Selank

Selank is the tetrapeptide tuftsin — an immunologically active fragment of the IgG heavy chain — extended with the same proline-glycine-proline stabilising tail used in Semax. Tuftsin itself is degraded within minutes; the extension pushes the half-life into a range where systemic effects are observable. The research interest is anxiolytic activity reported without the sedation or motor impairment characteristic of benzodiazepine-class compounds, with proposed mechanisms involving GABA-A receptor expression, enkephalin degradation inhibition and monoamine modulation.

Selank and Semax share the stabilising tail and are frequently studied together, but they are pharmacologically distinct — different parent fragments, different receptor systems. Treating them as interchangeable nootropics, which a lot of secondary writing does, misreads the literature.