Relationship between human IgG structure and retention time in hydroxyapatite chromatography with sodium‐phosphate gradient elution

The aim of this study was to classify the retention time of recombinant human monoclonal antibodies (rhMAbs) in hydroxyapatite chromatography with sodium‐phosphate gradient elution according to their physicochemical properties. We analyzed 37 rhMAbs and found that (i) the structures of both the constant and variable regions affected retention time, (ii) the number of basic amino acid residues in the variable region, particularly in the heavy chain, correlated well with retention time, and (iii) this correlation was more pronounced (e.g. r²=0.87 for 18 κ IgG₁ rhMAbs) when the surface accessibility of those residues are taken into account. These findings provide a useful guide for investigators and purification‐process developers working with monoclonal antibodies.     

Palladium-catalyzed asymmetric alkylation of 2-azaallyl acetates for the synthesis of β-carboxyaspartic acid derivatives

Palladium-catalyzed asymmetric alkylation of 2-azaallyl acetate, N-(diphenylmethylene)acetoxyglycine ester with a sodium salt of malonate ester was successfully carried out. High enantioselectivities were achieved using sodium dimethyl methylmalonate (98%ee) or sodium dimethyl malonate (93%ee) as a nucleophile with t-butyl ester of 2-azaallyl acetate in the presence of (S)-BINAP in acetonitrile.     

Preparation of substituted network polysilanes by a disproportionation reaction of ethoxydisilane initiated by a small amount of organolithium reagents

Network methylethoxypolysilanes containing various substituents such as phenyl, butyl, phenylene, thiophene, and anthracene groups were prepared by a disproportionation reaction of 1,1,2,2-tetraethoxy-1,2-dimethyldisilane initiated by addition of a small amount of organolithium reagents that have the corresponding substituents. The reaction was considered to be catalyzed by lithium ethoxide, which was formed by the substitution reaction of the ethoxydisilane with the lithium reagents. Both the substituted and pristine disilanes participated in the disproportionation reaction to yield the network polysilanes. The amount of the substituents and the molecular weight of the polysilanes varied, depending on what and how much of the lithium reagent were used. The electrical conductivity of some polysilanes was measured, and polymers with thiophene or anthracene groups were found to show relatively higher conductivity of 10⁻⁴ Scm⁻¹ after iodine doping. © 1997 John Wiley & Sons, Inc.     

Synthesis of Cristobalite Containing Ordered Interstitial Mesopores using Crystallization of Silica Colloidal Crystals

Cristobalite with ordered interstitial dual-sized mesopores was synthesized through the crystallization of silica colloidal crystals composed of monodispersed amorphous silica nanoparticles. An aqueous solution containing both a flux (Na₂O) and a carbon precursor (an aqueous low-molecular weight phenolic resin) was infiltrated into the interstices of silica colloidal crystals. The organic fraction in the nanocomposite was further polymerized and subsequently carbonized in an Ar flow at 750 °C to reinforce the colloidal crystal structure. The thermal treatment resulted in the crystallization of the colloidal crystals into cristobalite while retaining the porous structure. The cristobalite-carbon nanocomposite was calcined in air to remove the carbon and create interstitial ordered mesopores in the cristobalite. The surfaces of crystalline mesoporous silica are quite different from those of various ordered mesoporous silica with amorphous frameworks; thus, the present findings will be useful for a precise understanding and control of the interfaces between the mesopores and silica networks.     

Heterogeneously catalyzed efficient hydration of alkynes to ketones by tin-tungsten mixed oxides

The Sn–W mixed oxide prepared by calcination of the Sn–W mixed hydroxide precursor with a Sn/W molar ratio of 2:1 at 800 °C (SnW2‐800) acts as an efficient heterogeneous catalyst for the hydration of alkynes. Structurally diverse terminal and internal alkynes, including aromatic, aliphatic, and double‐bond‐containing ones, can be converted into the corresponding ketones in moderate to high yields. The catalytic activity of SnW2‐800 is much higher than those of previously reported heterogeneous catalysts and commonly utilized acid catalysts. The observed catalysis was truly heterogeneous, and the retrieved catalyst can be reused at least three times with retention of its high catalytic performance. The reaction rate for the SnW2‐800‐catalyzed hydration was decreased by addition of 2,6‐lutidine and the hydration hardly proceeded in the presence of an equimolar amount of this compound with respect to that of the Brønsted acid sites in SnW2‐800. Therefore, the present hydration is mainly promoted by the Brønsted acid sites in SnW2‐800.     

Stereoselective synthesis of cis-2,5-disubstituted THFs: application to adjacent bis-THF cores of Annonaceous acetogenins

The iodocyclization of γ,δ-unsaturated alcohols in the presence of a silyl enol ether produced cis-2,5-disubstituted tetrahydrofurans in one pot via siloxy intermediates. N-Iodosuccinimide (NIS) effectively worked as an activator of the double bonds in the substrates and the silyl enol ether. Application to an expedient synthesis of the adjacent bis-tetrahydrofuran core of Annonaceous acetogenins with a cis/threo/cis relative stereochemistry is also described.     

Effects of Annealing on the Mechanical Properties of Pentacene and Tris(8-hydroxyquinoline) Aluminum Films

Annealing is reported as an effective process to improve electrical properties of organic semiconducting films. The mechanical properties of pentacene and tris(8-hydroxyquinoline) aluminum (Alq₃) films annealed at 140°C were investigated in this study by nanoindentation testing. AFM observations of as-coated and annealed pentacene films indicate grain growth from 160 to 258 nm. The annealing process decreases pentacene and Alq₃ film hardness by 23 and 36% from those of the as-coated films, 0.643 and 0.523 GPa. Grain growth and decreasing hardness are attributed to thermal diffusion and recrystallization of molecules.