Application of dibutyltin oxide method to regioselective acylation and alkylation of tylosin at C-4'

4'-O-Acyl-, 4'-O-alkyl- and 4'-deoxy-tylosin derivatives were synthesized using 2'-O-acetyl-3',4'-O-(dibutyl-stannio)tylosin as a synthetic intermediate. The in vitro biological evaluation showed that the new derivatives were active against macrolide-resistant clinical isolates of bacteria and mycoplasmas, and that they were resistant to hepatic esterase.     

Valency states of radioactive antimony in hydrochloric acid solutions. Preparation and stability of antimony tracer for radioanalytical use

Variations of¹²⁵Sb valency states in HCl solutions were investigated by the use of the N-benzoyl-N-phenyl-hydroxylamine (BPHA) extraction method.¹²⁵Sb(V) is completely reduced to Sb(III) by one hour refluxing in conc. HCl.¹²⁵Sb(III) is gradually oxidized to Sb(V) in solutions of low HCl concentrations by the effects of their own radiations. Natural light promotes such oxidation reactions. By utilizing such oxidation-reduction effects¹²⁵Sb(V) can be easily prepared from¹²⁵Sb(III) and also¹²⁵Sb(III) can be prepared by the reduction of Cl _aq ⁻ . Their valency states were stable on keeping them in brown-colored bottles at 6M HCl concentrations.     

Photochemische Reaktionen. 107. Mitteilung. Zur Photochemie offenkettiger 2,6-bzw. 2,7-Dien-Carbonylverbindungen

The Photochemistry of Open-Chained 2,6- or 2,7-Dien-Carbonyl Compounds On ¹n, π*-excitation (λ > 347 nm) citral (5) and the methyl ketone 10 isomerize to compounds A (7, 19) and B (6, 20) , whereas the phenyl ketone 11 changes into the isomer 24 of type E. Evidence is given that the conversions to A and B may arise from the ³n, π*-state of the 2,6-diene-carbonyl compounds. On ¹n, π*-excitation (λ = 254 nm) 5 and 10 yield the isomers A (7, 19) and D (18, 22) , but no products of type B. Furthermore, conversion of 10 to the isomer 21 of type C is observed. Selective ¹n, π*-excitation (λ = 254 nm) as well as selective ¹n, π*-excitation (λ > 347 nm) of the 2,7-diene-carbonyl compounds 12 and 13 give rise to isomerization to the compounds F (25, 28) , exclusively. The intramolecular [2 + 2]-photocycloadditions are shown to be triplet processes. UV.-irradiation (λ > 280 nm) of compounds F (25, 28) furnishes the isomeric products G (26, 29) which photoisomerize to oxetanes of type H (27, 30).     

Site-directed 13C solid-state NMR studies on membrane proteins: strategy and goals toward revealing conformation and dynamics as illustrated for bacteriorhodopsin labeled with [1-13C]amino acid residues

We have so far demonstrated that well-resolved and site-specifically assigned (13)C peaks as recorded by site-directed NMR study on (13)C-labeled membrane proteins can serve as a convenient probe to reveal their local conformation and dynamics. We attempted here to clarify the extent to which (13)C NMR spectra of (13)C-labeled fully hydrated bacteriorhodopsin (bR) as a typical membrane protein are visible or well resolved in the presence of inherent fluctuation motions with frequency of 10(2)-10(8) Hz, especially at the membrane surfaces. Accordingly, we estimated the relative proportion of (13)C NMR signals from the surface areas with and without peak suppression by the accelerated transverse relaxation effect by surface-bound Mn(2+) ions, which could be effective for residues within 8.7 angstroms of the membrane surface. It turned out that the experimental findings are consistent with the predicted amount of amino acid residues under consideration located within 8.7 angstroms of the surface for [1-(13)C]Val- and Ile-labeled bR and also [3-(13)C]Ala-bR. In contrast, (13)C NMR peaks from such surfaces area are almost completely or partially suppressed for [1-(13)C]Gly-, Ala-, Leu-, Phe- and Trp-labeled bR, as a result of plausible interference of the fluctuation frequency with frequency of magic angle spinning (10(4) Hz). We further assigned several (13)C NMR signals of [1-(13)C] Val-, Trp- and Ile-labeled bR on the basis of a variety of site-directed mutants with reference to those of the wild type. Further, we recorded the (13)C NMR of bR in lipid bilayers to search for the optimal conditions to be able to obtain signals with the highest peak intensities and spectral resolution. Backbone dynamics turn out to be essential for recording (13)C NMR spectra so as to escape from motional frequencies of the order of 10(4)-10(5) Hz, either in the direction of accelerated fluctuation or slowed motions in the direction of forming the 2D array.     

Oxysulfide Sm(2)Ti(2)S(2)O(5) as a stable photocatalyst for water oxidation and reduction under visible light irradiation (lambda < or = 650 nm)

A Ti-based oxysulfide, Sm(2)Ti(2)S(2)O(5), was studied as a visible light-driven photocatalyst. Under visible light (440 nm < or = lambda < or = 650 nm) irradiation, Sm(2)Ti(2)S(2)O(5) with a band gap of approximately 2 eV evolved H(2) or O(2) from aqueous solutions containing a sacrificial electron donor (Na(2)S-Na(2)SO(3) or methanol) or acceptor (Ag(+)) without any noticeable degradation. This oxysulfide is, therefore, a stable photocatalyst with strong reduction and oxidation abilities under visible-light irradiation. The electronic band structure of Sm(2)Ti(2)S(2)O(5) was calculated using the plane-wave-based density functional theory (DFT) program. It was elucidated that the S3p orbitals constitute the upper part of the valence band and these orbitals make an essential contribution to the small band gap energy. The conduction and valence bands' positions of Sm(2)Ti(2)S(2)O(5) were also determined by electrochemical measurements. It indicated that conduction and valence bands were found to have satisfactory potentials for the reduction of H(+) to H(2) and the oxidation of H(2)O to O(2) at pH = 8. This is consistent with the results of the photocatalytic reactions.     

Immobilization of ultra-thin layer of monoclonal antibody on glass surface

When preparing an affinity column and a biosensor, it is desirable to immobilize a unimolecular layer of pure protein on a matrix. In this work, we tried to immobilize a monoclonal antibody on a surface of a glass test-tube as a model, to confirm the stability of this ultra-thin layer by an enzyme immunoassay, and to estimate the thickness of the layer on a slide glass by Fourier transform infrared reflection spectrometry. A new test-tube was washed and dried. The tube was filled with 5% 3-aminopropyltriethoxysilane. The 3-aminopropylsilylated surface was treated with glutaraldehyde and 5.6.10(-2) mg/ml solution of a normal mouse monoclonal antibody. The Schiff base between glutaraldehyde and the antibody was further reduced with 7.9.10(-3)% NaBH4. The tube was washed with 0.05% Tween 20 to block non-specific binding. The antibody immobilized on the surface was measured by an enzyme immunoassay based on a reaction of anti-mouse immunoglobulin G labelled with alkaline phosphatase, with which p-nitrophenol was produced from p-nitrophenylphosphate as a substrate. Meanwhile, various amounts of the antibody were immobilized on slide glasses in the same manner. The antibody on each surface was measured by Fourier transform infrared reflection spectrometry. The antibody immobilized under the final conditions was detectable by the enzyme immunoassay, and stable at 4 degrees C for ten days. The antibody on the slide glass was a unimolecular layer, as judged from the Fourier transform infrared spectra referred to -CONH- band semiquantitatively. Thus, we found the optimal conditions for immobilizing an ultra-thin layer of the monoclonal antibody on the glass surface.(ABSTRACT TRUNCATED AT 250 WORDS)     

Studies on stable free radicals. XIX. Copolymerization of N-oxyl biradical with α-chloro-p-xylylene

Copolymerization of N-oxyl biradical with α-chloro-p-xylylene was carried out by varying the feed ratio of α,α′-dichloro-p-xylene which was the precursor of α-chloro-p-xylylene. The structures of the obtained copolymers were determined spectroscopically. The results that the N-oxyl attacked the carbon-bearing chlorine atom of α-chloro-p-xylylene suggest a nucleophilic reactivity of N-oxyl radical. The copolymerization process was also discussed.     

Extraction separation of strontium and yttrium radionuclides by hydrogen heptachlorodicarbollylcobaltate in the presence of benzo-15-crown-5

Extraction of strontium and yttrium by the nitrobenzene solution of H⁺-form of heptachloro-bis-1,2-dicarbollylcobaltate (H⁺B^–) in the presence of benzo-15-crown-5 (B15C5, L) has been investigated. The presence of B15C5 leads to a great synergistic effect for the extraction of strontium and an antagonistic effect for the extraction of yttrium. The extraction constants of Sr²⁺ complexes of B15C5 were determined. The separation factor a(Sr/Y) in the system with B15C5 presents the same order of magnitude as that for 15C5.     

Molecular mobility of lyophilized poly(vinylpyrrolidone) and methylcellulose as determined by the laboratory and rotating frame spin-lattice relaxation times of 1H and 13C

Laboratory- and rotating- frame spin-lattice relaxation times (T(1) and T(1rho)) of (1)H and (13)C in lyophilized poly(vinylpyrrolidone) (PVP) and methylcellulose (MC) are determined to examine feasibility of using T(1) and T(1rho) as a measure of molecular motions on large time scales related to the storage stability of lyophilized formulations. The T(1rho) of proton and carbon was found to reflect the mobility of PVP and MC backbones, indicating that it is useful as a measure of large-time-scale molecular motions. In contrast to the T(1rho), the T(1) of proton measured in the same temperature range reflected the mobility of PVP and MC side chains. The T(1) of proton may be useful as a measure of local molecular motions on a smaller-time-scale, although the measurement is interfered by moisture under some conditions. The temperature dependence of T(1) and T(1rho) indicated that methylene in the MC molecule had much higher mobility than that in the dextran molecule, also indicated that methylene in the PVP side chain had a higher mobility than that in the MC side chain.