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Volume 10 Issue 3, March 2018

The targeted delivery of cells and therapeutics with systems that respond to disease-related biomarkers could improve the efficiency and efficacy of drug delivery and regenerative medicine. A team led by Cole A. DeForest has now made a range of stimuli-responsive hydrogels that collectively provide all possible YES/OR/AND logical outputs from input combinations involving an enzyme, a reducing agent and light. The sequential and environmentally stimulated release of multiple cell lines was demonstrated with these hydrogels. The image shown on the cover of this issue depicts the concept of a cross-linked polymer hydrogel network in which there are cyclic moieties containing scissile bonds that respond to the appropriate stimuli.

Article p251



News & Views

  • Rational engineering of biosynthetic assembly lines for production of new compounds is an attractive prospect, yet it presents many challenges. Learning from biology, some of the rules for expanding the chemical diversity of non-ribosomal peptides have been uncovered in two recent studies.

    • Binuraj R. K. Menon
    • Matthew Jenner
    News & Views


  • An arene-anchored uranium complex has recently been shown to serve as efficient electrocatalyst for the conversion of water into dihydrogen. Now, the crucial role of the arene moiety in enabling catalytic activity — unusual for uranium — has been explored, providing important insight for the design of improved electrocatalysts.

    • Marinella Mazzanti
    News & Views
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  • Biomaterials that respond to precise combinations of environmental cues represent an important technology for tissue engineering and next-generation drug delivery systems. Now, a modular framework to programme material degradation following Boolean logic has been demonstrated by specifying the molecular architecture and connectivity of orthogonal stimuli-labile moieties within hydrogel cross-linkers.

    • Barry A. Badeau
    • Michael P. Comerford
    • Cole A. DeForest
  • An arene-anchored uranium(III) complex that facilitates the electrocatalytic formation of H2 from H2O has now been shown to involve redox-cooperativity between the uranium centre and its covalently bound mesitylene ligand. The oxidative addition of H2O to the uranium catalyst is a concerted two-electron reaction — atypical for f-block metals.

    • Dominik P. Halter
    • Frank W. Heinemann
    • Karsten Meyer
  • Understanding how a supporting material can change the surface chemistry of the nanoparticle catalysts that it hosts is critical to tuning catalytic properties. Experimental Hammett studies and density functional theory calculations show that differences in reactivity can be attributed to differences in the electron density at metal active sites, which arises from differences in electron donation from the support.

    • Gaurav Kumar
    • Luke Tibbitts
    • Bert D. Chandler
  • Peptides derived from non-ribosomal peptide synthetases (NRPS) are an important class of pharmaceutically relevant drugs. However, no general rules for the modification of NRPS or the generation of artificial NRPS are known. Now, a new strategy for the modification of NRPS has been developed that uses defined exchange units that are fused at specific positions connecting the condensation and adenylation domains.

    • Kenan A. J. Bozhüyük
    • Florian Fleischhacker
    • Helge B. Bode
  • Nonribosomal peptide synthetases (NRPSs) produce vital natural products but have proven recalcitrant to biosynthetic engineering. Now, a combination of yeast surface display and fluorescence-activated cell sorting (FACS) has been used to reprogram an L-Phe-incorporating module for β-Phe. The resulting module is highly selective and functions efficiently in NRPS pathways.

    • David L. Niquille
    • Douglas A. Hansen
    • Donald Hilvert
  • Alkali-metal-rich compositions (for example, Li[LixM1–x]O2) are promising battery cathode materials that exhibit oxygen redox, which provides additional charge capacity. It is thought to occur in compounds containing alkali ions in the transition metal layers and featuring Li+–O(2p)–Li+ interactions; however, now it is observed in Na2/3[Mg0.28Mn0.72]O2, in which Mg2+ ions are present in the transition metal layer.

    • Urmimala Maitra
    • Robert A. House
    • Peter G. Bruce
  • Complex interfacial supramolecular architectures promise unique physical and chemical properties, but are challenging to make. Now, it has been shown that a simple organic precursor can undergo a convergent multi-step on-surface transformation to give more complex building blocks that assemble into a semi-regular Archimedean tessellation with long-range order.

    • Yi-Qi Zhang
    • Mateusz Paszkiewicz
    • Florian Klappenberger
  • Singlet fission may one day allow solar cells to produce two excited electrons with one photon. Now, by comparison of the time-resolved photoluminescence and sensitized triplet–triplet annihilation of a tetracene derivative, it has been shown that—contrary to previous reports—the excimer state is a trap, and not a necessary intermediate for singlet fission.

    • Cameron B. Dover
    • Joseph K. Gallaher
    • Timothy W. Schmidt
  • Enzymes that form a metabolic pathway in which the product of one enzyme is the substrate for the next have now been shown to associate through a process of sequential, directed chemotactic movement. The extent of enzyme migration is proportional to the exposure time to the substrate gradient.

    • Xi Zhao
    • Henri Palacci
    • Ayusman Sen
  • Proteins have the potential to serve as powerful scaffolds that control the catalytic activity and selectivity of organometallic centres; however, new methods are needed to optimize artificial metalloenzymes. Now, an efficient approach for evolving the activity and selectivity of artificial metalloenzymes has been demonstrated using dirhodium cyclopropanases. This approach does not require structural or mechanistic data to guide mutagenesis.

    • Hao Yang
    • Alan M. Swartz
    • Jared C. Lewis
  • A renewed interest in C–H bond activation has developed on account of the recent increased availability of shale gas. Now, using a combination of surface science, microscopy, theory and nanoparticle studies, the ability of coke-resistant Pt/Cu single-atom alloys to efficiently activate C–H bonds in alkanes has been demonstrated under realistic catalytic conditions.

    • Matthew D. Marcinkowski
    • Matthew T. Darby
    • E. Charles H. Sykes
  • Aminopalladation is a key step in a number of carbon–nitrogen bond-forming processes, but carrying out this step with intermolecular anti-Markovnikov selectivity has remained difficult. Such a process has now been developed by using an anionic palladium catalyst to generate terminal carbon–nitrogen bonds from alkenes.

    • Daniel G. Kohler
    • Samuel N. Gockel
    • Kami L. Hull
  • Intracellular asymmetric transfer hydrogenation catalysis using Os(II) complexes has now been demonstrated and offers a new approach for selectively killing cancer cells. Enantiomers of Os(II) arene catalysts can penetrate cell membranes enabling the reduction of pyruvate to D- or L-lactate using formate as a hydride source, with high enantioselectivity.

    • James P. C. Coverdale
    • Isolda Romero-Canelón
    • Peter J. Sadler
  • According to the entatic-state principle, distortions of the coordination geometry of a reacting compound can optimize the energies of starting and final states to improve reaction rates. Here, the entatic-state principle is observed to apply to photoactive copper complexes that have a constrained ligand geometry, resulting in very short charge-transfer state lifetimes.

    • B. Dicke
    • A. Hoffmann
    • S. Herres-Pawlis
  • Most steps in peptidoglycan biosynthesis are understood, but the lipid II binding properties to the flippases MurJ and FtsW remain unknown. Now, it has been shown that lipid II exhibits preferential binding to MurJ, which is modulated by ramoplanin and cardiolipins. These insights into the lipid II binding determinants suggest roles for lipids in regulating substrate binding.

    • Jani Reddy Bolla
    • Joshua B. Sauer
    • Carol V. Robinson
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