Inducing Supramolecular Chirality from Afar with Allostery

Researchers from India have achieved the control of supramolecular helicity in a bistable artificial self-assembled system through the addition of either a chiral or achiral component. Anthea Blackburn writes more…

Aristotle’s saying “the whole is more than the sum of its parts” is often well-exemplified in supramolecular chemistry – the result of non-covalent interactions present in a complex assembly of simple building blocks often generate novel properties that would not otherwise be present in a simple mixture of the components. The design of systems that exhibit these emergent phenomena is therefore an aim of many supramolecular chemists, including researchers from India who have achieved the control of supramolecular helicity in a bistable artificial self-assembled system through the addition of either a chiral or achiral component. This example of allosteric regulation in a synthetic system is an interesting analogue of that which occurs in biological systems, and offers an attractive approach to inducing not only conformational change in a pre-formed assembly, but also new chemical properties that could not otherwise be observed.

In biological systems, allosteric regulation, the binding of a secondary molecule to an enzyme, is employed to modulate the conformation of the active site and thus the effectiveness of an enzyme. This feature allows for communication between remote sites in a cell by providing a control loop in enzymes. It is therefore of interest to scientists to apply this allosteric regulation synthetically as a way of introducing a dynamic component to a molecular system.

Allosteric Regulation

Mohit Kumar and Subi George at the Jawaharlal Nehru Centre for Advanced Scientific Research[EB1] (JNCASR) in India have begun to experiment with the use of allostery in synthetic system[EB2] in order to induce [EB3] helicity in a polymeric supramolecular assembly comprised of a perylene bisimide functionalised at either end by a Zinc(II) motif that is known to bind phosphate ligands. In the “off” state this assembly exists as linear stacks of the molecule, such that overall the assembly is achiral. Upon the binding of 0.5 equivalents of chiral adenine trisphospate (ATP), a supramolecular reorganization is observed to form the helically dormant H1 state, which, upon the addition of further equivalents of ATP, results in a second conformational change to the helical H2, whereby the linear stacks are now twisted in nature and exhibit chirality. This example of chiral induction, in which a single molecule can turn “on” its chirality, exemplifies homotropic allosteric regulation. Furthermore, upon the addition of a second achiral pyrophosphate ligand (PPi) to H1, a different helical H2 state is induced in the assembly. The introduction of two chemically different molecules that interact with the assembly in different ways is an example of heterotropic allosteric regulation.

This use of supramolecular chemistry to post-synthetically elicit a change in a molecular assembly is an exciting way of mimicking the allostery observed in biology. Even more remarkable, is the ability of one system to respond in two different ways.

Read this HOT ChemSci article in full for free*!

Homotropic and heterotropic allosteric regulation of supramolecular chirality
Mohit Kumar and Subi B. George
DOI: 10.1039/C4SC00813H

About the Writer

Anthea Blackburn is a guest web writer for Chemical Science. Anthea is a graduate student hailing from New Zealand, studying at Northwestern University in the US under the tutelage of Prof. Fraser Stoddart (a Scot), where she is exploiting supramolecular chemistry to develop multidimensional systems and study the emergent properties that arise in these superstructures. When time and money allow, she is ambitiously attempting to visit all 50 US states before graduation.

*Access is free untill 06.06.14 through a registered RSC account – click here to register

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Hot Chemical Science articles for May

All of the referee-recommended articles below are free to access until 2nd June 2014

Functionalised staple linkages for modulating the cellular activity of stapled peptides
Yu Heng Lau, Peterson de Andrade, Soo-Tng Quah, Maxim Rossmann, Luca Laraia, Niklas Sköld, Tze Jing Sum, Pamela J. E. Rowling, Thomas L. Joseph, Chandra Verma, Marko Hyvönen, Laura S. Itzhaki, Ashok R. Venkitaraman, Christopher J. Brown, David P. Lane and David R. Spring  
Chem. Sci., 2014, 5, 1804-1809
DOI: 10.1039/C4SC00045E, Edge Article


Single molecule analysis of light-regulated RNA:spiropyran interactions
Xing Zhang, Junji Zhang, Yi-Lun Ying, He Tian and Yi-Tao Long  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC00134F, Edge Article


Imine-Based Chiroptical Sensing for Analysis of Chiral Amines: From Method Design to Synthetic Application
Leo A Joyce, Edward Sherer and Christopher J Welch  
Chem. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4SC01006J, Edge Article

 


Decoding the infrared signatures of pyramidal carbons in graphenic molecular nanostructures of interstellar origin
Héctor Álvaro Galué  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC00890A, Edge Article

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Shining a light on polymer welding

Charlie Quigg writes about a hot Chemical Science article for Chemistry World

Chinese chemists have created an epoxy that can be rapidly hardened and reshaped by shining a light on it. Unlike traditional epoxies which are cured using heat, this approach uses carbon nanotubes to translate light energy into localised heat to set the epoxy. Shining additional light on the set polymer initiates self-healing and reshaping.


Read the full article in Chemistry World»

Read the original journal article in Chemical Science - it’s free to access until 17th June:
Carbon nanotube-Vitrimer composite for facile and efficient photo-welding of epoxy
Yang Yang, Zhiqiang Pei, Xiqi Zhang, lei tao, yen wei and Yan Ji  
Chem. Sci., 2014, Accepted Manuscript, DOI: 10.1039/C4SC00543K, Edge Article

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Unzipping DNA cubes, a triggered response

Kate Montgomery is currently doing a PhD in drug delivery using polymer based nanoparticles, her project is a collaboration between Imperial College London and CSIRO in Melbourne. When she is not making extremely sticky polymers in the lab, Kate enjoys reading, running (very slowly) and deep sea diving.’

At the mention of DNA most people think of the storage of genetic information, but due to its biocompatibility and the ease with which it can be manipulated, it is becoming increasingly common for DNA to be used as a building material in nanotechnology.

DNA cages have attracted interest in the world of drug delivery as they can encapsulate small molecule drugs and are easily taken up by cells. The precision with which the size and shape of the cages can be controlled is another attractive aspect. Past studies have established that DNA cages can target cells, deliver encapsulated cargo and have a cytotoxic effect in cancer cells. However, specific control of the cellular delivery profile of DNA cages has not yet been achieved.

Sleinman and co-workers, from McGill University based in Montréal, Canada, have created dynamic DNA cubes which ‘unzip’ in a specific cellular environment. The cages are assembled from six DNA strands which make up the six sides of the cube and only disassemble in the presence of a trigger found in prostate cancer cells. The authors tested the uptake and disassembly, or ‘unzipping’, of their DNA cubes in vitro using three different mammalian cell lines.

Hydrophobic and hydrophilic dendritic chains were added to the cube after initial testing. It was determined that these chains coat the exterior of the cube and have a significant effect on the uptake of the structure. While the addition of hydrophobic chains to the cube increase uptake, addition of hydrophilic chains increase the stability of the cube in cellular environments.


One of the exciting aspects about this work is the scope for adaptation; the cubes could potentially be designed to respond to any nucleic acid sequence found specifically in diseased cells. Future work in the group will also look at encapsulating and delivering cargo, such as oligonucleotide drugs, using this new delivery system.


To download the full article for free* click the link below:

Sequence-responsive unzipping DNA cubes with tunable cellular uptake profiles

Katherine E. Bujold, Johans Fakhoury, Thomas G. W. Edwardson, Karina M. M. Carneiro, Joel Neves Briard, Antoine G. Godin, Lilian Amrein, Graham D. Hamblin, Lawrence C. Panasci, Paul W. Wiseman and Hanadi F. Sleiman
DOI: 10.1039/C4SC00646A

*Access is free until 02/06/2014 through a registered RSC account – click here to register

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Challenges in Inorganic and Materials Chemistry (ISACS13) – early bird registration approaching

 
Challenges in Inorganic and Materials Chemistry - ISACS13
   
Don’t miss your chance to attend Challenges in Inorganic and Materials Chemistry (ISACS13)

Early bird registration and bursary deadline – 12 May
 Register now

Now is also a perfect time to register to join Guy Bertrand, Susumu Kitagawa and Matthew Rosseinsky at Challenges in Inorganic and Materials Chemistry (ISACS13) as early bird rates and bursaries are currently available.

Remember, these great savings are only available until the 12 May 2014 so guarantee your place now.

We look forward to welcoming you to Dublin this July.             
                                      

Professor Thorri Gunnlaugsson Dr Robert D. Eagling
Conference Chair Editor, Chemical Science
 

P.S. Join us for the 5th Joint CSJ RSC Symposium on Supramolecular Chemistry which is being held on 1st July in Dublin, just before the start of ISACS13. It’s free to attend and registration is open now.

 

 

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Decoding interstellar carbon

Rachel Wood writes about a hot Chemical Science article for Chemistry World

For over 20 years the infrared spectra of many astronomical objects have been interpreted as flat two-dimensional polycyclic aromatic hydrocarbons (PAHs) that are also thought to be the source of organic matter on our own planet. More recently the detection of molecules such as fullerenes – molecules composed entirely of carbon, including the spherical C60 – has revealed a more complicated picture of carbon in space. The links between these different molecules have been rather unclear but new research from Héctor Alvaro Galué at VU University of Amsterdam, in the Netherlands, has taken a fresh approach to this long-standing puzzle.

Energetic particles in interstellar space induce strain and re-hybridisation within flat carbon structures. Background image: © NASA, ESA, M Robberto (Space Telescope Science Institute/ESA) and the Hubble Space Telescope Orion Treasury Project Team


Read the full article in Chemistry World»

Read the original journal article in Chemical Science - it’s free to download until 6th June:
Decoding the infrared signatures of pyramidal carbons in graphenic molecular nanostructures of interstellar origin
Hector Alvaro Galue  
Chem. Sci., 2014, Accepted Manuscript, DOI: 10.1039/C4SC00890A, Edge Article

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Challenges in Inorganic and Materials Chemistry (ISACS13) – poster deadline 21 April

 
Challenges in Inorganic and Materials Chemistry - ISACS13
Poster abstract deadline – 21 April
 Submit
Don’t miss your chance to submit an abstract for Challenges in Inorganic and Materials Chemistry (ISACS13) – the poster deadline is just one week away.

This is an excellent opportunity to showcase your work and there will also be a poster prize awarded by Chemistry World for the best contribution, so be sure to submit your latest research before Monday 21 April 2014.

Early bird registration and bursary deadline – 12 May
 Register now

Now is also a perfect time to register to join Guy Bertrand, Susumu Kitagawa and Matthew Rosseinsky at Challenges in Inorganic and Materials Chemistry (ISACS13) as early bird rates and bursaries are currently available.

Remember, these great savings are only available until the 12 May 2014 so guarantee your place now.

We look forward to welcoming you to Dublin this July.             
                                      

Professor Thorri Gunnlaugsson Dr Robert D. Eagling
Conference Chair Editor, Chemical Science
P.S. Join us for the 5th Joint CSJ RSC Symposium on Supramolecular Chemistry which is being held on 1st July in Dublin, just before the start of ISACS13. It’s free to attend and registration is open now.

 

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

DNA cube programmed for an exclusive reveal

Jennifer Newton writes about a hot Chemical Science article for Chemistry World

Scientists in Canada have made DNA cubes that are programmed to unzip and reveal molecules locked inside them in response to a carefully chosen trigger. Hanadi Sleiman and colleagues at McGill University and the Jewish General Hospital in Montreal, designed the cubes to release the drug cargo they might be carrying only in diseased cells and not normal cells.

The mRNA trigger binds tothe overhangs and opens the cube by strand displacement and strategically placed nicks on the structure


Read the full article in Chemistry World»

Read the original journal article in Chemical Science – it’s free to download until 7th May:
Sequence-responsive unzipping DNA cubes with tunable cellular uptake profiles
Katherine E. Bujold, Johans Fakhoury, Thomas G. W. Edwardson, Karina M. M. Carneiro, Joel Neves Briard, Antoine G. Godin, Lilian Amrein, Graham D. Hamblin, Lawrence C. Panasci, Paul W. Wiseman and Hanadi F. Sleiman  
Chem. Sci., 2014, Advance Article, DOI: 10.1039/C4SC00646A, Edge Article

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Hot Chemical Science articles for April

All of the articles below are free to access until 14th May

Boron–boron J coupling constants are unique probes of electronic structure: a solid-state NMR and molecular orbital study
Frédéric A. Perras and David L. Bryce  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC00603H, Edge Article


Disubstituted sialic acid ligands targeting siglecs CD33 and CD22 associated with myeloid leukaemias and B cell lymphomas
Cory D. Rillahan, Matthew S. Macauley, Erik Schwartz, Yuan He, Ryan McBride, Britni M. Arlian, Janani Rangarajan, Valery V. Fokin and James C. Paulson  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC00451E, Edge Article


Solvatochromic AIE luminogens as supersensitive water detectors in organic solvents and highly efficient cyanide chemosensors in water
Yuping Zhang, Dongdong Li, Yi Li and Jihong Yu  
Chem. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4SC00721B, Edge Article

 


Catalytic enantioselective synthesis of 2-aryl-chromenes
Bi-Shun Zeng, Xinyi Yu, Paul W. Siu and Karl A. Scheidt  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC00423J, Edge Article

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Two stories from ISACS 12: solar-fuel devices and catalyst identification

 

The April issue of our sister journal Energy & Environmental Science opens with an editorial on the ISACS 12 conference held in Cambridge last September.  Nathan Lewis, Chair of the EES editorial board, and co-authors report on highlights of the symposium and discuss two of the main topics covered at the meeting: solar-fuel generators and identifying catalysts.

Read the full EES editorial here:
Two stories from the ISACS 12 conference: solar-fuel devices and catalyst identification
Energy Environ. Sci.,
2014, 7, 1207, DOI: 10.1039/c3ee90043f

ISACS 12 focused on “Challenges in Renewable Energy” and built on the success of its precursor ISACS 4 in 2011. The full programme is available to view online.

The ISACS (International Symposia on Advancing the Chemical Sciences) series is organised in partnership with Chemical Science and brings together leading scientists from across the world. You can find out more about upcoming conferences on the website, as well as view the speakers and programmes for previous events.

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)