Fabrication of Nanoscale Hydrophobic Regions on Anodic Alumina for Selective Adhesion of Biologic Molecules

2003 ◽  
Vol 773 ◽  
Author(s):  
Xiefan Lin ◽  
Anthony S. W. Ham ◽  
Natalie A. Villani ◽  
Whye-Kei Lye ◽  
Qiyu Huang ◽  
...  
Keyword(s):  
Anodic Alumina ◽  
Biological Molecules ◽  
Spatial Density ◽  
Length Scale ◽  
Adhesion Sites ◽  
A Cell ◽  
Adhesive Molecules ◽  
Receptor Clusters ◽  
Molecular Bonding ◽  
Fabrication Parameters

AbstractStudies of selective adhesion of biological molecules provide a path for understanding fundamental cellular properties. A useful technique is to use patterned substrates, where the pattern of interest has the same length scale as the molecular bonding sites of a cell, in the tens of nanometer range. We employ electrochemical methods to grow anodic alumina, which has a naturally ordered pore structure (interpore spacing of 40 to 400 nm) controlled by the anodization potential. We have also developed methods to selectively fill the alumina pores with materials with contrasting properties. Gold, for example, is electrochemically plated into the pores, and the excess material is removed by backsputter etching. The result is a patterned surface with closely separated islands of Au, surrounded by hydrophilic alumina. The pore spacing, which is determined by fabrication parameters, is hypothesized to have a direct effect on the spatial density of adhesion sites. By attaching adhesive molecules to the Au islands, we are able to observe and study cell rolling and adhesion phenomena. Through the measurements it is possible to estimate the length scale of receptor clusters on the cell surface. This information is useful in understanding mechanisms of leukocytes adhesion to endothelial cells as well as the effect of adhesion molecules adaptation on transmission of extracellular forces. The method also has applications in tissue engineering, drug and gene delivery, cell signaling and biocompatibility design.

scholarly journals Length-scale effect in stability problems for thin biperiodic cylindrical shells: extended tolerance modelling

2020 ◽  
Author(s):  
B. Tomczyk ◽  
M. Gołąbczak ◽  
A. Litawska ◽  
A. Gołąbczak
Keyword(s):  
Scale Effect ◽  
Cylindrical Shells ◽  
Length Scale ◽  
Stability Problems ◽  
Constant Coefficients ◽  
A Cell ◽  
Circular Cylindrical Shells ◽  
Tolerance Modelling ◽  
Tolerance Model ◽  
Shell Equations

Abstract Thin linearly elastic Kirchhoff–Love-type circular cylindrical shells of periodically micro-inhomogeneous structure in circumferential and axial directions (biperiodic shells) are investigated. The aim of this contribution is to formulate and discuss a new averaged nonasymptotic model for the analysis of selected stability problems for these shells. This, so-called, general nonasymptotic tolerance model is derived by applying a certain extended version of the known tolerance modelling procedure. Contrary to the starting exact shell equations with highly oscillating, noncontinuous and periodic coefficients, governing equations of the tolerance model have constant coefficients depending also on a cell size. Hence, the model makes it possible to investigate the effect of a microstructure size on the global shell stability (the length-scale effect).

scholarly journals Aster migration determines the length scale of nuclear separation in the Drosophila syncytial embryo

2012 ◽  
Vol 197 (7) ◽  
pp. 887-895 ◽  
Author(s):  
Ivo A. Telley ◽  
Imre Gáspár ◽  
Anne Ephrussi ◽  
Thomas Surrey
Keyword(s):  
Early Embryo ◽  
Length Scale ◽  
Free System ◽  
Nuclear Separation ◽  
A Cell ◽  
Distinct Distance ◽  
Spindle Elongation ◽  
Insect Embryos ◽  
Microtubule Aster

In the early embryo of many species, comparatively small spindles are positioned near the cell center for subsequent cytokinesis. In most insects, however, rapid nuclear divisions occur in the absence of cytokinesis, and nuclei distribute rapidly throughout the large syncytial embryo. Even distribution and anchoring of nuclei at the embryo cortex are crucial for cellularization of the blastoderm embryo. The principles underlying nuclear dispersal in a syncytium are unclear. We established a cell-free system from individual Drosophila melanogaster embryos that supports successive nuclear division cycles with native characteristics. This allowed us to investigate nuclear separation in predefined volumes. Encapsulating nuclei in microchambers revealed that the early cytoplasm is programmed to separate nuclei a distinct distance. Laser microsurgery revealed an important role of microtubule aster migration through cytoplasmic space, which depended on F-actin and cooperated with anaphase spindle elongation. These activities define a characteristic separation length scale that appears to be a conserved property of developing insect embryos.

scholarly journals Endothelin receptors: what's new and what do we need to know?

2010 ◽  
Vol 298 (2) ◽  
pp. R254-R260 ◽  
Author(s):  
Stephanie W. Watts
Keyword(s):  
Biological Effect ◽  
Receptor Agonist ◽  
Biological Molecules ◽  
Endothelin Receptors ◽  
Receptor Interaction ◽  
Pharmacological Studies ◽  
Receptor Pharmacology ◽  
A Cell ◽  
And Function ◽  
Receptor Family

Receptors are at the heart of how a molecule transmits a signal to a cell. Two receptor classes for endothelin (ET) are recognized, the ETAand ETBreceptors. Intriguing questions have arisen in the field of ET receptor pharmacology, physiology, and function. For example, a host of pharmacological studies support the interaction of the ETAand ETBreceptor in tissues (veins, arteries, bronchus, arterioles, esophagus), but yet few have been able to demonstrate direct ETA/ETBreceptor interaction. Have we modeled this interaction wrong? Do we have a truly selective ETAreceptor agonist such that we could selectively stimulate this important receptor? What can we learn from the recent phylogenic studies of the ET receptor family? Have we adequately addressed the number of biological molecules with which ET can interact to exert a biological effect? Recent mass spectrometry studies in our laboratory suggest that ET-1 interacts with other hereto unrecognized proteins. Biased ligands (ligands at the same receptor that elicit distinct signaling responses) have been discovered for other receptors. Do these exist for ET receptors and can we take advantage of this possibility in drug design? These and other questions will be posed in this minireview on topics on ET receptors.

scholarly journals The Impact of Elastic Deformations of the Extracellular Matrix on Cell Migration

2020 ◽  
Vol 82 (4) ◽  
Author(s):  
A. A. Malik ◽  
B. Wennberg ◽  
P. Gerlee
Keyword(s):  
Extracellular Matrix ◽  
Cell Migration ◽  
Human Cancer ◽  
Matrix Stiffness ◽  
Human Cancer Cells ◽  
Adhesion Sites ◽  
The Matrix ◽  
A Cell ◽  
Necessary And Sufficient ◽  
The Impact

Abstract The mechanical properties of the extracellular matrix, in particular its stiffness, are known to impact cell migration. In this paper, we develop a mathematical model of a single cell migrating on an elastic matrix, which accounts for the deformation of the matrix induced by forces exerted by the cell, and investigate how the stiffness impacts the direction and speed of migration. We model a cell in 1D as a nucleus connected to a number of adhesion sites through elastic springs. The cell migrates by randomly updating the position of its adhesion sites. We start by investigating the case where the cell springs are constant, and then go on to assuming that they depend on the matrix stiffness, on matrices of both uniform stiffness as well as those with a stiffness gradient. We find that the assumption that cell springs depend on the substrate stiffness is necessary and sufficient for an efficient durotactic response. We compare simulations to recent experimental observations of human cancer cells exhibiting durotaxis, which show good qualitative agreement.

scholarly journals Integrating multiple ‘omics’ analysis for microbial biology: application and methodologies

Microbiology ◽  
2010 ◽  
Vol 156 (2) ◽  
pp. 287-301 ◽  
Author(s):  
Weiwen Zhang ◽  
Feng Li ◽  
Lei Nie
Keyword(s):  
Cellular Systems ◽  
Biological Molecules ◽  
Omics Analysis ◽  
Online Databases ◽  
Quantitative Monitoring ◽  
Integrated Omics ◽  
Genomic Scale ◽  
A Cell ◽  
Micro Organisms ◽  
Microbial Systems

Recent advances in various ‘omics’ technologies enable quantitative monitoring of the abundance of various biological molecules in a high-throughput manner, and thus allow determination of their variation between different biological states on a genomic scale. Several popular ‘omics’ platforms that have been used in microbial systems biology include transcriptomics, which measures mRNA transcript levels; proteomics, which quantifies protein abundance; metabolomics, which determines abundance of small cellular metabolites; interactomics, which resolves the whole set of molecular interactions in cells; and fluxomics, which establishes dynamic changes of molecules within a cell over time. However, no single ‘omics’ analysis can fully unravel the complexities of fundamental microbial biology. Therefore, integration of multiple layers of information, the multi-‘omics’ approach, is required to acquire a precise picture of living micro-organisms. In spite of this being a challenging task, some attempts have been made recently to integrate heterogeneous ‘omics’ datasets in various microbial systems and the results have demonstrated that the multi-‘omics’ approach is a powerful tool for understanding the functional principles and dynamics of total cellular systems. This article reviews some basic concepts of various experimental ‘omics’ approaches, recent application of the integrated ‘omics’ for exploring metabolic and regulatory mechanisms in microbes, and advances in computational and statistical methodologies associated with integrated ‘omics’ analyses. Online databases and bioinformatic infrastructure available for integrated ‘omics’ analyses are also briefly discussed.

scholarly journals Sticking around: Optimal cell adhesion patterning for energy minimization and substrate mechanosensing

2020 ◽  
Author(s):  
Josephine Solowiej-Wedderburn ◽  
Carina M. Dunlop
Keyword(s):  
Mechanical Properties ◽  
Focal Adhesion ◽  
Cell Model ◽  
Stress Component ◽  
Focal Adhesions ◽  
Cell Stiffness ◽  
Adhesion Sites ◽  
Cell Shapes ◽  
A Cell ◽  
Sense And Respond

AbstractCell mechanotransduction, in which cells sense and respond to the physical properties of their micro-environments, is proving fundamental to understanding cellular behaviours across biology. Tissue stiffness (Young’s modulus) is typically regarded as the key control parameter and bioengineered gels with defined mechanical properties have become an essential part of the toolkit for interrogating mechanotransduction. We here, however, show using a mechanical cell model that the effective substrate stiffness experienced by a cell depends not just on the engineered mechanical properties of the substrate but critically also on the particular arrangement of adhesions between cell and substrate. In particular, we find that cells with different adhesion patterns can experience two different gel stiffnesses as equivalent and will generate the same mean cell deformations. For small adhesive patches, which mimic experimentally observed focal adhesions, we demonstrate that the observed dynamics of adhesion growth and elongation can be explained by energy considerations. Significantly we show different focal adhesions dynamics for soft and stiff substrates with focal adhesion growth not preferred on soft substrates consistent with reported dynamics. Equally, fewer and larger adhesions are predicted to be preferred over more and smaller, an effect enhanced by random spot placing with the simulations predicting qualitatively realistic cell shapes in this case. The model is based on a continuum elasticity description of the cell and substrate system, with an active stress component capturing cellular contractility. This work demonstrates the necessity of considering the whole cell-substrate system, including the patterning of adhesion, when investigating cell stiffness sensing, with implications for mechanotransductive control in biophysics and tissue engineering.Author summaryCells are now known to sense the mechanical properties of their tissue micro-environments and use this as a signal to control a range of behaviours. Experimentally, such cell mechanotransduction is mostly investigated using carefully engineered gel substrates with defined stiffness. Here we show, using a model integrating active cellular contractility with continuum mechanics, that the way in which a cell senses its environment depends critically not just on the stiffness of the gel but also on the spatial patterning of adhesion sites. In this way, two gels of substantially different stiffnesses can be experienced by the cell as similar, if the adhesions are located differently. Exploiting this insight, we demonstrate that it is energetically favourable for small adhesions to grow and elongate on stiff substrates but that this is not the case on soft substrates. This is consistent with experimental observations that nascent adhesions only mature to stable focal adhesion (FA) sites on stiff substrates where they also grow and elongate. These focal adhesions (FAs) have been the focus of work on mechanotransduction. However, our paper demonstrates that there is a fundamental need to consider the combined cell and micro-environment system moving beyond a focus on individual FAs.

scholarly journals The Art of Mast Cell Adhesion

Cells ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 2664
Author(s):  
Joanna Pastwińska ◽  
Paulina Żelechowska ◽  
Aurelia Walczak-Drzewiecka ◽  
Ewa Brzezińska-Błaszczyk ◽  
Jarosław Dastych
Keyword(s):  
Cell Adhesion ◽  
Current Knowledge ◽  
Living Organism ◽  
Cellular Mechanisms ◽  
Cellular Processes ◽  
Adhesion Sites ◽  
Inflammatory Processes ◽  
Adhesive Molecules ◽  
Adhesive Proteins ◽  
Insight Into

Cell adhesion is one of the basic phenomena occurring in a living organism, affecting many other processes such as proliferation, differentiation, migration, or cell viability. Mast cells (MCs) are important elements involved in defending the host against various pathogens and regulating inflammatory processes. Due to numerous mediators, they are contributing to the modulation of many basic cellular processes in a variety of cells, including the expression and functioning of different adhesive molecules. They also express themselves many adhesive proteins, including ICAM-1, ICAM-3, VCAM-1, integrins, L-selectin, E-cadherin, and N-cadherin. These molecules enable MCs to interact with other cells and components of the extracellular matrix (ECM), creating structures such as adherens junctions and focal adhesion sites, and triggering a signaling cascade. A thorough understanding of these cellular mechanisms can create a better understanding of MC biology and reveal new goals for MC targeted therapy. This review will focus on the current knowledge of adhesion mechanisms with the involvement of MCs. It also provides insight into the influence of MCs or MC-derived mediators on the adhesion molecule expression in different cells.

scholarly journals Emerging strategies for the identification of protein–metabolite interactions

2019 ◽  
Vol 70 (18) ◽  
pp. 4605-4618 ◽  
Author(s):  
Marcin Luzarowski ◽  
Aleksandra Skirycz
Keyword(s):  
Ligand Binding ◽  
Small Molecules ◽  
Protein Interactions ◽  
Technological Progress ◽  
Molecular Complexes ◽  
Biological Molecules ◽  
Protein Protein Interactions ◽  
Binding Domains ◽  
Protein Receptors ◽  
A Cell

AbstractInteractions between biological molecules enable life. The significance of a cell-wide understanding of molecular complexes is thus obvious. In comparison to protein–protein interactions, protein–metabolite interactions remain under-studied. However, this has been gradually changing due to technological progress. Here, we focus on the interactions between ligands and receptors, the triggers of signalling events. While the number of small molecules with proven or proposed signalling roles is rapidly growing, most of their protein receptors remain unknown. Conversely, there are numerous signalling proteins with predicted ligand-binding domains for which the identities of the metabolite counterparts remain elusive. Here, we discuss the current biochemical strategies for identifying protein–metabolite interactions and how they can be used to characterize known metabolite regulators and identify novel ones.

Artificial Viscosity and the Simulation of Fragmentation

1982 ◽  
Vol 4 (4) ◽  
pp. 378-379 ◽  
Author(s):  
R.A. Gingold ◽  
J.J. Monaghan
Keyword(s):  
Angular Momentum ◽  
Donor Cell ◽  
Artificial Viscosity ◽  
Momentum Transport ◽  
Length Scale ◽  
Angular Momentum Transport ◽  
Truncation Errors ◽  
A Cell ◽  
Axisymmetric Problems ◽  
The Difference

Recent numerical experiments (Norman et al. 1980), which simulate the axisymmetric collapse of a rotating, self gravitating cloud, show that spurious angular momentum transport can seriously affect the evolution of the cloud. In particular, it may determine if a ring-like density enhancement will occur. The spurious angular momentum transport can arise either from an explicit artificial viscosity, which might be required if shocks occur, or from an implicit viscosity due to truncation errors in the difference equation approximation to the exact equations. In donor cell schemes like those used by Tohline (1980) and Boss (1980) spurious angular momentum transport is due to truncation errors in the difference equations. For axisymmetric problems the errors are usually not serious since the typical length of a cell in the computational grid is very much less than the length scale of the cloud. We would expect the errors to be much greater when fragmentation occurs because the length scale of a fragment may only be comparable to that of three or four cells.

Intracellular stress tomography reveals stress focusing and structural anisotropy in cytoskeleton of living cells

2003 ◽  
Vol 285 (5) ◽  
pp. C1082-C1090 ◽  
Author(s):  
Shaohua Hu ◽  
Jianxin Chen ◽  
Ben Fabry ◽  
Yasushi Numaguchi ◽  
Andrew Gouldstone ◽  
...  
Keyword(s):  
Fluorescent Protein ◽  
Apical Cell ◽  
Adherent Cell ◽  
Apical Surface ◽  
Structural Anisotropy ◽  
Synchronous Detection ◽  
Adhesion Sites ◽  
Detection Approach ◽  
Phase Lags ◽  
A Cell

We describe a novel synchronous detection approach to map the transmission of mechanical stresses within the cytoplasm of an adherent cell. Using fluorescent protein-labeled mitochondria or cytoskeletal components as fiducial markers, we measured displacements and computed stresses in the cytoskeleton of a living cell plated on extracellular matrix molecules that arise in response to a small, external localized oscillatory load applied to transmembrane receptors on the apical cell surface. Induced synchronous displacements, stresses, and phase lags were found to be concentrated at sites quite remote from the localized load and were modulated by the preexisting tensile stress (prestress) in the cytoskeleton. Stresses applied at the apical surface also resulted in displacements of focal adhesion sites at the cell base. Cytoskeletal anisotropy was revealed by differential phase lags in X vs. Y directions. Displacements and stresses in the cytoskeleton of a cell plated on poly-l-lysine decayed quickly and were not concentrated at remote sites. These data indicate that mechanical forces are transferred across discrete cytoskeletal elements over long distances through the cytoplasm in the living adherent cell.

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