Showing papers by "Gareth A. Morris published in 2017"
TL;DR: A new technique, compatible with all current pure shift methods, is presented that suppresses such sidebands to arbitrary order, allowing ultraclean spectra to be obtained.
43 citations
TL;DR: In this article, a modified version of the PSYCHE method was used to suppress couplings in the direct dimension, which allows straightforward determination of homonuclear couplings, and illustrates the need for care when combining pure shift data acquisition with multiple pulse methods.
22 citations
TL;DR: A new family of NMR experiments for mixture analysis (Relaxation-Encoded Selective TOCSY, REST) allows the extraction of component subspectra from mixtures using isotropic mixing to label whole spin systems with the relaxation times.
22 citations
TL;DR: In this paper, the authors evaluated matrix-assisted matrix assisted diffusion-ordered spectroscopy (MAD) for separating the signals of both acid and basic species using normal and reverse micelles as matrices.
Abstract: NMR is the most versatile tool for the analysis of organic compounds and, in combination with Diffusion-Ordered Spectroscopy (‘DOSY’), can give information on compounds in complex mixtures without the need for physical separation. In mixtures where the components' diffusion coefficients are nearly identical, for example because of similar sizes, Matrix-Assisted DOSY (‘MAD’) can help separate the signals of different constituents, resolving their spectra. Unfortunately, DOSY (including MAD) typically fails where signals overlap, as is common in 1H NMR. Using 19F NMR avoids such problems, because the great sensitivity of the 19F chemical shift to local environment leads to very well-dispersed spectra. Another advantage is the absence of any 19F background signals from the matrices typically used, avoiding interference with the analyte signals. In this study, differentiation among fluorophenol and fluoroaniline isomers was evaluated using normal and reverse micelles—of sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) and dioctyl sodium sulfosuccinate (AOT)—as matrices. These surfactants provide useful diffusion separation in these difficult mixtures, with all the solutes interacting with the matrices to different extents, in some cases leading to differences in diffusion coefficient of more than 30%. The best matrices for separating the signals of both acid and basic species were shown to be AOT and CTAB, which are useful over a wide range of surfactant concentration. Copyright © 2016 John Wiley & Sons, Ltd.
14 citations
TL;DR: The self-assembling tendencies of guanosine-5'-monophosphate (GMP) can be drastically increased using polyamines, with potential applications in the production of biocompatible smart materials, as well as for the design of antitumor drugs based on G-quadruplex stabilization.
Abstract: The self-assembling tendencies of guanosine-5'-monophosphate (GMP) can be drastically increased using polyamines, with potential applications in the production of biocompatible smart materials, as well as for the design of anti-tumoral drugs based on G-quadruplex stabilization. Results from scanning electron microscopy (SEM), wide angle X-ray scattering (WAXS), rheology and nuclear magnetic resonance (NMR) z-spectroscopy studies are presented.
12 citations
TL;DR: The addition of co-solutes to aid the separation of signals from molecules of similar size in matrix-assisted DOSY experiments is a potentially powerful technique for mixture analysis as mentioned in this paper.
Abstract: The addition of co-solutes to aid the separation of signals from molecules of similar size in DOSY experiments – matrix-assisted DOSY – is a potentially powerful technique for mixture analysis. The additional signals introduced by a co-solute can however greatly complicate analysis. By suitable choice of sample conditions, the NMR peaks of a surfactant matrix can be suppressed, allowing the clear resolution of molecular species according to chemistry and structure, without extraneous interference.
11 citations
TL;DR: In this paper, a new NMR experiment (Destruction of interfering Satellites by Perfect Echo Low-pass filtration, DISPEL) is introduced that facilitates the analysis of low-level components in high dynamic range mixtures by suppressing one-bond 13C satellite signals in 1H spectra.
Abstract: A new NMR experiment (Destruction of Interfering Satellites by Perfect Echo Low-pass filtration, DISPEL) is introduced that facilitates the analysis of low-level components in high dynamic range mixtures by suppressing one-bond 13C satellite signals in 1H spectra. Since the natural abundance of 13C is around 1.1%, these satellites appear at 0.54% of the intensity of a parent peak, mimicking and often masking impurity signals. The new experiment suppresses one-bond 13C satellite signals, with high efficiency, at negligible cost in signal-to-noise ratio, and over a wide range of one-bond coupling constants, without the need for broadband 13C decoupling.
10 citations
TL;DR: It is shown that NMR alone, using a combination of simple 19F, 1H, and DOSY experiments, can characterise both structure and kinetics of an intact reaction mixture, without the need for any physical separation.
Abstract: Stress tests form an important part of drug development, and of subsequent accreditation. Commonly the change in chemical composition over time is determined using chromatographic methods that separate the mixture components, but when structural characterization of the degradation products is required, other methods are needed. Arguably the most powerful method for determining chemical structure information is NMR spectroscopy. Here we show that NMR alone, using a combination of simple 19F, 1H, and DOSY experiments, can characterise both structure and kinetics of an intact reaction mixture, without the need for any physical separation.
7 citations
TL;DR: A new method for the analysis of low level impurities in sparsely fluorinated species allows measurement of clean high dynamic range 19F spectra, fully decoupled and free of interfering signals from 13C isotopomers.
5 citations
TL;DR: A matrix containing aqueous perfluorooctanoate micelles has the dual advantages of invisibility to 1H NMR, and interactions tuneable by adjusting the pH as discussed by the authors.
Abstract: Mixtures of species of similar sizes can be analysed with 1H NMR using diffusion-ordered spectroscopy (DOSY), by adding a co-solute with which different analytes interact to different extents (“matrix-assisted DOSY”). A matrix containing aqueous perfluorooctanoate micelles has the dual advantages of invisibility to 1H NMR, and interactions tuneable by adjusting the pH.
2 citations