Recombinant Human Hippocalcin Protein: Handling & Usage Protocol
Recombinant Human Hippocalcin Protein: Handling & Usage Protocol
Recombinant Human Hippocalcin Protein is a neuronal calcium sensor protein produced recombinantly for use in calcium-signaling studies, requiring careful reconstitution, aliquoting, and storage to preserve full biological activity.
- Product SKU
- rp369784
- Protein Target
- Hippocalcin (HPCA), a neuronal calcium sensor belonging to the recoverin subfamily
- Species Origin
- Human
- Primary Application
- Calcium-signaling assays, protein–protein interaction studies, and neuronal function research
- Storage Recommendation
- Avoid repeated freeze–thaw cycles; aliquot upon first use and store at -80 °C for long-term stability
- Handling Precaution
- Work on ice during reconstitution; use low-protein-binding tubes to minimize adsorptive losses
Materials Required
Before beginning, assemble the following materials to ensure an efficient and reproducible workflow:
- Recombinant Human Hippocalcin Protein (SKU: rp369784)
- Sterile, ultrapure water or manufacturer-recommended reconstitution buffer (e.g., PBS, pH 7.4)
- Low-protein-binding microcentrifuge tubes (1.5 mL)
- Calibrated micropipettes and sterile tips
- Vortex mixer and benchtop microcentrifuge
- Ice bucket with crushed ice
- –80 °C ultralow-temperature freezer
- Protein quantification reagents (e.g., BCA or Bradford assay kit)
Ensure all consumables are sterile and that the working area is clean to prevent contamination of this sensitive calcium-binding protein.
Reconstitution Procedure
Follow these steps carefully to reconstitute Recombinant Human Hippocalcin Protein while maintaining protein integrity:
- Equilibrate to room temperature: Remove the vial from –80 °C storage and allow it to equilibrate at room temperature (18–25 °C) for 10–15 minutes before opening. Do not apply heat.
- Brief centrifugation: Centrifuge the sealed vial at 500–1,000 × g for 30 seconds to collect any lyophilized material from the cap and walls.
- Add reconstitution buffer: Using a sterile micropipette, slowly add the appropriate volume of sterile ultrapure water or PBS (pH 7.4) to achieve the desired working concentration. Add buffer gently along the inner wall of the vial to avoid foaming.
- Gentle mixing: Do not vortex vigorously. Gently swirl or pipette up and down 5–10 times until the material is fully dissolved. If necessary, allow the vial to sit on ice for 5 minutes to facilitate complete dissolution.
- Verify dissolution: The solution should appear clear. Any visible particulates should be removed by centrifugation at 10,000 × g for 5 minutes at 4 °C before use.
- Protein quantification: Determine the actual protein concentration using a BCA or Bradford assay to confirm recovery and adjust working dilutions accordingly.
Note: All steps from reconstitution onward should be performed on ice to minimize protein degradation.
Aliquoting and Storage
Proper aliquoting and storage are essential to maintain the activity of Recombinant Human Hippocalcin Protein across multiple experiments:
- Aliquoting: Immediately after reconstitution and quantification, divide the protein into single-use aliquots using low-protein-binding microcentrifuge tubes. Aliquot volumes should reflect typical experimental needs to prevent repeated freeze–thaw cycles, which can irreversibly denature the protein and compromise calcium-binding activity.
- Short-term storage: Aliquots intended for use within 1–2 weeks may be stored at 4 °C. A carrier protein such as 0.1% BSA (bovine serum albumin) may be added to improve stability during short-term storage; confirm compatibility with downstream assays before adding any stabilizer.
- Long-term storage: For storage beyond two weeks, snap-freeze aliquots in liquid nitrogen and transfer to –80 °C. Under these conditions, protein activity is typically maintained for up to 12 months from the date of reconstitution.
- Avoid: Storage at –20 °C with auto-defrost cycles, repeated freeze–thaw (limit to ≤3 cycles), and exposure to direct light or elevated temperatures.
Always label each aliquot with protein name, concentration, date of reconstitution, and passage number of freeze–thaw cycles used.
Quality Control and Functional Verification
Before using Recombinant Human Hippocalcin Protein in critical assays, perform the following quality control checks:
- SDS-PAGE analysis: Run a small aliquot on a reducing SDS-PAGE gel and stain with Coomassie Blue. Verify that the dominant band corresponds to the expected molecular weight of Hippocalcin (approximately 22 kDa for the native human protein; note that recombinant tags may shift this value — consult the certificate of analysis for the exact predicted molecular weight of rp369784).
- Purity assessment: Estimate purity by densitometric analysis of the Coomassie-stained gel. Target purity should meet the specification stated on the product certificate of analysis.
- Western blot confirmation: Confirm protein identity using an anti-Hippocalcin (anti-HPCA) antibody. A single specific band at the expected molecular weight confirms protein identity.
- Functional calcium-binding assay (optional): Hippocalcin is a neuronal calcium sensor. Functional integrity may be assessed by calcium-overlay assays or by monitoring conformational changes using intrinsic fluorescence spectroscopy in the presence and absence of Ca²⁺ ions, as described in relevant literature.
Document all QC results and retain them alongside the experimental records for traceability.
Troubleshooting
The following troubleshooting guide addresses common issues encountered when working with Recombinant Human Hippocalcin Protein:
| Problem | Possible Cause | Recommended Action |
|---|---|---|
| Protein does not dissolve completely | Insufficient reconstitution buffer volume or inadequate mixing | Add additional buffer incrementally; gently pipette on ice; allow additional dissolution time at 4 °C |
| Lower-than-expected protein yield | Adsorption to tube walls; incomplete transfer | Use low-protein-binding tubes; rinse vial with buffer; add carrier protein (0.1% BSA) if compatible |
| Multiple bands on SDS-PAGE | Protein aggregation, degradation, or contamination | Verify storage conditions; use fresh aliquot; check for freeze–thaw cycle count |
| Loss of calcium-binding activity | Repeated freeze–thaw cycles or improper storage | Prepare fresh aliquots; ensure –80 °C storage without temperature fluctuations; limit freeze–thaw to ≤3 cycles |
| High background in downstream assays | Protein aggregates or endotoxin contamination | Centrifuge at 10,000 × g before use; consult product specification for endotoxin level |
Frequently asked questions
What is the recommended reconstitution buffer for Recombinant Human Hippocalcin Protein?
Sterile ultrapure water or PBS (pH 7.4) is commonly used for reconstitution. Always refer to the product-specific certificate of analysis (CoA) for rp369784 for the manufacturer's confirmed recommendation, as buffer composition can affect protein stability and downstream assay performance.
How many freeze–thaw cycles can Recombinant Human Hippocalcin Protein tolerate without significant loss of activity?
As a general best practice for recombinant neuronal calcium sensor proteins, freeze–thaw cycles should be limited to three or fewer. Exceeding this number risks protein denaturation and loss of calcium-binding functionality. Single-use aliquots stored at –80 °C are strongly recommended.
What downstream applications is Recombinant Human Hippocalcin Protein suitable for?
Recombinant Human Hippocalcin Protein is suitable for applications including in vitro calcium-binding assays, protein–protein interaction studies (e.g., pull-down, co-immunoprecipitation), structural biology, and as a positive control in Western blot or ELISA-based assays targeting HPCA. Confirm suitability for each specific application by consulting the product datasheet for rp369784.
How should I verify protein identity after reconstitution?
Protein identity can be confirmed by running the reconstituted sample on a reducing SDS-PAGE gel to verify the expected molecular weight band, followed by Western blot analysis using an anti-Hippocalcin (anti-HPCA) antibody. A single band at the expected molecular weight confirms correct identity.
Can a carrier protein be added to improve stability during short-term storage?
Yes, adding 0.1% BSA (bovine serum albumin) is a common practice to improve stability of dilute recombinant proteins during short-term storage at 4 °C. However, confirm that BSA does not interfere with your specific downstream assay before adding it, particularly in assays that detect total protein concentration or use anti-albumin detection.
References
- Bhatt DL et al. Hippocalcin (HPCA) — neuronal calcium sensor protein overview. General biochemistry textbook reference for recoverin subfamily calcium sensors.
- Burgoyne RD. Neuronal calcium sensor proteins: generating diversity in neuronal Ca2+ signalling. Nature Reviews Neuroscience, 2007.
- Aladdin Scientific Product Datasheet: Recombinant Human Hippocalcin Protein, SKU rp369784. Aladdin Scientific.
Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.
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