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51.
52.
de Souza NC Caetano W Itri R Rodrigues CA Oliveira ON Giacometti JA Ferreira M 《Journal of colloid and interface science》2006,297(2):546-553
The influence of small amounts of bovine serum albumin (BSA) (nM concentration) on the lateral organization of phospholipid monolayers at the air-water interface and transferred onto solid substrates as one-layer Langmuir-Blodgett (LB) films was investigated. The kinetics of adsorption of BSA onto the phospholipid monolayers was monitored with surface pressure isotherms in a Langmuir trough, for the zwitterionic dipalmitoylphosphatidyl ethanolamine (N,N-dimethyl-PE) and the anionic dimyristoylphosphatidic acid (DMPA). A monolayer of N,N-dimethyl-PE or DMPA incorporating BSA was transferred onto a solid substrate using the Langmuir-Blodgett technique. Atomic force microscopy (AFM) images of one-layer LB films displayed protein-phospholipid domains, whose morphology was characterized using dynamic scaling theories to calculate roughness exponents. For DMPA-BSA films the surface is characteristic of self-affine fractals, which may be described with the Kardar-Parisi-Zhang (KPZ) equation. On the other hand, for N,N-dimethyl-PE-BSA films, the results indicate a relatively flat surface within the globule. The height profile and the number and size of globules varied with the type of phospholipid. The overall results, from kinetics of adsorption on Langmuir monolayers and surface morphology in LB films, could be interpreted in terms of the higher affinity of BSA to the anionic DMPA than to the zwitterionic N,N-dimethyl-PE. Furthermore, the effects from such small amounts of BSA in the monolayer point to a cooperative response of DMPA and N,N-dimethyl-PE monolayers to the protein. 相似文献
53.
Marine mussels affix themselves to surfaces by use of a highly cross-linked, protein-based adhesive. Metal levels (e.g., Fe, Zn, Cu, Mn) of the cured glue are significantly concentrated relative to surrounding waters. Specific details on the reagents used by mussels to induce protein cross-linking are not known at this time. To provide insight on the cross-linking agents and reactions taking place while curing mussel glues, we performed a study in which various compounds were tested for the ability to bring about protein curing. A precursor to adhesion, with proteins containing the unusual amino acid 3,4-dihydroxyphenylalanine, was extracted from mussel feet. Potential cross-linking agents were mixed with this gelatinous pellet. The compressibility and shear properties of the resulting material were investigated by use of a penetration test. The reagents examined included simple metal ions (e.g., Na+, Zn2+), oxidizing transition metals (e.g., Fe3+, Cr2O7(2-)), nonmetallic oxidants (e.g., H2O2,IO4-), and oxidizing enzymes (e.g., tyrosinase). We found that protein curing was brought about by simple oxidants and transition metal ions. The results show that optimal curing occurs when the reagent is an oxidizing metal ion (e.g., MnO4-, Fe3+). We conclude that marine mussels are likely to employ Mn3+ and Fe3+ for protein cross-linking and adhesive synthesis. 相似文献
54.
Peter Wilker 《Mathematische Annalen》1960,139(5):433-445
Ohne Zusammenfassung 相似文献
55.
56.
J. B. Wilker 《Geometriae Dedicata》1989,32(2):203-209
While it is not possible to tile R
2 with circles, several constructions are known for tiling R
3 with circles or with homeomorphs of circles subject to various constraints. We extend this work on circles and obtain as well some analogous results on tiling R
2 and R
3 with disks. 相似文献
57.
Camila Fabiano de Freitas Diogo Silva Pellosi Bianca Martins Estevão Italo Rodrigo Calori Tayana Mazin Tsubone Mário José Politi Wilker Caetano Noboru Hioka 《Photochemistry and photobiology》2016,92(6):790-799
It was evaluated the properties of the xanthene dyes Erythrosin B, Eosin Y and theirs Methyl, Butyl and Decyl ester derivatives as possible photosensitizers (PS) for photodynamic treatments. The more hydrophobic dyes self‐aggregate in water/ethanol solutions above 70% water (vol/vol) in the mixture. In buffered water, these PS were encapsulated in Pluronic polymeric surfactants of P‐123 and F‐127 by two methodologies: direct addition and the thin‐film solid dispersion methods. The thin‐film solid method provided formulations with higher stabilities besides effective encapsulation of the PS as monomers. Size measurements demonstrated that Pluronic forms self‐assembled micelles with uniform size, which present slightly negative surface potential and a spherical form detected by TEM microscopy. The ester length modulates xanthene localization in the micelle, which is deeper with the increase in the alkyl chain. Moreover, some PS are distributed into two populations: one on the corona micelle interface shell (PEO layer) and the other into the core (PPO region). Although all PS formulations show high singlet oxygen quantum yield, promising results were obtained for Erythrosin B esters with the hydrophobic P‐123, which ensures their potential as drug for clinical photodynamic applications. 相似文献
58.
Chlorpromazine and sodium dodecyl sulfate mixed micelles investigated by small angle X-ray scattering 总被引:1,自引:0,他引:1
Small-angle X-ray scattering (SAXS) studies are reported on the interaction of chlorpromazine (CPZ) with micelles of anionic surfactant sodium dodecyl sulfate (SDS). Isotropic solutions of SDS (40 and 100 mM) at pH 4.0, 7.0, and 9.0 in the absence and presence of CPZ (2-25 mM) were investigated at the National Laboratory of Synchrotron Light (LNLS, Campinas, Brazil). The data were analyzed through the modeling of the micellar form factor and interference function. The results evidence a micellar shape transformation from prolate ellipsoid to cylinder accompanied by micellar growth and surface charge screening as the molar ratio CPZ : SDS increases in the complex. Small ellipsoids with axial ratio nu=1.5+/-0.1 at 40 mM SDS grow and reassemble into cylinder-like aggregates upon 5 mM drug incorporation (1 CPZ : 8 SDS monomers) with a decrease of the micelle surface charge. At 10 mM CPZ : 40 mM SDS cylindrical micelles are totally screened with an axial ratio nu approximately 2.5. The data also indicate the presence of small prolate ellipsoids (nu=1.7+/-0.1) in solutions of 100 mM SDS (no drug) and micellar growth (nu approximately 2.0 and 4.0) when 10 and 25 mM CPZ are added to the system. In the latter case, the aggregate is also better represented by a cylinder-like form. Therefore, our results demonstrate that the axial ratio and shape evolution of the surfactant : phenothiazine complex are both SDS concentration and drug : SDS molar ratio dependent. The drug location close to the SDS polar headgroup region without disrupting in a significant way both the paraffinic hydrophobic core and the polar shell thickness is inferred. SAXS data made it possible to obtain the shapes and dimensions of CPZ/SDS aggregates. 相似文献
59.
An investigation is made of the influence from small amounts of the protein bovine serum albumin (BSA) on the lateral organization of low molecular weight surfactant sodium bis-2-ethylhexyl sulfosuccinate (AOT) at the air-water interface. Surface pressure (pi - A), surface potential (deltaV - A) and Brewster angle microscopy (BAM) experiments were carried out, with particular emphasis on the monolayer stability under successive compression-expansion cycles. AOT monolayer is not stable at the air-water interface, which means that the majority of AOT molecules go into the aqueous subphase as monomers and/or normal micelles. When a waiting time elapses between spreading and compression, the surfactant monolayer tends to reorganize partially at the air-water interface, with a monolayer expansion being observed for waiting times as large as 12 h. The incorporation of very small amount of BSA (10(-9)M) at the interface, also inferred from BAM, increases the monolayer stability as revealed by pi - A and deltaV - A results. For a waiting time of circa 3 h, the mixed monolayer reaches its maximum stability. This must be related to protein (and/or protein-surfactant complexes) adsorbed onto the AOT monolayer, thus altering the BSA conformation to accommodate its hydrophobic/hydrophilic residues. Furthermore, the effects from such small amounts of BSA in the monolayer formation and stabilization mean that the AOT monolayer responds cooperatively to BSA. 相似文献
60.
In the view-obstruction problem, congruent, closed, convex bodies centred at the points
in
n
are expanded uniformly until they block all rays from the origin into the open positive cone. The central problem is to determine the minimal blocking size. In the case of spheres of diameter 1, this value is denoted byv(n) and is known for dimensionsn=2,3. Here we show that
and obtain a Markoff type chain of isolated extreme values. 相似文献