scholarly journals Interaction of the human N-Ras protein with lipid raft model membranes of varying degrees of complexity

2014 ◽  
Vol 395 (7-8) ◽  
pp. 779-789 ◽  
Author(s):  
Alexander Vogel ◽  
Jörg Nikolaus ◽  
Katrin Weise ◽  
Gemma Triola ◽  
Herbert Waldmann ◽  
...  
Keyword(s):  
Lipid Raft ◽  
Lipid Membranes ◽  
Model Systems ◽  
Stable Phase ◽  
Force Microscopy ◽  
Ras Protein ◽  
Atomic Force ◽  
Lipid Mixtures ◽  
Functional Aspects ◽  
And Function

Abstract Ternary lipid mixtures composed of cholesterol, saturated (frequently with sphingosine backbone), and unsaturated phospholipids show stable phase separation and are often used as model systems of lipid rafts. Yet, their ability to reproduce raft properties and function is still debated. We investigated the properties and functional aspects of three lipid raft model systems of varying degrees of biological relevance – PSM/POPC/Chol, DPPC/POPC/Chol, and DPPC/DOPC/Chol – using 2H solid-state nuclear magnetic resonance (NMR) spectroscopy, fluorescence microscopy, and atomic force microscopy. While some minor differences were observed, the general behavior and properties of all three model mixtures were similar to previously investigated influenza envelope lipid membranes, which closely mimic the lipid composition of biological membranes. For the investigation of the functional aspects, we employed the human N-Ras protein, which is posttranslationally modified by two lipid modifications that anchor the protein to the membrane. It was previously shown that N-Ras preferentially resides in liquid-disordered domains and exhibits a time-dependent accumulation in the domain boundaries of influenza envelope lipid membranes. For all three model mixtures, we observed the same membrane partitioning behavior for N-Ras. Therefore, we conclude that even relatively simple models of raft membranes are able to reproduce many of their specific properties and functions.

Deposition of Lipid Bilayers with Atomic Force Microscopy

2005 ◽  
Vol 11 (S03) ◽  
pp. 44-47 ◽  
Author(s):  
G. D. Tavares ◽  
M. C. de Oliveira ◽  
J. M. C. Vilela ◽  
M. S. Andrade
Keyword(s):  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Force Microscopy ◽  
Langmuir Blodgett ◽  
Flat Substrate ◽  
Atomic Force ◽  
Lipid Mixtures ◽  
A Cell ◽  
Integral Proteins ◽  
Spherical Vesicles

Biological membranes are constituted of lipids organized as a two dimensional bilayer supporting peripheral and integral proteins, providing a barrier between the inside and the outside of a cell [1]. Similar membranes can be prepared from the lipid mixtures forming liposomes. The liposomes are multi or unilamellar spherical vesicles in which an aqueous volume is enclosed and can be used to encapsulate some drugs [2]. In order to better expose the details of their structure, these membranes are generally deposited on the surface of a flat substrate. These supported planar lipid membranes can also provide a model system for investigating the properties and functions of the complex cell membrane and membrane mediated processes such as recognition events and biological signal transduction. Various methods have been used to create artificial lipid membranes supported on a solid surface, being the most used the Langmuir-Blodgett monolayers formation [3], the vesicle fusion or liposome adsorption [4] and the solution spreading [5].

scholarly journals Ultrafine metal-polymer catalysts based on polyconjugated systems for Fisher–Tropsch synthesis

2020 ◽  
Vol 92 (6) ◽  
pp. 977-984
Author(s):  
Mayya V. Kulikova ◽  
Albert B. Kulikov ◽  
Alexey E. Kuz’min ◽  
Anton L. Maximov
Keyword(s):  
Tropsch Synthesis ◽  
X Ray Diffraction ◽  
Fischer Tropsch ◽  
Force Microscopy ◽  
Composite Catalysts ◽  
Fe Catalyst ◽  
Atomic Force ◽  
And Function ◽  
Metal Polymer

AbstractFor previously studied Fischer–Tropsch nanosized Fe catalyst slurries, polymer compounds with or without polyconjugating structures are used as precursors to form the catalyst nanomatrix in situ, and several catalytic experiments and X-ray diffraction and atomic force microscopy measurements are performed. The important and different roles of the paraffin molecules in the slurry medium in the formation and function of composite catalysts with the two types of aforementioned polymer matrices are revealed. In the case of the polyconjugated polymers, the alkanes in the medium are “weakly” coordinated with the metal-polymer composites, which does not affect the effectiveness of the polyconjugated polymers. Otherwise, alkane molecules form a “tight” surface layer around the composite particles, which create transport complications for the reagents and products of Fischer-Tropsch synthesis and, in some cases, can change the course of the in situ catalyst formation.

Cross-bridge cycling gives rise to spatiotemporal heterogeneity of dynamic subcellular mechanics in cardiac myocytes probed with atomic force microscopy

2010 ◽  
Vol 298 (3) ◽  
pp. H853-H860 ◽  
Author(s):  
Evren U. Azeloglu ◽  
Kevin D. Costa
Keyword(s):  
Contractile Activity ◽  
Major Axis ◽  
Neonatal Rat ◽  
Pharmacological Treatments ◽  
Rat Cardiomyocytes ◽  
Force Microscopy ◽  
Cross Bridge ◽  
Apparent Modulus ◽  
Atomic Force ◽  
And Function

To study how the dynamic subcellular mechanical properties of the heart relate to the fundamental underlying process of actin-myosin cross-bridge cycling, we developed a novel atomic force microscope elastography technique for mapping spatiotemporal stiffness of isolated, spontaneously beating neonatal rat cardiomyocytes. Cells were indented repeatedly at a rate close but unequal to their contractile frequency. The resultant changes in pointwise apparent elastic modulus cycled at a predictable envelope frequency between a systolic value of 26.2 ± 5.1 kPa and a diastolic value of 7.8 ± 4.1 kPa at a representative depth of 400 nm. In cells probed along their major axis, spatiotemporal changes in systolic stiffness displayed a heterogeneous pattern, reflecting the banded sarcomeric structure of underlying myofibrils. Treatment with blebbistatin eliminated contractile activity and resulted in a uniform apparent modulus of 6.5 ± 4.8 kPa. This study represents the first quantitative dynamic mechanical mapping of beating cardiomyocytes. The technique provides a means of probing the micromechanical effects of disease processes and pharmacological treatments on beating cardiomyocytes, providing new insights and relating subcellular cardiac structure and function.

Structural evolution and acoustic phonon behavior in crystalline PTFE latex films

2003 ◽  
Vol 779 ◽  
Author(s):  
M. Pierno ◽  
C.S. Casari ◽  
A. Li Bassi ◽  
M.G. Beghi ◽  
R. Piazza ◽  
...  
Keyword(s):  
Structural Evolution ◽  
Crystalline Polymer ◽  
Model Systems ◽  
Fibrillar Structure ◽  
Sintering Process ◽  
Latex Films ◽  
Force Microscopy ◽  
Crystalline Polymers ◽  
Atomic Force ◽  
Acoustic Excitations

AbstractThe structural evolution of polytetrafluoroethylene (PTFE) crystalline polymer latex films is studied at hundreds nanometer length scale by atomic force microscopy and Brillouin light scattering. In a controlled sintering process the transition is observed from the original particle distribution towards a ‘fibrillar’ structure of crystalline regions embedded in a disordered matrix. This transition is accompanied by a cross-over from localized acoustic excitations to propagating acoustic phonons, related to mesoscopic elastic properties. After sintering, a ‘mark’ of the original particulate structure persists, suggesting that filming of crystalline polymers may be analogous to sintering of ceramic powders. Films of crystalline polymers can thus be exploited as model systems to study the elasto-optical properties of granular and disordered media.

scholarly journals Cellular heterogeneity in pressure and growth emerges from tissue topology and geometry

2018 ◽  
Author(s):  
Yuchen Long ◽  
Ibrahim Cheddadi ◽  
Vincent Mirabet ◽  
Gabriella Mosca ◽  
Mathilde Dumond ◽  
...  
Keyword(s):  
Water Movement ◽  
Turgor Pressure ◽  
Growth Control ◽  
Cellular Growth ◽  
Cellular Heterogeneity ◽  
Tissue Water ◽  
Water Conductivity ◽  
Force Microscopy ◽  
Atomic Force ◽  
And Function

Cell-to-cell heterogeneity prevails in many biological systems, although its origin and function are often unclear. Cell hydrostatic pressure, alias turgor pressure, is essential in physiology and morphogenesis, and its spatial variations are often overlooked. Here, based on a mathematical model describing cell mechanics and water movement in a plant tissue, we predict that cell pressure anticorrelates with cell neighbour number. Using atomic force microscopy, we confirm this prediction in the Arabidopsis shoot apical meristem, a population of stem cells that generate all plant aerial organs. Pressure is predicted to correlate either positively or negatively with cellular growth rate depending on osmotic drive, cell wall extensibility, and hydraulic conductivity. The meristem exhibits one of these two regimes depending on conditions, suggesting that, in this tissue, water conductivity is non-negligible in growth control. Our results illustrate links between local topology, cell mechanical state and cell growth, with potential roles in tissue homeostasis.

Structure and Function of Ion Pumps Studied by Atomic Force Microscopy and Gene-transfer Experiments Using Chimeric Na+/K+- and Ca2+ ATPases

1994 ◽  
pp. 264-275
Author(s):  
Kunio Takeyasu ◽  
Jose K. Paul ◽  
Mehdi Ganjeizadeh ◽  
M. Victor Lemas ◽  
Shusheng Wang ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Gene Transfer ◽  
Structure And Function ◽  
Ion Pumps ◽  
Force Microscopy ◽  
Atomic Force ◽  
And Function

Molecular-Scale Studies of Proteins at Model Biomaterial Surfaces by Atomic Force Microscopy

2001 ◽  
Vol 7 (S2) ◽  
pp. 124-125
Author(s):  
Christopher A. Siedlecki
Keyword(s):  
Atomic Force Microscopy ◽  
Tertiary Structure ◽  
Molecular Level ◽  
Biological Response ◽  
Initial Step ◽  
Protein Layer ◽  
Force Microscopy ◽  
Atomic Force ◽  
Biomaterial Surfaces ◽  
And Function

A widely accepted tenet of biomaterials research is that the initial step following contact of a synthetic material with blood is the rapid adsorption of plasma proteins. The composition of this adsorbed protein layer is dependent on a variety of factors, including the surface properties of the implant material and the nature of the adsorbing proteins, and the composition and function of this protein layer is important in the subsequent biological response and ultimately the success or failure of the implanted material. While a great amount of effort has gone into developing structure/function responses for implanted biomaterials, there is still much about the molecular level interactions to be determined. We utilized atomic force microscopy (AFM) to investigate the molecular-level interactions of proteins with model biomaterial substrates. The AFM is unique in that it offers the opportunity to characterize interfacial environments, determine material properties, measure protein/surface interaction forces, and visualize the tertiary structure of adsorbed proteins.

scholarly journals How Microbes Use Force To Control Adhesion

2020 ◽  
Vol 202 (12) ◽  
Author(s):  
Albertus Viljoen ◽  
Johann Mignolet ◽  
Felipe Viela ◽  
Marion Mathelié-Guinlet ◽  
Yves F. Dufrêne
Keyword(s):  
Single Molecule ◽  
Molecular Mechanisms ◽  
Flow Chamber ◽  
Microbial Adhesion ◽  
Single Molecule Level ◽  
Force Microscopy ◽  
Atomic Force ◽  
Adhesive Interactions ◽  
And Function ◽  
Mechanisms Of Adhesion

ABSTRACT Microbial adhesion and biofilm formation are usually studied using molecular and cellular biology assays, optical and electron microscopy, or laminar flow chamber experiments. Today, atomic force microscopy (AFM) represents a valuable addition to these approaches, enabling the measurement of forces involved in microbial adhesion at the single-molecule level. In this minireview, we discuss recent discoveries made applying state-of-the-art AFM techniques to microbial specimens in order to understand the strength and dynamics of adhesive interactions. These studies shed new light on the molecular mechanisms of adhesion and demonstrate an intimate relationship between force and function in microbial adhesins.

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