Structure changes on polymer blends by means of phase growth on microheterophase surface

We have studied the structural changes on poly(2-hydroxyethyl methacrylate) (PHEMA)/polystyrene (PS) blends by means of phase growth of microheterophase pattern on a template surface composed of poly[2-hydroxyethyl methacrylate (HEMA)-g-styrene (S)] graft copolymer (lamellar shape). The PS macromonomer was synthesized by free radical polymerization of S monomer initiated by a functional initiator [2,2'-azobis(2-(2-imidazolin-2-yl)propane: VA-061] in the presence of a degradative chain transfer agent, followed by an end-capping reaction with p-chloromethylstyrene (CMS). Poly(HEMA-g-S) graft copolymers were prepared by free radical copolymerization of these vinylbenzyl-terminated PS macromonomers with HEMA comonomer.     

EFFECTS OF N-PHENYLIMIDE S-23142 AND N-METHYL MESOPORPHYRIN IX ON THE SYNTHESIS OF THE PHYTOCHROME CHROMOPHORE IN PEA EMBRYONIC AXES

Abstract Treatment of imbibed embryonic axes taken from seeds of Pisum sativum with N-phenylimide S-23142, a herbicide that has been suggested to inhibit protoporphyrin synthesis, or with N -methyl mesoporphyrin IX, an inhibitor of the iron chelatase for heme, resulted in a significant decrease in the amount of spectrophotometrically detectable phytochromc in the axes in both cases. However, the amount of immunochemically detectable phytochrome was not affected by either treatment. If S-23142 inhibits the synthesis of protoporphyrin IX in pea, it appears that the conversion of protoporphyrinogen IX to protoporphyrin IX is involved in the biosynthesis of the phytochrome chromophore. The conversion of protoporphyrin IX to heme (Fe-protoporpbyrin) also appears to be a step in the biosynthesis of the chromophore, since N -methyl mesoporphyrin IX prevented the synthesis of spectrophotometrically detectable phytochrome but did not affect the magnesium chelatase activity required for the synthesis of chlorophyll in pea embryonic axes. The results suggest that protoporphyrinogen IX, protoporphyrin IX and heme are intermediates in the biogenesis of the phytochromc chromophore. The pathway to phytochromobilin might become fixed after protoporphyrin IX, being directed toward the Fe branch for heme rather than to the Mg branch for chlorophyll.     

Solvent effect on protein binding by polymer brush grafted onto porous membranes

An epoxy-group-containing polymer chain was grafted onto the hollow-fiber form of a porous polyethylene membrane by the immersion of the electron beam-irradiated trunk polymer in glycidyl methacrylate diluted with methanol and 1-butanol. The epoxy group density ranged from 8.5 to 13.4 mol per kg of the trunk polymer. Subsequently, the epoxy groups produced were converted into sulfonic acid and diethylamino groups. The density of -SOH and -N(C2H5), groups was 0.40 and 2.2 mol per kg of the product. respectively. The polymer brush, defined as a polymer chain extending from the surface of a pore toward the interior of the pore, was evaluated from the determination of an equilibrium binding capacity of hen egg lysozyme (HEL) and bovine serum albumin (BSA). The polymer brush prepared in 1-butanol was found to be longer than that prepared in methanol from the determinations of liquid permeability and protein adsorptivity. The proteins were bound to the polymer brush prepared in 1-butanol, followed by the functionalization, at higher degrees of multilayer binding: about 30 for HEL and 6 for BSA.     

Synthesis of poly (ethylene oxide)-b-polysilane by anionic polymerization of masked disilenes using a macroinitiator method

Poly(ethylene oxide-)-poly(1, 1-dimethyl-2, 2-dihexyldisilene) block copolymers (PEO-b-PMHS) were synthesized by the anionic polymerization of masked disilenes initiated with the potassium alkoxide of poly(ethylene glycol). The block copolymer self-assembled into polymer micelles in water accompanied by a transition in the polysilane conformation.     

Organometallic compounds : XII. stereochemical interconversion reactions between 1,1′−bis(α-hydroxyalkyl)ferrocenes and 7-oxa[3]ferrocenophanes

Meso and racemic isomers of 1,1′-bis(α-hydroxyalkyl)ferrocene derivatives, and trans and cis isomers of 7-oxa[3]ferrocenophanes have been isolated. The configurations of these isomers have been determined both by spectroscopy and from their reaction behavior. It has been found that the ring-closure and ring-opening interconversion reactions between 1,1′-bis(α-hydroxyalkyl)ferrocenes and 7-oxa[3]ferrocenophanes are stereospecific. PMR spectra of the diols and ethers have been examined at 100 MHz in CF₃COOH, and the existence of α-[1′-(α-hydroxyalkyl)ferrocenyl]carbonium ions has been demonstrated in this acid. A mechanism for the various interconversion reactions is proposed on the basis of their stereospecific reactivity and from the PMR spectra of the carbonium ions.     

Fluorescence quenching of pyrene and pyrenedecanoic acid by various kinds of N,N-dialkylanilines in dipalmitoylphosphatidylcholine liposomes

Fluorescence quenching of pyrene and pyrenedecanoic acid by various kinds of anilines has been studied in dipalmitoylphosphatidylcholine liposomes in gel phases. N,N-dimethylaniline and p-isopropyl-N,N-dimethylaniline caused anisotropic diffusional quenching, while N,N-dicetylaniline, a less mobile quencher, predominantly caused static quenching. These data suggested the location sites of both pyrenes and anilines in the membranes.     

Chromium- and tungsten-triggered valence isomerism of cis-1-acyl-2-ethynylcyclopropanes via [3,3]sigmatropy of (2-acylcyclopropyl)vinylidene-metal intermediates.

The reaction of cis vicinal acetylethynylcyclopropanes 1 with a catalytic amount of M(CO)5(THF) (M = Cr or W) in the presence of Et3N at room temperature gave ortho-substituted phenols 7 in good yields as valence isomerized products. In the absence of Et3N the reactions did not work at all. The reaction of a cyclopropane having an ester or an amide instead of an acetyl moiety with M(CO)5(THF) did not take place, whereas an ethynylvinylcyclopropane gave a mixture of 1- and 2-substituted 1,3,5-cycloheptatrienes. These valence isomerization reactions are assumed to proceed via the formation of vinylidene-metal intermediates 2 from terminal alkynyl moieties followed by [3,3]sigmatropy of 2 to give seven-membered carbene complexes 3.     

Photoaffinity labeling of bovine rhodopsin

Photoaffinity labeled (3-diazoacetoxy)-9-cis-retinal (1) and (9-methylenediazoacetoxy)-9-cis-retinal (20) were synthesized and bound to absorption maxima at 465 and 460 nm respectively. Binding studies established that synthetic retinals 1 and 2 bind to the natural binding site and that the integrity of the diazoacetoxy photoaffinity label is preserved in the process. Incorporation of 3-(O¹⁴COCHN₂)-labeled 9-cis retinal could be conveniently carried out in high yield using apomembrane solubilized in CHAPS as detergent to afford the pigment analog in a pure form. Photolysis of the diazoacetoxy group within the binding site led to 15–20%, crosslinking of rhodopsin as estimated by using radiocarbon containing labeled retinal 1 thus showing that this synthetic retinal is suitable for photoaffinity labeling of the active site in rhodopsin. Subsequent experiments to establish the site(s) of crosslinking by sequencing studies will then contribute to our knowledge of the structure of rhodopsin.     

Synthesis of new peptidic glycoclusters derived from β-alanine

The synthesis of an asymmetric glycocluster 1 has been achieved by coupling of a sugar unit with the β-alanine polypeptide, the principal chain, and combining a carbohydrate chain with the side chain causing it to branch from the N terminal. The synthesis of this side chain multivalent ligands is based on the scaffolding of some ω-amino acid (glycine, β-alanine, and GABA) derivatives. This method facilitated the synthesis of the cluster, of which the length of each unit differs.     

Sol-Gel Processing of Transparent PLZT((Pb,La)(Zr,Ti)O3) Fibers

PLZT((Pb,La)(Zr,Ti)O₃) ceramic fibers were prepared by the sol-gel method from a solution of lead acetate trihydrate, lanthanum isopropoxide, zirconium n-propoxide and titanium isopropoxide containing 2-methoxyethanol as the solvent. The as-drawn gel fibers were pretreated in an autoclave and preheated in flowing H₂O vapor prior to the heat-treatment for crystallization. The effects of autoclaving and preheating in flowing H₂O vapor on the structure and composition of the resultant fibers were investigated. Optically transparent single phase perovskite PLZT fibers of 5–15 m in thickness and 5 cm in length were successfully prepared when the autoclave-treatment and the preheating in flowing H₂O vapor were conducted prior to crystallization. These treatments are thought to promote hydrolysis of the organic groups and polycondensation reaction in the gel fibers, leading to the successful formation of dense, crack-free transparent PLZT fibers.