Shozo Ishizaka

Biological effects of Auger processes of bromine on yeast cells induced by monochromatic synchrotron X-rays.

The biological effects of inner-shell ionization in bromine atoms incorporated into DNA in the form of bromodeoxyuridine monophosphate (BrdUMP), induced by monochromatized synchrotron X-rays, were studied using a deoxythymidine monophosphate (dTMP)-permeable mutant of yeast, Saccharomyces cerevisiae. The BrdUMP-incorporated yeast cells were irradiated with monochromatic X-rays of 13.51 or 13.45 keV, between which the bromine K-absorption edge (13.47 keV) is located. The cells were 1.07 times more sensitive to irradiation by 13.51 keV X-rays than at 13.45 keV, while dTMP-incorporated cells did not show any difference in sensitivity. In the presence of a radioprotector during irradiation, BrdUMP-incorporated cells showed a larger enhancement (1.20). These enhancements observed in the bromine-incorporated cells cannot be explained only by an increase of the absorbed dose due to a substitution of CH3 group of thymine by bromine. It may be concluded that a major part of the enhancement was caused by inner-shell photoionization, followed by an Auger cascade of the bromine in the DNA. The quantum yield of lethality caused by the photoabsorption of bromine K-shell is not affected by the presence of cysteamine, suggesting the biological enhancement by the Auger processes may not be influenced by chemical protection.

Interaction between cell-binding domain and extracellular matrix-binding domain of fibronectin determined by fluorescence depolarization

Interaction of domains in fibronectin was observed by photometry of fluorescence polarization of three kinds of dye; [N-(1-anilinonaphthyl-4)]maleimide (ANM tau = 5 ns), [N-(3-fluoranthyl)]maleimide (FAM tau = 20 ns), and [N-(3-pyrene)]maleimide (PRM tau = 100 ns). Each dye was labeled at a free sulfhydryl group in the cell-binding domain. Neither fluorescence of ANM with short fluorescent lifetime, FAM with long lifetime, nor PRM with longer fluorescent lifetime on fibronectin depolarized as much as the free dye. It was found that each dye was firmly fixed in the cell-binding domain. When heparin or gelatin was added in the solution of PRM-fibronectin complex, the fluorescence polarization tended to increase principally by combining heparin or gelatin to fibronectin. It was found that the rotation of whole or partial fibronectin containing the cell-binding domain through fluorescent lifetime of 100 ns was suppressed by combining of heparin or gelatin to fibronectin. When heparin or gelatin was added in the solution of ANM- or FAM-fibronectin complex, on the contrary, the fluorescence polarization tended to decrease, that is, slightly depolarize through the fluorescent lifetime of 5 or 20 ns, respectively. It was found that the rotation of the cell-binding domain, or of part of the fibronectin molecule containing the domain, was slightly promoted by combining heparin or gelatin to its domain. These results indicate that an interaction of the heparin- or gelatin-binding domain with the cell-binding domain was induced by the combining of heparin or gelatin to the respective domains.

Development of a circularly polarizing microscope with a polarizing undulator

A circularly polarizing microscope by which we intend to obtain images with CD (circular dichroism) or CIDS (circular intensity differential scattering) in order to observe the structure and distribution of biomolecules has been constructed by using a polarizing undulator as the polarizing light source. The polarizing undulator with crossed and retarded magnetic field having fifteen periods was installed in the electron storage ring NIJI‐II in the Electrotechnical Laboratory. A Schwarzschild‐type mirror system combined with a convex mirror was developed in order to focus the undulator radiation to a microbeam keeping the quality of polarization of the radiation from the undulator. The beam size was from 0.66 μm (at wavelength 200 nm) to 0.96 μm (at 400 nm). Using a scanning sample stage and a photomultiplier which was positioned in the back of the sample, some images with transmitted and scattered light from fibrous DNA have been obtained. Attempts have also been made at obtaining images with CD and CIDS ...

Paraticulate metals in waters of a typical irrigation river: The River Sakuragawa, Japan

The particulate metallic elements in waters of a water system of the River Sakuragawa and Lake Kasumigaura were measured by the multielement analyses using particle-induced X-ray emission. The heavy metal particulates for environmental standards were less than 0.0001 ppm for Cd, 0.00037 ppm for Cr, and 0.00078 ppm both for Hg and Pb in the river waters. The predominant metal particles in the waters were Fe, Mn, and Zn.

Some elements comprising particulate matter during summer in waters of various environments in British Columbia, Canada

Abstract Multi-elemental traces comprising particulate matter in natural water collected during summer in 1978 and 1979 from British Columbia, Canada, were analyzed by α-particle excited X-ray fluorometry. Common elements from all waters examined were Si, Cl, Ca and Fe. The similarity of their distribution in different aquatic environments was statistically analyzed. They were distributed homogeneously in the marine environment but heterogeneously in the freshwater environments. No heavy metals concerned with the environmental standards were detected for all waters examined.