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Gareth A. Morris - One of the best experts on this subject based on the ideXlab platform.

  • Matrix-assisted Diffusion-Ordered NMR Spectroscopy with an invisible, tuneable matrix
    RSC Advances, 2017
    Co-Authors: A. Hernandez-cid, Ralph W. Adams, Mathias Nilsson, Robert Evans, M. Piekarska, Gareth A. Morris
    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.

  • Ultrahigh-Resolution Diffusion-Ordered Spectroscopy
    Angewandte Chemie (International ed. in English), 2016
    Co-Authors: Mohammadali Foroozandeh, Gareth A. Morris, Laura Castañar, Lucas G. Martins, Davy Sinnaeve, Guilherme Dal Poggetto, Cláudio F. Tormena, Ralph W. Adams, Mathias Nilsson
    Abstract:

    Diffusion-Ordered Spectroscopy (DOSY) is an effective method for the analysis of intact mixtures, but the quality of results is critically limited by resolution in the NMR dimension. A new experiment integrating diffusion weighting into the PSYCHE method for pure shift NMR Spectroscopy allows DOSY spectra to be measured with ultrahigh NMR resolution at improved sensitivity.

  • Matrix‐assisted diffusion‐ordered Spectroscopy: choosing a matrix
    Magnetic resonance in chemistry : MRC, 2016
    Co-Authors: Nilce V. Gramosa, Gareth A. Morris, Ralph W. Adams, Nágila M. S. P. Ricardo, Mathias Nilsson
    Abstract:

    Diffusion-Ordered Spectroscopy (DOSY) is an important technique for separating the NMR signals of the components in a mixture, and relies on differences in diffusion coefficient. Standard DOSY experiments therefore struggle when the components of a mixture are of similar size, and hence diffuse at similar rates. Fortunately, the diffusion coefficients of solutes can be manipulated by changing the matrix in which they diffuse, using matrix components that interact differentially with them, a technique known as matrix-assisted DOSY. In the present investigation, we evaluate the performance of a number of new, previously used, and mixed matrices with an informative test mixture: the three positional isomers of dihydroxybenzene. The aim of this work is to present the matrix-assisted DOSY user with information about the potential utility of a set of matrices (and combinations of matrices), including ionic and non-ionic surfactants, complexing agents, polymers, and mixed solvents. A variety of matrices improved the diffusion resolution of the signals of the test system, with the best separation achieved by mixed micelles of sodium dodecyl sulfate and cetyl trimethylammonium bromide. The use of mixed matrices offers great potential for the analyst to tailor the matrix to a particular sample under study. © 2016 The Authors Magnetic Resonance in Chemistry Published by John Wiley & Sons, Ltd.

  • Very broadband Diffusion-Ordered NMR Spectroscopy: (19)F DOSY.
    Chemical communications (Cambridge England), 2016
    Co-Authors: Jane Power, Mohammadali Foroozandeh, Ralph W. Adams, Mathias Nilsson, Pinelopi Moutzouri, Steven R. Coombes, Andrew R. Phillips, Gareth A. Morris
    Abstract:

    A new pulse sequence, CHORUS Oneshot, allows measurements of Diffusion-Ordered Spectroscopy (DOSY) spectra over the full chemical shift range of (19)F for the first time. Swept-frequency pulses are used to give very broadband excitation; the sequence is a prototype for a large family of very broadband liquid state NMR methods.

  • Unmixing the NMR spectra of similar species – vive la différence
    Chemical communications (Cambridge England), 2013
    Co-Authors: Adam A. Colbourne, Gareth A. Morris, Sebastian Meier, Mathias Nilsson
    Abstract:

    Diffusion-Ordered Spectroscopy (DOSY) is one of the most powerful methods for intact mixture analysis by NMR. However, the separation of overlapped spectra by current DOSY methods typically requires a minimum of 30% difference in diffusion coefficient. Here we present a new algorithm (OUTSCORE) that can improve the situation by almost an order of magnitude, allowing the unmixing of severely overlapped species of similar size, by combining least squares fitting with cross-talk minimisation, maximising spectral difference.

Mathias Nilsson - One of the best experts on this subject based on the ideXlab platform.

  • Matrix-assisted Diffusion-Ordered NMR Spectroscopy with an invisible, tuneable matrix
    RSC Advances, 2017
    Co-Authors: A. Hernandez-cid, Ralph W. Adams, Mathias Nilsson, Robert Evans, M. Piekarska, Gareth A. Morris
    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.

  • Ultrahigh-Resolution Diffusion-Ordered Spectroscopy
    Angewandte Chemie (International ed. in English), 2016
    Co-Authors: Mohammadali Foroozandeh, Gareth A. Morris, Laura Castañar, Lucas G. Martins, Davy Sinnaeve, Guilherme Dal Poggetto, Cláudio F. Tormena, Ralph W. Adams, Mathias Nilsson
    Abstract:

    Diffusion-Ordered Spectroscopy (DOSY) is an effective method for the analysis of intact mixtures, but the quality of results is critically limited by resolution in the NMR dimension. A new experiment integrating diffusion weighting into the PSYCHE method for pure shift NMR Spectroscopy allows DOSY spectra to be measured with ultrahigh NMR resolution at improved sensitivity.

  • Matrix‐assisted diffusion‐ordered Spectroscopy: choosing a matrix
    Magnetic resonance in chemistry : MRC, 2016
    Co-Authors: Nilce V. Gramosa, Gareth A. Morris, Ralph W. Adams, Nágila M. S. P. Ricardo, Mathias Nilsson
    Abstract:

    Diffusion-Ordered Spectroscopy (DOSY) is an important technique for separating the NMR signals of the components in a mixture, and relies on differences in diffusion coefficient. Standard DOSY experiments therefore struggle when the components of a mixture are of similar size, and hence diffuse at similar rates. Fortunately, the diffusion coefficients of solutes can be manipulated by changing the matrix in which they diffuse, using matrix components that interact differentially with them, a technique known as matrix-assisted DOSY. In the present investigation, we evaluate the performance of a number of new, previously used, and mixed matrices with an informative test mixture: the three positional isomers of dihydroxybenzene. The aim of this work is to present the matrix-assisted DOSY user with information about the potential utility of a set of matrices (and combinations of matrices), including ionic and non-ionic surfactants, complexing agents, polymers, and mixed solvents. A variety of matrices improved the diffusion resolution of the signals of the test system, with the best separation achieved by mixed micelles of sodium dodecyl sulfate and cetyl trimethylammonium bromide. The use of mixed matrices offers great potential for the analyst to tailor the matrix to a particular sample under study. © 2016 The Authors Magnetic Resonance in Chemistry Published by John Wiley & Sons, Ltd.

  • Very broadband Diffusion-Ordered NMR Spectroscopy: (19)F DOSY.
    Chemical communications (Cambridge England), 2016
    Co-Authors: Jane Power, Mohammadali Foroozandeh, Ralph W. Adams, Mathias Nilsson, Pinelopi Moutzouri, Steven R. Coombes, Andrew R. Phillips, Gareth A. Morris
    Abstract:

    A new pulse sequence, CHORUS Oneshot, allows measurements of Diffusion-Ordered Spectroscopy (DOSY) spectra over the full chemical shift range of (19)F for the first time. Swept-frequency pulses are used to give very broadband excitation; the sequence is a prototype for a large family of very broadband liquid state NMR methods.

  • Unmixing the NMR spectra of similar species – vive la différence
    Chemical communications (Cambridge England), 2013
    Co-Authors: Adam A. Colbourne, Gareth A. Morris, Sebastian Meier, Mathias Nilsson
    Abstract:

    Diffusion-Ordered Spectroscopy (DOSY) is one of the most powerful methods for intact mixture analysis by NMR. However, the separation of overlapped spectra by current DOSY methods typically requires a minimum of 30% difference in diffusion coefficient. Here we present a new algorithm (OUTSCORE) that can improve the situation by almost an order of magnitude, allowing the unmixing of severely overlapped species of similar size, by combining least squares fitting with cross-talk minimisation, maximising spectral difference.

Myriam Malet-martino - One of the best experts on this subject based on the ideXlab platform.

  • Diffusion-Ordered Spectroscopy on a benchtop spectrometer for drug analysis.
    Journal of pharmaceutical and biomedical analysis, 2018
    Co-Authors: Gaëtan Assemat, Boris Gouilleux, Dylan Bouillaud, Jonathan Farjon, Véronique Gilard, Patrick Giraudeau, Myriam Malet-martino
    Abstract:

    Abstract The first reported two-dimensional Diffusion-Ordered Spectroscopy (DOSY) experiments were recorded at low field (LF) on a benchtop NMR spectrometer using the BPP-STE-LED (bipolar pulse pair-stimulated echo sequence with a longitudinal eddy current delay) pulse sequence which limits phase anomalies and baseline discrepancies. A LF DOSY map was first obtained from a solution of a model pharmaceutical formulation containing a macromolecule and an active pharmaceutical ingredient. It revealed a clear separation between the components of the mixture and gave apparent diffusion coefficients (ADC) values consistent with those measured from the reference high field experiment. LF DOSY was then applied to a real esomeprazole medicine and several gradient sampling schemes (linear, exponential and semi-gaussian (SG)) were compared. With a pulsed field gradient range of 4–70%, the most reliable results were given by the SG ramp. The resulting LF DOSY map obtained after 2.84 h of acquisition confirmed that the diffusion dimension is of prime interest to facilitate the assignment of overcrowded LF spectra although relevant ADC values could not be obtained in part of the spectrum with highly overlapped signals.

  • Pulsed-field gradient nuclear magnetic resonance measurements (PFG NMR) for diffusion ordered Spectroscopy (DOSY) mapping
    The Analyst, 2017
    Co-Authors: Guilhem Pagès, Véronique Gilard, Robert Martino, Myriam Malet-martino
    Abstract:

    While NMR is the most used analytical method for determining the molecular structure of isolated chemical entities, small compounds as well as macromolecules, its capability of analysing complex mixtures is less known. The advent of Diffusion Ordered Spectroscopy (DOSY) NMR has made diffusion experiments popular, enabling diffusion coefficients to be routinely measured and used to characterize chemical systems in solution. Indeed, since the translational diffusion coefficients of molecular species reflect their effective sizes and shapes, DOSY NMR allows the separation of the chemical entities present in multicomponent systems and, as in all diffusion NMR experiments, provides information on their intermolecular interactions as well as on their size and shape. The main aim of this review is to present an overview of the DOSY NMR mapping and its applications. The paper starts with a brief introduction to pulsed-field gradient (PFG) NMR and then focuses on the methodological procedures that can be used to perform good diffusion data acquisition and to obtain good-quality DOSY maps. The second part describes, through selected literature examples, different applications of DOSY NMR to demonstrate the potential of the method for (i) unravelling the components of complex matrices comprising pharmaceuticals, dietary supplements, foods and beverages, and biological extracts, and (ii) probing intermolecular interactions and evaluating association constants between different hosts and guests, as well as estimating the sizes and molecular weights of molecular species.

  • Pulsed Field Gradient NMR with Sigmoid Shape Gradient Sampling To Produce More Detailed Diffusion Ordered Spectroscopy Maps of Real Complex Mixtures: Examples with Medicine Analysis.
    Analytical chemistry, 2016
    Co-Authors: Guilhem Pagès, Véronique Gilard, Alice Bonny, Myriam Malet-martino
    Abstract:

    NMR diffusion measurements are based on signal attenuation. In the case of complex mixtures for which some molecules are diffusing quickly while others are significantly slower, it is challenging to obtain a diffusion ordered Spectroscopy (DOSY)-type 2D map giving reliable information on all molecules. In this paper, we propose a new gradient sampling approach based on a sigmoid shape allowing the acquisition of a significant number of points for both the fast and slow diffusing molecules. We applied this new gradient sampling strategy to deformulate two medicines whose composition was known (Esomeprazole) or unknown (Mebendazole). PFG NMR associated with a sigmoid gradient ramp is an exciting strategy to study drugs as a whole, i.e., the active ingredient(s) and excipients.

Ritu Barthwal - One of the best experts on this subject based on the ideXlab platform.

  • Studies on the interaction of adriamycin with d-(TGATCA)2 by proton nuclear magnetic resonance Spectroscopy, time-resolved fluorescence measurement, diffusion ordered Spectroscopy followed by structural refinement using restrained molecular dynamics
    Journal of Molecular Structure, 2009
    Co-Authors: Prashansa Agrawal, Sudhir Kumar Barthwal, Girjesh Govil, Ritu Barthwal
    Abstract:

    Abstract Adriamycin is one of the most potent anticancer anthracycline drug having aromatic chromophore and an amino sugar moiety. We report here the solution structure of 2:1 adriamycin–d-(TGATCA) 2 complex which has been determined using restrained molecular dynamics. Sequential NOE (nuclear Overhauser effect) connectivities between T1pG2 and C5pA6 steps are not observed on the intercalation of the drug chromophore at these base pair steps. Presence of several other intermolecular NOEs, that is, T1CH 3 7H, T1CH 3 10eqH and C5H6 4OCH 3 corroborate the same. The specificity of interaction arises from the O -glycosidic dihedral bond C7 O7 C1′ C2′ (133°), positioning of NH 3 + moiety in minor groove, conformation of ring A and daunosamine sugar. Besides this, diffusion ordered Spectroscopy (DOSY) studies prove the formation of complex and time-resolved fluorescence measurement studies provide evidence for shortening of decay time on complex formation. The nonspecific interactions as well as those essential for molecular basis of drug action are discussed along with the specificity of interactions in the drug–DNA complex, which is responsible for the anticancer action of the drug.

  • Studies on self-aggregation of anthracycline drugs by restrained molecular dynamics approach using nuclear magnetic resonance Spectroscopy supported by absorption, fluorescence, diffusion ordered Spectroscopy and mass spectrometry
    European journal of medicinal chemistry, 2008
    Co-Authors: Prashansa Agrawal, Sudhir Kumar Barthwal, Ritu Barthwal
    Abstract:

    Self-association, a process that competes with binding to DNA and formation of hetero-complexes, is studied in anticancer drugs 4'-epiadriamycin, adriamycin and daunomycin by proton nuclear magnetic resonance Spectroscopy. The 2D nuclear Overhauser enhancement spectra yield several intra-molecular and inter-molecular inter-proton connectivities suggesting specific stacking patterns of aromatic chromophores in parallel and anti-parallel orientation. Absorption, emission and diffusion ordered Spectroscopy demonstrate the formation of self-aggregates. Electron spray ionization mass spectrometry gives a direct proof of the presence of dimer and absence of higher aggregates. The restrained molecular dynamics simulations show the structural differences between drugs, which have been correlated to the biological action. A clear evidence of reduced cardiotoxicity by 4'-epiadriamycin, as compared to daunomycin and adriamycin, is demonstrated by mass spectrometry data.

Stefano Caldarelli - One of the best experts on this subject based on the ideXlab platform.

  • Combined maximum-quantum and DOSY 3D experiments provide enhanced resolution for small molecules in mixtures
    Magnetic Resonance in Chemistry, 2017
    Co-Authors: G N Manjunatha Reddy, Mehdi Yemloul, Stefano Caldarelli
    Abstract:

    We illustrate here as the combination of high-order maximum-quantum (MaxQ) and Diffusion-Ordered Spectroscopy (DOSY) NMR experiments in a 3D layout allows superior resolution for crowded NMR spectra. Non-uniform sampling (NUS) allows compressing the experimental time effectively to reasonable durations. Because diffusion effects were encoded within multiple-quantum co-herences, increased sensitivity to magnetic field gradients is observed, requiring compensation for convection effects. The experiment was demonstrated on the spectra of a mix of small polyaromatic molecules. Specifically, in the case analyzed, the experiment provided an extreme simplification through the MaxQDOSY-MaxQ projection plane that presents one peak per molecule.

  • Effective processing of pulse field gradient NMR of mixtures by blind source separation.
    Analytical Chemistry, 2013
    Co-Authors: Ichrak Toumi, Bruno Torrésani, Stefano Caldarelli
    Abstract:

    NMR diffusometry and its flagship layout, Diffusion-Ordered Spectroscopy (DOSY), are versatile for studying mixtures of bioorganic and synthetic molecules, but a limiting factor of its applicability is the requirement of a mathematical treatment capable of distinguishing molecules with similar spectra or diffusion constants. We present here a processing strategy for DOSY, a synergy of two high-performance blind source separation (BSS) techniques: non-negative matrix factorization (NMF) using additional sparse conditioning (SC), and the JADE (joint approximate diagonalization of eigenmatrices) declination of independent component analysis (ICA). While the first approach has an intrinsic affinity for NMR data, the latter one can be orders of magnitude computationally faster and can be used to simplify the parametrization of the former.

  • Determination of Labile Chiral Supramolecular Ion Pairs by Chromatographic NMR Spectroscopy
    Angewandte Chemie (International ed. in English), 2013
    Co-Authors: G. N. Manjunatha Reddy, Rafael Ballesteros‐garrido, Jérôme Lacour, Stefano Caldarelli
    Abstract:

    Chiral recognition: Silica-enhanced NMR diffusometry can distinguish the signals of diastereoisomeric mixtures of supramolecular ion pairs (see picture; DOSY=Diffusion-Ordered Spectroscopy). The experiment has a shorter timescale than liquid chromatography, thus allowing an easier characterization of species that are even configurationally labile on the minutes timescale.