Nonequilibrium synthesis and assembly of hybrid inorganic-protein nanostructures using an engineered DNA binding protein

We show that a protein with no intrinsic inorganic synthesis activity can be endowed with the ability to control the formation of inorganic nanostructures under thermodynamically unfavorable (nonequilibrium) conditions, reproducing a key feature of biological hard-tissue growth and assembly. The nonequilibrium synthesis of Cu(2)O nanoparticles is accomplished using an engineered derivative of the DNA-binding protein TraI in a room-temperature precursor electrolyte. The functional TraI derivative (TraIi1753::CN225) is engineered to possess a cysteine-constrained 12-residue Cu(2)O binding sequence, designated CN225, that is inserted into a permissive site in TraI. When TraIi1753::CN225 is included in the precursor electrolyte, stable Cu(2)O nanoparticles form, even though the concentrations of [Cu(+)] and [OH(-)] are at 5% of the solubility product (K(sp,Cu2O)). Negative control experiments verify that Cu(2)O formation is controlled by inclusion of the CN225 binding sequence. Transmission electron microscopy and electron diffraction reveal a core-shell structure for the nonequilibrium nanoparticles: a 2 nm Cu(2)O core is surrounded by an adsorbed protein shell. Quantitative protein adsorption studies show that the unexpected stability of Cu(2)O is imparted by the nanomolar surface binding affinity of TraIi1753::CN225 for Cu(2)O (K(d) = 1.2 x 10(-)(8) M), which provides favorable interfacial energetics (-45 kJ/mol) for the core-shell configuration. The protein shell retains the DNA-binding traits of TraI, as evidenced by the spontaneous organization of nanoparticles onto circular double-stranded DNA.     

Dynamic capillary coatings with zwitterionic surfactants for capillary isoelectric focusing

The use of surfactants as additives was demonstrated for the first time in capillary isoelectric focusing (CIEF) to dynamically modify the surfaces of bare fused silica capillaries. These surfactants were zwitterionic sulfobetaines: dodecyldimethyl (3-sulfopropyl) ammonium hydroxide (C12N3SO3), hexadecyldimethyl (3-sulfopropyl) ammonium hydroxide (C16N3SO3) and coco (amidopropyl)hydroxyldimethylsulfobetaine (Rewoteric AM CAS U). They were added directly to the protein-ampholyte mixture, and remained in the capillary during isoelectric focusing and mobilization. The C16N3SO3 and CAS U coatings were shown effective in CEF. Separation of seven IEF protein standards was obtained, with significantly improved resolution compared to that from an uncoated silica capillary. The effect of these surfactants on the electroosmotic flow (EOF) in CIEF was determined. CAS U was effective in suppressing the EOF at neutral and alkaline pH conditions, C16N3SO3 was effective in suppressing EOF at acidic and neutral pH conditions. C12N3SO3 however had little effect on the EOF. The pH gradients formed inside these surfactant coated capillaries were recta-linear at pH 6 to 9 (R2 approximately equal to 0.99). Reproducibility of migration time and peak area was determined. For all three coatings, the migration time standard deviations were less than 1.6 min, and the relative standard deviations of area were below 10%. The protein recovery in the CAS U-modified capillary was quantitative or near-quantitative for five of the seven proteins studied.     

Short synthesis of the CDEF ring system of lactonamycin

[reaction: see text]. A synthesis of the CDEF fragment of lactonamycin is achieved in eight steps (six pots) from the known and readily available anhydride 4 via a Diels-Alder reaction between tricycle 13 and 2,3-dimethylbenzoquinone.     

Separation and determination of seven fluoroquinolones by pressurized capillary electrochromatography

In this paper, pressurized CEC was used for the separation and determination of seven fluoroquinolones (FQs). The effect of different experimental conditions, such as the concentration and pH of the buffer, the organic modifier concentration, the surfactant and ion-paring agents added to the electrolyte, and applied voltage were studied. All the seven FQs were baseline separated using mobile phase containing 27% v/v ACN, 5 mmol/L Na2HPO4 buffer (pH 4.0 adjusted using citric acid), 11 mmol/L SDS, and 0.01% TEA v/v at detection wavelength of 287 nm and at an applied voltage of -10 kV. The calibration curves were linear (r>0.9991) over a concentration range of 1.0-50.0 mg/L for norfloxacin (NFLX); 2.5-50.0 mg/L for fleroxacin (FLX), ciprofloxacin (CPFX), and lomefloxacin (LMX); and 5.0-50.0 mg/L for enoxacin (ENX), ofloxacin (OFLX), and gatifloxacin (GFLX). The detection limits (S/N = 3) for ENX, OFLX, FLX, NFLX, CPFX, LMX, and GFLX were 0.5, 0.8, 0.4, 0.2, 0.4, 0.5, and 1.0 mg/L, respectively. The method is simple, rapid, and reproducible. It was successfully applied to the analysis of fish muscle samples spiked with FQs. Mean recoveries ranged from 81.6 to 97.6%.     

Simultaneous separation and determination of seven isoflavones in Radix Puerariae by capillary electrophoresis with a dual cyclodextrin system

A simple, comprehensive and efficient capillary electrophoresis method using a dual cyclodextrin system was developed for the simultaneous determination of seven isoflavones (3′‐methoxypuerarin, puerarin, 3′‐hydroxypuerarin, ononin, daidzin, daidzein and genistin). Baseline separations of the seven isoflavones were achieved within 11 min with the running buffer consisting of 35 mm sodium tetraborate, 9.0 mm sulfobutylether‐β‐cyclodextrin and 30 mm α‐cyclodextrin at pH 9.34, and peaks were detected at 254 nm. Other separation parameters included the separation voltage for 15 kV and the working temperature for 25°C. Under the optimum conditions, good linearities were obtained with linear correlation coefficients of seven isoflavones of 0.9978–0.9992. The limits of detection and the limits of quantification were 0.7–2.9 and 2.5–9.5 μg/mL, respectively. Excellent precision and accuracy were obtained. The intraday and interday precision ranged from 0.7 to 2.0% and from 0.8 to 1.9%, respectively. The recoveries of seven analytes were from 97.7 to 103.1%. This method was successfully applied to determine the seven analytes in Radix Puerariae and its preparations.     

Synthesis,crystal structure and antifungal activity of a divalent cobalt(II) complex with uniconazole

Azole compounds have attracted commercial interest due to their high bactericidal and plant‐growth‐regulating activities. Uniconazole [or 1‐(4‐chlorophenyl)‐4,4‐dimethyl‐2‐(1H‐1,2,4‐triazol‐1‐yl)pent‐1‐en‐3‐ol] is a highly active 1,2,4‐triazole fungicide and plant‐growth regulator with low toxicity. The pharmacological and toxicological properties of many drugs are modified by the formation of their metal complexes. Therefore, there is much interest in exploiting the coordination chemistry of triazole pesticides and their potential application in agriculture. However, reports of complexes of uniconazole are rare. A new cobalt(II) complex of uniconazole, namely dichloridotetrakis[1‐(4‐chlorophenyl)‐4,4‐dimethyl‐2‐(1H‐1,2,4‐triazol‐1‐yl‐κN⁴)pent‐1‐en‐3‐ol]cobalt(II), [CoCl₂(C₁₅H₁₈ClN₃O)₄], was synthesized and structurally characterized by element analysis, IR spectrometry and X‐ray single‐crystal diffraction. The crystal structural analysis shows that the Co^II atom is located on the inversion centre and is coordinated by four uniconazole and two chloride ligands, forming a distorted octahedral geometry. The hydroxy groups of an uniconazole ligands of adjacent molecules form hydrogen bonds with the axial chloride ligands, resulting in one‐dimensional chains parallel to the a axis. The complex was analysed for its antifungal activity by the mycelial growth rate method. It was revealed that the antifungal effect of the title complex is more pronounced than the effect of fungicide uniconazole for Botryosphaeria ribis, Wheat gibberellic and Grape anthracnose.     

变限积分的求导方法

结合实例归纳总结不同类型变限积分的求导方法．