Synthesis of carbon nanotubes on Ni-alloy and Si-substrates using counterflow methane–air diffusion flames

We have conducted an experimental study to investigate the synthesis of multi-walled carbon nanotubes (CNTs) in counterflow methane–air diffusion flames, with emphasis on effects of catalyst, temperature, and the air-side strain rate of the flow on CNTs growth. The counterflow flame was formed by fuel (CH₄ or CH₄ + N₂) and air streams impinging on each other. Two types of substrates were used to deposit CNTs. Ni-alloy (60% Ni + 26% Cr + 14% Fe) wire substrates synthesized curved and entangled CNTs, which have both straight and bamboo-like structures; Si-substrates with porous anodic aluminum oxide (AAO) nanotemplates synthesized well-aligned, self-assembled CNTs. These CNTs grown inside nanopores had a uniform geometry with controllable length and diameter. The axial temperature profiles of the flow were measured by a 125 μm diameter Pt/10% Rh–Pt thermocouple with a 0.3 mm bead junction. It was found that temperature could affect not only the success of CNTs synthesis, but also the morphology of synthesized CNTs. It was also found, against previous general belief, that there was a common temperature region (1023–1073 K) in chemical vapor deposition (CVD) and counterflow diffusion flames where CNTs could be produced. CNTs synthesized in counterflow flames were significantly affected by air-side strain rate not through the residence time, but through carbon sources available for CNTs growth. Off-symmetric counterflow flames could synthesize high-quality CNTs because with this configuration carbon sources at the fuel side could easily diffuse across the stagnation surface to support CNTs growth. These results show the feasibility of using counterflow flames to synthesize CNTs for particular applications such as fabricating nanoscale electronic devices.     

Electronic transport properties and Microstructures of TiO2:Co magnetic semiconductors

TiO₂:Co thin films of high Co concentration were investigated by the high resolution transmission electron microscopy, physical property measurement system and energy dispersive X-ray. The as-deposited films are amorphous magnetic semiconductors and we did not find any Co metal particles in them. The electronic transport process in the low-temperature range below 80 K could be described by the spin-dependent variable-range-hopping process. However, after the samples were annealed at 300 °C, large amounts of Co metal particles were observed to connect each other and the films show a metallic behavior. The origin of ferromagnetism of the thin films is also discussed.     

The Flexibility of the Non-Conservative Region at the C Terminus of <Emphasis Type="SmallCaps">d</Emphasis>-Hydantoinase from <Emphasis Type="Italic">Pseudomonas putida</Emphasis> YZ-26 is Extremely Limited

We previously reported that a deletion mutant (P478) with a residue Arg deleted at the C terminus of d-hydantoinase (P479) from Pseudomonas putida YZ-26 was dissociated into the monomer from its dimeric state. Based on the above result, a series of mutants of the enzyme with the C-terminal residues either deleted or substituted were prepared. The size-exclusion chromatography and bioactivity assay show that a C-terminal-substituted enzyme (R479D) and several truncated mutants (P478, P477, P476, and P475) are dissociated into the monomeric state as well, but their activities are largely retained. In contrast, two other mutants (R474 and R479A) are expressed in the form of random aggregates without any activity. Our experiments demonstrate that only the last four amino acids (-PVQR) at the C terminus of the enzyme can be deleted without seriously affecting its activity, although the enzyme is dissociated from a dimer into a monomer. These mutants also reveal some unique properties such as the enzymatic activity in vivo or in vitro, the effect of divalent metal ions, and the thermostability etc. in comparison to wild-type enzyme (P479). In addition, the three-dimensional structural modeling shows that the intact structure of the enzyme is essential, and the flexibility of the non-conservative region at the C terminus of the enzyme is quite limited.     

Novel 2,7-substituted pyrene derivatives: syntheses, solid-state structures, and properties

A novel series of pyrene derivatives 3-6 functionalized with different aromatic substituents at 2,7-positions of the pyrene core have been readily synthesized by Suzuki coupling reactions. Single crystals suitable for X-ray crystallographic analysis of compounds 3-6 were all successfully obtained. The optical, electrochemical, and thermal properties of these newly synthesized compounds were thoroughly investigated and discussed. Theoretical calculation was adopted to study the geometric and electronic structure of compounds 3-6. Additionally, preliminary studies demonstrated that field-effect transistors using compound 3, 5, and 6 performed as p-type semiconductors, in which a field-effect mobility as high as 0.018 cm² V⁻¹ s⁻¹ and current on/off ratio of 10⁶ were achieved from compound 6.     

有机硅及其改性聚合物膜用于有机溶剂水溶液的渗透汽化分离

采用室温固化硅橡胶及其它三种改性硅氧烷聚合物制成渗透汽化膜,分离丙酮(A),丁酮(B)、乙醇(E)及异丙醇(P)等有机物的水溶液。结果表明,随着透过温度提高、透量成指数关系增大,但对分离系数影响甚小。透量大小顺序为A>B>E>P,分离系数大小顺序为A>B>P>E,当膜材料中(CH_3)_2SiO链节含量由70%上升到100%时,有机物的透量及分离系数同时增加。     

Measurement of deamidation of intact proteins by isotopic envelope and mass defect with ion cyclotron resonance Fourier transform mass spectrometry

After synthesis and folding, proteins undergo many post-synthetic modifications, including cleavage, oxidation, glycosylation, methylation, racemization, phosphorylation, and deamidation. Of these modifications, non-enymatic deamidation is the most prevalent. Each asparaginyl and glutaminyl residue in a protein is a miniature molecular clock that deamidates with a genetically determined half-time. These half-times vary from a few hours to more than a century, depending on a primary, secondary, tertiary, and quaternary structure near the amide residue. It has been suggested that these clocks regulate many biological processes. A few such processes have been discovered. These discoveries have been difficult because deamidation is inconvenient to measure. While most post-synthetic changes are easily measured by mass spectrometry, deamidation increases molecular mass by only one nominal Dalton, so the deamidated isotopic envelope overlaps the undeamidated isotopic envelope. While peptide deamidation rate determination through deconvolution of these envelopes has been accomplished for several hundred peptides, deconvolution becomes more difficult as the molecular weight increases. In high-resolution mass spectrometers, this deconvolution is possible for larger molecules and an alternative method based on the 19 mDa mass defect between the deamidated envelope and the isotopic envelope of protein fragments can also be utilized. We herein report a comparison of the envelope deconvolution and the mass defect methods for measurement of deamidation in human eye lens crystallins, with special emphasis on betaB2 crystallin and gammaS crystallin. Measurement of extent of deamidation of betaB2 crystallin in a 7 Tesla ion cyclotron resonance Fourier transform mass spectrometer is found to be accurate to a relative standard deviation in a single measurement of about 4% for each method. The envelope deconvolution method is further illustrated by detection of deamidation in intact gammaS crystallin, a 20 904 Da protein, and discovery of the principal gammaS deamidation site.     

Cyclopenicillone, a unique cyclopentenone from the cultures of Penicillium decumbens

Cyclopenicillone (1), possessing a unique 2,5-dimethylcyclopent-2-enone carbon skeleton, has been isolated from the cultures broth of the fungus Penicillium decumbens. The structure and absolute configuration of 1 were elucidated using a combination of NMR spectroscopy, CD data and computational approaches. Cyclopenicillone (1) demonstrated a dose-dependent (10-100 μM) inhibition against LPS-induced NO production in RAW264.7 macrophages.     

Two-photon induced luminescence, singlet oxygen generation, cellular uptake and photocytotoxic properties of amphiphilic Ru(II) polypyridyl-porphyrin conjugates as potential bifunctional photodynamic therapeutic agents

Two Ru(II) polypyridyl-porphyrin and Zn(II) porphyrin conjugates (Ru-L and Ru-Zn-L) have been synthesized and their photophysical properties studied. The two conjugates, which contained a hydrophobic tetraphenylporphyrin L conjugated via an acetylide linker at its β-position with a hydrophilic Ru(II) polypyridyl complex, showed high singlet oxygen quantum yields (>70%) and substantial two-photon absorption cross-sections (~500 GM). Ru-L gave strong emissions at ~660 and ~733 nm through linear or two-photon excitation. Solvatochromism was observed in the fluorescence spectra of Ru-L and Ru-Zn-L, where in less polar solvents (i.e., toluene and dichloromethane) their fluorescence emissions became slightly blue-shifted with a 3-fold reduction in intensity relative to those observed in polar solvents (i.e., acetonitrile and methanol). Cell-based studies of these complex conjugates were conducted using human nasopharyngeal carcinoma HK-1 and cervical carcinoma HeLa cells on which Ru-L showed rapid cellular uptake, low dark-cytotoxicity, and high photo-cytotoxicity. Furthermore, Ru-L can be excited and emits in the "biological window"in vitro, making it a potential potent new generation photodynamic therapeutic agent capable of singlet oxygen generation and in vitro near-infrared emission.     

One color resonant two photon ionization spectroscopy of p-methylstyrene and theoretical calculation

The band origin of the S1<--S0 transition of p-methylstyrene is determined to be 34,276 cm-1 by one color resonant two photon ionization (1C-R2PI) method, which is red shifted by 3811 cm-1 with respect to that of benzene. This indicates that the interaction of the methyl and vinyl groups with the ring in the S1 state is greater than that in the S0 state. The active vibrations assigned from the R2PI spectrum are found to be the in-plane ring modes. The bands at 399, 613, 724, and 786 cm-1 are assigned to the vibrations 9b, 6b, 12, and 1, respectively, and discussed in detail. The experimental results are well supported by ab initio and density functional theory (DFT) calculations.     

Theoretical investigation of the molecular, electronic structures and vibrational spectra of a series of first transition metal phthalocyanines

A theoretical investigation of the fully optimized geometries and electronic structures of metallophthalocyanines FePc, CoPc, NiPc, CuPc and ZnPc has been conducted with the density functional theory (DFT) method. A comparison between the different molecules for the geometry, molecular orbital, and atomic charge is made. The simulated order of the sizes of the central hole is FePc>CoPc>NiPcNiPc>CuPc>ZnPc, and the atomic charges of the central metal (M=Fe, Co, Ni, Cu, Zn) ions vary in the same order, FePc>CoPc>NiPcCoPc>FePc>CuPc>ZnPc, and the corresponding peaks predicted at 894, 896, 898, 882 and 871 cm(-1), respectively, also exhibit the same order as above-mentioned. Moreover, the lines of fit through plots of the experimental IR and Ra frequencies versus the calculated ones show very good correlations.