Here we take a look at Where to buy peptides are and where to buy peptides for educational and research needs. Research peptides are a new form of chemicals that are being tested to treat various age-related health problems.
Where to Buy Peptides for Research?
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What is a Peptide Sequence?
A region or a sequence, which exhibits a relatively strong affinity to the antibodies used. The antigen as required can be produced using the immunological method known to the person skilled in the art, e.g. the methods described in the literature, see e.g. M. Kast, Immunology of Peptide Synthesis, Springer-Verlag Berlin Heidelberg New York 1992; R. V. Page, Synthesis of Peptides and Proteins, New York, Oxford University Press 1988.
The immunological method known to the person skilled in the art can be adapted for the production of the antigen required. In one embodiment the antigen is a fusion protein that contains the antigen, as well as an antigenic fragment of the protein to be measured, as the antigens to be measured, are often too small to be purified to homogeneity.
The method known to the person skilled in the art comprises the following steps:
a) a host cell is transformed with an expression vector comprising DNA encoding for a polypeptide chain which is known to the person skilled in the art to be immunogenic and which comprises the antigen of interest and/or an antigenic fragment thereof
b) the transformed host cell is cultured under suitable conditions, whereby an amount of the polypeptide chain of interest is produced by the host cell.
How the antigen is produced?
The antigen can be purified from the culture supernatant or from the cell in which it was produced. It uses affinity chromatography, followed by further purification if necessary. In one embodiment, the antigen is a fusion protein, i.e. the antigen is not directly produced in the host cell, but is produced as a part of another protein, which in turn is produced as a part of the antigen.
The expression vector used in the step comprises DNA coding for the first protein. In this case, the method comprises the following steps:
- a host cell is transformed with a second expression vector comprising DNA encoding for a fusion protein.
- The transformed host cell is cultured under suitable conditions.
- The culture supernatant or the cell in which the polypeptide of interest is produced is contacted with an antibody specific for the second protein and an amount of the polypeptide is bound to the antibody.
- The bound polypeptide is eluted.
- A further purification step is performed.
What is a Polypeptide?
The second protein (e.g. a polypeptide) used in the method described in the second embodiment can be a fusion protein comprising the antigen as its N- or C-terminal portion. In this case, the first protein which is produced as a part of the antigen comprises a peptide sequence. It binds to an antibody specific to the polypeptide. The first protein binds to the antibody when the polypeptide is produced as a part of the fusion protein.
Steps of the method described above in the second embodiment can be repeated to further increase the yield of the polypeptide of interest. However, once the maximum yield is reached, the production of the fusion protein can be terminated. A further embodiment is characterized in that a method for the production of a fusion protein is used which comprises steps above. In this case, the second protein (e.g. a polypeptide) is a fusion protein comprising the antigen as its N- or C-terminal portion.
The first protein is produced as a part of the fusion protein with a polypeptide which can be purified in a purification step by the use of antibodies, such as monoclonal antibodies, which bind to the polypeptide.
Preferably, the fusion protein is produced in accordance with the method described above in a). The second protein can be a polypeptide which is present in the culture medium, or it can be a fusion protein comprising the antigen as its N- or C-terminal portion. The antigen can be present at an expression level of from 0.1% to 50% of the total amount of polypeptide in the mixture comprising the fusion protein and culture medium. A preferred embodiment is characterized in that the polypeptide comprises a sequence of from 1 to 5 amino acids, more preferably from 3 to 5 amino acids, most preferably from 3 to 5 amino acids.
What are proteins?
Examples of proteins that can be used as second proteins in the fusion protein according to the invention are polypeptides present in the medium and purification steps, e.g. an N-terminal polyhistidine (His) peptide and a C-terminal Strep II (Streptococcus Typhimurium protein A-II) peptide.
Examples of polypeptides are those which are present in the medium of the bacterial culture. The medium can be a nutrient broth, such as for example a nutrient broth according to EP patent applications having publication numbers 0 689 566 and 0 689 566, which are incorporated herein by reference. The polypeptides can be present in the medium in an amount of from 10 pg/ml to 10 mg/ml, more preferably from 50 pg/ml to 0.5 mg/ml, more preferably from 50 pg/ml
Examples of suitable protein fusion proteins are those having from 6 to 30, e.g. from 12 to 30, amino acid residues. Preferably the protein comprises a sequence of from 6 to 30 amino acids, more preferably of from 12 to 30 amino acids, and most preferably from 15 to 30 amino acids.
The protein fusion proteins of the invention can be prepared according to known techniques. For example, using techniques well known to the person skilled in the art, such as polypeptide coupling, recombinant techniques, or genetic engineering.