Article MEHRKANAL - AUFNAHMESYSTEM FÜR BIOSIGNALE MIT BIS ZU 512 ANALOGEN EINGÄNGEN was published on January 1, 2003 in the journal Biomedical Engineering / Biomedizinische Technik (volume 48, issue s1).

In this paper the application of microspheres fabricated from biodegradable polyesters like poly(DL-lactic acid) and poly(DL-lactic-co-glycolic acid) as carrier materials for the enzymes urease and phytase is described. The microspheres were prepared by a recently developed water-in-oil-in-water emulsion technique. The mean diameter of the obtained ball-shaped particles was between 50 and 200 mum, depending on the reaction conditions. The entrapment of urease within poly(DL-lactic acid)-beads results in a water-insoluble biocatalyst of good operational stability. The kinetic data (Michaelis-Menten constant, activation energy) as well as the determined low effective diffusion coefficient indicate a considerable mass transfer limitation whereas partitioning effects could not be detected. Further, phospholipids being present in the reaction mixture lead to a decrease in activation energy and with this to a remarkable increase in the reaction rate. This was observed for immobilized phytase too. The use of poly(DL-lactic-co-glycolic-acid) instead of poly(DL-lactic acid) turned out to be not as advantageous for the entrapment of urease concerning its repeated application, however, in case of phytase immobilized by the same technique within the co-polymer catalysts with an efficiency of up to 40% could be produced. On the other hand their operational stability is not yet satisfactory. This contribution also contains first results regarding the entrapment of B-D-galactosidase within poly(DL-lactic acid) microspheres.

The limitation of mass transport by diffusion plays an important role in heterogeneous catalysis. For optimizing the preparation conditions of immobilized and thereby water-insoluble biocatalysts and in order to be able to characterize them by their kinetical behaviour the effective diffusion coefficient De of the substrate molecules within the carrier matrix must be known. In this paper a simplified evaluation method for the determination of De by effusion measurements is described.

AbstractVom 10. bis 12. März veranstaltete die GDCh‐Fachgruppe „Biochemie”︁ ihre 12. Vortragstagung an der Martin‐Luther‐Universität Halle‐Wittenberg. Die Veranstalter stellten zum Thema „Stabilität und Stabilisierung von Proteinstrukturen”︁ ein attraktives Programm zusammen.

Experiments have been performed so as to clear up the influence of various organic solvents on the catalytic properties of urease, N,N-dimethylformamidase and phospholipase A2. This has been done by incubating the enzymes in organic solvents for different lengths of time at different temperatures before measuring their catalytic activity. It is found that this heat treatment in some cases leads to an enhancement of the activity, and that the enzymes are not inactivated even at temperatures far above their optimum temperatures in water.

The fixation of proteins to water insoluble materials has become an important field in chemistry and related disciplines [1]. Preference is often given to inorganic carriers because of their resistance of bacterial degradation. Moreover, the investigation of the interaction between proteins and nonbiological surfaces is of great practical interest with respect to the increasing use of prosthetic materials in the body [2].

The activity of urease immobilized by adsorption on anodized sheet aluminium strongly depends on the method chosen for preparation of these carriers. If oxalic acid is applied as electrolyte, only the anodizing temperature significantly influences the activity of the preparations. In case of the well-known GS process, however, the activity is not only affected by the temperature, but also by other conditions of anodizing, for example the current density and the electrolyte concentration. For both methods the correlation between the topography of the carrier surfaces and the activity of enzyme immobilized to the surface is described.

Nachrichten aus Chemie, Technik und LaboratoriumVolume 27, Issue 12 p. 765-766 Tagungsbericht IUPAC-Kongreß: Chemical Education P. Grunwald, P. GrunwaldSearch for more papers by this authorG. Keller, G. KellerSearch for more papers by this author P. Grunwald, P. GrunwaldSearch for more papers by this authorG. Keller, G. KellerSearch for more papers by this author First published: Dezember 1979 https://doi.org/10.1002/nadc.19790271204AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume27, Issue12Dezember 1979Pages 765-766 RelatedInformation

The immobilisation of enzymes is a well-known technique (enzyme engineering) by which proteins are made water-insoluble. In several cases it was possible to obtain new fundamental knowledge in enzyme chemistry from studies on the reaction behaviour of immobilised enzymes (1). We have carried out investigations on urease covalently attached to carriers of the type Aln(OH)3n−1-OOC-C6H4-NH2 (2) by an azo linkage (3). Normally, the activity of enzymes is reduced by immobilisation procedures, but this disadvantage can be overlooked because of the possibility of reusing the enzyme. The residual activity, too, is a function of the number of attachment points between protein and carrier per unit area. For the carrier material applied by us, low ‘n’ values mean high p-aminobenzoicacid concentrations and the activity of enzyme preparations increases with increasing value of ‘n’. Though enzymes, that are bound more rigid to a solid support have smaller activities, they are, as our experiments show, of better durability, if used for continous urea hydrolysis during several weeks, even if the reaction is performed at higher temperatures.

In order to obtain informations about the reaction mechanism of enzyme-catalysed reaction, a simple kinetic method exists, that shall be demonstrated here with urease as an example, the reaction behaviour of which is not yet known. The procedure is based on the conversion of the substrate molecule S into a charged state (eq.1),whose reaction with active site of the enzyme is then investigated (eq.2). In the case in question we made use of the complex formation between urea and alkaline earth halides (MeX2).

In this paper, an adsorption procedure of urease to Al(OH)3 is described that leads to a water-insoluble catalyst for urea hydrolysis. Moreover, it can be shown by this example, that the quantitative interpretation of adsorption measurements provides an indirect method for obtaining information about the structure of the adsorbed enzyme. The results of the experiments reported here reveal that, within two concentration ranges, the adsorbed quantity of enzyme increases with different slopes. This kind of adsorption is explained by a model, the basis of which is the assumption of a structure for the enzyme molecule deviating from the spherical form. The measured activities of the assays, as a function of adsorbed enzyme, support the hypothesis propounded.