Biomineralization in diatoms: the role of silacidins

Diatoms are eukaryotic, unicellular algae encased within siliceous cell walls (frustules), which are precisely reproduced generation by generation. The production of this nanostructured silica is under genetic control and the isolation of specific gene products (the proteins silaffins, silacidins) guiding the biomineralization processes, and which are necessary to produce the frustules, has already been described. Under silicon starvation, the amount of silacidins present in the cell walls of Thalassiosira pseudonana increases relative to other proteins. Natsilacidins, the native and highly phosphorylated silacidins are enormously effective in silica precipitation whereas silacidin A', the nonphosphorylated form, is not. This indicates an important role for natsilacidins in the survival of diatoms under silicic acid depleted conditions.     

Lipid Droplet Biosynthesis Impairment through DGAT2 Inhibition Sensitizes MCF7 Breast Cancer Cells to Radiation

Breast cancer is the most frequent cancer in women worldwide and late diagnosis often adversely affects the prognosis of the disease. Radiotherapy is commonly used to treat breast cancer, reducing the risk of recurrence after surgery. However, the eradication of radioresistant cancer cells, including cancer stem cells, remains the main challenge of radiotherapy. Recently, lipid droplets (LDs) have been proposed as functional markers of cancer stem cells, also being involved in increased cell tumorigenicity. LD biogenesis is a multistep process requiring various enzymes, including Diacylglycerol acyltransferase 2 (DGAT2). In this context, we evaluated the effect of PF-06424439, a selective DGAT2 inhibitor, on MCF7 breast cancer cells exposed to X-rays. Our results demonstrated that 72 h of PF-06424439 treatment reduced LD content and inhibited cell migration, without affecting cell proliferation. Interestingly, PF-06424439 pre-treatment followed by radiation was able to enhance radiosensitivity of MCF7 cells. In addition, the combined treatment negatively interfered with lipid metabolism-related genes, as well as with EMT gene expression, and modulated the expression of typical markers associated with the CSC-like phenotype. These findings suggest that PF-06424439 pre-treatment coupled to X-ray exposure might potentiate breast cancer cell radiosensitivity and potentially improve the radiotherapy effectiveness.     

Chemotactic and Angiogenic Potential of Mineralized Collagen Scaffolds Functionalized with Naturally Occurring Bioactive Factor Mixtures to Stimulate Bone Regeneration

To develop cost-effective and efficient bone substitutes for improved regeneration of bone defects, heparin-modified mineralized collagen scaffolds were functionalized with concentrated, naturally occurring bioactive factor mixtures derived from adipose tissue, platelet-rich plasma and conditioned medium from a hypoxia-treated human bone marrow-derived mesenchymal stem cell line. Besides the analysis of the release kinetics of functionalized scaffolds, the bioactivity of the released bioactive factors was tested with regard to chemotaxis and angiogenic tube formation. Additionally, functionalized scaffolds were seeded with human bone marrow-derived mesenchymal stromal cells (hBM-MSC) and their osteogenic and angiogenic potential was investigated. The release of bioactive factors from the scaffolds was highest within the first 3 days. Bioactivity of the released factors could be confirmed for all bioactive factor mixtures by successful chemoattraction of hBM-MSC in a transwell assay as well as by the formation of prevascular structures in a 2D co-culture system of hBM-MSC and human umbilical vein endothelial cells. The cells seeded directly onto the functionalized scaffolds were able to express osteogenic markers and form tubular networks. In conclusion, heparin-modified mineralized collagen scaffolds could be successfully functionalized with naturally occurring bioactive factor mixtures promoting cell migration and vascularization.     

Destabilization of model silica dispersions by polyelectrolyte complex particles with different charge excess,hydrophobicity, and particle size

Nonstoichiometric polyelectrolyte complex dispersions (PECs) with different charge excess and hydrophobicity as well as different average hydrodynamic particle size were used to induce flocculation of oppositely charged silica dispersions. PECs were formed with poly(diallyldimethylammonium chloride) (PD) as polycation and poly(styrene‐p‐sodium sulfonate) (NaPSS) and poly(acrylamide‐co‐sodium acrylate) (PR2540) as polyanions. PD was used as single polymer flocculant too. Flocculation process was characterized by optical densities of supernatants OD₅₀₀, by UV/VIS spectrometry, and determination of average floc sizes D(v; 0.5) as well as volume distribution of floc sizes by laser diffraction and determination of sedimentation velocity s by means of LUMiFuge? 114. It was found that the reaction process between silica and the used flocculants could be divided into three intervals (destabilization, flocculation optimum, and restabilization) as it is known for all other polymer flocculants. For an effective flocculation of a charged substrate, both electrostatic as well as hydrophobic interactions play an important role. The interval up to the beginning of the flocculation optimum is mainly ascertained by electrostatic interactions (the charge density of the flocculant) but the broadness of flocculation optimum depends largely on hydrophobic interactions. Hydrophobic interactions also play an important role for shear stability of the formed flocs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3776–3784, 2007     

Optical properties and appearance characteristics of tomato fruit (Lycopersicon esculentum)

Characterisation of the optical properties of the internal structures of tomatoes enhances assessment of the composite appearance. Reflectance colorimetry and the Kubelka-Munk analysis to distinguish three distinct maturity groups of tomatoes were tested. Differences in the scatter, absorption and internal transmittance were found amongst the component structures of the intact tomato. Tomato fruit was also pulped and a range of dilutions prepared. The decrease in scatter, absorption and increase in internal transmittance with increased dilution suggests the importance of optical properties with changes in concentration.     

Cranberry proanthocyanidins associate with low‐density lipoprotein and inhibit in vitro Cu2+‐induced oxidation

Antioxidant activity of six fractions of cranberry phenolic compounds was determined by inhibition of Cu²⁺‐induced low‐density lipoprotein (LDL) oxidation. The phenolic composition of each fraction was determined by high‐performance liquid chromatography. The phenolic fractions were mixed with aliquots of modified human serum prior to LDL isolation. The serum was modified to remove very‐low‐density lipoprotein and chylomicrons that may bind phenolic compounds. Only fractions 5 and 6 that contained proanthocyanidins (PAs) significantly increased the lag time of LDL oxidation, and the lag time for fraction 6 was significantly higher than for fraction 5. The mass distribution of PAs in these fractions was obtained by matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry, a technique that allows rapid characterisation of the molecular weight distribution in mixtures of oligomeric compounds. Fraction 5 contained trimers through heptamers, whereas fraction 6 contained pentamers through nonamers. In addition, fraction 6 contained PA oligomers with more doubly linked, A‐type interflavan bonds. Results indicate that PAs specifically associate with LDL in modified serum and increase the lag time of Cu²⁺‐induced oxidation. Differences between fractions 5 and 6 in PA structure and effects on LDL oxidation suggest that the degree of polymerisation and the nature of the interflavan bond influence antioxidant properties. © 2001 Society of Chemical Industry     

Designing trust: how strategic intermediaries choreograph homeowners’ low-carbon retrofit experience

ABSTRACT

In the Netherlands, as in other European countries, the uncertain, fragmented character of the low-carbon retrofit market hampers a transition towards sustainable housing. Connecting homeowners to supply-side actors of low-carbon retrofit procedures, products and technologies in ways satisfactory to homeowners forms an important, challenging task. Service design for the benefit of a customer-centric perspective might be a solution. This paper investigates the potential role of strategic intermediaries as agents of change located between supply-side actors and homeowners. It asks how strategic intermediaries choreograph low-carbon retrofit experiences of homeowners through the design of a ‘customer journey’. Trust is a crucial determinant. This paper distinguishes between three customer-journey designs in which, depending on the role envisioned for homeowners, a different trust relation is foregrounded: a private design envisions homeowners as passive consumers who trust in the expertise offered by the intermediary; a civic design envisions homeowners as engaged consumer-citizens who trust their neighbours as reliable service representatives; and a public design envisions homeowners as critical customers who trust in the retrofit technologies and products offered. This implies an important role for policy actors in realizing ways for scaling up and institutionalizing all three low-carbon retrofit customer-journey designs on a national level.     

Monitoring the stability of nanosized silica dispersions in presence of polycations by a novel centrifugal sedimentation method

The stability of Aerosil‐silica dispersions is analyzed in dependence on the addition of polycations with different charge density and hydrophobic modification using the analytical centrifuge LUMiSizer. This novel centrifugal sedimentation method allows the direct calculation of the stability parameters like sedimentation velocity and prediction of the shelf life. The highly charged polycation poly (diallyl‐dimethylammonium chloride) (PDADMAC) is compared with tailored cationic polyelectrolytes of equal degree of polymerization but lower and different charge density as well as various hydrophobic substitutions. The used technique allows to accelerate demixing and to quantify the stability of dispersions in a direct way. All polymers under study are able to stabilize aerosil dispersions, but the shelf life strongly depends on the polymer concentration. Typically for polycations, the stability increases with the polymer concentration whereas at low‐polymer content flocculation can be detected. In this context, the behavior of PDADMAC and three cationic PVB derivatives is similar, but, whereas the stability of PDADMAC containing dispersions decreases at higher polymer concentrations, PVB derivatives are effective stabilizers at higher concentrations too. The highest increase of the stability with increasing polymer concentration is obtained with the ampholytic terpolymer TP that has the lowest cationic charge. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009