The following are frequently asked questions about our products and services. If you have a question that is not answered on this page, or if you want clarification, please feel free to contact us. Our technical support team is always glad to help.
Email us at biotechnology@affibody.com, or call +46(0)8 59 88 38 00, 08.00 - 17.00 (Central European Time).
What is an Affibody® molecule?
The backbone of the Affibody® molecule is derived from one of the IgG-binding domains of Protein A, a bacterial surface protein from Staphylococcus aureus. The binding surface of the parent Protein A domain has been randomized to form pools of billions of Affibody® molecules, all with different binding sites, thus capable of binding different target proteins.
What is the difference between an Affibody® molecule and an antibody?
The small Affibody® molecule displays a binding surface as large as an antibody, but the binding surface constitutes a much larger proportion of the entire molecular surface. The binding surface of the Affibody® molecule is composed of surface-exposed amino acid residues of alpha helices 1 and 2 of the three-helix bundle protein, whereas the binding site of an antibody is composed of sidechains from loops connecting beta-sheets.
What is the advantage with Affibody® molecules over antibodies as a research reagent?
Many of the advantages of the Affibody® molecule stem from the fact that it is a small protein of only 58 amino acid residues forming a compact three-helix bundle. This allows for exceptional stability and favorable binding properties. The molecule has also inherited an unusual solubility from the parent Protein A molecule. The main competitive features of Affibody® molecules are small size; extreme stability; low production cost; low background binding and a favorable patent situation.
Can Affibody® molecules be used in the same applications as antibodies?
The Affibody® molecule can be used for the applications listed in the products list including typical antibody mediated methods such as immunofluorescence, flow cytometry and immunoprecipitation. The Affibody® molecule can also be used for double staining together with an antibody provided that the Affibody® molecule and antibody is not directed against the same epitope on the antigen.
What kind of affinities can one obtain with Affibody® molecules?
Affibody molecules have been developed with KD values ranging from µM to pM.
Is it possible to enhance affinity by maturation?
Yes.
What is the size of an Affibody® molecule?
An Affibody® molecule consists of 58 amino acids and is 6-7 kDa in size. Affibody® molecules commercialized as research reagents in the web shop are are genetically engineered head-to-tail dimers; with a molecular weight of approximately 14 kDa.
Can the Affibody® molecule be labeled?
The Affibody® molecule has a genetically introduced C-terminal cysteine that is suitable for labeling with sulfhydryl-reactive compounds. The protocol for coupling is included in the application note for the unconjugated products. For a separate protocol, click here.
What is the minimum size of target?
The size of the protein targets selected against so far ranges from 4 to over 800 kDa.
If a species is not listed as cross-reactive with the Affibody® molecule on the data sheet, does this mean that the species has not been tested?
Yes.
Do you have any references for Affibody® molecule?
A vast number of publications illustrate the broad applicability of Affibody® molecules, starting with the first publication of the concept in 1997. Click here to view a complete list.
What is the shelf life of Affibody® research regagents?
Unconjugated Affibody® molecules are lyophilized and are extremely stable. There is no decrease in performance of the reconstituted Affibody® molecule (1 mg/ml in PBS) after 10 repeated freeze and thaw cycle or after storage for 2 weeks in room temperature.
What are the recommended storage conditions?
+4°C is recommended for lyophilized protein. For reconstituted protein in physological buffer, short-term storage at +4°C is recommended. For long-term storage, the protein solution should first be aliquoted and stored frozen at -20°C.
Can the product be used in an ELISA for serum samples?
The functionality of Affibody® molecule as capture reagent in ELISA using plasma or serum samples is described in the application note for each Affibody® molecule.
Does the product come with pre-coated plates?
No.
What is the sensitivity of Affibody® molecules in an ELISA?
The sensitivity is described in the application note for each Affibody® molecule and should be considered as a guideline. Please observe that the sensitivity may vary depending on the second step antibody, the batch of standard protein and the HRP-conjugate.
Can I use Affibody® molecules in immunohistochemical (IHC) assays on paraffin imbedded tissue or frozen tissue sections?
Each Affibody® molecule works in a set of applications and the application notes can be found in the web shop.
Will Affibody® molecules work in Formalin Fixed Paraffin Embedded (FFPE) tissue samples?
Each Affibody® molecule works in a set of applications and the application notes can be found in the web shop.
Can I use Affibody® molecules for immunoprecipitation (IP)?
Each Affibody® molecule works in a set of applications and the application notes can be found in the web shop.
Is the Affibody® molecule immunogenic?
The protein has given rise to intermediate to low immune responses in mice and rats.
How is the stability of Affibody® molecules in vivo?
Very good - no effect of repeated cycles with sera on an immobilized dimeric Affibody® molecule.
What is the half life in vivo?
Less than 30 minutes.
Can the Affibody® molecule cross the blood-brain barrier?
There is no indication of this.