The influence of discrete surface charges on the force between charged surfaces

2005 ◽  
Vol 122 (10) ◽  
pp. 104705 ◽  
Author(s):  
Malek O. Khan ◽  
Simon Petris ◽  
Derek Y. C. Chan
Keyword(s):  
Surface Charges ◽  
Charged Surfaces ◽  
Discrete Surface

scholarly journals Characterization and Dye Decolorization Potential of Two Laccases from the Marine-Derived Fungus Pestalotiopsis sp.

2019 ◽  
Vol 20 (8) ◽  
pp. 1864 ◽  
Author(s):  
Wikee ◽  
Hatton ◽  
Turbé-Doan ◽  
Mathieu ◽  
Daou ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Catalytic Efficiency ◽  
Dye Decolorization ◽  
Sea Salt ◽  
Reactive Black 5 ◽  
Surface Charges ◽  
Recombinant Enzymes ◽  
Charged Surfaces ◽  
Three Dimensional Models ◽  
Encoding Genes

: Two laccase-encoding genes from the marine-derived fungus Pestalotiopsis sp. have been cloned in Aspergillus niger for heterologous production, and the recombinant enzymes have been characterized to study their physicochemical properties, their ability to decolorize textile dyes for potential biotechnological applications, and their activity in the presence of sea salt. The optimal pH and temperature of PsLac1 and PsLac2 differed in relation to the substrates tested, and both enzymes were shown to be extremely stable at temperatures up to 50 °C, retaining 100% activity after 3 h at 50 °C. Both enzymes were stable between pH 4–6. Different substrate specificities were exhibited, and the lowest Km and highest catalytic efficiency values were obtained against syringaldazine and 2,6-dimethoxyphenol (DMP) for PsLac1 and PsLac2, respectively. The industrially important dyes—Acid Yellow, Bromo Cresol Purple, Nitrosulfonazo III, and Reactive Black 5—were more efficiently decolorized by PsLac1 in the presence of the redox mediator 1-hydroxybenzotriazole (HBT). Activities were compared in saline conditions, and PsLac2 seemed more adapted to the presence of sea salt than PsLac1. The overall surface charges of the predicted PsLac three-dimensional models showed large negatively charged surfaces for PsLac2, as found in proteins for marine organisms, and more balanced solvent exposed charges for PsLac1, as seen in proteins from terrestrial organisms.

Highly Orientated Calcification in Newly Formed Bones on Negatively Charged Hydroxyapatite Electrets

2005 ◽  
Vol 284-286 ◽  
pp. 897-900 ◽  
Author(s):  
Satoshi Nakamura ◽  
Takayuki Kobayashi ◽  
Kimihiro Yamashita
Keyword(s):  
Electrostatic Force ◽  
Myeloid Cells ◽  
Osteoblastic Cells ◽  
Surface Charges ◽  
Electrical Polarization ◽  
Charged Surfaces ◽  
Negative Surface

Large negative charges induced by electrical polarization on hydroxyapatite (HA) ceramics has been demonstrated to enhance their osteoconductivities. The newly formed bones in the vicinities of the negatively charged surfaces were investigated in the views of crystallography and histology. The newly formed bone layers accompanied by mono-layered osteoblastic cells showed 4 perfect extinction positions in a 360° rotation, parallel and perpendicular to the HA surfaces by the optically polarizing images. The observation revealed that the newly formed bone layers directly bonding to the N-surface were consisted of the well-crystallized and highly orientated HA. Therefore, it was presumed that the enhanced osteobonding by negative surface charges was ascribed to the activation of myeloid cells and the intensified attraction of the HA nuclei by the electrostatic force.

scholarly journals Motion of an oil droplet through a capillary with charged surfaces

2019 ◽  
Vol 866 ◽  
pp. 721-758 ◽  
Author(s):  
P. Grassia
Keyword(s):  
Debye Length ◽  
The Body ◽  
Capillary Wall ◽  
Surface Charges ◽  
Oil Droplet ◽  
Noticeable Increase ◽  
Charged Surfaces ◽  
Singly Charged ◽  
Work Done ◽  
Osmotic Effects

A model developed by Wilmott et al. (J. Fluid Mech., vol. 841, 2018, pp. 310–350) for the advance of a charged oil droplet along a charged capillary pore is considered. The oil droplet is surrounded by an aqueous phase filling the pore, and the model considers a uniformly curved capillary static droplet front plus an aqueous thin film separating the body of the oil droplet from the capillary wall, with these two regions being joined by a transition region. The methodology follows a classical asymptotic approach proposed by Bretherton (J. Fluid Mech., vol. 10, 1961, pp. 166–188) but incorporates additional electro-osmotic effects (specifically an electro-osmotic disjoining tension) due to the charged surfaces. A number of dimensionless parameters control the model’s behaviour, of which the most important is denoted $\unicode[STIX]{x1D712}^{\prime }$ and represents the ratio between the ‘nominal’ thickness of the aqueous film (as determined neglecting any electrostatic effects) and the Debye length within the film, which is sensitive to ion concentrations and hence to salinity. When $\unicode[STIX]{x1D712}^{\prime }$ is large, electro-osmotic effects are screened and Bretherton’s classical results are recovered. However as $\unicode[STIX]{x1D712}^{\prime }$ decreases, electro-osmotic effects come into play and the film becomes much thicker than Bretherton’s prediction to ensure that screening effects are not altogether lost, and also there is a noticeable increase in the pressure needed to drive the droplet front along. These results apply with minor variations in the case of singly charged surfaces (charge on either oil or on the capillary wall), oil and wall surfaces with like charges, or oil and wall surfaces with opposite but unequal charges. However in the case of opposite and equal charges, the system’s behaviour changes dramatically. There is now a conjoining electro-osmotic pressure rather than a disjoining tension, the film becomes thinner than the analogous Bretherton film, and the pressure needed to drive the droplet front along decreases. Surprisingly in this case, for sufficiently small $\unicode[STIX]{x1D712}^{\prime }$, the work done by the conjoining pressure can exceed the work done against viscous dissipation, meaning the pressure required to drive the droplet front is not just smaller than in Bretherton’s predictions but also slightly less than would be estimated based on capillary forces alone. Although the main effect of reducing salinity is to increase Debye length and hence reduce $\unicode[STIX]{x1D712}^{\prime }$, salinity also affects surface charges. A situation is explored whereby reducing salinity affects charges, producing a switch from disjoining tensions to conjoining pressures and back again: this leads to a non-monotonic response in film thickness and pressure required to drive the droplet front along.

scholarly journals Automatic Actin Filament Quantification and Cell Shape Modeling of Osteoblasts on Charged Ti Surfaces

2021 ◽  
Vol 11 (12) ◽  
pp. 5689
Author(s):  
Martina Gruening ◽  
Jonathan E. Dawson ◽  
Christian Voelkner ◽  
Sven Neuber ◽  
Katja Fricke ◽  
...  
Keyword(s):  
Actin Filament ◽  
Cell Shape ◽  
Adhesion Forces ◽  
Surface Charges ◽  
Cellular Functions ◽  
Ion Conductance ◽  
Cortical Tension ◽  
Scanning Ion Conductance Microscopy ◽  
Charged Surfaces ◽  
The Impact

Surface charges at the cell–biomaterial interface are known to determine cellular functions. Previous findings on cell signaling indicate that osteoblastic cells favor certain moderately positive surface charges, whereas highly positive charges are not tolerated. In this study, we aimed to gain deeper insights into the influence exerted by surface charges on the actin cytoskeleton and the cell shape. We analyzed surfaces with a negative, moderately positive, and highly positive zeta (ζ) potential: titanium (Ti), Ti with plasma polymerized allylamine (PPAAm), and Ti with a polydiallyldimethylammonium chloride (PDADMA) multilayer, respectively. We used the software FilaQuant for automatic actin filament quantification of osteoblastic MG-63s, analyzed the cell edge height with scanning ion conductance microscopy (SICM), and described the cellular shape via a mathematical vertex model. A significant enhancement of actin filament formation was achieved on moderately positive (+7 mV) compared with negative ζ-potentials (−87 mV). A hampered cell spreading was reflected in a diminished actin filament number and length on highly positively charged surfaces (+50 mV). Mathematical simulations suggested that in these cells, cortical tension forces dominate the cell–substrate adhesion forces. Our findings present new insights into the impact of surface charges on the overall cell shape and even intracellular structures.

The Influence of Phytohormones on Zeta Potential and Electrokinetic Charges of Winter Wheat Cells

2002 ◽  
Vol 57 (7-8) ◽  
pp. 696-704 ◽  
Author(s):  
Maria Filek ◽  
Maria Zembala ◽  
Magdalena Szechyńska-Hebda
Keyword(s):  
Cell Culture ◽  
Zeta Potential ◽  
Winter Wheat ◽  
Protein Composition ◽  
Embryogenic Culture ◽  
Surface Charges ◽  
Water Solutions ◽  
Charged Surfaces ◽  
Phospholipid Liposomes ◽  
Negative Adsorption

The zeta potential measurements of protoplasts obtained from winter wheat cell culture and phospholipid liposomes were performed to determine the electrokinetic charge in a medium containing various phytohormones (kinetin, 2,4-D and zearalenone) in absence and in presence of 2·10-5ᴍCa2+. Calli were induced from immature inflorescences (inf) and embryos (emb) and cultured to obtain non-embryogenic (NE) and embryogenic (E) cell tissues. All investigated phytohormones indicate ability to adsorb to the negatively charged surfaces (latex, L88 - model negative adsorption site) both in water solutions and at the presence of mannitol and buffer (MES). In biological systems (protoplasts and liposomes - prepared from phospholipids of protoplasts) the electrokinetic charges were dependent on the phospholipid and protein composition of cells. The influence of protein groups on electrokinetic charge was calculated from charge values of protoplasts and liposomes, assuming additivity of surface charges. The comparison of calculated charges for protoplasts and liposomes indicate that 2,4-D is better adsorbed to the phospholipid and proteins of NE cells whereas kinetin is bound to the phospholipid and protein sites of E calli. This effect may be connected with embryogenesis process, where non-embryogenic culture of wheat requires 2,4-D in the medium, and embryogenic culture requires cytokinin rather. Zearalenone binding is especially dependent on the kind of explant.

Electro-osmosis of superimposed fluids in the presence of modulated charged surfaces in narrow confinements

2015 ◽  
Vol 776 ◽  
pp. 390-429 ◽  
Author(s):  
Shubhadeep Mandal ◽  
Uddipta Ghosh ◽  
Aditya Bandopadhyay ◽  
Suman Chakraborty
Keyword(s):  
Analytical Solutions ◽  
Numerical Solutions ◽  
Surface Charges ◽  
Charged Surfaces ◽  
Physico Chemical ◽  
Approximate Analytical Solutions ◽  
Electro Osmosis ◽  
Flow Features ◽  
Field Formalism ◽  
Modulation Wavelength

In the present study, we attempt to analyse the electro-osmotic flow of two superimposed fluids through narrow confinements in the presence of axially modulated surface charges. We attempt to solve for the flow structure as well as the interface deformation by both analytical and numerical techniques. Approximate analytical solutions are obtained through asymptotic analysis for low deformations, whereas numerical solutions are obtained by applying the phase field formalism; the numerical solutions are obtained for small as well as large interfacial deformations. The analytical solutions are derived only for the transient deformation of the interface, neglecting the transience in the flow, i.e. the flow is assumed to be quasisteady. The numerical solutions, however, are derived including the effects of inertia and transients in the flow. We attempt to compare our analytical and numerical results and explore the effects of several physico-chemical parameters on the deformation of the interface as well as the nature of the flow. Our analysis reveals that parameters such as the modulation wavelength, surface tension (described through the capillary number), viscosity ratio, permittivity ratio and extent of asymmetry in the potential on the two walls are the major contributors to the deformation and the resulting flow features.

Phosphate-Functionalized Stabilized F127 Nanoparticles: Introduction of Discrete Surface Charges and Electrophoretic Determination of Aggregation Number

2019 ◽  
Vol 27 (7) ◽  
pp. 657-662
Author(s):  
Juyoung Hwang ◽  
Mingyeong Kang ◽  
Mila Irva Sari ◽  
Tae Hyeong Lee ◽  
Kibeom Kim ◽  
...  
Keyword(s):  
Aggregation Number ◽  
Surface Charges ◽  
Discrete Surface
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