A natural protecting group strategy to carry an amino acid starter unit in the biosynthesis of macrolactam polyketide antibiotics

Macrolactam antibiotics are an important class of macrocyclic polyketides that contain a unique nitrogen-containing starter unit. In the present study, a set of starter biosynthetic enzymes in the macrolactam antibiotic vicenistatin was characterized. We found that the protection-deprotection strategy of the aminoacyl-ACP intermediate was critical in this system. On the basis of bioinformatics, the described pathway is also proposed as a common method for carrying amino acids in the biosynthesis of other macrolactam antibiotics.     

Optimisation of the analytical method for octa-, nona- and deca-brominated diphenyl ethers using gas chromatography–quadrupole mass spectrometry and isotope dilution

An analytical method for higher brominated congeners of polybrominated diphenyl ethers (PBDEs) was optimised using a gas chromatograph equipped with an electron impact ionisation-quadrupole mass spectrometer (GC-EI-qMS) and five native PBDEs and three ¹³C₁₂-labelled congeners in biological and environmental samples (mussels, sediment, dust). In the optimised instrumental conditions, abundance and repeatability improved with increase in temperature of the ion source. The instrumental detection limits (IDLs) for BDE-196, BDE-197, BDE-206, BDE-207 and BDE-209 were 0.1, 0.1, 0.2, 0.3 and 0.6?pg, respectively. When compared to the previous reports, the IDLs were the same as for electron capture negative ionisation (ECNI) or EI-double focusing magnetic sector (EI-Sector) mass spectrometer, indicating that sensitive determination could be achieved using a conventional GC-EI-qMS. Validation of the method was carried out by the analysis of reference materials and mussel samples. We confirmed that the concentrations quantified using this method was in the range of reported values for reference materials. Similar concentrations were found in mussels, which were analysed previously by our group. Thus, we conclude that a conventional GC-EI-qMS can be applied for analysis of higher brominated PBDEs in various environmental and biota matrices.     

Effect on carbon lengthening at the side chain terminal of 1 alpha,25-dihydroxyvitamin D3 for calcium regulating activity

A series of analogs of 1 alpha,25-dihydroxyvitamin D3 [1,25-(OH)2D3 (1)] with alkyl substitutions in 26- and 27-positions have been tested for their activity 1) in competing with 1,25-(OH)2D3 for binding to chick intestinal cytosol receptor, 2) in ability for formation of multinucleated cells (MNC) with various osteoclastic cell characteristics from blast cells, and 3) in stimulating bone calcium mobilization in vitamin D-deficient rats. The relative potencies of 1,25-(OH)2D3, 1 alpha,25-dihydroxy-26,27-dimethylvitamin D3 (2), 1 alpha,25-dihydroxy-26,27-diethylvitamin D3 (3), and 1 alpha,25-dihydroxy-26,27-dipropylvitamin D3 (4) in competing for intestinal cytosolic binding were 1:1.1:0.25:0.05. The similar order of the abilities on formation of the multinucleated cells in the same series was observed. In a bone calcium mobilization test with vitamin D-deficient rats, 1 alpha,25-dihydroxy-26,27-dimethylvitamin D3 showed slightly less activity than 1,25-(OH)2D3 at 12 h after administration, but long lasting activity was observed during time course experiments. 1 alpha,25-Dihydroxy-26,27-diethylvitamin D3, and 1 alpha,25-dihydroxy-26,27-dipropylvitamin D3 were found to be much less active than 1,25-(OH)2D3 in a bone calcium mobilization test.     

Synthesis of sulfonyloxy furoxans via hydroxyfuroxan ammonium salts

Furoxans are distinctive heteroaromatic compounds in that they are potentially capable of releasing nitric oxide under physiological conditions. In order to utilize the furoxan scaffold for the development of functional molecules, synthetically relevant functional groups are required for access to diverse furoxans. In this report, a facile route to furoxans with sulfonyloxy groups, which are halide surrogates, has been developed. The key features of this strategy include the synthesis and utilization of bench-stable hydroxyfuroxan salts, the use of sulfonyl anhydrides in the sulfonylation step instead of sulfonyl chlorides, and the photochemical isomerization of one regioisomer to another in order to gain access to both.     

A characterization of second order efficiency in a curved exponential family

Summary The optimality of estimation method is investigated in a curved exponential family. A risk function, which is an extension of a residual sum of squares in regression analysis, is introduced. It is shown that second order efficiency of an estimation method is equivalent to attain the minimum among limiting risks of all estimation methods.     

Role of cholesterol 10-methyl group and effect of "extra" 14-methyl group on silkworm growth and development

In order to establish the functional importance of the 10-methyl group of cholesterol and the planarity of the steroid ring, silkworms (Bombyx mori) were reared on an artificial diet containing 19-norcholesterol (1), 14 alpha-methylcholesterol (3) or 19,19-difluorocholesterol (2). The former two sterols (1 and 3) only partially satisfied the silkworm sterol requirement; growth and development were seriously retarded. The fluorinated sterol (2) was much more deleterious and was totally inadequate in meeting the sterol requirement.     

Hidden fermionic symmetry in conformal topological field theories

We point out that bosonic conformal coset modelsG _l ×G _k /G _l+k for all semi-simple Lie algebrasG have a hidden fermionic symmetry atl=0 (the central charge=0) and may be interpreted as twisted versions of some superconformal theories.     

Visualization of 50 MHz Surface Acoustic Wave Propagation Using Stroboscopic Phase-Shift Interferometry

A Stroboscopic phase-shift interferometry has been developed to visualize surface acoustic wave (SAW) propagation on SAW devices quantitatively. The developed interferometry is a Fizeau-type one with a multi-mode semiconductor laser diode and an optical isolator. With the laser light illuminating stroboscopically, observed interference intensity gives information about average displacements of the vibrations. Fifty MHz SAW propagation on the surface of the SAW device has been measured with the interferometry. Distribution of the SAW along the propagation path has been observed, whose amplitude is 3 nm (p-p). Repetition accuracy evaluated with the root mean square method is 1/2500 of the laser wavelength. The system is useful for estimating and improving performances of micro-devices.Presented at 1996 International Workshop on Interferometry (IWI ‘96), August 27-29, Saitama, Japan.