Masakazu Iwasaka

Effects of pulsed magnetic fields on the light scattering property of the freezing process of aqueous solutions

The purpose of the study is to clarify the effect and mechanism of magnetic fields on freeze processes in aqueous solutions. In the present study, an ice crystal formation process in biological aqueous solutions under pulsed train magnetic fields (PMF) of up to 325 T/s at 6.5 mT was observed. The pulsed magnetic field generators were set in a freezer, which controlled the temperature between 10C and −30 °C. During ice formation in the aqueous solution, disk-like ice crystal domains appeared, and the PMF-exposure exhibited a vibration of floating objects in the induced electric field directions under the cooled condition when the pulsed train frequency was changed between 10 and 17 Hz. In the freezing process of the aqueous solution with NaCl, the scattered light transmission of the ion containing the aqueous solution increased in the early phase of freezing, and then began to decrease during the late phase when the ice coagulation proceeded. The PMF exposure enhanced the light-scattering increase and decr...

Biaxial Alignment Control of Guanine Crystals by Diamagnetic Orientation

The present study provides evidence that a kind of nucleic acid base crystal, guanine crystal, shows a distinct magnetic orientation. Under the condition where the guanine crystal boards were lying on the glass surface due to gravity, the boards gradually oriented their length to the applied horizontal magnetic fields of 400 mT. On the other hand, the vertical magnetic fields parallel to Earths gravity caused their width to be oriented along the applied magnetic fields. Moreover, combining both vertical and horizontal magnetic fields produced a rapid alignment of the length to the horizontal magnetic fields.

Effects of static magnetic fields on light scattering in red chromatophore of goldfish scale

Light scattering in a guanine crystal plate of goldfish scales was observed with and without static magnetic field exposure. Under a microscopic image with dark-field-illumination, the structural color of the scale by guanine plates was observed, and isolated chromatophores showed a twinkling which was the intermittent light scattering of the light from the side. The light scattering was quenched by static magnetic fields of more than 0.26 tesla (T). The quenching was reversibly occurred when the applied external magnetic fields were changed between ambient fields and 5 T. The quenched light scattering did not improve when the magnetic field was decreased from 5 to 0.3 T. It recovered to the original twinkling state about one minute after reaching an ambient geomagnetic field level. The mechanism of the quenched light scattering was speculated to be concerned with the possible magnetic orientation of guanine crystal plates, which were sustained by protein fibers in the red chromatophore. The diamagnetic c...

Magnetic Control of the Light Reflection Anisotropy in a Biogenic Guanine Microcrystal Platelet

Bioinspired but static optical devices such as lenses, retarders, and reflectors have had a significant impact on the designs of many man-made optical technologies. However, while numerous adaptive and flexible optical mechanisms are found throughout the animal kingdom, highly desirable biomimetic copies of these remarkable smart systems remain, in many cases, a distant dream. Many aquatic animals have evolved highly efficient reflectors based on multilayer stacks of the crystallized nucleic acid base guanine. With exceptional levels of spectral and intensity control, these reflectors represent an interesting design pathway towards controllable micromirror structures. Here we show that individual guanine crystals, with dimensions of 5 μm × 20 μm × 70 nm, can be magnetically controlled to act as individual micromirrors. By applying magnetic fields of 500 mT, the reflectivity of these crystals can be switched off and on for the change in reflectivity. Overall, the use of guanine represents a novel design scheme for a highly efficient and controllable synthetic organic micromirror array.

Effect of 10-T magnetic fields on structural colors in guanine crystals of fish scales

This work reports the magnetically modulated structural colors in the chromatophore of goldfish scales under static magnetic fields up to 10 T. A fiber optic system for spectroscopy measurements and a CCD microscope were set in the horizontal bore of a 10-T superconducting magnet. One leaf of a fish scale was set in a glass chamber, exposed to visible light from its side direction, and then static magnetic fields were applied perpendicular to the surface of the scale. In addition, an optical fiber for spectroscopy was directed perpendicular to the surface. During the magnetic field sweep-up, the aggregate of guanine thin plates partially showed a rapid light quenching under 0.26 to 2 T; however, most of the thin plates continued to scatter the side-light and showed changing iridescence, which was displayed individually by each guanine plate. For example, an aggregate in the chromatophore exhibited a dynamic change in structural color from white-green to dark blue when the magnetic fields changed from 2 to...

Magnetic-field parallel motion of living cells

We discovered that the motion of adherent cells was influenced by strong static magnetic fields and was parallel to the magnetic fields. A real-time observation of living cells in the presence of magnetic fields inside the bore of a superconducting magnet was performed by using a charge-coupled device camera with a monozoom lens. Fibroblastlike cells (MC3T3-E1) were cultured and observed by a video microscope system during magnetic-field exposures at 8T. During the exposure, most cells showed a back-and-forth motion along the direction of the magnetic field. Specifically, the direction of cell extension immediately after cell division was parallel to the magnetic field. Cytoskeletons inside the cells were oriented in parallel with the magnetic fields, and introduced a cell motion parallel with the magnetic field. Our experiments showed that living cells consisting of diamagnetic materials had their motion restricted by the direction of the applied magnetic field.

Changes in the bioluminescence of firefly under pulsed and static magnetic fields

The effects of a pulsed train magnetic field (PMF) and 10-T order of static magnetic fields on firefly bioluminescence were investigated on two species, Luciola cruciata and Luciola lateralis. Strong static magnetic field exposure experiments were carried out with a time-resolved spectroscopy, and the firefly bioluminescence spectrum showed a redshift in the range of 540–580nm when the firefly emitted pulses under the 10-T magnetic field. Separately from this effect, a transient decrease in the firefly’s emission intensity was observed right after being exposed to the static magnetic fields of up to 10 T. On the other hand, the utilized PMFs stimulated and enhanced the bioluminescence of Luciola cruciata. The PMF with 250–325 T/s at 1.3–10 Hz increased both the firefly’s pulsed density and frequency. It was speculated that the magnetically induced current inside the firefly affected its nervous system or the photochemical processes in the light producing organ, while the diamagnetic torque forces, which w...

Field-flow fractionation of nucleic acids and proteins under large-scale gradient magnetic fields

For the purpose of developing techniques for separating biological macromolecules, the present study reports a magnetic chromatography system employing high performance liquid chromatography and superconducting magnets of 14 and 5T. We observed chromatograms of catalase and albumin, which were eluded from columns that were exposed to magnetic fields of up to 14T with a maximum gradient of 90T∕m. Without the magnetic fields, the chromatograms of the macromolecules showed a clear peak, while the chromatograms changed to have separated peaks for the same molecules after exposure to gradient magnetic fields. When the chromatocolumn was placed so the magnetic forces were opposite to the direction of flow, the albumin molecules separated into two groups. In addition, the chromatograms of catalase exposed to the magnetic fields indicated that the retention times of the two kinds of magnetically separated catalase were relatively changed if the column-field configuration was changed. Probably, the balance of para...

Magnetic control of the inclination of biogenic guanine crystals fixed on a substrate

In the present study, we describe the fabrication and manipulation of a micro-mirror system similar to the iridophores of neon tetra that allow microstructural light control. Biogenic guanine crystals as micro-mirrors were adhered to a glass substrate with flexible DNA joints under a vertical magnetic field of 480 mT. We then observed the movement of the micro-mirrors under sub-Tesla horizontal magnetic fields. Under ambient fields, the orientation of the guanine micro-mirrors did not change. Appling a horizontal magnetic field of approximately 400 mT generated by an electromagnet induced motion and width changes of the guanine micro-mirrors, which were observed by an optical microscope. However, the inclination of the micro-mirrors recovered upon removal of the magnetic field. The developed guanine micro-mirrors on a glass substrate demonstrate the remote control of microstructural diamagnetic materials, and may show promise for use as an underwater microactuator for microfluidic systems.

Magnetic Rotation of Monosodium Urate and Urinary Tract Stones for Clinical Treatment Applications

In recent years, diseases such as gout and urinary tract calculi, caused by crystals in vivo, are rapidly increasing due to excess intake of alcohol, salt, and so forth. Crystals causing gout are compounds of uric acid with sodium in the blood, which are called monosodium urate (MSU) crystals. On the other hand, urinary tract calculus is caused by calcium oxalate crystal. In this paper, we focused on the behaviors of MSU crystals and oxalic acid crystals under magnetic fields of several hundreds of mT (Tesla), and developed a method for new medical treatments by using a magnetic field. MSU crystals and oxalic acid crystals were prepared by a recrystallization from the aqueous solution. We observed these crystals using a charge-coupled device microscope under horizontal magnetic fields (maximum of 500 mT). While the magnetic fields were applied, the MSU crystals were oriented by the magnetic fields. In addition, oxalic acid crystals were oriented perpendicularly to the magnetic field. The dynamic rotation of MSU crystal was observed quantitatively by measuring the time course of the lightscattering intensities of the MSU suspension. The results show that the diamagnetic anisotropy in the MSU crystals controlled the rotational responses. As a possible medical application, a remote control of the MSU crystals and oxalic acid crystals in living body by the magnetic fields is proposed.