Magnetoliposomes

The adsorption of different types of phosphatidylglycerols onto magnetizable solid particles is studied. The super-paramagnetic magnetite spheres used have an average diameter of only 14 nm and are stabilized by lauric acid to keep them in solution. During incubation and dialysis of this water-based magnetic fluid in the presence of preformed sonicated phospholipid vescles, magnetoliposomes are formed which are captured from solution with high efficiency by high-gradient magnetophoresis. Support for the bilayer character of the phospholipid coat is derived from both theoretical calculations and experimental data. Phospholipids which form the inner monolayer are adsorbed very quickly with their charged headgroup orientated towards the iron oxide surface. The high-affinity character of the binding is reflected in the adsorption isotherms and is further illustrated by their non-extractability with high concentrations of Tween 20. The outer layer assembles through interaction with the exposed hydrocarbon chains. As compared to the inner layer, the phospholipids adsorb at a much slower rate and are displaced by Tween 20 concentrations which usually disrupt conventional membranes. The adsorption isotherms for this layer obey the Langmuir expression. The affinity constants, derived from them, progressively increase as the hydrophobic nature of the phosphatidylglycerols is more pronounced.Abbreviations DXPG di-fatty acyl form of phosphatdylglycerol where X=L, Lauroyl - M myristoyl - C _15:0 pentadecanoyl - O oleoyl. TES, 2-((tris(hydroxymethyl)methyl)amino)ethanesulfonic acid     

Adsorption and immobilisation of human insulin on graphene monoxide,silicon carbide and boron nitride nanosheets investigated by molecular dynamics simulation

The adsorption and immobilisation of human insulin onto the bio-compatible nanosheets including graphene monoxide, silicon carbide and boron nitride nanosheets were studied by molecular dynamics simulation at the temperature of 310 K. After equilibration, heating and 100 ns production molecular dynamic runs, it was found that the insulin was adsorbed and immobilised onto the considered surfaces in a native folded state. The structural parameters, including root-mean-square deviation and fluctuation, surface accessible solvent area, radius of gyration (R_g) and the distance between the centre of the mass of immobilised protein and the surface of the considered nanosheets, were measured, analysed and discussed. The energetics of the studied systems such as the interaction energy between protein and nanosheet was also measured and addressed. The discussions were centred on the structural and energetic parameters of the protein and nanosheets, including charge density, hydrophobicity, hydrophilicity and residue polarity. The results also showed that the active site of C-termini of chain B played an important role in the adsorption process and this could be helpful in the protection of insulin in its smart delivery and release applications.     

Involvement of the Lipopolysaccharides of Azospirilla in the Interaction with Wheat Seedling Roots

The present study was undertaken to comparatively investigate the attachment capacities of Azospirillum brasilenseSp245 and its lipopolysaccharide-defective Omegon-Km mutants KM018 and KM252, as well as their activities with respect to the alteration of the morphology of wheat seedling root hairs. The adsorption dynamics of the parent Sp245 and mutant KM252 strains of azospirilla on the seedling roots of the soft spring wheat cv. Saratovskaya 29 were similar; however, the attachment capacity of the mutant KM252 was lower than that of the parent strain throughout the incubation period (15 min to 48 h). The mutation led to a considerable decrease in the hydrophobicity of the Azospirillumcell surface. The lipopolysaccharides extracted from the outer membrane of A. brasilenseSp245 and mutant cells with hot phenol and purified by chromatographic methods were found to induce the deformation of the wheat seedling root hairs, the lipopolysaccharide of the parent strain being the most active in this respect. The role of the carbohydrate moiety of lipopolysaccharides in the interaction of Azospirillumcells with plants is discussed.     

Aluminium-induced changes in the surface and micropore properties of wheat roots: a study using the water vapor adsorption-desorption technique

The geometric and energetic characteristics of root surfaces of two wheat (Triticum L.) varieties, Al tolerant (Inia 66/16) and Al sensitive (Henika), were estimated from experimental water vapor adsorption–desorption data. Roots stressed for around 1 week at pH 4 without and with a toxic aluminium level (0.741 mol m^–3) were studied at the tillering and shooting stages. Roots grown continuously at pH 7 were taken as control. The surface properties of the pH 4 stressed roots were apparently the same as those of the control roots whatever the root age. For the roots of both varieties, the surface area and total micropore volume increased markedly after aluminium treatment. The average micropore radius increased significantly for the sensitive wheat, whereas it increased only slightly for the resistant one. Under Al treatment the number of large pores increased while small pores were fewer for both plants, indicating a possible alteration of the build-up of root tissue. The root surface pores were fractal. The fractal dimension of the sensitive wheat roots decreased under Al treatment, whereas for the resistant wheat this remained apparently unchanged. The adsorption energy distribution functions had different shapes for the sensitive and the resistant wheat varieties: the sensitive variety had greater number of high energy adsorption centers, which implies that the root tolerance on Al stress may be connected with lower polarity of the surface.     

A simple process for the isolation of epithelial cells from bacteria-contaminated samples using anchoring molecules

A simple and efficient tool to isolate epithelial cells from bacteria-contaminated samples has been developed using two different microparticles functionalized with chemical molecules. The epithelial cells could be captured simply by biocompatible anchors for membranes (BAM), consisting of poly(ethylene glycol) functionalized with oleyl-chain-conjugated NHS (N-hydroxysuccinimide) on glass microparticles, whereas bacteria were adsorbed on 3-aminopropyltrimethoxysilane (ATPS)-functionalized magnetic microparticles. In the case of samples highly contaminated with bacteria, epithelial cells were not isolated successfully by both of the single BAM- and antibody-functionalized microparticles. Therefore, serial isolation steps of these two different chemical functionalized microparticles were introduced. The concentration of bacteria was decreased dramatically by using APTS-functionalized magnetic particles prior to the isolation of epithelial cells by BAM microparticles. With these serial processes, successful isolation of epithelial cells was achieved from bacteria-contaminated epithelial samples. The applicability of this method was verified with bacteria-contaminated intestinal samples biopsied from a BALB/C mouse for primary cell cultivation.     

RASPA: molecular simulation software for adsorption and diffusion in flexible nanoporous materials

A new software package, RASPA, for simulating adsorption and diffusion of molecules in flexible nanoporous materials is presented. The code implements the latest state-of-the-art algorithms for molecular dynamics and Monte Carlo (MC) in various ensembles including symplectic/measure-preserving integrators, Ewald summation, configurational-bias MC, continuous fractional component MC, reactive MC and Baker's minimisation. We show example applications of RASPA in computing coexistence properties, adsorption isotherms for single and multiple components, self- and collective diffusivities, reaction systems and visualisation. The software is released under the GNU General Public License.     

Root exudates from sunflower (Helianthus annuus L.) show a strong adsorption ability toward Cd(II)

Abstract

Cd(II) adsorption of root exudates from sunflower (Helianthus annuus L.) seedling was investigated by Cd ion-selective electrode, Fourier Transform Infrared spectroscopy, and fluorescence spectroscopy. Root exudates from Helianthus annuus L. had strong adsorption ability toward Cd(II). The adsorption process was pH-dependent and the maximum adsorption capacity, 150.8 mg g^?1, was observed at pH 7.0. Root exudates had pK _a1 at 4.7 for carboxyl and pK _a2 at 9.2 for phenolic, and amino groups. The aliphatic and aromatic (C?H) groups, amide III group, and the C (=O)?O and sulfonate groups were responsible for Cd(II) adsorption. The excitation emission matrix fluorescence spectroscopy showed protein-like substances participated in Cd adsorption and formed strong complexes, with conditional stability constants of 4.70 and 4.32, which is a little lower than that determined by potentiometric methods, 5.13. The strong Cd complexing ability of root exudates implies that root exudates may significantly affect mobility, toxicity, and phytoavailability of Cd. Cd binding of root exudates may be attributed to its interaction with the proteins, polysaccharides, and phenolic compounds in root exudates.     

Comparison of physical and covalent immobilization of lipase from Candida antarctica on polyamine microspheres of alkylamine matrix

Abstract

Polyamine microspheres (PA-M) prepared using polyethyleneimine as matrix were used for the immobilization of Candida antarctica lipase. The isoelectric point of PA-M is 10.6, and the hydrophobicity of PA-M was indicated using naphthalene. Optimization of conditions showed that the maximal loading of lipase on PA-M reached 230.2 mg g^{? 1} at pH 9.0 and 35°C. An increased buffer concentration had no effect on the activity of lipase but decreased the amount of lipase adsorbed. Simulation with Langmuir and Freundlich isotherms demonstrated that the adsorption of lipase on PA-M was thermodynamically favorable. Covalent crosslinking of the lipase adsorbed extended the pH range and increased the optimal temperature of the lipase activity. The physically adsorbed lipase (P-lipase) and the covalently immobilized derivative (C-lipase) retained more than 75% and 85% of their initial activity, respectively, after 10 cycles of usage. The half-lives of P-lipase and C-lipase at 50°C were 15.70 and 27.67 times higher than that of the free enzyme, respectively. Compared to P-lipase, covalent immobilization obviously reduced the catalytic efficiency and activation energy of the enzyme.