摘要:

AbstractAn earlier investigation of the effects of γ‐irradiation on aqueous solutions of sodium deoxyribonucleate showed that a plot of log [η] against logR(where [η] = intrinsic viscosity,R= radiation dosage) was linear at highRwith a negative slope of 1.85. According to the theory of degradation of macromolecules, this slope should equal ( −α), where α is defined by [η] =KMα(K= constant,M= molecular weight). Determination by light scattering measurements of theMvalues of γ‐degraded nucleate samples has now shown that [η] =KM1.0; the slope of the log [η] against logRplot was therefore approximately twice that to be expected for random degradation of asinglechain. Moreover,M−1was a linear function ofR2over the whole range fromR= 0 and this suggested that the initial nucleate had a random distribution of molecular weights. These observations consitute more positive evidence for the earlier proposal that the decrease in molecular weight of the double‐helical nucleate structure during γ‐irradiation was caused by two independent and approximately opposite breaks, one in each of the polynucleotide strands, and that the formation of such double breaks was proportional toR2. Heating ruptures these hydrogen bonds and, in accordance with the mechanism proposed, caused a relatively greater decrease inMthe larger the previous radiation dosage (R). Titration at 25°C showed that γ‐irradiation ruptured the hydrogen bonds, although half of them were still present in the samples of lowest [η]. This change has now been re‐investigated by titrations at −0.75°C. which allow the determination of thereversibledissociation curves of the double helices and of the denatured form. The low temperature titrations showed that, unlike the main chain breakdown, the rupture of hydrogen bonds was non‐random, those linking adenine and cytosine being broken more easily than

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112201

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractEs wurde die Synthese eines gegenüber Nickel selektiven und 1,2‐Dioximgruppe als aktive Gruppe enthältenden Ionenaustauschers untersucht. Dieses Problem wurde schon früher von Kljatschko studiert, der die Darstellung eines Kunstharzionenaus‐tauschers durch die Einführung von Dimethylglyoxim in den Sulfo‐Resorcin‐Kationen austauscher im Stadium der Kondensation in kurzgefasster Form beschrieben hat. Bei der Anwendung seiner Methode wurde festgestellt, dass sie nicht zu positiven Resultaten führt. Dimethylglyoxim wird dabei aus dem Harze teilweise extrahiert, grösstenteils aber durch die Einwirkung von Formaldehyd zersetzt, und die komplexbildenden Eigenschaften eingebüsst werden. Die Elution von Dimethylglyoxim aus dem Harze kann durch die Einführung der 1,2‐Dioximgruppe in das Molekül beseitigt werden, das mit Formaldehyd in Polykondensation treten kann z. B.p, p′‐Dioxybenzildioxim; es wird dabei jedoch der destruktive Einfluss von Formaldehyd auf die Dioximgruppe nicht beseitigt. Eine andere Möglichkeit bietet eine geeignete Behandlung des Phenol‐Formaldehydharzes. So eignet sich z.B. für eine Nickelaufnahme daso‐2,3‐Dioximinobutylderivat des Resorcin‐Formaldehyd‐Harzes. Es besitzt jedoch eine geringe Stabilität, besonders bei erhöhten pH‐Werten. Harze mit erhöhter Beständigkeit wurden aus Polystyrol‐Harz hergestellt durch die aufeinander folgenden: Propionylierung, Nitrosierung und Oximierung. Das Studium über die Struktur des polymären Materials zeigte, dass die Einführung der Propionylgruppep‐ständig verläuft, während in dem Styrolmonomeren die Propionylgruppe in die ω‐Stellung an der Seitenkette eintritt. Das Dioximderivat Polystyrols besitzt für Nickel eine Austauschkapazität von 2 meter/g und das Verfärben des Polymeren bei der Sorption entspricht dem Verfärben der niedermolekularen Dioxim–Nickel‐Komplexe. Die von linearen Polystyrol dargestellten Ionenaustauscher besassen nicht die erforderlichen mechanischen Eigenschaften; es wurden also Versuche ausgeführt mit einem Styrol‐Divinylbenzol Suspensionskopolymeren (0,3; 1.0% DVB). Es wurden dabei Bedingungen für das Erreichen des erforderten Umsetzungsgrades gefunden. Gegenwärtig wird der Einfluss von der Konzentration des primären Subst

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112202

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractButadiene has been polymerized by AlCl3and related materials at −78°C. The structure of the polymers produced has been studied by infrared analysis. The structure of the soluble polybutadiene was found to be independent of extent of conversion, concentration of catalyst solution, and length of reaction. An insoluble polymer also formed in the system and the amount of this depended on the extent of conversion, being greater at higher conversion whether this was achieved by higher catalyst concentration or longer time. Complexing the AlCl3with nitroethane or nitrobenzene changed the structure of the polymer slightly, while the use of diethyl ether as a complexer produced no changes. TiCl4, used as the initiator, produced polymers of slightly different structure from those formed with AlCl3, while AlBr3and BF3·Et2O yielded polymers like those from AlCl3. When the solvent used was varied, the polymer structure also varied. The observed variations were small in all ca

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112203

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112204

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe dissociation of arachin has been studied over a range of pH values, ionic strengths, temperatures, and protein concentrations and standard energy values have been calculated. The standard entropy changes and standard heat contents were found to be lower than would be expected and possible reasons for this are discussed. TheKcvalues varied on altering the protein concentration and are considered to be dependent on a function of the ratio of concentration to ionic strength.

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112205

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe complex dielectric constant of a pure molecular weight fraction of poly‐n‐hexyl methacrylate and of poly‐n‐octyl methacrylate was determined over a frequency range of 30 to 3 × 105cycles/sec. and a temperature range of −66 to 106°C. and −61 to 81°C., respectively. The data indicate the presence of two transition regions, with the transitions being further apart with increasing side chain length. Examination of the data showed that superposition was not possible using the usual superpo

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112206

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractOn going from alkaline to acid pH's, polyadenylic acid undergoes a marked structural change in the vicinity of pH 6. This change is reflected by a decrease in radius of gyration at low ionic strengths, some increase in molecular weight, and a marked drop in extinction coefficient at 257 mμ. The transition has been shown to result from titration of the adenine group

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112207

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe current disagreement as to whether the acid denaturation of DNA produces reversible or irreversible changes of macromolecular configuration can be resolved by paying proper attention to the temperature dependence of the denaturation process. Light scattering measurements have been made on a sample of sodium desoxyribosenucleate taken to pH 2.6 and reneutralized at 0 and 25°C. in 0.1MNaCl. Whereas the material, acid treated at 25°C., is irreversibly collapsed (radius of gyration = 1370 A., molecular weight unchanged), 0°C. titration leaves the size of the DNA molecule unchanged (ρ = 2800 A.). Viscosity measurements at 0°C. and pH 2.6 show that at this pH the DNA is nearly as fully extended as in neutral solution ([η] = 40 dl./g. compared to 63 dl./g. in neutral aqueous salt solution). However, collapse occurs at pH 2.6 between 0 and 25°C., and this thermal denaturation at pH 2.6 is irreversible. The light scattering properties of acid‐denatured DNA are interpreted in terms of a more heterogeneous distribution of macromolecular configurations than in the native

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112208

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractA study was made of the solubility of a high molecular weight polyvinyl chloride in a wide variety of solvents at room temperature. Many powerful solvents and solvent combinations for the polymer were demonstrated. A number of combination of N, N‐disubstituted amides with other classes of solvents, including the cyclic ethers, aliphatic ketones, alkyl‐substituted pyridines, and aromatic hydrocarbons, were found to have synergistic solvent action. The solvent power of many pure and mixed solvents appear to be qualitatively predictable from molecular structure in terms of: (a) the electron donor capacity of the solvent, (b) steric hindrance to approach of the electron donor center of the solvent to the polymer, and (c) effective solvent bulk for keeping the polymer chains well separated. The solubility parameter concept does not appear to be applicable for predicting solvent power in the systems stud

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112209

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe weight‐loss of a methyl‐phenyl silicone resin was determined over the temperature range from 135 to 240°C. and up to approximately 10% volatilization. Weight‐fraction volatilized varied linearly with the logarithm of time. The history of such logarithmic processes is reviewed briefly. The empirical rate‐equation is discussed in terms of the data. On the basis of a surface‐removal experiment, and on the basis of the chemistry of the degradation, a mechanism of Fickian diffusion is proposed, wherein the diffusion coefficient varies exponentially as the degree of crosslinking and shrinkage, while the concentration gradient of volatilizable molecules remain

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112210

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY