High molecular weight hydrolyzed polyacrylamides. III. Effect of temperature on chemical stability

1980 ◽  
Vol 25 (4) ◽  
pp. 627-633 ◽  
Author(s):  
G. Muller ◽  
J. C. Fenyo ◽  
E. Selegny
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Chemical Stability ◽  
Effect Of Temperature

scholarly journals A theory relating the action of salts on bacterial respiration to their influence on the solubility of proteins

1947 ◽  
Vol 134 (875) ◽  
pp. 181-201 ◽  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Dehydrogenase Activity ◽  
Halophilic Bacteria ◽  
Convincing Evidence ◽  
Effect Of Temperature ◽  
Bacterial Respiration ◽  
Concentrated Solutions ◽  
Salting Out ◽  
Intact Cells

Evidence has been presented indicating that the action of concentrated solutions of salts on bacterial respiration may be partly explained in terms of salting-out. It has been suggested that the material upon which this action is exerted is probably one of the proteins concerned in respiration, perhaps a dehydrogenating enzyme. This theory provides satisfactory explanations for: ( a ) the relation between salt con­centration and rate of respiration or dehydrogenase activity; ( b ) the effect of temperature on this relation; and ( c ) the effect of pH on this relation, if it is further supposed that only the zwitterionic fraction of the protein is involved. The relative actions of various salts are in fair agreement with this suggestion, but provide no very convincing evidence either for or against it. The chief point of difficulty lies in the range of concentration over which the action is manifest. With halophilic bacteria, the evidence is consonant with the above view if the protein involved is one of high molecular weight. With normal organisms the salt concentra­tions are much lower than those causing salting-out. There is a little evidence that in normal organisms the dehydrogenating enzymes are less sensitive to salts than the intact cells, which may be the source of the discrepancy. No reason for this can yet be suggested, but the property must be absent from the enzymes of halophilic organisms, and whatever it is, its absence must be the foundation of the halophilic character.

Stability of Butadiene

1944 ◽  
Vol 17 (2) ◽  
pp. 475-484
Author(s):  
Richard F. Robey ◽  
Herbert K. Wiese ◽  
Charles E. Morrell
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Active Oxygen ◽  
Effect Of Temperature ◽  
Appreciable Effect ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Thermally Activated ◽  
Steel Surfaces ◽  
Dimerization Reaction

Abstract 1. The most prominent polymerization of pure butadiene in the absence of peroxides is dimerization. This reaction is thermally activated, and does not appear to be catalyzed by peroxides or by steel surfaces. 2. Butadiene is also capable of independent polymerization to high-molecular-weight polymer, but in the absence of peroxides this reaction is insignificant compared to dimerization. The effect of temperature on the rates of each of these reactions has been determined. 3. In the presence of appreciable amounts of peroxides, polymerization to high-molecular-weight polymer becomes prominent, and is superimposed additively on the thermal dimerization reaction. 4. The addition of suitable antioxidant inhibits the formation of high-molecular-weight polymer, but has no appreciable effect on the rate of dimer formation. 5. The rate of high-molecular-weight polymerization is directly proportional to the square root of the concentration of peroxides (active oxygen). 6. Butadiene is readily peroxidized by air, but this peroxidation may be inhibited for a time by the presence of antioxidants. 7. The peroxides are not readily volatile, and tend to accumulate in the residue if the diene is evaporated or distilled away. Concentration beyond a certain point yields an unstable residue which may decompose with violence when heated. Precautions for distillation of such peroxidized material are given.

Chlorinated Rubber from Latex

1952 ◽  
Vol 25 (3) ◽  
pp. 609-620 ◽  
Author(s):  
G. J. van Amerongen
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Chemical Stability ◽  
Hypochlorous Acid ◽  
Mechanical Stability ◽  
Chlorine Content ◽  
Rubber Latex ◽  
Synthetic Rubber ◽  
Satisfactory Method ◽  
New Applications

Abstract This work was undertaken to find new ways for producing chlorinated rubber from rubber latex. Methods have been applied during which coagulation of the latex and hyprochlorination of the rubber are avoided. Passing gaseous chlorine through stabilized and strongly acidified Hevea latex proves to be a satisfactory method for the chlorination of rubber. To avoid coagulation of the latex, certain nonionogenic or cationogenic emulsifiers have to be added. A high acidity of latex prevents the formation of hypochlorous acid and improves the mechanical stability of the latex. A chlorinated rubber latex is produced, the chlorinated rubber of which contains virtually no oxygen and up to 61 per cent of chlorine. By subjecting this chlorinated rubber latex or the dry isolated chlorinated rubber to an aftertreatment, products of a satisfactory solubility and with a chlorine content up to 72 per cent have been obtained. Judging from the reactivity with aniline, maximum chemical stability is at 65 per cent chlorine content. As a similar chlorination technique is applicable to rubber hydrochloride and synthetic rubber latexes, it is seen that latexes in general are good starting materials for the production of chlorinated derivatives. Moreover, stable chlorinated rubber latexes are obtained which can be used as such, making new applications possible. Technical advantages of chlorinating rubber in latex above rubber in solution are the much higher rubber concentration which can be used, and the ease of cooling the less viscous latex during the reaction. For some applications it is advantageous that the original high molecular weight of the polymer can be conserved.

Microtubule motors and other maps

1990 ◽  
Vol 48 (3) ◽  
pp. 1-1
Author(s):  
Richard B. Vallee
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Cytoplasmic Dynein ◽  
Organelle Transport ◽  
Structural Components ◽  
Microtubule Associated Proteins ◽  
Microtubule Motors ◽  
Associated Proteins ◽  
The Subject ◽  
Intracellular Motility

Microtubules are involved in a number of forms of intracellular motility, including mitosis and bidirectional organelle transport. Purified microtubules from brain and other sources contain tubulin and a diversity of microtubule associated proteins (MAPs). Some of the high molecular weight MAPs - MAP 1A, 1B, 2A, and 2B - are long, fibrous molecules that serve as structural components of the cytamatrix. Three MAPs have recently been identified that show microtubule activated ATPase activity and produce force in association with microtubules. These proteins - kinesin, cytoplasmic dynein, and dynamin - are referred to as cytoplasmic motors. The latter two will be the subject of this talk.Cytoplasmic dynein was first identified as one of the high molecular weight brain MAPs, MAP 1C. It was determined to be structurally equivalent to ciliary and flagellar dynein, and to produce force toward the minus ends of microtubules, opposite to kinesin.

Sign in / Sign up

Export Citation Format

Share Document