![]() ![]() This difference was explained by two different charging mechanisms: (1) deprotonation of hydroxyl groups on the surface of the metal oxide in suspension or as a thick layer, (2) adsorption of hydroxide ions on a metal surface covered by a thin oxide layer, as observed on hydrophobic surfaces. Continuous on-chip fluorescence labelling, free-flow isoelectric focusing and marker-free isoelectric point determination of proteins and peptides. For stainless steels, inconel and zircaloy, the values of isoelectric points were found to be between 2.4 and 3.0, far below the isoelectric points measured for metallic oxides constituting the alloy surface layer. Applications in a variety of fields using isoelectric point based separations are provided as well as an outlook on the field for future studies. It was found that the isoelectric points of aluminum (8.7) and dural (9.1), treated by boiling water, are close to those of hydrated aluminum oxides powders. The simulation of measurements by a model predicting the sticking coefficient based on DLVO theory was used for the determination of the isoelectric point from experimental results. The isoelectric point is the pH at which a particular molecule is electrically neutral due to the equilibrium of positive and negative charges. The concentration of polystyrene spheres with surface carboxylate groups (initially 0.5-1 mg L(-1)) in contact with metallic samples was measured as a function of pH and time by turbidimetry. All rights reserved.A set-up and a method were developed to determine the isoelectric point of metals and metallic alloys samples (stainless steels, inconel, zircaloy, aluminum and dural) by measuring the adhesion rate of negative latex particles. To illustrate the interest of the study for mAb developability purposes, ionic properties of a clinical mAb candidate (dalotuzumab) were also investigated.Ĭation exchange chromatography Charge variants Developability Imaged capillary isoelectric focusing Isoelectric points Therapeutic monoclonal antibodies mAbs.Ĭopyright © 2017 Elsevier B.V. ![]() In milk, which has a pH of about 6.6, the casein micelles have a net negative charge and are quite stable. For casein, the IEP is approximately 4.6 and it is the pH value at which acid casein is precipitated. The Multi Purpose Titrator MPT2 used in conjunction with a Zetasizer Nano instrument allows for the automatic determination of isoelectric points. That pH value is known as the isoelectric point (IEP) of the protein and is generally the pH at which the protein is least soluble. To our knowledge, this is the first study focusing on the ionic properties of a wide range of FDA and EMA approved reference mAbs, using both generic chromatographic and electrophoretic methodologies. The determination of the iso-electric point is an important parameter to help understand the stability of colloidal dispersions. A METHOD FOR DETERMINING THE ISOELECTRIC POINTS OF PROTEINS BY PLACING A DILUTE AQUEOUS SOLUTION OF THE PROTEIN IN CONTACT WITH A POROUS 96 SILICA GLASS. For neutral amino acids, the side chains are neutral and the isoelectric point is given simply by the average of the pKa values of carboxylic acid and amine. This value of surface charge is useful for understanding and predicting interactions between particles in suspension. The relative percentages of acidic and basic variants determined by cation exchange chromatography (CEX) using both salt- and pH-gradients were comprised between 15% and 30% for most mAbs and were in good agreement with each other, whereas generic icIEF seems to overestimate the amount of acidic charge variants in mAb products. Isoelectric Point Determination with Zeta Potential Analysis Isoelectric Point Measurement with the SZ-100 Autotitrator Zeta potential is the charge on a particle at the shear plane. icIEF can therefore be considered as a reference technique for such a determination. The obtained values were in good agreement with those calculated by both Vector NTI and MassLynx softwares. In this work, isoelectric points (pIs) of 23 Food and Drug Administration (FDA) and European Medicines Agency (EMA) approved mAbs were determined by imaged capillary isoelectric focusing (icIEF), and ranged from 6.1 to 9.4. Accuracy assessment for isoelectric point determination using capillary isoelectric focusing-whole column imaging detection. Despite the popularity of therapeutic monoclonal antibodies (mAbs), data relative to their ionic physico-chemical properties are very scarce in the literature. ![]()
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |