Transmembrane Proteins

A: Different membrane protein technology platforms have their own advantages and disadvantages. The selection should be based on the specific protein expression needs and application scenarios. You can consult with technical personnel from CUSABIO for specific guidance. Below is a comparison of different platforms:

A: Mammalian enveloped VLPs are enveloped virus-like particles, which are self-assembled by one or several structural proteins of the virus into a virus-free genome that cannot replicate and have no infectivity, but are similar in shape and structure to complete viruses and do not contain viral nucleic acid substances. It’s safe. Now many vaccines will also choose this technology, which shows that it is safe.

Mammalian enveloped VLPs are co-transfected with two expression plasmids (expressing transmembrane protein and capsid protein respectively) without using any virus and viral vector, and the transfection reagents are used for transient transfection.

A: In the early stage of platform development, a variety of membrane skeleton proteins and phospholipid molecules were tried, and orthogonal combinations were attempted, and finally a pair of optimal membrane skeleton proteins and phospholipid molecules was screened out. At present, the platform is mature and we use this same combination for different projects.

A: Considering that the total concentration of VLPs is measured, the recommended coating concentration is 2-10ug/ml, and the amount used for one well is 0.2-1ug.

A: The Bradford assay method is used for the concentration determination. The specific concentration of each item and each batch is different. Please consult the concentration information of the corresponding batch during pre-sales inquiry.

A: At present, we have tested, without adjuvant, adding rapid adjuvant (without emulsification) and conventional Freund's adjuvant to evaluate the impact on immunity. From the final effect, it is recommended to use rapid adjuvant.

A: There are many, but it involves customers projects, it is inconvenient to inform.

A: Relatively stable, and the specifics are also related to each project (the specific data is temporarily confidential).

A: Considering the difference of different positive antibodies, we will generally produce a positive antibody by ourselves. If both of the customer's antibody and our produced positive antibody don’t bind, it belongs to the risk-free category (no charge for inactivity).

A: We can provide empty VLPs as control for free, the negative control value is 0.1 or lower.

A: The envelope of VLPs is derived from the cell membrane and itself is a stable membrane.

A: The three bands coorespond to monomer, dimer and trimer respectively.

A: We are sorry to tell you that VLPs and target protein cannot be separated, because VLPs protein is an enveloped virus-like particles, and the target protein is displayed on the surface. The target protein can be close to the natural conformation in VLPs. So the VLPs protein also cannot be accurately quantified. But we provide the VLPs control protein under the same preparation conditions for free to the customer to deduct the influence of the host membrane protein on the envelope.

A: The standard buffer that we normally use is PBS, pH 7.4, 6% trehalose. We can etither provide it in liquid form or lyophilized form, please communicate with us in advance if you have any special requirement for the buffer or the shipping format.

Liquid form: It needs to be shipped with dry ice and we need to charge extra fees for dry ice and dry ice box.

Lyophilized form: It could be shipped with normal bule ice packs and no extra charges. However, if you request to ship with dry ice, please communicate with us in advance and extra fees will be charged.

Transmembrane proteins are displayed on the nanoparticle envelope in their native state.

A: Yes, the structure are identical except for CCR4.

Our Claudin18.2 has been developed with VLP platform. Both of VLP version and the detergent version are suitable for immunization and screening. However, the VLP version may be preferred for improved immunogenicity. For accurate affinity measurements, maybe the detergent version is more suitable.

Multi-pass transmembrane proteins span the cell membrane multiple times forming multiple extracellular domains. For example, Claudin18.2 and CD20 have two extracellular loops (ECLs) with each ECL having specific functions and interactions with each other. Full length can ensure that the protein conformation is biologically relevant while enabling the ECL to be completely exposed for improved screening of ideal antibodies. According to our experience, the full length is active and relevant compared to isolated extracellular domain. It is not the case that CUSABIO always emphasizes full length proteins, but drug discovery R&D work needs the full-length multi-pass transmembrane proteins. Indeed, when compared, the activity of only the ECL region is worse than that of the full-length protein. CUSABIO is committed to providing the high quality and relevant products that meet customers' needs.

Claudin18.2-VLP is tested and verified by anti-Claudin18.2 specific antibodies. The existence is evaluated by WB/SEM. The conventional negative dye EM cannot see whether Claudin18.2 is on the VLP due to its low resolution. Binding activity with anti-Claudin18.2 specific antibodies can confirm the presence of Claudin18.2 on the particles.

After our continuous technical optimization, we can now provide VLP-membrane proteins in lyophilized form, which can be transported by normal blue ice packs. VLP immunization mainly requires attention to the choice of adjuvant dose, because VLP itself can enhance immunogenicity, which is not the case for conventional protein products.

A: Generally, it will take 1.5 to 2.5 months, including the activity test. If customers have positive antibodies, they can send us to test activity.