High-Activity Latex Beads
|Amidinated positively charged hydrophobic latex is particularly suitable for the preparation of latex intermediates. The only surface functional group present on the particle is amidine, which is not sensitive to aggregating effects of polyvalent cations. These particles are sensitive to negatively charged contaminants of multivalent anions. Putting these latex beads in glass containers can result in aggregation due to such anions. Amidine latex microspheres should be used in low to neutral pH environments. These amidine latex beads are available in a range of sizes and surface charge densities (70-1000 Å² per charge group).|
- View All High Activity Amidine Latex Beads
- See the Protocol for Coupling of Proteins to Amidine Latex Beads by Passive Adsorption
Type ID: 7 (pKa ~5) 4% solids Hydrophobic
|Invitrogen offers carboxyl charge-stabilized hydrophobic polystyrene microspheres with only carboxyl groups present on the particle surface. The latex beads are the carboxyl analog of the sulfate latex beads. The pKa of the carboxyl group is relatively high; consequently, these particles are not suitable for work in acidic media. IDC carboxyl latex beads are available in a range of sizes and surface charge densities (70 Å² per charge group down to 3000 Å² per charge group). They may be used either for physical adsorption of antigens or antibodies, or for covalent coupling of components to the particle surface.|
Type ID: 8 4% solids Hydrophobic
These hydrophobic polystyrene latex beads possess carboxyl and sulfate groups in comparable numbers. Hydroxyl groups are also likely to be present. The latex bead has been designed for applications in which the reactivity of the carboxyl group combined with the charge stabilizing characteristics of the sulfate groups is required; in acidic media, for example. The total effective charge is pH-dependent. They are available in a range of proportions of surface charge groups to one another, and particle size.
Type ID: 1 (pKa ~2) 8% solids Hydrophobic
|These latex microspheres are stabilized by sulfate charges. In some cases, hydroxyl and carboxyl groups are also present in small amounts bound to the polymer chains. Depending upon manufacturing conditions and particle size, the surface charge density of sulfate groups ranges from about one charge group for every 200 Å² of particle surface down to one group for every 2000 Å² of surface. |
The pKa of the sulfate group is <2; consequently, the particles are stable in acidic media. Particle suspensions are stable up to almost 0.30 M univalent electrolyte concentrations and therefore may be used in media of physiological ionic strength. However, they are hydrophobic particles and will undergo aggregation in the presence of low concentrations of divalent or trivalent cations unless stabilized by a hydrophilic coating. Sulfate latex beads are suitable for calibration of particle size analysis equipment and appropriate for diagnostic test systems which rely upon physical adsorption of antigens or antibodies.