Nuclear magnetic resonance, proton dynamics

To detect dynamic featnres of colloidal preparations, additional methods are required. Nuclear magnetic resonance spectroscopy allows a rapid, repeatable, and noninvasive measurement of the physical parameters of lipid matrices withont sample preparation (e.g., dilution of the probe) [26,27]. Decreased lipid mobility resnlts in a remarkable broadening of the signals of lipid protons, which allows the differentiation of SLN and supercooled melts. Because of the different chemical shifts, it is possible to attribute the nuclear magnetic resonance signal to particnlar molecnles or their segments. 

The application of nuclear magnetic resonance (NMR) spectroscopy to polymer systems has contributed to significant advances in understanding of their structure and dynamical properties at the molecular level. From the analytical point of view, NMR spectroscopy is particularly suitable for a determination of the polymer structure by direct observation of the protons and carbons in different structural moieties. However, until the mid-1970s the application of this technique was limited to polymer solutions and to some elastomers in the solid state with a relatively high degree of the molecular mobility which allows the observation of the motionally narrowed absorption signals. 

Proton and deuteron nuclear magnetic resonance techniques are applied in solid hydrate research both for determining the hydrogen positions and for studying the dynamic processes of the water molecules ". ... 

The descriptions of the structure, energy, and dynamics of H-bonds continue to be a formidable task for both experimental and theoretical investigations. IR and nuclear magnetic resonance (NMR) techniques have become routine tools to analyze H-bonding interactions in various systems [1-4, 150]. The vibrational modes of molecules in the H-bonded state are affected in several ways. The proton involved in H-bonding interaction exhibits down field shift. Spectroscopic information obtained from these techniques has been used to probe H-bonding interactions. 

The dynamics of the so-called biological water molecules in the immediate vicinity of a protein have been studied using dielectric relaxation [18], proton and O NMR relaxation [19], reaction path calculation [20], and analytical statistical mechanical models [21]. While the dielectric relaxation time of ordinary water molecules is 10 ps [16], both the dielectric [18] and nuclear magnetic resonance (NMR) relaxation studies [19], indicate that near the protein surface the relaxation dynamics are bimodal with two components in the 10-ns and 10-ps time scale, respectively. The 10-ns relaxation time cannot be due to the motion of the peptide chains, which occurs in the 100-ns time scale. From the study of NMR relaxation times of " O at the protein surface, Halle et al. [19c,d] suggested dynamic exchange between the slowly rotating internal and the fast external water molecules. 

Interest in water at protein surfaces and other surfaces arises from a desire to understand structural, functional, and dynamic factors as well as their interrelationships. Nuclear magnetic resonance (NMR) spectroscopy provides both structural and dynamic information. This presentation will focus on dynamical aspects of the water-protein Interaction. In particular, the phenomenon of cross relaxation between the water and protein proton systems will be discussed and new evidence will be reported. Failure to recognize the importance of cross relaxation effects leads to incorrect conclusions about the dynamics of water at protein surfaces. 

Nuclear magnetic resonance is a powerful technique which can yield information on dynamic phenomena. Because of the lack of protons in the Nafions it is easier to study the water protons. 

Proton magnetic resonance spectroscopy and C nuclear magnetic resonance (NMR) spectroscopy have been reported to study the nature of water in hiunan SC (Foreman, 1976 Yamamura and Tezuka, 1989 Jokura et al., 1995). The H-NMR data are useful to study dynamic structural disorder of the intercellular lamellar Upid structure in the SC (Bezema etal., 1996). For further information on the use of NMR for investigating SC stmcture, refer to the review by Abraham et al. (1997). 

---