The swelling of wood upon impregnation by aqueous solutions of organic solvents is larger than swelling by pure water. This phenomenon, described as “hyperswelling”, results from specific ...interactions with components of the complex wood microstructure. To understand the combined effect of mixed solvents on wood properties, the specific influence of each solvent on wood biopolymers and structure must be first characterized. In this study, the effect of the impregnation of aqueous solutions of ethanol with concentrations from 0 to 100% on the physico-mechanical properties of poplar wood was investigated. For each solution, the sorption behaviour of veneer sapwood samples and the effect of sorption on wood viscoelasticity and microstructure were measured through vapour sorption gravimetry, dynamic mechanical analysis and optical microscopy monitoring. Pure water and pure ethanol showed contrasting sorption behaviour, ethanol leading to a much lower swelling and a very limited softening compared to water, despite comparable sorbed amounts. This result suggests different affinities of water and ethanol for biopolymers within wood microstructure. With mixed solutions, larger swelling and stronger variations in viscoelastic behaviour than in pure solvents were observed, confirming the synergistic effect of water/ethanol mixtures on structure and properties of wood cells. Microscopic observations evidenced that ethanol, both alone and in aqueous solutions, generates intercellular decohesion and disbonding of the different wood cell wall layers. These observations are consistent with a mechanism of partial solubilization by ethanol of lignin-related phenolic. This could lead to a release of the constraints which limit the swelling of the polysaccharide fraction of the cell wall by water. Such phenomenon is likely to be at the origin of the hyperswelling observed in mixed water/organic solvent systems.
Mixed-micelles of long-chain phosphatidylcholine and surfactants are of considerable scientific and biomedical interest. Lecithins are natural phospholipids from egg or soybean. Lecithin/dodecylamine ...mixed-micelles in an alcoholic/aqueous media allow to template the formation of sponge mesoporous silica (SMS) materials through a self-assembly process between mixed-micelles and tetraethoxysilane (TEOS). SMS synthesis adds a porosity control to the classical sol–gel synthesis used for enzymes encapsulation. We are reporting here the key parameters of SMS synthesis procedure (amount of amine, TEOS, ethanol, water, lecithin nature, salt addition, etc.), as well as a fine description of SMS structure by TEM. SMS features an isotropic 3-dimensional (3-D) pore structure similarly to SBA-16, but with a lower degree of mesoscopic structural order. Its porosity results from cavities and connecting channels, whose length is controlled by the synthesis conditions. Cavity diameters can reach 4.7
nm in accordance to the lecithin maximum alkyl chain length. Surface areas range from 300 to 800
m
2/g, and pore volumes from 0.30 to 0.85
mL/g. The use of lactose as an enzyme stabilizing agent does not change the pore structure of SMS. A very fragile enzyme, alcohol dehydrogenase, has been successfully encapsulated by this way, providing the first example of successful entrapment of this enzyme in an inorganic matrix. SMS encapsulation procedure is biomolecules friendly and opens a bright perspective for biomolecules processing for biocatalysis, biosensors or biofuel cell applications.
Sperm protein 17 (Sp17) was originally identified in the flagellum of spermatozoa and subsequently included in the subfamily of tumor-associated antigens known as cancer-testes antigens (CTA). Sp17 ...has been associated with the motility and migratory capacity in tumor cells, representing a link between gene expression patterns in germinal and tumor cells of different histological origins. Here we review the relevance of Sp17 expression in the mouse embryo and cancerous tissues, and present additional data demonstrating Sp17 complex expression pattern in this murine model. The expression of Sp17 in embryonic as well as adult neoplastic cells, but not normal tissues, suggests this protein should be considered an "oncofetal antigen." Further investigations are necessary to elucidate the mechanisms and functional significance of Sp17 aberrant expression in human adult cells and its implication in the pathobiology of cancer.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
SAXS patterns of a Ca-alginate hydrogel and of the derived alcogel and aerogel have been recorded. All patterns correspond to disordered arrays of rod-like fibrils. The calculated size of the fibrils ...of the aerogel, 8 nm, is in good agreement with the results of scanning electron microscopy and N₂ adsorption. The results suggest that ethanol exchange and CO₂ supercritical drying do not affect the spatial organisation of the secondary structures of the gel and that characterisations of the aerogel can provide information on the organisation of the parent hydrogel.
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► Silver oxide germs formed in situ are effective seeds for zeolite crystallisation. ► Seeded heterogeneous nucleation allows to control zeolite crystal size. ► Crystal size of ...zeolites as different as LSX and beta can be controlled.
The size of zeolite crystals can be controlled by modifying the nucleation frequency by the addition of silver-based promoters. Nanoparticles of silver oxide can be formed in the alkaline solutions used in zeolite synthesis and can act as effective heterogeneous nuclei for the crystallization of zeolites in a wide range of topology and composition (zeolites LSX, X, Y, A, L, and beta). The presence of silver oxide does not affect the normal nucleation mechanism of zeolites from gels and provides a number of additional seeds proportional to the amount of silver oxide precursors introduced in the synthesis systems. The yield of zeolite crystallization is not significantly affected by the presence of the nucleation promoters. The volume of the crystals formed can be decreased by a factor 20 in the appropriate conditions. The effectiveness of the nucleation promotion is not affected by the presence of organic cations but is largely reduced in extremely alkaline media, in which silver oxides are significantly soluble.
Hepatocyte Growth Factor (HGF, also known as Scatter Factor) is a powerful mitogen or motility factor in different cells, acting through the tyrosine kinase receptor encoded by the MET protooncogene. ...Endothelial cells express the MET gene and expose at the cell surface the mature protein ( p190 MET) made of a 50 kD (α) subunit disulfide linked to a 145-kD (β) subunit. HGF binding to endothelial cells identifies two sites with different affinities. The higher affinity binding site (K d=0.35 nM) corresponds to the p190 MET receptor. Sub-nanomolar concentrations of HGF, but not of a recombinant inactive precursor, stimulate the receptor kinase activity, cell proliferation and motility. HGF induces repairs of a wound in endothelial cell monolayer. HGF stimulates the scatter of endothelial cells grown on three-dimensional collagen gels, inducing an elongated phenotype. In the rabbit cornea, highly purified HGF promotes neovascularization at sub-nanomolar concentrations. HGF lacks activities related to hemostasis-thrombosis, inflammation and endothelial cells accessory functions. These data show that HGF is an in vivo potent angiogenic factor and in vitro induces endothelial cells to proliferate and migrate.
The small heat‐shock protein of 27 kDa (HSP27) is highly expressed in many cancers and is associated with aggressive tumour behaviour, metastasis, poor prognosis and resistance to chemotherapy. We ...aimed at assessing the role of HSP27 in modulating responses to target therapies. We selected several oncogene‐addicted cancer cell lines, which undergo either cell cycle blockade or cell death in response to agents that target the specific oncogene. Surprisingly, HSP27 suppression alone resulted in the apoptotic death of MET‐addicted EBC‐1 lung cancer cells, epidermal growth factor receptor (EGFR)‐addicted colorectal carcinoma (CRC) DiFi cells and BRAF‐addicted CRC COLO205 and OXCO‐1 and melanoma COLO741 cells, all of which also undergo death when treated with the specific targeted agent. In other cell lines, such as MET‐addicted gastric carcinoma MKN45 and EGFR‐addicted CRC SW48 lines, where oncogene inhibition only blocked proliferation, HSP27 knockdown made targeted agents switch from cytostatic to cytotoxic activity. Mechanistically, the more the cells were susceptible to HSP27 suppression, the more they were primed for death, as demonstrated by increased levels of mitochondrial outer membrane permeabilization. Priming for death was accompanied by the increase in pro‐apoptotic proteins of the BCL2 family and of active caspase‐3 and lamin B. Together, these data suggest that oncogene‐addicted cells require HSP27 for survival and that HSP27 might interfere with the effectiveness of targeted agents.
Knockdown of the small heat‐shock protein HSP27 triggers apoptosis in cancer cells with oncogene overactivation and converts cytostatic targeted agents into fully cytotoxic drugs. HSP27 suppression results in increased mitochondrial membrane permeabilization due to modulation of BCL2 proteins and primes cells for apoptosis. Thus, increased expression of HSP27 in cancer might interfere with the effectiveness of targeted therapies.
The direct synthesis of a mesostructured silica with a tridimensional mesopore network with micrometer-sized and -shaped particles control is reported for the first time. Micrometer-sized beads of ...the cubic silica mesostructure MCM-48 have been obtained through a MCM-41 pseudomorphic synthesis procedure using preformed porous silica particles as silica source combined with a MCM-41/-48 phase transition. The low degree of polymerization of the MCM-41 formed in high alkaline conditions allows the further MCM-41/-48 phase transition. The kinetics of MCM-48 formation depends on the surface area of the parent silica, indicating that the dissolution of the silica in a confined environment is the rate-determining step of the process. The reaction time required to produce MCM-48 decreases from 7 to 2 h when the surface area of the parent silica increases from 160 to 740 m2/g. The MCM-48 mesostructure is metastable toward a lamellar mesostructure at longer synthesis times (>20 h). The domain of existence of the different mesostructures as a function of synthesis time and surface area of the parent silica sources has been established. The aggregation state of the MCM-48 particles can be controlled by adjusting the dilution and the alkalinity of the synthesis medium.
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