Four-color hole burning spectra of phenol/ammonia 1:3 and 1:4 clusters

The hole burning spectra of phenol/ammonia (1:3 and 1:4) clusters were measured by a newly developed four-color (UV-near-IR-UV-UV) hole burning spectroscopy, which is a kind of population labeling spectroscopy. From the hole burning spectra, it was found that single species is observed in an n = 3 cluster, while three isomers are observed simultaneously for n = 4. A possibility was suggested that the reaction efficiency of the hydrogen transfer from the electronically excited phenol/ammonia clusters, which was measured by a comparison with the action spectra of the corresponding cluster, depends on the initial vibronic levels.     

Sequential flow-injection spectrophotometric determination of iron(II) and iron(III) by copper(II)-catalyzed reaction with Tiron

A flow injection method for the sequential determination of iron(II) and iron(III) was developed. It is based on the differential reaction kinetics of iron(II) and iron(III) with Tiron in a double-injection FI system. The proposed method employs the accelerating action of copper(II) for the oxidation of iron(II) in the presence of Tiron. A linear calibration graph is obtained for iron (II) and iron(III) in the concentration range 1.8 × 10^–5– 1.8 × 10^–4 mol/L; the throughput of samples is 30 injections/h.     

Selective uptake of toxic elements by an amorphous titanium dioxide ion exchanger

The ion-exchange selectivities for oxoanions of some toxic elements and halogens were studies on an amorphous hydrous titanium dioxide (Am-HTDO) as a function of OH^– and anion concentrations in chloride and nitrate media. The adsorption isotherm was of the Langmuir type. The selectivity sequence increased in the order of ClO ₃ ^– <BrO ₃ ^– <IO ₃ ^– SeO ₃ ^2– <TeO ₃ ^2– <As(OH) ₄ ^– . IO ₃ ^– was efficiently separated from ClO ₃ ^– and BrO ₃ ^– . As(OH) ₄ ^– and SeO ₃ ^2– were selectively separated from seawater. Such high selectivity of Am-HTDO may provide a new concentration technique of these toxic elements in environmental materials.Synthetic inorganic ion-exchange materials LIX.     

1-methylidenesqualene and 25-methylidenesqualene as active-site probes for bacterial squalene:hopene cyclase

1-methylidenesqualene and 25-methylidenesqualene were converted to 30-methylidenehop-22(29)-ene by squalene:hopene cyclase from Alicyclobacillus acidocaldarius. It was remarkable that both analogues generated the same product. The hopanyl intermediate cation, stabilized by the methylidene residue, enabled a rotation of the isobutenyl group at C-21 prior to the final proton elimination. In contrast, in the formation of hop-22(29)-ene, the final proton abstraction takes place regiospecifically from the Z-methyl group, which was verified by cyclization of (1,1,1,24,24,24-(2)H(6))squalene into (23,23,23,30,30,30-(2)H(6))hop-22(29)-ene. [reaction: see text]     

Vibrational energy redistribution in jet-cooled hydrogen-bonded phenols

Dispersed fluorescence spectra of jet-cooled hydrogen-bonded phenols have been observed by excitation of intra- and inter-molecular vibrational levels. The spectra show that vibrational energy redistribution occurs from the excited vibronic level into intermolecular vibrational modes. Energy redistribution within the intermolecular vibrational modes was also found.     

Effective form of sulfoquinovosyldiacyglycerol (SQDG) vesicles for DNA polymerase inhibition

Sulfoquinovosyldiacyglycerol (SQDG) has a wide range of biological activities that make it an attractive compound for the development of new drugs. Chemically synthesized beta-SQDG-C(18:0) (1,2-di-O-stearoyl-3-O-(6-deoxy-6-sulfo-beta-d-glucopyranosyl)-sn-glycerol), for example, has a potent inhibitory effect on DNA polymerases. We investigated the properties of the vesicle form of beta-SQDG-C(18:0) as the monomer has low solubility in water. The structure of the beta-SQDG-C(18:0) vesicles are highly influenced by NaCl concentration in preparation process. At low NaCl concentrations, the beta-SQDG-C(18:0) vesicles have high surface curvature and form small unilamellar vesicles. Increases in NaCl concentration, resulted in decreased surface curvature and a tendency for beta-SQDG-C(18:0) to form large multilamellar vesicles. The small unilamellar vesicles showed a potent inhibitory effect on DNA polymerase beta, whereas the large multilamellar vesicles had no such effect. We investigated further the relationship between vesicle size and activity by preparing smaller vesicles (262, 99 and 43 nm in diameter) using an extrusion technique. These smaller vesicles had a greater inhibitory effect on DNA polymerase beta activity than non-extruded vesicles. beta-SQDG-C(18:0) vesicles, especially those of small size, were effective in DNA polymerase inhibition and are expected to have high applicability in DNA polymerase study.     

Biosynthesis of polyhydroxyalkanoate (PHA) copolymer from fructose using wild-type and laboratory-evolved PHA synthases

Eleven laboratory-evolved polyhydroxyalkanoate (PHA) synthases which originated from Pseudomonas sp. 61-3 enzyme (PhaC1(Ps)), together with the wild-type enzyme, were applied for PHA synthesis from fructose using Ralstonia eutropha PHB(-)4 as a host strain. The evolved PhaC1(Ps) mutants had amino acid substitution(s) at position 325 and/or position 481. In these mutants, serine-325 (S325) was replaced by cysteine (C) or threonine (T), while glutamine-481 (Q481) was replaced by lysine (K), methionine (M) or arginine (R). All recombinant strains harboring the genes of the evolved PhaC1(Ps) mutants produced a significantly increased amount of PHA (55-68 wt.-%) compared with the one harboring the wild-type gene (49 wt.-%). Particularly, those evolved PhaC1(Ps) mutants having multiple amino acid substitutions showed higher activities for PHA synthesis. Characterization of the PHA by NMR spectroscopy revealed that they were copolymers consisting of (R)-3-hydroxybutyrate (98-99 mol-%) and medium-chain-length comonomers (1-2 mol-%). This study also confirmed that amino acid substitution at position 481 in PhaC1(Ps) led to an increasing molecular weight of PHA. The number-average molecular weight (Mn) of PHA (Mn = 240,000) synthesized by the evolved PhaC1(Ps) (Q481K) mutant was 4.6-fold greater than that (Mn = 52,000) synthesized by the wild-type enzyme.     

Total synthesis of scytophycin C. 1. Stereoselective syntheses of the C(1)-C(18) segment and the C(19)-C(31) segment

[structure: see text] Stereoselective total synthesis of scytophycin C, a marine 22-membered macrolide displaying potent activity against a variety of human carcinoma cell lines, has been reported in which the polypropionate structure bearing contiguous asymmetric centers was stereospecifically constructed by using new acyclic stereocontrol. This paper describes stereoselective syntheses of the C(1)-C(18) segment (Segment A) including a trans-disubstituted dihydropyran ring and the C(19)-C(31) segment (Segment B) having eight stereogenic centers.     

Binding constants of calcium and/or magnesium electrolytes and aggregation numbers in oil-in-water type microemulsions formed by an amphoteric surfactant

The effects of anti-symmetric electrolytes (CaCl₂, Ca(SCN)₂, MgCl₂, and/or Mg(SCN)₂) and pH on the phase behavior, the -potential, the hydrodynamic diameter and the surface charge density of an oil-inwater type (O/W-type) microemulsion formed in solutions of an amphoteric surfactant (N ,N -dimethyl-N -lauroyllysine, DMLL)/n-octane/1-pentanol/brine have been examined. The formation of the microemulsion in the presence of CaCl₂ and/or Ca(SCN)₂ is of Winsor-type with an increase in the concentration of 1-pentanol. Particularly, microemulsion is not formed by the addition of Ca(SCN)₂ in a pH region less than 2.6. The -potential and the surface charge density of the microemulsion in the presence of CaCl₂ decrease with an increase in pH and show slightly positive values in the isoelectric region (pH 5-7), while, in the presence of Ca(SCN)₂, the -potential and the surface charge density show negative values in the same region at which the net charge of DMLL molecules becomes almost zero. The hydrodynamic diameters in the presence of CaCl₂ show a maximum value around pH 2.5, whereas, in the presence of Ca(SCN)₂, the minimum value is around pH 5.5. Similar tendencies are recognized in results for the -potential, the hydrodynamic diameter and the surface charge density of the O/W-type microemulsion in the presence of MgCl₂ and Mg(SCN)₂. A new formula to estimate the binding constants (K) of Ca²⁺, Mg²⁺, Cl^–, and SCN^– to the hydrophilic groups in DMLL molecules and the adsorption density of DMLL molecules on the oil/water interface (N) in the presence of antisymmetric electrolytes has been derived.K for Ca²⁺, Mg²⁺, Cl^–, and SCN^– was found to beK _Ca=0.12M^–1,K _Mg=0.14 M^–1,K _Cl=0.0084±0.0016 M^–1, respectively.N for DMLL molecules in the presence of CaCl₂, Ca(SCN)₂, MgCl₂ and/or Mg(SCN)₂ was found to be 0.50 nm^–2, 0.38 nm^–2, 0.44 nm^–2, and 0.47 nm^–2, respectively; and the surfactant (DMLL) numbers per O/W-type microemulsion droplet change from a few hundreds to a few thousands with changing pH. The larger the hydrodynamic diameter of the O/W-type microemulsion, the greater the number of DMLL molecules adsorbed on the O/W-type microemulsion surfaces.     

Synthetic studies on β-lactam antibiotics. 19. Synthesis of 3′-nor-type 1-oxacephems

Synthesis of optically active 3′-nor-type 1-oxacephems from 6-APA was described. $\text{p}$-Nitrobenzyl 7β-amino-3-chloro-7α-methoxy-1-oxa-3-cephem-4-carboxylate $\text{39}$ was also prepared.