[Show abstract][Hide abstract] ABSTRACT: A new magnetic mesocellular mesoporous silica support featuring a 3D open-pore structure has been developed for highly efficient, filtration-free recycling of chiral ligands for catalytic asymmetric dihydroxylation. Reactions using the ligand immobilized on this magnetic silica system exhibited almost the same reactivity and enantioselectivity as those obtained in the homogeneous reaction. Magnetically recovered ligand could be recycled eight times with good to excellent conservation of reaction rates and enantioselectivities.
No preview · Article · Jan 2006 · Advanced Synthesis & Catalysis
[Show abstract][Hide abstract] ABSTRACT: Glucose-Oxidase (GOx) wurde in einem magnetischen mesozellulären Kohlenstoffschaum immobilisiert, indem sie mittels Glutaraldehyd vernetzt wurde. Mit diesem Material wurde ein magnetisch schaltbares bioelektrokatalytisches System aufgebaut, in dem die katalytische Oxidation von Glucose über die Positionierung eines externen Magneten nahe und fern der Elektrode ein- und ausgeschaltet werden konnte (siehe Schema).
Full-text · Article · Nov 2005 · Angewandte Chemie
[Show abstract][Hide abstract] ABSTRACT: Nanostructured magnetic materials (NMMs) have attracted much attention recently because of their broad biotechnological applications including support matrices for enzyme immobilization, immunoassays, drug delivery, and biosensors.[ 5] Specifically, the easy separation and controlled placement of NMMs by means of an external magnetic field enables their application in the development of immobilized enzyme processes and the construction of magnetically controllable bio-electrocatalytic systems.[5, 6] Herein, we demonstrate the use of immobilized enzymes in NMMs for magnetically switchable bio-electrocatalysis.
Full-text · Article · Nov 2005 · Angewandte Chemie International Edition
[Show abstract][Hide abstract] ABSTRACT: Magnetically separable ordered mesoporous carbon containing magnetic nanoparticles embedded in the carbon walls was synthesized using a simple synthetic procedure. The resulting magnetically separable mesoporous carbon was denoted as M-OMC (magnetically separable ordered mesoporous carbon) poly(pyrrole) with residual Fe2+ ions in the mesoporous channel was converted to carbon material containing superparamagnetic nanoparticles. The size of the magnetic nanoparticles obtained was restricted by the channel size of the SBA-15 silica template, which resulted in the generation of superparamagnetic nanoparticles embedded in the carbon rods. The blocking temperature of M-OMC is 110 K. Pore size and textural property of M-OMC is similar to that of hexagonally ordered mesoporous carbon fabricated using SBA-15 silica as a template. The saturation magnetization of M-OMC is ca. 30.0 emu/g at 300 K, high enough for magnetic separation.
[Show abstract][Hide abstract] ABSTRACT: Hierarchically ordered mesocellular mesoporous silica materials (HMMS) were synthesized using a single structure-directing agent. The mesocellular pores are synthesized without adding any pore expander; the pore walls are composed of SBA-15 type mesopores. Small-angle X-ray scattering revealed the presence of uniform pore structures with two different sizes. Using HMMS as a nanoscopic template, hierarchically ordered mesocellular mesoporous carbon (HMMC) and polymer (HMMP) materials were synthesized. HMMS was used as a host for enzyme immobilization. To improve the retention of enzymes in HMMS, we adsorbed enzymes, and then employed crosslinking using glutaraldehyde (GA). The resulting crosslinked enzyme aggregates (CLEAs) show an impressive stability with extremely high enzyme loadings. For example, 0.5 g alpha-chymotrypsin (CT) could be loaded in 1 g of silica with no activity decrease observed with rigorous shaking over one month. In contrast, adsorbed CT without GA treatment resulted in a lower loading, which further decreased due to continuous leaching of adsorbed CT under shaking. The activity of crosslinked CT aggregates in HMMS was approximately 10 times higher than that of the adsorbed CT, which represents a 74-fold increase in activity per unit weight of HMMS due to higher CT loading.