THE WHITE MEMBRANE OF CRYSTALLINE BACTERIOOPSIN IN HALOBACTERIUM HALOBIUM STRAIN R1mW AND ITS CONVERSION INTO PURPLE MEMBRANE BY EXOGENOUS RETINAL

Abstract— A new strain isolated from Halobacterium halobium designated R₁mW, contained negligible amounts of isoprenoid pigments, had a yellowish white color due to respiratory pigments and showed no proton movement in response to light. However, addition of all-trans-retinal converted R₁mW into purple cells. Formation of both halorhodopsin and bacteriorhodopsin was indicated by induction of light-dependent proton uptake and release, respectively. Both haloopsin and bacterioopsin were thus postulated to be present in R₁mW. Electron micrographs of freeze-fractured cytoplasmic membranes revealed patches in a hexagonal array of trimeric particles, comparable to the purple membrane structure. These white membrane patches were isolated by procedures similar to those for the purple membrane. The white membrane's buoyant density was about 1.18 g/m/, and its main component migrated on sodium dodecylsulfate polyacrylamide gels at the same rate as bacteriorhodopsin. The white membrane showed only a small absorption peak at ～410nm due to contaminating respiratory pigments and a strong absorption at around 275 nm and shorter wavelengths. The white membrane was thus considered to be mainly composed of bacterioopsin, which was readily converted into bacteriorhodopsin by an addition of all-trans-retinal. The absorption and CD spectra of the white membrane were measured before and after addition of retinal. The molar extinction coefficient of dark-adapted bacteriorhodopsin formed was determined to be 53000M^?1 cm^?1 at 560 nm from retinal binding studies. The CD spectrum of the white membrane was negligible in the visible region but showed several bands assigned to aromatic and backbone structures in the UV region. Retinal addition caused considerable changes in the spectrum, yielding the CD spectrum of crystalline purple membrane bacteriorhodopsin. The white membrane thus appears to be a preparation suitable for structure-function studies of bacteriorhodopsin.     

Reaction between carbon dioxide and elementary fluorine

Reactions between carbon dioxide and fluorine were examined at temperatures of 303-523 K under various pressure and mixture ratios of both gases. Reactions were carried out similarly under the existence of NaF, CsF and EuF₃.After the reaction, fluorine was removed and the reaction products were analyzed using FT-IR, GC/FT-IR and GC/MS. The major products were CF₃OF, COF₂, CF₄ and CF₂(OF)₂.The best yield of COF₂ was 11.1% under the reaction condition of CO₂/F₂ = 76 kPa/76 kPa with temperature of 498 K for 72 h in a direct reaction. The formation rate of COF₂ in the direct reaction was estimated as 0.232 dm³ mol⁻¹ h⁻¹ under the reaction conditions of CO₂/F₂ = 76 kPa/76 kPa, at 498 K. In the presence of CsF, it was estimated as 1.88 dm³ mol⁻¹ h⁻¹ at CO₂/F₂ = 76 kPa/76 kPa at 498 K.The activation energy of the COF₂ formation in the direct reaction was estimated as 45.7 kJ mol⁻¹ at CO₂/F₂ = 76 kPa/76 kPa at 498 K. In addition, 24.2 and 38.9 kJ mol⁻¹ were evaluated at CO₂/F₂ = 76 kPa/76 kPa at 498 K, respectively, in the presence of CsF and EuF₃.     

Seasonal variations of atmospheric210Pb and7Be concentrations at Kumamoto, Japan and their removal from the atmosphere as wet and dry depositions</p> </p>

Summary A relatively simple chemical separation procedure has been developed for the simultaneous determination of⁸⁹Sr and ⁹ 0Sractivities in water samples and on aerosol-filters of the Nuclear Power Plant (NPP) Paks origin. The procedure combines the cation-exchange chromatographic (Dowex 50 WX 8 resin) and solid phase extraction (EIChroM Sr.Spec?, DC18C6 crown ether) steps. The beta-radiation of radionuclides can be measured directly after the chemical separation by LSC. The activities of⁸⁹Sr,⁹⁰Sr and⁹⁰Y are calculated from an over determined set of equations using a method of constrained optimization technique. The equations are based on LSC measurements performed in three counting windows plus the⁹⁰Sr-⁹⁰Y decay law. The chemical yield of strontium is determined by ICP-AES. The lowest limits of detectable activity, for the measurement time of 600 minutes, are 30 mBq/sample and 18 mBq/sample for⁸⁹Sr and⁹⁰Sr, respectively.     

Synthesis and characterization of 1,3,4,-thiadiazole-containing polyethers from 2,5-bis (4-fluorophenyl)-1,3,4-thiadiazole and various aromatic diols

Seven 1,3,4-thiadiazole-containing polyethers with reduced viscosities of 0.27–1.44 dL/g were synthesized by the high-temperature solution polycondensation of novel activated difluoride, 2,5-bis (4-fluorophenyl)-1,3,4-thiadiazole, with aromatic diols possessing a variety of ring structures. The expected chemical structures were confirmed by IR and ¹H-NMR spectroscopy and elemental analysis. Of all the polymers, three polyethers were highly crystalline and soluble only in limited solvents such as concentrated sulfuric acid. The other polyethers were amorphous and dissolved easily in a variety of organic solvents including N-methyl-2-pyrrolidone (NMP), phenols, and chlorinated hydrocarbons. Colorless to slightly yellow-colored, transparent, and tough films could be cast from the NMP solutions of the amorphous polyethers. The mechanical properties of the films were excellent, and their tensile strength, elongation at break, and tensile moduli were in the ranges of 48–72 MPa, 5–7%, and 1.3–1.9 GPa, respectively. The amorphous polyethers had high glass transition temperatures of 204–299°C. All the polyethers were highly thermally and thermooxidatively stable and exhibited no weight loss up to 400°C, with 10% weight loss being recorded at 464–513°C in air. © 1994 John Wiley & Sons, Inc.     

Deformed phthalocyanines: synthesis and characterization of zinc phthalocyanines bearing phenyl substituents at the 1-, 4-, 8-, 11-, 15-, 18-, 22-, and/or 25-positions

The synthesis of a series of zinc phthalocyanines partially phenyl-substituted at the 1-, 4-, 8-, 11-, 15-, 18-, 22-, and/or 25-positions (the so-called alpha-positions) is reported. Macrocycle formation based on 3,6-diphenylphthalonitrile, o-phthalonitrile, and zinc acetate predominantly yielded the near-planar disubstituted complex and opposite tetrasubstituted isomer, while the lithium method yielded the sterically hindered hexasubstituted complex and adjacent tetrasubstituted isomer. All compounds have been characterized by 1H NMR, MALDI-TOF-MS, and elemental analysis methods. In addition, crystal structures have been solved for the di-, hexa-, and octasubstituted complexes and the adjacent tetrasubstituted isomer. DFT geometry optimization calculations predict more highly deformed structures than those observed in the crystals. The packing force of the crystals cannot therefore be ignored, particularly for the less phenyl-substituted derivatives. The crystal structures have revealed that overlap of the phenyl groups causes substantial deformation of the phthalocyanine (Pc) ligands within the crystals, while strong pi-pi stacking in the remainder of the Pc moiety lacking phenyl substituents can suppress the impact of the deformation. Absorption spectra show sizable red shifts of the Q-band with increasing number of phenyl groups. Analysis of the results of absorption spectra and electrochemical measurements reveals that a substantial portion of the red shift is attributable to the ring deformations. Molecular orbital calculations lend further support to this conclusion. A moderately intense absorption band emerging at around 430 nm for highly deformed octaphenyl-substituted zinc Pc can be assigned to the HOMO-->LUMO+3 transition, which is parity-forbidden for planar Pcs, but becomes allowed since the ring deformations remove the center of symmetry.     

Synthetic studies on mitomycins. 2. A synthesis of 9a-hydroxy-5,8-dideoxomitosane skeleton through a novel retroaldol type of ring-opening reaction.

A synthesis of 9a-hydroxy-5,8-dideoxomitosanes was accomplished by the transannular cyclization of hydro-1-benzazocinone intermediates derived from 3-(2,5-dioxo-1-methylcyclopentyl)-6-methyl-p-phenylenediamine derivatives. These mitosanes were led to the 8-membered ring system by an oxidative ring-opening reaction.     

Improvement of Corrosion Resistance of Metals by an Environmentally Friendly Silica Coating Method

Corrosion resistance of stainless steel and Zn plated steel can be improved by a chromium-free environmentally friendly chemical solution deposition method. Precursor solutions were prepared from tetraethoxysilane with polymer, and were deposited on stainless steel, Zn plated steel and aluminum alloy by dip coating, followed by heat treatment. Addition of polymer to the precursor solution proved very effective in preparing films free from cracks on stainless steel and aluminum alloy substrates. The corrosion resistance was greatly improved by the resulting sub-micron thick silica-polymer hybrid film coatings on stainless steel and on Zn plated steel prepared at 200°C. The hardness of aluminum alloy coated with silica-PMMA hybrid film was improved by 7% over uncoated alloy.     

Effects of atmosphere on laser vaporization and excitation processes of solid samples

Effects of atmosphere on the laser vaporization and excitation processes were investigated with spectral measurements and with the direct measurement of vaporized weight of samples. The samples, metals and ceramics, were positioned in three different atmospheres, i.e. air, argon and helium, from atmospheric pressure to a pressure reduced to a few torr. The time-resolved emission intensities of the Fe I lines and the Al I lines of the Al alloy and Al metal samples were measured in two time windows, i.e. 0–1 μs and 1 μs-1 ms. The excitation temperatures and the electron number densities of the plasmas were also estimated. The emission spectra, the excitation temperatures, and the electron densities were shown to be appreciably influenced by the ambient atmosphere. The amount of sample vaporized which was measured directly with an electric micro-balance after irradiation by 500 laser shots changed considerably with the atmosphere, e.g. from 12 ng/pulse at atmospheric pressure to 330 ng/pulse at 10 torr in argon.

The results are discussed in the scope of the possibility of ambient gas breakdown before sample vaporization and a change in the laser radiation coupling to the solid surface. It is revealed that the control of the interaction between laser radiation and plasmas and the prevention of the preceding gas breakdown are important for effective laser vaporization and for the emission measurement of the plasmas. The sample characteristics also influence the initiation stage of the plasmas and the effects from the atmosphere.     

Stepwise refolding of Acid-denatured myoglobin: Evidence from electrospray mass spectrometry

Application of electrospray mass spectrometry (ES/MS) to a protein refolding study was demonstrated. Acid denaturation of equine myoglobin was reversed by adding various amounts of ammonium hydroxide to the protein that was unfolded in 10% acetic acid. The protein refolding process was followed by ES/MS, in which both the changes in the protein charge-state distribution and mass were monitored. The ES/MS results show that the pH-dependent renaturation of the acid-denatured myoglobin is stepwise, consisting of two major steps. The unfolded polypeptide chain first refolds to establish a compact nativelike structure, without the assistance of the heme prosthetic group. The newly formed binding cavity then retains the heme group by noncovalent interactions. It is also shown that inclusion of a stabilizing buffer, such as ammonium acetate, in the protein solution is greatly beneficial to the ES/MS detection of intact noncovalent globin/heme complex.     

Solid-state polymerization of long-chain vinyl compounds. V. Two-step postpolymerization of octadecyl acrylate by temperature increase and by stepwise γ-ray irradiation

The mechanism of two-dimensional polymerization of octadecyl acrylate in lamellar crystal was investigated in two-step postpolymerizations by temperature increase and stepwiseγ-ray irradiation in lieu of the usual one-step reaction. Two-step postpolymerizations by these procedures are interpreted satisfactorily by the cone model, which assumes that the polymerization probability of the monomer molecules in a single layer is distributed conically around the initiation point. It was found that the propagating radicals were living, even in the saturated stage, and the effect of the polymer chains already formed on the propagating and terminating reactions was evident. Furthermore, molecular weight distributions of the resultant poly(octadecyl acrylate) measured by gel permeation chromatography (GPC) were broad. The values of M_w /M _n for the two-step post polymerizations were 4.71–7.03, whereas those for one-step reactions were 3.26–5.54.