Aqueous solutions of polyallylamine hydrochloride were examined by small angle x-ray scattering. When the polymer concentration of coexisting simple salt was low, a single, broad peak was observed. The peak was interpreted as indicating the presence of an ordered arrangement of macroions in the solutions. The intermacroion spacing was calculated by the Bragg equation and found to be much smaller than the average intermacroion spacing calculable from the polymer concentration, suggesting that there exist ordered regions and at the same time disordered regions in the solutions. The Bragg spacing decreased with increasing polymer concentration and increased with increasing salt concentration. Mixing of two samples of different molecular weights gave a new scattering peak in between the original peaks of the mother samples, which supports the intermolecular nature of the ordering. The peak height was lowered with increasing temperature. The scattering peak was found to stay unaffected for 21 days. Keywordssmall angle x-ray scattering, ordering of macroions in solutions, polyallylamine hydrochloride

Dilute aqueous solutions of bovine serum albumin, lysozyme, chondroitin sulfate, and tRNA were measured by small-angle x-ray scattering. The scattering curves showed a single, broad peak as was observed for synthetic polyelectrolytes, indicating the presence of an ordered distribution of charged solutes. The intermolecular distance evaluated from the peak position (2Dexpt) increased with decreasing polymer concentration and with increasing salt concentration. Except for chondroitin sulfate, 2Dexpt values were nearly equal to the interparticle distance (2D0) calculated based on the assumption of a uniform distribution. The observed relationship between 2Dexpt and 2D0 was in agreement with the proposal that intermacroion attraction is weak for low-charge density particles under discussion. This attraction and repulsive interparticle interaction create a ‘‘secondary’’ minimum in the potential curve enabling ordering to take place. For tRNA, the scattering peak became lower with rising temperature. The fact that only a single, broad peak could be observed was rationalized by invoking the concept of distortions of ordering particles such as the paracrystallinity, and the thermal motion and the crystalline size effect. The correlation hole theory based on repulsive interaction is critically discussed, particularly in light of the experimental fact that the peak position of albumin shifts toward wider angles with increasing number of charges.

Currently, nitric oxide and sulfur dioxide emitted from stationary combustion facilities have been removed separately by selective catalytic reduction processes and wet scrubbing processes. There is no practical process successful for simultaneous removal of N O and SO2. Since scrubbing soiutions for wet NO removal also remove SO,, wet scrubbing processes are potential candidates for simultaneous NO and SO, removal. For instance, by use of liquid-phase reaction sequences in which both dissolved N O and SO, participate, simultaneous removal of both the gases can be achieved effectively in a single step or equipment. Aqueous solutions of Na,SO, with added Fe(I1)EDTA (ferrous ion coordinated to ethylenediaminetetraacetic acid) seem to be promising absorbents to fulfill such a possibility. To establish the procedure for inevitable regeneration or treatment of spent adsorbent, it is necessary to clarify the whole scheme of the liquid phase complicated reactions.In our previous work (Sada et al., 1984(Sada et al., , 1986, the pathways of the liquid-phase reactions were completed and presented in the form of a map. The degree of removal of NO was found to depend on the concentration of Fe(II), which was determined from a balance of oxidation and reduction rates of iron. The removal of N O during simultaneous absorption of NO and SO, could be predicted from corresponding experimental results for absorption of only NO into an absorbent of the same pH value. Regarding reaction kinetics, the reduction of Fe(II1) to Fe(I1) by HS03-with coexisting EDTA, the oxidation of Fe(1I) to Fe(II1) by N O in the presence of Na,SO,, and the oxidation of Fe(I1)EDTA by dissolved oxygen were investigated (Sada et al., 1986(Sada et al., , 1987.In view of the results of our earlier fundamental work cited above, there are two important considerations that emerge in the simultaneous N O and SO, removal process: 1. To keep the level of the concentration of Fe(I1) as high as possible and for this purpose, to reduce a portion of the effluent Correspondence concerning this paper should be addressed to E. Sada stream by sulfite a t the boiling temperature in the outer loop of the absorberThe former is required from the'experimental result that the degree of N O removal mainly depends on the concentration of Fe(I1). The latter is necessary because of the pH of the absorbent is decreased by simultaneously absorbed SO,.In the present work, the process flow diagram for simultaneous removal of N O and SO2 by absorption into an aqueous solution of Na,SO, with added Fe(I1)EDTA was first proposed on the basis of our earlier fundamental work. Secondly, to put this simultaneous removal process into practical application, long-term absorption tests and the regeneration of (simulated) spent liquor by reduction at its boiling temperature were undertaken.2. to control the pH of the absorvent. Background of Simltaneous NO and SO, Removal ProcessThe wet scrubbing method generally has a significant disadvantage of inevitable waste-liquor treatment, so that the proce...

Human oxidation resistance 1 (OXR1) was identified as a protein that decreases genomic mutations in Escherichia coli caused by oxidative DNA damage. However, the mechanism by which OXR1 defends against genome instability has not been elucidated. To clarify how OXR1 maintains genome stability, the effects of OXR1-depletion on genome stability were investigated in OXR1-depleted HeLa cells using gamma-rays (γ-rays). The OXR1-depleted cells had higher levels of superoxide and micronucleus (MN) formation than control cells after irradiation. OXR1-overexpression alleviated the increases in reactive oxygen species (ROS) level and MN formation after irradiation. The increased MN formation in irradiated OXR1-depleted cells was partially attenuated by the ROS inhibitor N-acetyl-L-cysteine, suggesting that OXR1-depeletion increases ROS-dependent genome instability. We also found that OXR1-depletion shortened the duration of γ-ray-induced G2/M arrest. In the presence of the cell cycle checkpoint inhibitor caffeine, the level of MN formed after irradiation was similar between control and OXR1-depleted cells, demonstrating that OXR1-depletion accelerates MN formation through abrogation of G2/M arrest. In OXR1-depleted cells, the level of cyclin D1 protein expression was increased. Here we report that OXR1 prevents genome instability by cell cycle regulation as well as oxidative stress defense.

Ionizing radiations such as X-ray and γ-ray can directly or indirectly produce clustered or multiple damages in DNA. Previous studies have reported that overexpression of DNA glycosylases in Escherichia coli (E. coli) and human lymphoblast cells caused increased sensitivity to γ-ray and X-ray irradiation. However, the effects and the mechanisms of other radiation, such as low dose rate radiation, heavy-ion beams, or hydrogen peroxide (H2O2), are still poorly understood. In the present study, we constructed a stable HeLaS3 cell line overexpressing human 8-oxoguanine DNA N-glycosylase 1 (hOGG1) protein. We determined the survival of HeLaS3 and HeLaS3/hOGG1 cells exposed to UV, heavy-ion beams, γ-rays, and H2O2. The results showed that HeLaS3 cells overexpressing hOGG1 were more sensitive to γ-rays, OH(•), and H2O2, but not to UV or heavy-ion beams, than control HeLaS3. We further determined the levels of 8-oxoG foci and of chromosomal double-strand breaks (DSBs) by detecting γ-H2AX foci formation in DNA. The results demonstrated that both γ-rays and H2O2 induced 8-oxoguanine (8-oxoG) foci formation in HeLaS3 cells. hOGG1-overexpressing cells had increased amounts of γ-H2AX foci and decreased amounts of 8-oxoG foci compared with HeLaS3 control cells. These results suggest that excess hOGG1 removes the oxidatively damaged 8-oxoG in DNA more efficiently and therefore generates more DSBs. Micronucleus formation also supported this conclusion. Low dose-rate γ-ray effects were also investigated. We first found that overexpression of hOGG1 also caused increased sensitivity to low dose rate γ-ray irradiation. The rate of micronucleus formation supported the notion that low dose rate irradiation increased genome instability.