Comprehensive solvent acidity scale could help make acid-catalysed reactions more reliable and reproducible.
A collaboration between scientists in Estonia and Germany has resulted in a comprehensive solvent acidity scale spanning 28 orders of magnitude, twice as much as the classical pH scale.
Click here to read the full story on Chemistry World written by Lynn Murphy.
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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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.
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.
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*:
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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
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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.
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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
