Hyperpolarization techniques

Using the OPENCORE spectrometer, a research group led by M. Kitagawa in Osaka have developed an experimental setup for dynamic nuclear polarization (DNP) using electron spins in the photo-excited triplet state. This nuclear hyperpolarization technique, called hereafter triplet DNP,... 

In this seetion, I review the methodological work on hyperpolarization, if it also refers to relaxation phenomena. Three types of hyperpolarization technology will he covered. We start with the dynamic nuclear polarization (DNP) and continue with hyperpolarization through para-hydrogen (PHIP) and through optically pumped xenon. Koptyug presented reeently a review of hyperpolarization techniques applied to en matie proeesses and covering the first two approaches. 

Finally, spin hyperpolarization techniques for obtaining spin polarizations exceeding the Boltzman limit by several orders of magnimde like optical polarization, para hydrogen induced hyperpolarization, or dynamic nuclear polarization (DNP) are subject of intense research. In the last section we will highlight recent break-throughs and latest contributions of DNP in the field of biomolecular solid-state NMR spectroscopy. 

The recent success of DNP as a hyperpolarization technique in solid-state NMR spectroscopy is mainly due to the following developments [210],... 

A major limitation for NMR spectroscopy is the intrinsically low sensitivity due to the rather unfavorable Boltzmann distribution for nuclear spins at thermal equilibrium. Thus, considerable effort in magnetic resonance spectroscopy is made towards sensitivity enhancement by hyperpolarization techniques, such as optical polarization, para-hydrogen-induced polarization enhancement, and dynamic nuclear polarization (DNP), a method which exploits the magnetization of unpaired electrons in stable radicals or transition metals to enhance nuclear polarization beyond the Boltzmann limit. In the chapter Dynamic Nuclear Hyperpolarization in Liquids, the fundamental theory for different polarization transfer... 

Avermectin-sensitive sites in A. mum have been identified on pharyngeal muscle (Martin, 1996) using a two-micropipette current-clamp technique (Fig. 21.13A). Glutamate and avermectins produce hyperpolarization and an increase in Cl conductance when either bath-applied or pressure-ejected on to the pharyngeal preparation (Fig. 21.13B,C). These observations establish that one site of action of the avermectins is the pharyngeal muscle of nematodes and that the avermectins can inhibit feeding in nematodes. 

This initial system, though not optimized for this particular application in medicine, has since been superseded by more appropriate systems with other choices of the components [48]. Finally, possible applications for using selectively hyperpolarized fluorine-containing molecules as contrast agents for medical imaging techniques appear especially attractive however, this subject matter is discussed elsewhere [50]. 

Mahyar et al. (2006) report the effect of the fruit essential oil of cumin on the epileptiform activity induced by pentylenetetrazol (PTZ), using the intracellular technique. The results demonstrate that extracellular application of the essential oil of cumin (1 and 3%) dramatically decreases the frequency of spontaneous activity induced by PTZ in a time- and concentration-dependent manner. In addition, it showed protection against PTZ-induced epileptic activity by increasing the duration and decreasing the amplitude of after-hyperpolarization potential (AHP) following the action potential, the peak of action potential and inhibition of the firing rate. 

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