固相微萃取-气相色谱-质谱分析牡丹花的挥发性成分

用固相微萃取装置（SPME）顶空提取牡丹花的挥发性成分,采用气相色谱-质谱（GC-MS）联用技术定性分析不同品种牡丹花的挥发性成分,归一法计算其相对百分含量,同时对SPME与水气蒸馏提取效果进行了比较。10个品种牡丹花共检出34种成分,其中多数是烷烃。不同品种牡丹花的成分与相对百分含量不同,少量的醇、酯、烯等成为其特有成分。     

Synthesis and photopolymerization kinetics of benzophenone piperazine one‐component initiator

A one‐component type II photoinitiator (PDBP), based on 4‐hydroxybenzophenone (HBP), acryloyl chloride, and piperazine, was synthesized and its structure was confirmed by ¹H‐NMR. The photopolymerization kinetics of the photoinitiator was studied by real‐time Infrared spectroscopy (FT‐IR). It indicated that PDBP was a more effective photoinitiator than that of BP/triethylamine (TEA). The rate of polymerization, final conversion increased and the induction period shortened with increase in PDBP concentration, light intensity, and amine concentration. The kinetics of photopolymerization for TPGDA incorporating PDBP in the presence of different tertiary amines as the initiating system indicated that the PDBP/TEA combination exhibited the highest polymerization rates among the PDBP/amine combinations. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis and characterization of copolymerizable one‐component type II photoinitiator

A copolymerizable one‐component Type II photoinitiator (CMEBP), based on 4‐hydroxybenzophenone (HBP), epichlorohydrin, morpholine, and acryloyl chloride, was synthesized and its structure was confirmed by ¹H‐NMR. The properties of CMEBP were investigated with UV spectroscopy and photo‐differential scanning calorimetry (photo‐DSC). The maximum of UV absorption red‐shifted significantly compared to benzophenone (BP). Photopolymerization results of tripropylene glycol diacrylate (TPGDA) indicated that CMEBP had larger maximum rate of polymerization than that of BP/triethanolamine (TEOHA) and HBP/triethylamine (TEA), larger final double bond conversion than that of HBP/TEA, but lower than that of BP/TEOHA. The rate of polymerization, final conversion increased and the induction period shortened with increase in CMEBP concentration. Copyright © 2008 John Wiley & Sons, Ltd.     

DFT Study on Methanofullerene Derivative [6,6]-Phenyl-C61 Butyric Acid Methyl Ester

Density functional theory (DFT) and time-dependent density functional theory (TDDFT) with hybrid functional B3LYP were used to investigate several physical and chemical properties of [6,6]-phenyl-C₆₁ butyric acid methyl ester (PCBM), including the geometry, electron structure, charge population, bond properties, as well as IR, Raman and electronic absorption spectra. The analysis of the natural bond orbital (NBO) suggested that there were about 0.11 electrons transferred from moiety phenyl and butyric acid methyl ester group of PCBM to fullerene cage. The strongest IR and Raman peaks came from different modes with the frequencies of 1773 and 1492 cm⁻¹, respectively. The calculated isotropic polarizability, polarizability anisotropy invariant, and hyperpolarizability were 577.7, 96.9, and −22.8 a.u., respectively. Based on TDDFT, the electronic absorption spectra of PCBM were calculated and analyzed. The calculated absorption band near 349 nm agreed well with the experimental measurement.     

Weighted estimates for multilinear commutators of Marcinkiewicz integral

Let μ be the n-dimensional Marcinkiewicz integral and μb the multilinear commutator of μ. In this paper, the following weighted inequalities are proved for ω ∈ A∞ and 0 〈 p 〈 ∞,
｜｜μ（f）｜｜LP（ω）≤C｜Mf｜LP（ω） and ｜｜μb（f）｜｜LP（ω）≤C｜｜ML（log L）^1/r f｜｜LP（ω）.
The weighted weak L（log L）^1/r -type estimate is also established when p=1 and ω∈A1.     

Photoinduced Electron and Energy Transfer in Dyads of Porphyrin Dimer and Perylene Tetracarboxylic Diimide

Two compounds containing a porphyrin dimer and a perylene tetracarboxylic diimide (PDI) linked by phenyl ( 1 ) or ethylene groups ( 2 ) are prepared. The photophysical properties of these two compounds are investigated by steady state electronic absorption and fluorescence spectra and lifetime measurements. The ground state absorption spectra reveal intense interactions between the porphyrin units within the porphyrin dimer, but no interactions between the porphyirn dimer and PDI. The fluorescence spectra suggest efficient energy transfer from PDI to porphyrin accompanied by less efficient electron transfer from porphyrin to PDI. The energy transfer is not affected by the dimeric structure of porphyrin or the linkage between the porphyrin dimer and PDI. However, the electron transfer from porphyrin to PDI is significantly affected by either the linkage between the donor and the acceptor or the polarity of the solvents. The dimeric structure of the porphyrin units in these compounds significantly promotes electron transfer in nonpolar, but not in polar solvents.     

Mutability-Landscape-Guided Engineering of l-Threonine Aldolase Revealing the Prelog Rule in Mediating Diastereoselectivity of C−C Bond Formation

l -threonine aldolase (LTA) catalyzes C−C bond synthesis with moderate diastereoselectivity. In this study, with LTA from Cellulosilyticum sp (CpLTA) as an object, a mutability landscape was first constructed by performing saturation mutagenesis at substrate access tunnel amino acids. The combinatorial active-site saturation test/iterative saturation mutation (CAST/ISM) strategy was then used to tune diastereoselectivity. As a result, the diastereoselectivity of mutant H305L/Y8H/V143R was improved from 37.2 %_syn to 99.4 %_syn. Furthermore, the diastereoselectivity of mutant H305Y/Y8I/W307E was inverted to 97.2 %_anti. Based on insight provided by molecular dynamics simulations and coevolution analysis, the Prelog rule was employed to illustrate the diastereoselectivity regulation mechanism of LTA, holding that the asymmetric formation of the C−C bond was caused by electrons attacking the carbonyl carbon atom of the substrate aldehyde from the re or si face. The study would be useful to expand LTA applications and guide engineering of other C−C bond-forming enzymes.     

Ultra-Small Air-Stable Triplet-Triplet Annihilation Upconversion Nanoparticles for Anti-Stokes Time-Resolved Imaging

Image contrast is often limited by background autofluorescence in steady-state bioimaging microscopy. Upconversion bioimaging can overcome this by shifting the emission lifetime and wavelength beyond the autofluorescence window. Here we demonstrate the first example of triplet-triplet annihilation upconversion (TTA-UC) based lifetime imaging microscopy. A new class of ultra-small nanoparticle (NP) probes based on TTA-UC chromophores encapsulated in an organic–inorganic host has been synthesised. The NPs exhibit bright UC emission (400–500 nm) in aerated aqueous media with a UC lifetime of ≈1 μs, excellent colloidal stability and little cytotoxicity. Proof-of-concept demonstration of TTA-UC lifetime imaging using these NPs shows that the long-lived anti-Stokes emission is easily discriminable from typical autofluorescence. Moreover, fluctuations in the UC lifetime can be used to map local oxygen diffusion across the subcellular structure. Our TTA-UC NPs are highly promising stains for lifetime imaging microscopy, affording excellent image contrast and potential for oxygen mapping that is ripe for further exploitation.     

Phosphorescent and Test Strips Detection Properties of ClO− Probes Based on Iridium(III) Complexes with Pivaloyl Unit as Recognition Site

Three green phosphorescent Iridium(III) complex-based probes with different ligands (Cl⁻ ( Ir-1 ), NCS⁻ ( Ir-2 ) and NCO⁻ ( Ir-3 )) had been developed to detect hypochlorite (ClO⁻) using pivaloyl group as recognition site. The introduction of strong field ligand NCS and NCO caused an increase of quantum yields and phosphorescent lifetime both in solid and solution states. All the three probes could selectively and rapidly detect ClO⁻ through the changes in UV-visible and phosphorescence spectra. Upon addition of ClO⁻ to the solution of probes, green phosphorescent color of probes displayed obvious quench. Meanwhile, using a portable UV lamp, test strips which were pre-immersed with the above-mentioned probes could achieve easy detection of ClO⁻. The sensing process was confirmed by NMR, IR and ESI-MS.     

Poly-Hydride [AuI7(PPh3)7H5](SbF6)2 cluster complex: Structure,Transformation, and Electrocatalytic CO2 Reduction Properties

Hydride Au^I bonds are labile due to the mismatch in electric potential of an oxidizing metal and reducing ligand, and therefore the structure and structure–activity relationships of nanoclusters that contain them are seldom studied. Herein, we report the synthesis and characterization of [Au₇(PPh₃)₇H₅](SbF₆)₂ (abbrev. Au₇H₅ ²⁺ ), an Au cluster complex containing five hydride ligands, which decomposed to give [Au₈(PPh₃)₇]²⁺ (abbrev. Au₈ ²⁺ ) upon exposure to light (300 to 450 nm). The valence state of Au^I and H⁻ was verified by density functional theory (DFT) calculations, NMR, UV/Vis and XPS. The two nanoclusters behaved differently in the electrocatalytic CO₂ reduction reaction (CO₂RR): Au₇H₅ ²⁺ exhibited 98.2 % selectivity for H₂, whereas Au₈ ²⁺ was selective for CO (73.5 %). Further DFT calculations showed that the H⁻ ligand inhibited the CO₂RR process compared with the electron-donor H.