Peptide Synthesis - Frequently Asked Questions

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Q: What is the typical turn-around time for peptide synthesis?

The typical turn-around time is 2-3 weeks for a standard peptide under 30 amino acids. This time could vary depending on the length and difficulty of the peptide.

Q: How do you ship peptides? What QC data will be provided?

All peptides are lyophilized in a vial. Each peptide comes with both HPLC and MS reports.

Q: Is there any limitation on the length of peptides that can be achieved?

We can synthesize peptide from 2 amino acids up to 100 amino acids.

Q: What if some problems come up during the synthesis or purification process?

Due to the unique characteristic of each peptide, sometimes problems with synthesis or purification could occur beyond our expectations; however, when such a scenario occurs, we will inform you immediately.

Q: 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:

peptide@etonbio.com

or call us at 1-800-758-1630 and ask for a peptide service representative.

Q: I have already submitted an order, can I still modify it?

Generally, you cannot modify your order if the processing of your order has already started. To make modifications to an existing order, go to the peptide order modification page, insert your requested modifications, and we will contact you as early as we can to let you know whether modifications can be made.

Q: How is my peptide purified and confirmed?

The peptide is purified by HPLC and confirmed by Mass Spectrometry.

Q: What is the purity for crude level peptide?

The purity for crude peptides is in the range of 50-60%.

Q: How much does it cost?

For standard peptides, please refer to our price table. For difficult peptides, please contact us or sign up today and get a quote instantly!

Q: How much is shipping?

The shipping is free for our DNA sequencing customers and those who are in San Diego, Raleigh/Durham/RTP areas. For other customers, there will be a flat fee of $15 for Fedex overnight delivery.

Q: Which purity is recommended for my application?

Our recommended purity guideline is as follows:

  1. Peptide purity >85%: immunological applications, polyclonal antibody production and nonsensitive screening.
  2. Peptide purity >90%: Structure-Activity Relationship and Bioassays.
  3. Peptide purity >95%: ELISA, enzymology, and biological related activities.
  4. Peptide purity >98%: Structural studies/Crystallography, NMR and sensitive bioassays.

Q: What would be the appropriate modification choice for my peptide terminals?

For internal protein sequence peptides, we suggest applying terminal amidation (C-terminus) or acetylation (N-terminus) in order to remove terminal charges and further imitate its natural structure (amide, CONH2). This modification secures the stability of the peptide from potential enzymatic degradation, such as exopeptidase.

Q: How to dissolve my peptide?

In general, we recommend reconstituting peptides in sterile/distilled water with sonication if necessary. If the peptide solubility problem persists, please try dissolving it by adding a small amount of 10% acetic acid solvent will to dissolve basic peptides; 10% ammonium bicarbonate will help dissolve acidic peptides. For peptides with extremely poor solubility in aqueous solutions, organic solvents should be used first (such as DMSO, isopropanol, methanol, acetonitrile). When peptide is dissolved completely at highest concentration possible, distilled water or assay buffer of your choice then can be added slowly until the desired concentration has been reached. The desired assay buffer for your experiments should only be added after the peptide is fully in solution, since salts may promote aggregation and therefore create solubility problems.

Q: How do I store my synthetic peptides?

Lyophilized peptides can be stored at room temperature for a few months. For long-term storage, lyophilized peptides should be stored at -20°C, and allow them to come to room temperature before opening. Peptide solution storage should be avoided as their shelf-life is very limited.

Q: Is C-terminal labeling of Biotin (or FITC) possible?

Yes, we can apply C-terminal labeling modification of Biotin (or FITC) by attaching a LYS residue. The Biotin (or FITC) is attached to LYS side chain via amide bond, which removes its positive charge. The cost of adding an extra LYS residue will be reflected in the quoted price.

Q: Should I consider adding a Cysteine in peptides for making antibodies?

In general, we recommend adding Cysteine in peptides as most peptides contain several Amino-Carboxyl groups that could conjugate easily, resulting in deformation and multipoint attachments. Chemical conjugation using Cysteine offers a single point attachment for sequence containing single Cysteine residue (added or native). Also, Cysteine can be used to couple peptides to Sepharose for affinity purification of antibodies. Please see below for different peptide representations:
C-terminus representation
We recommend adding Cys at the NH2 terminus as it keeps the COOH free from conjugation
N-terminus representation
We recommend adding Cys at the COOH terminus as it keeps the NH2-terminal free from conjugation
Internal representation
we recommend adding Cys to the NH2-terminus as it is easier to synthesize, however, either end can be added.

Q: What conjugation methods we have?

We offer most conjugation modifications, including BSA, OVA, THY, and KLH. A noticeable advantage for utilizing a KLH conjugated peptide is that it does not interfere with ELISA or Western Blot. For most peptide conjugation, a Cysteine residue is added for either N or C terminus for protein linkage. As a general guideline, Cysteine should be added to the less important terminus, and we will also use special method if your peptide is an internal representation.

Q: Why does my KLH/Peptide solution appear cloudy?

KLH or Keyhole Limpet Hemocyanin is a large aggregating protein (MW = 4x105 %u2013 1x107). Due to its size and structure and its limited solubility in water, the peptide solution may give a cloudy appearance. This does not affect immunogenicity of the peptide product and can be used for immunizations.

Q: What are the impurities in my peptide?

The impurities are mostly incorrectly synthesized peptide fragments/deletions, incompletely de-protected peptides and residual water.

Contact Support

If you have any questions not covered in this section, please feel free to contact us at 800.758.1630.

You may also use the form below:

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Eton Bioscience, Inc.
5820 Oberlin Drive, Suite 108
San Diego, CA 92121
DNA Sequencing
Specialty DNA Sequencing
Direct Sequencing
Genomic Services
Fragment Analysis
Mammilian Cell Expression
Peptide Synthesis
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