Chemical Science Blog

Scientists in China have developed an intelligent nanoparticle system that delivers a chemotherapeutic and radiosensitiser drug directly to the nucleus of cancer cells. Tests suggest this intranuclear radiosensitisation technique could intensify the effects of radiotherapy.

Along with radiotherapy, chemotherapy assumes a frontline position in the battle against cancer. However, many drugs fail to enter cancer cell nuclei when they should. This often leads to multidrug resistance in tumours and a diminished response to radiotherapy.

Read the full article in Chemistry World»

Read the original journal article for free in Chemical Science:
Design of An Intelligent Sub-50 nm Nuclear-targeting Nanotheranostic System for Imaging Guided Intranuclear Radiosensitization
Wenpei Fan, Bo Shen, Wenbo Bu, Xiangpeng Zheng, Qianjun He, Zhaowen Cui, Kuaile Zhao, Shengjian Zhang and Jianlin Shi  
 Chem. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4SC03080J, Edge Article

Inspired by nature, scientists in Australia have united light and chlorophyll to generate a range of polymers that have biomedical applications.

During photosynthesis, chlorophyll is activated by visible light, and an electron is promoted from its ground state to an excited state. In plants, this excited electron goes on to react with carbon dioxide and water, via photoinduced electron transfer (PET). However, in the system devised by Cyrille Boyer and colleagues at the University of New South Wales, the excited electron is donated to a monomer, generating a radical, which then goes on to further react and generate polymers through a process known as living radical polymerisation.

Read the full article in Chemistry World»

Read the original journal article in Chemical Science – it’s free to access:
Utilizing the electron transfer mechanism of chlorophyll a under light for controlled radical polymerization
Sivaprakash Shanmugam, Jiangtao Xu and Cyrille Boyer  
Chem. Sci., 2015, Advance Article
DOI: 10.1039/C4SC03342F, Edge Article

In this Chemical Science Edge Article, the Anderson group and colleagues at the Universitiy of Oxford describe ultra-fast light harvesting materials which function in a similar way to various natural light harvesters, like, for example, those found in the chlorophyll assemblies of purple bacteria. These materials represent excellent candidates for use in next generation carbon based solar cells. 

The materials, which may contain up to 24 porphyrin units separated by conjugating butadiyne bridges, can measure up to 10nm in diameter. Recent advances in template directed synthesis mean these molecules have become more accessible.

Barriers to energy delocalisation are overcome due to distortions that occur in the molecular structure. A rigidifying template was used to probe the effect of distortions – without a coordinating constraint present, significantly different behaviour was observed, underlying the importance of flexibility to the behaviour observed.

24 prophyrin containing nanoring, and an example of a 6 unit ring containing a rigidifying template

Physical techniques were used to characterise the complex phenomena being observed, including time resolved photoluminescence spectroscopy, using femtosecond LASERs and steady state fluorescence. Further information about electronic structure was gained by comparing spectra of the ring structures with those of  linear oligomeric analogues. 

The authors describe synthetic materials which show a level of light harvesting and rapid energy delocalising ability, usually only seen in natural systems. The promise of technological applications which exploit these properties will drive the study of the fundamental physics and chemistry of such fascinating systems. 

Read this Chemical Science Edge Article today: 

Ultrafast Delocalisation of excitation in synthetic light-harvesting nanorings
Chaw-Keong Yong, Patrick Parkinson, Dmitry V. Kondratuk, Wei-Hsin Chen, Andrew Stannard, Alex Summerfield, Johannes K. Sprafke, Melanie C. O’Sullivan, Peter H. Beton, Harry L. Anderson and Laura M. Herz.
DOI: 10.1039/C4SC02424A

Flow reactors are edging towards self-regulation, thanks to researchers in the UK.

Inspired by previous self-optimised flow systems with in-line analytical monitoring, Lee Cronin’s group at the University of Glasgow has extended this concept so that multinuclear and 2D NMR can be performed in the fume hood.

Read the full article in Chemistry World»

Read the original journal article in Chemical Science:
A Self Optimizing Synthetic Organic Reactor System Using Real-time In-line NMR spectroscopy
Lee Cronin, Victor Sans, Luzian Porwol and Vincenza Dragone  
Chem. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4SC03075C, Edge Article

Macrocyclic scaffolds have been hugely influential in supramolecular chemistry and now scientists in China have synthesised a new addition to this pool of chemical building blocks.

The biphen[n]arene macrocycles, created by Chunju Li of Shanghai University and colleagues, are based on 4,4’-biphenol and are reminiscent of popular phenol and biphenol based macrocycles such as  calix[n]arenes, resorcin[n]arenes and pillar[n]arenes.

Macrocyclic arenes play a very important role in supramolecular chemistry

Read the full article in Chemistry World»

Read the original journal article in Chemical Science:
Biphen[n]arenes
Huanqing Chen, Jiazeng Fan, Xiaoshi Hu, Junwei Ma, Shilu Wang, Jian Li, Yihua Yu, Xueshun Jia and Chunju Li  
Chem. Sci., 2015, Advance Article
DOI: 10.1039/C4SC02422B, Edge Article

The ability to select which common building blocks of a mixture react, producing different products on demand, holds great promise for chemical synthesis. Think about systems where you have to add a great deal of additional components to prevent one reaction route and initiate another; wouldn’t it be simpler if you could add just one component that switches the chemical transformation?

This is what David Leigh and his team from the School of Chemistry at The University of Manchester have done. They have created a rotaxane with two different activation sites which promote different reactions and thus different products in the same mixture. The macrocycle position within the rotaxane is controlled and leads to one of the active sites being blocked while the other is active.

Switchable Rotaxane Organocatalyst – the position of the macrocycle either blocks or reveals one of the catalytic sites, leading to different products being formed from the same mixture of building blocks

The developed system promotes Michael addition reactions through iminium ion or hydrogen-bond-activated catalysis. The switch between these modes is provided by acid-base control of the position of the rotaxane macrocycle and leads to different products being formed.

This elegant catalytical switch approach holds great promise for chemical transformation and organic synthesis generally. To read the details of the transformations and, more importantly, how to make the rotaxane, read the Chemical Science paper today!

Read this Open Access Chem Sci article in full:
Selecting Reactions and Reactants using a Switchable Rotaxane Organocatalyst with Two Different Active Sites
David A Leigh, Jack Beswick, Victor Blanco, Guillaume De Bo, Urszula Lewandowska, Bartosz Lewandowski and Kenji Mishiro
Chem. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4SC03279A, Edge Article

Reprogramming the genetic code of bacteria to incorporate an unnatural amino acid has allowed scientists in the Netherlands to create a new metalloenzyme capable of catalysing an enantioselective reaction.

The artificial metalloenzymes were applied in a catalytic asymmetric Friedel–Crafts alkylation reaction

‘Nature is extremely good at catalysing reactions with very high rate accelerations and very high selectivity. But it does so, from our perspective, with a relatively limited set of reactions,’ explains Gerard Roelfes from the University of Groningen, the Netherlands, who led the study. His group is targeting existing reactions that use traditional catalysts, but fail to achieve the same rate acceleration and selectivity as enzyme catalysed reactions.

Read the full article in Chemistry World»

Read the original journal article in Chemical Science:
Novel artificial metalloenzymes by in vivo incorporation of metal-binding unnatural amino acids
vana Drienovská, Ana Rioz-Martínez, Apparao Draksharapu and Gerard Roelfes  
Chem. Sci., 2015, Advance Article
DOI: 10.1039/C4SC01525H, Edge Article

University chemistry students are taught that the shapes and electronics of inorganic complexes are predictable. For example, d8 square-planar Pd(ii) and Pt(ii) complexes are invariably low spin, while d3–d7 tetrahedral complexes are high spin. Now, researchers in the US have thrown away the textbook by synthesising a square-planar Fe(ii) complex that is not only high spin, but has a different core (FeO2NCl) to the only other examples of this complex type, all of which feature an FeO4 core. 

Read the full article in Chemistry World» 

Read the original journal article in Chemical Science:
A high-spin square-planar Fe(II) complex stabilized by a trianionic pincer-type ligand and conclusive evidence for retention of geometry and spin state in solution
M. E. Pascualini, N. V. Di Russo, A. E. Thuijs, A. Ozarowski, S. A. Stoian, K. A. Abboud, G. Christou and A. S. Veige  
Chem. Sci., 2015, Advance Article
DOI: 10.1039/C4SC02634A, Edge Article