Cell shape recognition by colloidal cell imprints: Energy of the cell-imprint interaction

The results presented in this study are aimed at the theoretical estimate of the interactions between a spherical microbial cell and the colloidal cell imprints in terms of the Derjaguin, Landau, Vervey, and Overbeek (DLVO) surface forces. We adapted the Derjaguin approximation to take into account the geometry factor in the colloidal interaction between a spherical target particle and a hemispherical shell at two different orientations with respect to each other. We took into account only classical DLVO surface forces, i.e., the van der Waals and the electric double layer forces, in the interaction of a spherical target cell and a hemispherical shell as a function of their size ratio, mutual orientation, distance between their surfaces, their respective surface potentials, and the ionic strength of the aqueous solution. We found that the calculated interaction energies are several orders higher when match and recognition between the target cell and the target cell imprint is achieved. Our analysis revealed that the recognition effect of the hemispherical shell towards the target microsphere comes from the greatly increased surface contact area when a full match of their size and shape is produced. When the interaction between the surfaces of the hemishell and the target cell is attractive, the recognition greatly amplifies the attraction and this increases the likelihood of them to bind strongly. However, if the surface interaction between the cell and the imprint is repulsive, the shape and size match makes this interaction even more repulsive and thus decreases the likelihood of binding. These results show that the surface chemistry of the target cells and their colloidal imprints is very important in controlling the outcome of the interaction, while the shape recognition only amplifies the interaction. In the case of nonmonotonous surface-to-surface interaction we discovered some interesting interplay between the effects of shape match and surface chemistry which is discussed in the paper. The results from this study establish the theoretical basis of cell shape recognition by colloidal cell imprints which, combined with cell killing strategies, could lead to an alternative class of cell shape selective antimicrobials, antiviral, and potentially anticancer therapies

An ultra melt-resistant hydrogel from food grade carbohydrates

© 2017 The Royal Society of Chemistry. We report a binary hydrogel system made from two food grade biopolymers, agar and methylcellulose (agar-MC), which does not require addition of salt for gelation to occur and has very unusual rheological and thermal properties. It is found that the storage modulus of the agar-MC hydrogel far exceeds those of hydrogels from the individual components. In addition, the agar-MC hydrogel has enhanced mechanical properties over the temperature range 25-85 °C and a maximum storage modulus at 55 °C when the concentration of methylcellulose was 0.75% w/v or higher. This is explained by a sol-gel phase transition of the methylcellulose upon heating as supported by differential scanning calorimetry (DSC) measurements. Above the melting point of agar, the storage modulus of agar-MC hydrogel decreases but is still an elastic hydrogel with mechanical properties dominated by the MC gelation. By varying the mixing ratio of the two polymers, agar and MC, it was possible to engineer a food grade hydrogel of controlled mechanical properties and thermal response. SEM imaging of flash-frozen and freeze-dried samples revealed that the agar-MC hydrogel contains two different types of heterogeneous regions of distinct microstructures. The latter was also tested for its stability towards heat treatment which showed that upon heating to temperatures above 120 °C its structure was retained without melting. The produced highly thermally stable hydrogel shows melt resistance which may find application in high temperature food processing and materials templating

Fabrication of living soft matter by symbiotic growth of unicellular microorganisms

We report the fabrication of living soft matter made as a result of the symbiotic relationship of two unicellular microorganisms. The material is composed of bacterial cellulose produced in situ by acetobacter (Acetobacter aceti NCIMB 8132) in the presence of photosynthetic microalgae (Chlamydomonas reinhardtii cc-124), which integrates into a symbiotic consortium and gets embedded in the produced cellulose composite. The same concept of growing living materials can be applied to other symbiotic microorganism pairs similar to the combination of algae and fungi in lichens, which is widespread in Nature. We demonstrate the in situ growth and immobilisation of the C. reinhardtii cells in the bacterial cellulose matrix produced by the simultaneous growth of acetobacter. The effect of the growth media composition on the produced living materials was investigated. The microstructure and the morphology of the produced living biomaterials were dependent on the shape of the growth culture container and media stirring conditions, which control the access to oxygen. As the photosynthetic C. reinhardtii cells remain viable and produce oxygen as they spontaneously integrate into the matrix of the bacterial cellulose generated by the acetobacter, such living materials have the potential for various applications in bio-hydrogen generation from the immobilised microalgae. The proposed approach for building living soft matter can provide new ways of immobilising other commercially important microorganisms in a bacterial cellulose matrix as a result of symbiosis with acetobacter without the use of synthetic binding agents and in turn increase their production efficiency

Fabrication of salt–hydrogel marbles and hollow-shell microcapsules by an aerosol gelation technique

We designed a new method for preparation of liquid marbles by using hydrophilic particles. Salt–hydrogel marbles were prepared by atomising droplets of hydrogel solution in a cold air column followed by rolling of the collected hydrogel microbeads in a bed of micrometre sized salt particles. Evaporation of the water from the resulting salt marbles with a hydrogel core yielded hollow-shell salt microcapsules. The method is not limited to hydrophilic particles and could potentially be also applied to particles of other materials, such as graphite, carbon black, silica and others. The structure and morphology of the salt–hydrogel marbles were analysed by SEM and their particle size distributions were measured. We also tested the dissolution times of the dried salt marbles and compared them with those of table salt samples under the same conditions. The high accessible surface area of the shell of salt microcrystals allows a faster initial release of salt from the hollow-shell salt capsules upon their dissolution in water than from the same amount of table salt. The results suggest that such hollow-shell particles could find applications as a table salt substitute in dry food products and salt seasoning formulations with reduced salt content without the loss of saltiness

Effects of the walnut Plukenetia conophora shell in the diet on the growth performance and genotoxicity of the African catfish Clarias gariepinus

Aquaculture industry is facing challenges of the high cost of fish feed, and therefore it is very crucial to explore the alternative raw materials for feed formulation at the lowest cost. Therefore, the objective of the present study was to evaluate the effect of Plukenetia conophora shells on the growth, haematological and biochemical parameters, and its genotoxicity on African catfish Clarias gariepinus juveniles. Five experimental diets were formulated having three replicates at 0% (0WS), 25% (25WS), 50% (50WS), 75% (75WS) and 100% (100WS) inclusion of walnut shell respectively. The fishes were fed on experimental diet two time a day for 12 weeks. The results showed that the fish in tank 25WS had the best weight gain with the mean of 33.5±5.8 g and the least was recorded in tank 100WS. The specific growth rate was highest in-tank 75WS with the mean value of 0.46±0.05 g was recorded. The highest feed intake was found in fish fed with 25% inclusion of P. conophora.  The fish fed with P. conophorashowed increased values of haemoglobin, (12.05±1.63g/dL), Red blood cell, (2.785±0.28µL) and White blood cell, (11.25±4.59µL) compared with control diet values of fish fed of  Red blood cell, (1.81±1.54µL) and White blood cell, (5.15±6.57µL). There was a reduction in the haematological value of the fish fed with control feed having Haemoglobin, (10.75±8.13g/dL). The genotoxicity test that was carried out showed that the highest counts of micronucleus were in tank 75WS. The Duncan Multiple Range Test (DMRT) shows a significant difference (p0.05) in the growth performance of the fish. It is concluded that inclusion of 50% P. conophora shells in the feed of C. gariepinus gave no negative impact on the health status  and growth performance of the fish.  Keywords: Toxicity test, Growth indices, Plukenetia conophora, Clarias gariepinus 

Olovo i kadmij u cigaretama i dimnom kondenzatu

The cigarettes of three commercial brands (belonging to JUS quality classes E, II and IV) were analysed for cadmium and lead in tobacco, butts and crude smoke condensate. Metal fractions transferred from the cigarette tobacco to the smoke as well as metal retentions in the butts were calculated from the analytical results. Statistical analyses revealed a significant dependence of all observables on the cigarette quality class.Metodom inverzne voltammetrije na visećoj živinoj kapi (DPASV) određene su količine kadmija i olova u cigaretama triju vrsta (kvalitetni razredi prema JUS-u: Extra, II i IV). Pored duhana, papira i filtarskih čepića analizirani su i opušci i sirovi dimni kondenzat. Iz analističkih rezultata izračunana je frakcija prijenosa metala iz duhana u dimni kondenzat kao J retencija metala u opušku. Statističkim analizama utvrđena je ovisnost svili opservabli o kvalitetnom razredu cigarete

Nitrilotriacetato Complexes of Lanthanides - A Thermochemical Study

The heats of formation of mono- and bis-nitrilotriacetato complexes of tervalent lanthanide ions were measured calorimetrically at 20\u27 C in 0.1 M KN03• From the experimental heat data and the formation constants determined by others under similar experimental conditions the entropy changes on coordination were calculated. A support is given for the opinion that, in essentially electrostatic complexes, the complex formation enthalpies and entropies are mutually correlated because of the displacement of solvent molecules in complex formation

Detection of SUSY Signals in Stau Neutralino Co-annihilation Region at the LHC

We study the prospects of detecting the signal in the stau neutralino co-annihilation region at the LHC using tau leptons. The co-annihilation signal is characterized by the stau and neutralino mass difference (dM) to be 5-15 GeV to be consistent with the WMAP measurement of the cold dark matter relic density as well as all other experimental bounds within the minimal supergravity model. Focusing on tau's from neutralino_2 --> tau stau --> tau tau neutralino_1 decays in gluino and squark production, we consider inclusive MET+jet+3tau production, with two tau's above a high E_T threshold and a third tau above a lower threshold. Two observables, the number of opposite-signed tau pairs minus the number of like-signed tau pairs and the peak position of the di-tau invariant mass distribution, allow for the simultaneous determination of dM and M_gluino. For dM = 9 GeV and M_gluino = 850 GeV with 30 fb^-1 of data, we can measure dM to 15% and M_gluino to 6%.Comment: 4 pages LaTex, 3 figures. To appear in Proceedings of SUSY06, the 14th International Conference on Supersymmetry and the Unification of Fundamental Interactions, UC Irvine, California, 12-17 June 2006. A typo in a reference is correcte

Factors affecting urban demand for live sheep: The case of Addis Ababa, Ethiopia

As the share of small ruminant meat, especially sheep, in the demand and consumption of meat in general grows, information about consumer expenditure behaviour and demand parameters for live sheep will be valuable for several interest groups in the sheep industry. Using the Heckman two-stage approach, this study shows that sheep prices and household income, as well as socio-demographic factors, including household size and composition, significantly affect the likelihood of buying live sheep and expenditures on live sheep. Projections of live sheep demand and supply in Addis Ababa in 2010 and 2020 show that sheep producers in Addis Ababa alone will be able to meet up to only 27% of the demand