Frequently Asked Questions: custom peptide synthesis |
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1. What is the typical turnaround time for peptide synthesis at GenScript?
Our typical turnaround time is about three weeks. The turnaround time may vary depending on the peptide length and complexity of synthesis.
2. How may I place my order?
GenScript needs the sequence, desired purity, desired quantity, and preferred payment information. If you have a PO (Purchase Order) number or credit card, you can place the order directly online using our secure server. Alternatively, you can send us the sequence by email and fax us the PO. If you like, you may viewSecure Instant Online Quotations for all peptide orders up to 1000 mg.
3. How much does it cost to ship a peptide outside the US?
We ship our products to many countries. The overseas shipping charge is $25 per shipment for most countries.
4. What kinds of payment do you accept?
GenScript accepts credit cards (Visa, MasterCard, American Express), checks, and wire transfers. For orders, you may send us a PO (Purchase Order). For certain orders, GenScript may require a deposit.
5. How do you ship peptides? What data will be provided?
All peptides will be lyophilized and shipped in small microcentrifuge tubes (2 ml). Large amounts of peptide may be aliquoted into several tubes. For every single peptide, data sheets containing information such as amino acid sequence, modifications, purity, mass spectrum data, and HPLC data will be provided.
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6. What is peptide purity?
The purity of GenScript’s catalog peptides is usually about 95%. This means that 95% of the NET PEPTIDE content (but not total peptide content, see question 11) of the dry powder shipped to you is composed of your target peptide. The other 5% of the PEPTIDE material in your sample is usually composed of the so-called deletion sequences that sometimes co-purify with the target peptide. Deletion sequences are generated during peptide synthesis, when due to the slight inefficiencies of the coupling reaction some amino acids are skipped in some of the synthesized molecules. Purity is usually determined by reverse-phase HPLC.
7. How pure does my peptide need to be?
That depends on your specific application. GenScript can synthesize peptides to 98% purity. Here is a general guideline for peptide purity requirements:
Purity |
Application |
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>85%
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Immunological applications and polyclonal antibody production |
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>90%
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SAR studies, bioassays |
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>95%
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In vitro bioassays such as ELISA, enzymology, biological activity |
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>98%
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NMR, crystallography, sensitive bioassays |
8. What methods do you use to purify the peptide?
HPLC is used for purification.
9. What is net peptide content?
It is important to understand the difference between net peptide content and total peptide content. The dry peptide powder shipped to you usually contains not only peptide, but also some other substances such as water, absorbed solvents, counter ions and salts. The total peptide content refers to the weight of this mixture. Net peptide weight indicates the actual weight of the peptide component of your sample. Net peptide content is usually 50-80% of the total peptide weight (also called gross peptide weight) and is usually determined by amino acid analysis or UV spectrophotometry. Net peptide content should not be confused with purity. Purity defines the percentage of the target peptide sequence in the peptide component of your sample.
10. How do you calculate theoretical net peptide content?
Theoretical net peptide content (calculated assuming that counterions are the only non-peptide components present in your peptide sample) can be estimated by dividing molecular weight of the peptide by a sum of this molecular weight and a number of trifluoroacetate counterions that are required to neutralize the peptide multiplied by the molecular weight of the TFA counterion (MW= 114). For example, a synthetic peptide of MW=1000 with a free N-terminal amino group and one Arg has theoretical net peptide content of 1000/(1000 + 2 x 114 ) = 1000/1228 =0.81 or 81%. In practice, counterions are not the only possible contaminants in the peptide sample. It can also contain water, absorbed solvents and traces of other substances. As a result, the actual net peptide content is usually determined by quantitative amino acid analysis.
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11. How should I store the peptides?
Lyophilized peptides can be stored long-term at -20°C.
12. What is the best way to dissolve the peptide?
The solubility of given peptides varies depending on their amino acid sequences and modifications. GenScript purifies peptides by HPLC using a water and acetonitrile gradient. Here are some general tips for dissolving peptides:
o Sonication will increase solubility.
o 10% acetic acid in the solvent will help dissolve basic peptides.
o 10% ammonium bicarbonate will help dissolve acidic peptides.
o For peptides with extremely low solubility in aqueous solutions, organic solvents (such as DMSO, isopropanol, methanol, and acetonitrile) should be used first. Once the peptides are completely dissolved, water may be gradually added until the desired concentration is obtained.
13. What is a counterion?
Most peptides except those that do not have basic amino acids such as Arg, Lys, His or those with blocked N-termini exist in the form of their salts. Synthetic peptides that are purified by HPLC are usually obtained as TFA salts. Their basic amino acid residues and N-termini are protonated and have trifluoroacetate (CF3COO -) counterions.
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14. What methods do you use to synthesize peptides?
For peptides with fewer than 50 amino acids, we use stepwise SPPS chemical methods. For peptides with more than 50 amino acids, we use fragment condensation, native ligation or our proprietary recombinant methods.
15. What if there is a problem with the synthesis of my peptide?
Each peptide has its specific characteristics and not all outcomes can be anticipated. If something goes wrong during the synthesis and we cannot deliver your peptide on time, we will inform you as soon as possible.
16. What is the maximum peptide length you can produce?
GenScript can synthesize peptides of length up to 200 aa . Peptides of 50-70 aa can be obtained by direct chemical synthesis. Longer peptides can be generated by chemically linking several synthetic peptide components. Proteins can also be chemically synthesized: learn more about GenScript’s chemical protein synthesis service.
17. What quality control data is provided by GenScript?
Quality assurance documentation provided with every GenScript peptide includes mass spectral and HPLC analyses determining composition and purity. Amino acid analysis is available upon request. We also provide storage and handling guidelines.
18. In what direction are the peptides synthesized?
Peptides are synthesized from the C-terminus to the N-terminus of the sequence.
19. What are the applications of peptide libraries?
Peptide libraries are efficient tools for GPCR ligand screening, protein-protein interaction studies, functional proteomics, nucleic acid binding, enzyme substrate and inhibitor screening, antigen and epitope screening, peptide/protein cross-talk studies, the discovery of signal molecules, and other processes significant to modern drug discovery.
20. Can you provide cGMP-grade peptides?
GenScript provides large-scale cGMP peptide services with capacity up to 2 kilograms per project. Our comprehensive experiences in cGMP-grade peptides synthesis for therapeutic and diagnostic applications give us an edge over the competition. We guarantee consistency, viability, and delivery.
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21. Are there any requirements for phosphopeptide design?
We recommend that you position the phosphorylated residue no more than 10 residues away from the N-terminus because the coupling efficiency of residues following a phosphorylated residue is significantly reduced.
22. Are there any requirements for introducing dye modifications?
We recommend that you add a spacer between the peptide and the dye molecule. This will reduce the chance of the dye affecting peptide folding and binding to receptors. However, if the purpose of the dye labeling is to quantify fluorescence transfer between different structures spacers should not be introduced.
23. What is the advantage of capping the N and C termini of the peptide?
Capping will make peptide appear more like native protein. The N terminus can be capped with an acetyl group and C terminus with an amide group.
24. What are the advantages of PEGylation of peptides?
PEGylation adds poly (ethylene glycol) polymer to target molecules through covalent attachments. PEGylation effectively enhances the peptides’ therapeutic properties by masking them from the host’s immune system, increasing their solubility (for hydrophobic drugs) and bioavailability. It can also prolong the peptides circulatory time within the host through reduced renal clearance.
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