Mevashuntin, a novel metabolite produced by inhibition of the mevalonate pathway in Streptomyces prunicolor

Inhibition of the mevalonate pathway by an HMG-CoA reductase inhibitor, mevalotin, in Streptomyces prunicolor possessing both mevalonate and MEP pathways resulted in the production of a new metabolite mevashuntin that consisted of conjugated thiazolone and pyranonaphthoquinone moieties.     

Investigation of individual micrometer-size Kosa particle with on-site combination of electron microscope and synchrotron X-ray microscope.

The Kosa (yellow sand) aerosol affects the global environment as well as human health because it migrates from the interior of China to other areas, absorbing various atmospheric elements. Investigation into individual Kosa aerosol particles, which are submicroscopic to several tens of micrometers in diameter, is required to resolving the issue. We installed a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDX) on a synchrotron radiation (SR) beam line and introduced the SR beam into the SEM chamber for combinatorial application of SEM-EDX and SR X-ray fluorescence (SR-XRF) spectrometry to individual particles. It should be noted that detailed topographic observation by SEM and sensitive elemental analysis by SR-XRF, both crucial for individual particle measurement but which previously had to be carried out separately, were jointly performed inside the SEM chamber in this setup. Here, we show that SR-XRF results, in conjunction with SEM images, contributed toward resolving individual particle dispositions. Atmospheric sulfur primarily adheres to calcium in the aerosol particles and the particle surface roughens as a consequence of the chemical reaction between the two elements.     

Application of WET sequence for the detection of the ligand signals resonating close to water

An efficient pulse sequence for observing the ligand signals resonating close to the water signal has been developed by incorporating the WET technique into the saturation transfer difference pulse sequence. Although several pulse sequences have been developed for observing a ligand binding with a protein receptor, the ligand signals resonating close to the water were undetectable owing to the interference of the huge water signal in the samples containing 95% ¹H₂O. On the point of sample preparation, it is preferable to avoid the solvent exchange in the protein samples. In the proposed pulse sequence, a WET sequence is incorporated for the selective suppression of the water resonance. The efficient water suppression and the clear observation of the bound ligand signals close to the water have been demonstrated using the lysozyme‐glucose complex. Copyright © 2009 John Wiley & Sons, Ltd.     

Theoretical studies on magnetic interactions between Cu(II) ions in hydroxypyridone nucleobases

The origin of a ferromagnetic interaction between Cu²⁺ ions in the Cu²⁺–DNA system which reported by Tanaka et al. is examined by using DFT calculations. In order to consider effects of an entanglement and a dis-entanglement of the double helix chain, three types of structural disorders i.e. distance, rotation angle and discrepancy in XY-plane, are considered in the model dimer structure. All calculated results show that J_ab values are weak anti-ferromagnetic couplings. Boltzmann distribution simulation indicates that the high spin (HS) species exist 21% at 1.5 K by thermal excitation within the model structure.     

Unprecedented alkylation of silicon enolates with alcohols via carbenium ion formations catalyzed by tin hydroxide-embedded montmorillonite

The solid acid, tin hydroxide-embedded montmorillonite, catalyzes the unprecedented alkylation of various silicon enolates with primary, secondary and tertiary benzylic alcohols as well as secondary allylic alcohols. The acid catalysis of Sn-Mont was not only higher than that of the other ion-exchanged montmorillonites (M-Mont; M = H, Ti, Fe and Al), but also higher than that of the typical homogeneous acid catalysts such as BF₃·OEt₂, TMSOTf and TfOH.     

An N-protection free ligation of the peptide thioester and the peptide with an N-alkoxy- or N-aryloxyamino group at its N-terminus

Peptides with an N-alkoxy or N-aryloxy amino acid at their N-terminus were synthesized and successfully ligated with a peptide thioester by silver ion activation under a slightly acidic condition without requiring protection of the side chain amino groups. The N-methoxy group was easily cleaved by the SmI₂ reduction in CH₃OH aq. to obtain the desired peptide with a native peptide bond. This method was successfully applied to the synthesis of the human atrial natriuretic peptide showing the efficiency of the novel ligation.     

Fabrication of well‐aligned electrospun nanofibrous membrane based on fluorinated polyimide

We have fabricated novel nanofibrous fluorinated polyimide membranes on a specially designed collector, which is composed of conductive aluminum plates and glass insulator materials and can be removed from the apparatus, using an electrospinning method. We describe the structure and water flux properties of the nanofibrous fluorinated polyimide membranes. The electrospun nanofibers were deposited across the plates and uniaxially aligned to the collector. In addition, the multi‐layer stacked nanofibrous membranes, consisting of three‐dimensionally ordered nanopores, were produced. The pure water fluxes for the stacked membranes were measured, using a stirred dead‐end filtration cell, and were linearly decreased with an increasing deposition time, indicating that the nanopores formed in the nanofibrous membrane were further narrowed due to the regularly accumulated nanofibers. Copyright © 2009 John Wiley & Sons, Ltd.     

Counter-current chromatographic separation of nucleic acid constituents with a hydrophilic solvent system

Nucleic acid constituents such as nucleobases, nucleosides and nucleotides were separated by counter-current chromatography using type J coil planet centrifuge. The separation was performed with a hydrophilic solvent system composed of 1-propanol/800 mM potassium phosphate buffer (pH 7.4) (1:1, v/v) by eluting the lower aqueous phase at a flow-rate of 0.5 ml/min. Eight selected nucleic acid constituents (4.0 mg, 0.5 mg of each), uridine monophosphate (UMP), adenosine monophosphate (AMP), deoxyadenosine monophosphate (dAMP), uridine, urasile, deoxy uridine, adenosine and adenine were well resolved within 160 min.