Publications

Antisymbiotic Self‐Assembly and Dynamic Behavior of Metallamacrocycles with Allylic Corners

Hip to be square: Tetranuclear metallamacrocycles containing Pd–allyl and either Pd(dppp) or Pt(dppp) moieties (dppp=1,3-bis(diphenylphosphino)propane) have been obtained from the selective combination of three different building blocks. The study of their unusual dynamic behavior demonstrated the equilibrium between the self-assembled supramolecules and their components (see scheme). Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Experimental Investigation of an Oxidative C−C Coupling Reaction Catalyzed by HAuCl₄

Abstract Reaction monitoring by electrospray (ESI) mass spectrometry (MS) is a valuable technique to investigate reaction mechanisms. It allows a glimpse into the reacting solution and the characterization of transient intermediates by tandem mass spectrometry. Herein we studied an intriguing gold(III)‐catalyzed synthesis of dicoumarins which includes a combination of hydroarylation and homocoupling steps. Reactants and products could be detected in positive mode. In negative mode, some species corroborating proposed transient intermediates could be detected by direct infusion ESI of reacting solutions. The ions were characterized by accurate mass determinations and gas‐phase fragmentation. Thus, indications for the nature and ligand sphere of reaction intermediates in the catalytic cycle could be collected.

CCDC 1411721: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CCDC 836993: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CCDC 699741: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CCDC 1520087: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

DNA‐Based Phosphane Ligands

Abstract In order to expand the repertoire of DNA sequences specifically interacting with transition metals, we report here the first examples of DNA sequences carrying mono‐ and bidentate phosphane ligands as well as P,N‐ligands. Aminoalkyl‐modified oligonucleotides have been reacted at predetermined internal sites with carboxylate derivatives of pyrphos, BINAP and phosphinooxazoline (PHOX) 2 b – d . Carbodiimide coupling in the presence of N ‐hydroxysuccinimide provided the DNA–ligand conjugates in 38–78 % yield. Phosphane‐containing oligonucleotides and their phosphane sulfide analogues were characterized by mass spectrometry (MALDI‐TOF and FT‐ICR‐ESI) and their stability after purification and isolation was systematically investigated. While DNA‐appended pyrphos ligand was quickly oxidized, BINAP and PHOX conjugates showed high stabilities, making them useful precursors for incorporation of transition metals into DNA.

Enantiomerenreine [M₆L₁₂]‐ oder [M₁₂L₂₄]‐Polyeder aus flexiblen Bis(pyridin)‐Liganden

Abstract Die koordinationsgetriebene Selbstorganisation ist eine der leistungsfähigsten Strategien zum Aufbau nanometergroßer diskreter (supra‐)molekularer Aggregate. Hier berichten wir über die Verwendung von zwei konstitutionsisomeren Bis(pyridin)‐Liganden auf der Basis von BINOL zu diesem Zweck. Je nach Substitutionsmuster des BINOL‐Gerüsts bilden sich bei der Koordination an Pd II ‐Ionen enantiomerenreine, endo ‐ oder exo ‐funktionalisierte sechs‐ oder zwölfkernige metallosupramolekulare Polyeder mit einem chiralen Gerüst. Die Aggregate wurden mittels NMR, MS, DLS, TEM und EELS sowie ECD charakterisiert. Die außergewöhnlich hohen molaren Circulardichroismen der Komplexe konnten durch den Vergleich experimenteller ECD‐Daten mit simulierten Daten (vereinfachte Tamm‐Dancoff‐Näherung zur zeitabhängigen DFT) nachvollzogen werden. Hervorzuheben ist ferner, dass die Selbstorganisationsprozesse vollständig selektiv im Sinne einer “narzisstischen” Selbsterkennung ablaufen, obwohl die Liganden ein hohes Maß an Rotationsfreiheit um die zentrale Aryl‐Aryl‐Bindung aufweisen.

Mass spectrometry as a tool in dendrimer chemistry: from self‐assembling dendrimers to dendrimer gas‐phase host–guest chemistry

Abstract Mass spectrometry has played a significant role in dendrimer chemistry, because it serves as an excellent analytical means to determine the purity and analyze the nature of defects even for higher generations. However, a mass spectrometer can also be used as a laboratory to study isolated dendrimer molecules in the gas phase or their host–guest complexes. Since the properties of molecules under environment‐free conditions are often quite different from those in solution, their gas‐phase chemistry provides valuable new insight into properties which cannot easily be studied in solution. This article summarizes some of our work on characterizing self‐assembling metallo‐supramolecular dendrimers, on analyzing ionization artifacts, on the differentiation between several, sometimes even isomeric defects through tandem MS experiments, and finally on the analysis of a surprisingly clear dendritic effect occurring in the fragmentation of dendritic host–guest complexes. Copyright © 2006 John Wiley & Sons, Ltd.

The SAVED domain of the type III CRISPR protease CalpL is a ring nuclease

Abstract Prokaryotic CRISPR-Cas immune systems detect and cleave foreign nucleic acids. In type III CRISPR-Cas systems, the Cas10 subunit of the activated recognition complex synthesizes cyclic oligoadenylates (cOAs), second messengers that activate downstream ancillary effector proteins. Once the viral attack has been weathered, elimination of extant cOA is essential to limit the antiviral response and to allow cellular recovery. Various families of ring nucleases have been identified, specializing in the degradation of cOAs either as standalone enzymes or as domains of effector proteins. Here we describe the ring nuclease activity inherent in the SAVED domain of the cA 4 -activated CRISPR Lon protease CalpL. We characterize the kinetics of cA 4 cleavage and identify key catalytic residues. We demonstrate that cA 4 -incuced oligomerization of CalpL is essential not only for activation of the protease, but is also required for nuclease activity. Further, the nuclease activity of CalpL poses a limitation to the protease reaction, indicating a mechanism for regulation of the CalpL/T/S signaling cascade. This work is the first demonstration of a catalytic SAVED domain and gives new insights into the dynamics of transcriptional adaption in CRISPR defense systems which are not aimed at abortive infection but rather at a reversible adaption to phage attack.

Light‐Induced Formation of G‐Quadruplex DNA Secondary Structures

A little light release: Temporarily blocked ("caged") dG nucleosides that can be incorporated into oligodeoxynucleotides are presented (see figure). Their hydrogen-bond-recognition site is inaccessible in the inactive form; this prevents, for example, the formation of secondary structures. Light can trigger the release of the unmodified oligonucleotide and thus induce correct folding. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2268/2005/z500198_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

CCDC 1411725: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CCDC 1919440: Experimental Crystal Structure Determination

CCDC 1893945: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Dehydration and Dehydrogenation of Alcohols with Mononuclear Cationic Vanadium Oxides in the Gas Phase and Energetics of VO<i>_n</i>H^0/+ (<i>n</i> = 2, 3)

Abstract The ion/molecule reactions of selected alcohols with the vanadium oxide cations VO + and VO 2 + are studied by Fourier‐transform ion‐cyclotron resonance (FT‐ICR) mass spectrometry. Dehydrogenation is the dominating reaction pathway for methanol and allyl alcohols. With larger or less unsaturated alcohols, dehydration and carbocation formations prevail. While the valence in VO + remains unchanged during alcohol dehydrogenation, VO 2 + is reduced to V III . Thermochemical data for VO 2 H 0/+ , VO 3 H and VO 3 H 2 + are derived by means of ICR bracketing. The experimental results are further complemented by ab initio calculations using density functional theory. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2007)

[2.2]Paracyclophane bis(pyridine)-based metallosupramolecular rhombs in the gas phase: Competitive cleavage of non-covalent and weak covalent bonds

The gas-phase fragmentation behavior of self-assembled metallo-supramolecular rhombs based on an unusual chiral [2.2]paracyclophane bis(pyridine) ligand is studied by collision-induced dissociation mass spectrometry. The fragmentation patterns strongly depend on the charge state of the respective mass-selected aggregate. For the doubly charged ions, simple symmetric fragmentation is observed in full accordance with previous results reported for related metallo-supramolecular species. The triply charged species cleaves unsymmetrically which can be rationalized by a preferred formation of ions with low charge density. CID of the quadruply charged rhomb reveals a complex fragmentation. Besides ligand oxidation to the radical cation, facile cleavage of the central covalently bound part of the [2.2]paracyclophane ligand takes place which is even preferred over rupture of the weak dative pyridine-Pd bond.

CCDC 971933: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Gas-phase H/D exchange of the protonated serine octamer cluster: “Ion ping pong” of populations A and B