Materials and Equipment

Before beginning, gather the following materials:

• Human IgG reagent (Aladdin Scientific, SKU: Ab170213B) — confirm lot number and retrieve the corresponding Certificate of Analysis (COA) for the exact concentration.
• Appropriate buffer for your application (e.g., PBS pH 7.4, TBS, or assay-specific diluent).
• Calibrated micropipettes and sterile, low-protein-binding tips.
• Low-protein-binding microcentrifuge tubes (1.5 mL or 0.5 mL).
• Microcentrifuge (optional, for clarification).
• Ice bucket or cooling rack to keep protein cold during handling.
• Spectrophotometer or BCA/Bradford protein assay kit (if independent concentration verification is required).

Preparation and Dilution Procedure

Follow these steps to prepare working concentrations of Human IgG:

1. Retrieve and inspect: Remove the Human IgG vial from storage. Visually inspect for particulates or discoloration. If the product has been stored frozen, allow it to thaw slowly on ice or at 2–8 °C.
2. Verify concentration: Consult the lot-specific COA for the confirmed stock concentration. For lots P230001659, P240013530, P240015375, P250016160, and P250016867, the stock concentration is 16.8 mg/mL. All other lots: refer to the COA shipped with your order.
3. Calculate required dilution: Determine the target working concentration for your assay. Apply the dilution formula: C₁V₁ = C₂V₂. For example, to prepare 1 mL of 1 mg/mL working solution from a 16.8 mg/mL stock: add 59.5 µL of stock to 940.5 µL of diluent buffer.
4. Mix gently: Pipette up and down gently or briefly vortex at low speed. Do NOT shake vigorously, as this may denature the protein and cause aggregation.
5. Clarify if needed: Centrifuge at 10,000 × g for 5 minutes at 4 °C to remove any aggregates before use.
6. Aliquot unused stock: To minimize freeze-thaw cycles, aliquot the remaining stock into single-use volumes and store as specified on the COA.

Application Guidelines

Human IgG from Aladdin Scientific is suitable for a variety of research applications. Representative uses include:

• Isotype control: Use at the same concentration and under identical conditions as the primary antibody in flow cytometry, immunohistochemistry (IHC), or ELISA to assess non-specific background binding.
• Blocking agent: Include Human IgG in blocking buffer to saturate Fc receptors or non-specific protein-binding sites on cells or membranes, reducing background in immunoassays.
• ELISA standard: Prepare a serial dilution series of Human IgG (e.g., 2-fold or 3-fold dilutions) to generate a standard curve for quantifying IgG concentrations in test samples.
• Western blot: Load known quantities as a molecular weight marker or positive control for anti-human IgG secondary antibodies.
• Functional assays: Use as a non-specific IgG control to assess antibody-independent effects in cell-based assays.

Note: Optimal working concentrations may vary by application and must be determined empirically by the end user.

Storage, Stability, and Quality Control

Storage: Always refer to the lot-specific COA for authoritative storage conditions. As a general best practice for purified IgG proteins:

• Short-term (up to 1 month): store at 2–8 °C.
• Long-term: aliquot into single-use volumes and store at -20 °C. Avoid repeated freeze-thaw cycles, which can cause aggregation and loss of protein integrity.
• Do not store in frost-free freezers that undergo repeated temperature cycling.

Stability: Protein stability depends on buffer composition, concentration, and handling. Adding a carrier protein (e.g., 0.1% BSA) may improve stability of diluted working solutions.

Quality Control: The specific concentration for each lot is provided on the COA accompanying the product shipment. Users are advised to verify protein concentration independently if critical quantification is required. Assess integrity by SDS-PAGE if needed.

Troubleshooting