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101.
102.
Aequationes mathematicae - 相似文献
103.
Ricardo M. Manzo Roberto J. Ceruti Horacio L. Bonazza Wellington S. Adriano Guillermo A. Sihufe Enrique J. Mammarella 《Applied biochemistry and biotechnology》2018,185(4):1029-1043
Carboxypeptidase A (CPA) is a metalloexopeptidase that catalyzes the hydrolysis of the peptide bonds that are adjacent to the C-terminal end of a polypeptide chain. The enzyme preferentially cleaves over C-terminal L-amino acids with aromatic or branched side chains. This is of main importance for food industry because it can be employed for manufacturing functional foods from different protein sources with reduced hydrophobic amino acid content for patients with deficiencies in the absorption or digestion of the corresponding amino acids. In that way, strategies for effective multipoint covalent immobilization of CPA metalloenzyme on chitosan beads have been developed. The study of the ability to produce several chemical modifications on chitosan molecules before, during and after its coagulation to form carrier beads lead in a protective effect of the polymer matrix. The chemical modification of chitosan through the use of an N-alkylation strategy produced the best derivatives. N-alkyl chitosan derivative beads with D-fructose presented values of 0.86 for immobilization yield, 314.6 IU g?1 bead for initial activity of biocatalyst and were 5675.64-fold more stable than the free enzyme at 55 °C. Results have shown that these derivatives would present a potential technological application in hydrolytic processes due to both their physical properties, such as low swelling capacity, reduced metal chelation ability and bulk mesoporosity, and increased operational stability when compared with soluble enzyme. 相似文献
104.
105.
Bordiga S Vitillo JG Ricchiardi G Regli L Cocina D Zecchina A Arstad B Bjørgen M Hafizovic J Lillerud KP 《The journal of physical chemistry. B》2005,109(39):18237-18242
Hydrogen storage is among the most demanding challenges in the hydrogen-based energy cycle. One proposed strategy for hydrogen storage is based on physisorption on high surface area solids such as metal-organic frameworks (MOFs). Within this class of materials, MOF-5 has been the first structure studied for hydrogen storage. The IR spectroscopy of adsorbed H2 performed at 15 K and ab initio calculations show that the adsorptive properties of this material are mainly due to dispersive interactions with the internal wall structure and to weak electrostatic forces associated with O13Zn4 clusters. Calculated and measured binding enthalpies are between 2.26 and 3.5 kJ/mol, in agreement with the H2 rotational barriers reported in the literature. A minority of binding sites with higher adsorption enthalpy (7.4 kJ/mol) is also observed. These species are probably associated with OH groups on the external surfaces present as termini of the microcrystals. 相似文献
106.
Liu Z Ma N Jia Y Bois-Choussy M Malabarba A Zhu J 《The Journal of organic chemistry》2005,70(7):2847-2850
[reaction: see text] Synthesis of enantiomerically pure beta-amino-alpha-hydroxy esters (1, 2) and beta-amino-alpha-azido ester (3) using Sharpless AA as a key step is described. A hitherto unreported side reaction, the oxidation of the beta-hydroxy-alpha-amino ester (5) into the alpha,alpha-di-tert-butyloxycarbamoyl-beta-ketoester (8) under AA conditions, is documented. 相似文献
107.
Plasma viral load (VL) values and CD4(+) cell count are employed clinically for initiation of therapy in the treatment of patients infected with human immunodeficiency virus (HIV), as previous clinical studies have shown a marked prevalence of acquired immunodeficiency syndrome (AIDS) development in seropositive individuals with VL values over 30 000 copies/mL. Many studies have shown that reduced glutathione (GSH) and cysteine (Cys) deficiency play an important role in the infection. We have developed capillary zone electrophoresis (CZE)-based assays and have used them to investigate the relationship between plasma and intracellular thiol levels and HIV-1 viremia in plasma. Blood samples from healthy volunteers and seropositive patients undergoing different antiretroviral regimes were analyzed in the study. The VL assay was based on CZE-UV detection of viral RNA at 260 nm. Determination of endogenous reduced Cys and GSH was achieved by CZE-UV detection of their mercurial complexes at 200 nm. We found that a decrease in GSH and Cys levels may be associated with disease progress. In fact, reduced GSH and Cys levels appear progressively reduced with increasing VL. 相似文献
108.
Readily available methyl hydrogen (R)-3-methylglutarate(2) is a useful chiral building block for the synthesis of several biologically active compounds. Enantiomerically pure (R)-2 has been employed to synthesize stereospecifically each of the two enantiomers, 1a and 1b, of 10-methyl-2-tridecanone, the sex pheromone of the southern corn rootworm, Diabrotica undecimpunctata howardi Barber. Compound (R)-2 has been also used to prepare 99% optically pure (R)-3-methyl-1-pentanol (6) and enantiomerically pure (R)-5-methyl-i-tricosyne (7). These compounds are useful building blocks suitable for the further elaboration to other chiral insect pheromones. 相似文献
109.
Sabrina M. Nobre Mauro N. Muniz Marcus Seferin Wagner M. da Silva Adriano L. Monteiro 《应用有机金属化学》2011,25(4):289-293
We have developed a sequential and selective Pd‐catalyzed double‐Heck arylation of ethylene that results in non‐symmetrical nitro‐stilbene analogs of trans‐resveratrol at excellent yields. A catalytic system consisting of Pd(OAc)2 and P(o‐tolyl)3 permitted us to carry out the two consecutive Heck arylations without losing activity from the first to the second Heck reaction. After the first Heck arylation of ethylene, no isolation or additional catalyst loading is required for the second Heck arylation reaction. This protocol was applied to the synthesis of methylated trans‐resveratrol, which was obtained at a 65% overall yield. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
110.
Adriano Mollica Federica Feliciani Ivana Cacciatore Gino Lucente 《Tetrahedron letters》2010,51(9):1333-1335
In this Letter we present a simple reaction pathway which allows the conversion of the glutamic acid residue of a tripeptide into a proline residue. The reaction was performed by using Boc-Val-Glu-Phe-NH2 as a starting material and is based on a NaH-induced intraresidue alkylation under reaction conditions analogous to that adopted during the Freidinger lactams formation. 相似文献