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Hydrolysis Step (hydrolysis + step)
Selected AbstractsNovel and Efficient Chemoenzymatic Synthesis of D -Glucose 6-Phosphate and Molecular Modeling Studies on the Selective BiocatalysisEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2007Tatiana Rodríguez-Pérez Abstract A concise chemoenzymatic synthesis of glucose 6-phosphate is described. Candida rugosa lipase was found to be an efficient catalyst for both regio- and stereoselective deacetylation of the primary hydroxy group in the peracetylated D -glucose. In addition, we report an improved synthesis of 1,2,3,4,6-penta- O -acetyl-,- D -glucopyranose providing a large-scale procedure for the acetylation of ,- D -glucose without isomerization at the anomeric center. The high overall yield and the easy scalability makes this chemoenzymatic strategy attractive for industrial application. Furthermore, molecular modeling of phosphonate transition-state analog for the enzymatic hydrolysis step supports the substrate selectivity observed with Candida rugosa lipase.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] A DFT study on the hydrolysis mechanism of NH-tautomeric antitumors of [HL][trans -RuCl4L(dmso- S)]INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 6 2010Jin Can Chen Abstract The hydrolysis process of Ru (III) complex [Htrz][trans -RuCl4(1- H -1,2,4-triazole)(dmso- S)] 1, a potential antitumor complex similar to the well-known anticancer agent [ImH][trans -RuCl4(Im)(dmso- S)] (NAMI-A), has been investigated by using density functional theory (DFT) method, and the solvent effect was also considered and calculated by conductor-like polarizable calculation model (CPCM). Meanwhile, the hydrolysis process of the NH-tautomeric isomer, [Htrz][trans -RuCl4(4- H -1,2,4-triazole)(dmso- S)] 2, was also modeled and predicted by the same methods. The structural characteristics and the detailed energy profiles for the hydrolysis processes of two isomers have been obtained. The analysis of thermodynamic and kinetic characteristics of hydrolysis reaction suggests the following: for the first hydrolysis step, the Complex 1 has lower hydrolysis rate than the reported anticancer drug NAMI-A, and the result is in accordance with experimental one. However, Complex 1 has obviously higher hydrolysis rate than its isomer Complex 2, and the result was reasonably explained in theory. For the second hydrolysis step, the formation of cis -diaqua species is thermodynamic preferred to that of trans isomers. In addition, the trend in nucleophilic attack abilities (A) of hydrolysis products by pertinent biomolecules was revealed and predicted. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Pretreatment of barley husk for bioethanol productionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2005Beatriz Palmarola-Adrados Abstract This paper reports on the optimization of steam pretreatment of barley husk for high pentose and hexose recovery in the subsequent enzymatic hydrolysis step, as well as high ethanol yield, following simultaneous saccharification and fermentation. The parameters optimized in the steam pretreatment step were residence time (5,15 min), temperature (190,215 °C), and concentration of the acid catalyst (0 or 0.5% H2SO4). A microwave oven was employed for screening of the optimal conditions to obtain the highest sugar yield following combined pretreatment and enzymatic hydrolysis. The final optimization of the pretreatment prior to enzymatic hydrolysis was performed on a larger scale, in a steam pretreatment unit. Simultaneous saccharification and fermentation was carried out following steam pretreatment on 5 and 10% dry matter steam-pretreated slurries. Fermentability tests were performed to determine the effect of by-products (ie furfural and 5-hydroxymethyl furfural) in the bioconversion of glucose to ethanol by baker's yeast. The maximum glucose yield, 88% of the theoretical, was obtained following steam pretreatment with 0.5% H2SO4 at 200 °C for 10 min. Under these conditions, a sugar to ethanol conversion of 81% was attained in simultaneous saccharification and fermentation. Copyright © 2004 Society of Chemical Industry [source] A novel microplate-based screening strategy to assess the cellulolytic potential of Trichoderma strainsBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2010Stefano Cianchetta Abstract Bioconversion of lignocellulosic biomass to fuel requires a hydrolysis step to obtain fermentable sugars, generally accomplished by fungal enzymes. An assorted library of cellulolytic microbial strains should facilitate the development of optimal enzyme cocktails specific for locally available feedstocks. Only a limited number of strains can be simultaneously assayed in screening based on large volume cultivation methods, as in shake flasks. This study describes a miniaturization strategy aimed at allowing parallel assessment of large numbers of fungal strains. Trichoderma strains were cultivated stationary on microcrystalline cellulose using flat bottom 24-well plates containing an agarized medium. Supernatants obtained by a rapid centrifugation step of the whole culture plates were evaluated for extracellular total cellulase activity, measured as filter paper activity, using a microplate-based assay. The results obtained were consistent with those observed in shake-flask experiments and more than 300 Trichoderma strains were accordingly characterized for cellulase production. Five strains, displaying on shake-flasks at least 80% of the activity shown by the hyper-cellulolytic mutant Trichoderma Rut-C30, were correctly recognized by the screening on 24-well plates, demonstrating the feasibility of this approach. Cellulase activity distribution for the entire Trichoderma collection is also reported. One strain (T. harzianum Ba8/86) displayed the closest profile to the reference strain Rut-C30 in time course experiments. The method is scalable and addresses a major bottleneck in screening programs, allowing small-scale parallel cultivation and rapid supernatant extraction. It can also be easily integrated with high-throughput enzyme assays and could be suitable for automation. Biotechnol. Bioeng. 2010;107: 461,468. © 2010 Wiley Periodicals, Inc. [source] Influence of dT20 and [d(AT)10]2 on Cisplatin Hydrolysis Studied by Two-Dimensional [1H,15N] HMQC NMR SpectroscopyCHEMISTRY - A EUROPEAN JOURNAL, Issue 13 2005Jo Vinje Dr. Abstract The influence of the presence of DNA on the kinetics of cisplatin (cis -[PtCl2(NH3)2]) aquation (replacement of Cl, by H2O) and anation (replacement of H2O by Cl,) involved in the hydrolysis of cisplatin have been determined by two-dimensional [1H,15N] HMQC NMR spectroscopy. Single-stranded dT20 and double-stranded [d(AT)10]2 oligonucleotides were used as DNA models, avoiding guanines which are known to react rapidly with aquated cisplatin forms. Reactions starting from cis -[PtCl2(15NH3)2], or from a stoichiometric mixture of cis -[Pt(15NH3)2(H2O)2]2+ and Cl, (all 0.5,mM PtII; in ionic strength, adjusted to 0.095,M or 0.011,M with NaClO4, pH between 3.0 and 4.0) were followed in an NMR tube in both the absence and presence of 0.7,mM dT20 or [d(AT)10]2. In the presence of dT20, we observed a slight and ionic-strength-independent decrease (15,20,%) of the first aquation rate constant, and a more significant decrease of the second anation rate constant. The latter was more important at low ionic strength, and can be explained by efficient condensation of cis -[Pt(15NH3)2(H2O)2]2+ on the surface of single-stranded DNA, in a region depleted of chloride anions. At low ionic strength, we observed an additional set of [1H,15N] HMQC spectral signals indicative of an asymmetric species of PtN2O2 coordination, and we assigned them to phosphate-bound monoadducts of cis -[Pt(15NH3)2(H2O)2]2+. Double-stranded [d(AT)10]2 slowed down the first aquation step also by approximately 15,%; however, we could not determine the influence on the second hydrolysis step because of a significant background reaction with cis -[Pt(NH3)2(H2O)2]2+. [source] Identification of Putative Binding Sites of P-glycoprotein Based on its Homology ModelCHEMMEDCHEM, Issue 2 2008Christoph Globisch Abstract A homology model of P-glycoprotein based on the crystal structure of the multidrug transporter Sav1866 is developed, incorporated into a membrane environment, and optimized. The resulting model is analyzed in relation to the functional state and potential binding sites. The comparison of modeled distances to distances reported in experimental studies between particular residues suggests that the model corresponds most closely to the first ATP hydrolysis step of the protein transport cycle. Comparison to the protein 3D structure confirms this suggestion. Using SiteID and Site Finder programs three membrane related binding regions are identified: a region at the interface between the membrane and cytosol and two regions located in the transmembrane domains. The regions contain binding pockets of different size, orientation, and amino acids. A binding pocket located inside the membrane cavity is also identified. The pockets are analyzed in relation to amino acids shown experimentally to influence the protein function. The results suggest that the protein has multiple binding sites and may bind and/or release substrates in multiple pathways. [source] | ||||||||||