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Catechol O-methyltransferase (COMT) is known as an important drug-target protein in the field of Parkinson's disease. All clinically approved COMT inhibitors bring a 5-substituted-3-nitrocatechol ring as a pharmacophore, and they bind to COMT with S-adenosylmethionine (SAM) and an Mg2+ ion to form a quaternary complex (COMT/SAM/Mg2+/inhibitor). However, structural information about such quaternary complexes is only available for a few inhibitors. Here, a new crystal structure of COMT complexed with nitecapone (5), SAM and Mg2+ is revealed. Comparison of the structures of these complexes indicates that conformation of the catechol binding pocket is almost constant regardless of structure of the inhibitors. The only restriction of the side chain of inhibitors (i.e., the substituent at the 5-position of 3-nitrocatechol) seems to be that it does not make steric repulsion with COMT. However, recent crystallographic and biochemical studies suggest that COMT is a flexible protein, and its conformational flexibility seems crucial for its catalytic process. Based on this information, implications of these quaternary inhibitor complexes were investigated. Met 40 in the α2α3-loop makes atomic contacts with SAM or S-adenosylhomocysteine and the 3-position of the catechol inhibitor. This interaction seems to play a critical role in the affinity of the inhibitor and to stabilize the COMT/SAM/Mg2+/nitrocatechol inhibitor complex by fixing the flexible α2α3-loop.

Catechol O-methyltransferase (COMT) is known as an important drug-target protein in the field of Parkinson's disease. All clinically approved COMT inhibitors bring a 5-substituted-3-nitrocatechol ring as a pharmacophore, and they bind to COMT with S-adenosylmethionine (SAM) and an Mg

A novel X-ray source based on parametric X-ray radiation (PXR) has been put into practical use at the Laboratory for Electron Beam Research and Application (LEBRA), Nihon University, Japan. The PXR beam has been generated from a Si single crystal irradiated by a 100-MeV electron beam from a linac at the LEBRA. In this study, phase-contrast imaging experiments using a diffraction-enhanced imaging (DEI) method have been carried out by using the parametric X-rays at an energy of 17.5 keV. The successful images obtained by the DEI method have shown detailed inner structures of soft biological tissues more clearly as compared with those by conventional absorption radiography. Given the significant properties of the LEBRA PXR source, i.e., compact system, large X-ray beam irradiation field of approximately 80 mm in diameter and quasi-monochromaticity, the result suggests a possible construction of a compact linac-driven PXR-DEI device and application to medical diagnoses. Copyright © 2012 John Wiley & Sons, Ltd.

Raman spectroscopy is based on Raman scattering of light form molecules, and Raman spectra provide highly useful information about molecular composition and its circumstances. The micro FT-Raman spectra both of ghost cells in calcifying cystic odontogenic tumor and keratinocytes of the gingiva showed a broad beak centered around 850 cm-1.

Signaling pathways have been shown to participate in the process of Retinoic acid (RA) - induced cleft palate (CP). In our current study, the signaling molecules of GSK-3 beta, Fzd3 and beta-TrCP, which all relate with Wnt pathway, were screened from the palate tissues of the RA-induced CP in mice by the Gene-chip Technology. But, their expression pattern and level in palates during perinatal stages have not been known yet. In the studies, mRNA level of GSK-3 beta, Fzd3 and beta-TrCP were detected by quantitative real-time PCR, and showed significant difference between the Embryonic day 18 (ED18) before birth and Postnatal day 0 (PD0) after birth, as well as between the RA-induced CP and wild type during the perinatal stage, respectively. And the localization pattern of GSK-3 beta, Fzd3 and beta-TrCP proteins in palates was also characterized. Our data indicates that the Wnt signaling pathway may involve in the RA-induced cleft palate during peirnatal stage.

In the application of lasers in dentistry, there is a delicate balance between the benefits gained from laser treatment and the heat-related damage arising from laser irradiation. Hence, it is necessary to understand the different processes associated with the irradiation of lasers on dental materials. To obtain insight for the development of a safe and general-purpose laser for dentistry, the present study examines the physical effects associated with the irradiation of a near-infrared free-electron laser (FEL) on the surface of a commonly used silver dental alloy. The irradiation experiments using a 2900-nm FEL confirmed the formation of a pit in the dental alloy. The pit was formed with one macro-pulse of FEL irradiation, therefore, suggesting the possibility of efficient material processing with an FEL. Additionally, there was only a slight increase in the silver alloy temperature (less than 0.9 °C) despite the long duration of FEL irradiation, thus inferring that fixed prostheses in the oral cavity can be processed by FEL without thermal damage to the surrounding tissue. These results indicate that dental hard tissues and dental materials in the oral cavity can be safely and efficiently processed by the irradiation of a laser, which has the high repetition rate of a femtosecond laser pulse with a wavelength around 2900 nm.

Tooth enamel is composed of nano-scale, needle-like biological apatite crystallites. These crystallites constitute the enamel prisms. The generally accepted Meckel's model of arrangement of crystallites in enamel prism might be slightly revised according to the variations in tooth enamel chemical composition and structures. An x-ray diffraction method was proposed to survey the three-dimensional crystallite orientation instead of electron microscopy. Preliminary results showed clear difference in the convergence and broadening of enamel crystallite orientations of human tooth enamel. This method has high potential in analyzing partial deviation in crystallite orientation as well as easy sample preparation and operation.

Parametric X-ray (PXR) is a new type of radiography with variable monochrome wavelength and high coherent characteristics. The Laboratory for Electron Beam Research and Application (LEBRA) at Quantum Science Institute, Nihon University generated LEBRA-PXR, a system that irradiates Si crystal with electron accelerated by linear accelerator (LINAC). LEBRA-PXR is uniquely developed for world-wide application experiment. X-ray images of tooth samples were taken with flat panel detector using LEBRA-PXR. As a result, images were captured as short as 1 sec. LEBRA-PXR uses LINAC with micro-macro pulse electron beam structure. Imaging time of 1 sec is equivalent to about 0.025 msec when x-ray is converted to actual radiation exposure. The effective dose point estimates of x-rays were about 1 μ Sv/5 sec. Results show that LEBRA-PXR can be used to generate low dose x-ray imaging advocating the possibility of its application in biological studies and medical treatment.

Wavelength-tunable monochromatic Parametric x-ray (PXR) was generated at the Laboratory for Electron Beam Research and Application (LEBRA) at Nihon University. Using the LEBRA-PXR, phase contrast imaging was carried out. Phase contrast images of a kitten deciduous tooth were taken by diffraction enhanced imaging (DEI) method. The results showed that LEBRA-PXR is a high coherent x-ray and is suitable for phase contrast imaging.

Advanced applications of parametric X-ray radiation (PXR) such as energy-dispersive X-ray absorption fine structure (DXAFS) analysis and phase-contrast imaging have been developed at the Laboratory for Electron Beam Research and Application (LEBRA) of Nihon University. To improve the electron beam quality and geometrical stability of the target crystal, the cooling-water system for the linac and the PXR target was replaced with a new one capable of more precise control. As a result, the reliability of the experimental data in PXR applications, especially in X-ray imaging, has improved. The effect of the electron beam focusing on the target crystal was also investigated. The results of X-ray imaging with a long propagation distance and measurement of the time-structure of the PXR intensity suggest that the correlation between the electron beam profile and the X-ray coherence is rather complicated. It is possible that incident electrons cause some deformation of the target crystal, becoming the dominant factor restricting the quality of intense PXR.

Recently, earthworms have become a useful model for research into the immune system, and it is expected that results obtained using this model will shed light on the sophisticated vertebrate immune system and the evolution of the immune response, and additionally help identify new biomolecules with therapeutic applications. However, for earthworms to be used as a genetic model of the invertebrate immune system, basic molecular and genetic resources, such as an expressed sequence tag (EST) database, must be developed for this organism. Next-generation sequencing technologies have generated EST libraries by RNA-seq in many model species. In this study, we used Illumina RNA-sequence technology to perform a comprehensive transcriptome analysis using an RNA sample pooled from sterile-cultured Eisenia andrei. All clean reads were assembled de novo into 41,423 unigenes using the Trinity program. Using this transcriptome data, we performed BLAST analysis against the GenBank non-redundant (NR) database and obtained a total of 12,285 significant BLAST hits. Furthermore, gene ontology (GO) analysis assigned 78 unigenes to 24 immune class GO terms. In addition, we detected a unigene with high similarity to beta-1,3-glucuronyltransferase 1 (GlcAT-P), which mediates a glucuronyl transfer reaction during the biosynthesis of the carbohydrate epitope HNK-1 (human natural killer-1, also known as CD57), a marker of NK cells. The identified transcripts will be used to facilitate future research into the immune system using E. andrei.

Thermal effects produced in a laser-irradiated sample were studied by micro-X-ray diffraction and micro-Fourier transform infrared spectroscopy (FTIR). Gypsum, transformed into bassanite at 124 degrees C and into anhydrite at 147 degrees C, was used as a thermal indicator. Pit formation by a wavelength-tunable free electron laser (FEL) irradiation on the gypsum pellet maximized at a wavelength of 3.0 microm, 2 mJ/shot, and pits were not detected in those irradiated at 2.6 or 3.8 microm compared with the maximum at 3.0 microm and diminished at 2.0 or 4.0 microm in the human tooth case. Micro-X-ray diffraction and micro-FTIR did not reveal any appreciable bassanite or anhydrite in the irradiated regions. From the laser ablation viewpoint, these results allow the FEL ablation to be considered as plasma or evaporative ones. This study indicated that the micro-pulse of laser was effective to prevent thermal damages of laser irradiation.

A parametric X-ray radiation (PXR) generator system was constructed in 2001 in a dedicated beamline connected to the 125 MeV electron linac of the Laboratory for Electron Beam Research and Application at Nihon University. This generator system consists of two perfect-silicon-crystal plates mounted on precisely moving mechanical setup to achieve a wide tunability. The experimental operation of the PXR generator started early in 2004; X-rays were first observed through this device in April 2004. Application studies using the PXR beam from a 100 MeV electron beam have been conducted since July 2004. Preliminary results suggest the possibility of applying the PXR to advanced X-ray imaging and to the measurement of X-ray absorption fine structure.

Parametric X-rays (PXR) are a new type of X-ray that are generated by crystal-electron interactions. The Laboratory for Electron Beam Research and Application (LEBRA) at Nihon University generates PXR using a double-crystal system generating electrons from a 100-MeV class LINAC. LEBRA-PXR has potential for use as a wavelength tunable, ultra-high bright X-ray source with a macro-/micro-pulse structure. LEBRA-PXR has an energy-dispersion in the horizontal axis, assumed to be 0.2% in the experimental window, but can be used as monochromatic X-ray source for diffraction using a simple slit-system. A diffraction experiment was successfully carried out by applying an 11 keV, or 1.1273 A, LEBRA-PXR. Near-perfect crystals, such as graphite used for a monochromator showed sharp diffraction peaks. Clear, transparent mineral quartz and fluorapatite crystals also showed sharp diffraction peaks, while the diffraction peaks from clear calcite and silicon powder were not detected. Possible reasons for the lack of diffraction peaks from these materials are discussed. LEBRA-PXR has potential for use in studies on the diffraction of other materials, and is therefore, expected to be a useful tool for crystallographic analysis.

Hemoglobin D (Hb D) from the Aldabra giant tortoise, Geochelone gigantea, was crystallized by the hanging drop vapor diffusion technique with a precipitant solution containing 10% polyethylene glycol 3350 and 50 mM HEPES-Na, pH 7.5. The Hb D crystals of G. gigantea, which diffract to at least a 2.0 A resolution, belong to the monoclinic space group C2 with unit cell dimensions of a = 112.1 A, b = 62.4 A, c = 54.0 A, and beta = 110.3 degrees. One alphabeta dimer molecule of Hb D existed in an asymmetric unit, with a calculated value of Vm of 2.77 A(3)Da(-1).

The presence of monomer and dimer subunits was revealed, by means of native polyacryl-amide gel electrophoresis (PAGE), in examined arachnid hemocyanins. We determined the N-terminal amino acid sequences of nine monomer subunits prepared from hemolymph of a whipscorpion, Typopeltis crucifer, and a primitive spider, Heptathela kimurai, and two constituent monomers of a dimer subunit from the whipscorpion. Based on a comparison of the sequences, we confirmed that the orthologous hemocyanin subunits are shared between the whipscorpion and the scorpion, Liocheles australasiae, between the primitive spider and the scorpion, and among the whipscorpion, the scorpion, and mygalomorph spiders. This study is the first to demonstrate the presence of orthologus hemocyanin subunits in different orders. Furthermore, it is evident that one of the constituent monomers of the hemocyanin dimer from the whipscorpion is orthologous to the constituent monomers (the group G subunits) of the hemocyanin dimers in mygalo...

Mygalomorph spider's hemocyanins examined contain monomer subunits which are the component parts of hemocyanin hexamers and dimer subunits which bond two hexamers together. We determined the N-terminal amino acid sequences of twenty-two monomer subunits and ten constituent monomers of the dimer subunits prepared from hemolymph of seven mygalomorph spiders. We classified these subunits into eight groups based on the sequence comparison. From the distribution of monomer subunits in mygalomorph spiders, it is evident that duplications and losses of monomer subunits occurred frequently. This is the reason why we cannot detect an orthologous monomer subunit derived from a common ancestral sequence in the seven spiders. These monomer subunits were found in either Atypoidea or Avicularioidea. On the other hand, the dimer subunits having similar N-terminal sequences were found widely in both mygalomorph spider groups, showing that the dimer subunits are more conservative than monomer subunits for their f...

Red blood cells of yellow-spotted river turtles (Podocnemis unifilis, Pleurodira, Chelonia, REPTILIA) have two hemoglobin (Hb) components, Hb A and Hb D. We purified the hemoglobin component homologous to amniote (reptiles, birds, and mammals) adult Hb A which comprises two identical α(A) -globin polypeptides and two identical β-globin polypeptides. To establish the crystal structure of Podocnemis Hb A, we first determined the globin primary structures using cDNA nucleotide sequencing with the assistance of protein sequencing. The purified Podocnemis Hb A produced a different form of crystal for each of the two different buffer systems used: form A, tetragonal crystals (space group, P4₁2₁2), produced under neutral pH (pH 7-8) conditions; and form B, hexagonal crystals (space group, P6₁22), produced under high alkaline pH (pH 11-13) conditions. Single crystals of the two forms were examined by Raman microscopy with an excitation of 532 nm, indicating their structural differences. The crystal structures of the two forms were constructed by X-ray crystallographic diffraction at a resolution of 2.20 A for form A and 2.35 A for form B. The differences of the tertiary and quaternary structures of the two forms were marginal; however, one clear difference was found in helix structure. When comparing Podocnemis Hb A with Hb A from specimens in other taxa, such as Anser indicus (birds) and Homo sapiens (mammals) by SHELXPRO, the root mean square deviation (RMSD) between the corresponding Cα atoms of the two globins does not exceed 2.0 A. These low values indicate the crystal structures resemble each other. Our data on X-ray crystal structures and Raman spectra not only reveal the first findings on the two crystal forms of Podocnemis unifilis Hb A but also provide the first refined models for reptilian adult Hb A.

Monomeric haemoglobin component V (Hb V) from the larva of the midge Propsilocerus akamusi shows high Cl− affinity under high salt concentrations at acidic pH. In order to understand the structural changes that depend on Cl− binding, crystal structures of Hb V were determined under acidic high-salt conditions and the structural changes arising from different haem-bound ligands were simulated. Crystal structures of Hb V under acidic high-salt conditions indicated that the side chain of ArgE10 on the distal face of the haem contributes to stabilizing haem-bound Cl−. The conformation of the Arg side chain in the Cl−-bound form was almost identical to that in ligated Hb V at neutral pH but not to that in met Hb V under acidic salt-free conditions. Furthermore, preliminary molecular-dynamics simulations also indicated that the swinging of the Arg side chain into the haem pocket depends on Cl− ligation. This result suggests that, like pH change, Cl− binding affects the location of the distal Arg residue. Owing to the increased positive electrostatic potential observed in the haem pocket at acidic pH, it was concluded that electrostatic changes caused by pH change and anionic ligand binding may affect the behaviour of the polar Arg residue.

The experiments of the PXR performance carried out for the target crystals with different cutting planes have shown significant difference in the PXR property, which suggests another way to increase the PXR intensity than by increasing the electron beam current. In order to investigate the effect of the geometrical condition of the crystal surface on the PXR property, the experiments have been carried out for the target crystal with a knife-edge-shaped cut surface. For the case with symmetric Bragg geometry on the front surface and asymmetric condition on the rear surface, the rather low intensity X-ray beam has shown considerably good spatial coherence. The X-ray beam with narrow line width has made it possible to obtain X-ray absorption spectra with a high resolution. In contrast, relatively high intensity, which enabled taking an absorption image with the exposure for several tens of seconds, has been obtained for the geometry with asymmetric front surface and symmetric rear surface. This configuration, however, has raised a problem of degradation in the spatial coherence of the X-rays due to the superposition of two different X-ray beams.

A novel X‐ray source based on Parametric X‐ray radiation (PXR) has been employed for phase‐contrast imaging at the Laboratory for Electron Beam Research and Application (LEBRA), Nihon University, Japan. The PXR X‐rays were generated by the 100 MeV electron beam passing through a Si single crystal. The X‐rays in the 16∼34 keV range were chosen for imaging of biological samples. The quasi‐monochromatic, tunable, and coherent X‐ray source is appropriate for this application. In addition, the large X‐ray beam irradiation field of approximately 100 mm in diameter, which was achieved without special optics, suggests that the PXR is applicable to imaging for medical diagnostics.

Haemoglobin component V (Hb V) from the midge larvaPropsilocerus akamusiexhibits oxygen affinity despite the replacement of HisE7 and a pH-dependence of its functional properties. In order to understand the contribution of the distal residue to the ligand-binding properties and the pH-dependent structural changes in this insect Hb, the crystal structure of Hb V was determined under five different pH conditions. Structural comparisons of these Hb structures indicated that at neutral pH ArgE10 contributes to the stabilization of the haem-bound ligand molecule as a functional substitute for the nonpolar E7 residue. However, ArgE10 does not contribute to stabilization at acidic and alkaline pH because of the swinging movement of the Arg side chain under these conditions. This pH-dependent behaviour of Arg results in significant differences in the hydrogen-bond network on the distal side of the haem in the Hb V structures at different pH values. Furthermore, the change in pH results in a partial movement of the F helix, considering that coupled movements of ArgE10 and the F helix determine the haem location at each pH. These results suggested that Hb V retains its functional properties by adapting to the structural changes caused by amino-acid replacements.

The monochromatic X-ray source based on parametric X-ray radiation (PXR) was developed by using Si(111) perfect crystals and the electron beam from the 125-MeV linac at Nihon University. Since the X-ray beam from the PXR system has a large exposure area with uniform flux density, the PXR-based source is suited for X-ray radiography. In addition to ordinary radiography, X-ray absorption spectroscopy and phase-contrast imaging have been developed as advanced applications of PXR. The absorption spectra of several samples were obtained using the energy dispersion of PXR, and the X-ray absorption fine structures (XAFS) were actually found in the spectra. With respect to phase-contrast imaging, refraction-contrast images have been obtained by using the X-ray diffraction in the (+, −, +) arrangement of perfect crystals. The high-contrast and the phase-reversal of the images taken in the experiment suggest that LEBRA-PXR has a high spatial coherence sufficient for phase-contrast imaging.

The monochromatic X‐ray source based on parametric X‐ray radiation (PXR) was developed by using the electron beam from the 125‐MeV linac at Nihon University. The X‐ray generating system consists of two silicon perfect‐crystal plates to offer a wide tunability. The system has actually been providing the energy dispersive monochromatic X‐ray beam in the region of 6 to 20 keV, using Si(111)‐plane for the target and the second crystals. Since the X‐ray beam from the PXR generator has rather high energy resolution and coherency, X‐ray absorption fine structure (XAFS) measurement and phase‐contrast imaging are possible applications of PXR. Actually, preliminary experiments on energy dispersive XAFS measurement and refraction‐contrast imaging have been successfully carried out using the PXR beam.

Phase contrast x‐ray imaging is an important technique for investigation of materials consisted of light atoms, such as soft biological tissues. The tunable monochromatic x‐ray source based on Parametric X‐ray Radiation (PXR), which was developed at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University, provides x‐rays with a high spatial coherence which is an essential property required for phase contrast imaging. In preliminary experiment, refraction contrast images for leaf tissues of a tree and animal specimen have been obtained successfully with the LEBRA‐PXR x‐rays. In the imaging system, the x‐ray that passed through the sample once reflects off the silicon perfect‐crystal x‐ray analyzer at the Bragg angle, and then enters the imaging plate. The bright‐field and the dark‐field phase contrast images have been obtained by infinitesimal rotations of the analyzer, showing the evidence of contrast reversal. Although the conventional radiograph by absorption contrast was also taken with the LEBRA‐PXR, significant differences are found between the radiograph and the phase contrast images.Phase contrast x‐ray imaging is an important technique for investigation of materials consisted of light atoms, such as soft biological tissues. The tunable monochromatic x‐ray source based on Parametric X‐ray Radiation (PXR), which was developed at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University, provides x‐rays with a high spatial coherence which is an essential property required for phase contrast imaging. In preliminary experiment, refraction contrast images for leaf tissues of a tree and animal specimen have been obtained successfully with the LEBRA‐PXR x‐rays. In the imaging system, the x‐ray that passed through the sample once reflects off the silicon perfect‐crystal x‐ray analyzer at the Bragg angle, and then enters the imaging plate. The bright‐field and the dark‐field phase contrast images have been obtained by infinitesimal rotations of the analyzer, showing the evidence of contrast reversal. Although the conventional radiograph by absorption contrast was also ...

The polymorphic components of hemoglobin (Hb) of the midge larva Propsilocerus akamusi were classified into two distinct types dependent on their spectroscopic properties, normal absorption (N) and low absorption (L). Analyses of the amino acid sequences of component VII (N-type Hb) and component V (L-type Hb) from P. akamusi indicated that one remarkable difference is the replacement of the distal histidine (His) with isoleucine (Ile) in component V. To clarify the structural differences between the two Hb components, we determined the crystal structures of components V and VII at resolutions of 1.64 A and 1.50 A, respectively. These crystal structures indicated a short additional helix comprising three amino acid residues at the C-terminal region in component V, and a typical globin fold including eight helices in component VII. Comparison of the heme regions of the Hb components suggests that the structural changes of the heme region in component V on ligation differ from that of usual Hb.

Wavelength tunable Free Electron Laser, FEL, was irradiated onto the polished surfaces of human tooth enamel and dentin using the FEL system at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. LEBRA-FEL system was so powerful that only 2 mJ/pulse shot resulted in an apparent pit on the surfaces. The pit showed neither marked scorch nor formation of secondary crystalline phase revealed by micro-XRD and micro-FTIR. Optimum wavelength for pit formation on the dental hard tissues was about 3.0 mm. However, the optimum wavelengths for enamel and dentin should be at 3.2 mm, 3.0 mm, respectively. The results strongly suggested that the ablation mechanism by laser irradiation for dental hard tissues might be not the simple interaction of laser beams with water, but complex phenomena, which could not be neglected of the hard tissue components and structure.

A novel X-ray source based on parametric X-ray radiation (PXR) has been employed for X-ray imaging at the Laboratory for Electron Beam Research and Application (LEBRA), Nihon University. Notable features of PXR are tunable energy, monochromaticity with spatial chirp, narrow local bandwidth and spatial coherence. Since the X-ray beam from the PXR system has a large irradiation area with uniform flux density, the PXR-based source is suited for X-ray imaging, especially for application to phase-contrast imaging. Despite the cone-like X-ray beam, diffraction-enhanced imaging (DEI) can be employed as a phase contrast imaging technique. DEI experiments were performed using 14- to 34-keV X-rays and the phase-gradient images were obtained. The results demonstrated the capability of PXR as an X-ray source for phase-contrast imaging with a large irradiation field attributed to the cone-beam effect. Given the significant properties of the LEBRA-PXR source, the result suggests the possible construction of a compact linac-driven PXR-Imaging instrument and its application to medical diagnoses.

An in-line ionization chamber has been developed for the real-time measurement of the absolute intensity of the pulsed parametric X-ray (PXR) beam during irradiation experiments. The quasi-monochromatic PXR generating system was developed at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. In contrast to typical narrow X-ray beams in synchrotron radiation facilities, the PXR beam profile is as large as approximately 100 mm in diameter with rather uniform flux distribution at the X-ray output port in the experimental hall. The energy of the PXR beam ranges from 5 to 34 keV, which is specified by the PXR target crystal plane and its geometrical condition. The ionization chamber is of a plane parallel type employing 6-μm thick double-sided aluminum vapor-deposited polyester films for the plane electrodes through which the X-ray beam passes. The plane bias electrode has been placed at an equal distance of 25 mm from the two plane earth electrodes that act as the beam windows with an aperture diameter of 120 mm. Due to the pulsed property of the PXR beam and the geometrical configuration of the ionization chamber, the charge-sensitive preamplifier output pulse height represents an integral of the fast electron current, corresponding to a half of the total ionization charge produced by the beam. The intensity of the PXR beam has been measured for various X-ray energies by using nitrogen and argon, respectively, as the filling gas.