Genomic and metagenomic investigations have recently led to the delineation of a novel class of natural products called ribosomally synthesized and post-translationally modified peptides (RiPPs). ...RiPPs are ubiquitous among living organisms and include pharmaceutically relevant compounds such as antibiotics and toxins. A prominent example is polytheonamide A, which exhibits numerous post-translational modifications, some of which were unknown in ribosomal peptides until recently. Among these post-translational modifications, C-methylations have been proposed to be catalyzed by two putative radical S-adenosylmethionine (rSAM) enzymes, PoyB and PoyC. Here we report the in vitro activity of PoyC, the first B12-dependent rSAM enzyme catalyzing peptide Cβ-methylation. We show that PoyC catalyzes the formation of S-adenosylhomocysteine and 5′-deoxyadenosine and the transfer of a methyl group to l-valine residue. In addition, we demonstrate for the first time that B12-rSAM enzymes have a tightly bound MeCbl cofactor that during catalysis transfers a methyl group originating from S-adenosyl-l-methionine. Collectively, our results shed new light on polytheonamide biosynthesis and the large and emerging family of B12-rSAM enzymes.
In this volume, acknowledged experts present state of the art reviews and empirical data on how aging affects personal communication, and how technology can contribute to improving communication ...efficacy. Chapters are divided into three sections. The first section provides a basic overview of issues in this field. The second section deals with socio-cultural issues. The final section addresses issues around training and compensation. The volume contains new research on heretofore unexplored areas within the field of aging, such as: computer use and design, internet use, and computer literacy. For gerontologists, psychologists, and other professionals interested in aging.
This open-access book aims to highlight the coming surge of 5G network-based applications and predicts that the centralized networks and their current capacity will be incapable of meeting the ...demands. The book emphasizes the benefits and challenges associated with the integration of 5G networks with varied applications. Further, the book gathers and investigates the most recent 5G-based research solutions that handle security and privacy threats while considering resource-constrained wireless devices. The information, applications, and recent advances discussed in this book will serve to be of immense help to practitioners, database professionals, and researchers.
Extended reduction of Mo2Cp2(μ-Cl)(μ-P t Bu2)(NO)2 (1) with Na(Hg) in acetonitrile (MeCN) at room temperature resulted in an unprecedented full cleavage of the CN bond of a coordinated MeCN ...molecule to yield the vinylidene derivative NaMo2Cp2(μ-P t Bu2)(μ-CCH2)(NO)2, which upon protonation with (NH4)PF6 gave the ethylidyne complex Mo2Cp2(μ-P t Bu2)(μ-CMe)(NO)2 Mo1–Mo2 = 2.9218(2) Å in a selective and reversible way. Controlled reduction of 1 at 273 K yielded instead, after protonation, the 30-electron acetamidinate complex Mo2Cp2(μ-P t Bu2)(μ-κN:κN′-HNCMeNH)(μ-NO)PF6 Mo1–Mo2 = 2.603(2) Å, in a process thought to stem from the paramagnetic MeCN-bridged intermediate Mo2Cp2(μ-P t Bu2)(μ-NCMe)(NO)2, followed by a complex sequence of elementary steps including cleavage of the NO bond of a nitrosyl ligand.
Language and Literacy Development: English Learners with Communication Disorders, from Theory to Application, Second Edition brings you the most useful, up-to-date information on best practices for ...English learners (ELs) with communication disorders from a variety of backgrounds--how to conduct assessment, intervention, and progress monitoring. The first edition of this text gave a comprehensive overview of the theory and practice of serving ELs with communication disorders, and the second edition is expanded to show the nuts and bolts of how to meet ELs' needs and how professionals can support their success at school.This text emphasizes collaboration between speech-language pathology (SLP) and English for speakers of other languages (ESOL) professionals. More importantly, it shows how to apply the knowledge and implement the mechanics and practicalities of assessment, intervention, and progress monitoring.
Oxidation by water with H2 liberation is highly desirable, as it can serve as an environmentally friendly way for the oxidation of organic compounds. Herein, we report the oxidation of alkenes with ...water as the oxidant by using a catalyst combination of a dearomatized acridine-based PNP-Ru complex and indium(III) triflate. Compared to traditional Wacker-type oxidation, this transformation avoids the use of added chemical oxidants and liberates hydrogen gas as the only byproduct.
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