I want to label 10 mg of protein with biotin. Suggestions?

One should purchase reagents separately to save money. You can purchase 5 mL Zeba columns from Pierce. The 10X Modification Buffer (without azide), is S-4000-005. This is 5 x 1.5 mL for $50. You can get the ChromaLink™ reagent in bulk (5 x 1.0 mg) if preferred, which is B-1007-105 (for the water soluble version) or (10 mg), which is Cat. No. B-1007-010. The best modification conditions:

1. Protein concentration is 5–6 mg/mL.
2. Normally 6X equivalence of linker used, MSR will be 4–4.5. If you want high MSR, just increase to 8X or 10X.
3. The 5 mL Zeba desalt spin column is good for 500–2,000 µL.
4. Use 2.5 mL 1X MB or 1X PBS to pre-equilibrate column at 1,000 x g for 2 min (three times) before desalt (desalt at 1,000 x g for 3 min). Use 15 mL tube as collection tube.