Spiroquinazoline support studies: methods for the preparation of imidazoloindolines from oxindoles

Two methods for the annulation of glycine to the 1 and 2 positions of oxindoles are described. The first method involves introduction of an α-azidoacetyl group on the oxindole nitrogen followed by an intramolecular Staudinger reaction to complete the annulation. The second method involves acylation of the oxindole nitrogen with an N-Cbz-glycine derivative followed by reduction of the oxindole carbonyl group and subsequent cyclization to provide an imidazoloindoline.     

Translocation of a beta-peptide across cell membranes.

Short cationic peptides derived from DNA-binding proteins, of which HIV Tat is a prototype, can cross the membranes of living cells, and they can bring covalently attached moieties (proteins, drugs) along with them. We show that a beta-amino acid analogue of Tat 47-57 enters HeLa cells with comparable efficiency to Tat 47-57 itself (YGRKKRRQRRR). The beta-peptide is comprised of residues that bear the appropriate side chain at the beta-carbon. Both the alpha- and the beta-peptide were conjugated to fluorescein at the N terminus, and cell penetration was monitored by confocal fluorescence microscopy. Deletion of the three C-terminal arginine residues from the alpha-peptide abolished translocation activity, consistent with prior reports, and deletion of the three C-terminal beta3-homoarginine residues from the beta-peptide had a similarly adverse effect. Thus, alpha- and beta-peptide translocation processes show similar length/charge dependence. The beta-peptide appeared to be largely unfolded in water, which is consistent with the behavior of short Tat-derived alpha-peptides, but in methanol the beta-peptide adopted a helical conformation, in contrast to short Tat-derived alpha-peptides. Our results show that neither altering the oligomeric backbone (amide group spacing) nor increasing the intrinsic propensity to adopt a specific secondary structure affects translocation activity.     

Studies of polyester fiber as carrier for microbes in a quantitative test method for disinfectants

Tests were conducted by a Task Force on Disinfectant Test Methods that was appointed to investigate controversies regarding the accuracy of AOAC test methods for disinfectants as presented in AOAC's Official Methods of Analysis, Chapter 6. The general principles for new and improved AOAC tests are discussed, and a disinfectant test using microbes labeled onto a polyester fiber surface is described. The quantitative test measures the survival of test microbes as a function of exposure time as well as the exposure conditions required to kill 6 log10 of the test microbes. The time required was similar to that for the kinetics of the kill of Bacillus subtilis-labeled cylinders as tested by methods of the AOAC Sporicidal Test 966.04.     

Structure of the co-crystalline solid formed between 1,4-dichloronaphthalene-2,3-diol and dioxane

The 1,4-dichloro-(1) and 1,4-dibromo-(2) derivatives of naphthalene-2,3-diol crystallise in structures containing acetic acid or dioxane solvent molecules. X-ray crystallographic examination of the compound formed between1 and dioxane is reported here [(C₁₀H₆Cl₂O₂)₂·(C₄H₈O₂),P2₁/c,a=12.358(3),b=4.9930(7),c=19.167(4) Å,β=96.09(1)⁰,Z=2,R=0.035] and this structure is analysed in crystal engineering terms. The compound is a co-crystalline material involving two types of hydrogen bonding: one phenolic group participates in a $$\begin{gathered} ...{\text{OH }}...{\text{OH }}...{\text{OH}} \hfill \\ {\text{ | | |}} \hfill \\ {\text{ Ar Ar Ar}} \hfill \\ \end{gathered} $$ chain, while the second phenolic group hydrogen bonds to a dioxane. Extension of the hydrogen bonding network through the second dioxane oxygen results in heavily corrugated layers. Neighbouring layers interact by a combination of aromatic face-face and edge-face interactions similar to a partial coronene-type γ packing to complete the structure.     

Expanded-bed adsorption utilizing ion-exchange resin to purify extracellular β-galactosidase

The application of expanded-bed ion-exchange resins allows the elimination of intermediary particulate separation steps like filtration or centrifugation prior to adsorption steps in enzyme-purification processes from crude fermentation broths. This work is concerned with the experimental evaluation data of a process related to the adsorption of an extracellular p-galactosidase from the fungiScopulariopsis. The protein recovery in the ion-exchange resin Accell Plus QMA™ was accomplished using a continuous-monitoring method. The direct adsorption step was followed by a elution step with concentrated NaCl solutions aiming to improve the enzyme-specific activity. Experimental data for fixed and expanded bed were compared     

The Dynamics of Marangoni-Driven Local Film Drainage between Two Drops

A study of Marangoni-driven local continuous film drainage between two drops induced by an initially nonuniform interfacial distribution of insoluble surfactant is reported. Using the lubrication approximation, a coupled system of fourth-order nonlinear partial differential equations was derived to describe the spatio-temporal evolution of the continuous film thickness and surfactant interfacial concentration. Numerical solutions of these governing equations were obtained using the Numerical Method of Lines with appropriate initial and boundary conditions. A full parametric study was undertaken to explore the effect of the viscosity ratio, background surfactant concentration, the surface Péclet number, and van der Waals interaction forces on the dynamics of the draining film for the case where surfactant is present in trace amounts. Marangoni stresses were found to cause large deformations in the liquid film: Thickening of the film at the surfactant leading edge was accompanied by rapid and severe thinning far upstream. Under certain conditions, this severe thinning leads directly to film rupture due to the influence of van der Waals forces. Time scales for rupture, promoted by Marangoni-driven local film drainage were compared with those associated with the dimpling effect, which accompanies the approach of two drops, and implications of the results of this study on drop coalescence are discussed. Copyright 2001 Academic Press.     

Correlation between isoniazid resistance and superoxide reactivity in mycobacterium tuberculosis KatG

Isoniazid is an antituberculosis prodrug that requires activation by the catalase-peroxidase (KatG) of Mycobacterium tuberculosis. The activated species, presumed to be an isonicotinoyl radical, couples to NADH forming an isoniazid-NADH adduct that ultimately confers antitubercular activity. We have compared the catalytic properties of three KatGs associated with isoniazid resistance (resistance mutation KatGs, (RM)KatGs: R104L, H108Q, S315T) to wild-type enzyme and two additional lab mutations (wild-type phenotype KatGs, (WTP)KatGs: WT KatG, Y229F, R418L). Neither catalase nor peroxidase activities, nor the presence/absence of the Met-Tyr-Trp cross-link (as probed by LC/MS on tryptic digests of the protein), exhibited any correlation with isoniazid resistance. The yields of isoniazid-NADH adduct formed were determined to be 1-5, 4-12, and 20-70-fold greater for the (WTP)KatGs than the (RM)KatGs for the compound I, II, and III pathways, respectively, strongly suggesting a role for oxyferrous KatG (supported by superoxide consumption measurements) that correlates with drug resistance. Stopped-flow UV-visible spectroscopic studies revealed that all KatGs were capable of forming both compound II and III intermediates. Rates of compound II decay were accelerated 4-12-fold in the presence of isoniazid (vs absence) for the (WTP)KatGs but were unaffected by the drug for the (RM)KatGs. A mechanism for isoniazid resistance which accounts for the observed reactivity for each of the compound I, II, and III intermediates is proposed and suggests that the compound III pathway may be the primary factor in determining overall isoniazid resistance by specific KatG mutants, with secondary contributions arising from the compound I and II pathways.     

A straightforward synthesis of (-)-phaseolinic acid

A concise approach to (-)-phaseolinic acid starting from commercially available (S)-oct-1-yn-3-ol is disclosed. The key steps are a ring-closing metathesis reaction to prepare a C(2)-symmetrical allylic diol and its desymmetrization to a gamma-butyrolactone by using an Ireland-Claisen rearrangement. The 2S,3S,4S configuration of the levogyre natural product has been confirmed.     

Mixtures formed of alkyl acetates with olive oil at 298.15 k

Enthalpies of mixing and heat capacities of the systems formed of alkyl acetates (ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate and isobutyl acetate) with olive oil were measured at 298.15 K. The mixing of acetates with the oil was strongly endothermic, and the highest measured enthalpies per mole of mixture were 2000 J mol^-1 for ethyl acetate at an acetate mole fraction of 0.6. The heat capacities of the mixtures were calculated too and values were decreasing as the mole fraction of acetate increases and varied from 296 to 3929 J K^-1 mol^-1. This revised version was published online in July 2006 with corrections to the Cover Date.     

Carbohydrate-derived spiroketals. Stereoselective synthesis of di-D-fructose dianhydrides by boron trifluoride promoted glycosylation-spiroketalization of acetal precursors

[reaction: see text] Di-D-fructose 1,2':2,1'-dianhydrides, dispiro-tricyclic disaccharides widely found in food materials, have been stereoselectively prepared in one-pot reaction from O-protected D-fructose 1,2-acetonide precursors by treatment with boron trifluoride diethyl etherate. The dimerization sequence involves (i) cleavage of the anomeric acetal linkage, (ii) autoglycosylation, and (iii) final spiroketalization, the stereochemical outcome being strongly dependent on the nature of the hydroxyl protecting groups.