Some new reactive polymers for the immobilization of enzymes.
From poly(vinyl alcohol) precursors, various reactive carriers for the immobilization of enzymes were synthesized. As insoluble starting polymers, the following products were used: poly(vinyl alcohol), gels crosslinked with terephthalaldehyde, hydrolyzed beads of crosslinked poly(vinyl acetate), poly(vinyl acetate-co- ethylene) tubes coated with poly(vinyl alcohol), and poly(vinyl alcohol)-containing synthetic pulp. Reactive groups introduced into these carriers or methods for their activation included the diazonium- and isothiocyanato group, and the glutardialdehyde-, BrCN, 2, 4, 6-trichloro-s-triazien, and p-benzoquinone methods. Furthermore, SH-specific reactive groups such as N-substituted maleimide groups or activated mixed disulfides with 2-thiopyridyl groups could be introduced into PVA-polymers. Enzymes like hydrolases (e.g. papain, trypsin, chymotrypsin, urease), oxidoreductases (e.g. glucose oxydase, catalase, glucose-6-phosphate dehydrogenase) as well as the example of transferase hexokinase coimmobilized with glucose-6-phosphate dehydrogenase, were immobilized by reactive poly(vinyl alcohol) carriers. The properties of the immobilized enzymes were investigated.
Coupling of Enzymes to Cellulose using Chloro-s-triazines
MANY methods are now available for coupling enzymes and other biologically active compounds to solid supports1–4. Most involve the preliminary preparation of a special support or of a special derivative of a general support such as cellulose; for example, the carboxymethyl or p-amino-benzyl ether derivative. We have therefore sought coupling reagents which allow a more direct approach and have developed the use of cyanuric chloride and dichloro-s-triazines. The latter can be prepared as stable compounds with solubilizing groups such as carboxy–methoxy or carboxy–methylamino, which make them very convenient reagents.
Hydrodynamically induced crystallization of polymers from solution
SummaryA detailed description of several phenomena observed during crystallization in a stirred solution of linear polyethylene is presented. It is found that simple shear flow is incapable of accelerating the formation of primary nuclei at elevated temperatures in 5% xylene solution of linear polyethylene (Marlex). The onset of fibrillar crystal formation is noted when the stirrer speed of the inner cylinder of aCouette instrument exceeds a minimum value which corresponds to the onset ofTaylor vortices. Closed loops of fibrillar crystals occurring periodically around the stirrer, revolve in orbits which coincide with the centers of theTaylor vortices. Turbulent flow seems to be most effective in inducing fibrillar crystallization and a maximum crystallization temperature of 112°C was achieved with the 5% xylene solution of Marlex. A mechanism is proposed for the formation of primary nuclei of bundlelike type which is based upon orientation and deformation of aggregates in regions of elongational flow between the vortices. Solutions of high molecular weight polyethylene (Mw=1.5×106) exhibit a pronouncedWeissenberg effect prior to the appearance of the first fibers. Normal stresses lower the rate of stirring inCouette flow at which vortices occur. This may account for the observed fibrillar crystallization of the high molecular weight polyethylene at stirrer speeds which in case ofNewtonian fluids give rise to laminar flow according to theTaylor criterion. Settlement of the fibrous network on the stirrer results from secondary flow.ZusammenfassungEs werden verschiedene, während der Kristallisation in einer gerührten Lösung von linearem Polyäthylen wahrgenommene Erscheinungen eingehend beschrieben. Es zeigt sich, daß eine einfache Strömung unter Scherung die Bildung von Primärkeimen bei gesteigerten Temperaturen in einer 5% igen Xylollösung von linearem Polyäthylen (Marlex) nicht zu beschleunigen vermag. Es wird festgestellt, daß die Bildung von Faserkristallen einsetzt, wenn die Rührgeschwindigkeit des Innenzylinders einesCouette-Gerätes einen der Entstehung derTaylorschen Wirbel entsprechenden Minimalwert übersteigt. Geschlossene Ringe von Faserkristallen, welche sich periodisch um den Rührer bilden, rotieren in Bahnen, welche durch die Mittelpunkte derTaylor-Wirbel gehen. Anscheinend ist eine turbulente Strömung das zweckmäßigste Mittel zum Hervorrufen einer Faserkristallisation; es wird hiermit in der 5% igen Xylollösung von Marlex eine maximale Kristallisationstemperatur von 112°C erreicht. Ferner wird ein Mechanismus zur Bildung von Primärkeimen vom garbenförmigen Typ vorgeschlagen auf Basis von Orientierung und Deformation von Aggregaten in den Geschwindigkeitsfeldern mit parallelen Gradienten zwischen den Wirbeln. Lösungen von Polyäthylen mit hohem Molekulargewicht (Mw=1,5×106) zeigen einen ausgeprägtenWeissenberg-Effekt, der dem Auftreten der ersten Fasern vorangeht. Normalspannungen erniedrigen den kritischen Wert der Rührgeschwindigkeit, bei der in einemCouette-Gerät eine Wirbelbildung auftritt. Dies dürfte eine Erklärung bieten für die beobachtete Faserkristallisation des hochmolekularen Polyäthylens bei Rührgeschwindigkeiten, welche im Falle derNewtonschen Flüssigkeiten zu einer demTaylorschen Kriterium entsprechenden Laminarströmung führen. Die Ablagerung des Fasernetzes auf dem Rührer ist auf Sekundärströmung zurückzuführen.