1,721,140 research outputs found
Simulated Point Mutations in the Aa -Chain of Human Fibrinogen Support a Role of the aC Domain in the Stabilization of Fibrin Gel
No full textNanoscale characterization of the biomechanical properties of collagen fibrils in the sclera
No full textWe apply the PeakForce Quantitative Nanomechanical Property Mapping (PFQNM) atomic force
microscopy mode for the investigation of regional variations in the nanomechanical properties of
porcine sclera. We examine variations in the collagen fibril diameter, adhesion, elastic modulus
and dissipation in the posterior, equatorial and anterior regions of the sclera. The mean fibril
diameter, elastic modulus and dissipation increased from the posterior to the anterior region.
Collagen fibril diameter correlated linearly with elastic modulus. Our data matches the known
macroscopic mechanical behavior of the sclera. We propose that PFQNM has significant potential in ocular biomechanics and biophysics research
CpG oligodeoxinucleotides promote phospholipase D despendent phagolysosome maturation and intracellular mycobacterial killing in M. tubercolosis infected type II alveolar epithelial cells
No full textCpG oligodeoxynucleotides have been previously shown to enhance antimycobacterial response in
human monocytes/macrophages. The present study reports evidences showing the capability of CpG oligodeoxynucleotides
to induce (i) host phospholipase D (PLD) activation, (ii) PLD dependent reactive oxygen
intermediate production, (iii) PLD dependent phagolysosome maturation and (iv) PLD dependent
intracellular mycobacterial killing in type II alveolar epithelial cells. These are the first evidences showing
that alveolar epithelial cells may represent efficient effecter cells during primary innate antimycobacterial
immune response
Physical Properties of the Zona Pellucida
No full textThe zona pellucida (ZP) is the extracellular coat that surrounds the mammalian oocyte. It forms a spherical shell of remarkably uniform thickness (5-10 mm in eutherian mammals) composed of three glycosylated proteins (ZP1, ZP2 and ZP3). Penetration of this shell by spermatozoa plays a crucial role in mammalian fertilization and any inability of spermatozoa to penetrate the ZP inevitably leads to infertility. The purpose of this work is to shed light to the three-dimensional structure of the ZP, its construction and its properties as a polymer. By means of the Atomic Force Microscopy (force-distance curves) we have determined for the first time several ZP structural properties (elasticity, plasticity,
adhesion, etc.) during the ovulatory, periovulatory and fertilized phase.
Moreover information about single polymers interactions has been obtained by means detachment experiments (pull-off curves)
Effect of the Residual Stress on Soft Sample Nanoindentation
No full textNanoindentation has recently emerged as a powerful tool for measuring nano- and microscale
mechanical properties in tissues and other biomaterials. This technique has been used to measure
the mechanical properties of microstructural features in cells, biopolymer networks and complex
biomaterials. Despite the wide use of the nanoindentation the residual stress effect in the
determination of soft samples elastic properties is still poorly explored. By using parametric finite
element analysis and atomic force spectroscopy, we determined the relationships between residual
stress and indenter geometry and how it can affect the structural response of polymeric spherical
shells flattened on a hard surface
Principal component analysis of personalized biomolecular corona data for early disease detection
No full textToday, early disease detection (EDD) is a matter of more importance than ever in medicine. Upon interaction with human plasma, nanoparticles are covered by proteins leading to formation of a biomolecular corona (BC). As the protein patterns of patients with conditions differ from those of healthy subjects, current research into technologies based on the exploitation of personalized BC patterns could be a turning point for early disease detection. Here, we present a framework based on principal component analysis of large personalized BC datasets. We comment on how principal component analysis of personalized BC data is a fundamental step towards turning the output of basic research into fast, safe and inexpensive technologies with superior prediction ability than current methods
Water hydration of biopolymers: The case of cellulose in ancient paper-a SANS study
No full textPlants, algae, and their derivatives paper, textiles, etc. are complex systems that are chiefly composed of a web of cellulose fibers. The arrangement of solvents within the polymeric structure is of great importance since cellulose degradation is strongly influenced by water accessibility. Here we show a model based on small angle neutron scattering (SANS) data able to deconvolve the scattering contributions of both polymeric structures and solvent clusters trapped along the polymeric fibers. The relevance of our model resides in the exploitation of a large number of biopolymer networks that are known to share structures similar to that of cellulose
Investigation of Zona Pellucida Hardening with Atomic Force Microscopy and Nonlinear Optimization
No full textThe Zona Pellucida (ZP) is an extracellular membrane surrounding mammalian oocytes. The so called “zona hardening” has a key role in the fertilization process as it produces a block of polyspermy also through an increase of the stiffness of the membrane. In this study, mechanical properties of the ZP membrane extracted from mature and fertilized bovine oocytes were investigated with Atomic Force Microscopy (AFM) nanoindentation measurements. Both inner and outer sides of the ZP isolated from the fertilized oocyte were characterized to gain a deeper comprehension of the mechanisms involved in the structural re-organization of the ZP membrane leading to mechanical hardening. The full understanding of the “zona-hardening” mechanisms as well as a correct estimation of ZP elastic properties is of fundamental importance as alterations of ZP represent a potential cause of infertility. This work proposes the application of a hybrid procedure combining experimental measurements, Finite Element analysis and nonlinear optimization to analyze the indentation curves. Unlike the classical Hertz theory traditionally applied to analyze AFM data, the novel methodology presented here provides a reliable derivation of the elastic properties of the ZP as it accounts for hyperelastic mechanical behavior of the membrane and nonlinearity of the finite indentation process
Wet sample confinement by superhydrophobic patterned surfaces for combined X-ray fluorescence and X-ray phase contrast imaging
No full textIn this work we propose a wet sample handling technique which enables the simultaneous collection of X-ray fluorescence (XRF) spectra and X-ray phase contrast imaging (XPCI) using a few microliters drop confined on a superhydrophobic surface. To this purpose, we fabricated and tested a superhydrophobic patterned surface entailing an hydrophilic region which leads to pinning of the drop, enabling X-ray beam effortless alignment and measuring in liquid phase. Our technique allows to acquire capillary-free XRF spectra, resulting in a significant fluorescence detection gain, which is particularly interesting for light elements. Simultaneous XPCI provides sample geometry assuring a fine control of the experimental conditions and allowing real time monitoring of the drop during measurements. As an additional advantage – after solvent evaporation – the solute is deposited on a precise spot, greatly increasing its concentration allowing further measurements, such as X-ray microanalysis and X-ray diffraction.
These results could have potential applications in the study of blood proteins, such as ferritin and low density lipoprotein, which are usually available in very limited quantity
Detection of microviscosity by using uncalibrated atomic force microscopy cantilevers
No full textIn this letter, we provide evidence that the vibrating resonance frequency of an uncalibrated atomic force microscope cantilever can be precisely related to the viscosity of the fluid in which it is immersed, independent of any knowledge of the cantilever s geometry and spring constant. Reverse geometry, density, and spring constants of a cantilever immersed in a fluid of known viscosity can be recovered with ease. The methods for monitoring viscosity we propose are of relevance to all biorheologic and microfluidic applications where functionalized cantilevers have to be used, and a simple, yet reliable nondestructive procedure is called for
- …
