Articoli di riviste: "Direct surface interactions"

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Peyre, P., M. Gharbi, C. Gorny, M. Carin, S. Morville, Denis Carron, P. Le Masson, T. Malot e R. Fabbro. "Surface Finish Issues after Direct Metal Deposition". Materials Science Forum 706-709 (gennaio 2012): 228–33. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.228.

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Derived from laser cladding, the Direct Metal Deposition (DMD) laser process, is based upon a laser beam – projected powder interaction, and allows manufacturing complex 3D shapes much faster than conventional processes. However, the surface finish remains critical, and DMD parts usually necessitate post-machining steps. In this context, the focus of our work was: (1) to understand the physical mechanisms responsible for deleterious surface finishes, (2) to propose different experimental solutions for improving surface finish. Our experimental approach is based upon: (1) adequate modifications of the DMD conditions (gas shielding, laser conditions, coaxial or off-axis nozzles), (2) a characterization of laser-powder-melt-pool interactions using fast camera analysis, (3) a precise check of surface aspects using 3D profilometry, SEM, (4) preliminary thermo-convective simulations to understand melt-pool hydrodynamics. Most of the experimental tests were carried out on a Ti6Al4V titanium alloy, widely investigated already. Results confirm that surface degradation depends on two aspects: the sticking of non-melted or partially melted particles on the free surfaces, and the formation of menisci with more or less pronounced curvature radii. Among other aspects, a reduction of layer thickness and an increase of melt-pool volumes to favor re-melting processes are shown to have a beneficial effect on roughness parameters.

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Linne, Christine, Daniele Visco, Stefano Angioletti-Uberti, Liedewij Laan e Daniela J. Kraft. "Direct visualization of superselective colloid-surface binding mediated by multivalent interactions". Proceedings of the National Academy of Sciences 118, n. 36 (31 agosto 2021): e2106036118. http://dx.doi.org/10.1073/pnas.2106036118.

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Reliably distinguishing between cells based on minute differences in receptor density is crucial for cell–cell or virus–cell recognition, the initiation of signal transduction, and selective targeting in directed drug delivery. Such sharp differentiation between different surfaces based on their receptor density can only be achieved by multivalent interactions. Several theoretical and experimental works have contributed to our understanding of this “superselectivity.” However, a versatile, controlled experimental model system that allows quantitative measurements on the ligand–receptor level is still missing. Here, we present a multivalent model system based on colloidal particles equipped with surface-mobile DNA linkers that can superselectively target a surface functionalized with the complementary mobile DNA-linkers. Using a combined approach of light microscopy and Foerster resonance energy transfer (FRET), we can directly observe the binding and recruitment of the ligand–receptor pairs in the contact area. We find a nonlinear transition in colloid-surface binding probability with increasing ligand or receptor concentration. In addition, we observe an increased sensitivity with weaker ligand–receptor interactions, and we confirm that the timescale of binding reversibility of individual linkers has a strong influence on superselectivity. These unprecedented insights on the ligand–receptor level provide dynamic information into the multivalent interaction between two fluidic membranes mediated by both mobile receptors and ligands and will enable future work on the role of spatial–temporal ligand–receptor dynamics on colloid-surface binding.

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Lai, Chiu-Chun, Kuo-Shien Huang, Po-Wei Su, Chang-Mou Wu e Ching-Nan Huang. "Interactions of modified Gemini surfactants: Interactions with direct dyes and dyeing properties in cotton fabrics". Modern Physics Letters B 33, n. 14n15 (28 maggio 2019): 1940002. http://dx.doi.org/10.1142/s0217984919400025.

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This study investigated dye–surfactant interactions between a series of modified Gemini surfactants and commercial direct dyes in aqueous solution and their corresponding effects on cotton fabric dyeing. A surface tension meter was also used to measure surface activities of compounds containing electrolyte under conditions similar to those in dyeing processes. The surface tension measurements showed lower than normal surface tension in surfactant solutions containing electrolyte. From the UV-Vis spectra, the isosbestic point indicated that dye–surfactant complexes had formed and existed as hydrophilic interaction between direct dyes and modified Gemini surfactants. When dyeing cotton fabric with red dye and orange dye, the presence of these surfactants decreased dye uptake rate but increased for blue dye because the dye–surfactant interaction had formed a hydrophilic complex.

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Norris, Anne, Mario A. Bianchet e Jef D. Boeke. "Compensatory Interactions between Sir3p and the Nucleosomal LRS Surface Imply Their Direct Interaction". PLoS Genetics 4, n. 12 (12 dicembre 2008): e1000301. http://dx.doi.org/10.1371/journal.pgen.1000301.

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Zhu, Chongqin, Yurui Gao, Weiduo Zhu, Jian Jiang, Jie Liu, Jianjun Wang, Joseph S. Francisco e Xiao Cheng Zeng. "Direct observation of 2-dimensional ices on different surfaces near room temperature without confinement". Proceedings of the National Academy of Sciences 116, n. 34 (2 agosto 2019): 16723–28. http://dx.doi.org/10.1073/pnas.1905917116.

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Water–solid interfaces play important roles in a wide range of fields, including atmospheric science, geochemistry, electrochemistry, and food science. Herein, we report simulation evidence of 2-dimensional (2D) ice formation on various surfaces and the dependence of the 2D crystalline structure on the hydrophobicity and morphology of the underlying surface. Contrary to the prevailing view that nanoscale confinement is necessary for the 2D liquid-to-bilayer ice transition, we find that the liquid-to-bilayer hexagonal ice (BHI) transition can occur either on a model smooth surface or on model fcc-crystal surfaces with indices of (100), (110), and (111) near room temperature. We identify a critical parameter that characterizes the water–surface interaction, above which the BHI can form on the surface. This critical parameter increases as the temperature increases. Even at temperatures above the freezing temperature of bulk ice (Ih), we find that BHI can also form on a superhydrophilic surface due to the strong water–surface interaction. The tendency toward the formation of BHI without confinement reflects a proper water–surface interaction that can compensate for the entropy loss during the freezing transition. Furthermore, phase diagrams of 2D ice formation are described on the plane of the adsorption energy versus the fcc lattice constant (Eads–afcc), where 4 monolayer square-like ices are also identified on the fcc model surfaces with distinct water–surface interactions.

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Touhami, Ahmed, Barbara Hoffmann, Andrea Vasella, Frédéric A. Denis e Yves F. Dufrêne. "Aggregation of yeast cells: direct measurement of discrete lectin–carbohydrate interactions". Microbiology 149, n. 10 (1 ottobre 2003): 2873–78. http://dx.doi.org/10.1099/mic.0.26431-0.

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Aggregation of microbial cells mediated by specific interactions plays a pivotal role in the natural environment, in medicine and in biotechnological processes. Here we used atomic force microscopy (AFM) to measure individual lectin–carbohydrate interactions involved in the flocculation of yeast cells, an aggregation event of crucial importance in fermentation technology. AFM probes functionalized with oligoglucose carbohydrates were used to record force-distance curves on living yeast cells at a rate of 0·5 μm s−1. Flocculating cells showed adhesion forces of 121±53 pN, reflecting the specific interaction between individual cell-surface lectins and glucose residues. Similar adhesion forces, 117±41 pN, were measured using probes functionalized with the lectin concanavalin A and attributed to specific binding to cell-surface mannose residues. By contrast, specific interaction forces were not observed in non-flocculating conditions, i.e. in the presence of mannose or when using non-flocculating cells, pointing to their involvement in yeast flocculation. The single molecule force spectroscopy measurements presented here provide a means to study a variety of cellular interactions at the molecular level, such as the adhesion of bacteria to animal and plant tissues.

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Hendrix, Martin, E. Scott Priestley, Gerald F. Joyce e Chi-Huey Wong. "Direct Observation of Aminoglycoside−RNA Interactions by Surface Plasmon Resonance". Journal of the American Chemical Society 119, n. 16 (aprile 1997): 3641–48. http://dx.doi.org/10.1021/ja964290o.

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Singla, Saranshu, Dharamdeep Jain, Chelsea M. Zoltowski, Sriharsha Voleti, Alyssa Y. Stark, Peter H. Niewiarowski e Ali Dhinojwala. "Direct evidence of acid-base interactions in gecko adhesion". Science Advances 7, n. 21 (maggio 2021): eabd9410. http://dx.doi.org/10.1126/sciadv.abd9410.

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While it is generally accepted that van der Waals (vdW) forces govern gecko adhesion, several studies indicate contributions from non-vdW forces and highlight the importance of understanding the adhesive contact interface. Previous work hypothesized that the surface of gecko setae is hydrophobic, with nonpolar lipid tails exposed on the surface. However, direct experimental evidence supporting this hypothesis and its implications on the adhesion mechanism is lacking. Here, we investigate the sapphire-setae contact interface using interface-sensitive spectroscopy and provide direct evidence of the involvement of acid-base interactions between polar lipid headgroups exposed on the setal surface and sapphire. During detachment, a layer of unbound lipids is left as a footprint due to cohesive failure within the lipid layer, which, in turn, reduces wear to setae during high stress sliding. The absence of this lipid layer enhances adhesion, despite a small setal-substrate contact area. Our results show that gecko adhesion is not exclusively a vdW-based, residue-free system.

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Ivanov, A. S., e A. E. Medvedev. "Optical surface plasmon resonance biosensors in molecular fishing". Biomeditsinskaya Khimiya 61, n. 2 (2015): 231–38. http://dx.doi.org/10.18097/pbmc20156102231.

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An optical biosensor employing surface plasmon resonance is a highly efficient instrument applicable for direct real time registration of molecular interactions without additional use of any labels or coupled processes. As an independent approach it is especially effective in analysis of various ligand receptor interactions. SPR-biosensors are used for validation of studies on intermolecular interactions in complex biological systems (affinity profiling of various groups of proteins, etc.). Recently, potential application of the SPR-biosensor for molecular fishing (direct affinity binding of target molecules from complex biological mixtures on the optical biosensor surface followed by their elution for identification by LC-MS/MS) has been demonstrated. Using SPR-biosensors in such studies it is possible to solve the following tasks: (a) SPR-based selection of immobilization conditions required for the most effective affinity separation of a particular biological sample; (b) SPR-based molecular fishing for subsequent protein identification by mass spectrometry; (c) SPR-based validation of the interaction of identified proteins with immobilized ligand. This review considers practical application of the SPR technology in the context of recent studies performed in the Institute of Biomedical Chemistry on molecular fishing of real biological objects.

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Yang, Hui, Wei Zhang, Ting Chen, Shizhe Huang, Baogang Quan, Min Wang, Junjie Li, Changzhi Gu e Jinben Wang. "Direct Experimental Evidence of Biomimetic Surfaces with Chemical Modifications Interfering with Adhesive Protein Adsorption". Molecules 24, n. 1 (21 dicembre 2018): 27. http://dx.doi.org/10.3390/molecules24010027.

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Current approaches to dealing with the worldwide problem of marine biofouling are to impart chemical functionality to the surface or utilize microtopography inspired by nature. Previous reports have shown that only introducing a single method may not resist adhesion of mussels or inhibit biofouling in static forms. While it is promising to integrate two methods to develop an effective antifouling strategy, related basic research is still lacking. Here, we have fabricated engineered shark skin surfaces with different feature heights and terminated with different chemical moieties. Atomic force microscopy (AFM) with a modified colloid probe technique and quartz crystal microbalance with a dissipation n (QCM-D) monitoring method have been introduced to directly determine the interactions between adhesive proteins and functionalized surfaces. Our results indicate that the adhesion strength of probe-surface decreases with increasing feature height, and it also decreases from bare Si surface to alkyl and hydroxyl modification, which is attributed to different contact area domains and interaction mechanisms. Combining biomimetic microtopography and surface chemistry, our study provides a new perspective for designing and developing underwater anti-fouling materials.

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Götzinger, Martin, e Wolfgang Peukert. "Dispersive forces of particle–surface interactions: direct AFM measurements and modelling". Powder Technology 130, n. 1-3 (febbraio 2003): 102–9. http://dx.doi.org/10.1016/s0032-5910(02)00234-6.

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Kanduč, Matej, e Roland R. Netz. "From hydration repulsion to dry adhesion between asymmetric hydrophilic and hydrophobic surfaces". Proceedings of the National Academy of Sciences 112, n. 40 (21 settembre 2015): 12338–43. http://dx.doi.org/10.1073/pnas.1504919112.

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Using all-atom molecular dynamics (MD) simulations at constant water chemical potential in combination with basic theoretical arguments, we study hydration-induced interactions between two overall charge-neutral yet polar planar surfaces with different wetting properties. Whether the water film between the two surfaces becomes unstable below a threshold separation and cavitation gives rise to long-range attraction, depends on the sum of the two individual surface contact angles. Consequently, cavitation-induced attraction also occurs for a mildly hydrophilic surface interacting with a very hydrophobic surface. If both surfaces are very hydrophilic, hydration repulsion dominates at small separations and direct attractive force contribution can—if strong enough—give rise to wet adhesion in this case. In between the regimes of cavitation-induced attraction and hydration repulsion we find a narrow range of contact angle combinations where the surfaces adhere at contact in the absence of cavitation. This dry adhesion regime is driven by direct surface–surface interactions. We derive simple laws for the cavitation transition as well as for the transition between hydration repulsion and dry adhesion, which favorably compare with simulation results in a generic adhesion state diagram as a function of the two surface contact angles.

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Eppell, S. J., B. A. Todd e F. R. Zypman. "Toward Measuring In-Vitro Single Molecule Force Fields Using a Scanning Force Microscope". Microscopy and Microanalysis 6, S2 (agosto 2000): 970–71. http://dx.doi.org/10.1017/s143192760003734x.

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The interaction of surfaces with their surroundings can be described as arising from force fields generated by molecules at the surface of interest. This statement is true for electrostatic interactions of proteins on cell membranes as well as steric interactions of macromolecules on polymer surfaces. To better understand these systems and ultimately to design superior materials, it is necessary to make direct measurements of these near-surface molecular scale force fields. Scanning force microscopy (SFM) holds some promise in the endeavor to make surface force measurements in a full three dimensional submolecularly resolved space. In-vitro measurements present a problem in that the force fields tend to be very short ranged. This necessitates placing the SFM probe very near the surface in order to measure the fields. The ubiquitous van der Waals attraction tends to induce an instability in the SFM instrument under these conditions leading to a non-equilibrium state. We have carefully examined this state of affairs and found that it is essential to use a substantially more sophisticated method to analyze SFM data than is commonly performed.

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Prelesnik, Jesse L., Robert G. Alberstein, Shuai Zhang, Harley Pyles, David Baker, Jim Pfaendtner, James J. De Yoreo, F. Akif Tezcan, Richard C. Remsing e Christopher J. Mundy. "Ion-dependent protein–surface interactions from intrinsic solvent response". Proceedings of the National Academy of Sciences 118, n. 26 (25 giugno 2021): e2025121118. http://dx.doi.org/10.1073/pnas.2025121118.

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The phyllosilicate mineral muscovite mica is widely used as a surface template for the patterning of macromolecules, yet a molecular understanding of its surface chemistry under varying solution conditions, required to predict and control the self-assembly of adsorbed species, is lacking. We utilize all-atom molecular dynamics simulations in conjunction with an electrostatic analysis based in local molecular field theory that affords a clean separation of long-range and short-range electrostatics. Using water polarization response as a measure of the electric fields that arise from patterned, surface-bound ions that direct the adsorption of charged macromolecules, we apply a Landau theory of forces induced by asymmetrically polarized surfaces to compute protein–surface interactions for two muscovite-binding proteins (DHR10-mica6 and C98RhuA). Comparison of the pressure between surface and protein in high-concentration KCl and NaCl aqueous solutions reveals ion-specific differences in far-field protein–surface interactions, neatly capturing the ability of ions to modulate the surface charge of muscovite that in turn selectively attracts one binding face of each protein over all others.

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Eyvaz, Murat, Hatice Deniz, Tuğrul S. Aktaş, Ebubekir Yüksel e Ahmet M. Saatçi. "Pre-Ozonation-Coagulant Interactions in Direct Filtration". Water Quality Research Journal 45, n. 3 (1 agosto 2010): 317–26. http://dx.doi.org/10.2166/wqrj.2010.034.

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Abstract Pre-ozonation–coagulant interactions effects in relation to the coagulant type and dosage in direct filtration of surface waters were investigated. The performance of the process was evaluated by monitoring the effluent quality and head loss development through the filter bed. Two identical pilot scale filter columns filtering the same raw water were operated in parallel. The raw water was brought from Ömerli Reservoir in Istanbul. Before filtering, the raw water flow was split into two equal flows. One of the streams was pre-ozonated and the other was aerated using contact chambers with equal volumes equipped with same number and type of diffusers. In coagulation experiments, one of the filters was operated using aluminum sulfate as a coagulant while the other one was run with ferric chloride. For similar filter run times, the effluent quality was always better with pre-ozonation compared to aeration. It was also observed that, aluminum sulfate application gave more favorable results for both particle and turbidity removal compared to ferric chloride. Ives’ filterability index which incorporates the important filtration design parameters such as: effluent quality, the headloss and the velocity of filtration into a dimensionless number was used for the comparison of the experimental results.

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Šilhavý, Miroslav. "A direct approach to nonlinear shells with application to surface-substrate interactions". Mathematics and Mechanics of Complex Systems 1, n. 2 (26 agosto 2013): 211–32. http://dx.doi.org/10.2140/memocs.2013.1.211.

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Munoz‐Robles, Brizzia G., Irina Kopyeva e Cole A. DeForest. "Surface Patterning of Hydrogel Biomaterials to Probe and Direct Cell–Matrix Interactions". Advanced Materials Interfaces 7, n. 21 (30 settembre 2020): 2001198. http://dx.doi.org/10.1002/admi.202001198.

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Monroe, Jacob I., Sally Jiao, R. Justin Davis, Dennis Robinson Brown, Lynn E. Katz e M. Scott Shell. "Affinity of small-molecule solutes to hydrophobic, hydrophilic, and chemically patterned interfaces in aqueous solution". Proceedings of the National Academy of Sciences 118, n. 1 (28 dicembre 2020): e2020205118. http://dx.doi.org/10.1073/pnas.2020205118.

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Performance of membranes for water purification is highly influenced by the interactions of solvated species with membrane surfaces, including surface adsorption of solutes upon fouling. Current efforts toward fouling-resistant membranes often pursue surface hydrophilization, frequently motivated by macroscopic measures of hydrophilicity, because hydrophobicity is thought to increase solute–surface affinity. While this heuristic has driven diverse membrane functionalization strategies, here we build on advances in the theory of hydrophobicity to critically examine the relevance of macroscopic characterizations of solute–surface affinity. Specifically, we use molecular simulations to quantify the affinities to model hydroxyl- and methyl-functionalized surfaces of small, chemically diverse, charge-neutral solutes represented in produced water. We show that surface affinities correlate poorly with two conventional measures of solute hydrophobicity, gas-phase water solubility and oil–water partitioning. Moreover, we find that all solutes show attraction to the hydrophobic surface and most to the hydrophilic one, in contrast to macroscopically based hydrophobicity heuristics. We explain these results by decomposing affinities into direct solute interaction energies (which dominate on hydroxyl surfaces) and water restructuring penalties (which dominate on methyl surfaces). Finally, we use an inverse design algorithm to show how heterogeneous surfaces, with multiple functional groups, can be patterned to manipulate solute affinity and selectivity. These findings, importantly based on a range of solute and surface chemistries, illustrate that conventional macroscopic hydrophobicity metrics can fail to predict solute–surface affinity, and that molecular-scale surface chemical patterning significantly influences affinity—suggesting design opportunities for water purification membranes and other engineered interfaces involving aqueous solute–surface interactions.

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Verzicco, R., e P. Orlandi. "Wall/Vortex-Ring Interactions". Applied Mechanics Reviews 49, n. 10 (1 ottobre 1996): 447–61. http://dx.doi.org/10.1115/1.3101985.

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This review article presents a state-of-the-art review of the ring and wall interactions in the case of normal and oblique collisions. The different approaches used to study this flow and the results obtained are described and discussed. These techniques span from flow visualizations to LDV measurements, direct numerical simulations, particle-in-cell vortex methods and viscous and inviscid interactions. The relevance of these basic flows to the comprehension of wall-turbulence is also described. Finally, further developments, such as interaction with a grooved surface and with a deformable wall, and in Non-Newtonian fluids, are suggested.

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Ralston, John, Ian Larson, Mark W. Rutland, Adam A. Feiler e Mieke Kleijn. "Atomic force microscopy and direct surface force measurements (IUPAC Technical Report)". Pure and Applied Chemistry 77, n. 12 (1 gennaio 2005): 2149–70. http://dx.doi.org/10.1351/pac200577122149.

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The atomic force microscope (AFM) is designed to provide high-resolution (in the ideal case, atomic) topographical analysis, applicable to both conducting and nonconducting surfaces. The basic imaging principle is very simple: a sample attached to a piezoelectric positioner is rastered beneath a sharp tip attached to a sensitive cantilever spring. Undulations in the surface lead to deflection of the spring, which is monitored optically. Usually, a feedback loop is employed, which holds the spring deflection constant, and the corresponding movement of the piezoelectric positioner thus generates the image. From this it can be seen that the scanning AFM has all the attributes necessary for the determination of surface and adhesion forces; a sensitive spring to determine the force, a piezoelectric crystal to alter the separation of the tip and surface, which if sufficiently well-calibrated also allows the relative separation of the tip and surface to be calculated. One can routinely quantify both the net surface force (and its separation dependence) as the probe approaches the sample, and any adhesion (pull-off) force on retraction. Interactions in relevant or practical systems may be studied, and, in such cases, a distinct advantage of the AFM technique is that a particle of interest can be attached to the end of the cantilever and the interaction with a sample of choice can be studied, a method often referred to as colloid probe microscopy. The AFM, or, more correctly, the scanning probe microscope, can thus be used to measure surface and frictional forces, the two foci of this article. There have been a wealth of force and friction measurements performed between an AFM tip and a surface, and many of the calibration and analysis issues are identical to those necessary for colloid probe work. We emphasize that this article confines itself primarily to elements of colloid probe measurement using the AFM.

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Abdullah Sajid e M Salman Latif. "Direct Electromagnetic Wave Scattering Calculation Using Methods of Moments through Layered Rough Surface". JOURNAL OF NANOSCOPE (JN) 4, n. 2 (31 dicembre 2023): 69–88. http://dx.doi.org/10.52700/jn.v4i2.97.

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This thesis focuses on the direct calculation of electromagnetic wave scattering through layered rough surfaces using the Method of Moments. The study aims to contribute to existing knowledge by addressing the problems associated with accurately predicting scattered electromagnetic fields from rough surfaces with layered structures. By using the Method of Moments, this research seeks to provide insights into the behavior of electromagnetic waves when interacting with multi-layered rough surfaces, offering valuable implications for practical engineering applications and the development of advanced computational tools for electromagnetic wave analysis. In practical terms, the surface is typically divided into small patches, and the electromagnetic field at each patch is determined using MoM. This involves solving integral equations describing the interaction between the induced currents on the surface and the incident field. The layered structure may require additional equations to model the reflection of waves and the transmission at the boundaries between the layers. The direct problem is also examined in a two-dimensional picture, where the rough surface profile and the medium are known parameters, and the electromagnetic waves scattered from the surface to the entire space are the unknowns. The rough surface is considered to have a finite length and can be deterministic or arise from a stationary stochastic random process, with a focus on Gaussian-type rough surfaces. The roughness is considered as two basic types: as a perfect electric conductor (PEC) in free space and as a boundary between two dielectric media. The equations of integration obtained are based on the scalar solution of Green's theory, Helmholtz equations, and using Hankel type green functions as kernels due to the one-dimensional nature. The MoM is extensively used to solve these integral equations and is compared to asymptotic approaches and analytical. Various simulations are conducted to test the feasibility of the algorithms, and the results are thoroughly discussed. The study of electromagnetic wave scattering in one-dimensional rough surfaces involves the direct problem, where the field distribution in the whole space is determined using the equation of integration. These equations take into account the surface roughness and medium parameters they are solved using the Method of Moments (MoM) by expressing the field distribution on the surface using basis functions. The direct calculation of electromagnetic wave scattering through a layered rough surface using the Method of Moments (MoM) is a computationally intensive process and complex and. It contains simulating the interaction of EM waves with a complex surface, which presents challenges due to the multiple layers with different properties, and a roughly surface causing and diffraction of incident waves and scattering. When working with a layered rough surface increases the electromagnetic wave interaction complexity. Additional multiple layers introduce considerations, such as layer interfaces and accounting for different material abilities. This requires careful modeling and analysis to exactly capture the behavior of electromagnetic waves as they traverse through and interact with layers. MoM, a commonly used numerical method for solving electromagnetic scattering problems, discreteness the surface into small segments and solves integral equations to determine the fields that is scattered. This approach allows for a maximum analysis of electromagnetic interactions at a grained level.

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Liu, Fanghui, Hui Yang, Ting Chen, Shanmeiyu Zhang, Danfeng Yu, Yongqiang Chen e Quan Xie. "Direct Evidence of Salinity and pH Effects on the Interfacial Interactions of Asphaltene-Brine-Silica Systems". Molecules 25, n. 5 (8 marzo 2020): 1214. http://dx.doi.org/10.3390/molecules25051214.

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The hydraulic fracturing technique remains essential to unlock fossil fuel from shale oil reservoirs. However, water imbibed by shale during hydraulic fracturing triggers environmental and technical challenges due to the low flowback water recovery. While it appears that the imbibition of fracturing fluid is a complex function of physico-chemical processes in particular capillary force which is associated with wettability of oil-brine-shale, the controlling factor(s) to govern the wettability is incomplete and the literature data in this context is missing. We thus measured the adsorption/desorption of asphaltenes on silica surface in the presence of brines using quartz crystal microbalance with dissipation (QCM-D). We detected zeta potential of asphaltene-brine and brine-silica systems and calculated the disjoining pressures of the asphaltene-brine-silica system in the case of different salinity. Moreover, we performed a geochemical study to quantify the variation of surface chemical species at asphaltene and silica surfaces with different pH values and used the chemical force microscope (CFM) method to quantify the effect of pH on intermolecular forces. Our results show that lowering salinity or raising pH reduced the adhesion force between asphaltene and silica surface. For example, at a pH value of 6.5, when the concentration of injected water is reduced from 1000 mM to 100 mM and 10 mM, the adhesion force decreased by approximately 58% and 66%, respectively. In addition, for the 100 mM NaCl solution, when the pH value increased from 4.5 to 6.5 and 9, the adhesion force decreased by approximately 56% and 87%, respectively. Decreased adhesion forces between asphaltene and the silica surface could promote the desorption of asphaltene from the silica surface, resulting in a negative zeta potential for both asphaltene-silica and brine-silica interfaces and a shift of wettability towards water-wet characteristic. During such a process, -NH+ number at asphaltene surfaces decreases and the bonds between -NH+ and >SiO− break down, to further interpret the formation of a thinner asphaltene adlayer on the rock surface. This study proposes a reliable theoretical basis for the application of hydraulic fracturing technology, and a facile and possible manipulation strategy to increase flowback water from unconventional reservoirs.

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VANDERBILT, DAVID. "ORDERING AT SURFACES FROM ELASTIC AND ELECTROSTATIC INTERACTIONS". Surface Review and Letters 04, n. 05 (ottobre 1997): 811–16. http://dx.doi.org/10.1142/s0218625x9700081x.

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Elastic and electrostatic interactions can sometimes have a profound influence on surface morphology. Here, we review the conditions under which surface stress or surface dipole variations can give rise to spontaneous domain formation at surfaces, and focus especially on the case of the Si(100) surface. In principle, the anisotropy of the surface stress should cause the spontaneous formation of a striped domain structure on Si(100). In practice, the length scale for this domain structure turns out to be so large as to prevent its direct observation, although the influence of the elastic interactions has been observed indirectly in a variety of related experiments. It is now evident that by introducing Ge or B atoms, the conditions can be tuned in such a way that the spontaneous domain formation is strikingly observed. Because surface electrostatic dipolar interactions scale in the same way as elastic ones, it follows that similar effects can arise from these sources. We consider a simple model two-phase surface system with 1/r3 dipolar interactions, and find that the model exhibits spontaneous formation of two kinds of periodic domain structure. A striped domain structure is stable near half-filling, but as the area fraction is changed, a transition to a hexagonal lattice of almost-circular droplets occurs. The relation of this model to experimental surface systems, especially that of Langmuir layers at the water–air interface, will be discussed.

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Gong, Xiangjun, Zhaohui Wang e To Ngai. "Direct measurements of particle–surface interactions in aqueous solutions with total internal reflection microscopy". Chem. Commun. 50, n. 50 (2014): 6556–70. http://dx.doi.org/10.1039/c4cc00624k.

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This feature article reviews the experimental studies of the interactions between designed colloidal surfaces in the presence or absence of macromolecules/nanoparticles including depletion attraction, steric repulsion, bridging flocculation, and specific interactions by using Total Internal Reflection Microscopy.

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Dufrêne, Yves F., Christophe J. P. Boonaert, Patrick A. Gerin, Marcel Asther e Paul G. Rouxhet. "Direct Probing of the Surface Ultrastructure and Molecular Interactions of Dormant and Germinating Spores ofPhanerochaete chrysosporium". Journal of Bacteriology 181, n. 17 (1 settembre 1999): 5350–54. http://dx.doi.org/10.1128/jb.181.17.5350-5354.1999.

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ABSTRACT Atomic force microscopy (AFM) has been used to probe, under physiological conditions, the surface ultrastructure and molecular interactions of spores of the filamentous fungus Phanerochaete chrysosporium. High-resolution images revealed that the surface of dormant spores was uniformly covered with rodlets having a periodicity of 10 ± 1 nm, which is in agreement with earlier freeze-etching measurements. In contrast, germinating spores had a very smooth surface partially covered with rough granular structures. Force-distance curve measurements demonstrated that the changes in spore surface ultrastructure during germination are correlated with profound modifications of molecular interactions: while dormant spores showed no adhesion with the AFM probe, germinating spores exhibited strong adhesion forces, of 9 ± 2 nN magnitude. These forces are attributed to polysaccharide binding and suggested to be responsible for spore aggregation. This study represents the first direct characterization of the surface ultrastructure and molecular interactions of living fungal spores at the nanometer scale and offers new prospects for mapping microbial cell surface properties under native conditions.

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Kanev, Kamen. "Tangible Interfaces for Interactive Multimedia Presentations". Mobile Information Systems 4, n. 3 (2008): 183–93. http://dx.doi.org/10.1155/2008/982947.

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This article is devoted to tangible interfaces for steering and control of interactive multimedia presentations. Various methods for digital encoding of physical objects are considered and their applicability in surface encoding for tangible interface components is discussed. Experiments with presentation controls, based on direct interaction with digitally encoded printed handouts are reported. An innovative approach for transferring presentation controls from printed handouts to surfaces of real physical objects is introduced. Consequently labels, digitally enhanced with CLUSPI codes are created and presentation control trials involving real products with digitally encoded surfaces are conducted. USB and wireless cameras are employed as CLUSPI readers for implementing surface based interactions and a portable communication device with an embedded camera is considered as a possible truly mobile solution.

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Lai, Chun Chih, John M. Bell e Nunzio Motta. "Bovine Serum Albumin Adhesion Force Measurements Using an Atomic Force Microscopy". Advanced Materials Research 32 (febbraio 2008): 49–52. http://dx.doi.org/10.4028/www.scientific.net/amr.32.49.

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A new, direct method has been developed to measure the adhesion forces of bovine serum albumin (BSA) on surfaces by using Atomic Force Microscopy (AFM) in liquid environment. We were able to measure interactions between proteins and substrate surface in PBS solution directly without any modification to the substrate or the AFM tip. Two different surfaces have been used in the experiments: mica (hydrophilic surface) and polystyrene (hydrophobic surface). The results show that a polystyrene surface is more adhesive to BSA than a mica surface. This is consistent with previous research, which assessed that hydrophobic surfaces enhance protein adhesion but hydrophilic surfaces do not, demonstrating the effectiveness of the technique.

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LÃ¯Â¿Â½ttge, Andreas, e Pamela G. Conrad. "Direct Observation of Microbial Inhibition of Calcite Dissolution". Applied and Environmental Microbiology 70, n. 3 (marzo 2004): 1627–32. http://dx.doi.org/10.1128/aem.70.3.1627-1632.2004.

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ABSTRACT Vertical scanning interferometry (VSI) provides a method for quantification of surface topography at the angstrom to nanometer level. Time-dependent VSI measurements can be used to study the surface-normal retreat across crystal and other solid surfaces during dissolution or corrosion processes. Therefore, VSI can be used to directly and nondestructively measure mineral dissolution rates with high precision. We have used this method to compare the abiotic dissolution behavior of a representative calcite (CaCO3) cleavage face with that observed upon addition of an environmental microbe, Shewanella oneidensis MR-1, to the crystal surface. From our direct observations, we have concluded that the presence of the microbes results in a significant inhibition of the rate of calcite dissolution. This inhibition appears to be a 2nd-order effect that is related to the formation of etch pits. The opening of etch pits was greatly inhibited in the presence of added bacteria, suggesting that the bacterial cells exert their effect by inhibiting the formation of etch pits at high-energy sites at the crystal surface caused by lattice defects, e.g., screw or point dislocations. The experimental methodology thus provides a nondestructive, directly quantifiable, and easily visualized view of the interactions of microbes and minerals during weathering (or corrosion) processes or during mineral precipitation.

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Otto, Karen, Hans Elwing e Malte Hermansson. "Effect of Ionic Strength on Initial Interactions ofEscherichia coli with Surfaces, Studied On-Line by a Novel Quartz Crystal Microbalance Technique". Journal of Bacteriology 181, n. 17 (1 settembre 1999): 5210–18. http://dx.doi.org/10.1128/jb.181.17.5210-5218.1999.

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ABSTRACT A novel quartz crystal microbalance (QCM) technique was used to study the adhesion of nonfimbriated and fimbriated Escherichia coli mutant strains to hydrophilic and hydrophobic surfaces at different ionic strengths. This technique enabled us to measure both frequency shifts (Δf), i.e., the increase in mass on the surface, and dissipation shifts (ΔD), i.e., the viscoelastic energy losses on the surface. Changes in the parameters measured by the extended QCM technique reflect the dynamic character of the adhesion process. We were able to show clear differences in the viscoelastic behavior of fimbriated and nonfimbriated cells attached to surfaces. The interactions between bacterial cells and quartz crystal surfaces at various ionic strengths followed different trends, depending on the cell surface structures in direct contact with the surface. While Δf and ΔD per attached cell increased for nonfimbriated cells with increasing ionic strengths (particularly on hydrophobic surfaces), the adhesion of the fimbriated strain caused only low-level frequency and dissipation shifts on both kinds of surfaces at all ionic strengths tested. We propose that nonfimbriated cells may get better contact with increasing ionic strengths due to an increased area of contact between the cell and the surface, whereas fimbriated cells seem to have a flexible contact with the surface at all ionic strengths tested. The area of contact between fimbriated cells and the surface does not increase with increasing ionic strengths, but on hydrophobic surfaces each contact point seems to contribute relatively more to the total energy loss. Independent of ionic strength, attached cells undergo time-dependent interactions with the surface leading to increased contact area and viscoelastic losses per cell, which may be due to the establishment of a more intimate contact between the cell and the surface. Hence, the extended QCM technique provides new qualitative information about the direct contact of bacterial cells to surfaces and the adhesion mechanisms involved.

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LAI, CHUN-CHIH, NUNZIO MOTTA e JOHN M. BELL. "ATOMIC FORCE MICROSCOPY MEASUREMENTS OF BOVINE SERUM ALBUMIN ADHESION FORCES ON SURFACES". International Journal of Nanoscience 07, n. 06 (dicembre 2008): 299–303. http://dx.doi.org/10.1142/s0219581x08005468.

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A novel, direct technique has been developed to measure the interactions of bovine serum albumin (BSA) on surfaces by using atomic force microscopy (AFM) in a liquid environment. We have been able to measure adhesion forces between proteins and substrate surfaces in phosphate-buffered saline (PBS) solution directly, without any modification to the substrate and the AFM tip. Two different surfaces have been used in the measurements: mica (hydrophilic surface) and polystyrene (hydrophobic surface). The results show that a polystyrene surface has larger adhesion forces to BSA than a mica surface. This is consistent with previous research, which demonstrated that hydrophobic surfaces enhance protein adhesion but hydrophilic surfaces do not.

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St-Onge, Dominique, e Claude Gicquaud. "Evidence of direct interaction between actin and membrane lipids". Biochemistry and Cell Biology 67, n. 6 (1 giugno 1989): 297–300. http://dx.doi.org/10.1139/o89-045.

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Actin is a protein component of the cystoskeleton and is involved in cell motility. It is believed generally that actin filaments are attached to the cell membrane through an interaction with membranous actin-binding proteins. By using an in vitro system composed of liposomes and actin, we have shown that actin may also interact directly with the phospholipids of the membrane. Actin deposited at the surface of the liposome is organized in two regular patterns: a paracrystalline sheet of parallel filaments in register, or a netlike organization. These interactions of actin with membrane lipids occur only in the presence of millimolar concentrations of Mg2+. These results suggest that the interaction of the cytoskeleton with the membrane involves, at least in part, a direct association of actin with phospholipids.Key words: actin, membrane, liposome.

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Dinur, Uri, e Arnold T. Hagler. "Direct evaluation of nonbonding interactions from ab initio calculations". Journal of the American Chemical Society 111, n. 14 (luglio 1989): 5149–51. http://dx.doi.org/10.1021/ja00196a021.

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Cook, Steven R., e Mark A. Hoffbauer. "Understanding gas-surface interactions from direct force measurements using a specialized torsion balance". Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 15, n. 3 (maggio 1997): 1553–57. http://dx.doi.org/10.1116/1.580630.

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Cohen, Miriam, Nancy Hurtado-Ziola e Ajit Varki. "ABO blood group glycans modulate sialic acid recognition on erythrocytes". Blood 114, n. 17 (22 ottobre 2009): 3668–76. http://dx.doi.org/10.1182/blood-2009-06-227041.

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Abstract ABH(O) blood group polymorphisms are based on well-known intraspecies variations in structures of neutral blood cell surface glycans in humans and other primates. Whereas natural antibodies against these glycans can act as barriers to blood transfusion and transplantation, the normal functions of this long-standing evolutionary polymorphism remain largely unknown. Although microbial interactions have been suggested as a selective force, direct binding of lethal pathogens to ABH antigens has not been reported. We show in this study that ABH antigens found on human erythrocytes modulate the specific interactions of 3 sialic acid-recognizing proteins (human Siglec-2, 1918SC influenza hemagglutinin, and Sambucus nigra agglutinin) with sialylated glycans on the same cell surface. Using specific glycosidases that convert A and B glycans to the underlying H(O) structure, we show ABH antigens stabilize sialylated glycan clusters on erythrocyte membranes uniquely for each blood type, generating differential interactions of the 3 sialic acid-binding proteins with erythrocytes from each blood type. We further show that by stabilizing such structures ABH antigens can also modulate sialic acid-mediated interaction of pathogens such as Plasmodium falciparum malarial parasite. Thus, ABH antigens can noncovalently alter the presentation of other cell surface glycans to cognate-binding proteins, without themselves being a direct ligand.

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Day, Christopher J., Elizabeth N. Tran, Evgeny A. Semchenko, Greg Tram, Lauren E. Hartley-Tassell, Preston S. K. Ng, Rebecca M. King et al. "Glycan:glycan interactions: High affinity biomolecular interactions that can mediate binding of pathogenic bacteria to host cells". Proceedings of the National Academy of Sciences 112, n. 52 (16 dicembre 2015): E7266—E7275. http://dx.doi.org/10.1073/pnas.1421082112.

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Cells from all domains of life express glycan structures attached to lipids and proteins on their surface, called glycoconjugates. Cell-to-cell contact mediated by glycan:glycan interactions have been considered to be low-affinity interactions that precede high-affinity protein–glycan or protein–protein interactions. In several pathogenic bacteria, truncation of surface glycans, lipooligosaccharide (LOS), or lipopolysaccharide (LPS) have been reported to significantly reduce bacterial adherence to host cells. Here, we show that the saccharide component of LOS/LPS have direct, high-affinity interactions with host glycans. Glycan microarrays reveal that LOS/LPS of four distinct bacterial pathogens bind to numerous host glycan structures. Surface plasmon resonance was used to determine the affinity of these interactions and revealed 66 high-affinity host–glycan:bacterial–glycan pairs with equilibrium dissociation constants (KD) ranging between 100 nM and 50 µM. These glycan:glycan affinity values are similar to those reported for lectins or antibodies with glycans. Cell assays demonstrated that glycan:glycan interaction-mediated bacterial adherence could be competitively inhibited by either host cell or bacterial glycans. This is the first report to our knowledge of high affinity glycan:glycan interactions between bacterial pathogens and the host. The discovery of large numbers of glycan:glycan interactions between a diverse range of structures suggests that these interactions may be important in all biological systems.

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Sperling, Anne I., John R. Sedy, N. Manjunath, Abraham Kupfer, Blair Ardman e Janis K. Burkhardt. "Cutting Edge: TCR Signaling Induces Selective Exclusion of CD43 from the T Cell-Antigen-Presenting Cell Contact Site". Journal of Immunology 161, n. 12 (15 dicembre 1998): 6459–62. http://dx.doi.org/10.4049/jimmunol.161.12.6459.

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Abstract CD43, a large highly glycosylated molecule, is arguably the most abundant molecule on the surface of T cells. Nevertheless, the function of CD43 remains unclear. Utilizing fluorescence microscopy, we find that CD43 is excluded from the T cell-APC contact site. This exclusion is Ag dependent since optimal CD43 exclusion requires Ag-pulsed APC, and since signaling through CD3, in the absence of any other receptor ligand interactions, can induce the modulation of CD43. These data suggest that CD43 may function as a barrier to nonspecific T cell-APC interactions that is removed as a result of T cell activation. Exclusion from the interaction site is a unique feature of CD43 and not universally found for all large highly glycosylated molecules since CD45 is not excluded. Thus, CD43 may represent a novel regulatory molecule on the T cell surface that can direct T cell interactions by changing its location on the cell surface.

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KLEYN, AART W. "ROTATIONAL RAINBOW SCATTERING OF ORIENTED MOLECULES". Surface Review and Letters 01, n. 01 (giugno 1994): 157–73. http://dx.doi.org/10.1142/s0218625x94000175.

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Molecule-surface interactions depend on many degrees of freedom. In this report one degree of freedom is discussed in particular: the dependence of the interaction on the molecular orientation. Using electrostatic fields a thermal beam of oriented NO molecules is produced. By scattering this beam from a crystal, steric effects are measured for the direct scattering and adsorption of NO on Ag(111) and Pt(111). The interaction is quite different for both systems. Nevertheless, rotational rainbow scattering when the O-end of the molecule is facing the surface is observed in both cases. For NO–Pt(111) rotational rainbows are only observed at energies around 0.5 eV. Very strong randomisation is observed for NO scattering from Pt(111) at higher energies. The results are discussed in terms of the possible elementary topology of the potential energy surfaces.

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Akashi, Sachiko, Shin-ichiroh Saitoh, Yasutaka Wakabayashi, Takane Kikuchi, Noriaki Takamura, Yoshinori Nagai, Yutaka Kusumoto et al. "Lipopolysaccharide Interaction with Cell Surface Toll-like Receptor 4-MD-2". Journal of Experimental Medicine 198, n. 7 (29 settembre 2003): 1035–42. http://dx.doi.org/10.1084/jem.20031076.

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Toll-like receptors (TLRs) are innate recognition molecules for microbial products, but their direct interactions with corresponding ligands remain unclarified. LPS, a membrane constituent of gram-negative bacteria, is the best-studied TLR ligand and is recognized by TLR4 and MD-2, a molecule associated with the extracellular domain of TLR4. Although TLR4-MD-2 recognizes LPS, little is known about the physical interaction between LPS and TLR4-MD-2. Here, we demonstrate cell surface LPS–TLR4-MD-2 complexes. CD14 greatly enhances the formation of LPS–TLR4-MD-2 complexes, but is not coprecipitated with LPS–TLR4-MD-2 complexes, suggesting a role for CD14 in LPS loading onto TLR4-MD-2 but not in the interaction itself between LPS and TLR4-MD-2. A tentative dissociation constant (Kd) for LPS–TLR4-MD-2 complexes was ∼3 nM, which is ∼10–20 times lower than the reported Kd for LPS–MD-2 or LPS–CD14. The presence of detergent disrupts LPS interaction with CD14 but not with TLR4-MD-2. E5531, a lipid A antagonist developed for therapeutic intervention of endotoxin shock, blocks LPS interaction with TLR4-MD-2 at a concentration 100 times lower than that required for blocking LPS interaction with CD14. These results reveal direct LPS interaction with cell surface TLR4-MD-2 that is distinct from that with MD-2 or CD14.

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Meyer, Nils, Oleg Saburow, Martin Hohberg, Andrew N. Hrymak, Frank Henning e Luise Kärger. "Parameter Identification of Fiber Orientation Models Based on Direct Fiber Simulation with Smoothed Particle Hydrodynamics". Journal of Composites Science 4, n. 2 (22 giugno 2020): 77. http://dx.doi.org/10.3390/jcs4020077.

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The behavior of fiber suspensions during flow is of fundamental importance to the process simulation of discontinuous fiber reinforced plastics. However, the direct simulation of flexible fibers and fluid poses a challenging two-way coupled fluid-structure interaction problem. Smoothed Particle Hydrodynamics (SPH) offers a natural way to treat such interactions. Hence, this work utilizes SPH and a bead chain model to compute a shear flow of fiber suspensions. The introduction of a novel viscous surface traction term is key to achieve full agreement with Jeffery’s equation. Careful modelling of contact interactions between fibers is introduced to model suspensions in the non-dilute regime. Finally, parameters of the Reduced-Strain Closure (RSC) orientation model are identified using ensemble averages of multiple SPH simulations implemented in PySPH and show good agreement with literature data.

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Zhou, Weixiang, Han Shen, Chenyu Wu, Zeyi Tu, Feng He, Yanan Gu, Yurui Xue et al. "Direct Synthesis of Crystalline Graphdiyne Analogue Based on Supramolecular Interactions". Journal of the American Chemical Society 141, n. 1 (20 dicembre 2018): 48–52. http://dx.doi.org/10.1021/jacs.8b09945.

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Wu, Di, e Alexandra Navrotsky. "Probing the energetics of organic–nanoparticle interactions of ethanol on calcite". Proceedings of the National Academy of Sciences 112, n. 17 (13 aprile 2015): 5314–18. http://dx.doi.org/10.1073/pnas.1505874112.

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Knowing the nature of interactions between small organic molecules and surfaces of nanoparticles (NP) is crucial for fundamental understanding of natural phenomena and engineering processes. Herein, we report direct adsorption enthalpy measurement of ethanol on a series of calcite nanocrystals, with the aim of mimicking organic–NP interactions in various environments. The energetics suggests a spectrum of adsorption events as a function of coverage: strongest initial chemisorption on active sites on fresh calcite surfaces, followed by major chemical binding to form an ethanol monolayer and, subsequently, very weak, near-zero energy, physisorption. These thermochemical observations directly support a structure where the ethanol monolayer is bonded to the calcite surface through its polar hydroxyl group, leaving the hydrophobic ends of the ethanol molecules to interact only weakly with the next layer of adsorbing ethanol and resulting in a spatial gap with low ethanol density between the monolayer and subsequent added ethanol molecules, as predicted by molecular dynamics and density functional calculations. Such an ordered assembly of ethanol on calcite NP is analogous to, although less strongly bonded than, a capping layer of organics intentionally introduced during NP synthesis, and suggests a continuous variation of surface structure depending on molecular chemistry, ranging from largely disordered surface layers to ordered layers that nevertheless are mobile and can rearrange or be displaced by other molecules to strongly bonded immobile organic capping layers. These differences in surface structure will affect chemical reactions, including the further nucleation and growth of nanocrystals on organic ligand-capped surfaces.

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Kékicheff, Patrick. "From Heterocoagulation to Biorecognition: Preparation of Surfaces for Direct Measurement of Their Interactions in a Surface Force Apparatus". Macromolecular Symposia 335, n. 1 (gennaio 2014): 24–42. http://dx.doi.org/10.1002/masy.201200119.

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Boffa, Vittorio, Cristian Lunghi, Cejna A. Quist-Jensen, Giuliana Magnacca e Paola Calza. "Fabrication and Surface Interactions of Super-Hydrophobic Silicon Carbide for Membrane Distillation". Nanomaterials 9, n. 8 (13 agosto 2019): 1159. http://dx.doi.org/10.3390/nano9081159.

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Hydrophilic silicon carbide was modified by surface deposition of a super-hydrophobic coating that is based on perfluorosilanes. The modification was proven to yield membrane surfaces with contact angles that were higher than 145° and to be stable under hydrothermal conditions. The measurement of the isosteric heat of adsorption of water and toluene by microgravimetry showed that, after modification, the membrane material was fully covered by a low-energy surface, which is consistent with the fluorocarbon moieties that were introduced by the modification. The same modification method was applied to a commercial multichannel SiC membrane tube (nominal pore size = 0.04 µm), which was tested in a direct contact membrane distillation apparatus. The membrane was permeable to water vapour and volatiles, but it showed full rejection for salt ions and organic pollutants with low vapour pressure (such as ibuprofen and caffeine). Moreover, the membrane was reusable, and its performances were stable with no sign of pore wetting over 8 h of filtration.

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Bertinetti, Luca, Anna Tampieri, Elena Landi, V. Bolis, C. Busco e Gianmario Martra. "Surface Structure, Hydration and Cationic Sites of Nanohydroxyapatite". Key Engineering Materials 361-363 (novembre 2007): 87–90. http://dx.doi.org/10.4028/www.scientific.net/kem.361-363.87.

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In this work, we studied the surface/water interaction properties of a pure calcium hydroxyapatite (HA) and their modifications as a consequence of the partial Ca2+/Mg2+ (MHA) substitution by means of IR spectroscopy and microcalorimetry of adsorbed water. IR data indicated that water molecules in direct contact with the surface of HA are coordinated to surface cations and experience H-bond significantly stronger than in liquid water. The heats of adsorption associated to such interactions are very high, being twice-triple the heat of liquefaction of water. Interestingly, water experiences H-bond higher than in its bulk liquid state also in the second layer. Finally the entering in the material of Mg2+ ions was shown to significantly affect the affinity of the material toward water and the properties of its hydration layers.

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Jana, Pritam Kumar, e Bortolo Matteo Mognetti. "Surface-triggered cascade reactions between DNA linkers direct the self-assembly of colloidal crystals of controllable thickness". Nanoscale 11, n. 12 (2019): 5450–59. http://dx.doi.org/10.1039/c8nr10217a.

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Dales, S. L., e C. Anthony. "The interaction of methanol dehydrogenase and its cytochrome electron acceptor". Biochemical Journal 312, n. 1 (15 novembre 1995): 261–65. http://dx.doi.org/10.1042/bj3120261.

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A fluorescence method is described for direct measurement of the interaction between methanol dehydrogenase (MDH) and its electron acceptor cytochrome cL. This has permitted a distinction to be made between factors affecting electron transfer and those affecting the initial binding or docking process. It was confirmed that the initial interaction is electrostatic, but previous conclusions with respect to the mechanism of EDTA inhibition have been modified. It is proposed that the initial ‘docking’ of MDH and cytochrome cL is by way of ionic interactions between lysyl residues on its surface and carboxylate groups on the surface of cytochrome cL. This interaction is not inhibited by EDTA, which we suggest acts by binding to nearby lysyl residues, thus preventing movement of the ‘docked’ cytochrome to its optimal position for electron transfer, which probably involves interaction with the hydrophobic funnel in the surface of MDH.

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Thordarson, Pall, Rob Atkin, Wouter H. J. Kalle, Gregory G. Warr e Filip Braet. "Developments in Using Scanning Probe Microscopy To Study Molecules on Surfaces — From Thin Films and Single-Molecule Conductivity to Drug–Living Cell Interactions". Australian Journal of Chemistry 59, n. 6 (2006): 359. http://dx.doi.org/10.1071/ch06043.

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Scanning probe microscopy (SPM) techniques, including atomic force microscopy (AFM) and scanning tunnelling microscopy (STM), have revolutionized our understanding of molecule–surface interactions. The high resolution and versatility of SPM techniques have helped elucidate the morphology of adsorbed surfactant layers, facilitated the study of electronically conductive single molecules and biomolecules connected to metal substrates, and allowed direct observation of real-time processes such as in situ DNA hybridization and drug–cell interactions. These examples illustrate the power that SPM possesses to study (bio)molecules on surfaces and will be discussed in depth in this review.

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Dastjerdi, Roya, Andreas Scherrieble, Shiva Bahrizadeh, Fatemeh Avareh Sadrabadi e Laleh Hedayat. "A Key Major Guideline for Engineering Bioactive Multicomponent Nanofunctionalization for Biomedicine and Other Applications: Fundamental Models Confirmed by Both Direct and Indirect Evidence". BioMed Research International 2017 (2017): 1–11. http://dx.doi.org/10.1155/2017/2867653.

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This paper deals with the engineering multicomponent nanofunctionalization process considering fundamental physicochemical features of nanostructures such as surface energy, chemical bonds, and electrostatic interactions. It is pursued by modeling the surface nanopatterning and evaluating the proposed technique and the models. To this end, the effects of surface modifications of nanoclay on surface interactions, orientations, and final features of TiO2/Mt nanocolloidal textiles functionalization have been investigated. Various properties of cross-linkable polysiloxanes (XPs) treated samples as well as untreated samples with XPs have been compared to one another. The complete series of samples have been examined in terms of bioactivity and some physical properties, given to provide indirect evidence on the surface nanopatterning. The results disclosed a key role of the selected factors on the final features of treated surfaces. The effects have been thoroughly explained and modeled according to the fundamental physicochemical features. The developed models and associated hypotheses interestingly demonstrated a full agreement with all measured properties and were appreciably confirmed by FESEM evidence (direct evidence). Accordingly, a guideline has been developed to facilitate engineering and optimizing the pre-, main, and post-multicomponent nanofunctionalization procedures in terms of fundamental features of nanostructures and substrates for biomedical applications and other approaches.

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Falcucci, G., E. Jannelli, S. Ubertini e S. Succi. "Direct numerical evidence of stress-induced cavitation". Journal of Fluid Mechanics 728 (11 luglio 2013): 362–75. http://dx.doi.org/10.1017/jfm.2013.271.

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AbstractIn this paper direct numerical evidence of flow-induced incipient cavitation is presented through lattice Boltzmann simulations of multiphase flows with a non-ideal thermodynamic equation of state. Cavitation emerges spontaneously as a result of the underlying non-ideal interactions, with no need for any modelling criteria based on the fluid variables, such as pressure or stress tensor. The onset of cavitation is well captured by Joseph’s minimum tension criteria, (Joseph, J. Fluid Mech., vol. 366, 1998, pp. 367–378; Dabiri, Sirignano & Joseph, Phys. Fluids, vol. 19, 2007, 072112), complemented with surface tension corrections, as proposed by Brennen (Cavitation and Bubble Dynamics, Oxford University Press, 1995). The simulations also show that the cavitation number (${C}_{N} $) proves to be a poor predictor of the onset of cavitation. Finally, strong dependence of the bubble morphology on the surface tension is also highlighted.

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Montavoci, Linda, Omar Ben Mariem, Simona Saporiti, Tommaso Laurenzi, Luca Palazzolo, Alice Federica Ossoli, Uliano Guerrini, Laura Calabresi e Ivano Eberini. "In Silico Description of the Direct Inhibition Mechanism of Endothelial Lipase by ANGPTL3". International Journal of Molecular Sciences 25, n. 6 (21 marzo 2024): 3555. http://dx.doi.org/10.3390/ijms25063555.

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Angiopoietin-like protein 3 (ANGPTL3) is a plasmatic protein that plays a crucial role in lipoprotein metabolism by inhibiting the lipoprotein lipase (LPL) and the endothelial lipase (EL) responsible for the hydrolysis of phospholipids on high-density lipoprotein (HDL). Interest in developing new pharmacological therapies aimed at inhibiting ANGPTL3 has been growing due to the hypolipidemic and antiatherogenic profile observed in its absence. The goal of this study was the in silico characterization of the interaction between ANGPTL3 and EL. Because of the lack of any structural information on both the trimeric coiled-coil N-terminal domain of ANGPTL3 and the EL homodimer as well as data regarding their interactions, the first step was to obtain the three-dimensional model of these two proteins. The models were then refined via molecular dynamics (MD) simulations and used to investigate the interaction mechanism. The analysis of interactions in different docking poses and their refinement via MD allowed the identification of three specific glutamates of ANGPTL3 that recognize a positively charged patch on the surface of EL. These ANGPTL3 key residues, i.e., Glu154, Glu157, and Glu160, could form a putative molecular recognition site for EL. This study paves the way for future investigations aimed at confirming the recognition site and at designing novel inhibitors of ANGPTL3.

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