Accurate measurement of atmospheric helium isotopes.

We have developed an analytical system to measure atmospheric 3He/4He ratios precisely by using a static vacuum operation mass spectrometer and an ultrahigh-vacuum purification line. After purification of the sample, helium was introduced into the mass spectrometer. Ion beams of 3He and 4He were measured at the same time by a double collector system. A resolving power of about 700 at the 5% level of the peak height was attained for the complete separation of 3He ions from those of HD and H3. Repeated analysis of a sample calibrated against a standard showed a precision of about 0.2% error margin (2sigma). This system has been applied to evaluating the 3He/4He ratio of He Standard of Japan (HESJ), and for the assessment of the atmospheric variation of latitude. The observed 3He/4He ratio of HESJ, 20.405+/-0.040Rair (2sigma) agrees well with the value of 20.408+/-0.044Rair by Lupton and Evans, but is smaller than the recommended value of 20.63+/-0.10Rair in a literature. Air samples collected from 45 to 20 degrees N in the Far East showed a slight decrease of the 3He/4He ratio with latitude. Even though the variation is attributable to an experimental artifact, it may not preclude the possibility that the anthropogenic release of crustal 4He is significant in the high-latitude region of the northern hemisphere.     

Purification and characterization of exo-type cellouronate lyase

A bacterial strain, Brevundimonas sp. SH203, has an ability to degrade cellouronate, β-(1→4)-linked polyglucuronic acid sodium salt, which is artificially prepared from regenerated cellulose by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation. In a previous paper, an endo-type cellouronate lyase (CUL-I) has been isolated from the strain. In this paper, we purified another cellouronate lyase, CUL-II, from cell-free extracts of Brevundimonas sp. SH203. CUL-II was a monomeric protein with a molecular mass of 56 kDa by size exclusion chromatography and 62 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and most active at pH 7.5. CUL-II formed monomers in a small quantity from cellouronate without forming any intermediate oligomers, whereas it degraded C4′–C5′ unsaturated cellouronate dimer more easily. Thus, CUL-II behaves as an exo-type lyase in degradation of cellouronate. When CUL-I and CUL-II were simultaneously treated to cellouronate, it was degraded to monomers more efficiently than treatment with one enzyme alone, CUL-I or CUL-II. Hence, cellouronate is synergistically degraded to monomers by Brevundimonas sp. SH203 by endo- and exo-type lyases, CUL-I and CUL-II, respectively.     

Rhodium(I)-catalyzed borylation of nitriles through the cleavage of carbon-cyano bonds

The reaction of aryl cyanides with diboron in the presence of a rhodium/Xantphos catalyst and DABCO affords arylboronic esters via carbon-cyano bond cleavage. This unprecedented mode of reactivity for a borylrhodium species allows the regioselective introduction of a boryl group in a late stage of synthesis.     

Synchrotron X-ray, photoluminescence, and quantum chemistry studies of bismuth-embedded dehydrated zeolite Y

For the first time, direct experimental evidence of the formation of monovalent Bi (i.e., Bi(+)) in zeolite Y is provided based on the analysis of high-resolution synchrotron powder X-ray diffraction data. Photoluminescence results as well as quantum chemistry calculations suggest that the substructures of Bi(+) in the sodalite cages contribute to the ultrabroad near-infrared emission. These results not only enrich the well-established spectrum of optically active zeolites and deepen the understanding of bismuth related photophysical behaviors, but also may raise new possibilities for the design and synthesis of novel hybrid nanoporous photonic materials activated by other heavier p-block elements.     

Highly sensitive detection of platelet-derived growth factor on a functionalized diamond surface using aptamer sandwich design

Aptamer-based fluorescence detection of platelet-derived growth factor (PDGF) on a functionalized diamond surface was demonstrated. In this work, a sandwich design based on the ability of PDGF to bind with aptamers at its two available binding sites was employed. It was found that this sandwich design approach significantly increases the fluorescence signal intensity, and thereby a very low detection limit of 4 pM was achieved. The effect of the ionic strength of MgCl(2) buffer solution was also investigated, and the most favourable binding for PDGF-BB occurred at a Mg(2+) concentration of 5.5 mM. Since the aptamers bind to the target PDGF with high affinity, fluorescence detection exhibited high selectivity towards different biomolecules. The high reproducibility of detection was confirmed by performing three cycles of measurements over a period of three days.     

Homochiral 1D helical chain based on an achiral Cu(II) complex

Self-assembly of an achiral [Cu(L)] complex produced a homochiral helical chain [Cu(L)](3)·2H(2)O (1) (L = 2-dimethylaminoethyl(oxamato)). Interestingly, complex 1 obtained in our laboratory exhibits only a left-handed helical chain without any chiral source. Single-crystal X-ray analysis revealed the absolute structure and homochirality of its helical chain structure in the space group of P3(2). Solid-state circular dichroism (CD) spectra confirmed the high enantio excess of the crystals obtained in different synthesis batches. Magnetic susceptibility measurements reveal a relatively strong intrachain antiferromagnetic interaction between Cu(II) centers via an oxamato bridge (J = -74.4 cm(-1)).     

Non-enzymatic diastereoselective asymmetric desymmetrization of 2-benzylserinols giving optically active 4-benzyl-4-hydroxymethyl-2-oxazolidinones: asymmetric syntheses of α-(hydroxymethyl)phenylalanine,N-Boc-α-methylphenylalanine,cericlamine and BIRT-377

A reaction of (S)-2-benzyl-2-(α-methylbenzyl)amino-1,3-propanediol (S)-4a and 2-chloroethyl chloroformate, and the subsequent addition of DBU gave (4R,αS)-4-benzyl-4-hydroxymethyl-3-(α-methylbenzyl)-2-oxazolidinone (4R)-5a (92% de) via a diastereoselective asymmetric desymmetrization process. Debenzylation of (4R)-5a using trifluoromethanesulfonic acid and anisole in MeNO₂ gave (R)-4-benzyl-4-hydroxymethyl-2-oxazolidinone (R)-15a, which was converted into (R)-(α-hydroxymethyl)phenylalanine (7) in two steps. N-Boc-α-methylphenylalanine (8), cericlami0ne (9) and BIRT-377 (10) were also synthesized using these asymmetric desymmetrization and debenzylation.     

Synthesis of Au-based porous magnetic spheres by selective laser heating in liquid

We report the synthesis of Au-based submicrometer-sized spherical particles with uniform morphology/size and integrated porosity-magnetic property in a single particles. The particles are synthesized by a two-step process: (a) selective pulsed laser heating of colloidal nanoparticles to form particles with Au-rich core and Fe-rich shell and (b) acid treatment which leads to formation of porous architecture on particle surface. The simple, fast, inexpensive technique that is proposed demonstrates very promising perspectives for synthesis of composite particles.     

General bottom-up construction of spherical particles by pulsed laser irradiation of colloidal nanoparticles: a case study on CuO

The development of a general method to fabricate spherical semiconductor and metal particles advances their promising electrical, optical, magnetic, plasmonic, thermoelectric, and optoelectric applications. Herein, by using CuO as an example, we systematically demonstrate a general bottom-up laser processing technique for the synthesis of submicrometer semiconductor and metal colloidal spheres, in which the unique selective pulsed heating assures the formation of spherical particles. Importantly, we can easily control the size and phase of resultant colloidal spheres by simply tuning the input laser fluence. The heating-melting-fusion mechanism is proposed to be responsible for the size evolution of the spherical particles. We have systematically investigated the influence of experimental parameters, including laser fluence, laser wavelength, laser irradiation time, dispersing liquid, and starting material concentration on the formation of colloidal spheres. We believe that this facile laser irradiation approach represents a major step not only for the fabrication of colloidal spheres but also in the practical application of laser processing for micro- and nanomaterial synthesis.     

Total Synthesis of Marine Eicosanoid (−)‐Hybridalactone

(?)‐Hybridalactone ( 1 ) is a marine eicosanoid isolated from the red alga Laurencia hybrida. This natural product contains cyclopropane, cyclopentane, 13‐membered macrolactone and epoxide ring systems incorporating seven stereogenic centers. Moreover, this compound has an acid‐labile skipped Z,Z‐diene motif. In this paper, we report on the total synthesis of (?)‐hybridalactone ( 1 ). The unique eicosanoid (?)‐hybridalactone ( 1 ) was synthesized starting from optically active γ‐butyrolactone 2 in a linear sequence comprising 21 steps with an overall yield of 21.9 %. A key step in the synthesis of (?)‐hybridalactone ( 1 ) is the methyl phenylsulfonylacetate‐mediated one‐pot synthesis of the cis‐cyclopropane‐γ‐lactone derivative. This reaction provided an efficient and stereoselective access to cis‐cyclopropane‐γ‐lactone 12 . Further elaboration of the latter compounds through desulfonylation, epoxidation, oxidation, Wittig olefination and Shiina macrolactonization afforded (?)‐hybridalactone.