Custom and Catalog Peptides

  1. How do I request a quote for my peptide?

  2. What type of chemistry do you use?

  3. How do you generally purify your peptides?

  4. How are the peptides supplied?

  5. What peptide scales are available?

  6. What is the typical turn-around time for peptide synthesis?

  7. Is there any limitation on the length of peptides that can be achieved?

  8. What if some problems come up during the synthesis or purification process?

  9. Are peptides containing free Cys supplied as monomers?

  10. What does SPPS mean?

  11. Why are peptides sold as salts?




  1. How do I request a quote for my peptide?


    To request an instant quote, please sign up a free account with us and proceed to the peptide order page. If you do not have an account with us yet and would like to receive a quote for your peptide(s), please email us: www.aapptec.com or call us at 1-888-692-9111 and ask for a peptide service representative.



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  2. What type of chemistry do you use?


    AAPPTec generally utilizes Fmoc chemistry for most peptide production. 



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  3. How do you generally purify your peptides?


    Our peptides are generally purified by preparative reversed phase HPLC, using trifluoroacetic acid (TFA) modified buffers at pH 2. Buffer A is 0.1 % TFA deionized water and buffer B is 0.1 % TFA in acetonitrile (ACN) at pH 2. Peptides are dissolved in either straight buffer A, or some amount of buffer B then diluted with buffer A.

    Sometimes it is necessary to use an organic polar solvent like (formic acid or acetic acid) in DMSO or DMF to aid in the dissolving of hydrophobic peptides but this is done on a case-by-case basis depending on the sequence analysis. The separation is monitored by UV at 214 nm and fractions are collected and analyzed by mass spectrometry for product identity and by reversed phase analytical HPLC for purity.

    The fractions are then lyophilized to remove the solvents. The fractions that meet the specifications of the order are then combined into one vial. Next, we run a final mass spectrum  and analytical HPLC on the combined material.



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  4. How are the peptides supplied?


    Unless specified otherwise, peptides are shipped as TFA salts.  Peptides are shipped as lyophilized powders at room temperature.  Upon receiving, the peptides should be stored dry at –20 C.  As lyophilized powders, peptides are stable at room temperature up to 1 week.  Stored at –20 C, lyophilized peptides are stable up to 1 year.



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  5. What peptide scales are available?


    AAPPTec typically synthesizes peptides in a scale from 2 to 100mg. Other scales are available upon request.



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  6. What is the typical turn-around time for peptide synthesis?


    For a standard peptide under 30 amino acids, delivery of the finished product is 2-3 weeks. This time could vary depending on the length and difficulty of the peptide.



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  7. Is there any limitation on the length of peptides that can be achieved?


    AAPPTec can synthesize peptides from 2 amino acids up to 100 amino acids.



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  8. What if some problems come up during the synthesis or purification process?


    Each peptide has unique characteristics. Sometimes these characteristics may cause unpredicted difficulty in synthesizing or purifying the peptide.  If problems during synthesis or purification arise, AAPPTec will notify you immediately.



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  9. Are peptides containing free Cys supplied as monomers?


    Yes.  The purity stated on the Certificate of Analysis for peptides containing free Cys residues signifies the monomer content at the time the analytical HPLC was recorded. As air oxidation cannot be completely prevented in the meantime, we suggest reducing the peptide before use by treatment with dithiothreitol (DTT). For a short description of the cystine reduction using DTT please see our Technical Note.



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  10. What does SPPS mean?


    SPPS (solid-phase peptide synthesis) is a standard method for preparing peptides.   The peptide, linked by its C-terminal amino acid to a synthesis resin, is assembled in the C→ N direction. It is elongated stepwise by coupling protected derivatives of the amino acids corresponding to the peptide sequence.  After each coupling step, the "temporary" Nα-blocking group is removed without affecting the lateral protective groups and the link to the carrier.  The method can be fully automated. Thus, peptides can be obtained by SPPS far more rapidly than in solution, but the method requires large excesses of amino acid derivatives for driving the coupling steps to completion.



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  11. Why are peptides sold as salts?


    The guanidino group of Arg, a strong base, the ε-amino group of Lys, the free N-terminus, and the weakly basic imidazole moiety of His can form salts with acids. Most peptides contain at least one of these basic functionalities.  Quite often, peptides are more soluble as salts than when they are desalted. 

    Except when mentioned otherwise, our peptides are provided as trifluoroacetate salts. Peptides obtained by SPPS come into contact with trifluoroacetic acid (a strong acid) during cleavage from the carrier resin and purification. Generation of other salt forms requires an additional ion-exchange step.  Acidic peptides, i.e. peptides containing a large proportion of Asp and/or Glu, or phospho- or sulfotyrosine, can form salts with bases. Thus, a few acidic peptides are sold as ammonium salts.



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