Study of the complex coacervation mechanism between the lysing enzyme from T. harzianum and polyallylamine hydrochloride.

Complex coacervation was achieved by mixing the lysing enzyme from T. harzianum (LYS) with polyallylamine hydrochloride (PAH). We show in this work that the study electrostatic complexes conformation can lead to the formation of dense complexes. We systematically investigated the effects of pH and the mass ratio on the structure and properties of the complex. The different transition phases (pHc, pHφ1, and pHφ2) have been determined using dynamic light scattering, zeta potential and turbidimetric measurements. The interpolymeric bonds may be ionic or physical, depending on the pH of the system. For a pH value of 4.9, the mixture system [LYS]/[PAH] gives raise the formation of coacervate droplets. The effects of temperature on the structure of coacervate droplets are studied by small angle light scattering (SALS).

Impact of macromolecular crowding on structure and properties of pepsin and trypsin.

The change of conformation of pepsin and trypsin in absence and presence of a high molecular crowding agent has been characterized using dynamic light scattering (DLS). Structural properties were investigated as a function of chemical denaturant concentrations, the guanidine hydrochloride (GdmCl). The results showed that Ficoll 400, macromolecular crowding, has a strong effect on the chemical denaturation process of these two proteins. The changes of measured hydrodynamic radius are attributed to the enhancement effect of the crowder agent due to the excluded volume effects. The data proved that the large size of a macromolecular crowder plays a crucial role on the conformation of a protein in its unfolded states. The values of interactions Parameter kd of complex particles and a number of proteins npr attached on the Ficoll 400 measured in different GdmCl concentrations. The effect of aging on the structure of complex are studied by small angle light scattering (SALS).

Structure and properties of native and unfolded lysing enzyme from T. harzianum: Chemical and pH denaturation.

The effect of chemical denaturants and pH on the change of the conformation of the protein Lysing Enzyme from Trichoderma Harzianum has been investigated by dynamic light scattering (DLS) and turbidimetry. Chemical denaturants are frequently used to describe the mechanisms of folding and transition states. We have analyzed the pH effect on the properties and particle size of the protein. The compaction factor CI has shown that the protein is weakly disordered. The molecular dynamics simulations confirm, at neutral pH, that the protein has a low net charge and high hydrophobicity.

Core-shell particles formed by ß-lactoglobulin microgel coated with xyloglucan.

Core-shell particles were formed by mixing in aqueous solution the neutral polysaccharide xyloglucan (XG) with microgels. The last one was obtained by heating the whey protein ß-lactoglobulin (ß-LG) in the presence of CaCl2. XG adsorbed spontaneously unto the microgels at pH<5.6. The amount of bound XG per protein was determined using a combination of centrifugation and size exclusion chromatography. It increased linearly with increasing XG concentration. The fraction of XG that adsorbed increased with decreasing pH. The formation of the XG shell inhibited large scale flocculation of the particles, that causes precipitation for naked microgels, close to their isoionic point. The thickness of the XG shell was estimated by measurement of the hydrodynamic radius using dynamic light scattering. The extent of binding depended on the pH history during mixing showing that the protein/XG complex was not in thermodynamic equilibrium.