Antigen FAQ

Frequently Asked Questions about DIARECT Antigens

How should I handle antigens upon receipt?
Upon receipt, our antigen products should remain frozen at - 70°C or below until use. We recommend thawing at room temperature, but thawed antigens should not remain at room temperature for longer periods of time. Mix the antigens gently before use.
If you plan on using only a portion of the product, please thaw and dispense it into aliquot volumes that are most practical for your application. Please note that we can only guarantee shelf life if the antigens are not frozen and thawed repeatedly.

What buffer is recommended for antigen storage?
While general recommendations for antigen storage conditions and buffers are given in the antigen's specification sheet, which can be found in the “+INFO” section associated with each antigen on DIARECT's website, the detailed buffer composition is available together with the lot-specific Certificate of Analysis.

Can I use antigens that arrive unfrozen?
No, we do not recommend using antigens without a guaranteed cold chain. If you receive a thawed product please inform our customer service immediately. Regarding dry ice shipments please visit section "shipping information" on our website for detailed information on temperature tests.

Where can I find supplementary information about an antigen?
For each antigen, DIARECT created a “+INFO” section on its website, which contains the antigen's material safety data sheet (MSDS) and specification sheet. The latter provides general recommendations regarding antigen storage and buffers. For select antigens, the  “+INFO” section also contains a brochure offering some background information and immunological test data.

What is the shelf life of your products?
Most of our antigen products have a guaranteed shelf life of five years unless otherwise noted on our Certificates of Analysis and Data Sheets, and providing that they are kept frozen at -70°C or below.

How can I benefit from DIARECT’s Reservation System?

We guarantee the reservation of a specified amount of antigen(s) without any obligation. Typically, customers reserve the amount of antigen(s) needed for a manufacturing period of up to 18 months. You simply inform us of your antigen requirements for this period, and every 4 months you will receive an updated overview regarding the accuracy of your estimate. The reservation system also includes the allocation of early enough samples of new lots of the respective antigen(s). This enables the customer to evaluate the new lot at an early stage for future reservations and allows a smooth transition to this new lot.
Advantages provided by DIARECT's reservation system:

  • Security of supply with no additional costs
  • No need for continual readjustment and fine tuning of your assay because of new antigen lots


What does Ec/BV stand for?
BV and Ec represent the type of expression system that was used to produce the antigen of interest. BV stands for DIARECT's baculovirus/insect cell expression system, while Ec stands for DIARECT's E. coli expression system.

What kind of technique does DIARECT use for purification?
For purification, the preferred technique is the very effective, yet gentle immobilized metal-ion affinity chromatography (IMAC) in combination with His-tag technology, which yields physiologically and immunologically active proteins.

How does DIARECT ensure lot-to-lot consistency of its antigens?
DIARECT's recombinant and native antigens - always produced according to documented procedures (SOPs) and manufactured per ISO 9001 and 13485 standards - undergo a rigorous series of tests in our quality control laboratory. Prior to its approval and release, each lot is subjected to various biochemical and immunological analyses to assure conformance to our strict product specifications. The goal of these extensive inspections is to ensure lot-to-lot conformance, which guarantees consistent results.

Where can I find sequence information about an antigen?
General information regarding the origin and expression constructs of antigens are provided in the respective specification sheets, however, exact sequence data are considered proprietary information.