Chemical Science Blog

Many researchers use photographs of fluorescent solutions to illustrate their scientific papers but scientists in Germany have shown these photographs are more than just pictures and actually contain valuable information.

Data equivalent to multiple emission spectra extracted from a single photograph

Emission spectroscopy is considered the gold standard for characterising fluorescent solutions but analysing this data can be time consuming and non-intuitive, especially when a lot of data is involved. This led Uwe Bunz’s team at Heidelberg University to ask if photography might be a better method for obtaining this information quickly and efficiently. And the answer is yes.

Photographic and spectroscopic data can be compared using the chromaticity coordinates, r,g. These can be easily extracted from emission spectra using colour matching functions. However, in order to extract chromaticity coordinates from photographs, we have to assume that the camera is using the same set of functions. ‘There was no good way to compare information gleaned from emission spectra and photographs,’ explains Bunz.

To get around this problem Bunz’s team used pseudo colour matching functions to give chromaticity coordinates specific to their camera. These values can then be directly compared to r,g values from emission spectra, converting the camera into a three filter detector. ‘We can now interconvert fluorescence spectral data and colour information gleaned from photographs,’ says Bunz. ‘The common denominators are the chromaticity coordinates r,g.’

They tested their method on light emitting diodes (LEDs) and solutions of inorganic quantum dots and organic fluorescent dyes. In all three cases, the photo-extracted coordinates were excellent matches with the spectroscopic values.

‘It’s a very simple but very effective method for analysing fast chemical processes,’ says Manijeh Razeghi, an expert in using cameras for spectroscopy from Northwestern University in Evanston, Illinois, US. ‘Its simplicity allows it to be used by a wide variety of people with different levels of knowledge about spectroscopy.’

Repurposing a camera as a spectrometer may sound a little unorthodox but a single photograph can simultaneously capture data on multiple coloured solutions making it cheap and efficient. Its applications range from the analysis of quality control test trips to adulterations of medical drugs.

You can read also this article in Chemistry World»

Read the original journal article in Chemical Science:
Photoscopy: Spectroscopic Information from Camera Snapshots?
Uwe Bunz, Thimon Schwaebel and Sebastian Menning  
Chem. Sci., 2013, DOI: 10.1039/C3SC52928B, Edge Article

Researchers in Germany looking to find unprecedented ways of combating bacterial infection have demonstrated that certain small molecules can reduce the ability of Staphylococcus aureus to cause disease. ‘The classic antibiotic approach puts bacteria in a life or death situation, meaning that they need to become resistant in order to survive. We aimed to find a way of reducing the ability of bacteria to make the toxins that harm eukaryote cells during infection, without putting them under selective pressure,’ explains Stephan Sieber of the University of Technology in Munich who led the study.

α-methylene-γ-butyrolactones can inhibit virulence factors like α-haemolysin (hla) to render pathogenic bacteria harmless

 Transcriptional regulators control the virulence factors in bacteria, that enable a microorganism to establish itself within a host or enhance its potential to cause disease, by directly binding to DNA promoter regions of toxin-encoding genes. In the study, the researchers identified a series of α-methylene-γ-butyrolactones that covalently modify cysteine residues on three transcriptional regulators in S. aureus, markedly decreasing the expression of α-haemolysin, one of the most prominent virulence factors.

Read the full article in Chemistry World»

Read the original journal article in Chemical Science:
α-Methylene-γ-butyrolactones attenuate Staphylococcus aureus virulence by inhibition of transcriptional regulation
Martin H Kunzmann, Nina C. Bach, Bianca Bauer and Stephan Axel Sieber  
Chem. Sci., 2013, Accepted Manuscript, DOI: 10.1039/C3SC52228H

Artificial proteins could be closer to participating in natural biochemical pathways after UK and US researchers show that bacteria will process amino acid sequences entirely unrelated to any natural protein to produce a fully functioning cytochrome.

Scientists trick E. coli into producing their artificial proteins © Shutterstock

The burgeoning field of synthetic biology demands that functional artificial proteins and enzymes seamlessly integrate with natural proteins and substrates. ‘We’re trying to build artificial proteins that exhibit some of the properties and chemistries of natural proteins,’ explains team member Ross Anderson from the University of Bristol.

Anderson and colleagues have used a relatively new methodology called the maquette approach that lets them escape some of the complexities of natural systems to construct their artificial cytochrome. They begin with a generic protein sequence designed only to fold into a 4-helix bundle. Engineered elements are added onto the stripped-down protein chassis; the role of every residue in the amino acid sequence is defined and adjusted by altering critical residues.

Read the full article in Chemistry World»

Read the original journal article online:
Constructing a man-made c-type cytochrome maquette in vivo: electron transfer, oxygen transport and conversion to a photoactive light harvesting maquette
J. L. Ross Anderson, Craig T. Armstrong, Goutham Kodali, Bruce R. Lichtenstein, Daniel W. Watkins, Joshua A. Mancini, Aimee L. Boyle, Tammer A. Farid, Matthew P Crump, Christopher C. Moser and P. Leslie Dutton  
Chem. Sci., 2014, Advance Article, DOI: 10.1039/C3SC52019F

Targeting the endoplasmic reticulum with a membrane-interactive luminescent ruthenium(II) polypyridyl complex
Martin R. Gill, Denis Cecchin, Michael G. Walker, Raminder S. Mulla, Giuseppe Battaglia, Carl Smythe and Jim A. Thomas
Chem. Sci., 2013,4, 4512-4519
DOI: 10.1039/C3SC51725J, Edge Article

Free to access until 15th December 2013

Benz[c]indeno[2,1-a]fluorene: a 2,3-naphthoquinodimethane incorporated into an indenofluorene frame
Hirokazu Miyoshi, Shunpei Nobusue, Akihiro Shimizu, Ichiro Hisaki, Mikiji Miyata and Yoshito Tobe
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C3SC52622D, Edge Article

Free to access until 15th December 2013

Sodium hydroxide-assisted growth of uniform Pd nanoparticles on nanoporous carbon MSC-30 for efficient and complete dehydrogenation of formic acid under ambient conditions
Qi-Long Zhu, Nobuko Tsumori and Qiang Xu
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C3SC52448E, Edge Article

Free to access until 15th December 2013

Direct Observation of a Lithiated Oxirane: A Synergistic Study Using Spectroscopic, Crystallographic, and Theoretical Methods on the Structure and Stereodynamics of Lithiated ortho-Trifluoromethyl Styrene Oxide
Vito Capriati, Antonio Salomone, Filippo Maria Perna, Saverio Florio, Aurelia Falcicchio, Anna Moliterni, Sten O. Nilsson Lill, Dietmar Stalke and Reent G. Michel
Chem. Sci., 2013, Accepted Manuscript
DOI: 10.1039/C3SC52099D, Edge Article

Free to access until 15th December 2013

A new class of MRI (magnetic resonance imaging) contrast agents developed by scientists in the UK is promising to deliver clearer images in less time. ‘In any NMR experiment you are chasing sensitivity. We have enhanced the intrinsic ability to observe an MRI probe signal by a factor of 20,’ explains David Parker of Durham University who led the study. 

MRI is used in clinical settings to image the inside of the body. It uses strong magnetic fields and radio waves to probe the behaviour of nuclei that possess nuclear spin. Chemical shifts from proton NMR normally fall between 0–12ppm but water and fat resonate at 4.7 and 1.3ppm, respectively, and can overlap with MRI probe signals. Parker’s new probes shunt the spectral window of MRI scans well away from these interfering signals, a concept he describes as ‘moving the goalposts’. The probes consist of lanthanide complexes with a t-butyl group and the distance between the lanthanide and t-butyl group was fixed to optimise the rate of decay of the t-butyl signal as well as move its chemical shift. Data acquisition was possible just a few minutes after administering the probe and the signal from the lanthanide induced relaxation of the nine protons in the t-butyl groups has been shifted by up to 80ppm. 

Proton NMR spectra showing the shifted t-butyl resonances in some of the new dysprosium and thulium complexes

  Read the full article in Chemistry World»

Read the original journal article in Chemical Science:
Moving the goal posts: enhancing the sensitivity of PARASHIFT proton magnetic resonance imaging and spectroscopy
Peter Harvey, Andrew M. Blamire, J. Ian Wilson, Katie-Louise N. A. Finney, Alexander M. Funk, P. Kanthi Senanayake and David Parker  
Chem. Sci., 2013,4, 4251-4258, DOI: 10.1039/C3SC51526E

Scientists from Japan have harvested light energy using an exceptionally large number of light absorbers to relay photons via antennas into one final energy acceptor. This two-step sequence closely mimics natural photosynthesis, resulting in greater and more efficient energy transfer.

Previously, researchers had only used one-step light harvesting systems, greatly limiting the number of absorbers able to feed light into a single reaction centre. Now, by imitating photosynthetic systems, Osamu Ishitani at the Tokyo Institute of Technology, Shinji Inagaki at the Toyota Central R&D labs and their co-workers have efficiently harvested light using the highest number of artificial leaves to date.

Read the full article in Chemistry World»

Read the original journal article in Chemical Science:
Efficient Light Harvesting via Sequential Two-Step Energy Accumulation Using a Ru–Re5 Multinuclear Complex Incorporated into Periodic Mesoporous Organosilica
Yohei Yamamoto, Hiroyuki Takeda, Tatsuto Yui, Kotaro Ueda, Kazuhide Koike, Shinji Inagaki and Osamu Ishitani 
Chem. Sci., 2013, Accepted Manuscript, DOI: 10.1039/C3SC51959G

In the presence of half mustard, the dithiol does not react with the squaraine dye so the dye’s blue colour is visible

Scientists in the US are trying to develop a new detection system for the chemical warfare agent mustard gas. 

There is no antidote to mustard gas, which burns the skin, eyes and respiratory system. Victims not killed by an attack are left severely incapacitated. It is an environmentally persistent chemical and its cruel effects can take around 12 hours to take hold. A cheap and simple sensor to alert civilians and emergency responders to its presence is obviously desirable. 

Eric Anslyn and Vinod Kumar at the University of Texas at Austin are getting closer to such a system. With the knowledge that chlorine atoms in mustard gas will readily react with good nucleophiles like thiols, they have designed a dithiol and squaraine dye system to give a clear colour change in the presence of the mustard gas simulant 2-chloroethyl ethyl sulfide, also known as half mustard. 

Metallohelices with activity against cisplatin-resistant cancer cells; does the mechanism involve DNA binding?
Viktor Brabec, Suzanne E. Howson, Rebecca A. Kaner, Rianne M. Lord, Jaroslav Malina, Roger M. Phillips, Qasem M. A. Abdallah, Patrick C. McGowan, Alison Rodger and Peter Scott
Chem. Sci., 2013, Advance Article
DOI: 10.1039/C3SC51731D, Edge Article

Free to access until 13th October 2013

Topological isomerism in a chiral handcuff catenane
Karel J. Hartlieb, Anthea K. Blackburn, Severin T. Schneebeli, Ross S. Forgan, Amy A. Sarjeant, Charlotte L. Stern, Dennis Cao and J. Fraser Stoddart
Chem. Sci., 2013, Advance Article
DOI: 10.1039/C3SC52106K, Edge Article

Free to access until 13th October 2013

Development of cell-impermeable coelenterazine derivatives
Eric Lindberg, Shin Mizukami, Keiji Ibata, Takashi Fukano, Atsushi Miyawaki and Kazuya Kikuchi
Chem. Sci., 2013, Advance Article
DOI: 10.1039/C3SC51985F, Edge Article

Free to access until 13th October 2013

Monolayers of trimesic and isophthalic acid on Cu and Ag: the influence of coordination strength on adsorption geometry
Izabela Cebula, Hao Lu, Michael Zharnikov and Manfred Buck
Chem. Sci., 2013, Accepted Manuscript
DOI: 10.1039/C3SC52137K, Edge Article

Free to access until 13th October 2013

Scientists in the US have successfully used a template directed protocol to synthesise two topological isomers of a handcuff catenane. Handcuff catenanes are mechanically interlocked molecules where two covalently bound rings, called the ditopic host, are interlocked by a third ring threaded through both rings of the ditopic host. Only three other mechanically interlocked molecules with the handcuff topology have been reported before – they are very difficult to synthesise.

Previous handcuff catenanes have all been achiral and have only demonstrated one way to thread the third ring through the diptopic host. The handcuff catenane made by Fraser Stoddart and colleagues at Northwestern University has two distinctive topologies – it is impossible for one to be converted into the other, unless covalent bonds are broken and then re-made. The stereochemistry demonstrated by Stoddart’s handcuff catenanes is interesting because as well as being topologically chiral they also display Euclidian chirality.

The different isomers of the handcuff catenane and their relationship to one another

The different isomers of the handcuff catenane and their relationship to one another
A template directed synthesis between the π-electron-rich bis-1,5-dioxynaphtho[50]crown-14 and the precursors of two fused π-electron-deficient cyclobis(paraquat-p-phenylene) cyclophanes was used to make the topologically complex molecules. The handcuff catenanes could have future applications in molecular switches.

This article appeared in Chemistry World on 9^th September 2013.

You can also read the original journal article in Chemical Science:
Topological isomerism in a chiral handcuff catenane
Karel J. Hartlieb, Anthea K Blackburn, Severin Thomas Schneebeli, Ross S Forgan, Amy Sarjeant, Charlotte L Stern, Dennis Cao and J. Fraser Stoddart
Chem. Sci., 2013, Accepted Manuscript, DOI: 10.1039/C3SC52106K