The Rigidification of the x-Conjugated System: An Effcient New Strategy Towards Small Bandgap Semi-Conductors

Abstract

A new synthetic approach for the reduction of the bandgap of molecular and polymeric conjugated systems is presented.     

Analysis of kinamycin D-mediated DNA cleavage

Kinamycin D is a potent antitumor antibiotic; however the biological mode of action is poorly understood. Recent efforts suggest the natural product is capable of generating reactive oxygen species under acidic pH to induce DNA damage in the presence of a reducing agent.     

Structural analysis of unstable norbixin isomers guided by pure shift nuclear magnetic resonance

We report the analysis of complex samples obtained during the microwave irradiation/heating of norbixin, which has been identified as a potential therapeutic target for age-related macular degeneration (AMD). In this context, identifying the different isomers that are obtained during its degradation is of primary importance. However, this characterization is challenging because, on the one hand, some of these isomers are unstable, and on the other hand, the ¹H spectra of these isomeric mixtures are poorly resolved. We could successfully apply 1D pure shift experiments to obtain ultrahigh-resolution ¹H nuclear magnetic resonance (NMR) spectra of the norbixin isomer samples and exploit their information content to analyze complementary 2D NMR data and describe accurately their isomeric composition.     

Structural and Functional Analysis of Bacterial Sulfonosphingolipids and Rosette-Inducing Factor 2 (RIF-2) by Mass Spectrometry-Guided Isolation and Total Synthesis

We have analyzed the abundance of bacterial sulfonosphingolipids, including rosette-inducing factors (RIFs), in seven bacterial prey strains by using high-resolution tandem mass spectrometry (HRMS²) and molecular networking (MN) within the Global Natural Product Social Molecular Networking (GNPS) web platform. Six sulfonosphingolipids resembling RIFs were isolated and their structures were elucidated based on comparative MS and NMR studies. Here, we also report the first total synthesis of two RIF-2 diastereomers and one congener in 15 and eight synthetic steps, respectively. For the total synthesis of RIF-2 congeners, we employed a decarboxylative cross-coupling reaction to synthesize the necessary branched α-hydroxy fatty acids, and the Garner-aldehyde approach to generate the capnine base carrying three stereogenic centers. Bioactivity studies in the choanoflagellate Salpingoeca rosetta revealed that the rosette inducing activity of RIFs is inhibited dose dependently by the co-occurring sulfonosphingolipid sulfobacins D and F and that activity of RIFs is specific for isolates obtained from Algoriphagus.     

Transport engineering in microbial cell factories producing plant-specialized metabolites

Transport engineering strategies use altered expression of transporter proteins to change metabolite distribution within an organism. The production of plant specialized metabolites in microbial cell factories encounters a set of challenges that could benefit from the implementation of transport engineering technology. The range of challenges includes premature pathway termination due to secretion of intermediates, feedback inhibition due to inefficient export of final products, low yields in bioconversion processes due to inefficient import of precursors, and poor connectivity between subcellular compartments expressing different parts of complex biosynthetic pathways. We highlight the latest examples of transport engineering in microbial cell factories producing plant specialized metabolites, identify the current knowledge gap, and propose future research for advancing the field.     

Mathematics and science teacher educators' use of representations of practice: A mixed methods study

This study sought to explore math and science teacher educators' use of various media to represent practice within methods courses. There is little understanding of why certain media is used over other representations and the rationale for these choices. Specifically, the study focused on the prevalence and familiarity of teacher educators with comics and animations, standard videos, and 360 videos. This mixed methods study utilized a survey and interviews to ascertain math and science teacher educators' level of familiarity and perceived usefulness of representations of practice. Results indicate that standard video is by far the most used representation of practice in methods classes with three themes explaining this finding: access to representations of practice, dimensions of representation, and pertinacity of using representations. Familiarity with representations of practice relates to teacher educators' perceptions of access thereby indicating a need for teacher educators to have better access to representations. Implications of this study include supporting current literature about the relationship between the level of familiarity and perceived usefulness in media along with the potential need for a central platform that houses these representations of practice resources for teacher educators.     

Nonclassical Crystallization and Size Control of Ultra‐Small MoO2 Nanoparticles in Water

Size tuning for MoO₂ nanoparticles is demonstrated for the first time over a wide range 2–100 nm, through a colloidal route into water. A nucleation‐growth mechanism based on oriented attachment is evidenced to rationalize the impact of two simple synthetic levers: reactant ratio and temperature. The smallest non‐aggregated crystalline MoO₂ nanoparticles are reported, with specific surface area reaching 86 m² g^?1. Size and morphology control, along with the ability to produce, non‐aggregated ultra‐small MoO₂ particles are important for a wide range of applications, such as catalysis and energy storage. To exemplify the importance of size tuning, the impact of downscaling on the electrochemical properties in Li‐ion batteries is investigated.