A generic model for diffusive dynamics of the substrate and fluorescein tagged enzyme in microfluidic platform

Microsystem Technologies - The aim of this study was to develop a model that describes enzymatic conversion in a microfluidic system along with convective and diffusive transport of...     

Effect of feeding pattern on biochemical storage by activated sludge under anoxic conditions

This study investigated the effect of feeding pattern on bacterial storage under anoxic conditions, emphasizing previous adaptation of biomass to a long term feeding condition, under steady-state operation. Storage was evaluated in a sequencing batch reactor (SBR) system operated in a sequence of anoxic/aerobic phases, fed with acetate as the sole carbon source during anoxic conditions. The experimental results indicated that biochemical storage of acetate as PHB occurred when substrate was fed as a pulse, while acetate was removed mostly through direct microbial growth under continuous feeding. For pulse feeding, the anoxic yield, Y(STOD) was calculated as 0.58mg COD (mgCOD)(-1) in two different ways, using mass balances on acetate utilization, PHB generation and nitrate consumption. This value was supported by parallel batch tests and similar results in the literature. Similarly, the rate coefficient for storage under anoxic conditions, k(STOD) was computed as 9.3day(-1) based on basic stoichiometry and model calibration of experimental data. Batch tests conducted with biomass adapted to different feeding patterns showed that substrate storage was insignificant when the feed was added continuously at low concentrations, even if the biomass was previously adapted to storage. Similarly biomass acclimated to continuous feeding could not store the excess substrate although fed instantly. For the operating conditions selected for the study, storage response was significant only with a microbial culture with metabolic activities previously adapted to storage and with short-term substrate feeding at high concentrations.     

Synthesis,characterization, and colloidal properties of polythiophene/borax conducting composite

In this study, synthesis of polythiophene (PT) and polythiophene/borax pentahydrate (PT/borax) conducting composite were carried out by in‐situ oxidative polymerization. The composite was subjected to various characterization techniques namely: FTIR, particle size, magnetic susceptibility, density, conductivity, dielectric, TGA, XRD, SEM, and zeta (ζ)‐potential measurements. The effects of time, pH, various surfactants, electrolytes and temperature on the ζ‐potential of PT and PT/borax composite were investigated. In a basic medium the ζ‐potential of the composite was observed to decrease up to ζ = −66.5 mV. The most effective surfactant on the ζ‐potential of the composite was sodium dodecyl sulfate, which reduced the value of ζ‐potential to ζ = −39.2 mV. It was concluded that the presence of mono‐valent (NaCl) salt has no impact on ζ‐potential whereas, di‐valent (BaCl₂) salt shifted the ζ‐potential value to more positive regions. Elevated temperatures caused almost no change on the ζ‐potential of the composite. Also an electrorheological effect (a tremendous viscosity increase) was determined from the PT/borax colloidal systems under an externally applied electric field, and the results obtained will be discussed in the forthcoming article. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

The effect of surface treatments on the bonding strength of ceramic inlays to dentin

Aim: To compare and evaluate the effects of different surface treatments on surface roughness and the microtensile bonding strengths of four different ceramics to dentin. Methods: 160 human molar teeth were used. The teeth were divided into four groups (n = 40). FC (Finesse), LC (IPS Empress Esthetics), LDC (IPS Empress e-Max) and MZC (Zirkonzahn Prettau) ceramic restorations were prepared. The specimens were divided into eight groups: (1) control, (2) air abrasion (AA), (3) HF acid etching (HF), (4) experimental hot etching (EHE), (5) Nd:YAG laser irradiation, (6) Nd:YAG laser + air abrasion, (7) Nd:YAG laser + HF acid, and (8) Nd:YAG laser + experimental hot etching. The surface roughness of the ceramics was determined with atomic force microscopy. After the cementation process, the specimens were thermal cycled and subjected to a microtensile bond strength (MBS) test. Two-way ANOVA and a Tukey’s test were used to analyse the surface roughness and MBS values of variance (p = 0.05). Results: HF acid etching showed the highest surface roughness in FC (p < 0.05). HF increased MBS in LC specimens where AA and HF increased MBS in LCD specimens. For the MZC specimens, AA and Nd:YAG + AA was effective in increasing the MBS (p < 0.05). Conclusion: Different surface treatments must be applied to different ceramics to improve the mechanical retention and MBS.     

Batch and Continuous Hydrolysis of Lactose Using P-Galactosidase Immobilized on Gelatin-Cmc

β-Galactosidase enzyme (E.C. 3.2.1.23) was immobilized onto a gelatin-carboxymethylcellulose carrier system by using cross-linker chromium acetate. A relative activity increase of 33% was achieved by adding carboxymethylcellulose to gelatin. The effect of operation temperature and pH on relative activity and reusability of the immobilized enzyme was investigated. A fluidized-bed reactor with a down flow mechanism was used for continuous process hydrolysis, and a constant glucose production rate was obtained.     

Favorable scaffolds: proteins with different sequence, structure and function may associate in similar ways

Proteins with similar structures may have different functions. Here, using a non-redundant two-chain protein-protein interface dataset containing 103 clusters, we show that this paradigm extends to interfaces. Whereas usually similar interfaces are obtained from globally similar chains, this is not always the case. Remarkably, in some interface clusters, although the interfaces are similar, the overall structures and functions of the chains are different. Hence, our work suggests that different folds may combinatorially assemble to yield similar local interface motifs. The preference of different folds to associate in similar ways illustrates that the paradigm is universal, whether for single chains in folding or for protein-protein association in binding. We analyze and compare the two types of clusters. Type I, with similar interfaces, similar global structures and similar functions, is better packed, less planar, has larger total and non-polar buried surface areas, better complementarity and more backbone-backbone hydrogen bonds than Type II (similar interfaces, different global structures and different functions). The dataset clusters may provide rich data for protein-protein recognition, cellular networks and drug design. In particular, they should be useful in addressing the difficult question of what the favorable ways for proteins to interact are.     

Characterization of polypyrrole/azocalix[4]arene salts: Electrical properties and thermal stability

Polypyrrole (PPy) was doped with the azocalix[4]arene [(5,11,17,23‐tetrakis[(p‐carboxyphenyl)azo]25,26,27,28‐tetrahydroxycalix[4]arene)] host species. PPy/azocalix[4]arene salts were characterized by FTIR, TGA, SEM, X‐ray diffraction, and conductivity measurements. The properties of PPy were investigated in the presence of azocalix[4]arene host species. The conductivity of PPy increased in the presence of azocalix[4]arene. TGA results indicated that the PPy/azocalix[4]arene salts have higher thermal stability than PPy. It was observed from SEM analysis that the particle diameter of PPy decreased with increasing content of azocalix[4]arene. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010