Protein nanotubes with an enzyme interior surface

This report describes the synthesis and enzyme activities of multilayered protein nanotubes with an α-glucosidase (αGluD) interior surface. The nanotubes were prepared by using an alternating layer-by-layer (LbL) assembly of human serum albumin (HSA) and oppositely charged poly-L-arginine (PLA) into a track-etched polycarbonate (PC) membrane (pore size=400 nm) followed by addition of αGluD as the last layer of the wall. Subsequent dissolution of the PC template yielded (PLA/HSA)(2)PLA/αGluD nanotubes. SEM measurements revealed the formation of uniform hollow cylinders with (413±17) nm outer diameter and (52±3) nm wall thickness. In aqueous media, the nanotubes captured a fluorogenic glucopyranoside, 4-methyl-umbelliferyl-α-D-glucopyranoside (MUGlc), into their one-dimensional pore space and hydrolyzed the substrate efficiently to form α-D-glucose. We determined the enzyme parameters (Michaelis constant, K(M), and catalytic constant, k(cat), values) of the protein nanotubes. The several-micrometers-long cylinders were of sufficient length to be spun down by centrifugation at 4000 g, so the product could therefore be easily separated. Similar biocatalysts were prepared by complexation of biotinylated-αGluD into HSA-based nanotubes bearing a single avidin layer as an internal surface. The obtained hybrid nanotubes also exhibited the same enzyme activity for the MUGlc hydrolysis.     

Enantioselective aza-Friedel–Crafts reaction catalyzed by a water inclusion complex of O,O′-diacyl tartaric acid

The efficiency of an O,O′-diacyl tartaric acid derivative as a chiral Brønsted acid catalyst was investigated in the enantioselective Friedel–Crafts reaction of indoles with an α-imino ester. The inclusion of water in the O,O′-di-p-toluoyl-d-tartaric acid catalyst is crucial for obtaining the enantioselectivity, and under optimal conditions the corresponding Friedel–Crafts product was obtained with an enantioselectivity of up to 88% ee.     

Skeletal Rearrangement of O‐Propargylic Formaldoximes by a Gold‐Catalyzed Cyclization/Intermolecular Methylene Transfer Sequence

Skeletal rearrangement of O‐propargylic formaldoximes, in the presence of gold catalysts, afforded 4‐methylene‐2‐isoxazolines in good to excellent yields by an intermolecular methylene transfer. In addition, the cascade reaction with maleimide in the presence of a gold catalyst afforded isoxazole derivatives by cyclization/methylene transfer and a subsequent ene reaction, whereas that using a copper catalyst gave oxazepines through a 2,3‐rearrangement.     

Facile synthesis of 5,10-diaryl-5,10-dihydrophenazines and application to EL devices

[structures: see text] An efficient method for the synthesis of 5,10-diaryldihydrophenazine was developed using a recently developed Pd(0)-mediated cross-coupling reaction. The products 1k and 3c showed excellent properties as hole injection materials in electroluminescent (EL) devices.     

Enantioselective Aza Michael‐Type Addition to Alkenyl Benzimidazoles Catalyzed by a Chiral Phosphoric Acid

Highly enantioselective Michael‐type addition (MTA) reactions between N‐protected alkenyl benzimidazoles and either pyrazoles or indazoles as nitrogen nucleophiles are accomplished for the first time using chiral phosphoric acid catalyst. Theoretical studies elucidated the reaction pathway and the origin of the stereochemical outcomes, where the catalyst substituent and the N‐protecting group of benzimidazole contributed to the resulting high enantioselectivity.     

Thermodynamic interactions in rubbery polymer/gas systems

The Flory–Huggins interaction parameters χ for 23 gases (He, Ne, Ar, Kr, Xe, H₂, N₂, O₂, N₂O, CO₂, CH₄, C₂H₄, C₂H₆, C₃H₆, C₃H₈, 1,3-C₄H₆, four C₄H₈'s, n-C₄H₁₀, iso-C₄H₁₀, and n-C₅H₁₂) in five rubbery polymers (1,2-polybutadiene (PB), poly(ethylene-co-vinyl acetate)) (EVAc), polyethylene (PE), polypropylene (PP), and poly(dimethyl siloxane) (PDMS) were determined from either literature data on Henry's law coefficient and partial molar volume or those on sorptive dilation for each polymer/gas system. Values of χ for the gases increased in the order of PDMS < PP ≡ PB < EVAc ≡ PE. Among the gases except He and H₂ whose χ values are not reliable, Ne and Xe have respectively the highest and the lowest values of χ for the polyolefins. The χ values of the hydrocarbons were compared together with previously reported χ values of n-alkanes C₃-C₁₀. The dependencies of χ upon concentration and temperature were discussed on the basis of the literature data. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1049–1053, 1997     

Antitumor agents. I. DNA topoisomerase II inhibitory activity and the structural relationship of podophyllotoxin derivatives as antitumor agents.

Various podophyllotoxin derivatives from desoxypodophyllotoxin (DPT) were synthesized to examine the structural relationships between the biological significance (cytotoxic effect, effects on DNA topoisomerase II and tubulin polymerization) in vitro and antitumor activity in vivo (L 1210). An intact 6,7-methylenedioxy group of DPT is necessary to inhibit tubulin polymerization and topoisomerase II. 4'-Phenolic hydroxyl group of DPT is essential to inhibit DNA topoisomerase II and the inhibitory effect on DNA topoisomerase II contributes to a high cytotoxicity. The introduction of an aminoalkoxy group at 1-position of DPT enhances the inhibitory activity against DNA topoisomerase II and cytotoxic effect, causing the inhibitory activity against tubulin polymerization to disappear. The results of antitumor test in mice bearing L 1210 on podophyllotoxin derivatives suggest the following: 1) the strong cytotoxic effect itself is not a good indication of antitumor activity in vivo as long as it is associated with inhibition of tubulin polymerization. DNA topoisomerase II inhibitory effect contributes to an antitumor activity in vivo; 2) detailed measurements of cytotoxicity and inhibition on DNA topoisomerase II and tubulin polymerization in vitro are necessary to evaluate podophyllotoxin derivatives.     

Formation of interpenetrated spherulites based on miscible crystalline polymer blends

The morphology and formation process of interpenetrated spherulites of poly(butylene succinate)/poly(vinylidene choloride‐co‐vinyl chloride) (PBSU/PVDCVC) blends were investigated by confocal laser scanning microscopy (CLSM). CLSM images showed that the dense fibrils of PBSU spherulites penetrated into the sparse PVDCVC spherulites. For a blend with PBSU content 50% and crystallization temperature T_c = 368 K, the simultaneous growth of PBSU and PVDCVC spherulites was observed. After PBSU fibrils collided with PVDCVC spherulites, they kept growing through PVDCVC spherulites. For a blend with PBSU content 30% and T_c = 363 K, PBSU started to nucleate after PVDCVC spherulites filled the whole space.