High Molecular Weight Products Research Articles

Electrical charge loss during pyrolysis of single coal particles

Westerholt and Ibbenbüren coal particles were devolatilized by means of a laser using an electrodynamic balance. The devolatilization occurred at ambient pressure and in a pure nitrogen atmosphere. The heating rate was moderate below 100 K/s. The particle temperature and the balancing voltage (to keep a single particle in the center of the balance) were measured continuously. Particle size and shape, and the aerodynamic drag force were measured before and after the reaction. Charge loss of the reacted particle was determined and it was found to be proportional to weight loss, indicating that at least a fraction of the evolved devolatilization products can carry charge which seems only to be possible for high molecular weight products such as a condensed phase.

MUC1 expression in hematopoietic tissues.

The MUC1 gene encodes the core protein of episialin, which is recognized by several antibodies. Reverse transcription-polymerase chain reaction (RT-PCR) detection of MUC1 transcripts has been proposed for the detection of micrometastases from breast cancers. MUC1 expression in hematopoietic tissues has been reported but not confirmed. Our preliminary RT-PCR studies confirmed MUC1 expression by MDA-231 breast cancer cells. Western blots of MDA-231 proteins stained with anti-MUC1 core gave one 68-kd (core protein) band, with an additional high molecular weight (HMW) band in blots stained with anti-epithelial membrane antigen (EMA). MUC1 expression was detectable by RT-PCR in 4 samples each of peripheral blood, bone marrow, and lymph node. MUC1 expression was detectable by Western blot analysis using anti-MUC1 core and anti-EMA in 2 peripheral blood samples and all bone marrow samples. Western blots from all lymph node samples stained positively with anti-EMA for the HMW product, but the 68-kd product was less prominent. Separated peripheral blood lymphocytes and granulocytes showed similar levels of MUC1 expression. RT-PCR studies demonstrated MUC1 expression in various hematopoietic cell lines. Western blots showed the 68-kd and HMW products in a granulopoietic line, with only the 68-kd product in 3 lymphoblastoid lines. MUC1 is expressed ubiquitously in hematopoietic tissues and is unsuitable for use as a marker for epithelial micrometastases.

Effect of Broensted and Lewis sites in ferrierites on skeletal isomerization of n-butenes

Skeletal isomerization of n-butenes to isobutene at 620 K was followed over NaH-ferrierites (FER) with different concentration of Broensted sites, prepared by NH 4 + vs. Na + ion exchange, and over H-FER containing both, the Broensted and Lewis sites formed by zeolite dehydroxylation at temperatures ranging from 670 to 990 K. Quantitative analysis of IR spectra of OH groups and adsorbed d 3-acetonitrile on ferrierite enabled determination of the concentration of Broensted and Lewis sites, and detected also those present in 8-ring ferrierite channels. With H-FER, the yield of isobutene is linearly proportional to the concentration of acidic OH groups. Formation of C 3 and C 5 olefins, C 2–C 5 paraffins and higher molecular weight products, resulting from di-, oligomerization of butenes followed by cracking/hydrogen transfer reactions, is enhanced by the presence of Lewis sites, if simultaneously present with the Broensted sites, that is in a substantial change of the selectivity of the reaction. On the other hand, both the conversion and yield of isobutene are nearly constant at decreasing concentrations of OH groups in NaH-FER, and only at low-concentration range of acidic hydroxyls a decrease in conversion was found. This indicates that the exchanged Na + ions are placed preferably in small ferrierite channels, as also evidenced by 23Na MAS NMR, which size is not large enough to accommodate isobutene molecules. Thus, besides the well-known positive effect of the inner geometry of ferrierite channels on isobutene selectivity, it has been shown that the reaction of n-butenes to isobutene is proportional to the number of hydroxyls located in large channels of ferrierite, and simultaneous presence of Lewis sites enhances di-,oligomerization/cracking reactions leading to higher yields of by-products.

Novel zirconocene catalysts for the production of high molecular weight LLDPE in high-temperature polymerization

Ethylene polymerization and ethylene/α-olefin copolymerization were conducted using diphenylmethylidene(cyclopentadienyl)(fluorenyl)zirconium dichloride (Ph 2 C(Cp)(Flu)ZrCl 2 ) as a catalyst activated with dimethylanilinium tetrakis(pentafluorophenyl)borate (Me 2 PhNH. B(C6F5) 4 )/triisobutylaluminium (i-Bu 3 Al) at high temperature and different ethylene pressure. This catalyst produces high molecular weight polyethylene with high activity. The molecular weight of the copolymers hardly decreases with increasing amount of comonomer in the feed. This is attributed to the control of β-H transfer from the propagating chain containing primary inserted comonomer. The occurrence of inner trisubstituted double bonds was confirmed. These bonds are probably formed by dehydrogenation reactions after β-H transfer from the propagating chain followed by ethylene insertion. Therefore, this reaction might play an important role in the production of high molecular weight ethylene/1-hexene copolymers at high temperature. At high ethylene pressure, isomerization reactions from inserted ethylene or primary inserted α-olefin as terminal units, which were observed under low ethylene pressure, can be controlled at low level.

Polymerization of lactides and lactones. II. Ring-opening polymerization of ?-caprolactone andDL-lactide by organoacid rare earth compounds

Ring-opening polymerization of lactone and lactide have been initiated with rare earth organoacid compounds, such as lanthanum acetate in bulk. The polymerization mechanism is in agreement with the “nonionic–coordination–insertion” mechanism, which involves the selective cleavage of the acyl–oxygen bond of the monomer. These organoacid rare earth initiators can give high yield of medium to high molecular weight products. An interesting aspect of this investigation is the good agreement between the performance of the initiator and the solubility of the initiator in the monomer. However, the relatively slow initiation step makes it difficult to control the molecular weight and results in a broad molecular weight distributions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1941–1948, 1999

Synthesis and properties of poly(lactic acid).

Poly(D,L lactic acid) was prepared by bulk polymerization of D,L lactide, both under atmospheric pressure and in vacuum. The obtained polymeric products were characterized in terms of molecular weight, Mw, melting point, calorimetric response and swelling behaviour. All products were amorphous. Their molecular weights were determined by viscosimetry and ranged from 2x10(3) to 9x10(4). Similarly, the melting points ranged from 90 to 210 degrees C. Swelling experiments, with specimens immersed in buffer solutions, showed that hydrolytic degradation started in a few days for the low Mw material, whereas for the higher molecular weight products it took much longer and probably followed a two-stage mechanism. This study suggests that the high molecular weight material could be an interesting carrier for the preparation of controlled release products, in cases where prolonged delivery is necessary.

Microbial desulfonation.

Organosulfonates are widespread compounds, be they natural products of low or high molecular weight, or xenobiotics. Many commonly found compounds are subject to desulfonation, even if it is not certain whether all the corresponding enzymes are widely expressed in nature. Sulfonates require transport systems to cross the cell membrane, but few physiological data and no biochemical data on this topic are available, though the sequences of some of the appropriate genes are known. Desulfonative enzymes in aerobic bacteria are generally regulated by induction, if the sulfonate is serving as a carbon and energy source, or by a global network for sulfur scavenging (sulfate-starvation-induced (SSI) stimulon) if the sulfonate is serving as a source of sulfur. It is unclear whether an SSI regulation is found in anaerobes. The anaerobic bacteria examined can express the degradative enzymes constitutively, if the sulfonate is being utilized as a carbon source, but enzyme induction has also been observed. At least three general mechanisms of desulfonation are recognisable or postulated in the aerobic catabolism of sulfonates: (1) activate the carbon neighboring the C-SO3- bond and release of sulfite assisted by a thiamine pyrophosphate cofactor; (2) destabilize the C-SO3- bond by addition of an oxygen atom to the same carbon, usually directly by oxygenation, and loss of the good leaving group, sulfite; (3) an unidentified, formally reductive reaction. Under SSIS control, different variants of mechanism (2) can be seen. Catabolism of sulfonates by anaerobes was discovered recently, and the degradation of taurine involves mechanism (1). When anaerobes assimilate sulfonate sulfur, there is one common, unknown mechanism to desulfonate the inert aromatic compounds and another to desulfonate inert aliphatic compounds; taurine seems to be desulfonated by mechanism (1).

Enantioselective Hydrogenation: V. Hydrogenation of Butane-2,3-dione and of 3-Hydroxybutan-2-one Catalysed by Cinchona-Modified Platinum

Pt/silica modified by cinchonidine and cinchonine is active for the enantioselective hydrogenation of butane-2,3-dione to butane-2,3-diol in dichloromethane at 268–298 K and 10 bar pressure. Reaction proceeds in three stages. In the first, about 85% of the butane-2,3-dione is converted to 3-hydroxybutan-2-one and 15% to three higher molecular weight products by hydrodimerisation. The initial enantiomeric excess in the hydroxybutanone is modest (20 to 40%(R) with cinchonidine as modifier, 10%(S) with cinchonine as modifier) and dependent on the amount of alkaloid used in catalyst preparation. In the second stage, 3-hydroxybutan-2-one is converted to butane-2,3-diol; a marked kinetic effect is observed whereby the minority enantiomer is converted preferentially to butanediol and the enantiomeric excess in the remaining hydroxybutanone increases dramatically to values in the range 62 to 89%(R) and to 30%(S). Under all conditions, the most abundant stereochemical form of the final product is meso-butane-2,3-dione. In the third stage the three dimers are slowly converted by hydrogenation, dissociation, and further hydrogenation to butane-2,3-diol. In the absence of alkaloid, butane-2,3-dione hydrogenation to racemic products in dichloromethane solution proceeds in two distinct stages with no dimer formation. Butane-2,3-dione hydrogenation has also been studied over Pt/silica modified anaerobically by exposure to cinchonidine in ethanol under propyne at 2 bar. This catalyst is remarkably active for the conversion of diketone to diol in ethanol at 293 K and 10 bar and kinetic selection in the second stage of reaction is again observed. The hydrogenation of racemic 3-hydroxybutan-2-one in dichloromethane over cinchonine-modified Pt/silica at 273 K and 10 to 40 bar pressure also showed kinetic selection, an enantiomeric excess of up to 70%(S) appearing in the reactant as it was consumed. Mechanisms which account for these hydrogenations and dimerisations and for the enantioselectivities observed and their variation are presented. This diketone hydrogenation provides an example of consecutive thermodynamic and kinetic control of enantioselectivity in a multistage catalytic reaction.

Halofluorination of 1,2-difluoro-1,2-di( p-tolyl)ethene, 1,2,3,4-tetrafluoro-1,4-di( p-tolyl) butadiene and its nonfluorinated parent compounds

The reactions of ( E)-1,2-difluoro-1,2-di ( p-tolyl) ethene ( 1) with N-bromo- or N-chlorosuccinimide gave mainly the expected halofluorination products 1-bromo-1,2-di( p-tolyl)-1,2,2-trifluoroethane ( 2) or 1-chloro-1,2-di( p-tolyl)-1,2,2-trifluoroethane ( 4), respectively. As a side reaction halogenation of the double bond has been obtained. With ( E,E)-1,4-di( p-tolyl)-1,2,3,4-tetrafluorobuta-1,3-diene ( 6) under the same conditions the products of 1,2- and 1,4-addition or its consecutive hydrolysis products were isolated. ( E)-Stilbene ( 19) on bromofluorination gave solely erythro-1-bromo-2-fluoro-1,2-diphenylethane ( 20), while with 1,4-diphenylbuta-1,3-diene ( 17) mainly higher molecular weight products were formed.

Polymers from pine gum components: Radical and coordination homo and copolymerization of pinenes

AbstractThe present work is aimed at studying the reactivity of α‐ and β‐pinenes in radical polymerization. The pinene homopolymers obtained were oligomers, showing both isomers similar reactivities. In order to achieve products of higher molecular weight, the radical copolymerization of α‐ and β‐pinene with methyl methacrylate and styrene was performed, giving rise to polymers with M̄w varying from 11 500 to 53 000. In radical copolymerization α‐pinene showed to be more reactive than β‐pinene. All the radical reactions performed were carried out with a Ziegler‐Natta catalyst, TiCl4/Et3Al, and with Et3Al. Under the conditions tested, β‐pinene did not undergo any polymerization reaction and the cocatalyst showed a pronounced catalytic effect. The coordination polymers obtained at 5 h had chain lenghts of the same order of magnitude of the corresponding radical copolymers obtained at 50 h, although for much lower overall conversion.

Fixed-bed dialysis culture of a transfectoma cell line producing chimeric Fab-fragments with “nutrient-split”-feeding strategy

The very shear sensitive transfectoma cell line, FAB 10, producing a chimeric Fab-antibody fragment specific for the human carcinoembryonic antigen (CEA), was cultivated in fixed bed reactors where the cells were immobilized in macroporous carriers. As the cell line had a very low productivity, cultures with “process integrated product enrichment” were performed in a membrane dialysis bioreactor with integrated fixed bed, where low molecular weight metabolites are removed over the membrane and high molecular weight products are enriched. In a new “nutrient-split” feeding strategy for dialysis cultures concentrated medium was supplied directly to the fixed bed unit, whereas a buffer solution was used as dialysis fluid. With the dialysis technique up to 5800 μg Fab l−1 could be obtained, more than 10 times higher compared to fixed bed cultures without dialysis or batch cultures with suspended cells. The “nutrient-split”-feeding strategy reduced the amount of medium required per mg of antibody significantly. © Rapid Science Ltd. 1998

Complex Organic Matter Present in Soil Structure and Origin

Organic matter, particularly humic substances and lipids, play an important role in soil processes (Stevenson, 1982). Previous studies have shown that lipid fraction from soil contains complex, macromolecular lipids which resemble a protokerogen (Ambles et al., 1991). The reversible incorporation of organic molecules in macromolecular lipids by ester groups was clearly demonstrated (Amblbs et al., 1994). Main of our results suggest that such a tranfer may also occur in humic substances. Moreover, these biomacromolecules can partly escape biodegradation and fossilizate after deposition in aquatic or hydromorphous environments. As a matter of fact, a close relationship could be established with sedimentary organic matter. Despite their geochemical importance, the structure of soil macromolecules remains largely unknown due to their heterogeneity and extreme complexity which render structural information often difficult and controversial. Different analytical techniques must be complementarily used to avoid misinterpretations in structural determination. In this work, the structure of macromolecular lipids, humic acids and insoluble humin present in an acidic anmoor soil sample (dystric histosol) from Plateau de Millevaches (France), where organic matter is accumulating, was studied using selective chemical degradations, pyrolysis and a new preparative TMAH thermochemolysis technique. The original soil sample contained 56% of total organic matter (TOM), based on oven-dried soil. Lipids contributed to 5% of TOM of the samples, fulvic acids to 21% and humic acids to 17%. The most important organic fraction was humin corresponding to 57% of TOM. Complex macromolecular lipids corresponded to 12% of lipids (0.6% of TOM). Hydrolysis of humin and humic acids. Stepwise hydrolysis was applied using a toluene solution of 18-Crown-6/KOH complex. A large part (87%) of the initially insoluble humin became soluble after a first series of hydrolyses. The soluble high molecularweight products thus obtained were still reactive when submitted again to the same conditions (2nd series of hydrolyses). Humic acids showed a lower reactivity. Linear dicarboxylic acids were produced in significant amounts from humin, they were short (mainly C9) in the first series and long even C16-C28 members of plant origin in the second one. Linear C12-C32 monocarboxylic acids and alkanols were freed from humin and humic acids. The short linear fatty acids and alkanols accompanied with isoand anteiso-C15 and C17 members denote a bacterial input while long even components, as well as various aromatic acids, originate from plant. Alkanols appeared as important hydrolysis products from both samples, mainly freed during the first series of experiments in the case of humin. They are C12-C30 n-alkanols with dominant C16, ClS, C20, C22, C24 and C26 members giving evidence for an important bacterial input. The identification of the iso C15 member confirms such a contribution. However, the source of the dominant n-C22 alkanol observed in humin and humic acids is not well explained. The results indicate that esterified aliphatic dicarboxylic acids are implicated in the reticulation of macromolecular chains corresponding to the matrix of humin. The matrix of humin and humic acids is substituted by alkyl chains which correspond to esterified fatty acids and alcohols, and by aromatic acids. These moieties are acting as monosubstituents. It is interesting to note that this model presents a high resemblance with the kerogen of many immature sediments. Thermochemolysis of humin and humic acids. Humic acids and humin were also investigated in their ester and ether groups using a new preparative TMAH thermochemolysis technique which allows the treatment of high quantity of product (~2g). Preparative TMAH thermochemolysis of humin and humic acids yields various hydrocarbons (alkene/ alkane doublets, sterenes, hopenes and hopanes), methyl esters of linear and branched fatty acids, linear dicarboxylic acids, oJ-methoxy fatty acids and 1-methoxyalkanes. In both samples, hydrocarbon distributions are dominated by classical pyrolytic series of Cls to C37 n-alk-l-ene/n-alkane doublets. Various steroids and triterpenoids, C27, C29 A-2 sterenes, C29 stera-

Structure of humin and humic acid from an acid soil as revealed by phase transfer catalyzed hydrolysis

A multistep alkaline hydrolysis under phase transfer catalysis conditions (PTC) was carried out on humic acid and humin fractions from an acid soil sample (anmoor soil) from the Plateau de Millevaches (France). A large part (87%) of the initially insoluble humin became soluble after a first series of hydrolysis. The main fraction obtained, soluble high molecular-weight products, was still reactive when submitted again to a second series of hydrolysis. Humic acid showed a lower reactivity. Linear dicarboxylic acids were produced in significant amounts from humin, they were short-chained (mainly C 9) in the first series and long-chained (C 16–C 28) with an even carbon number preference indicating a plant origin in the second series. Linear C 12–C 32 monocarboxylic acids and alkanols were freed from humin and humic acids. The short linear fatty acids and alkanols, accompanied with iso- and anteiso-C 15 and C 17 members, denote a bacterial input while long even components, as well as various aromatic acids, originate from plants. The results indicate that ester groups are involved in the cross-linking of macromolecular chains forming the matrix of humin. Aliphatic dicarboxylic acids act as bridges between alkyl chains in the matrix, while fatty acids, alcohols and aromatic acids correspond mainly to monosubstituents of the matrix (bound by ester groups). It is interesting to note that this model resembles the kerogen of many immature sediments.

Synthesis and properties of biodegradable copolymers based on polyether oligomers and fatty diacids

Polyether oligomers (Mn = 200–2000) were respectively esterified by succinic anhydride and fatty sebacoyl chloride to synthesize corresponding intermediate diacids, and experimental results of melt polycondensations based on these two kinds of intermediates were compared. The reasons for affecting higher molecular weight products to be achieved in polymerization with prepolymers based on succinic anhydride esterification were theoretically analyzed. Light scattering measurements showed that copolyanhydrides with higher molecular weights exceeding 8 × 104 (weight-average) were synthesized from the intermediate diacids prepared by a new method using fatty diacid chlorides to undergo esterification with polyether. Synthesized intermediates were characterized by 1H-NMR and infrared spectroscopy. Intrinsic viscosity of the polymers were measured to display the advancement of polymerization. The properties of polymers were investigated by X-ray diffraction and differential scanning calorimetry analysis as well. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1891–1898, 1997

Aromatic Polymers: Synthesis via Nickel Catalyzed Coupling of Aryl Chlorides

A new method for the formation of high molecular weight aromatic polymers via the nickel coupling of aromatic dichlorides will be described. The novel polymerization is performed in a dry aprotic solvent (e.g., in DMAC) using catalytic amounts of zero-valent nickel, triphenylphosphine or bipyridyl ligands, and excess zinc metal. The reaction must be performed under an inert atmosphere and in the absence of water. In order to obtain high polymer, one must use low amounts of nickel, high triphenylphosphine/nickel ratios, excess zinc metal and moderate temperatures (70°C). Variables such as the choice of ligand or co-ligand, salt addition, ligand and zinc concentrations, allow for optimization of the reaction efficiency. Critical features of the polymerization mechanism will also be reviewed. The method is general and allows for the preparation of novel monomers and an almost infinite variety of polymers. The two prerequisites for a successful preparation of high molecular weight product are solubility of the monomer, and more particularly of the obtained polymer, in the reaction medium; and the necessity that any functional group(s) present in the monomer(s) (and in the resulting polymer) be inert toward zinc/nickel system. Materials that were prepared via the novel method include polyarylether-sulfones, polyaryletherketones, polyphenylenes and polyamides. The approach is particularly suited for the synthesis of biphenylene based resins, e.g., polybiphenylene ethersulfone, because coupling of a chlorophenyl moiety creates a biphenyl unit. The latter display a number of highly attractive characteristics, such as high glass transition temperatures, low moisture absorption and extremely high impact strengths and toughness. An intriguing feature of the nickel coupling polymerizations and copolymerizations is encountered in instances that involve aryl chloro dichlorides possessing dissimilar chloro moieties. A number of sequence distributions are then possible in the resulting polymer. In some instances, different microstructures were indeed obtained under different experimental conditions when such “asymmetric” dichlorides were used.

Benzyl ether polymers: Crystallinity and pendant adamantyl effects

A series of benzyl ether polymers with and without pendant adamantyl groups has been synthesized. A-B homopolymers with dibenzylether and thioether connecting units were made by phase transfer reaction of 2-(4-bromomethylphenyl)-6-bromomethylbenzoxazole with KOH or Na 2 S. The ether-linked material was soluble only in conc. H 2 SO 4 while the thioether polymer was only soluble in a mixture of trifluoroethanol and chloroform. The parent AA-BB polyether from resorcinol and α,α'-dichloro-p -xylene (or the dibromo analog) was obtained as a very high molecular weight product which showed multiple crystalline forms depending on sample history. Solid-state 13 C-NMR spectroscopy and x-ray diffraction patterns were obtained on two samples [each with a single (different) type of crystalline domain], a high molecular weight sample displaying both types, and on amorphous material. Incorporation of pendent adamantyl groups was also examined because of their ability to enormously modify polymer properties.

A novel fabrication technique and new conjugated polymers for multilayer polymer light-emitting diodes

We report a novel fabrication technique for multilayer light-emitting diodes composed of new polyoxadiazole, POD, conjugated polymers for the first time. The fabrication technique called vapor deposition polymerization is described. Chemical modification of monomers brought about the enhancement of reactivity and the production of high molecular weight of POD. Emission color with photoexcitation was controllable from violet-blue to green by varying the chemical structures of PODs. It was found that PODs could be employed as either electroluminescent or carrier-injecting layers by the optimization of the device structure. Two types of bilayer devices, which are constructed with POD/tris (8-quinolinoato) aluminum, Alq3, and with two POD layers with different chemical structures, were investigated. Carrier injection begins in the POD/Alq3 bilayer device near 7 V, and the device emitted green light from Alq3. The maximum luminance of the POD/Alq3 device reached 3500 cd/m2. The POD/POD bilayer device emitted blue light with maximum luminance of 21 cd/m2. Electroluminescence spectra of the devices coincided with photoluminescence spectra of each emitting material used. © 1997 John Wiley & Sons, Ltd.

Thermal Treatment of 1,2,3,4-Tetrachlorodibenzo-p-dioxin by Reaction with Ca-Based Sorbents at 23−300 °C

The fate of combustion-generated polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) captured in sorbent-based, air pollution control devices remains uncertain. This process was simulated by passing vapor-phase 1,2,3,4-tetrachlorinated dibenzo-p-dioxin (TCDD) to a fixed-bed reactor laden with, typically, 1 g of calcium (Ca)-based sorbent. The sorbent bed, reactor rinsate, evaporation chamber, and gas impingers were analyzed separately to balance and account for the TCDD input. Tests at 160−300 °C demonstrated 50 to 100% conversion of TCDD to higher molecular weight, chlorinated products with both aromatic and aliphatic components. The unlikeliness of conventional semivolatile GC/MS analyses to detect these higher molecular weight products may offer an alternative explanation for research studies citing destruction or volatilization of chlorinated organics in the presence of Ca-based sorbents. The applicability of this reaction to other halogenated organics, such as polychlo...

Influence of medium composition on the growth and antigen expression of Helicobacter pylori.

An evaluation of the ability of various solid and liquid media to support both growth and antigen expression, particularly lipopolysaccharide (LPS) expression, by Helicobacter pylori culture collection strains and clinical isolates was performed. Liquid-based basal media (brain heart infusion, Brucella broth, Mueller-Hinton broth and tryptone soya broth) supported the growth of strains, whereas solid basal media of the same formulation did not support growth. Optimal growth of all strains was obtained on solid and in liquid media containing blood. Supplemented solid media containing supplements other than blood supported growth but only to a small extent. In liquid media excluding blood, serum supplements enhanced growth and horse serum was found to be superior to fetal calf serum. In general, beta-cyclodextrin did not increase growth. Mueller-Hinton broth or tryptone soya broth containing horse serum and a nitrogen source such as yeast extract or proteose peptone no. 3 were found to give optimal growth of H. pylori in a blood-free environment. Strains after cultivation in liquid media, irrespective of composition, maintained production of high-molecular weight (mol. wt) LPS with an O side chain independent of medium composition, whereas subculturing on solid media resulted in production of low-mol. wt LPS. Expression of proteins differed in liquid and on solid media, particularly proteins of 57 and 60 kDa, but qualitatively no differences were observed upon supplementation of basal media.

4-Vinylazobenzene: Polymerizability and Photochromic Properties of Its Polymers

The polymerizability of 4-vinylazobenzene; (VAB), a vinyl monomer containing an azobenzene chromophore directly attached to the polymerizable double bond, was investigated in the presence of radical, anionic, cationic, and Ziegler−Natta type catalysts. The homo- and copolymerization of VAB with (−)-menthyl methacrylate, carried out in the presence of AIBN as a radical initiator, afforded a fairly high yield of photochromic polymeric materials. On the contrary, no high molecular weight product was formed in the presence of cationic, anionic, and anionic coordinate catalysts, whereas polymeric products were obtained by anionic copolymerization of VAB with styrene. Determination of 13C relaxation times allowed us to evaluate the poly(VAB) molecular mobility, also, in comparison, that of 4-isopropylazobenzene, a low molecular weight model compound, and of other polymeric systems containing azobenzene chromophores spaced from the main chain. Thermally and photoinduced trans → cis and cis → trans isomerization ...