Juan Vicente Méndez-Méndez

Damage Mechanisms in AISI 304 Borided Steel: Scratch and Daimler-Benz Adhesion Tests

In this study, damage mechanisms in the FeB/Fe2B coatings formed on the surface of AISI 304 steel are determined by adhesion tests. First, the boriding of the AISI 304 steel was carried out through the powder-pack method at 1223 K in the range from 2-10 h of exposure time. After treatment, Berkovich depth-sensing indentation test were conducted; the result showed tensil and compressive residual stresses in the FeB and Fe2B, respectively. The adhesion of borided steels was evaluated by the Daimler-Benz Rockwell-C and scratch test. Based on the scratch tracks, the chipping was the predominant mechanism at 2 and 6 h, with critical loads of 35 and 43 N, respectively; while spalliation was determined at 27 N for 10 h. Also, hertzian and tensil cracks, buckling and compressive delamination were determined in the AISI 304 borided steel by scanning electron microscope.

Virtual and In Vitro Screens Reveal a Potential Pharmacophore that Avoids the Fibrillization of Aβ1–42

Among the multiple factors that induce Alzheimer’s disease, aggregation of the amyloid β peptide (Aβ) is considered the most important due to the ability of the 42-amino acid Aβ peptides (Aβ1–42) to form oligomers and fibrils, which constitute Aβ pathological aggregates. For this reason, the development of inhibitors of Aβ1–42 pathological aggregation represents a field of research interest. Several Aβ1–42 fibrillization inhibitors possess tertiary amine and aromatic moieties. In the present study, we selected 26 compounds containing tertiary amine and aromatic moieties with or without substituents and performed theoretical studies that allowed us to select four compounds according to their free energy values for Aβ1–42 in α-helix (Aβ-α), random coil (Aβ-RC) and β-sheet (Aβ-β) conformations. Docking studies revealed that compound 5 had a higher affinity for Aβ-α and Aβ-RC than the other compounds. In vitro, this compound was able to abolish Thioflavin T fluorescence and favored an RC conformation of Aβ1–42 in circular dichroism studies, resulting in the formation of amorphous aggregates as shown by atomic force microscopy. The results obtained from quantum studies allowed us to identify a possible pharmacophore that can be used to design Aβ1–42 aggregation inhibitors. In conclusion, compounds with higher affinity for Aβ-α and Aβ-RC prevented the formation of oligomeric species.

The shift in GH3 cell shape and cell motility is dependent on MLCK and ROCK

ABSTRACT Cytoskeletal organization, actin‐myosin contractility and the cell membrane together regulate cell morphology in response to the cell environment, wherein the extracellular matrix (ECM) is an indispensable component. Plasticity in cell shape enables cells to adapt their migration mode to their surroundings. GH3 endocrine cells respond to different ECM proteins, acquiring different morphologies: a rounded on collagen I‐III (C I‐III) and an elongated on collagen IV (C IV). However, the identities of the molecules that participate in these responses remain unknown. Considering that actin‐myosin contractility is crucial to maintaining cell shape, we analyzed the participation of MLCK and ROCK in the acquisition of cell shape, the generation of cellular tension and the cell motility mode. We found that a rounded shape with high cortical tension depends on MLCK and ROCK, whereas in cells with an elongated shape, MLCK is the primary protein responsible for cell spreading. Further, in cells with a slow and directionally persistent motility, MLCK predominates, while rapid and erratic movement is ROCK‐dependent. This behavior also correlates with GTPase activation. Cells on C I‐III exhibited higher Rho‐GTPase activity than cells on C IV and vice versa with Rac‐GTPase activity, showing a plastic response of GH3 cells to their environment, leading to the generation of different cytoskeleton and membrane organizations and resulting in two movement strategies, rounded and fibroblastoid‐like.

Polymerization of 10,16-Dihydroxyhexadecanoic Acid, Main Monomer of Tomato Cuticle, Using the Lewis Acidic Ionic Liquid Choline Chloride·2ZnCl2

10,16-dihydroxyhexadecanoic acid, main monomer of the tomato cuticle obtained from agro-residual wastes, was polymerized using (choline chloride.2ZnCl2) ionic liquid as catalyst at three different temperatures (80, 90 and 100 °C). The resulting polyesters obtained under these conditions were insoluble in most of the organic solvents and showed different physicochemical properties. While at 80 °C polymers were obtained as powder, at higher temperature they were found in viscous consistency. According with the CP MAS 13C NMR and FTIR-ATR analysis, polymers showed a linear structure with an increasing degree of esterification in position C-10. Polyesters were analyzed by means of differential scanning calorimetry (DSC), atomic force microscopy (AFM) and X ray diffraction (small- and wide-angle scattering, SWAXS) techniques.

Indentation Technique: Overview and Applications in Food Science

Indentation technique also known as instrumented indentation testing (IIT) has been widely used for characterization of mechanical properties of materials of different nature and different levels. This technique has been mostly used in the field of metallic materials, although in recent years its use has expanded to the biological area, and recently has been also used in the area of food science. The aim of this chapter is to show the general aspects of the indentation technique such as definition, measurement methods and data analysis, measured mechanical parameters, and examples of using the indentation technique in biological materials and specifically in food science. The main contribution of this chapter is to offer the reader a basic understanding of the technique and to show its scope for its possible application in the characterization of food mechanical properties.

Role of α-Dystrobrevin in the differentiation process of HL-60 cells

&NA; The &agr;‐Dystrobrevin gene encodes at least five different protein isoforms, expressed in diverse tissues. The &agr;‐Dystrobrevin‐1 isoform (&agr;‐Db‐1) is a member of the cytoplasmic dystrophin‐associated protein complex, which has a C‐terminal extension comprising at least three tyrosine residues susceptible to phosphorylation in vivo. We previously described &agr;‐Db in stem‐progenitor cells and blood neutrophils as playing a scaffolding role and, in association with kinesin and microtubules, &agr;‐Db promotes platelet‐granule trafficking. Additionally, the microtubules must establish a balanced interaction with the lamina A/C network for appropriate nuclear morphology. Considering that the most outstanding feature during neutrophil differentiation is nuclei lobulation, we hypothesized that &agr;‐Db might possess a pivotal function during the neutrophil differentiation process. Western Blot (WB) and confocal microscope assays evidenced a differential pattern expression and a subcellular redistribution of &agr;‐Db in neutrophils derived from HL‐60 cells. At the end of the differentiation process, we detected an important diminution in the expression of tubulin, kinesin, and &agr;‐Db‐1. Knockdown of &agr;‐Db prevented nuclei lobulation, increased Lamin A/C and syne1 expression and augmented the roughness of derived neutrophil membrane and disturbed filopodia assembly. Our results suggest that HL‐60 cells undergo extensive cytoskeletal reorganization including &agr;‐Db in order to possess lobulated nuclei when they further differentiate into neutrophils. Graphical abstract Figure. No Caption available. Highlights&agr;‐Db is downexpressed in HL‐60 cells induced into neutrophils with DMSO.&agr;‐Db‐1 knockdown prevented nuclei lobulation, increased lamin A/C, and syne1 expression.&agr;‐Db‐1 depletion augmented actin‐F and the roughness of derived neutrophil membrane.

Biofunctionality of native and nano-structured blue corn starch in prediabetic Wistar rats

ABSTRACT The biofunctionality of native and nanostructured starch obtained from blue corn was evaluated on prediabetic Wistar rats. The surface of both types of starch was analyzed by atomic force microscopy (AFM). Total polyphenols content, antioxidant activity and digestibility were also evaluated. Prediabetes was induced by feeding a diet high in fat, carbohydrates and the administration of streptozotocin. Experimental design included a control group, prediabetic group and two prediabetic groups, one supplemented with native starch and the other with nanostructured starch. AFM analysis showed nano-cavities <5 nm in nanostructured starch. Nanostructured starch also had a higher content of total polyphenols, higher antioxidant activity and higher percentage of slow digestibility starch compared to native starch. Glucose, triglycerides 34 and insulin in the plasma increased significantly in the prediabetic group. Nanostructured starch administration decreased the levels of glucose and insulin in the plasma and therefore has potential as functional ingredient.

Tools for the Study of Nanostructures

In this chapter, some of the most used microscopy techniques for analyzing the structure of biological materials at the micro- and nanoscale will be presented. These techniques are usually applied looking for the changes that promote the arise of new properties and phenomena that emerge at these scales, hence, the purpose of this chapter is to provide the reader with examples of the application of different types of microscopy techniques usually used to characterize food items.