Science
http://www.sciencemag.org/content/339/6116/189.full?rss=1
Bartosz Lewandowski1,Guillaume De Bo1,John W. Ward1,Marcus Papmeyer1,Sonja Kuschel1,María J. Aldegunde2,Philipp M. E. Gramlich2,Dominik Heckmann2,Stephen M. Goldup2,Daniel M. D’Souza2,Antony E. Fernandes2,David A. Leigh1,2,*
The ribosome builds proteins by joining together amino acids in an order
determined by messenger RNA. Here, we report on the
design, synthesis, and operation of an
artificial small-molecule machine that travels along a molecular strand,
picking up
amino acids that block its path, to synthesize a
peptide in a sequence-specific manner. The chemical structure is based
on
a rotaxane, a molecular ring threaded onto a
molecular axle. The ring carries a thiolate group that iteratively
removes amino
acids in order from the strand and transfers
them to a peptide-elongation site through native chemical ligation. The
synthesis
is demonstrated with ~1018 molecular
machines acting in parallel; this process generates milligram quantities
of a peptide with a single sequence confirmed
by tandem mass spectrometry.
Tuesday, January 15, 2013
Bio-Inspired Polymer Composite Actuator and Generator Driven by Water Gradients
Science
http://www.sciencemag.org/content/339/6116/186.full
Combining both a rigid matrix (polypyrrole) and a dynamic network (polyol-borate), strong and flexible polymer films were developed that can exchange water with the environment to induce film expansion and contraction, resulting in rapid and continuous locomotion. The film actuator can generate contractile stress up to 27 megapascals, lift objects 380 times heavier than itself, and transport cargo 10 times heavier than itself. We have assembled a generator by associating this actuator with a piezoelectric element. Driven by water gradients, this generator outputs alternating electricity at ~0.3 hertz, with a peak voltage of ~1.0 volt. The electrical energy is stored in capacitors that could power micro- and nanoelectronic devices.
http://www.sciencemag.org/content/339/6116/186.full
Combining both a rigid matrix (polypyrrole) and a dynamic network (polyol-borate), strong and flexible polymer films were developed that can exchange water with the environment to induce film expansion and contraction, resulting in rapid and continuous locomotion. The film actuator can generate contractile stress up to 27 megapascals, lift objects 380 times heavier than itself, and transport cargo 10 times heavier than itself. We have assembled a generator by associating this actuator with a piezoelectric element. Driven by water gradients, this generator outputs alternating electricity at ~0.3 hertz, with a peak voltage of ~1.0 volt. The electrical energy is stored in capacitors that could power micro- and nanoelectronic devices.
Surface functionalization
Templating Gold Surfaces with Function: A Self-Assembled Dendritic
Monolayer Methodology Based on Monodisperse Polyester ScaffoldsKim Öberg †, Jarmo Ropponen †‡, Jonathan Kelly §, Peter Löwenhielm §
, Mattias Berglin *
, and Michael Malkoch *†
, Mattias Berglin *, and Michael Malkoch *†
In this paper, a dendrimer-functionalized gold surface was used to
determine how different functionality presented by dendrimers (-OH or
-mannose) affected E. coli binding.
Drug delivery
One-Pot Synthesis of Mesoporous Silica Nanocarriers with Tunable
Particle Sizes and Pendent Carboxylic Groups for Cisplatin Delivery
Jinlou Gu *†, Jiapeng Liu †, Yongsheng Li †, Wenru Zhao †, and Jianlin Shi *†‡
http://pubs.acs.org/doi/abs/10.1021/la3036264
This paper reports might be good to keep in mind as drug delivery reference.
Jinlou Gu *†, Jiapeng Liu †, Yongsheng Li †, Wenru Zhao †, and Jianlin Shi *†‡
http://pubs.acs.org/doi/abs/10.1021/la3036264
This paper reports might be good to keep in mind as drug delivery reference.
Surface functionalization
Self-Assembled Monolayers of n-Alkanethiols Suppress Hydrogen
Evolution and Increase the Efficiency of Rechargeable Iron Battery
Electrodes
Souradip Malkhandi , Bo Yang , Aswin K. Manohar , G. K. Surya Prakash , and S. R. Narayanan http://pubs.acs.org/doi/full/10.1021/ja3095119
This work describes the importance of surface passivation of iron. Thiols do a good job, but could other ligands do better?
Souradip Malkhandi , Bo Yang , Aswin K. Manohar , G. K. Surya Prakash , and S. R. Narayanan http://pubs.acs.org/doi/full/10.1021/ja3095119
This work describes the importance of surface passivation of iron. Thiols do a good job, but could other ligands do better?
Self-assembled nanostructures
Dynamic or Nondynamic? Helical Trajectory in Hexabenzocoronene
Nanotubes Biased by a Detachable Chiral Auxiliary
Wei Zhang,†,‡ Wusong Jin,§ Takanori Fukushima,*,∥ Noriyuki Ishii,⊥ and Takuzo Aida*,†,‡
Wei Zhang,†,‡ Wusong Jin,§ Takanori Fukushima,*,∥ Noriyuki Ishii,⊥ and Takuzo Aida*,†,‡
DOI: 10.1021/ja311738m
The figure below speaks for itself. The assembly of functional hexabenzocoronenes is non-dynamic contrary to expectation.
Carbene complexes
Gold(III)-
versus Gold(I)-Induced Cyclization: Synthesis of Six-Membered Mesoionic
Carbene and Acyclic (Aryl)(Heteroaryl) Carbene Complexes (pages 758–761)Gaël Ung, Dr. Michele Soleilhavoup and Prof. Guy Bertrand
Article first published online: 21 NOV 2012 | DOI: 10.1002/anie.201207961
Interesting gold carbene structures were synthesized here.
Article first published online: 21 NOV 2012 | DOI: 10.1002/anie.201207961
Silylenes
A
Generic One-Pot Route to Acyclic Two-Coordinate Silylenes from
Silicon(IV) Precursors: Synthesis and Structural Characterization of a
Silylsilylene (pages 568–571)
Dr. Andrey V. Protchenko, Dr. Andrew D. Schwarz, Matthew P. Blake, Prof. Cameron Jones, Prof. Nikolas Kaltsoyannis, Prof. Philip Mountford and Prof. Simon Aldridge
Article first published online: 20 NOV 2012 | DOI: 10.1002/anie.201208554
This is an important discovery -- while stable cyclic silylenes are known, this report describes the first stable acyclic silylene. Molecules like this are likely going to be useful for surface functionalization of all things silicon.
Dr. Andrey V. Protchenko, Dr. Andrew D. Schwarz, Matthew P. Blake, Prof. Cameron Jones, Prof. Nikolas Kaltsoyannis, Prof. Philip Mountford and Prof. Simon Aldridge
Article first published online: 20 NOV 2012 | DOI: 10.1002/anie.201208554
This is an important discovery -- while stable cyclic silylenes are known, this report describes the first stable acyclic silylene. Molecules like this are likely going to be useful for surface functionalization of all things silicon.
Lewis Acid Catalysis
From JACS:
A Powerful Aluminium Catalyst for the Synthesis of Highly Functional Organic Carbonates
A novel aluminum complex promotes cycloaddition of CO2 and epoxides to
form carbonates with exceptional catalytic efficiency and broad
functional group tolerance. Though they focus on conditions that avoid
polymerization in this paper, this complex could end up being very
useful for epoxide/CO2 copolymerizations in the style of Geoff Coates.
Surface Functionalization
From JACS:
Gas-Phase Azide Functionalization of Carbon
Chidsey and coworkers report a really nice study showing that carbon
surfaces react with iodine azide gas to generate azide-functional
surfaces that can then be subjected to azide-alkyne click reactions.
Ni Catalysis
From JACS:
Decarbonylative C–H Coupling of Azoles and Aryl Esters: Unprecedented Nickel Catalysis and Application to the Synthesis of Muscoride A
Itami and coworkers report a surprising decarbonylative C-H
cross-coupling reaction catalyzed by a easy-to-make nickel catalyst.
They use this method for the synthesis of the natural product Muscoride
A. This work was highlighted in Angewandte here:
Bottom-up surface architecture
Surface Plasmon Mediated Chemical Solution Deposition of Gold
Nanoparticles on a Nanostructured Silver Surface at Room Temperature
Jingjing Qiu †, Yung-Chien Wu †, Yi-Chung Wang †, Mark H. Engelhard ‡, Lisa McElwee-White *†, and Wei David Wei *†
http://pubs.acs.org/doi/full/10.1021/ja309392x#
In this article, the authors describe synthesis of ligand-free gold nanoparticles (size is deposition time-tunable: 3-10 nm) on nano-structured silver surface via LSPR-promoted decomposition of Me-Au-PPh3. Gold nanoparticle growth is surface-limited, indicating that the silver surface is essential and that no gold-nanoparticle autocatalysis is taking place.
Jingjing Qiu †, Yung-Chien Wu †, Yi-Chung Wang †, Mark H. Engelhard ‡, Lisa McElwee-White *†, and Wei David Wei *†
http://pubs.acs.org/doi/full/10.1021/ja309392x#
In this article, the authors describe synthesis of ligand-free gold nanoparticles (size is deposition time-tunable: 3-10 nm) on nano-structured silver surface via LSPR-promoted decomposition of Me-Au-PPh3. Gold nanoparticle growth is surface-limited, indicating that the silver surface is essential and that no gold-nanoparticle autocatalysis is taking place.
Spherical Assemblies from π-Conjugated Alternating Copolymers: Toward Optoelectronic Colloidal Crystals
JACS
Taeko Adachi †, Liang Tong †, Junpei Kuwabara †‡, Takaki Kanbara †‡, Akinori Saeki §, Shu Seki §, and Yohei Yamamoto *†‡
http://pubs.acs.org/doi/abs/10.1021/ja3106626
The authors demonstrated that polymers such as polyfluorene and polythiophene having a single monomer component hardly formed defined and discrete objects but only gave ill-defined aggregates. In contrast, alternating copolymers typically having both fluorene and thiophene components in their repeating unit self-assembled into well-shaped spheres with diameters ranging from several hundreds of nanometers to several micrometers. Such clear differences in terms of the assembling geometries derive from the rigidity and crystallinity of the polymers, where the copolymers possess large steric hindrance on their backbone that reduces planarity of the polymers and inhibits anisotropic crystal growth, leading to the formation of structurally isotropic spheres. Changing the assembling parameters can systematically control diameter and deviation of the spheres. Furthermore, photocarrier lifetimes of the spheres were markedly enhanced by more than 3 orders of magnitude.
Taeko Adachi †, Liang Tong †, Junpei Kuwabara †‡, Takaki Kanbara †‡, Akinori Saeki §, Shu Seki §, and Yohei Yamamoto *†‡
http://pubs.acs.org/doi/abs/10.1021/ja3106626
The authors demonstrated that polymers such as polyfluorene and polythiophene having a single monomer component hardly formed defined and discrete objects but only gave ill-defined aggregates. In contrast, alternating copolymers typically having both fluorene and thiophene components in their repeating unit self-assembled into well-shaped spheres with diameters ranging from several hundreds of nanometers to several micrometers. Such clear differences in terms of the assembling geometries derive from the rigidity and crystallinity of the polymers, where the copolymers possess large steric hindrance on their backbone that reduces planarity of the polymers and inhibits anisotropic crystal growth, leading to the formation of structurally isotropic spheres. Changing the assembling parameters can systematically control diameter and deviation of the spheres. Furthermore, photocarrier lifetimes of the spheres were markedly enhanced by more than 3 orders of magnitude.
Visible-Light-Induced Reversible Complexation Mediated Living Radical Polymerization of Methacrylates with Organic Catalysts
From Macromolecules:
Visible-Light-Induced Reversible Complexation Mediated Living Radical Polymerization of Methacrylates with Organic Catalysts
Drug Delivery Systems
From J. Am. Chem. Soc.:
Acid-Active Cell-Penetrating Peptides for in Vivo Tumor-Targeted Drug Delivery
Cell-Material Interactions
From Nano Lett.:
Label-Free Segmentation of Co-cultured Cells on a Nanotopographical Gradient
The behavior of different cell types co-cultured on nanopillar arrays is
described. The authors find that co-cultured cells can be
differentiated based on the different pillar sizes. For example, they
suggest that 75 nm tall pillars will maximize the ratio of endothelial
cells to fibroblast cells in a co-culture.
Photochemistry and Liquid Crystals
From J. Am. Chem. Soc.:
Photoalignment Layers for Liquid Crystals from the Di-π-methane Rearrangement
The Swager group has used a clever di-pi-methane rearrangement along a polymer backbone to control liquid crystal alignment.
Ni-Catalyzed Cross Coupling
From J. Am. Chem. Soc.:
Nickel-Catalyzed Carbon–Carbon Bond-Forming Reactions of Unactivated Tertiary Alkyl Halides: Suzuki Arylations
The Fu group has reported a Ni-catalyzed cross-coupling of tertiary alkyl halides and 9-BBN functionalized aryl species. They essentially used conditions they had developed previously for primary and secondary halides, but employed a smaller ligand.
A Supramolecular Cross-Linked Conjugated Polymer Network for Multiple Fluorescent Sensing
From J. Am. Chem. Soc.:
A Supramolecular Cross-Linked Conjugated Polymer Network for Multiple Fluorescent Sensing
A gel material was developed that displays turn on fluorescence in response to various stimuli.
Selective Fluorescent Detection of RNA in Living Cells by Using Imidazolium-Based Cyclophane
From J. Am. Chem. Soc.:
Selective Fluorescent Detection of RNA in Living Cells by Using Imidazolium-Based Cyclophane
An imidazolium-based cyclophane was found to display turn on
fluorescence in the presence of RNA molecules. Ionic interactions
between the positively charged imidazolium groups and the anionic RNA
backbond, along with pi-pi interactions, are invoked as reasons why this
molecule selectively binds RNA. In any case, the synthesis could be of
interest to those of you working with NHCs.
H-Gemcitabine: A New Gemcitabine Prodrug for Treating Cancer
From Bioconj. Chem.:
H-Gemcitabine: A New Gemcitabine Prodrug for Treating Cancer
Synthesis and in vivo evaluation of a gemcitabine prodrug is
described. The synthesis deals with various thiol and thiol
derivatives. Could be useful for those of you making thiols.
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