Monday, June 02, 2008

Joel's Literature Update

Sensitive NMR Sensors detect Antibodies to Influenza
Isaac Koh, Rui Hong, Ralph Weissleder, Lee Josephson
Angwandte (2008)47, 4119.
Catching the flu: Magnetic particle aggregation has been used to provide a highly sensitive, NMR-based sensor for detecting antibodies to an influenza virus. To achieve high sensitivity, a homogeneous magnetic field (H) was employed to enhance antibody-based cross-linking between particles suspended in solution (see scheme; T2: change in the transverse relaxation time).

Temperature-Controlled Molecular Depolarization Gates in Nuclear Magnetic Resonance
Leif Schröder, Lana Chavez, Tyler Meldrum, Monica Smith, Thomas J. Lowery, David E. Wemmer, Alexander Pines
Angwandte (2008)47, 4316.
Down the drain: Cryptophane cages in combination with selective radiofrequency spin labeling can be used as molecular transpletor units for transferring depletion of spin polarization from a hyperpolarized source spin ensemble to a drain ensemble. The flow of nuclei through the gate is adjustable by the ambient temperature, thereby enabling controlled consumption of hyperpolarization (see scheme).

Broadband Dipolar Recoupling for Magnetization Transfer in Solid-State NMR Correlation Spectroscopy

Luminita Duma, Daniel Abergel, Fabien Ferrage, Philippe Pelupessy, Piotr Tekely, Geoffrey Bodenhausen
ChemPhysChem(2008)9, 1104.
Efficient recoupling: A new experimental procedure using a broadband variant of rotary resonance recoupling (B2R3, see figure) improves 13C-13C transfer of magnetization in biological molecules. The robustness of the method, combined with its simplicity, results in improved structural analysis of crystalline and non-crystalline systems.

Regioselective H/D Exchange at the Side-Chain of Ethylbenzene on Dealuminated Zeolite H-Y Studied by In Situ MAS NMR-UV/Vis Spectroscopy
Jun Huang, Yijiao Jiang, V. R. Reddy Marthala, Yean Sang Ooi, Michael Hunger
ChemPhysChem(2008)9, 1107.
Regioselective H/D exchange at the side-chain methyl group of ethylbenzene on dealuminated zeolite H-Y and formation of carbenium ions are observed for the first time by the novel in situ pulsed-flow 1H MAS NMR-UV/Vis technique. Hydride abstraction on Lewis acid sites lead to the formation carbenium ions which are protonated following Markovnikov's rule (see scheme).

High temperature NMR study of the local structure of molten LaF3–AF (A = Li, Na, K and Rb) mixtures
Anne-Laure Rollet, Stéphanie Godier and Catherine Bessada
The local structures of molten lanthanum alkali fluoride binaries have been studied using HT NMR technique. The chemical shifts of 19F, 23Na and 139La in solid and in liquid have been compared for AF (A = alkali) and LaF3. In pure molten alkali fluorides, the polarisability of anion–cation pairs appears to be a key parameter to depict the observed evolution of 19F chemical shifts. The influence of the composition has also been studied by measuring the chemical shifts in molten LaF3–AF as a function of LaF3 concentration. A strong influence of the alkali influence is observed. The coordination number of lanthanum is decreased versus AF amount all the more since the alkali atomic number is high. Moreover, the more polarisable the alkali, the less bridging fluorines between the LaFx units.

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