Nobuhiro Miura

The structure of water determined by microwave dielectric study on water mixtures with glucose, polysaccharides, and L-ascorbic acid

Dielectric relaxation measurements over an extremely wide frequency region from 1 MHz to 20 GHz were performed on water mixtures with glucose, polysaccharides, and L‐xylo ascorbic acid by the use of time domain reflectometry. For mixtures of polysaccharides bigger than maltotriose, two relaxation peaks were definitely observed. The high frequency relaxation is the water relaxation and the low frequency one is due to orientation of polysaccharide molecules. In the case of glucose, only one relaxation peak could be observed. It is shown that a hexagonal cluster in the lattice of ice can be replaced easily by the glucose molecule, where the lattice is distorted slightly, but stabilized by several hydrogen bonds between the glucose molecule and the lattice. Although the cluster can be replaced by the L‐ascorbic acid molecule too, the lattice cannot be kept stable. Its water mixture shows two relaxation peaks clearly. It is suggested that water has a structure of the distorted lattice of ice. Fluctuation of th...

The structure of water and methanol in p-dioxane as determined by microwave dielectric spectroscopy

Dielectric measurements were performed on water–p‐dioxane and methanol–p‐dioxane mixtures using time domain reflectometry over the frequency range 0.1–10 GHz. In the case of water–p‐dioxane mixtures, the relaxation strength normalized by the number of water molecules per unit volume is independent of the molar fraction of water xW if xW 0.66. However, the relaxation time of pure methanol is too large for clusters consisting of three molecules. It is suggested that the chainlike clusters form network structures.

High order and local structure of water determined by microwave dielectric study

Water mixture with tert‐butanol shows two critical points if the logarithm of dielectric relaxation time is plotted against the mol fraction of water XW. One point at XW∼0.97 is suggested to indicate the break point of a high order structure of water and another point XW=0.83 is that of a local structure. Existence of the high order structure was already indicated by a recent dielectric study on water–glucose mixture. The structure is a less ordered lattice of ordinary ice type. It is also shown that water mixture with treharose or maltose exhibits one relaxation peak as well as the glucose mixture. This manifests that the diameter of the water cluster is nearly the same as the length of treharose or maltose, at least, smaller than that of maltotriose which shows two relaxation peaks. The critical point XW∼0.97 corresponds to about 30 water molecules included in the high order structure, which is very reasonable to compare the result of the glucose mixture.

Molecular dynamics of hinge-bending motion of IgG vanishing with hydrolysis by papain.

We have performed dielectric relaxation measurements via a time domain reflectometry (TDR) method to study dynamic behaviors of the segmental flexibility of immunoglobulin G (IgG) in aqueous solution without antigen binding. In general, an intermediate relaxation process due to bound water is observed around 100 MHz at 25 degrees C for common proteins between two relaxation processes due to overall rotation and reorientation of free water. However, the intermediate process observed around 6 MHz for IgG was due to both bound water and hinge-bending motion. The apparent activation energy of 33 kJ/mol was larger than 27 kJ/mol for only bound water, and the relaxation strength was about five times as large as expected for bound water. The shape of the relaxation curve was very broad and asymmetric. These characteristic differences arising from the hinge-bending motion of IgG disappeared for fragments decomposed from IgG hydrolyzed by papain, since the hinge-bending motion did not exist in this case. We have separated the relaxation processes due to hinge-bending motion and bound water for IgG and obtained the Fab-Fab angle of IgG as about 130 degrees by Kirkwoods correlation parameter and the activation energy of 34 kJ/mol for hinge-bending motion.

Dielectric relaxation of the Kohlrausch‐type in aqueous polymer solution

Micro‐Brownian motion of polymer chain in aqueous solution was clearly observed at first for poly(vinyl pyrrolidone) as a dielectric relaxation by a time domain reflectometry method which covers an extremely wide frequency region from 100 kHz–10 GHz. The dielectric response function observed is of the Kohlrausch‐type as expected for the chain motion, φ(t)=exp[−(t/τl)β l]. Concentration dependence of the relaxation time τl at 25 °C is given by log τl=−9.77−1.35/(cd−2.07), where cd is the polymer concentration (g/cc), and that of the coupling parameter βl is given by βl=−0.182cd+0.662. These dependences are characteristic features of the relaxation caused by the chain motion.

Free water content and monitoring of healing processes of skin burns studied by microwave dielectric spectroscopy in vivo.

We have investigated the dielectric properties of human skin in vivo at frequencies up to 10 GHz using a time-domain reflectometry method with open-ended coaxial probes. Since gamma-dispersion results from the reorientation of free water molecules, the free water content of skin is quantitatively determined by dielectric measurements. The free water content of finger skin increased by about 10% after soaking in 37 degrees C water for 30 min, and it systematically decreased again through the drying process, as expected. Thus this analytical method has been applied to the study of skin burns. The free water content of burned human cheek skin due to hydrofluoric acid was significantly lower than that of normal skin, and the burned skin recovered through the healing process. In the case of a human hand skin burn due to heat, although the free water content was almost the same as that of normal skin at the beginning, it decreased during the healing process for the first 10 days, then began to increase. Although the number of test subjects was one for each experiment, it was shown that free water content is a good indicator for evaluating skin health and can be well monitored by dielectric spectroscopy.

Intermolecular vibrational study in liquid water and ice by using far infrared spectroscopy with synchrotron radiation of MIRRORCLE 20.

Far infrared absorption measurements for distilled water and ice Ih were performed in the frequency range from 20 cm(-1) to 1000 cm(-1) with Fourier Transform Infrared Spectrometer (FTIR) utilizing SR of a portable synchrotron. Four vibrational bands were separated from measured spectra in liquid water. We found that a peak frequency of 40±1 cm(-1) did not depend on the temperature in a range between 10.0°C and 70.0°C; however, any low energy excitation modes were not observed in the ice spectrum. It is concluded that this band is caused by collective vibrations specific to the dynamical structure in liquid water.

Globule-coil transition of denatured globular protein investigated by a microwave dielectric technique.

A mechanism for the gel-glass transition of denatured globular protein has been explained from the viewpoint of the globule-coil transition with microwave dielectric measurements using a time domain reflectometry (TDR) method. Boiled egg white, which is an aqueous gel of egg white prepared by heat treatment at 100 degrees C, becomes a glass on drying. In the gel state, the relaxation processes corresponding to the orientation of bulk water and the micro-Brownian motion of peptide chains of denatured protein were observed around 10 GHz and 10 MHz, respectively. When the gel-glass transition occurred, the relaxation strength for bulk water decreased rapidly as evaporation and breaking of water structure occurred. Simultaneously, the relaxation strength for micro-Brownian motion increased abruptly, as the structure of globular protein varied from globule state to coiled state. It is considered that the protein molecule spreads out and takes up a coiled state by reductions of hydrophobic and hydrophilic interactions of the globular protein. These reductions occur through a decrease in the amount of water.

Time domain reflectometry: measurement of free water in normal lung and pulmonary edema

The free water content of lung tissue was investigated by dielectric spectroscopy in normal lungs and in pulmonary edema induced by oleic acid in rats. The dielectric relaxation in a frequency range of 107 to 1010 Hz was measured with the time domain reflectometry method at 25°C. Three dielectric relaxation processes were analyzed for the lung tissue. A high-frequency process around 10 GHz was attributed to the orientation of free water molecules based on the relaxation time [log τh (in s) = -11.03]. The dielectric strength (Δε) of this high-frequency peak (Δεh) should reflect the amount of free water in the tissue. Because the measured Δεh depended on the air content of the lung samples, the value of Δεh was corrected for the air content of each sample as determined by the point-counting method in the area where the time domain reflectometry data were obtained. The lungs of rats that received an injection of oleic acid had a significantly increased free water content [(Δεh of lung/Δε of pure water) × density of pure water] compared with that in the normal lung (0.76 vs. 0.59 g/cm3). These results indicate that free water occupies ∼60% of the total volume of normal lung tissue and that there is an increase in free water in pulmonary edema.

Hinge-bending deformation of enzyme observed by microwave dielectric measurement

A dielectric relaxation peak due to an intramolecular motion in the active site of trypsin was first observed in aqueous solution below the freezing temperature of bulk water by a time domain reflectometry method. If trypsin inhibitor is added to the solution, it vanishes. It is suggested that the motion observed is a hinge-bending deformation giving rise to the enzymatic activity of trypsin, which is prohibited by linkage of the trypsin inhibitor. Relaxation time of the motion is 3 × 102 ns at − 10°C.