Production,Purification and Characterization of the Hen Egg-White Lysozyme Inhibitor from Enterobacter cloacae M-1002

Three hen egg-white lysozyme inhibitor producing strains, Enterobacter cloacae M-1002, E. sakazakii M-1204, and Erwinia rhapontici H-55, were isolated from the soils of Taiwan. E. cloacae M-1002 appeared to be a promising inhibitor producing strain. One inhibitor was isolated from the culture broth of this strain. Maximum lysozyme inhibitory activity was obtained when the bacterium was grown aerobically in a medium consisting of 0.75% glucose, 0.25% beef extract, 1.0% polypeptone, and 0.25% sodium L-glutamate (pH 70) at 37 °C after 36–48 hrs. A hen egg-white lysozyme inhibitor was isolated from the culture broth of this strain. The inhibitor was purified from the culture supernatant of E. cloacae M-1002 by ammonium sulfate fractionation, DEAE-Sepharose CL-6B column chromatography and Fractogel TSK HW-55 (S) gel chromatography. Molecular weight of the purified lysozyme inhibitor was estimated to be 18, 000–20, 000 by SDS-PAGE and HPLC, and was composed of 71% amino acid and 23% total sugar. Serine, glycine, and alanine in a 3:2:1 molar ratio were the major amino acids, calculated to be 32.8, 20.3, and 11.4% (mol%), respectively. Glucose and mannose were the major sugar components of the inhibitor. The inhibitor was stable at pH 5 to 8 and was stable under 50 °C. Only hen egg-white lysozyme was inhibited by the purified inhibitor but not the other tested enzymes such as lysozyme of celery, turnip; lytic enzyme of Pseudomonas aeruginosa M-1001; chitinase/lysozyme of P. aeruginosa K-187; or cellulase and xylanase of Streptomyces actuosus A-151 and Aspergillus sp. G-393. The inhibition of lysozyme to the bacterial cell lytic activity by the purified inhibitor was 100%.     

The electronic structure of two novel carbides,Ca3Cl2C3 and Sc3C4, containing C3 units

The triatomic C₃ unit that is known to exist in Mg₂C₃ has recently been found in the new compounds Ca₃Cl₂C₃ and Sc₃C₄. The electronic structure of these compounds is analyzed with the aid of extended Hückel Calculation. A fragment molecular Orbital analysis (FMO) is used to study the bonding characteristic of the C₃ unit in the ionic Ca₃Cl₂C₃, and in Sc₃C₄, the latter Containing C₂ unit and single C atoms as well. Sc₃C₄ Contain partially filled Sc (d) and C₂ bands leading to Metallic conductivity and Pauli Paramagnetism. The C? C bond distance in the diatomic C₂ units is significantly increased (d_{c? c}= 125 pm) relative to C^2?₂ or acetylene, because antibonding π*_g orbitals are partially filled. The unusual bending of the C₃ unit (d_{c? c}= 134 pm) in Sc₃C₄ (175,8°) and in Ca₃Cl₂C₃ (169,0°) is likely to be a result of the packing arrangement in these structures.     

LC/ESI‐MS/MS characterisation of lipopeptide biosurfactants produced by the Bacillus licheniformis V9T14 strain

Lipopeptide biosurfactants produced by the Bacillus licheniformis V9T14 strain showed an interesting anti‐adhesion activity against biofilm formation of human pathogenic bacterial strains. The chemical characterisation of the crude extract of V9T14 strain was first developed through electrospray ionisation mass spectrometry (ESI‐MS) and ESI‐MS/MS direct infusions: two sets of molecular ion species belonging to the fengycin and surfactin families were revealed and their structures defined, interpreting their product ion spectra. The LC/ESI‐MS analysis of the crude extract allowed to separate in different chromatogram ranges the homologues and the isoforms of the two lipopeptide families. The extract was then fractionated by silica gel chromatography in two main fractions, I and II. The purified biosurfactants were analysed through a new, rapid and suitable LC/ESI‐MS/MS method, which allowed characterising the composition and the structures of the produced lipopeptides. LC/ESI‐MS/MS analysis of fraction I showed the presence of C₁₃, C₁₄ and C₁₅ surfactin homologues, whose structures were confirmed by the product ion spectra of the sodiated molecules [M + Na]⁺ at m/z 1030, 1044 and 1058. LC/ESI‐MS/MS analysis of fraction II confirmed the presence of two main fengycin isoforms, with the protonated molecules [M + H]⁺ at m/z 1478 and 1506 corresponding to C₁₇ fengycin A and C₁₇ fengycin B, respectively. Other homologues (C₁₄ to C₁₆) were revealed and confirmed as belonging to fengycin A or B according to the retention times and the product ions generated, although with the same nominal mass. Finally, a relative percentage content of each homologue for both lipopeptides families in the whole extract was proposed. Copyright © 2010 John Wiley & Sons, Ltd.     

3‐Methylflavones characterization revisited: complete assignment of 1H and 13C NMR data

Ten 3‐methylflavone derivatives were studied. Previously reported NMR data of some derivatives were corrected and/or completed, including the complete assignment of the two known natural derivatives. The complete ¹H and ¹³C NMR assignments were achieved by combination of one‐dimensional and two‐dimensional NMR experiments. Copyright © 2013 John Wiley & Sons, Ltd.     

Isolation and partial characterization of an antifungal protein produced by Bacillus licheniformis BS-3

An antifungal protein produced by Bacillus licheniformis strain BS-3 was purified to homogeneity by ammonium sulfate precipitation, DEAE-52 column chromatography and Sephadex G-75 column chromatography. The purified protein was designated as F2 protein, inhibited the growth of Aspergillus niger, Magnaporthe oryzae and Rhizoctonia solani. F2 protein was a monomer with approximately molecular weight of 31 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gave a single peak on High Performance Liquid Chromatography (HPLC). Using Rhizoctonia solani as the indicator strain, the EC50 of F2 protein was 35.82 μg/mL, displaying a higher antifungal activity in a range of pH 6.0 to pH 10.0, and at a temperature below 70 °C for 30 min. F2 protein was moderately resistant to hydrolysis by trypsin, proteinase K, after which its relative activities were 41.7% and 59.5%, respectively. F2 protein was assayed using various substrates to determine the enzymatic activities, the results showed the hydrolyzing activity on casein, however, no enzymatic activities on colloidal chitin, CM-cellulose, xylan, M. lysodeikticus, and p-nitrophenyl-N-acetylglucosaminide.     

Synthesis,characterization, and properties of hydroxyl‐terminated copolysiloxanes containing γ‐cyanopropyl groups

A series of random copolysiloxanes (PCDMS) containing various amount of γ‐cyanopropyl groups are prepared by a new method under mild conditions. Structures of the synthesized polymers are fully characterized by FTIR, ¹H NMR, ²⁹Si NMR, and GPC. Rheological properties of PCDMS are tested by cone and plate rheometer, and thermal properties by differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). Damping properties as well as fuel resistance of the cured PCDMS elastomers are also tested. The correlation between chemical structure, content of cyanopropyl group and properties are discussed. With the increasing amount of polar cyanopropyl group introduced, glass transition temperatures (T_g) of the synthesized PCDMS gradually increases from ?121 to ?65 °C, residual weight increases from 0 to 36% at 800°C, loss factor reaches as high as 1.74, mass increase under fuel immersion for 14 days can be as low as 3.6%. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1408–1421     

Radical cation formation in characterization of novel C3-symmetric disks and their precursors by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Four C3-symmetrical tris(dipeptide) disks and their precursors were characterized using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS). The C3-symmetrical disks were based on a benzene-1,3,5-triscarboxamide core extended by oligopeptides with trialkoxyanilide tails. The results indicate that MALDI TOF MS is a powerful and straightforward analytical technique for characterizing C3-symmetrical disks and their precursors. Clear (pseudo)-molecular ion peaks could readily be identified. It is remarkable that strong radical ion signals were observed for all the compounds, including the anilines that were expected to be protonated prior to laser irradiation using acidic MALDI matrixes. Possible mechanisms for radical ion formation were investigated with the employment of radical scavengers, with various matrixes and with direct laser desorption/ionization (LDI). Most likely the radicals are formed by losing one electron from the aniline nitrogen and stabilized by conjugation through the phenyl ring. It appears that direct photo/thermal ionization of analytes is an important route for the radical ion formation of the compounds with trialkoxy aniline/anilide groups.     

C60O3的结构和电子光谱的理论研究

用INDO系列方法对C₆₀O₃的可能构型进行研究,结果表明:环氧结构邻近的6-6键易发生进一步的加成反应.其中3个氧原子加在同一个六元环的6-6边上,形成环氧结构最稳定的C₃v构型,第3个氧原子加在2个环氧结构相邻的六元环的6-6边上的C₂、C_s构型也相当稳定,C₂、C_s构型的部分¹³C NMR谱与实验吻合.C₆₀O₃可能有较好的反应活性,其电子光谱属于理论预测.     

Structure and Stability of C20H3 Radical

Density functional theory B3LYP with 6-31G* basis set has been used to investigate the geometries, rotational constants, dipole moments, energy gaps and vibrational frequencies of nine series of isomers of C20H3 radical. The result shows that the bowl-like structure with C1 symmetry is the most stable structure, in which the three hydrogen atoms locate on the edge carbon atoms, and the two hydrogen atoms are neighbouring and the other one has a two- carbon atom interval to the neighbouring hydrogen. In addition, the relationship between the energy and the position of one hydrogen atom from end to middle on the linear structures of C20H3 radical with two hydrogens atoms located on two ends was obtained, which shows the energy increase monotonously. Furthermore, hydrogenation can relax the strain and make the isomer of C20 more stable.     

Isolation and characterization of degradation products of citalopram and process-related impurities using RP-HPLC

A reversed-phase high-performance liquid chromatographic method for simultaneous separation and determination of citalopram hydrobromide and its process impurities in bulk drugs and pharmaceutical formulations was developed. The separation was accomplished on an Inertsil ODS 3V (250x4.6 mm; particle size 5 mum) column using 0.3% diethylamine (pH = 4.70) and methanol/acetonitrile (55:45 v/v) as mobile phase in a gradient elution mode. The eluents were monitored by a photodiode array detector set at 225 nm. The chromatographic behavior of all the related substances was examined under variable conditions of different solvents, buffer concentrations, and pH. The method was validated in terms of accuracy, precision, and linearity. The method could be of use not only for rapid and routine evaluation of the quality of citalopram in bulk drug manufacturing units but also for the detection of its impurities in pharmaceutical formulations. Three unknown impurities were consistently observed during the analysis of different batches of citalopram. Forced degradation of citalopram was carried out under thermal, photo, acidic, alkaline, and peroxide conditions. The degradation products and unknown impurities were isolated and characterized by ESI-MS/MS, (1)H NMR, and FT-IR spectroscopy.     

Compositional and structural characterization of alloyed carbide by 3D atom probe and high‐resolution TEM

During tempering of solute supersaturated ferrous martensite, the face‐centered cubic MC‐type carbides (M is alloy elements) such as VC and NbC phases usually co‐precipitate on crystal defects such as dislocation and take on plate‐like morphology. Over‐tempering makes the plate‐like shape change to spherical shape because of Ostwald coarsening. The coarsening process strongly correlates to the diffusion behaviors of the carbon and carbide‐forming elements, and consequently inhomogeneous compositional and structural distribution in the carbides is formed. Three‐dimensional atom probe and high‐resolution transmission electron microscopy have been proved useful methods to characterize the composition, morphology and nanostructure of the carbides that precipitate in a quench‐tempered micro‐alloyed steel. Depending on the actual affinity with C and the diffusion behavior, Si and Al are rejected from the alloy carbide, whereas Mn, V and Nb are inhomogeneously enriched in it. The morphology and structure change with the compositional redistribution. During the coarsening process of the pre‐existing plate‐like carbide, transition carbide that is semi‐coherent with ferritic matrix is formed because of the disparity in diffusion ratio of different solutes. A core–shell complex nanostructure is consequently formed in the coarsening carbide, and the core and shell are identified as V₈C₇ enriched in Mn, Mo and Mo₂C, respectively. Copyright © 2013 John Wiley & Sons, Ltd.     

The effects of strain and charge doping on the electronic properties of graphitic C3N5

Inspired by the successful synthesis of a new graphitic C₃N₅ (termed as g-C₃N₅), we systematically investigate its geometry and electronic properties. The layered g-C₃N₅ has a nanopore diameter of 13.8 Å. It is a direct semiconductor with a band gap of 0.53 eV. The influence of strains on the electronic properties is considered. When applying uniaxial or biaxial compressive strain, the band gap can decrease until zero, resulting in a semiconductor-to-metal transition. The effects of charge doping on the electronic properties are also studied. With the increase of negative charge doping, the band gap becomes narrow until zero, indicating that a semiconductor-to-metal transition occurs as well. In addition, the electronic properties of g-C₃N₅ can be tuned by both strain and charge doping. Thus, we provide a fundamental understanding of g-C₃N₅, and its semiconductor-to-metal transition could be possibly experimentally approached by strain and charge doping, extending the electronic usage of g-C₃N₅.     

Preparation and characterization of copper nanoparticles surface‐capped by alkanethiols

Cu nanoparticles surface‐capped by alkanethiols were synthesized using ligand exchange method in a two‐phase system. The effects of synthetic conditions, including the pH value of CuSO₄ solution, the ratio of cetyltrimethyl ammonium bromide to CuSO₄, and reaction temperature, on the size and shape of as‐synthesized Cu nanoparticles were investigated. As‐synthesized Cu nanoparticles surface‐capped by alkanethiols with different chain lengths (C_xS‐Cu) were characterized by means of X‐ray diffraction, transmission electron microscopy, Fourier transform infrared spectrometry, and ultraviolet–visible light spectrometry. The tribological behavior of C_xS‐Cu as an additive in liquid paraffin was evaluated with a four‐ball machine. Results indicate that cetyltrimethyl ammonium bromide plays an important role in controlling the dispersion of Cu nanoparticles before adding modifier octanethiol into the reaction solution. C_xS‐Cu nanoparticles as additive in liquid paraffin possess excellent antiwear and friction‐reduction performance because of the deposition of nano‐Cu with low melting point on worn steel surface leading to the formation of a self‐repairing protective layer thereon. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis, characterization and solid-phase C NMR of naphtho-9-crown-3

The synthesis and characterization of naptho-9-crown-3, N9C3, as a novel 9-membered ring crown ether with greater lipophilicity than that of benzo-9-crown-3, B9C3, is reported. The solution AA′BB′ pattern of –CH₂O– protons in N9C3 is close to that of B9C3. The solid-phase ¹³C CPMAS NMR, as a tool for conformation prediction, reveals that the solid-phase conformation of the 9-membered ring crown cavity in N9C3 is different from B9C3, the two key C2O2CH₂ and C3O1CH₂ units are predicted to be out of naphthalene plane, and the two C1C2O2CH₂ and C4C3O1CH₂ torsion angles are close to each other.     

Total synthesis of stevastelins B3 and C3: structure confirmation of stevastelin B3 and revision of stevastelin C3

The total synthesis of stevastelin B3, stevastelin C3 and 5-deoxy derivative of stevastelin C3, novel 13-membered cyclic depsipeptides, is described. This study unambiguously confirmed the proposed absolute structure of stevastelin B3, and revealed that the structure of stevastelin C3 is incorrect. The correct structure of stevastelin C3 was established by the total synthesis to be 5-deoxy derivative of the proposed structure.     

Structural determination of 3beta-stearyloxy-urs-12-ene from Maytenus salicifolia by 1D and 2D NMR and quantitative 13C NMR spectroscopy

Six pentacyclic triterpenoids, 3beta-stearyloxy-urs-12-ene (1), friedelin (2), 3beta-friedelinol (3), alpha-amyrin (4), beta-amyrin (5), and lupeol (6), have been isolated from the hexane extract of Maytenus salicifolia Reissek (Celastraceae) leaves. The molecular and structural formula as well as the stereochemistry of a new pentacyclic triterpene (1) were determined using data obtained from 1H and 13C NMR spectra, DEPT135 and by 2D HSQC, HMBC, COSY and NOESY experiments. The molecular formula C48H84O2 was established using quantitative 13C NMR, and the molecular weight (692 Da) was confirmed by elemental analysis and mass spectrometry (GC-MS).     

Some Novel Dinuclear phenylboronates of biologically potent β‐enaminoesters: Synthesis,Spectroscopic characterization,antimicrobial activity and their antiandrogenic effect

Organoboron derivatives of biologically potent β‐enamino esters of the type [Where R = CH₃(1a), C₂H₅ (1b), C₃H₇(1c) and C (CH₃)₃ (1d)] have been prepared by the reactions of β‐enamino esters and Phenyl boronic acid [PhB (OH)₂] in 1:2 molar ratio in refluxing tetrahydrofuran (THF). All these derivatives have been characterized by physico‐chemical properties, elemental analyses and molecular weight measurements. The structures of these compounds have been proposed on the basis of IR, ¹H, ¹³C, ¹¹B NMR spectral data and GC‐mass spectrometry. Phenyl boronic acid, β‐enamino esters and their respective phenylboronates derivatives have been screened for the antibmicrobial activities against pathogenic bacteria (B. subtilis and E. coli) and fungi (A. niger and P. peniculosum) to access their growth inhibiting potential. In addition to this, antiandrogenic effect of Ligand, L^aH₂ and its boron derivative (1a) has also been tested in male albino rats.     

Preparation and characterization of PS/pAPBA core-shell microspheres

Polystyrene microspheres with an average diameter of 55 μm were prepared by suspension polymerization via oxidation of the monomer by ammonium persulfate. Poly-3-aminophenylboronic acid was grafted onto the surfaces of the polystyrene microspheres to form polystyrene/poly-3-aminophenylboronic acid core- shell micospheres. The samples were characterized by scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and nitrogen adsorption/desorption method. The results show that poly-3-aminophenylboronic acid was successfully grafted to the surfaces of the polystyrene microspheres by aromatic ring electronpairing interaction. The surfaces of the core-shell microspheres possessed a porous structure, with the average pore diameter of 30.2 nm and the BET surface area of 193.26 m²/g. __________ Translated from Chinese Journal of Applied Chemistry, 2008, 25(4) (in Chinese)     

Synthesis of Fan‐Shaped C3 Molecule with Three Glycyrrhetinic Acid Units and Self‐Assembly Properties

A novel fan‐shaped C₃ molecule with three glycyrrhetinic acid units was synthesized via "click chemistry" in high yield and the self‐assembly characteristics were studied in different mixed solvents.