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Hydrogen bonding plays an important role in forming higher-order structures of peptides, polypeptides and proteins. Accordingly, the nature of the hydrogen bond has been widely studied by various spectroscopic methods. High-resolution NMR spectroscopy has been used as one of the most powerful methods for obtaining useful information on the details of the hydrogen-bonded structure.

Most recently, the concept of an NMR chemical shift map has been used to characterize the conformation of synthetic polypeptides and the conformation of any specified amino acid residues of proteins. Here, we are concerned with the chemical shift map as established by a theoretical approach and experimental approach. The amino acid residues except for the proline amino acid residue have the freedom of internal rotation about the two consecutive bonds, NH-C_αHR and C_αHR-CO bonds, where R is the side chain. These torsional angles are defined by Φ and Ψ, respectively. It is very convenient to represent the chemical shift of the amino acid residue as a function of the torsional angles (Φ, Ψ), because the conformation-dependent chemical shift can be obtained and then the conformation can be determined through the chemical shift value. This is the so-called “chemical shift contour map” or “chemical shift map.” This has similar significance to the Ramachandran map for the conformational energy of amino acid residues.

The NMR chemical shift is available from practically every conventional NMR experiment. In contrast to X-ray diffraction it is mainly caused by the density distribution of the valence electrons, hence it contains genuine information about the valence structure of the molecular system. High-resolution solid-state investigations on crystalline systems revealed a considerable dependence of the chemical shift on the 3D arrangement of the atoms and on their packing within the unit cell [1]. In many cases, an asymmetric content of the unit cell could be deduced from NMR line splittings. The point group symmetry of the molecule under study is frequently reflected within the NMR spectra and especially within the chemical shift tensors [2]. It was demonstrated by Taulelle [3] that even the complete space group could be deduced from NMR results.

One of the reasons for difficulties in explaining indirect nuclear spin-spin coupling constants is that this phenomenon has no analogs in classical physics. The main driving force for inducing nuclear spin-spin couplings in molecules is not electromagnetic interactions but the Pauli’s exclusion principle, operating between electrons with the same spin. It was demonstrated that Fermi correlation, due to the Pauli’s exclusion principle, can be considered to be the mechanism whereby distant atoms communicate with each other [1]. The indirect nuclear spin-spin coupling is described by the form of J _ MN I _ M · I _ N in which I _ M and I _ N are the nondimensional nuclear spin vectors, and J _ MN is called an isotropic nuclear spin-spin coupling constant [2,3]. J _ MN has the units of hertz (2π rad/s) Unlike the direct interaction of magnetic dipoles, an energy of this sort of nuclear spin-spin coupling does not average out to zero when the molecules are rotating, so its effect still remains in the spectra of liquids. This fact indicates that the indirect nuclear spin-spin coupling comes from an indirect coupling mechanism via the electrons in the molecule. The indirect coupling mechanism between nuclear spins will be considered in the next section.

Recently, much attention has been paid to silks from textile engineers to polymer chemists and biomedical scientists. The silk fibers produced by silkworms or spiders are the nature’s most highly engineered structural materials with combinations of strength and toughness not found in today’s man-made materials [1]. In addition, there are many kinds of silks from silkworms and spiders with different structures and properties.

An application of field gradient attaches a spatial information in NMR signal, therefore, it can produce a spatial distribution of nuclei, that is, NMR imaging [1,2]. When two field gradients for the diphase and rephrase applied, the NMR signal decays due to the displacement of nucleus during the time between two field gradients [3,4]. This gives the diffusion coefficient for Fickian diffusion in free space and the space size for a spatially restricted diffusion [5]. Recently, the field gradient is used for the selection of desired coherence pathway by rephasing the desired coherence and dephasing the undesired coherence [6]. In this chapter, these three important uses of field gradient are described.

Self-diffusion is the random translational motion of molecules driven by their internal kinetic energy [1]. Translational diffusion and rotational diffusion can be distinguished.

In this contribution, radio frequency and field gradient pulse sequences for the encoding of position, velocity, and acceleration will be described and explained. The applicability of the techniques will be demonstrated by presenting experimentally obtained velocity and acceleration maps of fluid flow in artificial pore spaces. Porous model objects fabricated on the basis of random percolation clusters are taken as a paradigm for networks in any sort of natural or technical pores or channel complexes. Numerically obtained velocity and acceleration maps will be compared to the experimental data to test the reliability of the methods.

An application of NMR spectroscopy for biomedical area is most clearly embodied as MRI, a diagnostic imaging tool, where the information obtained by NMR is presented in a visualized image. Signal intensity, more often, T _1 and T _2, of H_2O signal in ^1H NMR is utilized for the construction of image in 2-dimensional space, as the so-called slice. To acquire data along the direction of chemical shift, it requires further elaborated time in addition to the mea- surement of MRI data. This is the major reason why the MR spectroscopic imaging is not widely accepted in clin- ical situation. Furthermore, MR images are sometimes obscured with overlapping images generated by separated signals, so-called “chemical shift artifact.” In order to circumvent this bias, it is necessary to employ a technique to enhance the sensitivity of the detection of NMR signal and also to shorten the measurement time by a fast scan technique in MRI. In this section a unique, however, an important area of NMR application, which will lead to the future NMR technology, the so called, molecular imaging (MI) in the near future is discussed.

In 1973 Paul Lauterbur proposed the use of magnetic field gradients in order to “tell exactly where an NMR signal came from” [1]. The name he coined for the technique, zeutmatography , is derived from the Greek word for “joining together”: to join the magnetic field gradient and the corresponding radiofrequency in a nuclear magnetic resonance (NMR) experiment. This connection allowed the encoding of spatial information in NMR spectra. The use of magnetic field gradients to separate the resonant frequencies corresponding to different spatial slices led to the development of NMR imaging (NMRI) or, in current language, magnetic resonance imaging (MRI). In the last 25 years, NMRI has blossomed into an essential diagnostic procedure in medicine that provides clear images of previously hidden anatomic parts. Applications of NMRI to Materials Science and other important disciplines, although not as dramatic as the medical applications, are steadily developing [2]. The wonderful story on the discovery of NMRI has been told recently [3].