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Biological Reactions (biological + reaction)
Selected AbstractsCombined use of nuclear magnetic resonance and infrared spectroscopy for studying recognition processes between amphenicolic antibiotics and albuminMAGNETIC RESONANCE IN CHEMISTRY, Issue 7 2003Silvia Martini Abstract Biological reactions are mostly concerned with selective interactions between small ligands and macromolecular receptors. The same ligands may activate responses of different intensities and/or effects in the presence of different receptors. Many approaches based on spectroscopic and non-spectroscopic methods have been used to study interactions between small ligands and macromolecular receptors, including methods based on NMR and IR spectroscopic analysis of the solution behaviour of the ligand in the presence of receptors. In this work, we investigated the interaction between ovine serum albumin with two amphenicolic antibiotics [chloramphenicol (CAP) and thiamphenicol (TAP)], using a combined approach based on NMR and IR methodologies, furnishing complementary information about the recognition process occurring within the two systems. The two ligands, despite their similar structures, showed different affinities towards albumin. NMR methodology is based on the comparison of selective () and non-selective () spin,lattice relaxation rates of the ligands in the presence and absence of macromolecular receptors and and temperature dependence analysis. From these studies, the ligand,receptor binding strength was evaluated on the basis of the ,affinity index.' The derivation of the affinity index from chemical equilibrium kinetics for both the CAP,albumin and TAP,albumin systems allowed a comparison of the abilities of the two amphenicolic antibiotics to interact with the protein. IR methodology is based on the comparison of the ligand,protein ,complex' spectra with those of the non-interacting systems. On the basis of the differences revealed, a more thorough IR analysis was performed in order to understand the structural changes which occurred on both ligand and protein molecules within the interacting system. Copyright © 2003 John Wiley & Sons, Ltd. [source] Biological Reactions Resulting from Endotoxin Adsorbed on Dialysis Membrane: An In Vitro StudyARTIFICIAL ORGANS, Issue 2 2004Kenji Tsuchida Abstract:, Some types of dialysis membrane are known to adsorb endotoxin (ET). It is suggested that the biocompatibility of dialysis membrane is enhanced by adsorption and inhibition of ET. This study attempts to clarify the membrane-mediated biological reaction of the ET that is adsorbed to a dialysis membrane. After a dialysis circuit was prepared, contaminated dialysate was introduced on the dialysate side of a polyether polymer alloy (PEPA) membrane that adsorbs ET while saline solution or blood were introduced on the blood side, and the difference in ET adsorption between the two set-ups was measured. Further, the side filled with blood was left standing for 2 h, after which the changes in the amount of interleukin 1 receptor antagonist (IL-1Ra) produced from the whole blood were also assayed. Significantly more ET was adsorbed to the dialysis membrane when blood rather than saline was on the other side. In addition, the IL-1Ra production from the dialysis membrane that adsorbed ET was significantly higher. The ET adsorbed to the dialysis membrane may influence a living body even if it does not pass through the membrane. Accordingly, it is difficult to assume that the adsorption of ET to the membrane enhances its biocompatibility. [source] Improved model of secondary clarifier in A2/O processASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009Ma Longhua Abstract The complex behavior of the secondary clarifier and its great importance in the successful operation of the activated sludge process (ASP) have made the settling process a major issue for researchers working in the field of mathematical modeling. So, a precise model of the secondary clarifier can describe the actual behavior of a sewage plant better. But in ASM2, the solid/liquid separation in a secondary clarifier, which is highly nonlinear, is not considered. The solid/liquid separation affects not only the biological reaction but also the quality of the effluent. In this paper an improved secondary clarifier model based on a one-dimensional settler model is established in terms of the solid flux concept and a mass balance. Through some given assumptions, a model of A2/O process including secondary clarifier is built, and then simulated. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Mouse RS21-C6 is a mammalian 2,-deoxycytidine 5,-triphosphate pyrophosphohydrolase that prefers 5-iodocytosineFEBS JOURNAL, Issue 6 2009Mari Nonaka Free nucleotides in living cells play important roles in a variety of biological reactions, and often undergo chemical modifications of their base moieties. As modified nucleotides may have deleterious effects on cells, they must be eliminated from intracellular nucleotide pools. We have performed a screen for ITP-binding proteins because ITP is a deaminated product of ATP, the most abundant nucleotide, and identified RS21-C6 protein, which bound not only ITP but also ATP. Purified, recombinant RS21-C6 hydrolyzed several canonical nucleoside triphosphates to the corresponding nucleoside monophosphates. The pyrophosphohydrolase activity of RS21-C6 showed a preference for deoxynucleoside triphosphates and cytosine bases. The kcat/Km (s,1·m,1) values were 3.11 × 104, 4.49 × 103 and 1.87 × 103 for dCTP, dATP and dTTP, respectively, and RS21-C6 did not hydrolyze dGTP. Of the base-modified nucleotides analyzed, 5-I-dCTP showed an eightfold higher kcat/Km value compared with that of its corresponding unmodified nucleotide, dCTP. RS21-C6 is expressed in both proliferating and non-proliferating cells, and is localized to the cytoplasm. These results show that RS21-C6 produces dCMP, an upstream precursor for the de novo synthesis of dTTP, by hydrolyzing canonical dCTP. Moreover, RS21-C6 may also prevent inappropriate DNA methylation, DNA replication blocking or mutagenesis by hydrolyzing modified dCTP. [source] A thermodynamic analysis of the activated sludge process: Application to soybean wastewater treatment in a sequencing batch reactorAICHE JOURNAL, Issue 10 2009Bing-jie Ni Abstract A bioenergetic methodology was integrated with a modified activated sludge model No.1 (ASM1) to analyze the activated sludge process, with the treatment of soybean-processing wastewater as an example. With the bioenergetic methodology established by McCarty and coworkers, the microbial yield was predicted and the overall stoichiometrics for biological reactions involving the key chemical and biological species in activated sludge were established. These obtained parameters were related to the ASM1 model, which was modified after coupling the biological reactions in activated sludge with electron balances. This approach was able to approximately describe the treatment of soybean wastewater by activated sludge in a sequencing batch reactor in terms of substrate utilization, biomass growth, and the elector acceptor consumption. Such an attempt provides useful information for accurate modeling of the complex activated sludge process. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] General hybrid multizonal/CFD approach for bioreactor modelingAICHE JOURNAL, Issue 8 2003F. Bezzo A critical issue in the modeling of aerobic bioreactors is the close interaction between fluid flow and the biological reactions. In particular, shear rate has a large effect on the broth viscosity which, in turn, affects the rate of mass transfer of oxygen from the gas to the liquid phase. We demonstrate how a generic hybrid multizonal/computational fluid dynamics (CFD) modeling approach can be applied to take account of these interactions. The approach to multizonal modeling presented characterizes the flow rates between adjacent zones, and also the fluid mechanical quantities, such as the shear stress, that have important effects on the process behavior within each zone, by means of steady-state CFD calculations. An unstructured model for xanthan gum production in a batch aerobic bioreactor is used for this purpose. The hybrid modeling approach is also applied to structured models involving distributions of cell mass within each zone. [source] Remodeling protein complexes: Insights from the AAA+ unfoldase ClpX and Mu transposasePROTEIN SCIENCE, Issue 8 2005Briana M. Burton Abstract Multiprotein complexes in the cell are dynamic entities that are constantly undergoing changes in subunit composition and conformation to carry out their functions. The protein,DNA complex that promotes recombination of the bacteriophage Mu is a prime example of a complex that must undergo specific changes to carry out its function. The Clp/Hsp100 family of AAA+ ATPases plays a critical role in mediating such changes. The Clp/Hsp100 unfolding enzymes have been extensively studied for the roles they play in protein degradation. However, degradation is not the only fate for proteins that come in contact with the ATP-dependent unfolding enzymes. The Clp/Hsp100 enzymes induce structural changes in their substrates. These structural changes, which we refer to as "remodeling," ultimately change the biological activity of the substrate. These biological changes include activation, inactivation (not associated with degradation), and relocation within the cell. Analysis of the interaction between Escherichia coli ClpX unfoldase and the Mu recombination complex, has provided molecular insight into the mechanisms of protein remodeling. We discuss the key mechanistic features of the remodeling reactions promoted by ClpX and possible implications of these findings for other biological reactions. [source] Protein Targeting into Secondary Plastids,THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 1 2009KATHRIN BOLTE ABSTRACT. Most of the coding capacity of primary plastids is reserved for expressing some central components of the photosynthesis machinery and the translation apparatus. Thus, for the bulk of biochemical and cell biological reactions performed within the primary plastids, many nucleus-encoded components have to be transported posttranslationally into the organelle. The same is true for plastids surrounded by more than two membranes, where additional cellular compartments have to be supplied with nucleus-encoded proteins, leading to a corresponding increase in complexity of topogenic signals, transport and sorting machineries. In this review, we summarize recent progress in elucidating protein transport across up to five plastid membranes in plastids evolved in secondary endosymbiosis. Current data indicate that the mechanisms for protein transport across multiple membranes have evolved by altering pre-existing ones to new requirements in secondary plastids. [source] Modeling the partial nitrification in sequencing batch reactor for biomass adapted to high ammonia concentrationsBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2006V. Pambrun Abstract Partial nitrification has proven to be an economic way for treatment of industrial N-rich effluent, reducing oxygen and external COD requirements during nitrification/denitrification process. One of the key issues of this system is the intermediate nitrite accumulation stability. This work presents a control strategy and a modeling tool for maintaining nitrite build-up. Partial nitrification process has been carried out in a sequencing batch reactor at 30°C, maintaining strong changing ammonia concentration in the reactor (sequencing feed). Stable nitrite accumulation has been obtained with the help of an on-line oxygen uptake rate (OUR)-based control system, with removal rate of 2 kg NH -N,·,m,3/day and 90%,95% of conversion of ammonium into nitrite. A mathematical model, identified through the occurring biological reactions, is proposed to optimize the process (preventing nitrate production). Most of the kinetic parameters have been estimated from specific respirometric tests on biomass and validated on pilot-scale experiments of one-cycle duration. Comparison of dynamic data at different pH confirms that NH3 and NO should be considered as the true substrate of nitritation and nitratation, respectively. The proposed model represents major features: the inhibition of ammonia-oxidizing bacteria by its substrate (NH3) and product (HNO2), the inhibition of nitrite-oxidizing bacteria by free ammonia (NH3), the INFluence of pH. It appears that the model correctly describes the short-term dynamics of nitrogenous compounds in SBR, when both ammonia oxidizers and nitrite oxidizers are present and active in the reactor. The model proposed represents a useful tool for process design and optimization. © 2006 Wiley Periodicals, Inc. [source] | |||||||||||||