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The influence of ligands at the sixth dismal position on the formation of pi-cation radical in horseradish peroxidase (HRP) is determined. The results showed that fluoride accelerates the reaction of HRP with IrCl(sub 6)(super 2-) to form a new product which is a ferric flouride complex with a porphyrin pi-cation radical. Addition of cyanide slows the reaction. The pH dependence of the one-electron reduction potential of the oxidized HRP-fluoride complex was also determined.

X-ray absorption spectroscopy of the heme-iron structures of lignin and manganese peroxidase isoenzymes from the white rot fungus, Phanerochaete chrysosporium, reveals differences in the atoms of the second and third shell. The data from the second shell indicate H4, H8 and H10 isoenzymes form a group, while the H3 and H5 form another group but the H2 is separate from both the groups. The differences in the shells are probably related to variations in heme conformations.

X-ray absorption fine structure spectroscopy was used in studying the mative lactoperoxidase (LPO), compound II, and the reduced forms at pH6 and pH9. Similarities and differences in the heme-active structures of several peroxidases including horseradish peroxidase, cytochrome c peroxidase, catalase and lignin peroxidase were determined. In addition, changes in spin state were not observed at the different pH values.

The active site of the heme peroxidase horseradish peroxidase (HRP) compound II at pH 7 and pH 10 was investigated using X-ray absorption spectroscopy. The aim was to further characterize the catalytic reaction center of HRP. The results showed that at pH 10, there was a decrease in the Fe-O bond length of HRP compound II. This was attributed to the loss of a hydrogen bond between the oxygen ligand and an amino acid in the heme pocket at higher pH.

Research was conducted on the structure of the active site of lignin peroxidase isozyme H2 using x-ray absorption spectroscopy. The iron content of the native enzyme, the reduced enzyme and compound III of the glycosylated protein was analyzed. Fe-pyrrole nitrogen, Fe-proximal nitrogen and Fe-distal ligand distances were determined. The active-site structure of compound III among the distances was also identified.

Author(s): M Ichikawa; T Asai; T Saito; G Yamamoto; S Seo; I Yamazaki; T Yamagata; K Mitani; S Chiba; H Hirai; S Ogawa; M Kurokawa Nat. Med. 10, 299-304 (2004) [...]

Purpose: Effects of a long-acting ophthalmic formulation of carteolol containing alginic acid on the corneal epithelial barrier function and its water retentive effect were investigated.Methods: Using 10 healthy adult subjects, 2% Mikelan Ophthalmic Solution(®) (MK) was instilled in the eye once daily for 7 days (MK group) and then after a washout period of at least 28 days, 2% Mikelan LA Ophthalmic Solution(®) (MKLA) was instilled in the eye once daily for 7 days (LA group). As an index of the corneal epithelial barrier function, the fluorescein uptake was measured using Kowa FL-500. A Schirmer test was conducted to evaluate the tear dynamics. In another 10 subjects, 0.5% Timoptol(®) (TM) was instilled in the eye unilaterally twice daily for 7 days (TM group), and the tests were conducted in the same manner.Results: Concerning the fluorescein uptake before and after initiation of instillation, the levels before and at 7 days after initiation of instillation were 20.7 and 26.5 ng/mL, respectively, in the LA group and 20.6 and 26.4 ng/mL, respectively, in the MK group, showing no significant difference between levels before and after initiation of instillation in either group. In the TM group, the levels were 21.4 and 65.5 ng/mL, respectively, showing a significant increase after initiation of instillation. In the Schirmer test, the values before and after initiation of instillation were 16.8 and 20.7 mm, respectively, in the LA group and 13.7 and 12.7 mm, respectively, in the MK group, showing a trend toward increase in the LA group.Conclusions: The findings suggest that the long-acting ophthalmic formulation of carteolol containing alginic acid does not affect the corneal epithelial barrier function and that it may possess a water retentive action. [ABSTRACT FROM AUTHOR]

In this work, the uranium (U) content in sediment and soil samples collected near the Santos and São Vicente estuaries was determined using the fission track registration technique (SSNTD). The sediment and soil samples after oven-dried and pulverised were prepared in the solution form. About 10 µl of this solution was deposited on a plastic detector and irradiated at the IPEN-IEA-R1 (3.5 MW) nuclear reactor. After the irradiation and chemical etching of the plastic foils, the fission tracks were counted with a system consisting of an optical microscope together with a video camera and a PC. The U content in the analysed samples ranged from 3.12 ± 0.55 to 18.3 ± 1.2 ppm for sediments and from 3.21 ± 0.63 to 11.5 ± 1.1 ppm for soils or in terms of 238U equivalent activity from 38.5 ± 6.8 to 226 ± 15 and 39.6 ± 7.8 to 142 ± 14 Bq kg−1 for sediments and soils, respectively. These results were compared with other values reported in the literature for sediments and soils collected in environments similar to the ones studied in this work. Most of the values obtained in this work are higher than the world mean and are in reasonable agreement with results found by other authors for sediments and soils from regions considered as polluted or with a high level of radioactivity. [ABSTRACT FROM PUBLISHER]

The structure around the metal site of mavicyanin, a protein molecule with a copper site, was investigated in solution by using time-differential perturbed angular correlation of 117In. The electric field gradient (EFG) of the metal site was deduced from the measurement. It demonstrated that the site in a mutant-type mavicyanin, Thr15Ala-Mav, gives an EFG different from that in the wild-type mavicyanin does. The pH dependence of the EFG was also observed for both proteins. [ABSTRACT FROM AUTHOR]

A microchannel-plate photomultiplier (MCP-PMT) has been applied to the time-correlated single-photon counting technique. Electrical and timing characteristics were investigated for the two types of MCP-PMT’s, nonproximity type (Hamamatsu R1264) and proximity type (R1564), which are different in distance between the photocathode and MCP. In the proximity type, the transit-time spread was found to be 60 ps, i.e., a factor of 4 shorter than that in conventional photomultipliers with a dynode string. It was concluded that both types of MCP-PMT’s are fully applicable to the single-photon counting method and that the proximity type MCP-PMT in particular leads to further improvements in the cathode transit-time difference and the wavelength effect of the timing properties. Some examples of experimental results are shown for fluorescence decay curves and picosecond time-resolved spectra. [ABSTRACT FROM AUTHOR]

To study the effect of ipriflavone on osteoclast-mediated bone resorption and new osteoclast formation, we used an unfractionated bone cell culture system containing mature osteoclasts from femur and tibia of newborn mice. Ipriflavone (10(-5) M) inhibited pit formation on dentin slices and caused a decrease in the number of tartrate-resistant acid phosphatase (TRAP)-positive (+) multinucleate cells (MNCs) in a 4-day culture period in which no increase in the number of TRAP(+)-MNCs was observed in the presence of 5% fetal bovine serum (FBS) and 10(-8) M 1 alpha,25-dihydroxy-vitamin D3 (1 alpha,25(OH)2D3). During the following 12 days, both the total area of the pits and the number of TRAP(+)-MNCs increased in the control. Continuous treatment with ipriflavone also inhibited the increase in pit area during this period. These effects of ipriflavone were reversible. Furthermore, the differentiation of osteoclasts was examined when preexisting TRAP(+)-MNCs were removed by incubation in the absence of 1 alpha,25(OH)2D3 for the initial 4 days in culture dishes without dentin slices. When 1 alpha,25(OH)2D3 and ipriflavone were added to the medium on the 4th day, ipriflavone inhibited new TRAP(+)-MNC formation stimulated by 1 alpha,25(OH)2D3 in a dose-dependent manner. However, pretreatment of the cells with ipriflavone before the addition of 1 alpha,25(OH)2D3 did not inhibit TRAP(+)-MNC formation. These results indicate that ipriflavone inhibits both the activation of mature osteoclasts and the formation of new osteoclasts without affecting growth of TRAP-negative progenitor cells. [ABSTRACT FROM AUTHOR]

Effects of ipriflavone (7-isopropoxyisoflavone) on osteoclast-induced bone resorption were evaluated using an unfractionated bone cell culture system containing mature osteoclasts from the femur and tibia of newborn mice. When cells were cultured for 4 days on dentin slices in the presence of 5% fetal bovine serum and 10(-8) M 1 alpha, 25(OH)2D3, ipriflavone (3 x 10(-7) -3 x 10(-5) M) inhibited pit formation and caused a decrease in the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNCs). The lowest significant effect was observed at a concentration of 10(-6) M. Unlike ipriflavone, calcitonin inhibited pit formation 4 days after the culture was started without affecting the number of TRAP-positive MNCs. Ipriflavone still inhibited pit formation when the culture period was 13 days, when new osteoclasts were expected to be formed. These findings suggest that ipriflavone inhibits new osteoclast formation and bone resorption at the cellular level. [ABSTRACT FROM AUTHOR]