Cyclotides are fascinating microproteins (≈30–40 residues long) with a unique head-to-tail cyclized backbone, stabilized by three disulfide bonds forming a cystine knot. This unique topology makes them exceptionally stable to chemical, thermal and biological degradation compared to other peptides of similar size. Cyclotides have been also found to be highly tolerant to sequence variability, aside from the conserved residues forming the cystine knot, able to cross cellular membranes and modulate intracellular protein–protein interactions both in vitro and in vivo. These properties make them ideal scaffolds for many biotechnological applications. This article provides and overview of the properties of cyclotides and their applications as molecular imaging agents and peptide-based therapeutics.

环肽是一种令人着迷的微生物蛋白质（约 30-40 个残基长），具有独特的头尾环化主链，通过形成胱氨酸结的三个二硫键稳定。与其他类似大小的肽相比，这种独特的拓扑结构使它们对化学、热和生物降解特别稳定。还发现，除了形成胱氨酸结的保守残基外，环肽对序列变异具有高度耐受性，能够穿过细胞膜并在体外和体内调节细胞内蛋白质-蛋白质相互作用。这些特性使它们成为许多生物技术应用的理想支架。本文概述了环肽的特性及其作为分子成像剂和基于肽的治疗剂的应用。