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51.
A long-standing open problem asks whether a Riemannian metric on the real projective space with the same volume as the canonical metric carries a periodic geodesic whose length is at most π. A contact-geometric reformulation of systolic geometry and the use of canonical perturbation theory allow us to solve a parametric version of this problem: if g s is a smooth, constant-volume deformation of the canonical metric that is not formally trivial, the length of the shortest periodic geodesic of the metric g s attains π as a strict local maximum at s = 0. This result still holds for complex and quaternionic projective spaces as well as for the Cayley plane. Moreover, the same techniques can be applied to show that Zoll Finsler manifolds are the unique smooth critical points of the systolic volume. Pour résoudre un problème nouveau, nous cherchons toujours à le simplifier par une série de transformations ; mais cette simplification a un terme, car il y a dans tout problème quelque chose d’essentiel, pour ainsi dire, que toute transformation est impuissante à modifier. Henri Poincaré 相似文献
52.
Raphael E. F. de Paiva Camilla Abbehausen Fernando R. G. Bergamini Andre L. Thompson Danilo A. Alves Marcelo Lancellotti Pedro P. Corbi 《Journal of inclusion phenomena and macrocyclic chemistry》2014,79(1-2):225-235
The present work describes the preparation and characterization of inclusion systems involving β-CD and the silver(I) nimesulide coordination complex (Ag-NMS), prepared by kneading (K) and co-evaporation (CE) methods. Solid state characterization by DSC, XRD and IR vibrational spectroscopic measurements provided remarkable evidences of the formation of true inclusion systems. Solution measurements provided information about the inclusion mode. The UV–Vis spectroscopy was used to obtain the association constants by the Scatchard method, and the value obtained was 370 ± 2 L mol?1. The 1H NMR spectroscopic measurements indicate a total inclusion of the guest into the cavity. A 2D NOESY experiment was carried out for the inclusion complex. The spectrum shows that hydrogens 3–6 of the cyclodextrin clearly correlate with the protons of the phenoxy ring of nimesulide in the Ag-NMS coordination compound, which confirms the formation of the inclusion complex. The antibacterial activities of the Ag-NMS and CE-[(Ag-NMS)·β-CD] inclusion system were evaluated by the well diffusion method over Escherichia coli and Pseudomonas aeruginosa (Gram-negative) and Staphylococcus aureus (Gram-positive) pathogenic bacterial strains. The observed data shows the significant antibacterial activity of the Ag-NMS coordination complex, and no activity for the inclusion complex under the same considered conditions. 相似文献
53.
This paper focuses on the deposition of silicon oxide thin films, using laser assisted CVD based on a CO2 laser, and on the feasibility of the process for coating porous silicon samples. Scanning electron and atomic force microscopy were used to analyse the morphology and microstructure of the films, while structure and chemical composition were determined by Fourier transform infrared and Rutherford backscattering spectroscopy. Two-wavelength ellipsometry was used for thickness and refractive index evaluation. The photoluminescence of SiO2/PS was measured and compared with that of uncoated samples. 相似文献
54.
Cunha AG Fernández-Lorente G Bevilaqua JV Destain J Paiva LM Freire DM Fernández-Lafuente R Guisán JM 《Applied biochemistry and biotechnology》2008,146(1-3):49-56
Lipase immobilization offers unique advantages in terms of better process control, enhanced stability, predictable decay rates
and improved economics. This work evaluated the immobilization of a highly active Yarrowia lipolytica lipase (YLL) by physical adsorption and covalent attachment. The enzyme was adsorbed on octyl–agarose and octadecyl–sepabeads
supports by hydrophobic adsorption at low ionic strength and on MANAE–agarose support by ionic adsorption. CNBr–agarose was
used as support for the covalent attachment immobilization. Immobilization yields of 71, 90 and 97% were obtained when Y. lipolytica lipase was immobilized into octyl–agarose, octadecyl–sepabeads and MANAE–agarose, respectively. However, the activity retention
was lower (34% for octyl–agarose, 50% for octadecyl–sepabeads and 61% for MANAE–agarose), indicating that the immobilized
lipase lost activity during immobilization procedures. Furthermore, immobilization by covalent attachment led to complete
enzyme inactivation. Thermal deactivation was studied at a temperature range from 25 to 45°C and pH varying from 5.0 to 9.0
and revealed that the hydrophobic adsorption on octadecyl–sepabeads produced an appreciable stabilization of the biocatalyst.
The octadecyl–sepabeads biocatalyst was almost tenfold more stable than free lipase, and its thermal deactivation profile
was also modified. On the other hand, the Y. lipolytica lipase immobilized on octyl–agarose and MANAE–agarose supports presented low stability, even less than the free enzyme. 相似文献
55.
Kézia Santana de Moura Hugo Rafael Chaves da Silva Leonardo Prezzi Dornelles Luana Cassandra Breitenbach Barroso Coelho Thiago Henrique Napoleão Maria Danielly Lima de Oliveira Patrícia Maria Guedes Paiva 《Applied biochemistry and biotechnology》2016,180(7):1361-1371
Moringa oleifera seeds contain a water-soluble lectin [water-soluble M. oleifera lectin (WSMoL)] that has shown coagulant activity. Magnesium ions are able to interfere with the ability of this lectin to bind carbohydrates. In this study, we performed structural characterization of WSMoL and analyzed its effect on the electrical resistance of a kaolin clay suspension in both presence and absence of monosaccharides (N-acetylglucosamine, glucose, or fructose) and magnesium ions. The coagulant activity of WSMoL was monitored by measuring optical density and electrical resistance over a period of 60 min. Native WSMoL had a molecular mass of 60 kDa and exhibited anionic nature (pI 5.5). In sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE), it appeared as three polypeptide bands of 30, 20, and 10 kDa. WSMoL reduced the optical density and electrical resistance of the kaolin suspension, which suggests that suspended particles are destabilized and that this is followed by formation of complexes. The coagulant activity of lectin decreased in the presence of Mg2+ ions and carbohydrates at concentrations that also inhibited hemagglutinating activity. This was most likely due to conformational changes in lectin structure. Our findings suggest that the coagulant activity of WSMoL is enhanced by lowering of electrical resistance of the medium and is impaired by lectin–carbohydrate and lectin–Mg2+ interactions. 相似文献
56.
Ana P. H. Rodrigues Iaci M. Pereira Sâmara D. de Souza Camila S. Brey Gil Giovanna Machado Sandhra M. Carvalho Fabiano V. Pereira Paulo R. P. Paiva Luiz C. A. de Oliveira Patrícia S. de O. Patricio 《Cellulose (London, England)》2017,24(4):1731-1744
Collagen is an important biomaterial because it has many applications in the biomedical sector. However, the high hydrophilicity of collagen (COL) leads to easy swelling. Thus, controlling this property is highly desirable. In this work, cellulose nanocrystals (CNCs) dispersed in glycerol (GLI) were incorporated in the matrix collagen to tailor the hydrophilicity and mechanical properties. Study of the hydrophilicity of the bio-based nanocomposite was evaluated by contact angle measurement and thermogravimetric analysis. Mechanical analyses showed that CNCs are excellent reinforcing fillers to the collagen matrix. Synchrotron small-angle X-ray scattering was employed to investigate the nanostructures of COL/GLI/CNC nanocomposites and CNC water dispersion. CNC in concentrations up to 1 wt% presents an intermediate shape between a rod and a plane with a 9.34-nm radius of gyration (R g). Bio-based nanocomposites present two different structural levels with two types of particles with very different R gs. At the intermediate power-law regime, a large-scale mass fractal aggregate is observed. In the high-power-law regime, it is observed scattering from primary particles smaller than 1 nm. As the CNC concentration increases, the original particle distorts from a rod to a plate. The cytotoxicity assay indicates that the collagen and nanocomposites did not affect the cell viability of rat calvarial cells in vitro. 相似文献
57.
58.
Gislaine Aparecida Honorato Ricardo Vieira de Lima Bhaskar Reddy Manda Derisvaldo Rosa Paiva Tairine Pimentel Roberto da Silva Gomes 《Tetrahedron letters》2017,58(23):2240-2243
The comparison in several reaction conditions for synthesis of nonracemic α-methylsulfinylation of 3,4-dihydronaphthalen-1(2H)-one was achieved. The sulfanylation reactions of 3,4-dihydronaphthalen-1(2H)-one-O-methyloxime and 2-(methylsulfinyl)-3,4-dihydronaphthalen-1(2H)-one-O-methyloxime by homogenous reaction medium are reported. The products were obtained in good yields and de. The yields, diastereoselectivity and theoretical calculations to all obtained compounds to support the experimental data are compared and discussed. 相似文献
59.
Andréa F. S. Santos Maria G. Carneiro-da-Cunha José A. Teixeira Patrícia M. G. Paiva Luana C. B. B. Coelho Regina Nogueira 《Chemical Papers》2011,65(4):406-411
The aim of this work was to characterise the affinity of protein preparations from Moringa oleifera seeds, specifically extract (seeds homogenised with 0.15 M NaCl), fraction (extract precipitated with 390 mg mL−1 of ammonium sulphate) and cMoL (coagulant M. oleifera lectin) to bind humic acids using a haemagglutinating activity assay with rabbit erythrocytes and a radial diffusion assay
in agarose gel. Specific haemagglutinating activity (SHA) decreased by 94 % for the extract and cMoL and by 50 % for the fraction
in the presence of humic acid. Precipitation bands were observed in the diffusion gel. Both results suggested humic acid-cMoL binding. Carbohydrates, potassium, and calcium ions and pH affected the SHA of cMoL. As an example of application, cMoL was immobilised on a column packed with sepharose receiving 20 mg mL−1 of carbon humic acid solution, 30 mg of humic acid per gram of support was removed. This result suggested that protein preparations
might be used in water treatment to remove humic acids. 相似文献
60.
Maria Inês Sucupira Maciel Maria do Socorro de Mendon?a Cavalcanti Thiago Henrique Napole?o Patrícia Maria Guedes Paiva Maria Teresa Jansem de Almeida Catanho Luana Cassandra Breitenbach Barroso Coelho 《Applied biochemistry and biotechnology》2012,168(3):580-591
Lectins, proteins that recognize carbohydrates, have been immobilized on inert supports and used in the screening or purification of glycoproteins. Anacardium occidentale bark infusion has been used as a hypoglycemic agent in Brazil. The toxicity of natural products may be evaluated determining their capability to alter the biodistribution of technetium-99M (99mTc). This work reports the isolation and characterization of a lectin from A. occidentale bark (AnocBL), its evaluation as an affinity support for glycoprotein isolation and lectin effect on the uptake of 99mTc by rat adipocytes. AnocBL was isolated from 80?% ammonium sulphate supernatant by affinity chromatography on fetuin?Cagarose. SDS?CPAGE showed a single protein band of 47?kDa. The monossacharide l-arabinose and the glycoproteins fetuin, asialofetuin, ovomucoid, casein, thyroglobulin, peroxidase, fetal bovine serum and IgG inhibited the activity. The lectin activity was stable until 70?°C and at a pH range of 3.0?C7.5. AnocBL?CSepharose column bound fetuin indicating that the lectin matrix may be used to obtain glycoconjugates of biotechnological interest. In vitro assay revealed that glucose and insulin increase 99mTc uptake by rat adipocytes. AnocBL decreases 99mTc uptake, and this effect was not detected in the presence of glucose. Fetuin inhibited AnocBL effect in all insulin concentrations. 相似文献