainable bioeconomy systems a guarantee for a healthy planet? If yes, why, when, and how? In literature, different sustainability indicators have been presented to shed light on this complicated question. Due to high degrees of complexity and interactions of actors in bioeconomy systems, trade-offs and non-linear outcomes became apparent. This fueled the debates about the normative dimensions of the bioeconomy. In particular, the behavior of actors and the utilization of products do not seem to be harmonized according to the environmental, social, and economic pillars of sustainability. Potential conflicts require a new conceptual framework that is here introduced. It consists of a ‘sustainability’ cylinder captured between an inner-cylinder, representing order, and an outer-cylinder for chaos, based on the laws of physics and complex adaptive systems. Such a framework permits (bioeconomy) systems to propagate in the sustainability zone only if they follow helical pathways serving as the new norms. Helices are a combination of two sinusoidal patterns. The first represents here the sustainable behavior of interacting actors and the second the balanced usage of resources and products. The latter counteracts current growth discourses. The applicability of the conceptual cylinder framework is positively verified via 9 cases in Europe, which encompass social-organizational and product-technological innovations. –

Absence of Non-Linear Effects Despite Evidence for Catalyst Aggregation

<p>An in-depth study of the catalytic system, consisting of the enantioselective addition of ZnEt₂ to benzaldehyde with (1<i>R</i>,2<i>S</i>)-(-)-N-Methylephedrine (NME) as chiral ligand, suggests the presence of dimeric and trimeric aggregates, as deduced from product ee vs catalyst loading and NMR investigations (¹H, DOSY). Formation of catalyst aggregate was excluded in earlier studies as this system displays a linear product ee vs ligand ee-correlation, which is usually taken as an indication for the <i>absence</i> of catalyst aggregation. A subsequent theoretical study, using the monomer-dimer competition model we recently have developed, highlights the possible parameter configurations leading to linear product ee vs ligand ee plots – despite the presence of catalyst dimers. It shows that, while the Kagan and Noyori models allow linearity in very specific cases only, a multitude of scenarios may lead to linearity here, especially if heterochiral dimers are catalytically active.</p>

Absence of Non-Linear Effects Despite Evidence for Catalyst Aggregation

<p>An in-depth study of the catalytic system, consisting of the enantioselective addition of ZnEt₂ to benzaldehyde with (1<i>R</i>,2<i>S</i>)-(-)-N-Methylephedrine (NME) as chiral ligand, suggests the presence of dimeric and trimeric aggregates, as deduced from product ee vs catalyst loading and NMR investigations (¹H, DOSY). Formation of catalyst aggregate was excluded in earlier studies as this system displays a linear product ee vs ligand ee-correlation, which is usually taken as an indication for the <i>absence</i> of catalyst aggregation. A subsequent theoretical study, using the monomer-dimer competition model we recently have developed, highlights the possible parameter configurations leading to linear product ee vs ligand ee plots – despite the presence of catalyst dimers. It shows that, while the Kagan and Noyori models allow linearity in very specific cases only, a multitude of scenarios may lead to linearity here, especially if heterochiral dimers are catalytically active.</p>

A mechanism for the extension and unfolding of parallel telomeric G-quadruplexes by human telomerase at single-molecule resolution

Telomeric G-quadruplexes (G4) were long believed to form a protective structure at telomeres, preventing their extension by the ribonucleoprotein telomerase. Contrary to this belief, we have previously demonstrated that parallel-stranded conformations of telomeric G4 can be extended by human and ciliate telomerase. However, a mechanistic understanding of the interaction of telomerase with structured DNA remained elusive. Here, we use single-molecule fluorescence resonance energy transfer (smFRET) microscopy and bulk-phase enzymology to propose a mechanism for the resolution and extension of parallel G4 by telomerase. Binding is initiated by the RNA template of telomerase interacting with the G-quadruplex; nucleotide addition then proceeds to the end of the RNA template. It is only through the large conformational change of translocation following synthesis that the G-quadruplex structure is completely unfolded to a linear product. Surprisingly, parallel G4 stabilization with either small molecule ligands or by chemical modification does not always inhibit G4 unfolding and extension by telomerase. These data reveal that telomerase is a parallel G-quadruplex resolvase.

A mechanism for the extension and unfolding of parallel telomeric G-quadruplexes by human telomerase at single-molecule resolution

Telomeric G-quadruplexes (G4) were long believed to form a protective structure at telomeres, preventing their extension by the ribonucleoprotein telomerase. Contrary to this belief, we have previously demonstrated that parallel-stranded conformations of telomeric G4 can be extended by human and ciliate telomerase. However, a mechanistic understanding of the interaction of telomerase with structured DNA remained elusive. Here, we use single-molecule fluorescence resonance energy transfer (smFRET) microscopy and bulk-phase enzymology to propose a mechanism for the resolution and extension of parallel G4 by telomerase. Binding is initiated by the RNA template of telomerase interacting with the G-quadruplex; nucleotide addition then proceeds to the end of the RNA template. It is only through the large conformational change of translocation following synthesis that the G-quadruplex structure is completely unfolded to a linear product. Surprisingly, parallel G4 stabilization with either small molecule ligands or by chemical modification does not always inhibit G4 unfolding and extension by telomerase. These data reveal that telomerase is a parallel G-quadruplex resolvase.

Semigroups of linear tree languages

A linear tree language of type [Formula: see text] is a set of linear terms, terms in which each variable occurs at most once, of that type. We investigate a semigroup consisting of the collection of all linear tree languages such that products of any element in the collection are nonempty and the operation of the corresponding linear product especially idempotent elements, Green’s relations [Formula: see text], [Formula: see text], and [Formula: see text], and some of its subsemigroups. We discover that this semigroup is neither factorizable nor locally factorizable. We also study the linear product iteration and show that any iteration is idempotent in this semigroup. Moreover, we study a semigroup with the complement of the universe set of the above semigroup together with the same linear product operation.