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As is the case for proteins, NMR methods have been applied to DNA and RNA extensively and methods for the structure determination by NMR are recently almost established [1–6]. In this section, a general view of the NMR application for DNA and RNA is shown.

In solution-state NMR, homonuclear shift correlation experiments, such as COSY and INADEQUATE, have successfully been used for signal assignment. In these experiments, correlation between spins is established via through-bond J couplings, so that each cross peak represents corresponding chemical bonding. Similar J -correlation experiments can also be applicable in solids. Due to the low resolution of ^1H resonances in the solid-state NMR, however, we use other spin-1/2 nuclei such as ^13C and ^15N, whose high resolution observation is capable in solids by the combined use of magic-angle spinning (MAS) and ^1H decoupling. Since these isotopes are rare in natural abundance, homonuclear shift-correlation experiment in solids requires a uniformly ^13C or ^15N-labeled sample. Hereafter, we examine experiments on ^13C spins, but most results can also be applied to other rare spin-1/2 nuclei (^15N, ^19Si, etc). Figure la shows a COSY pulse sequence in solids; instead of a single 90° pulse used in solution NMR, cross polarization is applied for excitation. Figure lb shows a ^13C-COSY contour spectrum of [u-^13C,^15N]glycilisoleucine([u-^13C,^15N] Glylle).^[1] The straight lines indicate ^13C-^13C J connectivity. As exemplified by this, it is straightforward to implement J -based sequences in solid NMR. However, ^13C-COSY and/or INADEQUATE have not been popular so far. One of the reasons may be ascribed to the size of the J interaction being much smaller than those of the other spin interactions. To observe small ^13C-^13C J splitting of a few 10 Hz, line broadening due to ^13C-^13C dipolar coupling should be removed by fast MAS together with the removal of ^13C-^1H dipolar broadening by efficient ^1H decoupling. Further, the samp le-rotation angle should precisely be adjusted to the magic angle to get rid of broadening due to the anisotropic chemical-shift interaction.

Solid-state nuclear magnetic resonance (SSNMR) spectroscopy has become an important technique for studying molecular structure and dynamics of chemical and biological systems. Most successful SSNMR studies have been based on observation of magnetically dilute spin-1/2 nuclei such as ^13C,^15N,^29Si, and^31P, etc. Although oxygen is ubiquitous in organic and biological molecules, SSNMR studies for ^17O (the only NMR-active oxygen isotope) are far less common [1–4]. The scarcity of solid-state ^17O NMR studies arises from the fact that ^17O has a very low natural abundance (0.037%) and a quadrupolar nucleus (spin-5/2) with a sizable nuclear electric quadrupole moment ( eQ = -2.558 fm^2). The major obstacle of obtaining SSNMR spectra for quadrupolar nuclei such as ^17O is the large size of nuclear quadrupole interactions (typically of the order of 10^6 Hz). This is because these large quadrupole interactions make it difficult to record SSNMR spectra with sufficient spectral resolution in order to resolve chemically or crystallographically different sites.

Narrowest heteronuclear dipolar coupling spectral lines provided by the two-dimensional polarization inversion spin exchange at the magic angle (PISEMA) technique lead to the development and application of a series of multidimensional solid-state NMR methods for the structural studies of biological solids. Studies have shown that the measurement of structural and orientational constraints from uniformly labeled proteins using PISEMA is crucial, particularly in the structure determination of membrane-associated proteins. Excellent line-narrowing efficiency, high scaling factor, and performance at various magic-angle-spinning (MAS) speeds and radio frequency (rf) power are the main advantages of PISEMA. However, high rf power requirement and offset effects are the major limitations of this technique. In this chapter, these difficulties and methods to overcome them are discussed for both static and MAS experimental conditions. Experimental and simulated data to demonstrate the efficacy of newly developed PISEMA-type pulse sequences are also presented.

Rotational-echo, double-resonance (REDOR) NMR is a high-resolution, solid-state NMR experiment for measuring the dipolar coupling between a heteronuclear spin pair [1,2]. The 1/ r ^3 distance dependence of the dipolar coupling makes REDOR useful for the structural characterization of solids, and REDOR has become a valuable tool for characterizing a wide range of materials, including peptides and proteins, polymers, zeolites, guest-host systems, glasses, and more. Since the REDOR experiment is based primarily on trains of π pulses, it has mostly been used to measure dipolar couplings between pairs of spin -1/2 nuclei. Under certain conditions, however, the REDOR experiment can also make effective use of quadrupolar nuclei as structural probes.

Torsion angles in synthetic and biological solids encode important information on the backbone and side chain conformation of these molecules, and provide complementary structural restraints to distances. In the last decade, solid-state NMR spectroscopy has become a mature tool for determining molecular torsion angles [1]. The development of methods for measuring torsion angles in peptides and proteins has helped determine de novo high-resolution structures of small peptides [2–4] and solved the conformation distribution of large structural proteins [5] and synthetic polymers [6]. This review examines these torsion angle determination techniques, with a special emphasis on tensor correlation methods applied to biological solids. Both static and magic angle spinning (MAS) methods will be discussed, the former giving exquisite angular resolution, while the latter having the necessary site resolution to yield multiple angular restraints from each experiment.

The backbone structures of proteins are characterized by the secondary structure, such as α-helix, β-sheet, and turn structures [1]. Thus, backbone segments in the 3D structures can be assigned to these regular conformations. Information on the secondary structure is obtained at earlier stages of the experimental structural analysis by circular dichroism (CD), infrared absorption (IR), chemical shifts in nuclear magnetic resonance, and X-ray diffraction at low resolution [2]. The secondary structure analysis is the basis for the further detailed structural studies.

Telomeres are the ends of eukaryotic linear chromosomes consisting of repetitive G-rich sequences and telomeric repeat binding factors. In mammalian telomeres, TRF1 and TRF2 bind to double-stranded telomeric DNA consisting of TTAGGG repeats and regulate telomere length. Both contain a central TRF-homology domain and a C-terminal DNA-binding domain. We have determined the solution structures of DNA-binding domains from human TRF2 and TRF1 bound to a telomeric DNA. Both structures are very close to each other, however, small but significant differences are observed. Based on their structures, we created six mutants of the hTRF2 DNA-binding domain and the DNA-binding activities of all these DNA-binding domains could be well analyzed.

Magnetic resonance spectroscopy (MRS) has the unique ability to measure the chemical content of living tissue in the body, repeatedly and noninvasively. This permits investigations of biology and physiology in human and in animal models in vivo , in both healthy and diseased tissues. From such studies, information on tumor diagnosis and response to therapy, as well as prognostic information, has been obtained. MRS can also be used for in vitro studies of cell and tumor extracts. Now with high-resolution magic-angle spinning (HR-MAS) spectroscopy, small pieces of intact tissue (e.g. biopsies) can also be examined.

Genetically modified mice and (to a lesser degree) rats are frequently used as models for human cardiac disease. Since the genomes of both mouse and humans have now been fully analyzed, major research programs are currently underway worldwide to investigate systematically the function of specific genes by overexpression, deletion or mutation of these genes and their products in mice (e.g. [1] for review). These recent advances in gene manipulation have lead to a new era of cardiovascular research, and new animal models of cardiovascular disease are appearing at arapid rate [2–4]. The phenotypic effects introduced by these transgenic models range from the absence of any overt abnormalities to severe anatomical, functional, or metabolic malformations during development causing premature death in utero or soon after birth [5].