Answers to common questions about custom peptide synthesis, including peptide purification, expected impurities, D-amino acid synthesis, KLH/BSA conjugation, crude purity, HPLC and LC-MS quality control, peptide shipping, storage, Fmoc SPPS, and peptide solubility.
This FAQ provides practical information about Alan Scientific's custom peptide synthesis, including peptide purification, expected impurities, conjugation, D-amino acid synthesis, purity, quality control, shipping, storage, Fmoc solid-phase peptide synthesis, and peptide solubility.
Synthetic peptides supplied through Alan Scientific are generally purified by preparative HPLC using a water/acetonitrile gradient. The purpose of purification is to separate the desired peptide from synthesis-related and process-related impurities.
Depending on the sequence and purification process, potential residual impurities may include water, salts, TFA, trace solvents, truncated peptide sequences, and incompletely deprotected species. The final peptide purity is evaluated by analytical HPLC, while mass spectrometry is used to confirm molecular mass.
For representative analytical data, see our Peptide Quality Control Reports.
Yes. KLH or BSA conjugation can be performed even when the peptide sequence does not contain cysteine. However, without a designated cysteine residue, the conjugation site cannot be controlled as precisely and the conjugation efficiency may be lower.
For this reason, we generally recommend adding a cysteine residue to the peptide sequence when the peptide is intended for KLH or BSA conjugation.
Yes. Our custom peptide synthesis service supports all-D peptide sequences.
The estimated turnaround time is generally approximately 2–3 weeks, although the exact schedule depends on the peptide sequence, length, purity requirement, and synthesis difficulty.
D-amino acid peptides are more expensive than corresponding L-amino acid peptides. As a general estimate, an additional $30 per D-amino acid residue may apply compared with standard amino acids.
Alan Scientific does not guarantee a specific purity level for crude peptides. Crude purity can vary substantially depending on peptide length, sequence composition, coupling efficiency, aggregation, and other synthesis-related factors.
Analytical HPLC is used to determine the actual crude purity of a synthesized peptide. If a defined purity specification is required for your experiment, purified peptide should be selected instead of crude material.
For help selecting a suitable purity level, see our Recommended Peptide Purity guide.
Peptides are generally lyophilized and shipped in small microcentrifuge tubes at room temperature.
For larger quantities, the peptide can be aliquoted into multiple tubes upon request. Each peptide is supplied with supporting information that may include the amino acid sequence, peptide purity, mass spectrometry data, HPLC data, and applicable modifications.
Lyophilization helps provide a convenient format for peptide transportation and subsequent storage before reconstitution.
Lyophilized peptides should generally be stored dry, tightly sealed, and protected from strong light.
For short-term storage, lyophilized peptides may be stored at approximately 4°C for one week to two months. For longer-term storage, −20°C is recommended.
Once a peptide has been dissolved, the solution should be used as soon as practical because solution stability can differ significantly depending on the peptide sequence, concentration, solvent, pH, and modifications.
Alan Scientific provides batch-specific HPLC, MS and COA documentation for peptide products as part of the quality control process.
Analytical HPLC is used to assess chromatographic purity, while mass spectrometry supports identity assessment by comparing the observed and expected molecular mass. Applicable results are documented in the Certificate of Analysis. Additional testing is specified according to project requirements.
Representative reports are available on our Peptide Quality Control Report page.
Fmoc-based solid-phase peptide synthesis is a widely used strategy for stepwise peptide assembly on a solid support, commonly referred to as a resin.
The resin contains a linker that provides the attachment point for the first amino acid. Additional amino acids are then sequentially coupled through formation of amide bonds between amino and carboxyl groups.
To minimize unwanted reactions, temporary protecting groups are used during synthesis. Fmoc (9-fluorenylmethoxycarbonyl) is commonly used to protect the Nα-amino group, while suitable protecting groups are used for reactive amino acid side chains.
A major advantage of the Fmoc strategy is the relatively mild deprotection condition. Fmoc removal can be performed using approximately 20–50% piperidine in DMF, while side-chain protecting groups remain intact under these conditions.
The release of the Fmoc group can also be monitored spectrophotometrically at approximately 300–320 nm, allowing the progress of deprotection to be followed.
After the desired peptide sequence has been assembled, the peptide is deprotected and cleaved from the resin, commonly using TFA under Fmoc-compatible acid-labile linker conditions.
For a broader introduction, see our Peptide Synthesis Overview.
There is no single solvent that works for every peptide. Peptide solubility depends strongly on the amino acid sequence, overall charge, hydrophobicity, concentration, and chemical modifications.
Several general approaches may help improve peptide dissolution.
Sonication can improve dissolution of some peptides by increasing dispersion in the solvent.
Select the reconstitution conditions for the specific peptide and intended assay. Begin with a small-scale solubility test and document the solvent composition, concentration and final assay conditions. See our peptide reconstitution guide for a stepwise approach.
For peptides with very low aqueous solubility, an organic solvent such as DMSO, isopropanol, methanol, or acetonitrile may be used initially. Once the peptide is dissolved, water can be gradually added until the desired concentration or solvent composition is reached.
Because peptide solubility is highly sequence dependent, customers may also request a peptide solubility test when placing an order if solubility information is important for the planned experiment.
Yes. A peptide solubility test can be requested when placing an order.
This service may be particularly useful for hydrophobic peptides, modified peptides, or projects in which a specific experimental solvent or peptide concentration is required.
Please include the solubility-test request and any relevant solvent or concentration requirements when submitting the peptide synthesis order.
Alan Scientific works with qualified manufacturing and analytical partners selected according to project requirements and product specifications. Our quality process includes supplier qualification, batch-specific analytical review, and documentation such as HPLC, mass spectrometry, and Certificates of Analysis (COAs), as applicable.
Where relevant to a specific project, manufacturing or analytical partners may operate under ISO-certified quality systems. Supporting quality or certification documentation can be provided upon request when available.