Chemistry & nose-to-brain delivery
Selank's properties are written into its structure: seven amino acids, three prolines that stiffen the chain and…
Seven residues, three prolines, and a path to the brain
Selank's properties are written into its structure: seven amino acids, three prolines that stiffen the chain and resist enzymes, and an intranasal route that gives partial direct access to the brain. This unit shows the molecule and follows it from a nasal spray to its target.
It also confronts an inconvenient gap: how much of an intranasal dose ends up in brain tissue is not stated in any source this course could read, which is why "sprayed on the nose" is not the same as "delivered to the brain."
Key terms
The molecule, residue by residue
Selank's sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro: the tuftsin core (Thr-Lys-Pro-Arg) followed by the Pro-Gly-Pro tail. Click each building block (residue) to see its role. The standout feature is the three prolines, which stiffen the chain and make it hard for enzymes to cut.
The structure frames the pharmacology. The first four residues are tuftsin, carrying the immune heritage; the last three are the added tail. Proline's rigid ring blocks many of the enzymes that cut small peptides, which is the general chemistry the designers were relying on when they added it, though how much durability it actually bought is not measured in any source readable here.
AdvancedWhy three prolines matter so much
Proline is the only amino acid whose side chain loops back to its own backbone nitrogen, forcing a kink and removing the amide hydrogen that many proteases recognize. That is general peptide chemistry, and it is the reasoning behind the Pro-Gly-Pro design, which its authors describe as elongating the tuftsin fragment to enhance metabolic stability and the length of action. What no readable source provides is the payoff measured: neither tuftsin's stability nor Selank's has been quantified here.