PT-141 and Melanotan II differ by one dalton in a thousand. They are the closest pair of commonly sold peptides in existence, and the difference is a single chemical group at one end of the molecule.
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Order this testA cyclic seven-residue peptide, the C-terminal acid form of Melanotan II. Approved as bremelanotide. The ring is closed through a lactam bridge, which makes the synthesis more demanding than the residue count suggests.
Melanotan II is the C-terminal amide; PT-141 is the C-terminal acid. Chemically that is the difference between –NH2 and –OH at one end of the chain. In mass terms it is almost exactly one dalton in 1025.
PT-141 is in fact a metabolite of Melanotan II, which is why the substitution happens in both directions and why neither compound can be confirmed by name, colour, or how it behaves on a column.
Resolving a one-dalton difference is inside the reach of a properly run triple quadrupole method, because the two molecules fragment differently even where they weigh almost the same. It is well outside the reach of any method that identifies a peptide by retention time.
If a certificate confirms PT-141 without saying how it ruled out Melanotan II, it has not answered the only question that matters here.
Linear, uncyclised material has the same residues in the same order and a different mass, because forming the ring releases a water molecule. Incomplete cyclisation is a common synthesis failure and shows up as an 18-dalton shift.
1025.2 vs 1024.2
PT-141 against Melanotan II — one dalton apart, about 0.1%
One part in a thousand. That is a single grain of rice in a two-kilogram bag. How mass spectrometry separates them anyway.
One unopened vial. Detailed posting instructions arrive with your order confirmation, immediately after you pay.
No. Lyophilised peptides travel safely at room temperature, which is how nearly all samples reach us.
An independent Ontario laboratory. Every certificate we issue names the facility that ran it — we are a testing service, not a laboratory, and we would rather say so than let you find out from the report.
You get the result. We do not soften findings, and we do not charge differently depending on what the analysis shows.
Yes. Every certificate carries an identifier that anyone can check against our records, including the vendor you bought from.
Test your pt-141
$249 CAD · about five business days from arrival · never leaves Canada