Peptides are tiny messenger molecules that cells use to send signals by binding...

https://yourhealthmagazine.net/article/health-news-research/how-peptides-help-scientists-understand-cell-communication/

Peptides are tiny messenger molecules that cells use to send signals by binding to specific receptors. Researchers use peptides in the lab to understand how receptors recognize signals and trigger responses, like changes in intracellular calcium levels