Dr. Nobuko I. Wakayama Profile

Dr. Nobuko I. Wakayama

at AIST

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Proceedings Article | 25 October 2002 Paper

Effect of a strong magnetic field on protein crystal growth

Nobuko Wakayama, L. Wang, M. Ataka

Proceedings Volume 4813, (2002) https://doi.org/10.1117/12.450135

KEYWORDS: Blood, Liquids, Molecules, X-ray diffraction, Crystallography, Superconductors, Convection, Proteins, Magnetism, Crystals

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Recently, a superconducting magnet has been used to obtain better quality protein crystals. It is possible to reduce effective gravity and damp natural convection by applying a vertical magnetic field gradient to cause an upward magnetization (Kelvin) force. When protein crystals (snake muscle fructose-1,6-bisphosphatase) were formed in 0.7-0.8 g, their resolutions of X-ray diffraction were improved by 30% compared with those formed outside the magnet. On the other hand, in a uniform field of 10 T which did not cause an upward force, the improvement of the quality of orthorhombic lysozyme crystals was found. In this paper, besides through the upward magnetization force, we studied how a strong magnetic field damps natural convection and influences the crystal quality. First, we discussed the damping of natural convection by Lorentz force, and concluded it almost negligible because Hartman number is about 3.5 for the typical protein crystal formation experiments. Second, we studied the magnetic effect on the viscosity of protein solutions and found that the viscosity increases under 10 T when the solution contains suspended small crystals. Numerical simulations showed that the viscosity increase causes the damping of natural convection during protein crystal growth. Furthermore, the effect of magnetic orientation of suspended crystals on the crystal quality was also discussed. These types of magnetic effect will occur both in gradient and uniform magnetic fields. If we use these kinds of magnetic effects efficiently, it will be possible to improve the crystal quality.

Proceedings Article | 6 July 1999 Paper

Control of bubbles in fluids by using magnetic buoyancy forces

Nobuko Wakayama

Proceedings Volume 3792, (1999) https://doi.org/10.1117/12.351268

KEYWORDS: Magnetism, Microfluidics, Liquids, Convection, Chemical reactions, Platinum, Cameras, Bioalcohols, Video, Oxygen

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Magnetic force, i.e., magnetization force is body force and the function of density, and it is possible to induce buoyancy and convection similarly to the gravitational one. Magnetization force under 1D magnetic field gradient is generally shown by the product of density (p), mass magnetic susceptibility (x_g), magnetic field strength (H) and its gradient (dH/dy). Several experiments to control bubbles by using magnetic buoyancy forces were conducted under microgravity as follows: (1) Magnetic transport of bubbles: In pure water and glycerol/water mixture which are diamagnetic, the magnetic buoyancy force caused by a strong permanent magnet could transport bubbles toward a stronger magnetic field and to fix bubbles at the maximum point of magnetic strength. The transporting velocity was found to decrease with decreasing the radius of bubbles and increasing the viscosity. (2) Collision and fusion of two bubbles: It is almost impossible to observe the collision of bubbles clearly on the earth. the technique of magnetic control of bubbles nd microgravity condition made this observation possible. (3) Magnetic support of chemical reaction to produce bubbles (2H₂O₂→O₂+2H₂O on Pt catalyst). When small O₂ bubbles were removed from the surface of catalyst by magnetic buoyancy force, the decomposition reaction was observe to continue smoothly even under microgravity. On the other hand, in the absence of the magnet, the reaction was observed to stop under microgravity. Thus, the present study suggest the potential of using magnetic buoyancy forces to control bubbles in space experiments.

Proceedings Article | 6 July 1999 Paper

Use of magnetic force to control convection

Nobuko Wakayama, Jianwei Qi, Akira Yabe

Proceedings Volume 3792, (1999) https://doi.org/10.1117/12.351299

KEYWORDS: Magnetism, Convection, Crystals, Fermium, Proteins, Liquids, Numerical simulations, Water, Computer simulations, Superconductors

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Because magnetization force is body force, it is possible to induce convection and buoyancy driven flows. A vertical magnetization force can modify the vertical acceleration and quench natural convection. The effect of horizontal and vertical magnetization forces on natural convection is studied. We present numerical simulations of the velocity and temperature distributions of a nonconducting fluid heated from below in the presence of an imposed, nonuniform magnetic field, generated with a solenoid-type magnet. The vertically placed magnet induces horizontal and vertical magnetic forces due to the gradient of magnetic strength, and the horizontal force is found to play an important to damp natural convection. When an imposed magnetic field of strength H₀ in the middle of the magnet, is less than a critical value, H_0c, the damping effect increases with increasing H₀. For H₀ > H_0c, natural convection is completely replaced by convection induced by the magnetic field. These results were discussed, comparing either the effect of vertical forces. Our results indicate a novel method to control convection of nonconducting fluids, especially in crystal formation processes.

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