We have already introduced the research on protein structure
that uses the synchrotron radiation facility of KEK in various
ways. As explained in our introduction to the Protein 3000
Project, a national project in Japan, the three-dimensional
structure of protein can be identified mainly by using X-ray
crystallography. X-ray synchrotron radiation that is strong
and spatially focused has been used for over 20 years because
it is optimal when illuminating a protein crystal for accurate
measurement through the internal weak diffraction point
(point of changing the direction of X-ray such as reflection).
Life sciences, particularly those based on the 3-D structure
of protein have recently been activated and promoted internationally
on a large scale. In this situation, it has become difficult
to carry out the rapid measurements of large-scale crystal
or the measurement of micro crystal by use of beam line
in conventional synchrotron radiation facilities.
Today, we introduce the NW12, the beam line for the structural
biology research, created in the high-energy synchrotron
radiation ring (PF-AR: Photon Factory Advanced Ring) of
KEK synchrotron radiation facility in order to meet the
expectations. The name, NW 12, reflects the fact that it
makes use of the light source located at the 12th section
on the northwest side of PF-AR. This beam line measures
the diffraction data obtained from the exposure of X-ray
synchrotron radiation to protein crystal. The calculation
using computer of diffraction data obtained leads to the
elucidation of protein structure. For rapid measurement,
the beam line is equipped with special devices such as the
inserting light source to eliminate light that is stronger
than that of conventional synchrotron radiation and the
CCD Detector to enable to read the diffraction data rapidly.
For this, the exposure time and data recording time were
shortened and the measurement time has been cut from over
3 hours at the time using the beam line in conventional
PF to about 20 minutes.
There is only 2.2 micron or less of wobbling of the rotation
axis of crystal in NW12. Because of its very high precision,
measurement of microcrystal in even microns (a thousandth
of 1 mm) is available. With the mirror that collimates X-ray
synchrotron or the system to cool spectral structures by
using liquid nitrogen (-196), X-rays highly collimate,
leading to the experiment using the multiwavelength anomalous
dispersion (MAD) method with high precision. The MAD method
is used to find clues to the structure through the use of
the minute changes of signals that occur in the diffraction
intensity when X-ray wavelength is changed, and is a potent
structure determination method, which is difficult to carry
out without synchrotron radiation, which its variable wavelength.
Other state-of-the-art techniques, such as the X-ray shutter
that can open and close for 10 millisecond or the spectrometer
that has a variable wavelength without changing the outgoing
site of the beam, have been incorporated into NW12.
In experimental study at the end of February, the structure
of the protein called glycosyltransferases was clarified.
It was possible to obtain the diffraction data at 2.0 angstrom
resolution after measuring for only 20 minutes by using
a crystal sized approximately 30 x 30 x 100 microns. Figure
3 shows the 3-dimentional structures obtained as a result
of the structural analysis.
To carry out effectively the sequential measurement of
large-scale crystals, the process of setting the crystal
into the device should be accelerated. NW 12 is equipped
with a control system that makes these process automated
by introducing a robot. In the near future, through automating
most of the process, the mechanism will be established to
supply data immediately to researchers in structural biology.
Picture of crystals of glycosyltransferases,
which are approximately 30 x 30 x 100 microns
X-ray diffraction picture of glycosyltransferases
Each of the many spots of light, like a starry sky, has
information about the location of each atom. The 3-dimentional
structure of protein as shown in Figure 3 can be obtained
using computer-assisted analysis.
The 3-dimentional structure of glycosyltransferases
analyzed using NW12
Newly constructed NW 12 beam line for the
structural biology research in PF-AR
Boxes called "hutches" that are seen at the front
and the back of this picture hold the devices of the optical
system and the measurement devices.
magnification (60 KB)
High-speed CCD detector installed in the
Using this detector, the diffraction data as shown in Figure
2 can be obtained rapidly.
magnification (41 KB)