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Realization of Three-Dimensional Imaging of Chirality Domains Using Synchrotron Radiation (Press Release)

Release Date
27 Jun, 2013
  • BL39XU (Magnetic Materials)
- Distinguishing the difference in “handedness”, a decisive factor for the functions of substances, by an X-ray approach -

Graduate School of Frontier Sciences, The University of Tokyo
Aoyama Gakuin University
Japan Synchrotron Radiation Research Institute (JASRI)

Key points of this research
• Development of an X-ray microscope system for visualizing the handedness of chiral substances using synchrotron radiation at SPring-8
• Three-dimensional observation of chirality domains in crystalline substances with micron resolution
• Breakthrough toward establishing the regulation scheme of the crystallization of materials with the same handedness

A joint research group comprising RIKEN (President, Ryoji Noyori), the University of Tokyo (President, Junichi Hamada), Aoyama Gakuin University (President, Ken-ichi Semba), and JASRI (President, Yoshiharu Doi) developed a technique for visualizing chirality domains in crystalline substances with micron resolution using synchrotron radiation X-rays. The group was led by Hiroyuki Ohsumi (senior research scientist) and Masaki Takata (Group Director) from the Spin Order Research Team, Quantum Order Research Group, RIKEN SPring-8 Center (Director, Tetsuya Ishikawa); Taka-hisa Arima (professor) from the Graduate School of Frontier Sciences, the University of Tokyo (also the leader of the Spin Order Research Team); and Yusuke Kousaka (postdoctoral researcher) and Jun Akimitsu (professor) from College of Science and Engineering, Aoyama Gakuin University.

“Chiral” originates from the Greek word for “hand”, and chiral substances refer to substances that are not identical to their mirror image, similarly to human hands. Various sugars and amino acids that constitute human bodies are chiral substances and require strict matching of handedness in normal metabolism. For example, monosodium glutamate naturally found in kelp is a left-handed substance responsible for umami (i.e. fifth taste). In artificial synthesis, however, bitter right-handed monosodium glutamate is also produced. Therefore, only the substances with the desired handedness must be separated and purified for use in medicines, pharmaceuticals, and food additives. However, reagents and filters used for separation and purification are also made of chiral substances, that is, purification for purifiers is recursively required, which takes enormous labor and cost. The labor and cost of separation and purification can be greatly reduced if high-quality crystals of chiral substances with the same handedness can be grown. Thus, the development of a technique that enables such crystal growth is much needed. The conventional method described in Fig. 1 can be used to determine the fraction of left- and right-handed substances in aqueous solution but cannot tell which part of crystal is left- or right-handed. The understanding of the mechanisms behind such crystal growth is also limited.

To solve this problem, the joint research group has worked on the development of an X-ray microscope system at SPring-8[1] for visualizing the difference in the handedness of substances. In this research, the group succeeded in three-dimensionally observing the distribution of left- and right-handed domains in the chiral substance cesium copper chloride (CsCuCl3).

The achievements of this research will contribute to the understanding of the mechanism behind the crystal growth of chiral substances, leading to markedly improved technologies for producing medicines, pharmaceuticals, food additives, and even spintronics materials. In addition, new knowledge may be gained on the origin of the homochirality of life[2], which has long been a mystery of living organisms.

The results of this research were published online in the German scientific journal Angewandte Chemie International Edition on 1 July 2013 prior to the paper version.

"Three-Dimensional Near-Surface Imaging of Chirality Domains with Circularly Polarized X-rays"
H. Ohsumi, A. Tokuda, S. Takeshita, M. Takata, M. Suzuki, N. Kawamura, Y. Kousaka,J.Akimitsu, and T. Arima
Angewandte Chemie International Edition, 2013


Fig. 1	General method of chiral discrimination
Fig. 1 General method of chiral discrimination

The fraction of left- and right-handed chiral substances in aqueous solution can be determined by guiding light so that it passes through the aqueous solution and measuring the degree of rotation of the plane of polarization. This method cannot be applied to chiral substances that lose their chirality* in aqueous solution or solid substances that are opaque. Even if a solid substance is transparent, that is, it can transmit light, it is considered very difficult to determine the fraction of left- and right-handed chiral substances in the solid from the rotation angle of the plane of polarization because the rotation angle is greatly affected by other factors (linear dichroism and linear birefringence).

Fig. 2	Scanning X-ray microscope developed in this research
Fig. 2 Scanning X-ray microscope developed in this research

Linearly polarized X-rays are converted to circularly polarized ones by a quarter wave plate and focused down to the micron level by Kirkpatrick-Baez (K-B) mirrors. In the developed microscope, these circularly polarized X-ray microbeams are used to scan a sample, enabling the magnified observation of chirality domains in crystalline substances.

[1] SPring-8

SPring-8 is a synchrotron radiation facility that provides the world’s highest-brilliance synchrotron radiation. It is owned by RIKEN and located in Harima Science Park City, Hyogo Prefecture, Japan. JASRI is responsible for the operation, management, and promotion of the use of SPring-8. The name “SPring-8” is derived from “Super Photon ring-8 GeV”. When the direction of the electron beams accelerated to nearly the speed of light is changed by magnets, electromagnetic waves are emitted in the tangential direction; these waves are synchrotron radiation. When the electron beam has a higher energy and the change in the traveling direction is large, synchrotron radiation contains shorter-wavelength lights such as X-rays. In particular, the following three facilities are known as the third-generation large synchrotron facilities: SPring-8 in Japan, the Advanced Photon Source (APS) in the USA, and the European Synchrotron Radiation Facility (ESRF) in France. Because the ring at SPring-8 enables an electron acceleration energy of 8 giga-electronvolts to be generated, synchrotron radiation in a wide range of wavelengths can be obtained including far-infrared light, visible light, vacuum ultraviolet light, soft X-rays, and hard X-rays. SPring-8 is used by researchers both in Japan and overseas for joint research in various fields such as materials science, earth science, life science, environmental science, and industrial applications.

[2] The homochirality of life
Sugars and amino acids that constitute living organisms on earth exist exclusively as one of two enantiomers.

[3] Circular polarization
There is a mirror-image relationship between left- and right circularly polarized light.

* Chirality
The property of a substance having a nonsuperimposable mirror image.

For more information, please contact:
  Ph.D. Takahisa Arima (RIKEN)

  Dr. Hiroyuki Ohsumi (RIKEN)

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