Frequently Asked Questions: Custom Peptide Synthesis
PEPTIDE PURITY & CONTENT
PEPTIDE STORAGE & SOLUBILITY
- What methods do you use to synthesize peptides?
- What if there is a problem with the synthesis of my peptide?
- What is the maximum peptide length GenScript can synthesize?
- What quality control data is provided by GenScript?
- In what direction are peptides synthesized?
- What are the applications of peptide libraries?
- Can you provide cGMP-grade peptides?
What is the typical turnaround time for peptide synthesis at GenScript?
The turnaround time may vary depending on the peptide length and complexity of synthesis. Our typical turnaround time is about 3 weeks. Currently, we are offering an Express Peptide Synthesis Service shipped in 5 days.
How may I place my order?
GenScript needs the sequence, desired desired purity and quantity, and also preferred payment information. If you have a purchase order (PO) number or credit card, you can place the order directly online using our secure server. Alternatively, you can send us the required information by email and fax us the PO. Our technical account manager will contact you within 24 hours to confirm your order. Feel free to use our Secure Instant Online Quotations for all peptide orders up to 1000 mg.
How much does it cost to ship a peptide outside the US?
GenScript ships peptides to many countries. The overseas shipping charge is } per shipment for most countries.
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 purchase order (PO). GenScript may require a deposit for certain orders.
How do you ship peptides? What data will be provided?
All peptides are lyophilized and shipped in 2 ml microcentrifuge tubes. Large amounts of peptides may be aliquoted into several tubes upon request. For each peptide, QC reports containing the amino acid sequence, modification information, peptide purity, mass spectrum, and HPLC chromatogram will be provided.
What is peptide purity?
The purity of GenScript's catalog peptides is usually about 95%. This means that 95% of the NET PEPTIDE CONTENT (DIFFERENT FROM TOTAL NET PEPTIDE CONTENT, see question 9) is composed of your target peptide. The other 5% of the PEPTIDE material in your sample is usually composed of 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 omitted from some of the synthesized molecules. Purity is usually determined by reverse-phase HPLC.
How pure does my peptide need to be?
Peptide purity requirements depend on your specific application. GenScript can synthesize peptides with up to 98% purity. Below is a general guideline for peptide purity requirements:PurityApplication>70%Immunological assays and polyclonal antibody production>85%NMR, Bioassays, Epitope mapping>95%SAR studies, In vitro bioassays such as ELISA, Enzymology, Receptor-ligand interactions>98%Crystallography, cGMP peptides
What methods do you use to purify the synthesized peptides?
HPLC is used for peptide purification.
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 N element analysis. Net peptide content should not be confused with purity. Purity is defined as the percentage of the target peptide sequence in the peptide component of your sample.
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 the molecular weight of the peptide by the sum of the molecular weight and the number of trifluoroacetate counterions that are required to neutralize the peptide. The sum is multiplied by the molecular weight of the TFA counterion (MW= 114). For example, a synthetic peptide with the MW=100, a free N-terminal amino group and one Arg in the sequence has a 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. Peptide samples 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.
How should I store my peptides?
Lyophilized peptides can be stored long-term at -20°C.
What is the best way to dissolve peptides?
The solubility of a given peptide varies depending on its amino acid sequence and modifications. GenScript purifies peptides by HPLC using a water and acetonitrile gradient. Below are some general tips for dissolving peptides:
- Sonication will increase solubility.
- Add 10% acetic acid to your solvent to help dissolve basic peptides.
- Add 10% ammonium bicarbonate to your solvent to help dissolve acidic peptides.
- For peptides with extremely low solubility in aqueous solutions, try adding organic solvents (such as DMSO, isopropanol, methanol, or acetonitrile) first. Once the peptides are completely dissolved, water may be gradually added until the desired concentration is obtained.
What is a counterion?
In chemical terms, a counterion is an ion of opposite charge to another ion in a solution or an electrochemical system. In peptide synthesis, counterions such as TFA are used for solubility and HPLC separation. Specifically, peptides lacking basic amino acids, such as Arg, His and Lys or containing blocked N-termini, require TFA for protonation and hence, are obtained as TFA salts. GenScript provides a guaranteed TFA removal service.
In some cases TFA couterions may be harmful to biological assays (see Top 5 reasons peptide assays fail). GenScript can replace TFA counterions with acetate or HCl, upon requesting our TFA removal service.
What methods do you use to synthesize peptides?
We use the latest peptide synthesis technologies. Specifically, we use a combination of solid (SPS) and liquid phase synthesis (LPS), as well as microwave-assisted, recombinant and ligation technologies via our FlexPeptide™ Technology Platform. This platform allows us to flexibly choose the most appropriate synthesis method for synthesizing high quality peptides for your project.
What if there is a problem with the synthesis of my peptide?
Each peptide has specific characteristics and the outcome of a synthesis attempt cannot always be anticipated. If for some reason we cannot deliver your peptide on time, we will inform you as soon as possible. However, GenScript has a 95% synthesis success rate for custom peptides and can deliver even the most complex peptides.
What is the maximum peptide length GenScript can synthesize?
GenScript can synthesize peptides up to 200 aa in length. 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.
What quality control data is provided by GenScript?
Quality assurance documentation provided with every GenScript custom 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.
In what direction are peptides synthesized?
Peptides are synthesized from the C-terminus to the N-terminus of the sequence.
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.
Can you provide cGMP-grade peptides?
GenScript provides large-scale cGMP-grade peptide services with a capacity of up to 2 kilograms per project. Our comprehensive experiences in cGMP-grade peptide synthesis for therapeutic and diagnostic applications give us an edge over the competition. We guarantee consistency, reliability, and timely delivery.
What are the 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.
GenScript is an expert in custom peptide synthesis and has been successful in synthesizing even the most complex phosphopeptides (see our phosphopeptide case studies).
Are there any requirements for introducing dye modifications into peptides?
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.
What is the advantage of capping the N and C termini of my peptide?
Capping imparts peptide sequences with more characteristics of native proteins. The N-terminus can be capped with an acetyl group and C-terminus with an amide group.
What are the advantages of PEGylation of peptides?
PEGylation is the process of adding Poly Ethylene Glycol polymer chains through covalent or non-covalent attachments. PEGylation effectively enhances the therapeutic properties of a peptide by masking it from the host's immune system, increasing its solubility (for hydrophobic drugs), and bioavailability. It can also prolong the half-life of peptides in the host circulatory system by reducing renal clearance.