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Recombinant Severe Acute Respiratory Syndrome Coronavirus 2 Spike RBD

rSARS-CoV-2 Spike RBD

Item No:6Z1-03
Protein Structure
$ 330
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Technical Data
    Escherichia coli.
    Molecular Weight
    Approximately 25.1 kDa, a single non-glycosylated polypeptide chain containing 223 amino acid residues.
    AA Sequence
    > 90% by SDS-PAGE analyses.
    Biological Activity
    Testing in progress.
    Physical Appearance
    Sterile Filtered White lyophilized (freeze-dried) powder.
    Lyophilized from a 0.2 µm filtered concentrated solution in 30% acetonitrile and 0.1% TFA.
    Less than 0.1 EU/μg of rSARS-CoV-2 Spike RBD as determined by LAL method.
    We recommend that this vial be briefly centrifuged prior to opening to bring the contents to the bottom. Reconstitute in 10mM HCl to a concentration of 0.1-1.0 mg/mL. Stock solutions should be apportioned into working aliquots and stored at ≤ -20 °C. Further dilutions should be made in appropriate buffered solutions.
    The product is shipped at ambient temperature. Upon receipt, store it immediately at the temperature recommended below.
    Stability & Storage
    Use a manual defrost freezer and avoid repeated freeze-thaw cycles.
    - 12 months from date of receipt, -20 to -70 °C as supplied.
    - 1 month, 2 to 8 °C under sterile conditions after reconstitution.
    - 3 months, -20 to -70 °C under sterile conditions after reconstitution.
    This material is offered by Shanghai PrimeGene Bio-Tech for research, laboratory or further evaluation purposes. NOT FOR HUMAN USE.
    SARS-CoV-2, which causes the global pandemic coronavirus disease 2019 (Covid-19), belongs to a family of viruses known as coronaviruses that are commonly comprised of four structural proteins: Spike protein(S), Envelope protein (E), Membrane protein (M), and Nucleocapsid protein (N). SARS-CoV-2 Spike Protein (S Protein) is a glycoprotein that mediates membrane fusion and viral entry. The S protein is homotrimeric, with each ~180-kDa monomer consisting of two subunits, S1 and S2. In SARS-CoV-2, as with most coronaviruses, proteolytic cleavage of the S protein into two distinct peptides, S1 and S2 subunits, is required for activation. The S1 subunit is focused on attachment of the protein to the host receptor while the S2 subunit is involved with cell fusion. Based on structural biology studies, the receptor binding domain (RBD), located in the C-terminal region of S1, can be oriented either in the up/standing or down/lying state. The standing state is associated with higher pathogenicity and both SARS-CoV-1 and MERS can access this state due to the flexibility in their respective RBDs. A similar two-state structure and flexibility is found in the SARS-CoV-2 RBD. Based on amino acid (aa) sequence homology, the SARS-CoV-2 S1 subunit RBD has 73% identity with the RBD of the SARS-CoV-1 S1 RBD, but only 22% homology with the MERS S1 RBD. The low aa sequence homology is consistent with the finding that SARS and MERS bind different cellular receptors. The S Protein of the SARS-CoV-2 virus, like the SARS-CoV-1 counterpart, binds Angiotensin-Converting Enzyme 2 (ACE2), but with much higher affinity and faster binding kinetics. Before binding to the ACE2 receptor, structural analysis of the S1 trimer shows that only one of the three RBD domains in the trimeric structure is in the "up" conformation. This is an unstable and transient state that passes between trimeric subunits but is nevertheless an exposed state to be targeted for neutralizing antibody therapy. Polyclonal antibodies to the RBD of the SARS-CoV-2 protein have been shown to inhibit interaction with the ACE2 receptor, confirming RBD as an attractive target for vaccinations or antiviral therapy. There is also promising work showing that the RBD may be used to detect presence of neutralizing antibodies present in a patient's bloodstream, consistent with developed immunity after exposure to the SARS-CoV-2 virus. Lastly, it has been demonstrated the S Protein can invade host cells through the CD147/EMMPRIN receptor and mediate membrane fusion.
    1Why do proteins need to be lyophilized? What are the effects on proteins?
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    Proteins are heat sensitive and lyophilization allows the protein to be stored with maximum activity, extended shelf life, and reduced transportation costs. The effects of lyophilization on proteins include the possibility of partial inactivation, aggregation and other denaturation problems. However, these negative effects can be minimized by adding protective agents (stabilizers, additives, excipients) and controlling the various conditions of lyophilization.
    2Why add protectants to the protein solution before lyophilization? What are the common protective agents used by PrimeGene?
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    Freeze-drying has a certain effect on the activity of proteins, and the addition of a protective agent can reduce this effect and maximize the protection of protein activity. The usual protectants or stabilizers are sugars, polyols, polymers, surfactants, certain proteins and amino acids. Our common protective agents are: trehalose, mannitol, etc.
    3Why do some proteins come with labels?
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    The tagged proteins are generally used to meet the experimental requirements of some customers. If His-tag and GST-tag are required, affinity purification columns can be used; proteins fused to Fc fragments of immunoglobulins can be used for antibody studies, etc.
    4How is the protein quantified?
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    Usually three methods, BCA ,Bradford and OD280, are used for quantification.
    5Why the results measured by my quantification method do not match the quantification on the PrimeGene label?
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    Different protein quantification methods are used and will give different results. Sometimes the difference in results caused by different quantification methods is significant.
    6I purchased a small package of lyophilized protein, why did I receive only one empty tube?
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    Unlike some protein products on the market, the vast majority of our products do not contain carrier proteins or other additives (such as bovine serum albumin (BSA), human serum albumin (HSA) and alginose) and are lyophilized in a solution with minimal salt content. As a result, trace amounts of protein are deposited inside the tube during the lyophilization process, forming a very thin or almost invisible protein layer, and even the protein powder can drift on the tube walls. Before opening the cap, we recommend rapid centrifugation in a centrifuge for 20-30 seconds to allow the protein powder attached to the cap or wall to collect at the bottom of the tube.
    7How to reconstitute the lyophilized powder protein?
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    Unless the instructions are more specific, we recommend the following.
    (1) Equilibrate the reagent bottle and reconstitute buffer to room temperature.
    (2) Centrifuge the reagent vial briefly to ensure that all lyophilized material is collected at the bottom of the vial.
    (3) Add the recommended re-dissolution buffer to the concentration recommended on the product description. Avoid vigorous shaking or pipette blowing, which may result in denaturation of the protein.
    (4) Allow reagent vials to redissolve at room temperature for 15-30 minutes, either using a 360 degree shaker or manually by gently inverting up and down.
    (5) Dispense in volumes no less than 10μl per tube and store as directed on the product insert.
    (6) If the vial presents flakes or pellets, mix the product at room temperature for several hours and then overnight at 4°C.
    8How to determine the reference dosage for protein activity experiments?
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    All protein products which have been verified by biological activity have activity verification information on our product page, customers can check the information of cell type used and ED50 value in the Biological Activity column.
    9Why is ED50 a range?
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    A bioactivity assay is a measurement of the biological response of a protein. Therefore, any changes in the bioactivity assay may also lead to different results. Such variations may include cell density, cell age, number of passages, nutritional status, media and additives used, as well as the experimental operator's practices. Due to the variable nature of bioactivity assays, the same protein may not produce the same ED50 under different circumstances. For this reason, PrimeGene's protein instructions give a range of ED50s.
    10Application of products
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    Our products can be classified according to scientific fields, but no clear guidance is given on their specific applications. Since proteins can be explored for multiple applications and methods of application according to their functions, we recommend our customers to conduct experiments according to the literature or to explore their own application methods based on scientific research.
    11Can the protein be used for in vivo experiments (In vivo)? What is the recommended concentration?
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    PrimeGene Protein does not perform any in vivo testing. We do not have data on the activity and half-life of these products in in vivo applications.
    12What is Trehalose and what is its role in the formulation?
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    Trehalose is a non-reducing sugar that does not react with amino acids or proteins in the Murad reaction. It is found in many plants and animals in nature. Alginate stabilizes proteins against damage caused by freezing and also makes them more resistant to water when freeze-dried, thus making it less likely that the product will precipitate upon re-solution.
    13If the product contains trehalose, will in vivo experiments (In vivo) affect the animals?
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    Trehalose is unlikely to affect in vivo experiments. It is approved for use as an excipient in human injectable drugs. The trehalose used in the R&D system is derived from brewer's yeast and has a purity of at least 98.5% as determined by HPAE.
    14Does trehalose interfere with the ligation reaction (Conjugation)?
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    The presence of trehalose may interfere with the successful binding of proteins. This will depend on the method of conjugation and customers are advised to do the relevant research before purchasing the product.
    15The lyophilized form of the recombinant protein product arrives at room temperature and the instructions indicate that it should be stored at -20ºC. Does this shipping method affect the activity of the product?
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    The lyophilized powder product is shipped at ambient temperature (Ambient) and will not be affected. Freeze-drying improves the stability of the protein product while reducing packaging materials and shipping costs. We have tested the shipping conditions of our freeze-dried products to ensure product quality.
    16How to store the product?
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    Because of the different nature of the products, please read the instructions carefully and store them properly according to the methods described in the instructions.
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