Mimicking Biological Systems with Supramolecular Assemblies: A Step Closer

Biological systems, such as circadian rhythms and ion pumps, are generally able to respond autonomously to chemical stimuli. Such ability is at the root of certain amphiphilic molecules (i.e. molecules containing both hydrophilic and hydrophobic parts) that can change their configurations temporally at the presence of the stimulants. In recent decades, building artificial biological systems with active, adaptive and autonomous behaviours similar to natural biological systems has become a hot topic.

Supramolecular assemblies are among the most extensively explored building materials. A supramolecular assembly is a system consisting of complex molecules held together by non-covalent bonds, such as DNA. One of the major technological hurdles for developing artificial biological systems using supramolecular assemblies is to acquire assemblies with an amphiphilic nature and the ability to undergo a transient change of configuration when stimulated. The change should also be highly reversible and durable. Currently, extensive research efforts are committed to finding candidates that address the aforementioned challenge.

A research group from Jawaharlal Nehru Centre for Advanced Scientific Research in India recently made a step forward and published their work in Chemical Science. They developed an amphiphilic supramolecular motif, coined PN-VN foldamer, which could switch its conformation upon contact with oxidizing and reducing agents. As shown in Figure 1a, the skeleton of the supramolecular motif is composed of three sections. The green head is an electron donor pyranine (PN), the red tail is an electron acceptor called viologen (VN) rendering the hydrophobic nature, and the blue body is a flexible hydrophilic hexaethylene glycol that connects the electron donor and acceptor.

Figure 1. (a) The structure of the amphiphilic PN-VN foldamer. (b) Unfolded and folded states of the PN-VN foldamer correspond to sheet and vesicle morphologies, respectively.

The researchers demonstrated the assembly pattern of PN-VN foldamers (Figure 1b) by using two chemical fuels, sodium dithionite and glucose, as the stimulants. The transformation process is depicted in Figure 2a. When undisturbed, the negatively charged PN (PN3-) and the positively charged VN (VN2+) can attract each other via a charge transfer interaction, folding the entire molecular chains to vesicles. When placed in a solution containing sodium dithionite and glucose, the VN2+ terminal can be instantaneously reduced by sodium dithionite to its radical cation form (VN•+). The reduction weakens the charge transfer interaction, and subsequently unfolds PN-VN vesicles to sheets. Meanwhile, catalyzed by glucose oxidase (an enzyme), the excess glucose in the same solution can oxidize VN•+ back to its original state, resulting in the folded state that recovers vesicles. The transition is directly confirmed by transmission electron microscopy as shown in Figure 2b. Since the reduction process proceeds much faster than the oxidation process, it is observed that PN-VN vesicles first extend to sheets momentarily and gradually but automatically fold back to vesicles within minutes. The rate of the transition can be well tuned by varying the concentration of glucose oxidase.

Figure 2. (a) Schematic of the transient configuration change between vesicles and sheets. SDT: sodium dithionite; GOx: glucose oxidase. (b) Transmission electron microscopic images of the vesicles (left) and the sheets (right). Inset in the left panel shows the distribution of the wall thickness of the vesicles. Inset in the right panel is a confocal fluorescence microscopy image of a selected sheet (scale bar: 2 μm).

To find out more please read:

Temporal Switching of an Amphiphilic Self-assembly By a Chemical Fuel-driven Conformational Response

Krishnendu Jalani, Shikha Dhiman, Ankit Jain, and Subi J. George

DOI: 10.1039/c7sc01730h

About the author:

Tianyu Liu is a Ph.D. in chemistry graduated from University of California-Santa Cruz. He is passionate about scientific communication to introduce cutting-edge researches to both the general public and the scientists with diverse research expertise. He is a web writer for the Chem. Commun. and Chem. Sci. blog websites. More information about him can be found at http://liutianyuresearch.weebly.com/.

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HOT Chemical Science articles for July

All of the referee-recommended articles below are free to access.

Solid–State Molecular Organometallic Chemistry. Single–Crystal to Single–Crystal Reactivity and Catalysis with Light Hydrocarbon Substrates
F. Mark Chadwick, Alasdair I. McKay, Antonio J. Martinez-Martinez, Nicholas H. Rees, Tobias Krämer, Stuart A. Macgregor and Andrew S. Weller
Chem. Sci., 2017, Advance Article
DOI: 10.1039/C7SC01491K, Edge Article

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Efficient stabilisation of a dihydrogenphosphate tetramer and a dihydrogenpyrophosphate dimer by a cyclic pseudopeptide containing 1,4-disubstituted 1,2,3-triazole moieties
Disha Mungalpara, Arto Valkonen, Kari Rissanen and Stefan Kubik
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DOI: 10.1039/C7SC02700A, Edge Article

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Dual targeting of the cancer antioxidant network with 1,4-naphthoquinone fused Gold(I) N-heterocyclic carbene complexes
R. McCall, M. Miles, P. Lascuna, B. Burney, Z. Patel, K. J. Sidoran, V. Sittaramane, J. Kocerha, D. A. Grossie, J. L. Sessler, K. Arumugam and J. F. Arambula
Chem. Sci., 2017, Advance Article
DOI: 10.1039/C7SC02153D, Edge Article

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Remote C–H insertion of vinyl cations leading to cyclopentenones
Sarah E. Cleary, Magenta J. Hensinger and Matthias Brewer
Chem. Sci., 2017, Advance Article
DOI: 10.1039/C7SC02768K, Edge Article

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Plotting a course to new antibiotics

Researchers in Switzerland and Italy have devised a way to chart protein-based antibiotics according to their chemistry. This map of the chemical space has allowed them to search for new compounds more intelligently and has already led to them finding a new antibiotic for a highly resistant hospital bug.

In the biochemical arms race between bacteria and medicine, novelty is key. New types of molecules, acting in new ways, can kill microbes that are resistant to our existing arsenal. Unfortunately, the world of potential molecules is huge and mostly uncharted. New antibiotics act as landmarks, signposting where other useful compounds might lie. Researchers then start exploring nearby – although in an abstract chemical space, ‘nearby’ can be a tricky concept.

Source: © Royal Society of Chemistry
Chemical space guided the discovery of antimicrobial bridged bicyclic peptides against Pseudomonas aeruginosa and its biofilms

Read the full story by Alexander Whiteside on Chemistry World.

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Congratulations to Pablo Martinez-Bulit!

Chemical Science poster prize winner at ISMSC/ISACS 2017

Pablo Martinez-Bulit next to his poster presented at ISMSC/ISACS

Congratulations to the Poster Prize winner at this year’s ISMSC/ISACS meeting.

The winner is Pablo Martinez-Bulit from the University of Windsor, Canada who is currently working as a graduate student in the group of Professor Stephen Loeb. His Ph.D. research focuses on the synthesis of [n]rotaxanes suitable for their incorporation into solid-state materials so we can use the dynamics inherent to these systems. He is especially interested in the rotation, translation, and conformational changes of the macrocyclic ring. Finally, the use of porphyrins provides an excellent scaffold to obtain robust materials.

The International Symposium on Macrocylic and Supramolecular Chemistry (ISMSC) which was run in 2017 in conjunction with ISACS: Challenges in Organic Materials & Supramolecular Chemistry took place in Cambridge, UK. The conference themes spread the breadth of macrocyclic and supramolecular chemistry from inorganic to organic chemistry and chemical biology, and the symposium provided an excellent opportunity for graduate students and postdocs to present their work in a multidisciplinary environment.

We wish Pablo all the best for his ongoing research and look forward to reading about his first results very soon.

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Christopher C. Cummins awarded the 2017 Linus Pauling award

We would like to congratulate Chemical Science Associate Editor Christopher C. Cummins (MIT), who was recently awarded the 2017 Linus Pauling award. Christopher will be presented with the award later on in the year at the 2017 Linus Pauling Medal Award Symposium at Portland State University. The Pauling Medal is sponsored jointly by the Portland, Puget Sound, and Oregon sections of the American Chemical Society. Congratulations from all of us at Chemical Science and the Royal Society of Chemistry!

Nominees for the award were chosen based on their history of making outstanding contributions to chemistry that are worthy of receiving worldwide recognition. Those who have previously received a Nobel Prize are not eligible for this award.

Christopher has been an Associate Editor for Chemical Science since the launch of the journal in 2010. Christopher specializes in the areas of inorganic and organometallic chemistry and welcomes submissions in this area. Together with our dynamic international team of Associate Editors, he has been actively driving the journal’s scientific development by making direct decisions on its content – submit your best work to any of their Editorial Offices today!

Read Christopher Cummins’ latest articles in Chemical Science*:

On the incompatibility of lithium–O2 battery technology with CO2
Shiyu Zhang, Matthew J. Nava, Gary K. Chow, Nazario Lopez, Gang Wu, David R. Britt, Daniel G. Nocera and Christopher C. Cummins
Chem. Sci., 2017, Advance Article
DOI: 10.1039/C7SC01230F, Edge Article
Open Access

A family of cis-macrocyclic diphosphines: modular, stereoselective synthesis and application in catalytic CO2/ethylene coupling
Ioana Knopf, Daniel Tofan, Dirk Beetstra, Abdulaziz Al-Nezari, Khalid Al-Bahily and Christopher C. Cummins
Chem. Sci., 2017,8, 1463-1468
DOI: 10.1039/C6SC03614G, Edge Article
Open Access

Multi-electron reactivity of a cofacial di-tin(II) cryptand: partial reduction of sulfur and selenium and reversible generation of S3˙−
Julia M. Stauber, Peter Müller, Yizhe Dai, Gang Wu, Daniel G. Nocera and Christopher C. Cummins
Chem. Sci., 2016,7, 6928-6933
DOI: 10.1039/C6SC01754A, Edge Article
Open Access

Negative ion photoelectron spectroscopy of P2N3−: electron affinity and electronic structures of P2N3˙
Gao-Lei Hou, Bo Chen, Wesley J. Transue, David A. Hrovat, Christopher C. Cummins, Weston Thatcher Borden and Xue-Bin Wang
Chem. Sci., 2016,7, 4667-4675
DOI: 10.1039/C5SC04667J, Edge Article
Open Access

*Access is free through a registered RSC account

 

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HOT Chemical Science articles for June

The referee-recommended articles below are free to access until 5th August 2017.

Formation and decay of negative ion states up to 11 eV above the ionization energy of the nanofabrication precursor HFeCo3(CO)12
Ragesh Kumar T P, Ragnar Bjornsson, Sven Barth and Oddur Ingólfsson
Chem. Sci., 2017, Advance Article
DOI: 10.1039/C7SC01927K, Edge Article

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Structural-functional analysis of engineered protein-nanoparticle assemblies using graphene microelectrodes
Jinglei Ping, Katherine W. Pulsipher, Ramya Vishnubhotla, Jose A. Villegas, Tacey L. Hicks, Stephanie Honig, Jeffery G. Saven, Ivan J. Dmochowski and A. T. Charlie Johnson
Chem. Sci., 2017, Advance Article
DOI: 10.1039/C7SC01565H, Edge Article

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Polar solvents promote halogen bonds over hydrogen ones

Solvent effects control competition between hydrogen bonding and halogen bonding in supramolecular systems, new research shows. The upshot of the finding is a potential new tool to direct supramolecular self-assembly.

During self-assembly, each molecule breaks its bonding interactions with neighbouring solvent molecules, then forms new interactions. To investigate competition between hydrogen bonding and halogen bonding when co-crystals form, researchers from an ongoing collaboration between the UK Universities of Sheffield, York and Cambridge chose seven solvents of different polarities to study three aromatic molecules known to self-assemble. The molecules’ functional groups included pairs of hydrogen bond and halogen bond donors that compete for a common acceptor group.

Solvent plays a critical role in directing self-assembly

Read the full story by Fiona Tscherny on Chemistry World.

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Light-driven catalytic process offers greener route to organic alcohols

Researchers in Spain have developed a light-driven catalytic process that offers a greener way to produce organic alcohols – important compounds used to manufacture pharmaceuticals and pesticides.

Researchers have developed a catalytic system to reduce aromatic ketones and both aliphatic and aromatic aldehydes that uses earth-abundant metals and light.

Read the full story by Jamie Durrani on Chemistry World.

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15th Host Guest Supramolecular Chemistry Annual Symposium RSC award winners

The Chemical Science was awarded at the 15th Host Guest Supramolecular Chemistry Annual Symposium in Kusatsu, Japan, 3-4 June 2017, along with the ChemComm poster prize, the Organic & Biomolecular Chemistry poster prize and 7 other poster prizes.

The Host Guest Supramolecular Chemistry Annual Symposium (website in Japanese) is an annual event that is organized by the Association of Research for Host-Guest and Supramolecular Chemistry. This year, the 15th occurrence of this symposium took place at the Ritsumeikan University on 3-4 June 2017. The event was attended by 230 people and counted 39 talks and 128 poster presentations.

The Chemical Science, ChemComm and Organic & Biomolecular Chemistry poster prizes were delivered to the 3 most outstanding poster presentations, along with 7 other poster prizes.

 

Nobuhiko Nishitani from Kyoto University was awarded the Chemical Science award for their poster titled: STM Observation of Cooperative Self-Assembly at the Liquid/Graphite Interface: Influence of Intercolumnar Interactions on Domain Size and Shape

Tsuyoshi Mashima from Osaka University was awarded the ChemComm award for their poster titled: Construction of Zn-substituted Hexameric Hemoprotein with Multiple Photosensitizers and Evaluation of its Light Harvesting Function

Tomokuni Kai from Tokyo Institute of Technology was awarded the Organic & Biomolecular Chemistry award for their poster titled: Polyaromatic Micelles: Emission Enhancement of Eu(III)-complexes in Water upon Encapsulation

From right to left: Prof. Tatsuya Nabeshima (University of Tsukuba), Nobuhiko Nishitani, Tsuyoshi Mashima, Tomokuni Kai, and the poster prize winners, along with Prof. Hiromitsu Maeda (Ritsumeikan University, left) (Click to enlarge)


Dr Hiromitsu Urakami, from the Royal Society Chemistry, gave a lauded presentation on Publishing on 3rd June.

Dr Hiromitsu Urakami

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First +5 praseodymium compound with PrN triple bond made

The first pentavalent praseodymium nitride–oxide that features a rare Pr≡N triple bond is the second ever lanthanide(V) complex to be made.

Lanthanide chemistry is dominated by the +3 oxidation state. There are some common +4 lanthanide complexes such as cerium oxide (CeO2), but +5 compounds have proven elusive. Praseodymium has long been considered as the most promising route to lanthanide(V) chemistry as it has five valence electrons, but the first pentavalent praseodymium complex, the oxide PrO2+, was only synthesised last year.

Source: © Royal Society of Chemistry
Calculations led to these representations of the molecular orbitals of the praseodymium(V) compound, NPrO

Read the full story by Aurora Walshe on Chemistry World.

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