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Functional Modification Effect of Epoxy Oligomers on the Structure and Properties of Epoxy Hydroxyurethane Polymers

We introduce different ways to solve the actual fragility problem of the epoxy-amine polymers by curing epoxidian oligomers with aliphatic amines without additional heat input. The pathways are the oligomer-oligomeric modification of epoxy resins-epoxy oligomers (EO), with their conversion to oligoethercyclocarbonates (OECC) by carbonization with carbon dioxide. The cocuring of these oligomers as a result of aminolysis competing reactions is “epoxide-amine” (forming a network polymer) and “cyclocarbonate-amine” (forming the linear hydroxyurethane, extending the internodal chains). Formation of internal and intermolecular hydrogen bonds was established on hydroxycarbonates (HA) and linear polyhydroxyurethanes (PHU) model compounds by IR and NMR spectroscopy. The results of the hydrogen bond system formation processes explain the change in the relaxation and physicomechanical properties of hard polymers modified by the epoxy-amine compositions (OECC), containing aromatic and aliphatic links. This paper presents a possible OECC modificator, the optimal EO:OECC ratio and its influence on the cross-link frequency, the polarity, the fragment and chain flexibilities and, as a consequence, the possible stiffness regulation for selected epoxy polymers. Thus, the causes of the increase in deformation-strength and adhesion characteristics were established by a factor of 1.5 to 3.0 due to an increase in cohesive strength (as a result of the combined network operation with covalent and physical bonds), as well as reduction of residual stresses (by adding the aliphatic fragments as additional relaxants), and reducing the defectiveness of the boundary layers (polymer-substrate)

Mapping of UK Biobank clinical codes: Challenges and possible solutions.

ObjectiveThe UK Biobank provides a rich collection of longitudinal clinical data coming from different healthcare providers and sources in England, Wales, and Scotland. Although extremely valuable and available to a wide research community, the heterogeneous dataset contains inconsistent medical terminology that is either aligned to several ontologies within the same category or unprocessed. To make these data useful to a research community, data cleaning, curation, and standardization are needed. Significant efforts to perform data reformatting, mapping to any selected ontologies (such as SNOMED-CT) and harmonization are required from any data user to integrate UK Biobank hospital inpatient and self-reported data, data from various registers with primary care (GP) data. The integrated clinical data would provide a more comprehensive picture of one's medical history.Materials and methodsWe evaluated several approaches to map GP clinical Read codes to International Classification of Diseases (ICD) and Systematized Nomenclature of Medicine Clinical Terms (SNOMED CT) terminologies. The results were compared, mapping inconsistencies were flagged, a quality category was assigned to each mapping to evaluate overall mapping quality.ResultsWe propose a curation and data integration pipeline for harmonizing diagnosis. We also report challenges identified in mapping Read codes from UK Biobank GP tables to ICD and SNOMED CT.Discussion and conclusionSome of the challenges-the lack of precise one-to-one mapping between ontologies or the need for additional ontology to fully map terms-are general reflecting trade-offs to be made at different steps. Other challenges are due to automatic mapping and can be overcome by leveraging existing mappings, supplemented with automated and manual curation

Alchemical FEP Calculations of Ligand Conformer Focusing in Explicit Solvent

Slow rotational degrees of freedom in ligands can make alchemical FEP simulations unreliable due to inadequate sampling. We addressed this problem by introducing a FEP-based protocol of ligand conformer focusing in explicit solvent. Our method involves FEP transformations between conformers using equilibrium dihedral angle as a reaction coordinate and provides the cost of “focusing” on one specific conformational state that binds to a protein. The calculated conformer focusing term made a considerable difference of 5–10 kJ/mol in computed relative binding free energies of studied Syk inhibitors and significantly improved the resulting accuracy of predictions

Quantifying Possible Routes for SpnF-Catalyzed Formal Diels–Alder Cycloaddition

The Diels–Alder reaction is a cornerstone of modern organic synthesis. Despite this, it remains essentially inaccessible to biosynthetic approaches. Only a few natural enzymes catalyze even a formal [4 + 2] cycloaddition, and it remains uncertain if any of them proceed via the Diels–Alder mechanism. In this study, we focus on the [4 + 2] cycloaddition step in the biosynthesis of spinosyn A, a reaction catalyzed by SpnF enzyme, one of the most promising “true Diels–Alderase” candidates. The four currently proposed mechanisms (including the Diels–Alder one) for this reaction in water (as a first-order approximation of the enzymatic reaction) are evaluated by an exhaustive quantum mechanical search for possible transition states (728 were found in total). We find that the line between the recently proposed bis-pericyclic [<i>J. Am. Chem. Soc.</i> <b>2016</b>, <i>138</i> (11), 3631] and Diels–Alder routes is blurred, and favorable transition states of both types may coexist. Application of the Curtin–Hammett principle, however, reveals that the bis-pericyclic mechanism accounts for ∼83% of the reaction flow in water, while the classical Diels–Alder mechanism contributes only ∼17%. The current findings provide a route for modeling this reaction inside the SpnF active site and inferring the catalytic architecture of possible Diels–Alderases

Quantifying Possible Routes for SpnF-Catalyzed Formal Diels–Alder Cycloaddition

The Diels–Alder reaction is a cornerstone of modern organic synthesis. Despite this, it remains essentially inaccessible to biosynthetic approaches. Only a few natural enzymes catalyze even a formal [4 + 2] cycloaddition, and it remains uncertain if any of them proceed via the Diels–Alder mechanism. In this study, we focus on the [4 + 2] cycloaddition step in the biosynthesis of spinosyn A, a reaction catalyzed by SpnF enzyme, one of the most promising “true Diels–Alderase” candidates. The four currently proposed mechanisms (including the Diels–Alder one) for this reaction in water (as a first-order approximation of the enzymatic reaction) are evaluated by an exhaustive quantum mechanical search for possible transition states (728 were found in total). We find that the line between the recently proposed bis-pericyclic [<i>J. Am. Chem. Soc.</i> <b>2016</b>, <i>138</i> (11), 3631] and Diels–Alder routes is blurred, and favorable transition states of both types may coexist. Application of the Curtin–Hammett principle, however, reveals that the bis-pericyclic mechanism accounts for ∼83% of the reaction flow in water, while the classical Diels–Alder mechanism contributes only ∼17%. The current findings provide a route for modeling this reaction inside the SpnF active site and inferring the catalytic architecture of possible Diels–Alderases