Hot Articles – Page 26 – Chemical Science Blog

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Nanopipette-based sensors to detect peanut allergies

15 Nov 2012

Scientists in the US and Ireland have developed a new approach to quantitative resistive-pulse sensing, using a nanopipette-based sensor to selectively detect antibodies to peanut allergens (about 1% of Americans suffer from peanut allergies, they say).

Peanut allergens are glycoproteins, and these cause an immune response elevating IgE (Immunoglobulin E) antibody levels in people with a peanut allergy. The increased immunoglobulin levels can be measured by the nanopipette sensor and will help to detect the likelihood of severe allergy episodes.

The nanopipettes work by sensing an analyte as it enters their nanometre-sized pores. The particle must be small enough to fit through the hole, but large enough to cause a measurable change in the recorded ion current. This technique allows label-free detection of antibodies.

Read the ‘HOT’ article:

Resistive-Pulse Measurements with Nanopipettes: Detection of Au Nanoparticles and Nanoparticle-Bound Anti-peanut IgY
Y Wang et al, Chem. Sci., 2012, DOI: 10.1039/c2sc21502k

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Fluorescence, camera, action

12 Nov 2012

Fluorescence responses can be analysed using digital photography instead of spectroscopy, say scientists in Germany. The technology could eventually be integrated into smart phones.

Uwe Bunz and his colleagues from the University of Heidelberg used digital photography to study the optical changes occurring when different pyridine-substituted cruciform (cross-conjugated) fluorophores (XF) were subjected to protonation. They protonated the nitrogen on the pyridine and observed the colour changes of the XFs in the presence of carboxylic acids.

Instrument set-up for taking photographs of emission colour

The team extracted data from the photographs by transforming the red, green and blue (RGB) values into numerical values, a process that helps define the colour and removes brightness information. ‘The method is quick and inexpensive, and large data quantities can be stored and acquired in seconds,’ says Bunz.

See the Chemistry World article in full or read the paper from Chemical Science:

Digital photography for the analysis of fluorescence responses
Thimon Schwaebel , Oliver Trapp and Uwe H. F. Bunz
Chem. Sci., 2013, DOI: 10.1039/C2SC21412A

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Effect of Solvent Molecules on Potential Energy Surfaces

12 Nov 2012

Potential energy surfaces of reactions are usually measured in the gas phase. However the vast majority of chemical reactions in the laboratory are conducted in solvent. What effect do these solvent molecules have on the potential energy surfaces that have been measured in the gas phase? Andrew Orr-Ewing and colleagues have been finding out.

They have used ultrafast time-resolved broadband infra-red absorption spectroscopy to study the reaction of chlorine atoms with hydrocarbons in chlorinated solvent.

Two timescales were found, which corresponded to prompt reaction of the chlorine atom with the hydrocarbon, which was most likely located in the immediate solvent shell, and a slower reaction following diffusion into the bulk solvent. The presence of solvent molecules also partially suppresses the presence of vibrationally excited products that occur when the exothermic reaction is sufficient to form vibrationally hot products.

: Reaction of chlorine atoms with a hydrocarbon in chlorinated solvent.

This work extends previous experiments conducted with cyanide radicals in solvent and general conclusions on the effect of solvent molecules on the potential energy surface are now emerging.

To find out more, download the Chemical Science article today (free to access until the 7th of December 2012).

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Synthesis of antibiotics derivatives to aid further drug discovery

08 Nov 2012

A new and efficient way to make β-lactams, the key components of common antibiotics such as penicillin, has been developed by US scientists.

The team made the β-lactams from simple aldehydes via a multi-component catalytic asymmetric aziridination reaction. The reaction is high-yielding, stereospecific and diastereoselective. It should aid new drug discovery.

Read the Chemical Science article in full:

Multifaceted Interception of 2-Chloro-2-Oxoacetic Anhydrides: A Catalytic Asymmetric Synthesis of b-Lactams
L Huang et al.
Chem. Sci., 2012, DOI: 10.1039/c2sc21240d

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Quantifying the strength of the chemical bond using the properties of the participating species

06 Nov 2012

Unlike conventional electromagnetic interactions, the chemical bond has not been quantified in strength by any known property of the participating species, until now.

Scientists in China say that bond energy (EAB), a quantitative measure of the bond strength, can be decoupled into two contributions of the participating reactants, which is a new principle.

The team verified their theory with more than 300 bonds, including covalent bonds in molecules and adsorption bonds on metal surfaces; this can be applied in a wide range of chemical reactions. Particularly, the characteristic complex quantity, termed ‘chemical amplitude’ can be used to describe accurately the chemical reactivity of both molecules and metal surfaces, which is an advantage when studying heterogeneous catalysis.

The work should allow scientists to make a direct evaluation of the bond energy and also reveal new aspects of the chemical interaction, they say.

Read this ‘HOT’ Chemical Science Edge Article:

Bond-Energy Decoupling: Principle and Application to Heterogeneous
Catalysis Bing Huang , Lin Zhuang , Li Xiao and Juntao Lu
Chem. Sci., 2012, DOI: 10.1039/C2SC21232C

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New method to create antibody mimics for improved therapeutics

01 Nov 2012

US scientists have reported a new method to create antibody mimics that could be used to make new and improved therapeutics.

Fusion proteins contain segments derived from two or more different precursors. The proteins allow multiple biological functions to be combined in a single entity. The most successful fusion protein therapeutics contain the crystallisable fragment (Fc) region of antibodies. But they are not easy to make and modify. The team has come up with two strategies to modify antibody Fc fragments using chemical modification, leading to the creation of novel Fc-synthetic molecule hybrids.

The strategy also allows Fc domains to be used as building blocks that can be appended to virtually any class of synthetic molecules. This allows the pharmacokinetic improvements imparted by Fc to be used in many different drug delivery contexts, and could add potential immunological function to many different constructs.

Read the ‘HOT’ Chemical Science article today:
Synthetically Modified Fc Domains as Building Blocks for Immunotherapy Applications
C Netirojjanakul et al, Chem. Sci., 2012, DOI: 10.1039/c2sc21365f

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A system to mimic the complexity of biological networks

29 Oct 2012

A stimuli-responsive system that brings chemists one step closer to mimicking the complexity of biological networks has been developed by scientists in the UK, Australia and the US.

Biological systems are complicated as they can produce multiple responses to stimuli at the same time. The team says that the key to unravelling the origin of life may come from studying the complex interactions of molecules.

They have discovered a self-assembled cage molecule that consists of a system of interconverting diastereomers in solution. When anionic guest molecules are added, the system adapts, expressing a new combination of diastereomers that synergistically bind the guest molecules. Not only do the cage diastereomers interconvert, the volume of the individual cages adapts physically through the rotation of bonds, providing a tailored binding pocket for the guest lined with hydrogen-bond donors.

This two-fold adaptation is a feature of the responses to external stimuli displayed by biological systems, something that has not previously been observed in synthetic systems. Complex and functional synthetic systems of this type will lead to the design of more effective systems for host-guest recognition and the development of systems approaching the complexity of those that exist in nature.

Read the ‘HOT’ Chemical Science article today:

A Stimuli Responsive System of Self-Assembled Anion-Binding Fe₄L₆⁸⁺ Cages
Jack Kay Clegg, Jonathan Cremers, Andrew J Hogben, Boris Breiner, Maarten M. J. Smulders, John D. Thoburn and Jonathan Nitschke
Chem. Sci., 2012, DOI: 10.1039/C2SC21486E

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Less is more for DNA reactions

26 Oct 2012

A technique allowing the use of small amounts of DNA for efficient DNA-directed chemistry has been developed by scientists in Germany.

Oliver Seitz and Alexander Roloff at the Humboldt University of Berlin in Germany have made it possible to use incredibly small amounts of nucleic acids in important DNA-directed reactions.

DNA-directed chemistry is used in applications as diverse as nanowire synthesis and light harvesters to drug screening and diagnostics. This includes DNA-directed ligation reactions, in which two molecules are chemically joined. However, gaining enough of a particular DNA sequence from biological sources is challenging. Living organisms usually produce only small amounts and these may not be exactly uniform in nature.

The polymerase chain reaction (PCR) is the answer to this availability problem. PCR uses the enzyme polymerase to copy a small sample of DNA – the template – and make multiple copies of it with high accuracy and efficiency.

Read the full Chemistry World article or read the Chemical Science article in full:

Article Bioorthogonal reactions challenged: DNA templated native chemical ligation during PCR
Alexander Roloff and Oliver Seitz
Chem. Sci., 2012, DOI: 10.1039/C2SC20961F

DNA templated native chemical ligation during PCR

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Plant power – Organocatalytic conversion of cellulose into a platform chemical

24 Oct 2012

Viable alternatives to fossil fuels are a vital area of research for chemists as current deposits dwindle. To combat our reliance on these fuels, US scientists have discovered a new route for turning the carbohydrate cellulose – the most abundant organic molecule on Earth – into 5-(hydroxymethyl)furfural (HMF), a promising precursor molecule to alternative fuels.

Whereas conventional methods for converting carbohydrates into HMF have involved the use of harsh reaction conditions and toxic heavy metal catalysts, the route proposed by Ronald Raines and co-workers at the University of Wisconsin-Madison uses a one-pot, low temperature approach that utilises less toxic organocatalysts instead.

Converting cellulose to HMF is a three-step process. It consists of hydrolysis of cellulose to glucose, isomerisation of glucose to fructose and dehydration of fructose to HMF. The hardest step is the transformation from glucose to fructose and it is difficult to achieve this without using a catalyst. So, the team used a phenylboronic acid organocatalyst combined with magnesium chloride and mineral acids to get HMF in yields of up to 54%, a yield comparable to using toxic heavy metal catalysts. Phenylboronic acids have some catalytic activity, but the magnesium chloride and mineral acids are needed to boost the efficiency of the conversion process.

View the whole Chemistry World article…

Read the Chemical Science paper in full:

Organocatalytic conversion of cellulose into a platform chemical
Benjamin R. Caes , Michael J. Palte and Ronald T. Raines
Chem. Sci., 2013, DOI: 10.1039/C2SC21403B

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Super-resolution single-molecule imaging

22 Oct 2012

This exciting article just published in Chemical Science by Professor W.E. Moerner and colleagues describes a novel method of introducing fluorophores of single-molecule quality into live bacterial cells for super-resolution imaging studies.

Single-molecule fluorescence imaging works by converting a dark fluorogen into a bright emitter. The really interesting aspect of this current study is that this conversion is achieved enzymatically. They have synthesised a nitro-aryl fluorogen (dark fluorogen) which is converted by a nitroreductase enzyme into a push-pull red-emitting fluorophore (bright emitter).

This new method allows the neutral dye molecule to enter the cell in a fluorescently ‘deactivated’ state. The substrate is then photoactivated by reaction with the enzyme, producing the fluorescent products – which is bright and detectable on the single-molecule level. The concentration can also be controlled by the level of substrate uptake – providing the opportunity for a variety of novel labeling systems.

The authors also present a detailed characterization of the spectral and photophysical properties of the fluorescent product, as well as the enzymatic kinetics in vitro.

Read the full article:
Enzymatic Activation of Nitro-Aryl Fluorogens in Live Bacterial Cells for Enzymatic Turnover-Activated Localization Microscopy
Marissa K. Lee, Jarrod Williams, Robert Twieg, Jianghong Rao and W.E. Moerner
Chem. Sci., 2012, DOI: 10.1039/C2SC21074F

Take a look at the high-quality physical chemistry research recently published in Chemical Science:

Vibrationally resolved dynamics of the reaction of Cl atoms with 2,3-dimethylbut-2-ene in chlorinated solvents
Fawzi Abou-Chahine, Stuart Greaves, Greg Dunning, Andrew Orr-Ewing, Gregory M Greetham, Ian P Clark and Michael Towrie
Chem. Sci., 2012, DOI: 10.1039/C2SC21267F

Nanomechanical properties of molecular-scale bridges as visualised by intramolecular electronic energy transfer
Anthony Harriman, Effat Bahaidarah, Raymond Ziessel, Mohammed Alamiry and Delphine Hablot
Chem. Sci., 2012, DOI: 10.1039/C2SC21505E

Role of conformational structures and torsional anharmonicity in controlling chemical reaction rates and relative yields: butanal + HO2 reactions
Jingjing Zheng, Prasenjit Seal and Donald G. Truhlar
Chem. Sci., 2013, DOI: 10.1039/C2SC21090H

Tridentate Cobalt complexes as alternate redox couples for high efficiency Dye Sensitized Solar Cells
Ben Aribia Kais, Thomas Moehl, Shaik M Zakeeruddin and Michael Gratzel
Chem. Sci., 2012, DOI: 10.1039/C2SC21401F

Cu2O|NiOx nanocomposite as an inexpensive photocathode in photoelectrochemical water splitting
Chia-Yu Lin, Yi-Hsuan Lai, Dirk Mersch and Erwin Reisner
Chem. Sci., 2012, DOI: 10.1039/C2SC20874A

Perspective
Impurities in graphenes and carbon nanotubes and their influence on the redox properties
Martin Pumera, Adriano Ambrosi and Elaine Lay Khim Chng
Chem. Sci., 2012, DOI: 10.1039/C2SC21374E

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