Antibacterial activities of polystyrene-block-poly(4-vinyl pyridine) and poly(styrene-random-4-vinyl pyridine)

Styrene was polymerized in the presence of benzoyl peroxide (BPO) and 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) to yield polystyrene-TEMPO (PS-TEMPO) macroinitiator. The PS-TEMPO macroinitiator with different molecular weight was reacted with 4-vinyl pyridine (4-VP) to synthesize polystyrene-block-poly(4-vinyl pyridine) (PS-b-PVP), which was then quaternized with n-octyl iodide. Antibacterial activity of the quaternized copolymers was assessed against a gram negative bacterium (Pseudomonas aeruginosa) and a gram positive one (Staphylococcus aureus) by using the shake flask test method, and the results were compared with those of poly(styrene-random-4-vinyl pyridine) (P(ST-r--VP)). The quaternized copolymers inhibited greatly the growth of the bacteria, and PS-b-PVP was more active than P(ST-r-VP), which was ascribed to the fact that the content of quaternized 4-VP units on the surface of the particles of the former copolymer was higher than that corresponding to the latter one.     

A unified and quantitative receptor model for the microtubule binding of paclitaxel and epothilone

[formula: see text] Paclitaxel and epothilone represent the two major classes of antimicrotubule agents that promote tubulin polymerization and, presumably, mitotic arrest during cell division. A common minireceptor binding site model at beta-tubulin has been constructed for these structurally divergent compounds. Utilizing 20 amino acids identified in photoaffinity labeling experiments, the 3-D model correlates measured and predicted Ki's with r = 0.99 and rms(delta Gcalc-delta Gexp) = 0.2 kcal/mol. In addition, the model predicts the affinity of compounds not used in the training set and explains much of the SAR for the paclitaxel and epothilone families.     

Simultaneous determination of60Co,131I and137Cs in model radioactive waste water by reverse radiometric flow injection analysis with the aid of a multichannel analyzer

Reverse radiometric flow injection analysis was used for the simultaneous determination of⁶⁰Co,¹³¹I and¹³⁷Cs in model radioactive waste water. A NaI (Tl) scintillation detector coupled to a Canberra MCA was used for measuring the activity of¹³⁷Cs at 662 keV,⁶⁰Co at 1173 keV and 1332 keV, and¹³¹I at 364 keV.     

Determination of water-soluble vitamins in pharmaceutical preparations by reversed-phase high-performance liquid chromatography with a mobile phase containing sodium dodecylsulphate andn-propanol

Summary A reversed-phase liquid chromatographic method with sodium dodecylsulphate-n-propanolwater as mobile phase has been used to separate and determine six water-soluble vitamins in twelve minutes. The analytical characteristics linear range, sensitivity, detection limits, and precision were evaluated. The lowest detection limits were those of nicotinic acid (not usually present in pharmaceutical products), 0.7 mgL⁻¹, nicotinamide, 1.3 mg L⁻¹, and pyridoxine, 1.4 mg L⁻¹. When the method was applied to the determination of the vitamins in pharmaceutical samples the values found agreed with those on the labels.     

Construction of a 2,6-difunctionalized 2-methyl-2H-1-benzopyran library by using a solid-phase synthesis protocol

[reaction: see text] A library containing 1200 analogues of 2,6-difunctionalized 2-methyl-2H-1-benzopyran was constructed by using a solid-phase synthesis protocol. Polymer-bound 6-amido-, 6-sulfonamido-, and 6-uredo-functionalized 2-hydroxymethyl-2-methylbenzopyrans 10 were prepared as part of a first-generation diversification step by employing reactions of respective acid halides, sulfonyl chlorides, and isocyanates with the amine precursor 7. Transformations of the resin-bound intermediates 10 by reactions with alkyl and acid halides were then used to produce a diverse series of 2,6-difunctionalized 2-methyl-2H-1-benzopyran analogues 12 and 14.     

Field and flow programming in frit-inlet asymmetrical flow field-flow fractionation

The separation of wide molecular mass (Mr) ranges of macromolecules using frit inlet asymmetrical flow field-flow fractionation (FI-AFlFFF) has been improved by implementing a combination of field and flow programming. In this first implementation, field strength (governed by the cross flow-rate through the membrane-covered accumulation wall) is decreased with time to obtain faster elution and improved detection of the more strongly retained (high Mr) materials. The channel outlet flow-rate is optionally held constant, increased, or decreased with time. With circulation of the flow exiting the accumulation wall to the inlet frit, the dual programming of cross flow and channel outlet flow could be implemented using just two pumps. With this flow configuration, the channel outlet flow-rate is always equal to the channel inlet flow-rate, and these may be programmed independently of the cross flow-rate through the membrane. FI-AFlFFF retains its operational advantage over conventional asymmetrical flow FFF (AFlFFF). Unlike conventional AFlFFF, FI-AFlFFF does not require time consuming, and experimentally inconvenient, sample focusing and relaxation steps involving valve switching and interruption of sample migration. The advantages of employing dual programming with FI-AFlFFF are demonstrated for sets of polystyrene sulfonate standards in the molecular mass range of 4 to 1000 kDa. It is shown that programmed FI-AFlFFF successfully expands the dynamic separation range of molecular mass.     

Growth promotion of HepG2 hepatoma cells by antisense-mediated knockdown of glypican-3 is independent of insulin-like growth factor 2 signaling

Glypican-3 (GPC3) encodes a cell-surface heparan- sulfate proteoglycan and its expression is frequently silenced in ovarian cancer, mesotheliomas, and breast cancer cell lines and ectopic expression of GPC3 inhibited the growth of these cells, suggesting that GPC3 plays a negative role in cell proliferation. In contrast, up-regulation of GPC3 is often observed in hepatoma, neuroblastoma, and Wilms' tumor. Whether GPC3 plays the same growth inhibitory role in these tumors remains to be studied. Here we report that antisense-mediated knockdown of GPC3 in the HepG2 hepatoma cells significantly promotes the growth of hepatoma cells. In addition, we show that this growth promotion is independent of insulin-like growth factor 2 (IGF2) signaling. Our data suggest that GPC3 plays a growth-suppressing role in hepatoma and provide cell biological evidence inconsistent with the hypothesis that GPC3 acts as a growth suppressor by downregulating IGF2.     

Covalent-ionic nature of the potential energy surface of the Li-CO2 complex

Unrestricted Hartree-Fock calculations with large basis sets, including d-functions, and the estimation of the correlation energy, show that the potential energy surface for the Li-CO₂ complex is built from the crossing of two states, each of them corresponding to a different electron arrangement. One has a strong ionic character and the other is of van der Waals type. Each portion of the energy surface presents a minimum, which is stable in respect to the dissociation limit.