Ambipolar hexa-peri-hexabenzocoronene-fullerene hybrid materials

A new class of self-assembling hexa-peri-hexbenzocoronene (HBC)-fullerene hybrid materials has been synthesized and characterized. Photoluminescence experiments indicate that energy transfer processes can be tuned in these donor-acceptor systems by varying the length and nature of the linker group. In preliminary device testing, ambipolar charge transport behavior is observed in organic field effect transistors, while single active component organic photovoltaic devices consisting of these materials achieved a maximum external quantum efficiency of 30%.     

Polarizable molecular dynamics simulation of Zn(II) in water using the AMOEBA force field

The hydration free energy, structure, and dynamics of the zinc divalent cation are studied using a polarizable force field in molecular dynamics simulations. Parameters for the Zn(2+) are derived from gas-phase ab initio calculation of Zn(2+)-water dimer. The Thole-based dipole polarization is adjusted based on the Constrained Space Orbital Variations (CSOV) calculation while the Symmetry Adapted Perturbation Theory (SAPT) approach is also discussed. The vdW parameters of Zn(2+) have been obtained by comparing the AMOEBA Zn(2+)-water dimerization energy with results from several theory levels and basis sets over a range of distances. Molecular dynamics simulations of Zn(2+) solvation in bulk water are subsequently performed with the polarizable force field. The calculated first-shell water coordination number, water residence time and free energy of hydration are consistent with experimental and previous theoretical values. The study is supplemented with extensive Reduced Variational Space (RVS) and Electron Localization Function (ELF) computations in order to unravel the nature of the bonding in Zn(2+)(H(2)O)(n) (n=1,6) complexes and to analyze the charge transfer contribution to the complexes. Results show that the importance of charge transfer decreases as the size of Zn-water cluster grows due to anticooperativity and to changes in the nature of the metal-ligand bonds. Induction could be dominated by polarization when the system approaches condensed-phase and the covelant effects are eliminated from the Zn(II)-water interaction. To construct an "effective" classical polarizable potential for Zn(2+) in bulk water, one should therefore avoid over-fitting to the ab initio charge transfer energy of Zn(2+)-water dimer. Indeed, in order to avoid overestimation of condensed-phase many-body effects, which is crucial to the transferability of polarizable molecular dynamics, charge transfer should not be included within the classical polarization contribution and should preferably be either incorporated in to the pairwise van der Waals contribution or treated explicitly.     

Separation and quantitative determination of sesquiterpene lactones in Lindera aggregata (Wu‐yao) by ultra‐performance LC‐MS/MS

An ultra‐performance LC in combination with MS/MS method was established to evaluate the quality of Wu‐yao (the dried root of Lindera aggregata (Sims) Kosterm. (Lauraceae)) through simultaneous quantitation of five sesquiterpene lactones, linderagalactone D ( 1 ), linderagalactone C ( 2 ), hydroylindestenolide ( 3 ), neolinderalactone ( 4 ) and linderane ( 5 ). All compounds were separated on a Waters Acquity ultra‐performance LC HSS T3 column (2.1 mm×100 mm, 1.8 μm particle size) with linear gradient elution of acetonitrile and 0.1% formic acid. An ESI interface in the positive mode was employed prior to MS detection. All the compounds showed good linearity (R²≥0.9992). The recoveries, measured at three concentration levels, varied from 97.3 to 103.4% with RSDs <4.8%. The simple, rapid and reliable method was successfully applied to quantify the five components in 13 samples of Wu‐yao from different areas.     

A rapid method with ultra‐high‐performance liquid chromatography–tandem mass spectrometry for simultaneous determination of five type B trichothecenes in traditional Chinese medicines

A speedy and selective ultra‐HPLC‐MS/MS method for simultaneous determination of deoxynivalenol (DON), 3‐acetyldeoxynivalenol (3‐ADON), 15‐ADON, nivalenol and fusarenon X in traditional Chinese medicines (TCMs) was developed. The method was based on one‐step sample cleanup using reliable homemade cleanup cartridges. A linear gradient mobile‐phase system, consisting of water containing 0.2% aqueous ammonia and acetonitrile/methanol (90:10, v/v) at a flow rate of 0.4 mL/min, and an Acquity UPLC HSS T3 column (100 mm×2.1 mm, 1.8 μm) were employed to obtain the best resolution of the target analytes. [¹³C₁₅]–DON was used as the internal standard to accomplish as accurate as possible quantitation. The established method was further validated by determining the linearity (R²≥0.9990), sensitivity (LOQ, 0.29–0.99 μg/kg), recovery (88.5–119.5%) and precision (RSD≤15.8%). It was shown to be a suitable method for simultaneous determination of DON, 3‐ADON, 15‐ADON, nivalenol and fusarenon X in various TCM matrices. The utility and practical impact of the method was demonstrated using different TCM samples.     

Improving Gene Delivery Efficiency of Bioreducible Poly(amidoamine)s via Grafting with Dendritic Poly(amidoamine)s

Dendritic poly(amidoamine)s (PAMAM)s were introduced into the side chains of disulfide‐containing poly(amidoamine)s via repetitive Michael addition and amidation. The bioreducible poly(amidoamine)s grafted with dendritic polyamidoamines showed high buffer capacity, low cytotoxicity and strong DNA binding ability at low N/P ratio. They were able to condense DNA into small sized polycation/DNA complexes, which degraded and released the incorporated DNA under reductive conditions. In comparison to the original disulfide‐containing poly(amidoamine) with aminoethyl side chain, the grafting of the bioreducible poly(amidoamine) with dendrimer greatly improved the transfection efficiencies of 293T and HeLa cells with foreign DNA at various N/P ratios. The structure–gene delivery property relations of dendrimer‐grafted polycations will provide valuable insight into the design of highly efficient and less toxic polycationic gene carriers.

     

Synthesis,characterization, and drug release behaviors of a novel thermo‐sensitive poly(N‐acryloylglycinates)

In this study, a novel thermo‐sensitive poly(N‐acryloylglycinates) was prepared in order to get a potential drug release carrier. The corresponding monomers and the polymers were characterized with Fourier‐transform infrared (FTIR) and ¹H NMR. The thermo‐sensitivity of the poly(N‐acryloylglycinates) was evaluated by measuring their lower critical solution temperatures (LCST) in water, inorganic salt solution, and different pH solutions. The results indicated that poly(N‐acryloylglycine methyl ester) (NAGME) and poly(N‐acryloylglycine ethyl ester) (NAGEE) exhibit a reversible thermo‐sensibility in their aqueous solutions at 61.5 and 12.5°C, respectively. However, no thermo‐sensitive behavior of poly(N‐acryloylglycine propyl ester) (NAGPE) was found due to its over hydrophobicity. The swelling studies on hydrogels were carried out at different temperatures, in different pH, and inorganic salt solutions. The hydrogels showed a remarkable phase transition at about 35°C with changing temperature. The release rate of caffeine from the thermo‐sensitive hydrogel was apparently decreased as the crosslinker content increased and temperature decreased. Seventy five percent caffeine from the polymeric hydrogel with 5% NMBA (N, N‐methylenebis(acrylamide)) was released at room temperature within 240 min, whereas 95.4% caffeine diffused into the medium at 37°C. Copyright © 2009 John Wiley & Sons, Ltd.     

Gas-phase acidities of cysteine-polyglycine peptides: The effect of the cysteine position

The sequence and conformational effects on the gas-phase acidities of peptides have been studied by using two pairs of isomeric cysteine-polyglycine peptides, CysGly_3,4NH₂ and Gly_3,4CysNH₂. The extended Cooks kinetic method was employed to determine the gas-phase acidities using a triple quadrupole mass spectrometer with an electrospray ionization source. The ion activation was achieved via collision-induced dissociation experiments. The deprotonation enthalpies (Δ_acid H) were determined to be 323.9 ± 2.5 kcal/mol (CysGly₃NH₂), 319.2 ± 2.3 kcal/mol (CysGly₄NH₂), 333.8 ± 2.1 kcal/mol (Gly₃CysNH₂), and 321.9 ± 2.8 kcal/mol (Gly₄CysNH₂), respectively. The corresponding deprotonation entropies (Δ_acid S) of the peptides were estimated. The gas-phase acidities (Δ_acid G) were derived to be 318.4 ± 2.5 kcal/mol (CysGly₃NH₂), 314.9 ± 2.3 kcal/mol (CysGly₄NH₂), 327.5 ± 2.1 kcal/mol (Gly₃CysNH₂), and 317.4 ± 2.8 kcal/mol (Gly₄CysNH₂), respectively. Conformations and energetic information of the neutral and anionic peptides were calculated through simulated annealing (Tripos), geometry optimization (AM1), and single point energy calculations (B3LYP/6-31+G(d)), respectively. Both neutral and deprotonated peptides adopt many possible conformations of similar energies. All neutral peptides are mainly random coils. The two C-cysteine anionic peptides, Gly_3,4(Cys-H)⁻NH₂, are also random coils. The two N-cysteine anionic peptides, (Cys-H)⁻Gly_3,4NH₂, may exist in both random coils and stretched helices. The two N-cysteine peptides, CysGly₃NH₂ and CysGly₄NH₂, are significantly more acidic than the corresponding C-terminal cysteine ones, Gly₃CysNH₂ and Gly₄CysNH₂. The stronger acidities of the former may come from the greater stability of the thiolate anion resulting from the interaction with the helix-macrodipole, in addition to the hydrogen bonding interactions.     

Two minor phytoecdysteroids of the plant Silene viridiflora

Chemical investigations of Silene viridiflora (L.) yielded a new ecdysteroid, 20-hydroxyecdysone 20,22-monoacetonide-25-acetate (1), and a known ecdysteroid, 2-deoxypolypodine B-3-beta-D-glucoside (2). The elucidation of the chemical structures was established by 1D and 2D NMR experiments.     

血糖近红外光谱分析的Savitzky-Golay平滑模式与偏最小二乘法因子数的联合优选

利用偏最小二乘法(PLS)和光谱Savitzky-Golay(SG)平滑方法,建立血清葡萄糖近红外光谱分析的优化模型。基于最优单波数模型的预测效果,提出划分校正集和验证集的一种新方法。采用10000～5300cm-1和4920～4160cm-1的组合波段,光谱经过SG平滑处理,利用PLS方法建立定标预测模型。将平滑点数扩充为5,7,…,87(奇数),多项式次数扩充为n=2,3,4,5,6,得到包含582个平滑模式的14个平滑系数表。对所有平滑模式和PLS因子数(1～40)分别建立PLS模型。按照预测效果进行优选,得到最优SG平滑模式为1阶导数平滑,3、4次多项式类型,SG平滑点数为53,最优PLS因子数为7,最优RMSEP达到0.376mmol/L。所采用的划分校正集和验证集的方法、SG平滑模式的扩充、SG平滑模式和PLS因子数的联合大范围筛选能够有效地应用于近红外光谱分析的模型优化。     

Analysis of anthocyanin pigments in Lonicera (Caerulea) extracts using chromatographic fractionation followed by microcolumn liquid chromatography-mass spectrometry

Anthocyanins from the fruit Lonicera caerulea L. var. kamtschatica (blueberry honeysuckle, Caprifoliaceae) were studied via (semi)preparative chromatographic fractionation followed by MS and μLC/MS analysis. The extraction procedure was optimized with respect to analytical purposes as well as its potential use for the preparation of nutraceuticals. The highest yield of anthocyanins was obtained using acidified methanol as the extraction medium. A comparable total anthocyanin content was obtained using a mixture of methanol and acetone. However, when Lonicera anthocyanins were in contact with acetone, a condensation reaction occurred to a large extent and related 5-methylpyranoanthocyanins were found. The effect of other extraction media, including ethanol as a "green" solvent, is also discussed. The potential of two fractionation procedures for extract purification differing in their chromatographic selectivity and scale was studied (i.e. using a Sephadex LH-20 gel column and a reversed phase). Fractions obtained by both procedures were used for a detailed analysis. MS and μLC/MS(2) methods were used for monitoring anthocyanin and 5-methylpyranoderivatives content as well as identifying less common and more complex dyes (dimer of cyanidin-3-hexoside, cyanidin-ethyl-catechin-hexosides, etc.). These more complex dyes are most likely formed during fruit treatment.