We've been sourcing custom peptides from GL Biochem (Shanghai) for about three years now across multiple NIH-funded projects. Figured I'd write up a proper review since there's surprisingly little discussion about them here despite being one of the largest peptide manufacturers globally. Background: GL Biochem was founded in 2001 and has grown to 1,500+ employees with ISO 9001:2015 and cGMP-certified facilities in Shanghai. They supply to major pharma including Roche and Merck — which is partly why we initially chose them. Custom synthesis experience: - Ordered 14 custom sequences ranging from 8-mer to 42-mer over the past 3 years - Purity specs met or exceeded on 13/14 orders (one 38-mer came in at 93.2% vs requested >95%, resolved with re-synthesis) - Turnaround: typically 2-3 weeks for standard sequences, 4-6 weeks for longer/difficult ones - HPLC and MS data included with every shipment — always consistent with our in-house QC verification Pricing: Roughly 15-25% more expensive than the cheapest Chinese suppliers, but significantly less than US/EU custom synthesis houses. For a typical 15-mer at >95% purity, we're paying around $3.50-4.50/mg at 50mg scale. Overall, very solid for academic research applications. Happy to answer questions.

Good write-up. We've had a similar experience at our core facility. A few things I'd add: > Turnaround: typically 2-3 weeks for standard sequences This has been our experience too, though I'll note that around Chinese New Year (late Jan/Feb) you should plan for significant delays. We've had orders slip 3+ weeks during that period. Now we front-load orders in December to avoid the bottleneck. One thing that really sets GL Biochem apart from smaller suppliers is their technical support. When we had a difficult cyclic peptide with two disulfide bridges, their chemistry team actually engaged with us on the synthesis strategy before we placed the order. That level of pre-project consultation is unusual for a supplier at their price point. We also use them for isotope-labeled peptides (13C, 15N) for our NMR facility. Quality has been excellent — isotopic enrichment consistently >98%.

How does their documentation hold up for publication? We had an issue with another Chinese supplier where the CoA data was... let's say inconsistent with what we saw on our own instruments. Our PI is now requiring independent QC verification for any externally sourced peptides, which adds cost and time. Also curious about their modification capabilities. We need some non-standard modifications — PEGylation, fluorescent labeling (FITC, TAMRA), biotin conjugation. Have you used them for anything beyond standard Fmoc synthesis?

Good questions. Documentation quality: Their CoAs are thorough — you get analytical HPLC chromatogram, MS spectrum (ESI or MALDI depending on size), and a detailed spec sheet. In our experience, the data has been consistent with in-house verification. We routinely run our own analytical HPLC as standard practice and the purity values have typically agreed within +/- 1.5%. I wouldn't say the documentation is at the level of, say, a Bachem CoA, but it's more than adequate for academic publications. We cite them as the source and include our own QC data in supplementary materials. Modifications: Yes, we've used them for: - FITC-labeled peptides (4 orders, all good) - Biotin-Ahx conjugates (2 orders, fine) - Phosphopeptides (pSer, pThr — 3 orders, reliable) - One PEGylated peptide (PEG2000) — this one took longer (~5 weeks) but came out well Haven't tried stapled peptides or more exotic chemistries with them yet. Their catalog lists D-amino acid substitutions and various N-terminal modifications as standard offerings.

I'll offer a slightly different perspective as someone who's been in peptide chemistry for 20+ years. GL Biochem is a perfectly competent large-scale supplier, but people should understand what they're getting. Their strength is volume and reliability at scale. They have something like 200+ peptide synthesizers running at any given time. For standard sequences, standard modifications, and reasonable purity requirements, they're excellent. Where I've seen limitations: 1. Very long peptides (>50-mer): Success rate drops. This isn't unique to GL Biochem — it's a fundamental chemistry challenge — but specialized boutique labs sometimes have better strategies for difficult sequences. 2. Novel/unusual modifications: They tend to stick to well-established chemistry. If you need something truly cutting-edge (e.g., new click chemistry conjugates, non-standard cyclization strategies), a specialized CRO might serve you better. 3. Speed for urgent orders: Their process is optimized for throughput, not speed. If you need something in <1 week, look elsewhere. That said, for 90% of what academic labs need, GL Biochem delivers consistently. Their partnership history with companies like Roche and Merck isn't just marketing — those relationships require passing rigorous vendor qualification audits.