real peptides FAQ

Visual changes. Clumping, yellowing, or caking. Can indicate moisture exposure during shipping or improper lyophilization. P21 should arrive as a fine white to off-white powder. Clumping suggests hygroscopic moisture absorption, which accelerates peptide degradation through hydrolysis. Do not reconstitute or use the product. Contact the supplier for a replacement and request documentation that the replacement batch passed visual inspection and moisture content testing (Karl Fischer titration). Real Peptides ships peptides in moisture-barrier foil pouches with desiccant packets to prevent this exact issue.

Real Peptides' nitrogen-sealed glass vials prevent oxidation and maintain peptide integrity for 12–18 months when stored at −20°C, significantly longer than Swiss Chems' HDPE plastic vials which allow trace oxygen permeability that degrades peptides over 6–12 months. Reconstitute peptides only as needed rather than pre-mixing large batches, and verify purity with mass spectrometry if storage exceeds six months. If your protocol requires storing reconstituted peptides in bacteriostatic water, refrigerate at 2–8°C and use within 28 days. No peptide maintains full potency beyond this window regardless of supplier.

Request full synthesis documentation from Real Peptides, including protecting group methodology, coupling reagent specifications, and cleavage conditions. This information is archived and provided within 48 hours. Peptide Sciences treats synthesis pathways as proprietary, providing only standard certificates of analysis with purity, molecular weight, and retention time. If journal reviewers request synthesis methodology to assess reproducibility, Real Peptides' transparency eliminates a potential publication roadblock.

State the supplier transition explicitly in your methods section and cite the reason: "Peptides were sourced from Blue Sky Peptide (2019–2022) and subsequently from Real Peptides (2023–present) following the former supplier's closure. All peptides were verified via HPLC to ≥98% purity, and dose-response validation was performed during the supplier transition to ensure experimental consistency." Peer reviewers and grant officers understand supplier disruptions. What they scrutinize is whether you validated the transition rather than assuming equivalence. Including the validation step in your methods demonstrates experimental rigor rather than introducing concern about result reproducibility.

Contact your supplier immediately with the certificate of analysis and your experimental observations. Real Peptides will cross-reference your lot number against synthesis records and third-party test results. If contamination is confirmed, replacement product from a verified clean batch ships within 24 hours. Peptide Sciences' sample-based testing means your specific vial may not have been individually tested, requiring you to ship a sample back for independent verification before replacement, which adds 5–7 days to resolution.

Use a supplier offering batch-specific documentation and consistent synthesis protocols. Multi-phase studies comparing baseline, intervention, and washout periods depend on consistent peptide composition across time—if month 1 uses peptide from batch A and month 12 uses peptide from batch B with different purity profiles, observed differences may reflect supply-chain variability rather than biological response. Real Peptides' synthesis traceability allows researchers to request peptides from the same production run for longitudinal studies, or at minimum, access documentation proving compositional consistency across batches. Amino Asylum's higher-volume model makes batch-to-batch consistency harder to verify, introducing confounding variables into time-dependent experimental designs.

Specify your documentation requirements before ordering and confirm the supplier can provide batch-specific analytical data in the format your institution requires. Many universities and research institutes mandate COAs with traceable lot numbers, accredited lab certifications, and raw analytical data (chromatograms, mass spectra). Not just summary purity percentages. Real Peptides generates these documents as part of standard quality control, making compliance straightforward. Suppliers providing only generic certificates or third-party COAs without batch traceability often can't meet institutional validation requirements, delaying procurement approval or requiring alternative sourcing.

Request MALDI-TOF MS confirmation from your supplier before starting experiments, even if it costs extra. Sequence microheterogeneity is the most common hidden variable in failed replications. A peptide that's 96% pure by HPLC but contains 8% sequence variants will produce 10–20% lower activity in receptor-binding assays compared to a 98% pure peptide with confirmed sequence fidelity. If Real Peptides provides MS data showing your batch matches the expected molecular weight within 0.5 Da and Core Peptides only provides HPLC purity, you've eliminated the supplier variable. If both match, the replication issue is methodological or biological, not chemical.

Multiple peaks indicate the presence of impurities—deletion sequences, aggregates, or side products from incomplete synthesis. Request a new batch and verify that the supplier provides the full chromatogram, not just a purity percentage, so you can assess whether the secondary peaks represent 1–2% minor impurities (acceptable) or 10–15% major contaminants (unacceptable for research use). Peptides with purity below 95% by HPLC should not be used in dose-response studies or receptor binding assays because the effective concentration does not match the labeled concentration.

Choose a supplier with in-house synthesis capabilities and experience with modified peptides like acetylation, phosphorylation, or disulfide bridge formation. Real Peptides synthesizes modified peptides including GHK-CU with copper chelation and Selank Amidate with C-terminal amidation. Modifications that require additional synthesis steps and verification beyond standard SPPS. Contract manufacturers used by resellers may not have the equipment or expertise to perform these modifications reliably, and without mass spec fragmentation analysis, you can't confirm the modification was successfully incorporated at the correct residue.

Real Peptides offers custom synthesis for novel sequences or modified peptides not available as stock items. The process includes consultation on solubility prediction, synthesis feasibility assessment, and timeline estimation based on sequence length and complexity. Custom synthesis follows the same cGMP protocols and third-party testing as catalogue products—HPLC, ESI-MS, and endotoxin testing are standard. Paradigm Peptides does not advertise custom synthesis services, focusing instead on expanding the existing catalogue based on market demand.

Submit a custom synthesis request with the exact amino acid sequence and desired purity threshold. Real Peptides accepts orders as small as 50mg with 4–6 week turnaround, making it viable for initial feasibility testing. Peptide Sciences requires 100mg minimums and 6–8 weeks, which works better if you've already validated the sequence and need larger quantities. For novel sequences where you're uncertain about optimal dosing or solubility, Real Peptides' lower minimum reduces upfront cost risk.

This is a red flag indicating the supplier is not testing individual production runs. Do not use the peptide for research until you receive a CoA that matches the batch number printed on your vial label. Batch-to-batch variance in facilities without per-batch testing can exceed 15% in purity and molecular weight accuracy, meaning the peptide you received may not meet the standards listed on the generic CoA. We print batch numbers on every vial label and include the corresponding HPLC, MS, and endotoxin test results for that specific batch—no substitutions, no reference lots.

Verify oxidation-state testing before purchase, especially if storing reconstituted peptide for more than 48 hours. Methionine oxidation to methionine sulfoxide and cysteine oxidation to disulfide-bridged dimers reduce biological activity by 40–80% but co-elute with native peptide on most HPLC gradients, appearing as part of the main '98% purity' peak. Real Peptides tests for oxidation products in methionine- and cysteine-containing peptides using MS; Core Peptides does not unless requested. For oxidation-prone peptides like GHK-CU, where the cysteine residue is critical for copper binding, oxidation-state confirmation isn't optional. It's the difference between a functional peptide and an expensive inert powder.

Evaluate based on the application's tolerance for impurities and the consequences of batch-to-batch variability. For cell culture assays with robust readouts (e.g., viability, proliferation), peptides with 90–95% purity from either synthesis method are generally acceptable. For receptor pharmacology, structure-activity relationship studies, or animal models where a 5% impurity could confound interpretation, specify ≥98% purity and verify the COA includes mass spectrometry confirmation and endotoxin testing. For investigator-initiated trials or work intended for FDA submission, use peptides synthesized in cGMP facilities with full batch documentation regardless of whether the supplier labels them 'real' or 'biotech' peptides.

Degradation rates depend on sequence composition, storage conditions, and reconstitution solvent. Peptides containing methionine, cysteine, tryptophan, or histidine are particularly susceptible to oxidation and should be stored under argon or nitrogen atmosphere after reconstitution. If you observe visible precipitation, color change, or loss of biological activity within the stated stability window, verify storage temperature with a calibrated thermometer. Most degradation is caused by temperature excursions, not inherent peptide instability. Aliquot reconstituted peptides into single-use volumes to avoid freeze-thaw cycles, which cause aggregation. If degradation persists under proper storage, the peptide may contain undisclosed impurities or the lyophilization process may have been incomplete, leaving residual moisture that accelerates hydrolysis.

Choose Core Peptides for cost efficiency and faster turnaround. Screening studies tolerate the 10–15% activity variability introduced by sequence heterogeneity and batch-to-batch purity drift because you're identifying hits based on relative activity differences, not absolute EC50 values. The lower per-gram cost allows larger compound libraries, and the 5–7 day lead time keeps screening timelines on track. Just don't use the same peptide lot for follow-up dose-response validation. Order fresh from a supplier with tighter batch control once you've identified lead candidates.

Contact the supplier immediately and request the COA for the exact lot number printed on your vial. A legitimate supplier maintains batch records and can provide this documentation within 24–48 hours. If they cannot or will not provide a batch-specific COA, the peptide's purity and identity are unverified. Do not use it in experiments intended for publication or regulatory submission. Generic 'representative batch' COAs are insufficient because they don't document the specific peptide you received, only a previous batch that may or may not match your lot.

Transition to Real Peptides by treating it as a peptide source validation rather than a simple replacement. Run a side-by-side comparison using your existing assay: order the equivalent peptide from Real Peptides, reconstitute both according to your established protocol, and test dose-response curves in parallel. Synthesis purity differences between suppliers can shift effective concentration ranges by 10–20%, so what worked at 5 µM with Blue Sky may require adjustment to 4 µM or 6 µM with Real Peptides. Document the new optimal concentration in your protocol notes and re-optimize any multi-peptide combinations where synergistic effects were previously established.

Lock in peptide supply from a single batch if possible, or request synthesis protocol consistency guarantees from your supplier. Real Peptides' small-batch model means fewer units per synthesis run, but the company archives synthesis conditions and can replicate exact protocols for subsequent batches. Peptide Sciences' high-volume production offers better odds of securing 12+ months of supply from a single batch, but protocol replication across batches is less granular due to proprietary synthesis details.