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| Product Name | Tosyl-Activated Magnetic Beads |
| Catalog No. | MAGBEA-0018 |
| Description | Tosyl (p-toluenesulfonyl)-activated superparamagnetic beads for the direct, covalent coupling of proteins, antibodies, and other biomolecules through primary amine or sulfhydryl groups under mild physiological conditions. The tosyl-reactive group enables efficient ligand immobilization without carbodiimide activation reagents, providing a simple one-step coupling protocol. The stable secondary amine or thioether bonds formed resist hydrolysis and ligand leaching under a wide range of buffer and pH conditions, making these beads suitable for reusable affinity matrices and immunodiagnostic reagents. |
| Intended Use | Covalent immobilization of proteins, antibodies, antigens, enzymes, and peptides for affinity purification, immunoprecipitation, diagnostic immunoassay solid phases, enzyme reactor construction, and custom affinity matrix preparation. |
| Principle / Technology | The bead surface is functionalized with reactive p-toluenesulfonyl (tosyl) ester groups that undergo nucleophilic displacement by primary amines (to form stable secondary amine bonds) or sulfhydryl groups (to form thioether bonds). Coupling proceeds at near-neutral to mildly alkaline pH without pre-activation. The tosyl group acts as a good leaving group, facilitating efficient coupling. Residual unreacted tosyl groups are readily quenched with ethanolamine or Tris buffer after coupling. The resultant covalent bonds are stable to high salt, denaturants, and a broad pH range (pH 2-12). |
| Detection Method | DLS for bead size; TNBS or UV280 difference for protein coupling density and efficiency; BCA assay for total immobilized protein; SDS-PAGE for coupling verification; enzyme activity assay (HRP, ALP) for retained activity; zeta potential for surface charge; ligand leaching assay |
| Sample Type | Proteins (antibodies, enzymes, Protein A/G, streptavidin, BSA, ovalbumin), peptides, amino-modified oligonucleotides, and any biomolecule containing accessible primary amine or sulfhydryl groups; amines on lysine residues and N-termini are primary coupling targets; optimal for ligands stable at pH 8.0-9.5 during coupling |
| Performance Range / Specifications | Bead diameter: 1-3 µm; tosyl group density: 0.1-0.5 mmol/g; protein coupling capacity: 5-30 mg protein per g beads (ligand-dependent); coupling efficiency: 50-90% (dependent on protein concentration and pH); coupling time: 2-24 hours at room temperature or 4°C; non-specific binding after quenching: <2%; ligand leaching after covalent coupling: <1% over 6 months; magnetic separation: <10 seconds |
| Sensitivity / LOD | Effective coupling of proteins at concentrations as low as 0.1 mg/mL; coupling detectable by change in bead zeta potential or protein assay; reproducible coupling densities from 1-30 mg/g depending on protein size and concentration |
| Specificity | Specific covalent coupling to primary amines and sulfhydryl groups; minimal coupling to hydroxyl, carboxyl, or amide groups; efficient quenching prevents further reactivity; coupled ligands retain recognition specificity (antibody-antigen binding retained >80%); enzyme activity of coupled HRP and ALP retained >60% |
| Reaction Conditions / Protocol | Wash beads with coupling buffer (0.1 M borate buffer pH 9.5 or 0.1 M phosphate pH 8.0); add protein solution (1-10 mg/mL in coupling buffer); incubate at room temperature for 2-4 hours or at 4°C for 16-24 hours with end-over-end rotation; magnetically separate; wash beads; quench residual tosyl groups with 0.1 M ethanolamine pH 8.0 or 0.1 M Tris-HCl pH 8.0 for 2 hours at room temperature; wash extensively with PBS; resuspend in storage buffer; verify coupling by protein assay of pre- and post-coupling supernatant; total protocol: 4-24 hours |
| Components / Formulation | Tosyl-activated superparamagnetic beads, lyophilized or as 20 mg/mL slurry in acetone or dry organic solvent (moisture-sensitive); supplied under inert gas in sealed container; coupling buffers and quenching reagents not included |
| Storage Conditions | 2-8°C in sealed, moisture-free container; protect from moisture (tosyl groups hydrolyze in aqueous solution—half-life approximately 8-12 hours at pH 8.0 at room temperature); for slurry in organic solvent, store under nitrogen or argon after opening; lyophilized format: store with desiccant; use immediately after suspending in coupling buffer |
| Shelf Life | 24 months for lyophilized format at 2-8°C (moisture-free); 12 months for organic solvent slurry at 2-8°C; tosyl group hydrolysis monitored by reactivity assay; once resuspended in aqueous coupling buffer, use within 8-12 hours; coupled beads stable 6-12 months in PBS/azide at 2-8°C |
| Package Specifications | 100 mg, 500 mg, 1 g, 5 g lyophilized powder; 1 mL, 5 mL organic solvent slurry; sufficient for 10-100 coupling reactions; bulk packaging available; moisture-protective packaging with desiccant |
| Product Form | White to off-white powder (lyophilized) or pale suspension in organic solvent; free-flowing powder; rapid resuspension in coupling buffer; characteristic tosyl odor; moisture-sensitive appearance change (clumping indicates hydrolysis) |
| Quality Control | Per lot: tosyl group density (titration or UV), protein coupling capacity with BSA and IgG standards, coupling efficiency, residual tosyl groups after quenching, non-specific binding, ligand leaching (6-month stability study), endotoxin, moisture content (lyophilized), sterility, particle size; organic solvent purity verified for slurry format |
| Key Features | One-step covalent coupling without activation reagents; mild coupling pH compatible with sensitive proteins; stable secondary amine/thioether linkages; low ligand leaching; high coupling density; suitable for manufacturing of reusable affinity matrices; extended shelf life in lyophilized format |
| Purity | Tosyl group density: 0.1-0.5 mmol/g; endotoxin <0.1 EU/mg; coupling efficiency validated with BSA and IgG; moisture content <1% (lyophilized); coupling capacity per lot specified |
| Concentration | Lyophilized: 100% solids; slurry: 20 mg/mL; coupling capacity 5-30 mg protein/g beads (protein-dependent); exact specifications per lot |
| Activity / Unit Definition | Tosyl density: 0.1-0.5 mmol/g; BSA coupling: 10-20 mg/g; IgG coupling: 5-15 mg/g; coupled IgG retains >80% antigen binding; coupled HRP retains >60% enzymatic activity; quenching efficiency >99% residual tosyl inactivated |
| Molecular Weight | Tosyl group: ~155 g/mol (p-toluenesulfonyl, CH3C6H4SO2-); leaving group molecular weight upon displacement: 155 + 1 (protonated tosylic acid) |
| Source / Origin | Fully synthetic; polymer-magnetite beads are surface-activated with tosyl chloride under anhydrous conditions; p-toluenesulfonyl chloride is synthetic organic reagent; all chemicals are analytical grade; no animal-derived components; manufactured under controlled atmosphere |
| pH Range / Optimal pH | Coupling: pH 7.5-10.0 (optimal 8.0-9.5 for amines); tosyl hydrolysis accelerates below pH 7 and above pH 11; coupled ligand stability: pH 2-12 (secondary amine bond); bead integrity: pH 2-13; quenching: pH 7.5-9.0 |
| Shipping Conditions | Ambient temperature with desiccant for lyophilized format; organic solvent slurry may require flammable liquid shipping classification (acetone typically); moisture-protective packaging essential; expedited shipping to minimize atmospheric moisture exposure |
| Expiration Date / Stability | 24 months lyophilized at 2-8°C (moisture-free); tosyl reactivity >90% retained; moisture-sensitive—degradation accelerated by humidity; after opening, use immediately or repack under inert gas; coupled beads: 6-12 months in PBS/azide |
| Regulatory / Compliance | For research use and manufacturing; raw material for IVD component preparation; ISO 9001 manufacturing; certificate of analysis with lot-specific reactivity data; acetone-containing slurry may be regulated for shipping; SDS includes organic solvent hazard information |
| Compatibility | Coupling buffers: borate (0.05-0.2 M, pH 8.5-9.5), phosphate (0.05-0.2 M, pH 7.5-8.5), carbonate (0.05-0.2 M, pH 9.0-9.5); avoid Tris and other amine-containing buffers during coupling (competes with protein); compatible with NaCl up to 1 M; avoid azide (amines compete); coupled beads compatible with wide range of application buffers |
| Recommended Buffer System | Coupling: 0.1 M sodium borate pH 9.5 or 0.1 M sodium phosphate pH 8.0, with 0.15-0.5 M NaCl optional; quenching: 0.1 M ethanolamine in PBS pH 8.0 or 0.1 M Tris-HCl pH 8.0; storage of coupled beads: PBS pH 7.4 with 0.02% NaN3; lyophilized beads stored moisture-free with desiccant |
| Application Notes / Precautions | Protein must be free of amine-containing buffer components before coupling; dialyze or desalt protein into non-amine coupling buffer; higher protein concentration during coupling increases density; extend coupling time for large proteins (>150 kDa); coupling at 4°C overnight reduces protein denaturation risk; for glycoproteins, periodate oxidation allows oriented coupling through carbohydrate moieties; quench thoroughly—residual tosyl groups cause non-specific binding; monitor coupling efficiency by UV280 difference of pre/post supernatant |
| Batch-to-Batch Consistency | Tosyl density CV <15%; BSA coupling capacity CV <12%; coupling efficiency >80% all lots; moisture content within specification per lot; each lot validated with BSA and IgG coupling standards; reactivity shelf life verified |
For research use only, not for clinical use.
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