Studies of Properties of Derivatives of 1-Phospha-5-Aza-2,6,9-Trioxabicyclo[3.3.3]
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Lactide/^Caprolactone Polymerization Behavior of Monomeric Aryloxytitanatrane
698 Bull. Korean Chem. Soc. 2007, Vol. 28, No. 4 Notes Synthesis, X-ray Structure, and /-Lactide/^Caprolactone Polymerization Behavior of Monomeric Aryloxytitanatrane Sang-deok Mun, Younjin Hong, and Youngjo Kim* Department of Chemistry, Chungbuk National University, Cheongju, Chungbuk 361-763, Korea. *E-mail: 가[email protected] Received February 2, 2007 Key Words : Titanatrane, Mononuclear, Ring opening polymerization, Polylactide, Polycaprolactone The chemistry of atrane coordinated by the central nitro polymerization (ROP) of l-lactide (l-LA) or ^caprolactone gen atom as well as all three arms of deprotonated triethanol 任-CL) are now one of popular research fields in the homo amine ligand, imino-2,2',2''-triethanolate, has been inten geneous catalysis. In this regard, a new mononuclear tita- sively studied over the past few decades and its examples are natrane obtained was used as a catalyst for the ROP of l-LA now known across the periodic table.1 Most studies have and £-CL. focused on the use of main group elements such as silicon, The treatment of Ti(O-i-Pr)4 with 1 equivalent of 2,6-di- phosphorus, aluminum, and tin in the formation of atrane.1 tert-butylphenol and 1 equivalent of triethanolamine in THF In view of the well known significant number of similarities gave, after workup, novel mononuclear titanatranes 1 as in the chemistries of tin and titanium, relatively few reports orange-yellow crystals in 81% isolated yield. After recrystal have appeared concerning metallic titanatranes with a lization using toluene, 1 was used as a catalyst for making transannular N—Ti bond from bridgehead N atom in polylactide (PLA) and polycaprolactone (PCL). -
Approach to Site-Selective Protein Modification JUSTIN M
A “Tag-and-Modify” Approach to Site-Selective Protein Modification JUSTIN M. CHALKER, GONC-ALO J. L. BERNARDES, AND BENJAMIN G. DAVIS* Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom RECEIVED ON FEBRUARY 27, 2011 CONSPECTUS ovalent modification can expand a protein's functional capacity. Fluorescent or radioactive labeling, for instance, allows C imaging of a protein in real time. Labeling with an affinity probe enables isolation of target proteins and other interacting molecules. At the other end of this functional spectrum, protein structures can be naturally altered by enzymatic action. ProteinÀprotein interactions, genetic regulation, and a range of cellular processes are under the purview of these post- translational modifications. The ability of protein chemists to install these covalent additions selectively has been critical for elucidating their roles in biology. Frequently the transformations must be applied in a site-specific manner, which demands the most selective chemistry. In this Account, we discuss the development and application of such chemistry in our laboratory. A centerpiece of our strategy is a “tag-and-modify” approach, which entails sequential installation of a uniquely reactive chemical group into the protein (the “tag”) and the selective or specific modification of this group. The chemical tag can be a natural or unnatural amino acid residue. Of the natural residues, cysteine is the most widely used as a tag. Early work in our program focused on selective disulfide formation in the synthesis of glycoproteins. For certain applications, the susceptibility of disulfides to reduction was a limitation and prompted the development of several methods for the synthesis of more stable thioether modifications. -
Electron Transfer and Modification of Oligosilanylsilatranes and Related
This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited. Article pubs.acs.org/Organometallics Electron Transfer and Modification of Oligosilanylsilatranes and Related Derivatives † ‡ § Mohammad Aghazadeh Meshgi, Judith Baumgartner,*, Viatcheslav V. Jouikov,*, † and Christoph Marschner*, † Institut für Anorganische Chemie, Technische Universitaẗ Graz, Stremayrgasse 9, 8010 Graz, Austria ‡ Institut für Chemie, Universitaẗ Graz, Stremayrgasse 9, 8010 Graz, Austria § UMR 6226, Chimie et Photonique Moleculaires,́ Universitéde Rennes 1, 35042 Rennes, France *S Supporting Information ABSTRACT: Several silatranyl -substituted oligosilanes were prepared starting from bis(trimethylsilyl)silatranylsilanide. Electrochemical and theoretical investigations of some oligosilanes revealed that electrooxidation occurs by formation of a short-lived cation radical. This species undergoes structural relaxation to form a pair of conformers, with endo and exo relationships with respect to the Si−N interaction. Reaction of a 1,4-disilatranyl-1,4-disilanide with 1,2- dichlorotetramethyldisilane gave a mixture of cis and trans diastereomers of a cyclohexasilane with the trans isomer showing a diminished Si−N distance. ■ INTRODUCTION along the Si−N dative bond reflects the nature of Si−N − Among hypercoordinated silicon compounds silatranes (Figure bonding. In fact the Si N bonding neither is covalent nor is − 8 1) occupy a prominent position.1 4 The suffix “atrane” was based on intermolecular charge transfer. What happens with this unusual bond upon electron withdrawal, for instance during electrooxidation, is of a great interest (for classical bonds see ref 9) but is not known so far. -
Ncomms12703.Pdf
ARTICLE Received 17 Feb 2016 | Accepted 26 Jul 2016 | Published 2 Sep 2016 DOI: 10.1038/ncomms12703 OPEN Chemoselective synthesis and analysis of naturally occurring phosphorylated cysteine peptides Jordi Bertran-Vicente1, Martin Penkert1,2, Olaia Nieto-Garcia1,2, Jean-Marc Jeckelmann3, Peter Schmieder1, Eberhard Krause1 & Christian P. R. Hackenberger1,2 In contrast to protein O-phosphorylation, studying the function of the less frequent N- and S-phosphorylation events have lagged behind because they have chemical features that prevent their manipulation through standard synthetic and analytical methods. Here we report on the development of a chemoselective synthetic method to phosphorylate Cys side-chains in unprotected peptides. This approach makes use of a reaction between nucleophilic phosphites and electrophilic disulfides accessible by standard methods. We achieve the stereochemically defined phosphorylation of a Cys residue and verify the modification using electron-transfer higher-energy dissociation (EThcD) mass spectrometry. To demonstrate the use of the approach in resolving biological questions, we identify an endogenous Cys phosphorylation site in IICBGlc, which is known to be involved in the carbohydrate uptake from the bacterial phosphotransferase system (PTS). This new chemical and analytical approach finally allows further investigating the functions and significance of Cys phosphorylation in a wide range of crucial cellular processes. 1 Leibniz-Institut fu¨r Molekulare Pharmakologie (FMP), Robert-Ro¨ssle-Str. 10, D-13125 Berlin, Germany. 2 Humboldt-Universita¨t zu Berlin, Institut fu¨r Chemie, Brook-Taylor-Str. 2, D-12489 Berlin, Germany. 3 Institute of Biochemistry and Molecular Medicine, University of Bern, 3012 Bern, Switzerland. Correspondence and requests for materials should be addressed to C.P.R.H. -
Template for Electronic Submission to ACS Journals
Understanding the role of Ti-rich domains in the stabilization of gold nanoparticles on mesoporous silica-based catalysts Alaina Moragues a, Begoña Puértolas b, Álvaro Mayoral c,d, Raúl Arenal c,d, Ana B. Hungría e, Sonia Murcia-Mascarós a, Stuart H. Taylor f, Benjamín Solsona g,*, Tomás Garcíab,*, Pedro Amorós a,* a Institut de Ciència dels Materials, Universitat de València, P.O. Box 22085, 46071 Valencia, Spain. b Instituto de Carboquímica (ICB-CSIC), C/ Miguel Luesma Castán 4, 50018 Zaragoza, Spain. c Laboratorio de Microscopias Avanzadas (LMA), Instituto de Nanociencia de Aragon (INA), Universidad de Zaragoza, Mariano Esquillor, 50018 Zaragoza, Spain. d Fundación Agencia Aragonesa para la Investigación y el Desarrollo (ARAID), María de Luna 11, 50018 Zaragoza, Spain. e Departamento de Ciencia de Materiales, Ingeniería Metalúrgica y Química Inorgánica, Universidad de Cádiz, Campus Río San Pedro, 11510 Puerto Real, Spain. f Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, CF10 3AT Cardiff, United Kingdom. g Departamento de Ingenieria Quimica, Universitat de València, Avenida de la Universitat, 46071 Valencia, Spain. *Corresponding authors at: Institut de Ciència dels Materials, Universitat de València, P.O. Box 22085, 46071 Valencia, Spain (Pedro Amorós). E-mail addresses: [email protected], [email protected], [email protected] 1 ABSTRACT The preparation and stabilization of gold nanoparticles with a precise control of size and dispersion is highly attractive for a variety of applications, and a key aspect is thermal stability of the nanoparticles. This paper focuses on understanding the effect of TiO2-based nanodomains, dispersed on mesoporous silicas, and how they control gold nanoparticle stability. -