Chemical Science Blog

The movement of molecules in and out of cells is fundamental to the chemistry of life. The process is facilitated by other molecules, specifically designed (or perhaps evolved!) to assist in transportation across the cell wall. It is a complicated process and remains poorly understood yet it is known that disruption of the process is linked to many debilitating diseases, such as cystic fibrosis. As a result, there is significant interest in increasing our understanding of the chemistry involved. Only by doing this will it be possible to create treatments which could, for example, use synthetic carriers to improve transportation in cases where it is restricted.

(a) Varying the position of the anion-binding group (b) Transport activities in synthetic vesicles are measured via the quenching of lucigenin fluorescence by incoming chloride.

Insight into transport of anions across cell membranes is reported in back-to-back Edge Articles in Chemical Science by Philip Gale and his network of collaborators at the University of Southampton, the University of Sydney, the University of Ljubljana and the NMR centre at the National Institute of Chemistry in Slovenia, and the University of Bristol.  In the first paper, Gale’s group and the team of Anthony Davis at Bristol address a new principle, which they refer to as ‘lipophilic balance’.  Anion carriers must have an affinity for the ions they need to transport but, as they discover, the location of that anion receptor within the molecule is also critical.  A central or balanced location with the transport carrier results in a much faster transportation of the anion.

In the second paper, Gale and co-workers team up with Katrina Jolliffe (Sydney), Janez Plavec (Slovenia), and their respective groups to examine transport of a poorly studied anion – sulphate. To do this, they explain how they developed a new method based upon sulphur NMR spectroscopy. This has allowed them to monitor sulphate transportation through differences they observe, both inside and outside of the vesicle. Furthermore, they establish that the movement is assisted by small cyclic molecules that are able to wrap around the sulphate.

The work is also reported through an exciting new website called Kudos – a prototype site which works with selected authors to test the effect on download and social media activity of collating and creating multimedia and additional metadata around articles.  The pilot project, supported by the Royal Society of Chemistry and other publishers, is designed to help scientists enhance the impact of their published work, increasing visibility and discoverability. This is achieved by providing a framework to include supplementary information which is often not possible to include in a journal submission, such as a discussion of the work in lay terms, the wider impact of the work and supplementary information such as videos. The greater accessibility of the work therefore allows the researchers to engage a wider audience and maximise their impact.

Access these two Chemical Science Edge Articles on Kudos today – FREE to read!

Lipophilic balance – a new design principle for transmembrane anion carriers
Hennie Valkenier, Cally J. E. Haynes, Julie Herniman, Philip A. Gale and Anthony P. Davis
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C3SC52962B

Synthetic transporters for sulfate: a new method for the direct detection of lipid bilayer sulfate transport
Nathalie Busschaert, Louise E. Karagiannidis, Marco Wenzel, Cally J. E. Haynes, Neil J. Wells, Philip G. Young, Damjan Makuc, Janez Plavec, Katrina A. Jolliffe and  Philip A. Gale
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C3SC52006D

Ruaraidh McIntosh is a guest web-writer for Chemical Science.  His research interests include supramolecular chemistry and catalysis.  When not working as a Research Fellow at Heriot-Watt University, Ruaraidh can usually be found in the kitchen where he has found a secondary application for his redoubtable skills in burning and profanity.

Heterogeneous catalysis is widely used industrially to assist in the production of many man made materials.  The world economy is reliant upon production of these materials, therefore catalysts which are reliable and cheap are hugely important.  Heterogeneous catalysts generally fulfill these criteria, hence their wide application, but the understanding of how they function is often poorly defined.

Academic investigations of single site homogeneous catalysts are generally simpler to study, which makes defining what reactions occurs at each stage and the factors which influence them clearer to interpret.  Heterogeneous catalysts are more complex to study.  The interaction between the different phases must be considered along with the nature of the catalyst itself.  The catalysts are generally solid materials whose bulk composition may not provide an accurate picture of the surface where the reactions will ultimately be occurring and the activity may be quite different.  Analysis of the subtleties of what is happening at the surface is incredibly difficult with many of the commonly used techniques not capable of providing the detail required.  But in order to fully understand a heterogeneous catalyst it is essential to have an understanding of the how the separate phases interact.

Tristan Youngs of the ISIS Facility, Christopher Hardacre of Queen’s University Belfast, and their co-workers have reported a new method to study a heterogenous process in real time.  Neutron scattering experiments (which were only made possible by the state of the art facilities at ISIS) provide the ability to simultaneously examine the rate at which reactions occur and also the speed with which the different phases in a heterogeneous system can interact.  A commonly held principle of heterogeneous catalysis is that by constructing pores and channels in the catalyst we can increase the effective surface area of the catalyst, increasing the number of sites where reactions can occur, thereby increasing the effectiveness of the catalysts.

This study, for the first time, highlights that the speed of the process is critically dependent on how easily the molecules can pass in and out of these pores.  While this may not be the case for every process, challenging some of these commonly held beliefs will surely lead to a rethink of how catalysts are designed in the future.

Interested in more?  Read this HOT, Open Access Chem Sci Edge article now!

Probing chemistry and kinetics of reactions in heterogeneous catalysts
Tristan G. A. Youngs, Haresh Manyar,  Daniel T. Bowron,  Lynn F. Gladden and Christopher Hardacre
Chem. Sci., 2013, Advance Article
DOI: 10.1039/C3SC51477C

Ruaraidh McIntosh is a guest web-writer for Chemical Science.  His research interests include supramolecular chemistry and catalysis.  When not working as a Research Fellow at Heriot-Watt University, Ruaraidh can usually be found in the kitchen where he has found a secondary application for his redoubtable skills in burning and profanity.

An essential feature of cell function and development is the transportation of molecules across the cell wall.

The maxim of ‘like dissolves like’ is well known by every high school chemist and is the reason why the cell itself does not dissolve; the cell wall and the water outside it naturally repel each other.

Whilst this is excellent news for the stability of the cell, it presents a problem for the water-soluble molecules trying to get into the cell.  If such a molecule is dissolved in water outside of the cell then it follows that it will be unhappy passing through the greasy cell wall.

Nature as always has a solution and solves this problem by effectively wrapping up these molecules in an oily layer making transport across the cell wall more efficient.  A similar concept is responsible for the cleaning action of detergent in a dirty cooking pan.

This transportation is of particular interest to the pharmaceutical industry where transport of small drug molecules into cells is of paramount importance.  Drugs can have remarkable activity in a laboratory experiment but if it cannot find its way into the cell then it will be unable to achieve this in a person.  Understanding the factors which control this process is therefore crucial.

Prof. Philip Gale’s research group at the University of Southampton along with co-workers at the Universidade de Aveiro have published a detailed and systematic study which highlights some critical features of molecules which are capable of fulfilling this role.

Interested in more?  Read this HOT Chem Sci Edge article now!

Towards predictable transmembrane transport: QSAR analysis of anion binding and transport
Nathalie Busschaert, Samuel J. Bradberry, Marco Wenzel, Cally J. E. Haynes, Jennifer R. Hiscock, Isabelle L. Kirby, Louise E. Karagiannidis, Stephen J. Moore, Neil J. Wells, Julie Herniman, G. John Langley, Peter N. Horton, Mark E. Light, Igor Marques, Paulo J. Costa, Vítor Félix, Jeremy G. Frey and Philip A. Gale
Chem. Sci., 2013, Advance Article
DOI: 10.1039/C3SC51023A

Ruaraidh McIntosh is a guest web-writer for Chemical Science.  His research interests include supramolecular chemistry and catalysis.  When not working as a Research Fellow at Heriot-Watt University, Ruaraidh can usually be found in the kitchen where he has found a secondary application for his redoubtable skills of burning and profanity.

Marilyn Monroe once sang that ‘diamonds are a girl’s best friend.’  If that is the case then it could be said that graphene, another form of carbon, has become the scientist’s best friend.  The relatively recent explosion of research conducted on graphene has been remarkable, and in 2010 resulted in a Nobel Prize for Andre Geim and Konstantin Novoselov at the University of Manchester.

Energy minimized structure from DFT calculations for a large PAH with the hydrogens removed.

Graphene can be thought of as the largest member of the polycyclic aromatic hydrocarbon (PAH) family, molecules made up of fused aromatic rings.  The interest in these carbon-based materials arises from their amazing electronic and optical properties.  The smaller members of the PAH family provide chemists an opportunity to create molecules of fixed and uniform dimensions, something which is challenging when making graphene.  Furthermore, by synthesising PAHs in a logical, stepwise fashion, we can adapt their properties to suit our own needs.

In a recent Chemical Science Edge article, the groups of Hexing Li (Shanghai Normal University) and Colin Nuckolls (Columbia University) have shown that they can construct large polycyclic aromatic hydrocarbons (PAHs) in a relatively straightforward and high yielding process. As might have been expected, such a large aromatic molecule is not particularly soluble but, emphasising the utility of their method, they are able to overcome this by adding groups to the molecule which make it more soluble.  The versatility of their approach will surely lead to the creation of even larger PAHs which will eventually serve to bridge the gap between these small molecules to the extended structures of graphene.

Interested in more?  Read this HOT Chem Sci Edge article now!

Supersized contorted aromatics
Shengxiong Xiao, Seok Ju Kang, Ying Wu, Seokhoon Ahn, Jong Bok Kim, Yueh-Lin Loo, Theo Siegrist, Michael L. Steigerwald, Hexing Li and Colin Nuckolls
Chem. Sci., 2013, 4, 2018-2023
DOI: 10.1039/C3SC50374G

Ruaraidh McIntosh is a guest web-writer for Chemical Science.  His research interests include supramolecular chemistry and catalysis.  When not working as a Research Fellow at Heriot-Watt University, Ruaraidh can usually be found in the kitchen where he has found a secondary application for his redoubtable skills in burning and profanity.