Japan Atomic Energy Research Institute (JAERI) and the Institute of Physical and Chemical Research (RIKEN) have jointly been constructing a third generation, hard X-ray synchrotron radiation facility, SPring-8, in Harima, Hyogo. We expect the first X-rays in February, 1997 and ten public beamlines will be subjected to scientific program by the middle of FY1997. In the paper, the outline of the SPring-8 Project will described. In the rest, the scientific program which may be promoted in the third generation synchrotron radiation sources is discussed in terms of key words, expressing characteristics of SPring-8.
Various improvements have been brought into X-ray solution scattering by the use of synchrotron radiation: time-resolved solution X-ray scattering became feasible; the application of solution scattering have been extended to non-native conformations of proteins. SPring-8 will brings the further improvements: to carry out experiments in very short times; to obtain very accurate data from very low angle to quite high angle. These factors should change the quality of investigation. The combined use of solution scattering with SPring-8 and molecular dynamics simulation will open the way to deduce solution structures and/or structural changes upon ligand binding based on crystal structures. Elucidation of the folding mechanism through the structure of non-native conformations are also expected. We will be able to carry out single-shot time-resolved measurements of msec time resolution at SPring-8 with a new high sensitive detector.
Although the crystal structure of myosin subfragment-1 and actin has been known for some years, molecular mechanism of force production is still unknown. This is a common situation with many other protein molecules: it is hard to elucidate the mechanism of dynamic function of of a protein from crystal structure. Time-resolved X-ray diffraction studies in a microsecond range may help us solve this fundamental problem in molecular biophysics.
With the use of extremely intense synchrotron radiation sources it has become possible to collect good quality x-ray diffraction data for protein crystals on a subsecond time-scale. This has led to the development of time-resolved protein crystallography, where the main objective is to determine the structures of short-lived intermediates during enzymatic reactions by monitoring the time dependence of the x-ray intensities. Furthermore, utilization of single-bunch mode in the 3rd generation synchrotron source enables us to shorten the time scale of the time-resolved protein crystallography to nano-or picosecond order. Possibility of nano-or picosecond protein crystallography in Accumlation Ring (KEK) and SPring-8 is disscussed.
Bio-Crystallography (MIR-OAS) beamline is under construction at SPring-8 for routine analyses of macromolecular crystal structures by the multiple isomorphous replacement phasing with optimized anomalous scattering. It aims to present a high-quality electron density map of target macromolecules within one beamtime.
Time-resolved XAFS spectroscopy is suitable for probing the active-site structures of the reaction intermediates of metalloproteins. Various types of the technique including energy-dispersive, repetitive-excitation, Q-scan, rapid-flow and rapid-freeze methods are described, together with the future prospects of their applications to biological samples.
Principle of XAFS (X-ray Absorption Fine Structure) was briefly reviewed in relation to its application to metalloproteins in biological systems. Our experiences in PF of KEK for these ten years were also summarized toward the 3rd generation photon ring.
A brief description of the present state of optics for the x-ray microscope is made. X-ray optical elements, detectors and several types of x-ray microscopes are introduced. Prospects of new developments of x-ray microscopes with SPring-8 are mentioned.
Imaging x-ray microscopy and its capability of observing live biospecimens are reviewed. Wet biospecimens can be monitored with the resolution of 19nm. Phase contrast method may open the capability of observing live cells.
X-ray microscopy of a single whole cell is briefly reviewed with respect to spectromicroscopy and holography. A resonance peak in XANES (X-ray absorption near edge structure) will be useful for imaging elements and molecules. X-ray holography is a different approach to the development of X-ray microscopy and may be applicable to three dimensional imaging of a cell.
Harima Science Garden City is being constructed by Hyogo Prefectural Government in the south-west part in Hyogo Prefecture. The area under development is 960 ha. This city will include research institutes, academic institutions, industrial factories and houses, and the amenity for the people to live in this city is aimed. The SPring-8 is the biggest institute and Faculty of Science, Himeji Institute of Technology was located in order to collaborate with the SPring-8. The many research institutes will be constructed in this city by industrial companies, and one of them, Harima Research Institute of Sumitomo Electric Industry has already started its activities. The total concept to construct Harima Science Garden City is described.
Mitubishi-kasei Institute of Life Sciences, Machida 194 and Graduate Program in Biological Sciences, Hokkaido University, Faculty of Science, Sapporo 060. Massive neuronal death occurring during development (naturally-occurring neuronal death) plays a pivotal role in sculpting the nervous system. The nuclear type of cell death, one of the three types of cell death found in vivo, shares several features common to apoptosis. Using cultured sympathetic neurons and neuronal PC12 cells. molecular nature of this mechanism has been extensively explored. This review summarizes recent advances in this study along with those of regulatory mechanisims including the role of intracellular Ca2+. The idea that neurons have an intrinsic suiside program has led us to hypothesize that collapse of homeostasis during senescence may activate this program as well. Proposed mechansim of neuronal death in Alzheimers disease is very intriguing in support of this notion.