HIGHLIGHTS


compatible with the method described here (Figure 3). Complementary methods were


used to validate the approach such as a high performance liquid chromatographic MS/MS method for the first group using isotope labelling. Parameters considered included derivatisation reaction, separation, linearity of response on a high range of concentrations, correction of matrix effect as well as unambiguous assignment of each metabolite. In spite of the complexity, this has been fully validated by the Food and Drug Administration (FDA) as well as the European Medicines Agency (EMA) according to their specific recommendations with many criteria including linearity, precision, accuracy, dilution integrity, selectivity, carryover and stability. Robustness and reproducibility of the method were demonstrated and it is currently being applied in a cohort of asthma and COPD patients.


Figure 3 Illustration of the procedure used for preparation of samples, including isotopic labelling and calibration of method with resulting chromatogram obtained showing recognition of relevant amino acids metabolites


Bacterial detection method based on cell-imprinted microplates Conventional methods for accurate bacterial identification, such as colony counting, are time consuming, especially when identification is re- quired quickly to avoid high mortality rates. In order to improve the swift- ness with which the identification is provided other methods, including fluorescence activated cell sorting and cell imprinted polymers (CIPs) have been suggested. Shan et al have reported a


high-throughput bacterial detection method based on a cell-imprinted 96-well microplate (Analyst, doi: 10.1039/c7an02057k). This method uses bacterial cell imprinting techniques with a polypyrrole and Nafion complex deposited on a gold nanoparticle coated microplate. This process can provide a


very quick (30 minutes) and highly selective detection of targeted cells. Conventional methods take much longer, up to several days, and


Organic chemistry


G. RICHARD STEPHENSON University of East Anglia, UK


Turning a molecular-scale crank The photochemistry of the N=N double bond remains a focus for organic research groups interested in using light to cause and control molecular motion. When inserted between two formamides, the resulting N-(C=O)-N=N-(C=O)-N motif (Figure 1) has many merits, which are far from fully explored and developed. Such structures are relatively easy to make using simple building blocks, and can be reliably expected to have valuable


N


Rotation 1 Rotation 2


(a)


O N N O


(a)


photochemical properties and good photostability.


This is born out in a study that


combines time-resolved infrared spectroscopy and quantum- mechanical calculations to reveal


N 1


Figure 1 Two rotational motions that allow 1 to serve as a light-driven molecular crank [(a) = N-(C=O)-N=]


O 46 02 | 2018 (a)


MDI-PTHF Polyurethane O


B O O C O


specific receptors can be fabricated for specific cellular recognition. There is even a strong indication that the microplates could be particularly selective to Escherichia Coli O157:H7, one of the bacteria recognised to cause severe diseases, as well as discriminating specific bacteria from a mixture.


In addition, the preparation is


also rapid as CIPs, which derive from molecular imprinting technique, can be used for fast preparation of cavities designed to bind to desired bacteria. In comparison, antibodies commonly used as receptors for the immune system can take several months to prepare. Many parameters were tested and/ or optimised, they included binding performance, thickness of the cell imprinted polymer and selectivity, shown to be twenty fold for the target compared with others. Techniques used were atomic force microscopy, scanning electron microscopy and fluorescence imaging.


new dynamic conformational effects in azodicarboxamides (S. Amirjalayer, A. Martinez-Cuezva, J. Berna, S. Woutersen, W. J. Buma; Angew. Chem. Int. Ed., 2018, 57, 1792). Light-driven partial rotations take


place around the C-N bonds that connect each formamide carbonyl group to the central azo group in compound 1. These molecules behave somewhat like the cranks on a bicycle or, as the authors comment, like a ‘pedalo’, with energy from light replacing foot-power to turn the cranks. Of course, having achieved a


workable molecular-scale crank, the next issue is how to make it drive a molecular-scale machine.


O A O B'


MDI-PTHF Polyurethane


(a)


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