MT-1 vs MT-2: Linear and Cyclic Melanocortin Analogs Compared
MT-1 and MT-2 are both synthetic analogs of alpha-melanocyte-stimulating hormone (alpha-MSH) from the same University of Arizona research program. MT-1 is a linear 13-residue peptide; MT-2 is a much smaller cyclic lactam. This post compares their structures, sizes, the receptor questions the literature asks, and how each is checked in the laboratory.
Research blog: general laboratory-science and literature context. Not medical advice. Sealed Peptides materials are for laboratory research use only, and are not for human or veterinary use.
One parent hormone, two designs
Both molecules start from alpha-MSH, the 13-residue melanocortin peptide. Researchers replaced methionine at position 4 with norleucine (Nle), which cannot oxidize, and phenylalanine at position 7 with its D-isomer, which slows enzymatic breakdown.
MT-1 keeps the full linear 13-residue backbone with those two substitutions. MT-2 trims the sequence to the core and closes it into a ring through a lactam bridge between aspartic acid and lysine side chains.
Sequence and size at a glance
- MT-1: Ac-Ser-Tyr-Ser-Nle-Glu-His-D-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2, formula C78H111N21O19, listed molecular weight 1646.9 Da. Linear, N-acetylated and C-amidated.
- MT-2: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, formula C50H69N15O9, listed molecular weight 1024.2 Da. Cyclic, seven residues.
- Shared: the His-D-Phe-Arg-Trp core that melanocortin receptors recognize, and both supplied as lyophilized powders.
What the literature examines
Melanocortin research describes five receptor subtypes, MC1R through MC5R. Papers on MT-1 mostly study MC1R, the subtype found on melanocytes, in cell and tissue models. MT-2 binds several subtypes with less selectivity, so its literature spans MC1R, MC3R and MC4R signaling in rodent and cell models.
The MT-1 and MT-2 research overviews summarize that literature with citations.
Checking each one in the lab
The roughly 623 Da mass difference makes the two easy to tell apart by Mass spectrometry. Because MT-2 is cyclic, its mass is 18 Da lower than the same residues joined in a line, which is a quick check that the ring actually closed.
On reversed-phase HPLC the two elute at clearly different times. The peptide molecular weight estimator reproduces the linear MT-1 mass from its sequence.
Handling notes
Both are stored sealed and frozen as lyophilized powders. Tryptophan in both sequences is sensitive to light, so amber vials and limited light exposure are common practice. For solution arithmetic with each listed molecular weight, see the MT-1 and MT-2 calculators.
Terms used in this guide
Related tools and guides
For laboratory research use only. Not for human or veterinary use. This post is general chemistry and literature context and does not describe or endorse any use of Sealed Peptides products.
