# Sermorelin vs CJC-1295 No DAC: Native GHRH(1-29) Against Its Hardened Analogue > Four substitutions separate the native fragment from Modified GRF 1-29. What each one prevents, and when a lab should prefer one over the other. Web page: https://peptidemedixeu.com/en/learn/cjc-1295-no-dac-vs-sermorelin/ · Peptide Medix EU · 8 min read · Updated: 2026-01-08 [Sermorelin](https://peptidemedixeu.com/en/products/sermorelin/) reproduces native GHRH(1-29); CJC-1295 without DAC is those same 29 residues with four positions intentionally swapped. The changes at positions 2, 8, 15 and 27 shut down three particular degradation pathways: cleavage by dipeptidyl peptidase-4, deamidation of asparagine and oxidation of methionine. They add only 10 g/mol, moving the mass from 3357.93 to 3367.93. Comparing CJC-1295 with sermorelin therefore comes down to whether the protocol needs the native sequence as its biological benchmark or a toughened analogue that emerges from handling and assay conditions unaltered. Both arrive as lyophilized powder in 2, 5 and 10 mg vials with lot-matched HPLC certificates: CJC-1295 (No DAC / [Mod GRF 1-29](https://peptidemedixeu.com/en/products/cjc-1295-no-dac/)) and sermorelin, both within GHRH analogs. Both are research chemicals for in-vitro and preclinical laboratory work only. ## One receptor, one fragment, one hardened version Endocrine research long ago showed that the first 29 residues of the 44-residue hormone hold practically all the receptor-binding information, which is why GHRH(1-29) rather than the full hormone became the routine laboratory tool. Sermorelin is that fragment copied exactly: the native sequence with a C-terminal amide and nothing else altered. CJC-1295 without DAC, properly named Modified GRF 1-29, is an analogue of the same fragment. Each of its four substitutions is a targeted repair rather than an attempt to change receptor behaviour, and knowing what each one does explains most of the practical gap between the two compounds. ### Position 2: stopping DPP-4 Dipeptidyl peptidase-4 strips the first two residues from native GHRH within minutes, wrecking the N-terminus the receptor needs. A D-amino acid at position 2 blocks that cleavage sterically. Wherever an assay runs in serum, plasma or a tissue preparation with native peptidase activity, this is the decisive substitution: sermorelin degrades measurably during a long incubation while the analogue does not. ### Position 8: eliminating a deamidation site Asparagine deamidates spontaneously in water, becoming aspartate with a 1 Da mass gain and a change in charge. Swapping the asparagine at position 8 closes that route. A 1 Da shift is easy to miss on a mass spectrum, yet it produces a chemically distinct species with different isoelectric behaviour. ### Position 15: conformational stabilisation The change at position 15 is described as reinforcing the peptide's helical character rather than blocking any particular degradation reaction. ### Position 27: taking out the methionine This substitution is the one you can see in the molecular formulas. Sermorelin's formula includes a single sulfur atom; the analogue's does not, because its methionine has been replaced. Methionine oxidises more readily than any other residue in stored peptides, turning into the sulfoxide with a 16 Da mass gain on exposure to air, light, trace metals and time. Removing it eliminates the molecule's biggest storage weakness. ## Consequences for experimental design None of the four substitutions changes the receptor, and both compounds are used to study the same things: signalling at the pituitary GHRH receptor, cyclic-AMP accumulation and the pulsatile release of growth hormone in intact animal preparations. What differs is how much intact compound remains when the experiment ends. In [brief in-vitro](https://peptidemedixeu.com/en/glossary/in-vitro/) work using defined buffer the two are nearly interchangeable, and sermorelin's native sequence is arguably the better choice, since it is the ligand the receptor evolved to recognise. For longer experiments, work in serum, or any case where one stock is used over weeks, the analogue is more dependable purely because it has fewer routes to becoming something else. Sermorelin's insidious failure mode is that its degradation products are not inert: a methionine sulfoxide or a deamidated variant is still a peptide, still elutes close to the parent and may keep part of its activity. A slow drift in potency over a long study is therefore easily blamed on biology when the cause is chemistry. Groups using sermorelin over extended periods should re-check the stock instead of assuming it is unchanged. ## Matching the compound to the question ### Use sermorelin as the biological benchmark When the study calls for the native ligand, whether to establish baseline receptor pharmacology, to generate a reference concentration-response curve or to serve as the yardstick for analogues, sermorelin is the right material. It also suits replication of older endocrine studies, most of which used the native fragment. Sermorelin has, in addition, a regulatory history that most [research peptides do not](https://peptidemedixeu.com/en/learn/research-catalog-type-peptides/): a sermorelin product was once marketed as a prescription medicine in the United States and has since been withdrawn. That history belongs to the regulated pharmaceutical article, not to research-grade powder. ### Use the modified analogue as the working tool For assays containing serum, multi-week animal protocols, long-standing stock solutions or any design where degradation would muddy the readout, Modified GRF 1-29 is the sturdier option. It is also the usual comparator in structure-activity studies asking how much a GHRH fragment can be altered before receptor behaviour shifts. ### Run both when stability itself is the variable Together they form a tidy two-point series: same receptor target, same chain length, four defined substitutions. Testing them under identical conditions directly separates intrinsic pharmacology from survival in the assay as explanations for an apparent potency gap. The series extends further: tesamorelin puts an N-terminal trans-3-hexenoyl group on the same fragment (see tesamorelin vs sermorelin), and [CJC-1295 with DAC](https://peptidemedixeu.com/en/products/cjc-1295-dac/) layers covalent albumin conjugation onto the same substituted backbone. ### Add a secretagogue for combination designs Because GHRH analogues and ghrelin-receptor secretagogues hit different receptors, the two are frequently paired. We stock [ipamorelin on its own](https://peptidemedixeu.com/en/products/ipamorelin/) as well as co-formulated sermorelin with ipamorelin and CJC-1295 with ipamorelin vials; our survey of the secretagogue landscape shows how the family relates. ## Handling, reconstitution and storage Both follow standard practice: keep sealed lyophilized vials frozen, warm them to room temperature before piercing the stopper so moisture does not condense on cold powder, reconstitute by letting diluent run down the vial wall, dissolve without shaking and aliquot so the stock is not frozen and thawed repeatedly. Within that routine sermorelin demands extra attention, and the methionine is why. Oxidation is hastened by dissolved oxygen, light and trace metal ions, so prepare sermorelin solutions fresh, keep them dark and do not leave them standing in half-empty tubes full of headspace oxygen. Deamidation is base-catalysed, so avoid keeping sermorelin in alkaline buffer for long periods too. The modified analogue is largely untroubled by any of this. Concentration is a lab calculation rather than a usage recommendation: 5 mg reconstituted in 2 mL of diluent gives 2.5 mg/mL, or 2,500 mcg/mL, so 0.1 mL holds 250 mcg. As the two masses differ by just 10 g/mol, about 0.3 percent, mass and molar concentrations are effectively equivalent between them, which makes molar-matched comparison unusually simple. See our reconstitution guide and storage guide. ## Purity, identity and certificate checks Ask for the lot-matched certificate with each vial and confirm HPLC purity against a [visible chromatogram](https://peptidemedixeu.com/en/blog/read-peptide-coa-like-chemist/), a mass spectrometry figure matching the expected value (3367.93 g/mol for the analogue, 3357.93 g/mol for sermorelin) and a lot number matching the vial. With sermorelin, watch for a satellite peak 16 Da above the parent, signalling methionine sulfoxide, and for a 1 Da shift signalling deamidation; both are frequent in aged material and neither shows up in a purity percentage. For the analogue, the useful confirmation is the absence of sulfur in the formula, which tells it apart from the native fragment beyond doubt. Our COA guide describes what a complete document contains. ## Regulatory framing Both are supplied as research chemicals for laboratory use only. Modified GRF 1-29 holds no approved status in any jurisdiction. Sermorelin's prescription history in the United States relates to a discontinued pharmaceutical product; that status attaches to the regulated article rather than to research-grade powder. For wider context see our growth and performance research overview. ## Frequently asked questions ### How does CJC-1295 without DAC differ from sermorelin? Sermorelin is unmodified native GHRH(1-29) amide. CJC-1295 without DAC, correctly called Modified GRF 1-29, is the same 29-residue fragment carrying four substitutions at positions 2, 8, 15 and 27, each closing off a specific degradation pathway. Both act at the same pituitary GHRH receptor. ### Why does only sermorelin's formula include sulfur? Sermorelin keeps the methionine at position 27 while the analogue replaces it. Methionine oxidises more easily than any other residue in stored peptides, becoming the sulfoxide with a 16 Da mass increase when exposed to air, light and trace metals. Removing it takes away the molecule's greatest storage liability. ### Which holds up better in a serum-containing assay? The modified analogue, clearly. Its position 2 substitution blocks dipeptidyl peptidase-4, which otherwise clips the first two residues off native GHRH within minutes and ruins the N-terminus the receptor depends on. Sermorelin degrades noticeably during a long serum incubation. ### Do the substitutions alter which receptor is targeted? No. All four aim at chemical robustness rather than receptor interaction, and both compounds act at the pituitary GHRH receptor. Structure-activity work with this pair asks how much modification a GHRH fragment tolerates before its behaviour shifts, not whether the target changes. ### Can both be used at the same molar concentration? Yes, and more easily than with most pairs. At 3367.93 versus 3357.93 g/mol they differ by 10 g/mol, roughly 0.3 percent, so mass and molar concentrations are practically interchangeable, making molar-matched side-by-side preparation simple. ### What should a sermorelin certificate of analysis be checked for? A satellite peak 16 Da above the parent mass, indicating methionine sulfoxide, and a 1 Da shift indicating asparagine deamidation. Both appear often in aged material, both elute near the main peak, and neither can be spotted from a purity percentage alone. ### Is sermorelin a licensed medicine? A sermorelin product was formerly sold as a prescription medicine in the United States and has since been discontinued. That status belongs to the regulated pharmaceutical article, not to research-grade powder, and the material supplied here is a research chemical for laboratory use only. ## Related products - [Sermorelin](https://peptidemedixeu.com/en/products/sermorelin/): from €38 --- For laboratory research use only. This page is provided for scientific and educational information. Materials referenced here are sold strictly for in-vitro laboratory research by qualified professionals — not for human or veterinary use, and nothing on this page is medical advice.