bluuebunny/crossref_metadata_2025_split huggingface dataset:
Classification of proteins according to conformation
Authors: Jirgensons B. 
Published: April 2003

AbstractOn the basis of optical rotatory dispersion data and other evidence, it was attempted to classify the proteins according to the conformation of their polypeptide chains. Three large groups of globular proteins emerge: 1. proteins with a high α‐helix content, 2. proteins with a low α‐helix content, and 3. the nonhelical globular proteins. Recent optical rotatory dispersion data have revealed that the nonhelical proteins can be subdivided into three subgroups: (a) proteins with an unknown order of type I (chymotrypsinogen, elastase, the luteinizing hormone, soyabean trypsin inhibitor, etc.), (b) proteins with an unknown non‐helical order of type II (serum γ‐globulin, the BENCE JONES proteins), and (c) disordered proteins (phosvitin, histones in aqueous solutions).New results on the following proteins are reported: adenosine deaminase, arginase, bacterial α‐amylase, collagenase, conalbumin, glucose‐6‐phosphate dehydrogenase, glyoxalase, 20‐β‐hydroxysteroid dehydrogenase, isocitric dehydrogenase, nucleoside phosphorylase, ovalbumin, peroxidase, α‐phosphorylase, phosphotransacetylase, phosphoglycerate mutase, transferrin, triose phosphate isomerase, and xanthine oxidase. The MOFFITT constants (b0) were determined, and the far ultraviolet COTTON effects were studied.Since the rotatory power of completely disordered proteins at the wave length of 198 mμ is now known, the α‐helix content of the proteins exhibiting the positive maximum in the curves at 198 mμ can be calculated from the amplitude of the maximum using the poly‐α‐L‐glutamic acid as standard.
Reaktionsfähige hochpolymere auf polystyrolbasis als träger von proteinen und enzymen
Authors: Manecke Von Georg , Föurster Hans‐Joachim 
Published: April 2003

AbstractDurch FRIEDEL‐CRAFTS‐Reaktion von 4‐Fluorbenzolsulfonsäurechlorid mit Polystyrol, anschließende Sulfonierung und Nitrierung wurden reaktionsfähige, hydrophile, unlösliche Polymere mit Nitrofluorbenzolsulfonylgruppen hergestellt.Die Copolymerisation von 4‐ bzw. 3‐Fluorstyrol mit Methacrylsäure und Divinylbenzol und nachträgliche Nitrierung ergaben hydrophile, unlösliche Copolymerisate mit Dinitrofluorphenylgruppen.Die chemische Reaktionsfähigkeit dieser Hochpolymeren, insbesondere ihr Proteinbindungsvermögen, wurden untersucht.Die Umsetzung der reaktionsfähigen Polymeren mit Diastase und Papain ergab Enzymharze, deren Eigenschaften untersucht wurden.
Graft efficiency
Authors: Smets G. , Dysseleer E. 
Published: April 2003

AbstractPolystyrenes carrying tert‐butyl peracrylic side groups have been synthesized by copolymerization of styrene with acrylyl chloride, partial esterification of the acid chloride units with tert‐butyl hydroperoxide, and, finally, methylation of the remaining free carboxylic groups. The weight percent of perester units varied from 0.9 to 3.4, that of methyl acrylate between 14 and 18%. These copolymers were used at 75 °C. in benzene solution for initiating the polymerization of methyl methacrylate; this second step polymerization obeys the square‐root law with respect to the initiator concentration, and is proportional to the monomer concentration. The graft efficiency, i.e. the ratio of the amount methyl methacrylate bonded as grafts to that of homopolymer, has been determined by carrying out fractionation of the several reaction products, using the precipitation method with chloroform as solvent and methanol as precipitant. The graft efficiency decreases from 1.52 to 0.77 when the monomer concentration increases from 1.91 to 7.54 mole· 1−1; it is however unsensitive to the macroinitiator concentration, unsensitive to the bulk viscosity of the reaction medium as well as to the presence of non‐solvent (methanol) in this medium.The perester‐content of the macroinitiator exerces a slight influence, the efficiency being higher when this content increases.The temperature affects strongly the efficiency ratio; this ratio increases from 0.53 to 1.11 when the temperature rises from 55 ° to 75 °C.; this effect stresses the strong influence of the nature of the radical with respect to their ability of monomer addition.
Neuere ergebnisse auf dem gebiet der cycloaliphatischen epoxydharze. 13. mitt.: Über die chemie der epoxydharze (1)
Authors: Batzer Von H. , Porret D. , Lohse F. 
Published: April 2003

AbstractEs werden Synthesen aliphatisch‐cycloaliphatischer Epoxydverbindungen beschrieben. Im ausgehärteten Zustand liefern sie Endprodukte mit hervorragenden mechanischen Eigenschaften. Ferner wird eine einfache Prüfmethode zur Erfassung der Rißanfälligkeit beim Eingießen von Metallteilen in kleinen Prüfkörpern angegeben und das Verhalten verschiedener Epoxydharze in diesem Test und ihre physikalischen Eigenschaften dargestelt. Der Härtungsmechanismus mit Carbonsäureanhydriden wird diskutiert.
Über die synthese unverzweigter polysaccharide
Authors: Husemann Von E. , Müller G. J. M. 
Published: April 2003

Abstract2,3,6‐Glucosetricarbanilat — aus Cellulosetricarbanilat durch Alkoholyse in 1‐Hydroxy‐2‐methoxy‐äthan in Gegenwart von p‐Toluolsulfosäure hergestellt — wurde in Chloroform/Dimethylsulfoxid durch Phosphorpentoxid kondensiert. Streulichtmessungen der Polykondensate ergaben Polymerisationsgrade bis 640. Zum Unterschied von Cellulose‐ und Amylosetricarbanilaten wurde keine eindeutige Beziehung zwischen STAUDINGER‐Indices und Molekulargewichten gefunden. Die Streulichtintensität ergab keine Winkelabhängigkeit. Die Produkte müssen daher verzweigt sein. Die Seitenketten sind an die Carbanilatgruppen gebunden, denn nach alkalischer Verseifung lagen die Polymerisationsgrade bei ca. 60. Aus Abbauversuchen mit α‐Amylase und Cellulase, Drehwerten in Tetraäthylammoniumhydroxid und vergleichenden Viskositätsmessungen an den Polyglucosanen und verschiendenen Cellodextrinen geht hervor, daß nur 1,4‐β‐glucosidische Bindungen in den synthetischen Polysacchariden vorliegen und daß die Produkte unverzweigt sind.
Homogeneous hydrolysis of esters with polymer sulfonic acids
Authors: Sakurada Ichiro , Sakaguchi Yasuyoshi , Ono Tomoyoshi , Ueda Toshio 
Published: April 2003

AbstractStudies on homogeneous hydrolysis were carried out of low molecular esters with polymeric sulfonic acids such as polyvinylsulfonic acid, copolymers of vinyl sulfonic acid and styrene, sulfonated polystyrenes, etc.In an aqueous solution of polymeric sulfonic acid, hydrogen ions, which contribute to the hydrolysis, are found only in the neighborhood of polymer molecule, and in dilute solution there is a region where no hydrogen ion being able to contribute to the hydrolysis exists; as a result, the hydrolysis takes place only in the neighborhood of polymer molecule. When longer alkyl ester such as butyl acetate is hydrolysed with partially sulfonated polystyrenes, the ester molecules are bound by hydrophobic interaction between a benzene ring and the alkyl group to result in a higher concentration of ester in the neighborhood of polymer molecule. In such a case, the rate of hydrolysis by a polymeric sulfonic acid is for example more than ten times greater than that of hydrolysis with hydrochloric acid. When no concentration of ester around polymer catalyst occurs, there is apparently no difference between the rates of hydrolysis by polymer catalyst and hydrochloric acid.It was further shown that esters which contain an amino group are hydrolysed with polystyrenesulfonic acid with a much higher rate than with hydrochloric acid due to its electrostatic interaction with the polymeric sulfonic acid.
Das durch das enzym amylomaltase eingestellte gleichgewicht oligomerer amylosen
Authors: Schulz Von G. V. , Häselbarth V. , Keller H. E. , Schwinn H. A. 
Published: April 2003

AbstractIn der Reihe Glucose G, Maltose G2, Maltotriose G3 usw. stellt Amylomaltase die Gleichgewichte: 2 G2 = G3 + G (K1), G3 + G2 = G4 + G (K2) usw. ein. Die Gleichgewichtsgemische werden chromatographisch analysiert und daraus die Gleichgewichtskonstanten K1, K2 usw. berechnet. Diese steigen vom Wert K1 = 0,9 ab bis zu einem Grenzwert von etwa 1,05 asymptotisch an. Enthalpie, Entropie und freie Enthalpie liegen, außer für den ersten Reaktionsschritt (K1), wie zu erwarten nahe bei 0. Das aus Escherichia coli (Stamm ML aus dem Institut Pasteur) isolierte Enzym Amylomaltase hat ein Molekulargewicht von etwa 130 000 und eine darauf bezogen Wechselahle von etwa 11 000 Mol Maltose pro Min.
Zur kristallstruktur der polycarbonate aus 4,4′‐dihydroxydiphenyl‐2,2‐propan, 4,4′‐dihydroxydiphenylsulfid und 4,4′‐dihydroxydiphenylmethan
Authors: Bonart Von R. 
Published: April 2003

AbstractEs wird gezeigt, daß das Polycarbonat aus 4,4′‐Dihydroxydiphenyl‐2,2‐propan monoklin in der Raumgruppe Cs2 mit je 4 Ketten in der Gitterzelle, das Polycarbonat aus 4,4′‐Dihydroxydiphenylsulfid und das aus 4,4′‐Dihydroxydiphenylmethan dagegen rhombisch in der Raumgrupe C2v9 mit je 2 Ketten in der Gitterzelle kristallisiert. Die Faseridentitätsperiode umfaßt in allen drei Substanzen jeweils zwei monomere Einheiten, so daß je 8 bzw. je 4 monomere Einheiten in der Gitterzelle liegen. Die Kristalldichten sind 1,315 g/ccm für das Polycarbonat aus 4,4′‐Dihydroxydiphenyl‐2,2‐propan, 1,50 g/ccm für das Polycarbonat aus 4,4′‐Dihydroxydiphenylsulfid und 1,303 g/ccm für das Polycarbonat aus 4,4′‐Dihydroxydiphenylmethan. Die Faseridentitätsperioden der drei betrachteten Polycarbonate sind um ca. 15% bis 20% gegenüber ihrer theoretischen Maximallänge bei voll ausgestreckten Ketten verkürzt. Dementsprechend beträgt der Kristall‐Elastizitätsmodul in Kettenrichtung ca. 450 bis 600 kp/mm2. Die betrachteten Kristallstrukturen enthalten keinerlei Gleitebenen, so daß die Kristallbereiche eine hohe Scherfestigkeit besitzen. Die geringe Kristallisationstendenz des Polycarbonates aus 4,4′‐Dihydroxydiphenyl‐2,2‐propan findet durch die Kristallstruktur eine plausible, zwanglose Erklärung.
On the thermoelastic inversion point of swollen rubber
Authors: Oplatka A. , Katchalsky A. 
Published: April 2003

AbstractA thermoelastic inversion point has long been known for dry rubber. We report inversion points for natural rubber swollen to different extents by n‐hexadecane. A theoretical analysis of the length at the inversion point as a function of the degree of swelling is presented and shown to be in good agreement with the experimental findings.
Halogénation et déhydrohalogénation des cis‐1,4 polyisoprènes et polyènes analogues
Authors: Pinazzi Chr. P. , Gueniffey H. 
Published: April 2003

AbstractLe présent travail porte sur les halogénations et les déhydrohalogénations des cis‐1,4 polyisoprènes et polybutadiènes. Il apporte une contribution à l'étude de la bromation des polyisoprènes et il décrit les conditions permettant la bromation des polybutadiènes; ces substances font l'object d'une étude particulière. La faible solubilité des dérivés polybromés (sur les doubles liaisons) ne s'explique pas par les réticulations, lesquelles sont sans doute peu nombreuses, mais plutôt par l'encombrement stérique des atomes de brome. La labilité de ces macromolécules bromées explique la décomposition notable qui se manifeste dans certains solvants aprotiques tels que le tétrahydrofuranne et la diméthylformamide, et cela même en l'absence de réactif de déhydrohalogénation.La déhydrohalogénation des macromolécules possédant deux bromes sur carbones vicinaux. et par motif, a permis de montrer la formation de moyennes séquences de doubles liaisons conjuguées sur des produits de masse moléculaire élevée. Il semble que les meilleurs résultats soient obtenus par des réactions lentes à la température ambiante.Enfin, l'étude de l'halogénation radicalaire en α des doubles liaisons fait ressortir la facilité avec laquelle ces polyènes halogénés donnent des réactions de déhydrohalogénation et aussi des réactions secondaires de réticulation.
Polymerization by crystallization of molten trioxane suspended in inert media, in presence of ethylenoxide
Authors: Baccaredda Mario , Butta Enzo , Morelli Fernando , Masetti Giorgio 
Published: April 2003

AbstractThe method of polymerization of trioxane solutions during crystallization by cooling is extended to molten trioxane in presence of ethylenoxide, suspended in mineral oil (thickened with polyisobutylene) and activated with small quantities of BF3·Et2O. Operating with quantities of catalyst in the order of 4.0/10−5 moles/mole of trioxane, copolymers with prevailing polyxymethylene structure are obtained, characterized by high molecular weight (ηinh = 1.5 in 0.5% solution in p‐chlorophenol at 60°C.) and good thermal stability (k220 = 0.03%/min.), with yields of 45 to 60%.
Polymerization of alkylene oxide by alumina
Authors: Matsui Y. , Yokoo M. , Tanabe H. , Saegusa T. , Furukawa J. 
Published: April 2003

AbstractAmorphous γ‐alumina of small particles size has been prepared by the hydrolysis of aluminum isopropoxide (AIP) powder with a gas mixture of steam and nitrogen and subsequent calcination of aluminum hydroxide at 600°C.; it has proved to be of quite high catalyst activity for the polymerization of ethylene oxide and propylene oxide. Several other alumina species have also been prepared by different procedures and examined for catalyst activity.The properties of these alumina species, such as surface area, acid strength, acidity, and crystal form were surveyed in relation to the catalyst activity. It has been assumed that the high catalytic activity of amorphous γ‐alumina prepared by the above specific procedure is due to the amorphous nature and to high acidity.
Asymmetric‐selection polymerization of propylene oxide by diethylzinc and D‐ or L‐glutamate system
Authors: Furukawa Junji , Saegusa Takeo , Yasui Seimei , Akutsu Seiichi 
Published: April 2003

AbstractAsymmetric polymerization of racemic mixture of d‐ and l‐propylene oxide (PO) was carried out by means of catalyst system of diethylzinc and glutamic acid ester. From the optical activity of the recovered monomer, the effect of unbalance between D‐ and L‐glutamates in the catalyst system upon the selectivity of asymmetric consumption of d‐ and l‐monomers was examined. It has been shown that the catalyst system having excess diethyl D‐glutamate (DG) over the L‐counterpart (LG) favours the polymerization of l(–)‐PO. A directly opposite phenomenon of asymmetric consumption was observed in the polymerization with catalyst system having excess LG. The unbalance degree of asymmetric consumption is almost linearly related to the unbalance between DG and LG in the catalyst system. The sign of optical rotation of produced polymer was opposite to that which is to be expected from the unbalance in monomer consumption. This peculiar phenomenon has been explained by the findings that partial inversion of the asymmetric carbon atom of PO monomer occurs in the course of propagation reaction, and that the extent of inversion of one monomer enantiomer is different from that of its antipode in the polymerization with asymmetric catalyst.
Über einige chemische reaktionen am polyacenaphthylen (Teil II)
Authors: Manecke Von G. , Bauerschmidt E. 
Published: April 2003

AbstractPolylithiumacenaphthylen wurde mit Aldehyden, Nitrilen, Schwefel, Phenylisocyanat und Dimethylformamid umgesetzt. Polyacenaphthylen konnte bromiert und hydroxynitriert werden. Die Darstellung einer Polyacenaphthylencarbonsäure gelang durch Oxydation des acetylierten Polyacenaphthylens mit Hypochlorit.
Die copolymerisation von formaldehyd mit cyclischen formalen
Authors: Hermann Von H. D. , Weissermel K. 
Published: April 2003

AbstractEs wird über die Darstellung von Copolymerisaten aus Formaldehyd und cyclischen Formalen in Gegenwart Kationisch wirksamer Katalysatoren berichtet. Der Einfluß von Monomerenzusammensetzung, Temperatur, Katalysatortyp und ‐konzentration auf den Copolymerisationsverlauf wird beschrieben. Im Verlauf der Polymerisation kann eine Transacetalisierung erfolgen, die zu einheitlich aufgebauten Copolymeren führt. Das Ausmaß der Transacetalisierung läßt sich durch Variation der Polymerisationsbedingungen beeinflussen.
Polymers containing pyromellitimide units
Authors: Imai Yoshio , Uno Keikichi , Iwakura Yoshio 
Published: April 2003

AbstractPolymers containing pyromellitimide units were prepared from pyromellitic dianhydride and dihydrazides. The polymer formation was carried out in two steps: (i) the ring‐opening polyaddition reaction of pyromellitic dianhydride with a dihydrazide in dimethylacetamide and (ii) the imidization reaction of the precursor. The polymers having inherent viscosity up to 0.5 was obtained readily. They were insoluble in all organic solvents and indicated some degree of crystallinity. The polymer having aromatic linkage showed good thermal stability up to 380°C. in air.
Polycondensation‐addition. II. Polyurethan‐ureas from ω‐isocyanatoalkyl chloroformates and diamines
Authors: Hayashi Katsumi , Iwakura Yoshio 
Published: April 2003

Abstract5‐Isocyanatopentyl chloroformate (I), 3‐isocyanatopropyl chloroformate (II), and 2‐isocyanatoethyl chloroformate (III) were prepared by treating corresponding amino alcohols with phosgene in dioxane. The preparations gave ω‐Chloralkylisocyanate und 2‐Oxazolidone. as by‐products. I, II, and III were subjected to polycondensationsaddition with various diamines to obtain high molecular weight, film forming polyuretharr‐ureas.
The effect of tacticity on polypropylene fractionation
Authors: Porter Roger S. , Cantow Manfred J. R. , Johnson Julian F. 
Published: April 2003

AbstractThe basis for gradient‐elution fractionation is a regular decrease in solubility with an increase in polymer molecular weight. tacticity, however, can be an overlapping effect in the solvent separation process. In this study, the effect of tacticity in the fractionation of polypropylene has been studied using representative “atactic” and “isotactic” polymers, defined by heptane solubility. Typical and published column techniques have been used. A high resolution proton magnetic resonance analysis of protons in the chain methylene region was used for evaluation of tactic placement. A new tacticity correlation was developed which is based on data obtained here and on PMR results on polypropylene reported by SATOH and KATO. This correlation has been compared to published spectra of STEHLING and of WOODBREY. Changes of tacticity with molecular weight are most prominently observed in the first gradient‐elution fractions from both “atactic” and “isotactic” polypropylenes. The implication of these results concerning apparent molecular weights and distributions is discussed.
Cationic copolymerization of 1,3‐dioxolane with styrene
Authors: Okada Masahiko , Yamashita Yuya , Ishii Yoshio 
Published: April 2003

AbstractCationic copolymerization of 1,3‐dioxolane with styrene was performed in toluene solution at 25°C. using boron fluoride etherate as catalyst. Determination of formaldehyde units in the copolymer showed that the two monomer units formed somewhat longer sequences in the copolymer chain than calculated on the assumption that these monomer units are statistically distributed in the copolymer chain according to their copolymerization parameters.
The helical conformation of poly(3‐methyl butene‐1)
Authors: Huguet M. G. 
Published: April 2003

AbstractThe crystal structure of poly(3‐methyl butene‐1) has been investigated by X‐ray methods. The unit cell is tetragonal with a = b = 34.32 Å., c = 6.84 Å., α = β = γ = 90°, and the space group was found to be I41 cd. The experimental density, 0.91 g./ccm., agrees well with the calculated value 0.92 g./ccm., on the assumption of 64 monomeric units. The monomeric units are arranged in 16 different helices, which are of the 41 type, and which pack together in groups of four around each four‐fold screw axis of the unit cell, leading to four four‐helixclusters. The crystal structure proposed for poly(3‐methyl butene‐1) can be described as a four four‐helical cluster which exhibits a high degree of “openness”. This „openness”︁ of the structure is a consequence of the way in which the four clusters of four helices each pack together. Each cluster, however, behaves by itself very much as a distinct unit. The high melting point observed is probably a consequence of the mode of packing of the helices within this unit cell.
Vinyl polymerization. 120. Mutual copolymerization of p‐substituted styrenes through radical mechanism
Authors: Imoto Minoru , Kinoshita Masayoshi , Nishigaki Masahiko 
Published: April 2003

AbstractThe radical mutual copolymerization of p‐substituted styrenes, such as p‐methoxy‐, p‐chloro‐, p‐bromo‐, p‐cyanostyrene, and styrene was carried out with one another at 30°C. in the dark. As initiator, azobisisobutyronitrile was used. The plots of the copolymerization rates against HAMMETT's σ values showed no linear relationships and the concave curves were obtained therefrom. The relative reactivities of p‐substituted styrenes with a definite p‐substituted polystyryl radical, which were shown by the reciprocal of monomer reactivity ratio r1, were plotted against σ values and concave curves were also obtained. The relative reactivities of p‐substituted polystyryl radicals with p‐substituted styrene were calculated from the ratios r2 and the propagation rate constants in homopolymerization. the plots of them against σ values gave straight lines with different ρ values, according to the polarity of substituents. These results suggest that polar structures in transition state affected markedly the copolymerization rates. The effect of substituents on resonance stabilization was also quantitatively estimated.
On structural characteristics of stereoregular cis‐polybutadienes
Authors: Poddubnyi I. Ja. , Grechanovskii V. A. , Ehrenburg E. G. 
Published: April 2003

AbstractThe study of molecular weight distribution and the degree of branching on cis‐poly‐butadienes obtained by using complex catalysts Til4 + (i C4H9)6Al (I) and (i C4H9)2AlCl + CoCl2 (II) has established that the structural characteristics of these polymers do not depend exclusively on the type of catalyst used.The polymers obtained in the presence of catalyst II having a narrow molecular weight distribution at the beginning of the polymerization process become highly polydisperse towards the end of the reaction. This result as well as the increase in chain branching of the type II polymers at high degrees of conversion suggest interchain reactions to occur readily in the course of polymerization.In the case of type I polymers a narrow molecular weight distribution is observed; the polymerization having a stationary character during all its stages at 25°C. At lower temperatures, however, this character is disturbed, the polymer molecular weight increasing with the increase in conversion degree. Type I polymers are practically linear upto 100% conversion.Thus, both branching and molecular weight distribution of these polymers depend on polymerization conditions, affecting them differently for the two catalysts used.
The conversion of metal catalysts into inhibitors of autoxidation
Authors: Betts A. T. , Uri N. 
Published: April 2003

AbstractIt is demonstrated that certain cobalt compounds which are autoxidation catalysts at low concentrations become inhibitors at higher concentrations. In all these cases inhibition implies a lengthening of the induction period, but only in a few systems (N‐alkylamide + cobaltous acetate) is the inhibitory effect observable beyond the induction period. In the case of hydrocarbons and cobalt(II) salicylaldimines the rate of oxygen uptake beyond the substantially increased induction period is not reduced even at the highest catalyst concentrations. A reaction mechanism and a kinetic scheme, consistent with the novel experimental observations, are proposed.