H-shaped oligothiophenes with low band gaps and amphoteric redox properties

H-shaped bridged oligothiophenes HT-1 and HT-2 were synthesized by two different approaches. Different from normal oligothiophenes, HT-1 and HT-2 showed low band gaps and amphoteric redox behaviors due to intramolecular charge transfer, which is further supported by time-dependent DFT calculations.     

Preparative isolation and purification of anti‐tumor agent ansamitocin P‐3 from fermentation broth of Actinosynnema pretiosum using high‐performance counter‐current chromatography

Ansamitocin P‐3 is a potent anti‐tumor maytansinoid found in Actinosynnema pretiosum. However, due to the complexity of the fermentation broth of Actinomycete, how to effectively separate ansamitocin P‐3 is still a challenge. In this study, both analytical and preparative high‐performance counter‐current chromatography were successfully used to separate and purify ansamitocin P‐3 from fermentation broth. A total of 28.8 mg ansamitocin P‐3 with purity of 98.4% was separated from 160 mg crude sample of fermentation broth in less than 80 min with the two‐phase solvent system of hexane–ethyl acetate–methanol–water (0.6:1:0.6:1, v/v/v/v). The purity and structural identification were determined by HPLC, ¹H NMR, ¹³C NMR and mass spectroscopy.     

Phenylcarbamoylated β‐CD: π‐Acidic and π‐basic chiral selectors for HPLC

Two types of chiral stationary phases for HPLC based on π‐acidic or π‐basic perphenylcarbamoylated β‐CDs were synthesized. The relative structural features of the two effective chiral selectors are discussed and compared in both normal‐phase and RP modes. In addition, the nature and concentration of alcoholic modifiers were varied for optimal separation in normal phase and the structural variation of the analytes was also examined. The results showed that hydrogen bonding, steric effect and π‐acidic–π‐basic interaction contributed greatly to enantioseparation. Upon comparison, some of the differences in the separation behavior of the two types of chiral stationary phases might be due to the π‐acidic or π‐basic phenylcarbamate groups.     

Synthesis and Characterizations of Ferrocenyl Carbonyl Chromium and Cobalt Clusters

Two novel bimetallic complexes, [Cr(CO)₃(η ⁶-C₆H₅)–C≡C–C₆H₄–Fc] (Fc = C₅H₅FeC₅H₄] (1) and [Cr(CO)₃(η ⁶-C₆H₅)–C ≡ C–Fc–C(CH₃)₂–Fc] (3), were synthesized by the Sonogashira coupling reaction. By using of (1) and (3) as ligands to react with Co₂(CO)₈, two others novel polymetallic complexes, [Cr(CO)₃(η ⁶-C₆H₅){Co₂(CO)₆-η ²-μ ²-C≡C–}–C₆H₄–Fc] (2) and [Cr(CO)₃(η ⁶-C₆H₅){Co₂(CO)₆-η ²-μ ²-C≡C–}Fc–C(CH₃)₂–Fc] (4) were obtained. Four carbonyl complexes were characterized by elemental analysis, FT-IR, NMR and MS. The molecular structures of complexes (1), (2) and (4) were determined by single crystal X-ray diffraction. The interactions among the ferrocenyl, Cr(CO)₃ and Co₂(CO)₆-η ²-μ ²-C≡C– units were investigated by cyclic voltammetry.     

Resolving the composition of protein complexes using a MALDI LTQ orbitrap

Current biological studies have been advanced by the continuous development of robust, accurate, and sensitive mass spectrometric technologies. The MALDI LTQ Orbitrap is a new addition to the Orbitrap configurations, known for their high resolving power and accuracy. This configuration provides features inherent to the MALDI source, such as reduced spectra complexity, forgiveness to contaminants, and sample retention for follow-up analyses with targeted or hypothesis-driven questions. Here we investigate its performance for characterizing the composition of isolated protein complexes. To facilitate the assessment, we selected two well characterized complexes from Saccharomyces cerevisiae, Apl1 and Nup84. Manual and automatic MS and MS/MS analyses readily resolved their compositions, with increased confidence of protein identification compared with our previous reports using MALDI QqTOF and MALDI IT. CID fragmentation of singly-charged peptides provided sufficient information for conclusive identification of the isolated proteins. We then assessed the resolution, accuracy, and sensitivity provided by this instrument in the context of analyzing the isolated protein assemblies. Our analysis of complex mixtures of singly-charged ions up to m/z 4000 showed that (1) the resolving power, inversely proportional to the square root of m/z, had over four orders of magnitude dynamic range; (2) internal calibration led to improved accuracy, with an average absolute mass error of 0. 5 ppm and a distribution centered at 0 ppm; and (3) subfemtomole sensitivity was achieved using both CHCA and DHB matrices. Additionally, our analyses of a synthetic phosphorylated peptide in mixtures showed subfemtomole level of detection using neutral loss scanning.     

Luminescence of Eu(DBM)3Phen-doped in azobenzene-containing copolymers—Effects of absorption overlapping of two components

Poly(N-isopropylacrylamide)-b-poly{6-[4-(4-methylphenyl-azo)phenoxy]hexylmethacrylate} (PNIPAM₃₂-b-PAzoMM₈) and poly(N-isopropylacrylamide)-b-poly{6-[methyl(4-nitrophenyldiazenyl)phenyl]aminohexylmethacrylate} (PNIPAM₃₂-b-PAzoNO₁₀) were prepared by reversible addition–fragmentation chain transfer (RAFT) radical polymerization. The optical properties of Eu(DBM)₃Phen (Eu, Europium; DBM, dibenzoylmethide; Phen, 1,10-phenanthroline)-doped azobenzene-containing copolymer vesicle solutions were studied by UV–vis and fluorescence spectroscopy. When the electronic transition bands of azobenzene and Eu(DBM)₃Phen overlapped at about 350 nm in PNIPAM₃₂-b-PAzoMM₈, the fluorescent emission intensity at 612 nm of Eu(DBM)₃Phen could be modulated by irradiation with UV and visible light. However, when the absorption of the azobenzene-moiety red-shifted to 477 nm in PNIPAM₃₂-b-PAzoNO₁₀, the luminescence intensity of Eu(DBM)₃Phen was not affected any longer. The difference between these two systems was possibly caused by the energy allocation in the luminescence process, which was discussed in detail.     

Toxicokinetics and the related metabolites in rainbow trout (Oncorhynchus mykiss) after exposure to decabromodiphenyl ether

Decabromodiphenyl ether (BDE209) is poorly absorbed by mammals, and little information is available on the toxicokinetics of BDE209 and its metabolites in fish. In the present study, rainbow trout (Oncorhynchus mykiss) were administered to 100 ng/g and 500 ng/g body wet weight of BDE209 via a single intraperitoneal injection and parent BDE209 and its metabolites were sequentially monitored for 28 days. The results showed that toxicokinetic profiles of BDE209 could be described by the one-compartment model. In the higher dose group (500 ng/g wet weight), the calculated half-life (t _1/2) and elimination rate (k _e) were 17.7 d and 0.039/d in the liver, and 100.3 d and 0.007/d in the muscle, respectively. Three major methoxylated brominated diphenyl ethers (MeO-BDEs) were detected with 2,2′,4,4′-tetrabromo-5-methoxydiphenyl ether (5-MeO-BDE47) being detected in all tissue samples. There was no significant temporal change of 5-MeO-BDE47 concentration in the muscle, whereas an exponential increase was observed in the liver. Therefore, the metabolism rate of BDE209 depended on the administered dose. BDE209 was hardly accumulated in the muscle of rainbow trout, while the liver was a primary metabolic organ. MeO-BDEs were formed via metabolism of BDE209, which probably played a significant role in fish toxicology as a potential indicator.     

Chemical composition and antifungal activity of essential oils of Thuja sutchuenensis, a critically endangered species endemic to China

The essential oils from leaves, twigs and stems of large trees and shrub-like trees of Thuja sutchuenensis were extracted by hydrodistillation and supercritical fluid extraction, and analyzed by GC and GC-MS. The essential oil composition differed significantly among the three organs, as well as between large trees and shrub-like trees. Furthermore, consistent with the eastern Asia-North American disjunct distribution of the genus, many differences in the essential oil composition between T. sutchuenensis and other Thuja species were apparent. The essential oils exhibited a certain degree of antifungal activity against six strains of human pathogenic fungi.     

New observation on a class of old reactions: Chemoselectivity for the solvent-free reaction of aromatic aldehydes with alkylketones catalyzed by a double-component inorganic base system

Solvent-free reactions of aromatic aldehydes with three representative ketones, including acetophenone, acetone and cyclohexanone, have been examined under the catalysis of a low-cost inorganic base system consisting of NaOH and K₂CO₃. It was found that the chemoselectivity of the reactions is in close relationship with the composition of the reactants and the doublecomponent catalyst. Under the optimized experimental conditions, 1,2,3,4,5-pentasubstituted cyclohexanols, α,β-unsaturated ketones and Claisen-Schmidt bicondensation products were obtained in high yields. Two Kostanecki’s triketones were separated, The composition and structure were affirmed by X-ray crystallographic analysis.     

Assessment of linear finite‐difference Poisson–Boltzmann solvers

CPU time and memory usage are two vital issues that any numerical solvers for the Poisson–Boltzmann equation have to face in biomolecular applications. In this study, we systematically analyzed the CPU time and memory usage of five commonly used finite‐difference solvers with a large and diversified set of biomolecular structures. Our comparative analysis shows that modified incomplete Cholesky conjugate gradient and geometric multigrid are the most efficient in the diversified test set. For the two efficient solvers, our test shows that their CPU times increase approximately linearly with the numbers of grids. Their CPU times also increase almost linearly with the negative logarithm of the convergence criterion at very similar rate. Our comparison further shows that geometric multigrid performs better in the large set of tested biomolecules. However, modified incomplete Cholesky conjugate gradient is superior to geometric multigrid in molecular dynamics simulations of tested molecules. We also investigated other significant components in numerical solutions of the Poisson–Boltzmann equation. It turns out that the time‐limiting step is the free boundary condition setup for the linear systems for the selected proteins if the electrostatic focusing is not used. Thus, development of future numerical solvers for the Poisson–Boltzmann equation should balance all aspects of the numerical procedures in realistic biomolecular applications. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010