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131.
Veria Addorisio Filomena Sannino Cesar Mateo Jose M. Guisan 《Process Biochemistry》2013,48(8):1174-1180
The hydrolysis of phenolic compounds using an immobilized and highly active and stable derivative of laccase from Trametes versicolor is presented. The enzyme was immobilized on aldehyde supports. For this, the enzyme was enriched in amino groups by chemical modification of its carboxyl groups. The aminated enzyme was immobilized with a high recovered activity (over 60%). Aldehyde derivatives were more stable than soluble or aminated-soluble enzyme and the reference derivatives after incubation in different inactivating conditions (high temperatures, different pH values or presence of organic cosolvents). The most stable derivative was obtained immobilizing the chemically aminated enzyme at pH 10 on aldehyde supports with a stabilization factor approximately 280 fold after incubation at pH 7 and 55 °C. In addition, it was possible to prepare immobilized derivatives with a maximal enzyme loading of 60 mg g?1 of support. This derivative could be reused for 10 reaction cycles with negligible lost of activity. 相似文献
132.
Tilman Schlothauer Petra Rueger Jan Olaf Stracke Hubert Hertenberger Felix Fingas Lothar Kling Thomas Emrich Georg Drabner Stefan Seeber Johannes Auer Stefan Koch Apollon Papadimitriou 《MABS-AUSTIN》2013,5(4):576-586
The neonatal Fc receptor (FcRn) is important for the metabolic fate of IgG antibodies in vivo. Analysis of the interaction between FcRn and IgG in vitro might provide insight into the structural and functional integrity of therapeutic IgG that may affect pharmacokinetics (PK) in vivo. We developed a standardized pH gradient FcRn affinity liquid chromatography method with conditions closely resembling the physiological mechanism of interaction between IgG and FcRn. This method allows the separation of molecular IgG isoforms, degradation products and engineered molecules based on their affinity to FcRn. Human FcRn was immobilized on the column and a linear pH gradient from pH 5.5 to 8.8 was applied. FcRn chromatography was used in comparison to surface plasmon resonance to characterize different monoclonal IgG preparations, e.g., oxidized or aggregated species. Wild-type and engineered IgGs were compared in vitro by FcRn chromatography and in vivo by PK studies in huFcRn transgenic mice. Analytical FcRn chromatography allows differentiation of IgG samples and variants by peak pattern and retention time profile. The method can distinguish: 1) IgGs with different Fabs, 2) oxidized from native IgG, 3) aggregates from monomer and 4) antibodies with mutations in the Fc part from wild-type IgGs. Changes in the FcRn chromatographic behavior of mutant IgGs relative to the wild-type IgG correlate to changes in the PK profile in the FcRn transgenic mice. These results demonstrate that FcRn affinity chromatography is a useful new method for the assessment of IgG integrity. 相似文献
133.
Jonathan Griffin Darren C. Watters Hunan Yi Ahmed Iraqi David Lidzey Alastair R. Buckley 《Liver Transplantation》2013,3(7):903-908
Bulk heterojunction solar cells containing molybdenum oxide hole extracting anode contacts have been fabricated with varying stoicheometry using radio frequency reactive sputtering from a Molybdenum metal target. A blend of the newly synthesised conjugated polymer poly[9‐(heptadecan‐9‐yl)‐9H‐carbazole‐2,7‐diyl‐alt‐(5,6‐bis(octyloxy)‐4,7‐di(thiophen‐2‐yl)benzo[c][1,2,5]thiadiazole)‐5,5‐diyl] (PCDTBT‐8) and fullerene [6,6]‐Phenyl‐C71‐butyric acid methyl ester (PC70BM) was used as the photoactive layer and device results show that anodes with greater than 98% Molybdenum (VI) oxide result in peak power conversion efficiencies of 3.7%.The presence of up to 28% of Mo (V) results in no significant reduction in efficiency, however the presence of metallic Mo (IV) and lower oxidation states lead to severe reductions in device performance due to a combination of a large hole extraction energy barrier of approximately 0.9eV and reduced device stability. 相似文献
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136.
Immacolata Del Giudice Danila Limauro Emilia Pedone Simonetta Bartolucci Gabriella Fiorentino 《Biochimica et Biophysica Acta - Proteins and Proteomics》2013,1834(10):2071-2079
Microorganisms living in arsenic-rich geothermal environments act on arsenic with different biochemical strategies, but the molecular mechanisms responsible for the resistance to the harmful effects of the metalloid have only partially been examined. In this study, we investigated the mechanisms of arsenic resistance in the thermophilic bacterium Thermus thermophilus HB27. This strain, originally isolated from a Japanese hot spring, exhibited tolerance to concentrations of arsenate and arsenite up to 20 mM and 15 mM, respectively; it owns in its genome a putative chromosomal arsenate reductase (TtarsC) gene encoding a protein homologous to the one well characterized from the plasmid pI258 of the Gram + bacterium Staphylococcus aureus. Differently from the majority of microorganisms, TtarsC is part of an operon including genes not related to arsenic resistance; qRT-PCR showed that its expression was four-fold increased when arsenate was added to the growth medium. The gene cloning and expression in Escherichia coli, followed by purification of the recombinant protein, proved that TtArsC was indeed a thioredoxin-coupled arsenate reductase with a kcat/KM value of 1.2 × 104 M− 1 s− 1. It also exhibited weak phosphatase activity with a kcat/KM value of 2.7 × 10− 4 M− 1 s− 1. The catalytic role of the first cysteine (Cys7) was ascertained by site-directed mutagenesis. These results identify TtArsC as an important component in the arsenic resistance in T. thermophilus giving the first structural–functional characterization of a thermophilic arsenate reductase. 相似文献
137.
Yi Zhou Balaji Sundara Sekar Shuke Wu Zhi Li 《Biotechnology and bioengineering》2020,117(8):2340-2350
As an important bulk chemical, benzoic acid is currently manufactured from nonrenewable feedstocks under harsh conditions. Although there are natural pathways for biosynthesis of benzoic acid, they are often inefficient and subjected to complex regulation. Here we develop a nonnatural enzyme cascade to efficiently produce benzoic acid from styrene or biogenic L -phenylalanine under mild conditions. By using a modular approach, two whole-cell catalysts Escherichia coli LZ305 and LZ325 are engineered for coexpressing seven and nine enzymes for production of 133–146 mM benzoic acid (16.2–17.8 g/Laq) with 88–97% conversion via seven- and nine-step cascade biotransformation of styrene and L -phenylalanine, respectively. The seven-step cascade represents a formal high-yielding biocatalytic oxidative cleavage of styrene, and the nine-step cascade showcases the high efficiency of extended nonnatural enzyme cascades. Moreover, to achieve benzoic acid production directly from low-cost renewable glycerol, a novel coupled fermentation-biotransformation process was developed by integration of fermentative production of L -phenylalanine with in situ biotransformation to give 63–70 mM benzoic acid (7.6–8.6 g/Laq), which is around 20 times higher than the reported value via a natural pathway. The coupled fermentation-biotransformation process could be generally applicable to microbial production of growth-inhibitory or toxic chemicals in high concentrations. 相似文献
138.
Maurizio Bruschi Giovanni Candiano Laura Santucci Gian Marco Ghiggeri 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013
Background
Proteins are extremely reactive to oxidants and should represent a potential target of instable reactive oxygen. This may represent a problem for plasma proteins since they may be directly modified in vivo in a compartment where antioxidant enzymatic systems are scarcely represented. On the other hand, it is possible that some plasma components have evolved over time to guarantee protection, in which case they can be considered as anti-oxidants.Scope of review
To present and discuss main studies which addressed the role of albumin in plasma antioxidant activity mainly utilizing in vitro models of oxidation. To present some advances on structural features of oxidized albumin deriving from studies carried out on in vitro models as well as albumin purified in vivo from patients affected by clinical conditions characterized by oxidative stress.Major conclusions
There are different interaction with HOCl and chloramines. In the former case, HOCl produces an extensive alteration of 238Trp and 162Tyr, 425Tyr, 47Tyr, while thiol groups are only partially involved. Chloramines are extremely reactive with the unique free SH group of albumin (34Cys) with the formation of sulfenic and sulfinic acid as intermediates and sulfonic acid as end-product. Oxidized albumin has a modified electrical charge for the addition of an acidic residue and presents α-helix and random coil reorganization with subtle changes in domain orientation.General significance
Albumin, is the major antioxidants in plasma with a concentration (0.8 mM) higher than other antioxidants by an exponential factor. Functional and protective roles in the presence of oxidative stress must be defined. This article is part of a Special Issue entitled Serum Albumin. 相似文献139.
AbstractThis article describes an electrochemical method to remove bacterial biofilm from a stainless steel (SS) surface using a potential pulse/reverse pulse technique. This technique employs a periodic waveform that consists of anodic and cathodic pulses. The pulses can effectively strip a thin layer of metal off the SS surface, along with the adherent biofilm, in a saline solution. Not only can the pulses effectively remove biofilm from the SS surface, but they also regenerate the original mirror-like shiny surface. The importance of this electrochemical biofilm removal method is its wide applicability for any types of biofilms. That is, instead of directly removing the biofilm, it removes a very thin layer of the metal under the biofilm. Thus, the removal process is independent to the nature of the biofilms. Furthermore, this electrochemical biofilm removal method is rapid (less than 30?s of potential pulse time) and does not require hazardous chemicals. 相似文献
140.
Disulfide bonds formed by the oxidation of cysteine residues in proteins are the major form of intra- and inter-molecular covalent linkages in the polypeptide chain. To better understand the conformational energetics of this linkage, we have used the MP2(full)/6-31G(d) method to generate a full potential energy surface (PES) for the torsion of the model compound diethyl disulfide (DEDS) around its three critical dihedral angles (χ2, χ3, χ2′). The use of ten degree increments for each of the parameters resulted in a continuous, fine-grained surface. This allowed us to accurately predict the relative stabilities of disulfide bonds in high resolution structures from the Protein Data Bank. The MP2(full) surface showed significant qualitative differences from the PES calculated using the Amber force field. In particular, a different ordering was seen for the relative energies of the local minima. Thus, Amber energies are not reliable for comparison of the relative stabilities of disulfide bonds. Surprisingly, the surface did not show a minimum associated with χ2~ ? 60°, χ3~90, χ2′~ ? 60°. This is due to steric interference between Hα atoms. Despite this, significant populations of disulfides were found to adopt this conformation. In most cases this conformation is associated with an unusual secondary structure motif, the cross-strand disulfide. The relative instability of cross-strand disulfides is of great interest, as they have the potential to act as functional switches in redox processes. 相似文献