01 / Molecular architecture
A closer look at the chain.
The seven-residue reference has a lactam connection between Asp at position 2 and Lys at position 7. It is N-acetylated and has an amidated C-terminus; the ring is not shown by the linear sequence alone.
- 7 residues
- Asp2–Lys7 lactam ring
- C-terminal amide
- 1Nle
- 2Asp
- 3His
- 4D-Phe
- 5Arg
- 6Trp
- 7Lys
Reference information: [1][2]. Actual lot identity must be verified separately.
Closing a ring through side chains.
The Asp2–Lys7 lactam links side-chain groups through an amide bond. It is different from a disulfide bridge between cysteines and different from joining the backbone’s two ends. A line of seven residue names leaves out this extra connection, so the ring must be specified alongside the sequence.
Comparing a closely related reference.
Melanotan-2 and PT-141 share the residue names shown in their reference schematics, making terminal notation particularly useful. Melanotan-2 ends in an amide, whereas the PT-141 reference has a C-terminal acid. A comparison based only on the seven residue labels misses that chemical distinction.
Structure and research references: [1]
02 / Read the evidence
Research & analytical context.
Melanotan-2 is used in melanocortin-receptor investigations. Receptor subtype, expression system and endpoint all matter when comparing activity with other members of the family.
The distinction that matters
PT-141 is closely related but differs in terminal chemistry. Do not identify the two materials from their seven residue names alone.
03 / From reference to record
Know the lot, too.
A publication describes its own test material. Your lot’s certificate describes what was tested on that lot. Keep the compound name, batch number and reported methods together when reviewing a result.
Identity & composition
Check sequence or chemical form, terminal modifications, counterion and—where relevant—each blend component.
Analytical results
Read purity, content, sterility and endotoxin results as separate measurements. Only call a test passed when the actual report supports it.
Handling & storage notes
Lyophilized material: Store at −20°C; protect from light and moisture.
Follow the material-specific label and supporting storage documentation. These temperatures do not establish a shelf life.
How to store lyophilized peptides04 / Reference questions
A few details, explained.
Is the ring a disulfide bridge?
No. This reference uses an Asp–Lys lactam, an amide connection between side chains. A disulfide is a different bond type involving sulfur atoms.
Why does the drawing still look like a line?
The sequence schematic emphasizes residue order. The accompanying ring annotation supplies connectivity that a straight sequence cannot show; it is not intended as a three-dimensional structure.
Read alongside the references: [1]
05 / Continue reading
Go to the source.
Each source is labeled by its type. External sources are not Pioneer batch certificates.