Saturday 6 August 2016

HR-MAS NMR Spectroscopy: A Practical Guide for Natural Samples

Author(s):

Hashim Farooq, Denis Courtier-Murias, Ronald Soong, Wolfgang Bermel, William M. Kingery and André J. SimpsonPages 3013-3031 (19)

Abstract:


High Resolution Magic Angle Spinning (HR-MAS) NMR spectroscopy is a versatile technique that provides high resolution NMR data on samples containing solutions, gels and swellable solids. In addition to providing structural information HR-MAS can also be used to investigate interfaces (for example organic structures at the solid-aqueous soil interface), processes such as swelling/ flocculation, kinetic transfer between gel/liquid phases, as well as conformation and molecular interactions in situ. As such, HRMAS has potential in a diversity of fields including organic, biological, environmental, and medical research. This manuscript focuses on the application of HR-MAS to intact natural samples. A range of 1D and 2D NMR experiments are reviewed and compared in terms of general performance on a range of samples. Therefore, this practical guide and review should be a useful reference and starting point for those wishing to apply HR-MAS NMR. While this article focuses on natural samples, common key 1D and 2D experiments are considered which may be of interest to readers with diverse research interests.

Keywords:

1D NMR, 2D NMR, Algae, High resolution magic angle spinning (HR-MAS), Natural samples, NMR, Soils, Worm tissue.

Affiliation:

Department of Chemistry, University of Toronto, 1265 Military Trail, Toronto, Canada, M1C 1A4.


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    Environmental Organic Photochemistry: Advances and Perspectives

    Author(s):

    Andrea Pace and Salvatore BarrecaPages 3032-3041 (10)

    Abstract:


    This review is a survey of recent advances in environment related aspects of organic photochemistry. Besides presenting general concepts, the manuscript is mainly focused on the photoreactivity of natural organic matter, and on the photochemistry of anthropogenic substances under natural light irradiation.

    Keywords:

    Environmental photochemistry, Organic photochemistry, Natural organic matter, Photocatalysis, Photodegradation, Photooxidation.

    Affiliation:

    Dipartimento di Scienze e Tecnologie Biologiche, Chimiche e Farmaceutiche, Università degli Studi di Palermo, Viale delle Scienze Ed.17 - 90128 Palermo, Italy.


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    Synthetic Routes to Methylerythritol Phosphate Pathway Intermediates and Downstream Isoprenoids

    Author(s):

    Sarah K. Jarchow-Choy, Andrew T. Koppisch and David T. FoxPages 1050-1072 (23)

    Abstract:


    Isoprenoids constitute the largest class of natural products with greater than 55,000 identified members. They play essential roles in maintaining proper cellular function leading to maintenance of human health, plant defense mechanisms against predators, and are often exploited for their beneficial properties in the pharmaceutical and nutraceutical industries. Most impressively, all known isoprenoids are derived from one of two C5-precursors, isopentenyl diphosphate (IPP) or dimethylallyl diphosphate (DMAPP). In order to study the enzyme transformations leading to the extensive structural diversity found within this class of compounds there must be access to the substrates. Sometimes, intermediates within a biological pathway can be isolated and used directly to study enzyme/pathway function. However, the primary route to most of the isoprenoid intermediates is through chemical catalysis. As such, this review provides the first exhaustive examination of synthetic routes to isoprenoid and isoprenoid precursors with particular emphasis on the syntheses of intermediates found as part of the 2C-methylerythritol 4-phosphate (MEP) pathway. In addition, representative syntheses are presented for the monoterpenes (C10), sesquiterpenes (C15), diterpenes (C20), triterpenes (C30) and tetraterpenes (C40). Finally, in some instances, the synthetic routes to substrate analogs found both within the MEP pathway and downstream isoprenoids are examined.

    Keywords:

    Enzyme mechanism, isoprenoids, terpenes, MEP pathway.

    Affiliation:

    Los Alamos National Laboratory, PO Box 1663, Bioscience Division MS M888, USA.

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      Polyelectrolyte-graphene Nanocomposites for Biosensing Applications

      Author(s):

      Dimitrios PriftisPages 1819-1827 (9)

      Abstract:


      Due to their unique structure, the optical and mechanical properties graphene and its derivatives (e.g. graphene oxide, reduced graphene oxide) have captured the attention of a constantly increasing number of scientists with regards to biomolecule sensing. This mini review focuses on one specific type of sensor, that consisting of graphene and polyelectrolytes. Polyelectrolyte-graphene nanocomposites exhibit outstanding detection capabilities by synergistically combining the characteristics of both components, outperforming traditional sensors in many cases. Characteristics and mechanistic details of the most important polyelectrolyte-graphene based sensors will be discussed in detail in addition to some current challenges and future perspectives.

      Keywords:

      Polyelectrolytes, graphene, nanocomposites, sensors, hybrid materials.

      Affiliation:

      The Institute for Molecular Engineering, University of Chicago, Chicago, IL 60637, USA.

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      Carbon Dioxide Utilization by the Five-Membered Ring Products of Cyclometalation Reactions

      Author(s):

      Iwao OmaePages 953-962 (10)

      Abstract:


      In carbon dioxide utilization by cyclometalated five-membered ring products, the following compounds are used in four types of applications:
      1. 2-Phenylpyrazole iridium compounds, pincer phosphine iridium compounds and 2-phenylimidazoline iridium compounds are used as catalysts for both formic acid production from CO2 and H2, and hydrogen production from the formic acid. This formic acid can be a useful agent for H2 production and storage for fuel cell electric vehicles.
      2. Other chemicals, e.g., dimethyl carbonate, methane, methanol and CO, are produced with dimethylaminomethylphenyltin compounds, pincer phosphine iridium compounds, pincer phosphine nickel compound and ruthenium carbene compound or 2-phenylpyridine iridium compounds, and phenylbenzothiazole iridium compounds as the catalysts for the reactions with CO2.
      3. The five-membered ring intermediates of cyclometalation reactions with the conventional substrates react with carbon dioxide to afford their many types of carboxylic acid derivatives.
      4. Carbon dioxide is easily immobilized at room temperature with immobilizing agents such as pincer phosphine nickel compounds, pincer phosphine palladium compounds, pincer N,N-dimethylaminomethyltin compounds and tris(2-pyridylthio)methane zinc compounds.

      Keywords:

      Carbon dioxide utilization, greenhouse gas, climate change, cyclometalation reactions, five-membered ring, global warming.

      Affiliation:

      Omae Research Laboratories, 335-23, Mizuno, Sayama, Saitama, 350-1317, Japan.

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