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411.
Helane?MS?Costa Augusto?CV?Freitas Júnior Ian?PG?Amaral Izaura?Y?Hirata Patrícia?MG?Paiva Luiz?B?CarvalhoJr Vitor?Oliveira Ranilson?S?BezerraEmail author 《Chemistry Central journal》2013,7(1):166
Background
Over the past decades, the economic development and world population growth has led to increased for food demand. Increasing the fish production is considered one of the alternatives to meet the increased food demand, but the processing of fish leads to by-products such as skin, bones and viscera, a source of environmental contamination. Fish viscera have been reported as an important source of digestive proteases with interesting characteristics for biotechnological processes. Thus, the aim of this study was to purify and to characterize a trypsin from the processing by-products of crevalle jack (Caranx hippos) fish.Results
A 27.5 kDa trypsin with N-terminal amino acid sequence IVGGFECTPHVFAYQ was easily purified from the pyloric caeca of the crevalle jack. Its physicochemical and kinetic properties were evaluated using N-α-benzoyl-DL-arginine-p-nitroanilide (BApNA) as substrate. In addition, the effects of various metal ions and specific protease inhibitors on trypsin activity were determined. Optimum pH and temperature were 8.0 and 50°C, respectively. After incubation at 50°C for 30 min the enzyme lost only 20% of its activity. K m , kcat, and k cat /K m values using BApNA as substrate were 0.689 mM, 6.9 s-1, and 10 s-1 mM-1, respectively. High inhibition of trypsin activity was observed after incubation with Cd2+, Al3+, Zn2+, Cu2+, Pb2+, and Hg2+ at 1 mM, revealing high sensitivity of the enzyme to metal ions.Conclusions
Extraction of a thermostable trypsin from by-products of the fishery industry confirms the potential of these materials as an alternative source of these biomolecules. Furthermore, the results suggest that this trypsin-like enzyme presents interesting biotechnological properties for industrial applications.412.
413.
Rojas EC Staton JA John VT Papadopoulos KD 《Langmuir : the ACS journal of surfaces and colloids》2008,24(14):7154-7160
A model water-in-oil-in-water (W1/O/W2) double emulsion was prepared by a two-step emulsification procedure and subsequently subjected to temperature changes that caused the oil phase to freeze and thaw while the two aqueous phases remained liquid. Our previous work on individual double-emulsion globules1 demonstrated that crystallizing the oil phase (O) preserves stability, while subsequent thawing triggers coalescence of the droplets of the internal aqueous phase (W1) with the external aqueous phase (W2), termed external coalescence. Activation of this instability mechanism led to instant release of fluorescently tagged bovine serum albumin (fluorescein isothiocyanate (FITC)-BSA) from the W 1 droplets and into W2. These results motivated us to apply the proposed temperature-induced globule-breakage mechanism to bulk double emulsions. As expected, no phase separation of the emulsion occurred if stored at temperatures below 18 degrees C (freezing point of the model oil n-hexadecane), whereas oil thawing readily caused instability. Crucial variables were identified during experimentation, and found to greatly influence the behavior of bulk double emulsions following freeze-thaw cycling. Adjustment of these variables accounted for a more efficient release of the encapsulated protein. 相似文献
414.
415.
Emmanuel N. Koukaras Aristides D. Zdetsis Panaghiotis Karamanis Claude Pouchan Aggelos Avramopoulos Manthos G. Papadopoulos 《Journal of computational chemistry》2012,33(10):1068-1079
It is shown by density functional theory calculations that high symmetry silicon cages can be designed by coating with Li atoms. The resulting highly symmetric lithiated silicon cages (up to D5d symmetry) are low‐lying true minima of the energy hypersurface with binding energies of the order of 4.6 eV per Si atom and moderate highest occupied molecular orbital–lowest unoccupied molecular orbital gaps. Moreover, relying on a systematic study of the electric response properties obtained by ab initio (Hartree–Fock, MP2, and configuration interaction singles (CIS)) and density functional (B3LYP, B2PLYP, and CAM‐B3LYP) methods, it is shown that lithium coating has a large impact on the magnitude of their second hyperpolarizabilities resulting to highly hyperpolarizable species. Such hyperpolarizable character is directly connected to the increase in the density of the low‐lying excited states triggered by the interaction between the Si cage and the surrounding Li atoms. © 2012 Wiley Periodicals, Inc. 相似文献
416.
Christos D. Papadopoulos Stavroula Skoulika Antonios G. Hatzidimitriou Prof. Dr. Maria Lalia‐Kantouri 《无机化学与普通化学杂志》2012,638(14):2273-2279
The reaction of a lanthanide(III) nitrate (Ln = Pr, Nd) with the base 2, 2′‐dipyridylamine (dpamH) afforded two very stable microcrystalline compounds. These compounds were characterized as complex salts with the general formula [Ln(NO3)6] · 3[dpamH‐H+] · H2O, where the dpamH ligand is not coordinated, but exists in its protonated form serving as counterion (dipyridylammonium cation), as it was revealed by single‐crystal X‐ray diffraction studies. Each one of the nitrate ions is coordinated, however, in a bidentate manner with the lanthanide(III) ion, which obtains coordination number twelve. All organic dpamH‐H+ cations are arranged in two columns parallel to the a axis of the cell forming pairs of almost parallel cationic molecules at a distance of about 3.5 Å. Inside each pair the molecules interact by strong π–π interactions. The water molecules, arranged between the inorganic anions [Ln(NO3)6]3–, bridge them by strong hydrogen bonds, involving the water proton and one nitrate oxygen. The lattice can be described as made from successive organic and inorganic alternating parallel columns interacting between them with strong hydrogen bonds. The thermal stability and decomposition mode of the two lanthanide compounds were studied by the simultaneous TG/DTG‐DTA technique and compared with the starting hexahydrate lanthanide(III) salts and the dipyridylamine. 相似文献
417.
Local search and constraint programming for the post enrolment-based course timetabling problem 总被引:1,自引:0,他引:1
Hadrien Cambazard Emmanuel Hebrard Barry O’Sullivan Alexandre Papadopoulos 《Annals of Operations Research》2012,194(1):111-135
We present a variety of approaches for solving the post enrolment-based course timetabling problem, which was proposed as
Track 2 of the 2007 International Timetabling Competition. We approach the problem using local search and constraint programming
techniques. We show how to take advantage of a list-colouring relaxation of the problem. Our local search approach won Track
2 of the 2007 competition. Our best constraint programming approach uses an original problem decomposition. Incorporating
this into a large neighbourhood search scheme seems promising, and provides motivation for studying complete approaches in
further detail. 相似文献
418.
Apostolos Kuiroukidis Demetrios B. Papadopoulos 《International Journal of Theoretical Physics》2006,45(1):64-78
We consider brane cosmologies within the context of five-dimensional effective actions with higher curvature corrections. The actions are compatible with bulk string amplitude calculations from heterotic string theory. We find wrapped solutions that satisfy the field equations in an approximate but acceptable manner given their complexity, where the internal, four-dimensional, scale factor is naturally inflating, having an exponential De-Sitter form. The temporal dependence of the metric components is nontrivial so that this metric cannot be factored as in a conformally flat case. The effective Planck mass is finite and the brane solutions can localize four-dimensional gravity while the four-dimensional gravitational constant varies with time. The Hubble constant can be freely specified through the initial value of the scalar field, to conform with recent data. 相似文献
419.
A correlation between the monomeric volume and the dynamic quantity E*(V)/H*, used to provide a quantitative measure of the role of temperature and density on the dynamics, is demonstrated for a series of polymers and glass-forming liquids. We show that monomeric volume and local packing play a key role in controlling the value of this ratio and thus the dynamics associated with the glass temperature. 相似文献
420.
Dionysia Papagiannopoulou George Makris Charalambos Tsoukalas Catherine P. Raptopoulou Aris Terzis Maria Pelecanou Ioannis Pirmettis Minas S. Papadopoulos 《Polyhedron》2010
The synthesis and structural characterization of the neutral rhenium complex fac-[Re(NSO)(CO)3], Re-1, where (NSO) is a tridentate bifunctional chelating agent, 3-(carboxymethylthio)-3-(1H-imidazol-4-yl)propanoic acid (1), is presented. The complex crystallized from methanol–water and its structure was assigned by IR and 1H, 13C NMR spectroscopies and X-ray crystallography. Furthermore, the analogous technetium complex fac-[99mTc(NSO)(CO)3], 99mTc-1, was synthesized in high yield by reacting ligand 1 with the fac-[99mTc(OH2)3(CO)3]+ precursor for 30 min at 85 °C. The tracer complex was found to be more than 95% stable in the L-histidine challenge experiment. Our data indicate that the bifunctional NSO chelating agent 1 can be successfully applied for the development of potential 99mTc-radiopharmaceuticals. 相似文献