LY3298176 is supplied across more strengths than almost anything else in this catalogue, which makes vial sizing a real decision rather than a formality. The molecule is identical across all of them. What changes is how much of it is in the vial, and therefore how long an opened vial has to last.
This guide covers choosing a strength, reading the certificate for this compound specifically, and the three things that genuinely differ between suppliers offering what looks like the same product.
What LY3298176 is, structurally
A synthetic peptide engineered to engage two incretin receptors rather than one, built on a backbone related to naturally occurring incretin sequences with substitutions that change receptor engagement and resistance to the enzymes that would otherwise clear it quickly. GLP-1 and incretin peptides covers the class it belongs to.
It also carries a fatty-acid chain attached to the backbone. That modification binds albumin and extends how long the molecule circulates, and it dominates the physical behaviour of the material in ways the receptor profile does not. NN9535, LY3298176 and LY3437943 compared sets the three side by side.
The LY3298176 sequence written out
In one-letter code, with Aib standing for α-aminoisobutyric acid, the 39 residues run Y-Aib-E-G-T-F-T-S-D-Y-S-I-Aib-L-D-K-I-A-Q-K-A-F-V-Q-W-L-I-A-G-G-P-S-S-G-A-P-P-P-S, ending in a C-terminal amide. That is the backbone read from the chemical structure in PubChem CID 166567236, a record that carries the depositor-supplied synonym LY3298176 and the CAS number 2023788-19-2; the record gives a structure rather than letter code, so the letters here are a transcription of it.
The 2018 paper describing its discovery (Coskun and colleagues) gives the same features in words: a 39 amino acid linear peptide with the non-coded residue Aib at positions 2 and 13, a C20 fatty diacid attached through a linker to the lysine at position 20, and an amidated C-terminus. Counting along the sequence above, the lysine at position 20 is the second of the two; the one at position 16 is unmodified.
Choosing a strength
Larger vials are cheaper per milligram and that saving is only real if the material is used before it degrades. For a compound supplied across seven strengths, the right question is not which is cheapest per milligram but which one a single piece of work consumes.
| Situation | Favours | Why |
|---|---|---|
| Evaluating a new supplier | The smallest strength | A first order is a test, not a commitment |
| Steady, predictable consumption | A larger strength | Per-milligram saving is realised |
| Occasional or exploratory work | The smallest strength | Avoids holding material that ages out |
| Several parallel pieces of work | Multiple smaller vials | Fewer entries per vial, less exchange of air |
| Long lead time on resupply | Mid strength, ordered earlier | Stock, not size, solves a lead-time problem |
The sizing question is consumption, not unit price. A vial half discarded was bought at full price.
Inventory levels and reorder points covers deriving that from measured consumption rather than from an estimate, and minimum order quantities covers what to do when the smallest order available exceeds what you can use.
What the certificate should show
The same panel as any other research peptide, read in the same order. Lot number first, against the vial. Then the two dates, which must run forwards. Then identity, then content, then purity.
For a long modified peptide like this one, the identity method matters more than it does for a short sequence. A single intact mass confirms the mass is consistent with the molecule. A method that fragments it and reads a ladder establishes considerably more, and mass spectrometry and peptide identity covers the difference.
For LY3298176 specifically, the identity mass should reconcile with 4813.45 g/mol, the molecular weight in the catalogue record for the 39-residue molecule (formula C225H348N48O68). That figure is an average mass. At this size the average and monoisotopic values sit roughly three daltons apart (PubChem lists a monoisotopic mass of 4810.52 for the same formula), so a certificate should state which basis its observed mass is on before the two numbers are compared. Molecular weight covers the two conventions.
The sequence matters to that line because the expected mass is not the mass of 39 ordinary amino acids. C225H348N48O68 is the formula of the whole molecule in the PubChem structure: the two Aib residues, the fatty diacid and its linker on the lysine at position 20, and the amidated C-terminus are all inside it. An observed mass that reconciles with the expected figure is therefore consistent with the modified molecule as a whole, and a figure worked out from the bare peptide chain would not match it. What an intact mass does not show is which lysine carries the chain: a structure built from the same parts with the side chain on a different lysine would have the identical formula and monoisotopic mass.
The seven listed strengths (10, 15, 20, 30, 60, 100 and 200 mg) are the same molecule, so the same lot-matched certificate checks apply to each. What changes with size is that a larger vial concentrates more value behind one certificate.
Content, and why the label is the wrong number
The strength on the label is nominal. The certificate reports a measured mass of peptide, and fills are generally set to meet or slightly exceed the label, so the measured figure is often a few percent higher.
At these strengths a few percent is a real quantity, and it belongs in any calculation rather than the label figure. Net peptide content covers why the two differ.
Three things that genuinely vary between suppliers
- Whether the certificate names your lot or the product line. The first documents the vial you will receive; the second documents a vial someone else received.
- Whether identity is established by a method that reads a sequence, or only by a mass. Both are legitimate and they are not equivalent.
- Which salt form is supplied, which changes the mass of powder in the vial without changing the peptide. It is rarely on the certificate and it is always answerable by asking.
Comparing suppliers on documentation is the scoring method these roll up into, and it needs one email.
Reconstitution, and why this compound is slow
The acyl chain that extends circulation also makes the molecule more hydrophobic than its residue composition suggests. That is why LY3298176 and its class-mates are among the slower compounds in any catalogue to dissolve.
Material that appears not to be going into solution is usually behaving exactly as expected and needs time rather than force. Shaking drives air into a solution, and the air-water interface is where peptides unfold and associate, which is why foaming is read as a sign of stress on the material.
Why some peptides resist dissolving covers the mechanism, and reconstitution solvents compared covers choosing a diluent.
Storage, before and after reconstitution
As a sealed dry solid this material is comparatively robust, because the water that most degradation routes need has been removed. The clock that matters starts at reconstitution rather than at delivery.
Once in solution, the usual controls apply and the number of entries into the vial matters as much as elapsed time. Freeze-thaw cycles and aliquoting covers protecting a reconstituted vial, and vial closures covers why entries are a limit.
What to check on arrival
- Lot number on every vial against the certificate supplied for it, reading the full string rather than the last few characters.
- The cake itself: a collapsed, shrunken or glassy cake is a finding worth raising, though it says nothing about identity or purity.
- Any temperature indicator, with the value recorded rather than the impression.
- That the quantity and strengths match the packing list before anything is put away.
Receiving and inspecting a peptide shipment is the ten-minute protocol this fits into.
What this guide deliberately does not cover
Anything about effects. LY3298176 is supplied here strictly for laboratory research, and nothing in a buying guide speaks to outcomes in any organism. The published literature on this compound is extensive and is where that question belongs.
What a buyer can settle from documentation is narrower and more useful: which molecule is in the vial, how pure it is, how much of it there is, and whether the lot in front of them is the one the certificate describes.
Planning resupply rather than reacting to it
Lead times on this class are long enough that reactive ordering produces either a gap in the work or an emergency purchase at a worse price. The fix is to measure consumption for a quarter and set a reorder point from the measurement rather than from memory.
The complication specific to research material is that it degrades while it waits, so holding more stock buys exposure rather than security beyond a point. There is a ceiling as well as a floor, and the ceiling is whatever can be used inside the material usable window.
Comparing two quotes for the same compound
With seven strengths on offer, two quotes for the same compound may not be comparing the same thing, because per-milligram figures across different vial sizes are not directly comparable in practice. Normalise before comparing anything. Put both on the strength you will actually use, add shipping, add the cost of money for the terms offered, and only then divide. Thirty-day terms are worth something, but less than they look: at a 12% annual cost of money, thirty days is worth about 1% of the invoice, so a quote on terms has to sit within roughly that margin of a prepayment quote to come out ahead.
Where the two differ on documentation, treat the weaker one as carrying a cost you cannot price but should not ignore. How to read a wholesale peptide quote takes the four lines apart.
What to record once the material arrives
- The lot, read in full from the vial rather than from the packing slip, with the strength recorded alongside it, because a compound supplied across seven strengths produces records where the lot alone does not tell a later reader how much peptide was in the vial.
- The certificate, downloaded and stored with your own records rather than linked to the supplier's archive.
- The measured content figure, since that is the number every later calculation uses.
- The salt form, which exists only in correspondence unless someone writes it down.
- The date of reconstitution and the count of entries, once the vial is opened.
Lot traceability and recordkeeping covers why the lot number is the field everything else hangs off.
A short pre-order checklist
Five questions, one email, about fifteen minutes. Can you send the certificate for a lot I would receive. Which laboratory issued it. Is the identity mass on it stated as an average or a monoisotopic value. Which salt form is supplied. What is the lead time for in stock versus made to order.
The answers matter and so does how they arrive: how quickly, whether they address what was asked, and whether they come from someone who can see the document. Comparing suppliers on documentation covers scoring the replies.
Why seven strengths exist at all
Because buyers consume at very different rates, and a single strength would force most of them into either waste or frequent reordering. A wide strength range is a convenience that transfers the sizing decision to the buyer, which is why it is worth making deliberately rather than by habit.
In short
One molecule across seven strengths. Size against what a single piece of work consumes rather than against unit price, use the certificate content figure rather than the label, expect slow dissolution because of the acyl chain, and settle documentation before price.
A note on bundles
Where a compound is offered inside a bundle, the per-vial economics change and the documentation does not. Each vial in a bundle still carries its own lot and should still be traceable to a certificate naming that lot, and a bundle that supplies one document for several lots has not met that bar.
Check the lot count against the certificate count on arrival. It takes seconds and it is the commonest documentation gap in multi-item orders.
One final note on ordering across strengths. Where several strengths are bought together, confirm that each arrives with its own lot-matched certificate rather than one document covering the order, because a multi-strength delivery is the situation where that most often goes wrong.
This is one part of buying wholesale. The wholesale buying guide covers the whole process from evaluating a supplier to placing a first order.