(C2H10N2)[BPO4F2] — Structural Relations between [BPO4F2]2— and [Si2O6]4—

(C₂H₁₀N₂)[BPO₄F₂] — Strukturbeziehungen zwischen [BPO₄F₂]^2— und [Si₂O₆]^4— Colourless crystals of (C₂H₁₀N₂)[BPO₄F₂] were prepared from mixture of ethylendiamine, H₃BO₃, BF₃ · C₂H₅NH₂, H₃PO₄ and HCl under mild hydrothermal conditions (220 °C). The crystal structure was determined by single crystal methods (triclinic, P1¯ (no. 2), a = 451.85(5) pm, b = 710.20(8) pm, c = 1210.2(2) pm, α = 86.08(1)°, β = 88.52(2)°, γ = 71.74(1)°, Z = 2) and contains infinite tetrahedral zweier‐single‐chains {[BPO₄F₂]^2—} which are isoelectronic (48e^—) with the polyanions {[Si₂O₆]^4—} of the pyroxene family.     

Tritium content as indicator of environmental character on Taiwan Island

Environmental characters have been established by tritium contents in well water, coastal seawater and reservoir water collected from various places around Taiwan island. Tritium concentrations of samples were detected by a liquid scintillation analyzer TRI-CARB-LSC 2550 TR mode, with a low level standard quench curve. After samples were concentrated by electrolysis, tritium concentration was detected in optimum conditions of LLLSA. An electrolytic enrichment technique was also developed with a eurrent density of 100 mA/cm² and 0.4–0.6% (Na₂O₂) electrolyte in concentrated samples. Data observed show a lower tritium concentration for coastal seawater than for wells in the same area. The tritium concentration ratio of well and coastal seawater on the western side of Taiwan is 4.000 and on the eastern side 5.801. Tritium content of reservoir water is related to the logarithm of effective volume capacity.     

Boomerang‐Type Substitution Reaction: Reactivity of Fullerene Epoxides and a Halofullerenol

The C_s‐symmetric fullerene chlorohydrin C₆₀(Cl)(OH)(OOtBu)₄ reacts with 4‐dimethylaminopyridine (DMAP) and 1,4‐diazabicyclo[2.2.2]octane (DABCO) to yield two isomers with the formula C₆₀(O)(OOtBu)₄ in good yields. These isomers differ with respect to the location of the epoxy functionality. The one from DMAP is C_s symmetric, whereas that from DABCO is C₁ symmetric with the epoxy group on the central pentagon. Two different mechanisms are proposed to explain the chemoselectivity of these reactions. The reaction with DMAP involves single‐electron transfer as the key step; DMAP acts as the electron donor. A combination of an oxygen‐atom shift and S_N2′′ processes (boomerang substitution) are responsible for the formation of isomer with DACBO. Various related reactions support the proposed mechanisms. The structures of new fullerene derivatives were determined by spectroscopy, single‐crystal X‐ray analysis, and chemical correlation experiments.     

Fluorescent polymer cubosomes and hexosomes with aggregation-induced emission

Fluorescent polymer cubosomes and hexosomes with aggregation-induced emission (AIE) were prepared from amphiphilic block copolymers PEG-b-PTPEMA where the hydrophobic block PTPEMA was a polymethacrylate with tetraphenylethene (TPE) as the AIE side group. Four highly asymmetric block copolymers with hydrophilic block weight ratio f_PEG ≤ 20% were synthesized. Cubosomes and hexosomes with strong fluorescence emission were obtained by nanoprecipitation of polymers with f_PEG < 9% in dioxane/water and THF/water systems. Their ordered internal structures were studied by electron microscopy (cryo-EM, SEM and TEM) and the X-ray scattering technique (SAXS). To elucidate the formation mechanisms of these inverted colloids, other parameters influencing the morphologies, like the water content during self-assembly and the organic solvent composition, were also investigated. This study not only inspires people to design novel building blocks for the preparation of functional cubosomes and hexosomes, but also presents the first AIE fluorescent polymer cubosome and hexosome with potential applications in bio-related fields.

Fluorescent Im$\bar{3}$m cubosome and P6mm hexosome with aggregation-induced emission (AIE) were reported, which were formed by amphiphilic block copolymers PEG-b-PTPEMA. The length of hydrophobic block PTPEMA was adjusted to control morphology formation.     

Ring-opening reaction of methylenecyclopropanes with LiCl, LiBr or NaI in acetic acid

The methylenecyclopropanes 1 react with LiCl, LiBr or NaI at 80 °C to give the corresponding gem-disubstituted homoallylic halides 2 in good to excellent yields in acetic acid. In some cases, the ring-opening reaction can be completed within 5 min to give the corresponding gem-disubstituted homoallylic halides in high yields.     

Production of 1,3-propanediol by Klebsiella pneumoniae

1,3-Propanediol (1,3-PD) has numerous applications from polymers to cosmetics, foods, lubricants, and medicines. Recently, there are strong industrial interests in a new kind of polyester, polytrimethylene terephthalate, with 1,3-PD as a monomer. This new polyester shows significant promise for use in carpeting and textiles. In this article we introduce a mild aerobic fermentation process using a strain screened from Klebsiella pneumoniae ATCC 25955, which is insensitive to oxygen, to produce 1,3-PD. We also describe a two-step fermentation process starting with glucose that was converted into glycerol with a glycerol-producing yeast, followed by K. pneumoniae that converts glycerol into 1,3-PD without intermediate isolation and purification of glycerol.     

The neomycin biosynthetic gene cluster of Streptomyces fradiae NCIMB 8233: characterisation of an aminotransferase involved in the formation of 2-deoxystreptamine

The biosynthetic gene cluster of the 2-deoxystreptamine (DOS)-containing aminoglycoside antibiotic neomycin has been cloned for the first time by screening of a cosmid library of Streptomyces fradiae NCIMB 8233. Sequence analysis has identified 21 putative open reading frames (ORFs) in the neomycin gene cluster (neo) with significant protein sequence similarity to gene products involved in the biosynthesis of other DOS-containing aminoglycosides, namely butirosin (btr), gentamycin (gnt), tobramycin (tbm) and kanamycin (kan). Located at the 5'-end of the neo gene cluster is the previously-characterised neomycin phosphotransferase gene (apH). Three genes unique to the neo and btr clusters have been revealed by comparison of the neo cluster to btr, gnt, tbm and kan clusters. This suggests that these three genes may be involved in the transfer of a ribose moiety to the DOS ring during the antibiotic biosynthesis. The product of the neo-6 gene is characterised here as the L-glutamine : 2-deoxy-scyllo-inosose aminotransferase responsible for the first transamination in DOS biosynthesis, which supports the assignment of the gene cluster.     

Electrostatic recognition and induced fit in the kappa-PVIIA toxin binding to Shaker potassium channel

Brownian dynamics (BD) and molecular dynamics (MD) simulations and electrostatic calculations were performed to study the binding process of kappa-PVIIA to the Shaker potassium channel and the structure of the resulting complex. BD simulations, guided by electrostatic interactions, led to an initial alignment between the toxin and the channel protein. MD simulations were then carried out to allow for rearrangements from this initial structure. After approximately 4 ns, a critical "induced fit" process was observed to last for approximately 2 ns. In this process, the interface was reorganized, and side chains were moved so that favorable atomic contacts were formed or strengthened, while unfavorable contacts were eliminated. The final complex structure was stabilized through electrostatic interactions with the positively charged side chain of Lys7 of kappa-PVIIA deeply inserted into the channel pore and other hydrogen bonds and by hydrophobic interactions involving Phe9 and Phe23 of the toxin. The validity of the predicted structure for the complex was assessed by calculating the effects of mutating charged and polar residues of both the toxin and the channel protein, with the calculated effects correlating reasonably well with experimental data. The present study suggests a general binding mechanism, whereby proteins are pre-aligned in their diffusional encounter by long-range electrostatic attraction, and nanosecond-scale rearrangements within the initial complex then lead to a specifically bound complex.     

Gold nanoparticles: catalyst for the oxidation of NADH to NAD(+)

Nicotinamide adenine dinucleotide is an important coenzyme involved in the production of ATP, the fuel of energy, in every cell. It alternates between the oxidized form NAD(+) and the reduced form dihydronicotinamide adenine dinucleotide (NADH) and serves as a hydrogen and electron carrier in the cellular respiratory processes. In the present work, the catalytic effect of gold nanoparticles on the oxidization of NADH to NAD(+) was investigated. The addition of gold nanoparticles was found to quench the NADH fluorescence intensities but had no effect on the fluorescence lifetime. This suggested that the fluorescence quenching was not due to coupling with the excited state, but due to changing the ground state of NADH. The intensity of the 340 nm absorption band of NADH was found to decrease while that of the 260 nm band of NAD(+) was found to increase as the concentration of gold nanoparticles increased. This conversion reaction was further supported by nuclear magnetic resonance and mass spectroscopy. The effect of the addition of NADH was found to slightly red shift and increase the intensity of the surface plasmon absorption band of gold nanoparticles at 520 nm. This gives a strong support that the conversion of NADH to NAD(+) is occurring on the surface of the gold nanoparticles, i.e. NADH is surface catalyzed by the gold nanoparticles. The catalytic property of this important reaction might have important future applications in biological and medical fields.     

Intramolecular metathesis of a vinyl group with vinylidene C=C double bond in Ru complexes

The cationic complex {[Ru]=C=CHCPh2CH2CH=CH2}BF4 (3a, [Ru] = (eta5-C5H5)(PPh3)2Ru) in solution transforms to {[Ru]=C=CHCH2CPh2CH=CH2}BF4 (4a) via a new metathesis process of the terminal vinyl group with the C=C of the vinylidene group which is confirmed by 13C labeling studies. This transformation is irreversible as revealed by deuteration and decomplexation studies. The cationic complex {[Ru]=C=CHCPh2CH2CMe=CH2}BF4 (3b) undergoes a cyclization process yielding 6b containing a eta2-cyclic allene ligand which is fully characterized by single-crystal X-ray diffraction analysis. Analogous complexes 4a' and 6b' ([Ru] = (eta5-C5H5)(dppe)Ru) containing dppe ligands were similarly obtained from protonation of the corresponding acetylide complexes via formation of vinylidene intermediate. Protonation of the acetylide complex containing a terminal alkynyl group [Ru]-CCCPh2CH2CCH (2c) generates the vinylidene complex {[Ru]=C=CHCPh2CH2CCH}BF4 (3c) which again undergoes an irreversible transformation to give {[Ru]=C=CHCH2CPh2CCH}BF4 (4c) possibly via a pi-coordinated alkynyl complex followed by hydrogen and metal migration. No similar transformation is observed for the analogous dppe complex 3c'. With an extra methylene group, complex {[Ru]=C=CHCPh2CH2CH2CH=CH2}BF4 (3d) and complex {[Ru]=C=CHCPh2CH2Ph}BF4 (3e) are stable. The presence of a gem-diphenylmethylene moiety at the vinylidene ligand with the appropriate terminal vinyl or alkynyl group along with the correct steric environment implements such a novel reactivity in the ruthenium vinylidene complexes.