•Magnetic stimuli-responsive biocatalytic membrane reactor was optimized.•It was stable over a broad range of various operating parameters.•Flux and feed concentration, related by reactor productivity were crucial parameters.•Productivity increased with increased enzyme amount, despite the universal trend.•There was no enzyme leakage, activity decay or TMP rise continuously over 240 h.In this work, the performance of an innovative magnetic responsive biocatalytic membrane reactor (BMRSP) has been investigated under various operational parameters. In particular, feed concentrations, flow rates across the bed, temperature and amount of biocatalytic bead were varied to probe the flow-dependent transport and kinetic properties of the reaction and the subsequent hydrolytic performance of the BMRSP. The rate of fouling for the BMRSP was always lower than a corresponding control system. For a given enzymatic concentration, a constant foulant hydrolyzing capacity is identified. At 3 g/m2 pectinase containing bionanocomposites, the BMRSP hydrolytic efficiency was 1.5 g/m2 h. This efficiency was further increased by increasing the amount of bionanocomposites per membrane area. This further allowed the BMRSP to hydrolyze higher loads of foulants while keeping a low if not zero increase in TMP over time at constant flux.Identification of an optimal operating condition laid the platform for continuous operation of the BMRSP over 200 h, without visible transmembrane pressure drift while maintaining constant flux. Product assay in the permeate gave constant value in the entire duration, i.e., no enzymatic activity decay owing to stable enzyme immobilization and no leakage through the pores of the membrane owing to the synergistic magnetic interaction between the magnetic membrane and magnetic bionanocomposites.The obtained stability over a broad range of operational parameters and sustainable performance over long period gives a high prospect to the newly developed BMRSP to be utilized in continuous biocatalysis and separation, thereby significantly improved process efficiency.Download high-res image (65KB)Download full-size image

The first hyperpolarizabilities of [Au25(SR)18]−1/0 and Au38(SR)24 clusters were determined by Hyper-Rayleigh Scattering. A strong dependence on the molecular symmetry was observed, and we explore two strategies to destroy the center of inversion in [Au25(SR)18]−1/0, protection by chiral ligands and alloying of the cluster with silver. This may open new avenues to applications of Au:SR clusters in second-order nonlinear optics.

•Magnetic nanoparticles used to prepare magnetic-responsive hybrid membrane.•Magnetic nanoparticles used for enzyme immobilization to form bionanocomposites.•Their magnetic interaction enhanced formation of dynamic enzyme layer on membrane.•Combination gave 75% reduced filtration resistance and multi-cycle membrane use.•Membrane usable life was prolonged.The synergistic magnetic interaction between biofunctionalized magnetic nanoparticles and a hybrid membrane is exploited to develop a nano-inspired, magnetic-responsive enzyme membrane (micro) reactor. The novelty of the process lies in the use of superparamagnetic nanoparticles both as enzyme carrier to form bionanocomposites and as nanofiller to form organic–inorganic (O/I) hybrid membrane to render both reversibly magnetizable. This reversible magnetic force facilitates dispersion of the enzymatically active magnetic nanoparticles (bionanocomposites) over the membrane surface, allows retention of the enzyme by a large pore, i.e., high-flux membrane and renders enzyme recovery after use is very easy. The feasibility and versatility of the concept is demonstrated through 2 case studies, i.e., a pectin/polygalacturonase and an arabinoxylan/xylanase system, for membrane fouling prevention through in-situ enzymatic membrane cleaning. This robust multidisciplinary approach resulted in a 75% reduction in filtration resistance, thus realizing significant energy savings and high reactor productivity. The advantages of the novel approach include: (i) absence of need for neither functionalized nor retentive membrane surfaces, (ii) no leakage of nanosized, high surface area immobilized enzymes through microporous membranes, (iii) full recovery and re-usability of the enzymes, (iv) possibility to apply enzyme cocktails to achieve optimal conversions and (v) use of the membrane beyond the enzyme life cycle.For color reproduction on the web and in black-and-white in print.

For the first time, second-harmonic generation microscopy (SHGM) has been employed to study zeolites. Large ZSM-5 crystals filled with p-nitroaniline (PNA) dipoles have been visualized. It is shown that SHGM can discriminate between the straight b-pores and the sinusoidal a-pores of this zeolite, thus revealing the intergrown structure of these crystals. Moreover, it is shown that dipole chains are formed not only in the b-pores but also in the a-pores. PNA only assembles into dipole chains of parallel orientation in those pores that are directly accessible from the outer surface. The area in which this PNA ordering prevails is limited to a strip near the outer surface of the zeolite crystal. A rationalization for these two observations is offered.

Second-harmonic generation microscopy (SHGM) has been employed to study crystals of zeolite-like material SAPO-5 filled with p-nitroaniline (PNA). The SHG and 2-photon fluorescence response of PNA in the one-dimensional channels readily reveals the pore accessibility; intergrown crystallites containing hexagonal pyramidal components and internal diffusion barriers are found next to seemingly perfect crystals. The sensitivity of second-harmonic generation to molecular orientation allowed for mapping of the domains of differently organized PNA. Dense domains of highly aligned PNA alternate with dilute zones with loosely aligned PNA.

Second-harmonic generation-circular dichroism (SHG-CD) effects in thin films of a chiral poly(3-alkylthiophene) have been investigated. Polarization patterns were recorded for several angles of incidence and analyzed using a recently developed optical model that takes all linear and non-linear optical achiral and chiral terms into account. From a complete analysis of the second-order susceptibility tensors, it is clear that SHG-CD in this particular system cannot be described by electric-dipole contributions only, but instead relies on the presence of strong magnetic-dipole contributions, similarly to linear optical CD effects.Second-harmonic generation-circular dichroism was used to study thin films of a chiral poly(alkyl)thiophene.

•Key amino acid residues for activity of a synthetically engineered μ-conotoxin.•Peptide engineering.•New leads for drug development.•Structure–activity relationship.Cone snail toxins or conotoxins are often small cysteine-rich peptides which have shown to be highly selective ligands for a wide range of ion channels such as voltage-gated sodium channels (NaVs). NaVs participate in a wide range of electrophysiological processes. Consequently, their malfunction has been associated with numerous diseases. The development of subtype-selective modulators of NaVs remains highly important in the treatment of such disorders. In order to expand our knowledge in the search for novel therapeutics to treat NaV-related diseases, we explored the field of peptide engineering. In the current study, the impact of well considered point mutations into a bioactive peptide that was found to be a very potent and selective inhibitor of NaVs (i.e. Midi R2) was examined. We designed two peptides, named Midi R2[A7G] and Midi R2[H10A, R12A] which have mutations at position 7, and both 10 and 12, respectively. Electrophysiological recordings indicated that an Ala to Gly mutation at position 7 increased IC50-values from the nanomolar range to the micromolar range. For Midi R2[H10A, R12A] at a concentration of 10 μM, activity is even reduced to 0–10% for all of the tested NaV-channels. Circular dichroism measurements proved that overall structural conformations did not change. These findings suggest that the minimal space between the second and the third intercysteine loop of Midi R2 is the sequence RRWARDHSR and that His at position 10 and Arg at position 12 are crucial amino acids for the potency and specificity of Midi R2. In this way, new insights into the structure–activity relationships of μ-conotoxins were found.

Second-harmonic generation microscopy (SHGM) has been employed to study crystals of zeolite-like material SAPO-5 filled with p-nitroaniline (PNA). The SHG and 2-photon fluorescence response of PNA in the one-dimensional channels readily reveals the pore accessibility; intergrown crystallites containing hexagonal pyramidal components and internal diffusion barriers are found next to seemingly perfect crystals. The sensitivity of second-harmonic generation to molecular orientation allowed for mapping of the domains of differently organized PNA. Dense domains of highly aligned PNA alternate with dilute zones with loosely aligned PNA.