Tuesday, April 12, 2011

Bridge12 Collaborates with Agilent 
on THz Technology for DNP-NMR

Click here to read the press release by Agilent Technologies

Cambridge, Mass. – April 11, 2011 – Bridge12 Technologies, a leading provider of terahertz technology for applications in science, medicine, security and defense, today announces it has entered into an agreement with Agilent to collaborate on technology for dynamic nuclear polarization (DNP) enhanced nuclear magnetic resonance (NMR) spectroscopy. As part of the collaboration, Bridge12 will provide gyrotrons, a critical component for an emerging application known as DNP, which accelerates NMR experiments that typically require weeks to be performed in minutes.
Under the agreement, Bridge12 will provide critical terahertz components such as gyrotrons and terahertz transmission lines for DNP-NMR to be integrated with new and existing Agilent spectrometers. Where other solutions require expensive proprietary equipment, Bridge12's gyrotron can be retrofitted to existing spectrometers and requires no changes to the facility's layout.
Applying DNP to NMR experiments significantly improves measurement sensitivity for solid-state samples, reducing the duration of experiments by several orders of magnitude. Structure determination of proteins at atomic resolution by solid-state NMR (SSNMR) spectroscopy is a time-consuming, iterative process. Signal intensities are typically very small due to the very small gyromagnetic ratio of the nuclei under study, such as 1H, 2H, 13C, and 15N. However, free electrons possess a magnetic moment that is 660 times larger than that of protons. In a DNP experiment this polarization can be transferred to surrounding nuclei by radiating the sample with terahertz radiation to boost NMR signal intensities. With DNP, experiments that typically require several weeks of signal averaging can be performed in minutes. This acceleration is of great value in structural biology, pharmaceutical research and material science
“Bridge12 gyrotrons for Agilent's spectrometers are turn-key, low-maintenance, and designed specifically for the requirements of the NMR community,” says Dr. Thorsten Maly, a Bridge12 co-founder. “The joint system enables research groups to run DNP NMR experiments without requiring terahertz specialists on staff. Thus far, the scientific community has not been able to take advantage of DNP due to the lack of affordable, reliable terahertz sources. As a result of our collaboration with Agilent, we will be offering a turn-key solution to the NMR community that has far lower maintenance costs than current home-grown systems.”
Bridge12 staff will be available to answer questions at the Agilent booth at the 52nd Experimental Nuclear Magnetic Resonance Conference (ENC) held at the Asilomar Conference Center (Pacific Grove, California) from April 10th to 15th, 2011.

Monday, April 4, 2011

Solution-State Dynamic Nuclear Polarization

M. D. Lingwood et al., Solution-State Dynamic Nuclear Polarization, Annu. Rev. NMR Spec., 2011, 73, 83-126


Solution-state dynamic nuclear polarization (DNP) is an increasingly popular method of enhancing nuclear spin polarization that has many applications in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). The theory, methods and applications of DNP in the solution state using the Overhauser effect are distinctly different from those of solid-state DNP or what is known as dissolution DNP. This review discusses the theory and recent experimental advances of Overhauser DNP techniques in the solution state at various field strengths ranging from the earth's magnetic field to 9.2 T, covering the literature from 1986 to late 2010. Most of the focus in this review is on spectroscopy applications of DNP, although proton–electron double resonance imaging (PEDRI) and remotely enhanced liquids for imaging contrast (RELIC) applications are briefly covered.

Saturday, April 2, 2011

High-Field Dynamic Nuclear Polarization with High-Spin Transition Metal Ions

B. Corzilius et al., High-Field Dynamic Nuclear Polarization with High-Spin Transition  Metal Ions, 2011, JACS

We report the dynamic nuclear polarization of  1H spins in magic-angle-spinning spectra recorded at 5 T and 84 K via the solid effect using Mn2+ and Gd3+ complexes as polarizing agents. We show that the magnitude of the enhancements can be directly related to the effective line width of the central (mS = -1/2, 1/2) EPR transition. Using a Gd3+ complex with a narrow central transition EPR line width of 29 MHz, we observed amaximum enhancement of ∼13, which is comparable to previous results on the narrow-line-width trityl radical.

Dynamical nuclear polarization and confinement effects in ZnO quantum dots

P. G. Baranov et al., Dynamical nuclear polarization and confinement effects in ZnO quantum dots, Phys. Status Solidi B., 2010, 247, 1476-1479

The spatial distribution of the electronic wave function of a  shallow donor (SD) in a ZnO semiconductor quantum dots (QD’s) has been determined in the regime of quantum confinement by using the nuclear spins as probes. Hyperfine (HF) interactions as monitored by electron nuclear double resonance spectroscopy quantitatively reveal the transition from semiconductor to molecular properties upon reduction of the size of the nanoparticles. Influence of confinement effect on g-factor value of SD’s in ZnOand CdS QD’s was displayed. The almost complete dynamic nuclear polarization (DNP) of nuclear spins has been demonstrated can be achieved in ZnO QD’s by saturating the EPR transition of the SD present in the QD’s with using high-frequency at low temperatures. Polarization of 67Zn nuclear spins inZnO core and of 1Hnuclear spins in the Zn(OH)2 capping layer have been obtained which manifests itself via the creation of a hole and an antihole in the EPR absorption line of the SD in QD’s and a shift of the hole (antihole). The enhancement of the nuclear polarization opens the possibility to study semiconductor nanostructures with NMR techniques

Dynamic Nuclear Polarization Polarizer for Sterile Use Intent

J. H. Ardenkjaer-Larsen et al., Dynamic Nuclear Polarization Polarizer for Sterile Use Intent, NMR Biomed., 2011, published online.

A novel polarizer based on the dissolution-dynamic nuclear polarization (DNP) method has been designed, built and tested. The polarizer differs from those previously described by being designed with sterile use intent and being compatible with clinical use. The main features are: (1) an integral, disposable fluid path containing all pharmaceuticals constituting a sterile barrier, (2) a closed-cycle cryogenic system designed to eliminate consumption of liquid cryogens and (3) multi-sample polarization to increase throughput. The fluid path consists of a vial with the agent to be polarized, a pair of concentric inlet and outlet tubes connected to a syringe with dissolution medium and a receiver, respectively. The fluid path can operate at up to 400 K and 2.0MPa and generates volumes as high as 100 mL. An inline filter removes the amount of electron paramagnetic agent in the final product by more than 100-fold in the case of [1-13C]pyruvate. The system uses a sorption pump in conjunction with a conventional cryocooler. The system operates through cycles of pumping to low temperature and regeneration of the sorption pump. The magnet accommodates four samples at the same time. A temperature of less than 1 K was achieved for 68 h (no sample heat loads) with a liquid helium volume of 2.4 L. The regeneration of the liquid helium could be achieved in less than 10 h, and the transition to cold (< 1.2 K) was achieved in less than 90 min. A solid state polarization of 36W4% for [1-13C]pyruvic acid was obtained with only 10 mW of microwave power. The loading of a sample adds less than 50 J of heat to the helium bath by introducing the sample over 15 min. The heat load imposed on the helium bath during dissolution was less than 70 J. The measured liquid state polarization was 18W2%.

Dynamic Nuclear Polarization with Polychlorotriphenylmethyl Radicals: Supramolecular Polarization-Transfer Effects

C. Gaellieri et al., Dynamic Nuclear Polarization with Polychlorotriphenylmethyl Radicals: Supramolecular Polarization-Transfer Effects, Angew. Chem. Int. Ed., 2010, 49, 3360-3362

Polychlorinated trityl radicals (see structure: C black, Cl green, Na gray, O red) used for dynamic nuclear polarization (DNP) showed a new transfer mechanism involving quadrupolar chlorine nuclei. The observation of positive or negative enhancements, depending on the substrate, highlights the supramolecular character of the initial polarization-transfer process.