Volume 5 Issue 8, August 2013

Volume 5 Issue 8

Antibiotic–resistant bacteria are an increasingly important public health concern and the development of new antibiotic drugs — particularly those that act by new mechanisms — is thus of great importance. Now, Benjamin Davis, Hagan Bayley and co-workers have used a single-molecule electrochemical technique to identify potential blockers of the channel-forming proteins that export capsular polysaccharides, which form part of the bacterial defence system, from the cell. The cover image shows the eight-fold symmetrical cyclodextrinbased inhibitor binding to the octameric channel-forming protein.

Article p651; News & Views p642

IMAGE: LEON HARRINGTON AND LINGBING KONG

COVER DESIGN: ALEX WING

Thesis

  • Thesis |

    Thomas Tidwell reflects on the overlooked — but prescient — proposal by the British chemists Arthur Downes and Thomas Blunt for photochemical free-radical formation, decades before Moses Gomberg launched the field of radical chemistry by preparing triphenylmethyl, the first stable organic radical.

    • Thomas Tidwell

Research Highlights

Blogroll

News and Views

  • News & Views |

    Electrochemical sensing of the function of cell-membrane proteins has led to the identification of inhibitors that could provide a new approach to the identification of antimicrobial drugs.

    • Ellis C. O'Neill
    •  & Robert A. Field
  • News & Views |

    Accurately representing molecules with many coupled unpaired electrons is currently impossible using conventional electronic-structure theories. Now, using a recently developed approach, the near-exact quantum wavefunction of the highly complex Mn4CaO5 cluster of photosystem II has been calculated.

    • Jeremy N. Harvey
  • News & Views |

    Heparin is an anionic polysaccharide that has tremendous clinical importance as an anticoagulant. Several dyes have been developed that can detect heparin, and the latest example — named Mallard Blue — has now been shown to have excellent sensing properties under biologically relevant conditions.

    • Zachary Shriver
    •  & Ram Sasisekharan
  • News & Views |

    Macrocycles have been a mainstay of supramolecular chemistry since its beginnings. The latest addition to this rank of host compounds is the result of a simple and high-yielding one-step method that produces a star-shaped macrocycle able to bind anionic guests — and has the potential for generating a wide range of anion-responsive structures.

    • James A. Wisner
  • News & Views |

    Chemists have long been interested in synthesizing compounds that push the boundaries of conventional molecular structure. Incorporating metal centres into the ring unit of highly strained and unsaturated cyclic molecules can help reduce strain — a tactic that has now been used to render a previously inaccessible metallapentalyne isolable.

    • Torsten Beweries
    •  & Uwe Rosenthal

Articles

  • Article |

    Capsular polysaccharides (CPS) enclose many pathogenic strains of Escherichia coli, protecting the bacteria from the host. Here, an extracellular blocker of Wza, a pore-forming protein that transports CPS to the cell surface, has been discovered by single-channel electrical recording. Treatment with the blocker exposes the bacterial cell surface and thereby facilitates killing by the human immune system.

    • Lingbing Kong
    • , Leon Harrington
    • , Qiuhong Li
    • , Stephen Cheley
    • , Benjamin G. Davis
    •  & Hagan Bayley
  • Article |

    Many-electron quantum modelling of the metal clusters in metalloenzymes is a long-standing ambition for theoreticians. Here, using the density matrix renormalization group, the many-electron wavefunctions of the Mn4CaO5 cluster of photosystem II are computed, providing new insights into the electronic structure and reactivity at the level of many-particle quantum mechanics and entanglement.

    • Yuki Kurashige
    • , Garnet Kin-Lic Chan
    •  & Takeshi Yanai
  • Article |

    A general and selective palladium-catalysed cross-coupling of aryl- and alkenyl-bromides with a wide range of alkyl-, aryl- and heteroaryl-lithium reagents is reported. The process proceeds quickly at room temperature, and avoids the notorious lithium–halogen exchange and homocoupling side-reactions commonly associated with these extremely reactive organometallic compounds.

    • Massimo Giannerini
    • , Martín Fañanás-Mastral
    •  & Ben L. Feringa
  • Article |

    Dysprosium alkoxides and dysprosium-doped yttrium alkoxides show very large energy barriers, greater than 800 K, to magnetic relaxation. These barriers arise from the presence of a strongly axial pseudo-octahedral crystal field, which switches off relaxation through the first excited state that typically occurs in single-molecule magnets, and favours a competitive pathway through higher-energy states.

    • Robin J. Blagg
    • , Liviu Ungur
    • , Floriana Tuna
    • , James Speak
    • , Priyanka Comar
    • , David Collison
    • , Wolfgang Wernsdorfer
    • , Eric J. L. McInnes
    • , Liviu F. Chibotaru
    •  & Richard E. P. Winpenny
  • Article |

    Daphenylline is an alkaloid containing a tetra-substituted arene within a sterically compact hexacyclic scaffold. Here, the first total synthesis of daphenylline is described. A gold-catalysed 6-exo-dig cyclization reaction was exploited to construct the bridged 6,6-bicycle at an early stage, the aromatic moiety was forged through a photoinduced olefin isomerization/6π electrocyclization cascade followed by oxidative aromatization.

    • Zhaoyong Lu
    • , Yong Li
    • , Jun Deng
    •  & Ang Li
  • Article |

    Using ab initio simulations external mechanical forces are shown to trigger structural changes to disulfide bridges that result in conformations that are less susceptible to nucleophilic attack. This finding is crucial for the interpretation of recent force microscopy experiments, and could be important for understanding protein regulation.

    • Przemyslaw Dopieralski
    • , Jordi Ribas-Arino
    • , Padmesh Anjukandi
    • , Martin Krupicka
    • , Janos Kiss
    •  & Dominik Marx
  • Article |

    A far-red-fluorescent probe based on a ring-fused BODIPY core that is conjugated to a polyglycerol dendrimer is now reported. The most notable feature of this probe is its long-lasting fluorescence emission with a strikingly low level of blinking in single-molecule-imaging experiments, even in the absence of anti-fading agents such as Trolox.

    • Si Kyung Yang
    • , Xinghua Shi
    • , Seongjin Park
    • , Taekjip Ha
    •  & Steven C. Zimmerman
  • Article |

    Pentalyne — a bicyclic anti-aromatic molecule that contains a strained five-membered ring — is a challenging synthetic target. Incorporation of an osmium centre has been shown to stabilize such features and enable the preparation of two osmapentalyne derivatives. Despite featuring the smallest angles observed so far at a carbyne moiety, these molecules benefit from Möbius aromaticity and reduced ring strain.

    • Congqing Zhu
    • , Shunhua Li
    • , Ming Luo
    • , Xiaoxi Zhou
    • , Yufen Niu
    • , Minglian Lin
    • , Jun Zhu
    • , Zexing Cao
    • , Xin Lu
    • , Tingbin Wen
    • , Zhaoxiong Xie
    • , Paul v. R. Schleyer
    •  & Haiping Xia
  • Article |

    Macrocycles are key compounds in supramolecular chemistry, yet their efficient preparation is an ever present challenge. Now, it has been shown that a C5-symmetric macrocycle, termed ‘cyanostar’, can be formed in high yields on multigram scales in one pot. Cyanostars form unusually strong sandwich complexes with large and weakly coordinating anions and can template the formation of a dialkylphosphate [3]rotaxane.

    • Semin Lee
    • , Chun-Hsing Chen
    •  & Amar H. Flood
  • Article |

    Quinones are key electron acceptors in nature, however, the role of their excited states is not fully understood. Femtosecond spectroscopy and quantum calculations on the prototypical parabenzoquinone radical anion provide insight into quinones’ intrinsic electron-accepting ability, revealing how unbound electronically excited states relax to form the ground-state radical anion.

    • Daniel A. Horke
    • , Quansong Li
    • , Lluís Blancafort
    •  & Jan R. R. Verlet
  • Article |

    Frustrated Lewis pairs have been shown to be capable of heterolysis of strong covalent bonds such as those in molecular hydrogen, and have been used in the hydrogenation of polar multiple bonds. Here, a new type of ansa-aminohydroborane is shown to be active for the partial hydrogenation of alkynes under mild conditions.

    • Konstantin Chernichenko
    • , Ádám Madarász
    • , Imre Pápai
    • , Martin Nieger
    • , Markku Leskelä
    •  & Timo Repo

In Your Element

  • In Your Element |

    Barbara Finlayson-Pitts muses on how chlorine has come to play a role in many aspects of our lives — for better or for worse.

    • Barbara J. Finlayson-Pitts