http://struct.pc.uec.ac.jp/
Research on the structure of materials;
investigations of correlations between
the structure and properties of materials
Masanori YASUI Laboratory
Summary of Research
X-Ray Analysis of Crystal Structure, A Key Piece of Information on a
Substance
Masanori YASUI
Our laboratory analyzes the crystal structures of substances using X-ray diffractometers. Our major theme is to observe molecules with X-rays, a mission that generally
involves investigations of the correlation between the structure of a substance and
its physical properties, based on the analysis of atomic and molecular arrangements
and intermolecular interactions. Minute particles on the scale of atoms and molecules
cannot be observed directly. In contrast to everyday objects, examinations by visible
light tell us nothing. We must use X-rays, which have far shorter wavelengths than
visible light, to study the spectra of scattered (diffracted) X-rays, observing atoms and
molecules indirectly. This is what X-ray diffractometers allow us to do.
X-ray diffraction (XRD) is a phenomenon generated by the interactions of X-rays and
electrons. The most basic data obtained via XRD analysis is information on the distribution of electrons within the crystal, or electron density distribution. Since interactions between atoms/molecules are mediated by electrons, we can identify the forces
acting between atoms within a single molecule (intramolecular interactions), as well as
those between molecules in the crystal (molecular interactions), and strengths of the
forces to make quantitative assessments.
This information on crystal structures is fundamental, because the structure of a substance determines its physical properties. Determining structures allows us to determine physical properties.
Studying the Mechanisms That Generate Physical Properties
From the above, it follows that if we can identify which atomic/molecular interactions
are responsible for a given physical property (i.e., the mechanism that gives rise to
these physical properties), we should be able to enhance or suppress certain properties by intensifying or weakening the interactions responsible. One theme of research
at our laboratory is to perform such structural analysis of substances and to investigate the mechanisms giving rise to these physical properties. In short, we undertake
basic research on the structure and physical properties of substances.
Advantages
State-of-the-Art In-House X-Ray Diffractometer
Our laboratory has many years of experience in analyzing organic crystals, from which
we have stockpiled extensive experience and expertise on analytical technologies. We
currently own and operate a state-of-the-art X-ray diffractometer at the Coordinated
Center for UEC Research Facilities.
Keywords
X-ray crystallographic analysis, electron
density distribution analysis, molecular
interaction, structural phase transition
of organic crystals, protein, interactions
between proteins and pigment molecule
Affiliations
Member
OPAL-RING
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Crystallographic Society of Japan;
Chemical Society of Japan
Masanori Yasui, Associate
professor
Our key strength lies in an integration of technologies, experience, expertise, and advanced instruments, which makes possible various XRD experiments.
High-Speed, High-Precision Structural Analysis Capabilities
Our X-ray diffractometer confers the capacity to observe and analyze the crystal
structure of a substance within one or two days, provided we have access to a 0.2-0.3
mm cube of a single crystal of sufficient quality.
Here lies the rub: The key difficulty associated with XRD analysis is preparing single
crystals of sufficient quality. In this area, too, we offer guidance and advice grounded
in experience. We are confident we can respond in constructive ways to requests to
determine the structure of a certain functional material, thereby helping to enhance
functions in a manner you find satisfactory.
Nanotechnology and Materials
At the Coordinated Center for UEC Research Facilities, we
also have access to an instrument capable of performing simultaneous differential scanning calorimetric and powder XRD
measurements, enabling detailed investigations of structural
changes with changing temperatures.
Future Prospects
Clarifying the Nature of Interactions Between
Proteins and Various Molecules
We are currently pursuing two major research focuses. In the
first, which involves interactions between proteins and various molecules, we have initiated structural analysis studies of
proteins. As a first step in the research, we are investigating the
optical behavior exhibited by optically-inactive pigment molecules when they interact with proteins.
We believe identifying and understanding the mechanism underlying the interactions of the protein-pigment molecules will
open the door to new protein applications, in addition to those
based on the well-known functions of enzyme reaction of proteins. The large molecular weight of proteins makes it difficult
to produce single protein crystals that satisfy the quality criteria
for XRD analysis. We must explore effective protein crystallization methods before embarking on structural analysis.
Performing High-Precision Electron Density
Distribution Analysis of Various Molecules
Our second current theme involves more precise electron
density analysis of various molecules. Powerful new structural
analysis software has emerged during the past decade, accelerating growth in both the number of researchers and overall
research activity. While interest in this area remains relatively
low in Japan, this field of study promises an abundance of interesting discoveries.
We recently acquired an instrument that will make it possible
to lower the temperature of a sample to -230 °C, allowing us to
perform electron density distribution analysis at ultra-low temperatures. We have no doubts that the results of this research
will prove both interesting and significant.
A CCD single-crystal X-ray diffractometer
A powder X-ray diffractometer (for simultaneous differential scanning calorimetry)
122
OPAL-RING