Dextran kinetics, effect

Blackburn AC, Doe WF, Buffinton GD (1998) Salicylate hydroxylation as an indicator of OH radical generation in dextran sulfate-induced colitis. Free Rad Biol Med 25 305-313 Bonifacic M, Stefanic I, Hug GL, Armstrong DA, Asmus K-D (1998) Glycine decarboxylation The free radical mechanism. J Am Chem Soc 120 9930-9940 Bonifacic M, Armstrong DA, Stefanic I, Asmus K-D (2003) Kinetic isotope effect for hydrogen abstraction by OH radicals from normal and carbon-deuterated ethyl alcohol in aqueous solution. J Phys Chem B 107 7268-7276... 

In principle, several routes exist for enzymatic isomaltose synthesis. With respect to cost-effectiveness it is obvious that one should use substrates like sucrose or starch that can be exploited by dextransucrase (EC 2.4.1.5) or glucoamylase (EC 3.2.1.3), respectively. However, in both cases, isomaltose represents a side product which is released only in small proportions next to dextran or glucose as main products. Realization of higher yields requires extensive time and effort with respect to engineering of reaction and catalyst design. Based on kinetic investigations dextransucrase has been chosen for the production of isomaltose with sucrose as the substrate, and glucose as an acceptor (see Sect. 2.1). 

Dextranase has been immobilized by adsorption onto porous titanium(iv) oxide particles coated with diazotized 1,3-diaminobenzene. Investigations of the effects of changes in dextran concentration, pH, temperature, and flow rate upon a continuously operated column of the immobilized dextranase permitted assessment of the kinetic aspects of the system via Lineweaver-Burk plots. 

Figure 5 illustrates the effect the urea in concentration from 10 to 10 mol/1 produces on fluorescence spectra of capsules containing SNARF-1 dextran and urease. Urea concentration dependence is reflected spectroscopically by apparent pH change in the course of enzymiatic reaction inside the capsules. The ammonium ions generated via enzymatic reaction in capsule interior effect on pH shift what is recorded by SNARF-1 on the plot (Fig. 5). The fluorescent spectra were measured at the 30-min time point after adding urea solutions at these concentrations to the SNARF-1 dextran/urease capsule s samples. Our particular attention was paid to the kinetics of the change at the fluorescence intensity ratio at 580 nm to 640 nm R (Fig. 6) and its relevance to amount of SNARF/urease. Parameter R was plotted versus time and as one can see on curves at high concentration...

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