Mechanism of interaction of hydrocalumites (Ca/Al-LDH) with methyl orange and acidic scarlet GR

The development of new materials for water purification is of universal importance. Among these types of materials are layered double hydroxides (LDHs). Non-ionic materials pose a significant problem as pollutants. The interaction of methyl orange (MO) and acidic scarlet GR (GR) adsorption on hydrocalumite (Ca/Al-LDH-Cl) were studied by X-ray diffraction (XRD), infrared spectroscopy (MIR), scanning electron microscope (SEM) and near-infrared spectroscopy (NIR). The XRD results revealed that the basal spacing of Ca/Al-LDH-MO was expanded to 2.45 nm, and the MO molecules were intercalated with a inter-penetrating bilayer model in the gallery of LDH, with 49o tilting angle. Yet Ca/Al-LDH-GR was kept the same d-value as Ca/Al-LDH-Cl. The NIR spectrum for Ca/Al-LDH-MO showed a prominent band around 5994 cm-1, assigned to the combination result of the N-H stretching vibrations, which was considered as a mark to assess MO- ion intercalation into Ca/Al-LDH-Cl interlayers. From SEM images, the particle morphology of Ca/Al-LDH-MO mainly changed to irregular platelets, with a “honey-comb” like structure. Yet the Ca/Al-LDH-GR maintained regular hexagons platelets, which was similar to that of Ca/Al-LDH-Cl. All results indicated that MO- ion was intercalated into Ca/Al-LDH-Cl interlayers, and acidic scarlet GR was only adsorped upon Ca/Al-LDH-Cl surfaces

Molecular Modifications of β-Lactoglobulin upon Exposure to High Pressure

Irreversible modifications in tertiary structure, surface hydrophobicity, and association state of \u3b2-lactoglobulin were studied after exposure to high pressure (600 and 900 MPa) of solutions of the protein at neutral pH and at different concentrations. Only minor irreversible structural modifications were evident even for treatments as intense as 15 min at 900 MPa. The occurrence of irreversible modifications was time-progressive at 600 MPa but was complete within 2 min at 900 MPa. The irreversibly modified protein was soluble, but some covalent aggregates were formed. Formation of aggregates increased with increasing protein concentration and was prevented by blocking the free thiol moiety in each \u3b2-lactoglobulin monomer. Results are discussed in light of their practical relevance, and a unifying denaturation mechanism is envisaged for \u3b2-lactoglobulin. In the proposed mechanism, release of monomers represents one of the earliest events, while association of transiently modified monomers stabilizes the denatured forms of the protein

Molecular Modifications of β-Lactoglobulin upon Exposure to High Pressure

Irreversible modifications in tertiary structure, surface hydrophobicity, and association state of β-lactoglobulin were studied after exposure to high pressure (600 and 900 MPa) of solutions of the protein at neutral pH and at different concentrations. Only minor irreversible structural modifications were evident even for treatments as intense as 15 min at 900 MPa. The occurrence of irreversible modifications was time-progressive at 600 MPa but was complete within 2 min at 900 MPa. The irreversibly modified protein was soluble, but some covalent aggregates were formed. Formation of aggregates increased with increasing protein concentration and was prevented by blocking the free thiol moiety in each β-lactoglobulin monomer. Results are discussed in light of their practical relevance, and a unifying denaturation mechanism is envisaged for β-lactoglobulin. In the proposed mechanism, release of monomers represents one of the earliest events, while association of transiently modified monomers stabilizes the denatured forms of the protein.[...

Clathrin-independent endocytosis of ubiquitinated cargos

Plasma membrane receptors can be endocytosed through clathrindependent and clathrin-independent pathways. Here, we show that the epidermal growth factor (EGF) receptor (EGFR), when stimulated with low doses of EGF, is internalized almost exclusively through the clathrin pathway, and it is not ubiquitinated. At higher concentrations of ligand, however, a substantial fraction of the receptor is endocytosed through a clathrin-independent, lipid raft-dependent route, as the receptor becomes ubiquitinated. An ubiquitination-impaired EGFR mutant was internalized through the clathrin pathway, whereas an EGFRubiquitin chimera, that can signal solely through its ubiquitin (Ub) moiety, was internalized exclusively by the non-clathrin pathway. Non-clathrin internalization of ubiquitinated EGFR depends on its interaction with proteins harboring the Ub-interacting motif, as shown through the ablation of three Ub-interacting motif-containing proteins, eps15, eps15R, and epsin. Thus, eps15s and epsin perform an important function in coupling ubiquitinated cargo to clathrin-independent internalization