LL-37

LL-37 is the mature antimicrobial peptide cleaved from human cathelicidin hCAP18, named for its two leading leucines and 37-residue length. It is strongly cationic and forms an amphipathic helix in membrane-mimetic environments, which is the structural basis for its membrane-disrupting antimicrobial activity. Beyond direct antimicrobial work it is studied as an immunomodulator and chemoattractant, and as a wound-environment signalling molecule.

Two handling notes matter more for this peptide than most. First, it is highly cationic and adsorbs aggressively to glass and untreated plastic — measurable losses in dilute solution are an adsorption artefact, not degradation, and low-binding tubes solve it. Second, its antimicrobial activity is strongly salt-sensitive, so buffer composition is not a detail you can vary casually between experiments and still compare results.