What the number means
Add up the mass of every atom in a molecule and you get its molecular weight. Every amino acid adds a known amount, so each peptide sequence has its own expected weight. PubChem lists the expected weight for each compound.
You may see two kinds of figure. The average molecular weight (what PubChem and most labels show) allows for natural isotopes. The monoisotopic mass uses only the most common isotope of each element and is slightly lower. Mass spectrometry reports often use the monoisotopic mass.
Why reports show odd numbers
Mass spectrometry measures charged molecules. A peptide that picks up one proton appears at its mass plus about 1, written [M+H]+. One that picks up two appears at roughly half its mass plus 1, written [M+2H]2+. That is why BPC-157, at 1,419.5 g/mol, is often reported at about 710.8.
What it cannot tell you
Educational information only. Nothing here is medical advice, dosing guidance or a recommendation to use any substance. Research peptides are not approved medicines and are not for human or animal consumption. Speak to a qualified professional and follow the law where you are.
