摘要:

Hypochromic effects of 2-(thymin-1-yl)propionyl graft polyethylenimine (P-T) and its related monomer (M-T) and dimer model (D-T), and 2-(adenin-9-yl)propionyl graft polyethylenimine (P-A) and its monomer (M-A) and dimer model (D-A) have been systematically investigated, and the base-stacked conformation in comparison with corresponding polynucleotides and dinucleotides has been discussed. The results suggest that the graft polymers and even their dimer models may have a particular preference for a stacked conformation compared with the corresponding poly- and dinucleotides. A study of solvent effect on the NMR spectra of the dimer model suggests the existence of a preferred base-stacked conformation. Base pairing effects between the complementary bases have also been studied for various combinations among the model systems. Only the combination P-T/P-A showed a considerable hypochromic effect.

ISSN:0022-233X    

DOI:10.1080/00222337908056675

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The preparation of bilayer membranes from synthetic dialkyl amphiphiles is described. According to the electron microscopic observation, the bilayer structure similar to that of biomembranes is formed spontaneously when dialkyldimethyl-ammonium bromides with C10-C20alkyl groups are dispersed in water by sonication. The line broadening in the NMR spectrum strongly suggests that these synthetic bilayers constitute liquid crystalline or solid phases. The hydrophilic head group may be sulfonium and modified ammonium moieties. The bilayer assembly is also formed from dialkyl amphiphiles with anionic head groups: (phosphate, sulfonate, and carboxylate), from nonionic dialkyl amphiphiles (oligomeric ethylene oxide) moiety) and from zwitterionic dialkyl amphiphiles. These bilayers incorporate equimolar cholesterol fairly readily. The redistribution of catalyst (a cholesterol derivative) and substrate (p-nitrophenyl palmitate) molecules is very slow when they are tightly bound to the aggregate. The intravesicle reaction is much faster than the intervesicle counterpart in the case of the di-dodecyldimethylammonium bromide vesicle.

ISSN:0022-233X    

DOI:10.1080/00222337908056676

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

There is a need for hydrophilic polymeric microspheres with functional groups on their surface which can be reacted efficiently with proteins. These microspheres with antibodies (immunoglobulins) covalently bound to their surfaces constitute valuable immunoreagents capable of marking specific receptors (antigens) on cell surface membranes. The main requirements of the microspheres for the above applications are: insolubility in aqueous or organic media, absence of aggregation and of nonspecific interaction with cells and presence of suitable functional groups for covalent binding with antibodies. Hydrophobic polystyrene or poly(methyl methacrylate) latices do not meet these requirements. Copolymerization of hydrophilic monomers under suitable experimental conditions yielded microspheres with the required characteristics. Emulsion polymerization and ionizing radiation were found to constitute convenient techniques for the synthesis of hydrophilic and crosslinked (and therefore insoluble) functional microspheres ranging in diameter from 0.01 to 8 μm. By choosing suitable comonomers, it was possible to incorporate hydroxyl, carboxyl, amido, and dimethylamino functional groups into the particles. Copolymerization with isomeric vinylpyridines or dimethylamino methacrylate yielded weakly or strongly basic groups, respectively, capable of binding with acids. The experimental conditions suitable for obtaining desired particle sizes, in a relatively narrow distribution, were determined. It was found that the particle size depended to a large extent on the water solubility of the monomers, the presence or absence of stabilizer, the concentration of a surfactant, and the monomer concentration. The preferred technique to bind antibodies to the microsphere surface consisted of reacting amino groups with glutaraldehyde followed by the reaction with proteins. The use of polyglutaraldehyde instead of glutaraldehyde was also investigated. For this purpose the rate of polymerization of glutaraldehyde as a function of concentration and pH was first studied, followed by a study of the reactivity of polyglutaraldehyde micro-spheres with immunoglobulins. A recent new development of importance for cell separation is the synthesis of functional microspheres containing magnetic iron oxide. Preliminary investigations show that red blood cells and lymphocytes labeled with magnetic immunomicrospheres can be efficiently separated by means of permanent magnet. Separation of labeled from unlabeled human red blood cells was also achieved by means of a free-flow electrophoretic instrument.

ISSN:0022-233X    

DOI:10.1080/00222337908056677

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Colloidal dispersions of noble metals in synthetic polymers are prepared by reduction with alcohol. Reflux of a solution of rhodium(III) chloride and poly(vinyl alcohol) (PVA) in a methanol-water mixed solvent under argon or air for 4 hr gives a homogeneous solution of colloidal dispersion of rhodium (Rh-PVA-MeOH/H2O). The particle size of metallic rhodium is distributed n a narrow range of 30-70 Å, and the average diameter is 40 A. The formation of colloidal rhodium proceeds through three steps: coordination of poly(vinyl alcohol) to rhodium(III) ion, reduction with methanol to form small particles (8 Å in diameter), and growth of the small particle to large particle (40 Å in diameter). Polyvinylpyrrolidone (PVP) and poly(methyl vinyl ether) (PMVE) can be used in place of poly(vinyl alcohol) and result in colloidal dispersions, respectively, similar to Rh-PVA-MeOH/H2O. Colloidal dispersions in nonaqueous solvent can be prepared by using ethanol instead of methanol-water (Rh-PVP-EtOH) and by using methanol instead of methanol-water, with addition of small amount of methanol solution of sodium hydroxide (Rh-PVP-MeOH/NaOH). The average diameters of rhodium particles in Rh-PVP-EtOH and Rh-PVP-MeOH/NaOH are 22 and 9 Å, respectively. The colloidal dispersions of palladium, silver, osmium, iridium, platinum, and gold in aqueous or nonaqueous solvent are prepared by using polyvinylpyrrolidone. The colloidal dispersions are very stable even under air for 20 days. Those of rhodium, palladium, and platinum are effective catalysts for hydrogenation of olefins at 30°C under an atmospheric hydrogen pressure. The colloidal dispersion of palladium catalyzes highly selective hydrogenation of diene and dienoate to monoene and monoenoate, respectively.

ISSN:0022-233X    

DOI:10.1080/00222337908056678

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Carbon dioxide and epoxide copolymerize in the presence of some organometallic catalyst systems under moderate conditions to give aliphatic polycarbonates of high molecular weight. Some metalloporphyrins of aluminum and zinc were found to act as novel catalysts for the polymerization of epoxide and for the copolymerization of carbon dioxide and epoxide, though not alternating. The polymers are characterized by the narrow molecular weight distribution and the unusual stereoregularity. Starting from the copolymerization of carbon dioxide and trimethylsilyl glycidyl ether with diethylzinc-water catalyst system, a readily degradable polycarbonate having hydroxyl group was obtained.

ISSN:0022-233X    

DOI:10.1080/00222337908056679

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The spontaneous polymerization of 4-vinylpyridinium p-styrene-sulfonate or 4-vinylpyridinium chloride with sodium p-styrenesuifonate or of 4-vinylpyridinium 2-acrylamido-2-methylpro-panesulfonate with sodium p-styrenesuifonate produces an amphoteric, equimolar copolymer. An UV study on the interaction between 4-vinylpyridinium chloride and sodium p-styrenesulfonate indicates an absorption maximum corresponding to 1:1 charge transfer complex. From the observed results, a charge-transfer polymerization of 4-vinylpyridinium salts with electron-donating monomers is elucidated.

ISSN:0022-233X    

DOI:10.1080/00222337908056680

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The enantiomer selectivity in the propagation reaction of NCA was investigated by using suitable model reactions. Contrary to the assumption usually made, the enantiomer selectivity in the nucleophilic addition of chiral amines to NCA depended strongly on the structure of amine or NCA and the solvent. In the polymerization by an activated-NCA mechanism, the addition of activated NCA to NCA was found for the first time to be enantiomer-selective. In addition to this, the chiral penultimate unit was found to participate in the enantiomer selection. Structures of the transition states leading to the different types of enantiomer selection were proposed.

ISSN:0022-233X    

DOI:10.1080/00222337908056681

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Extensive studies on the mechanism of carbocationic polymerization initiation and particularly termination yielded information useful for the synthesis of a variety of new mono- and difunctional (telechelic) polymers. Unraveling aspects of initiation has opened new avenues toward the synthesis of novel cationic graft copolymers. Understanding details of termination has led among other products to cyclopentadiene-ended polyisobutylene and cyclopentadienylated rubbers. The latters crosslink by Diels-Alder addition and produce thermally reversible networks. Combination of controlled initiation and termination yielded telechelic products e. g., α, ω-diene-polyisobutylene. The use of Cl2/BCl3combinations led to the synthesis of α, ω-dichloropolyisobutylenes.

ISSN:0022-233X    

DOI:10.1080/00222337908056682

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0022-233X    

DOI:10.1080/00222337908056674

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor