Frequently Asked Questions (FAQs)

Protein Specifications Ordering Shipping

Protein Specifications

How do you biotinylate the proteins? Do you use chemical biotinylation?

We offer both enzymatic and chemical biotinylation methods to meet different researcher's needs. Our proteins are primarily enzymatically biotinylated via AviTag™ technology. During sub-cloning, a unique 15-amino acid peptide called the AviTag is fused to the gene of interest. The single lysine residue within this tag is biotinylated by the enzyme biotin ligase (BirA), ensuring precise and uniform biotin labeling at a single site. This method avoids interference with the target protein's natural binding activities and ensures uniform protein orientation when immobilized on avidin-coated surfaces, which is ideal for binding assays.

What is the tag length? How do you decide what tag length to use?

We typically use His, hFc (human Fc), mFc (mouse Fc), or no tag, depending on the application. For His-tagged proteins, we use an 8-residue His tag, as this length provides a strong and reliable affinity for purification without compromising protein function.

For Fc-tagged proteins, both human and mouse Fc regions are used, typically based on IgG1 isotypes. These Fc tags have stable lengths and do not require customization. Occasionally, mouse IgG2a is employed for specific applications. Our tag selection and length are optimized to ensure efficient purification and maintain the protein’s structural integrity and functionality.

How do you purify the proteins based on different tags?

Recombinant proteins are often tagged to simplify the purification process. Common tags like His-tag (Histidine) or hFc-tag (human IgG1 Fc) provide specific binding affinities that aid in protein separation. The purification process generally begins with affinity chromatography. For His-tagged proteins, Nickel or Cobalt ion-immobilized resins are used, as these ions bind specifically to the histidine residues. For hFc-tagged proteins, Protein A-based affinity resins are employed, which selectively bind to the Fc region.

If further purification is needed to achieve higher purity levels, additional steps like ion-exchange chromatography can be performed. This method separates proteins based on their isoelectric point and overall charge. Gel filtration chromatography, which separates proteins by molecular weight, may also be applied as a final polishing step. For proteins with no tag or proteins that have no proper affinity resin, we start from ion-exchange chromatography, and then use gel filtration chromatography.

By selecting the appropriate purification methods, we ensure that our recombinant proteins meet high purity and functional standards for research and development applications.

Is there any linker between the protein and the tag?

The presence of a linker between the protein and the tag can vary depending on the specific protein and tag used. For example, we sometimes add a linker between the His-tag and the protein to improve detection, as certain protein conformations can sometimes obscure the His-tag. This adjustment is based on our research and customer feedback and ensures more reliable detection.

For Fc-tagged proteins, a linker may also be added, depending on the requirements or scientific literature supporting the need for it. If you'd like to know if your specific product has a linker or want more information, please contact us at support@kactusbio.us.

How should I reconstitute the protein?

Reconstitution instructions are on the product page or datasheet. If you need additional support for reconstitution, please contact support@kactusbio.us.

Can you share the full sequences of the protein?

Some of our protein sequences can be shared and some have undergone proprietary plasmid design. You can request the full sequence of your protein at support@kactusbio.us.

Where can I find the predicted molecular weight?

The protein's molecular weight can be found on the product page or datasheet. If you are unable to find the information or need additional support, please contact support@kactusbio.us.

Ordering

How do I pay by purchase order (PO)?

You can place an order directly online and select "Purchase Order" under the payment section. Please send your PO to orders@kactusbio.us. Alternatively, contact us directly at orders@kactusbio.us with the PO and we can set up the order for you.

How do I request a quote?

You can request a quote by going to a product page and selecting "add to quote". Select the black "Quote" button on the right hand side of the screen and click "Submit". Alternatively, email support@kactusbio.us with the items and quantities you are requesting a quote for.

Can I request a test sample?

Yes, please contact support@kactusbio.us to request a test sample.

How do I request customizations or a custom protein?

Please submit our custom protein request form or email support@kactusbio.us with the scope of the work.

Shipping

How much does shipping cost?

For lyophilized recombinant proteins, domestic shipping (US) is $45 and international shipping is $150.

For liquid recombinant proteins and enzymes, domestic shipping (US) is $90 and international shipping is $300.

How do I track my order?

When your items are packaged and scheduled for shipping, our system will send you a confirmation email, which will include the tracking number. If you did not receive a tracking number and you believe your item has been shipped out already, please contact orders@kactusbio.us.

Where do you ship to?

We offer international shipping to a majority of countries from our inventory hub in Boston, MA, USA.

We also have various international distributors. You can find a full list of our distributors here.

Do you have distributors?

Yes, you can find a full list of our distributors here.

What is the lead time?

For catalog products, a majority of our products ship out the next day. You can find the estimated ship day on the product page below the add to cart button.

For custom orders, the turnaround time is generally 6-8 weeks. You should contact support@kactusbio.us to discuss the scope of your requirements and the lead time.