LL-37 5mg

What LL-37 is

LL-37 is a 37-residue linear peptide, LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES, built only from standard L-residues, uncapped at both ends (N-terminal amine, C-terminal carboxylic acid). It contains no cysteine and therefore no disulfide bonds. The name is literal: the chain opens with two leucines and runs to thirty-seven residues.

The sequence corresponds to the C-terminal segment, residues 134 to 170, of the human cathelicidin precursor hCAP18, which is where the catalog’s “CAP-18” tag comes from; the precursor itself is a much larger protein. Other fragments of the same precursor circulate under their own names, and a 36-mer or a single-substitution variant would still start with LL, so the printed sequence rather than the shorthand is the real identifier.

LL-37 5mg specification

How LL-37 is analyzed

LL-37 carries eleven basic residues, six lysines and five arginines, against five acidic ones, for a net charge near +6 at neutral pH. Drawn as a helix it presents one hydrophobic face and one charged face, and on reverse phase that hydrophobic face binds strongly, so the peptide elutes late at high organic strength. The basic side chains can interact with residual silanols and cause tailing, which consistent TFA ion-pairing and a wide-pore phase (often 300 Å) help to control. Self-association and surface adsorption can also produce broad or split peaks that reflect sample behavior rather than impurity. There is no tryptophan or tyrosine, and the four phenylalanines contribute little at 280 nm, so the purity read is taken near 214 nm.

Electrospray gives a ladder of multiply charged ions whose deconvoluted mass should fall close to 4493.3. For a chain of this length, deletion sequences missing one residue are the principal synthesis impurity, and they sit close to the main peak in retention. LL-37 5mg carries its own independent HPLC figure on this page, and an unnumbered LL-37 vial is traced to that figure through the crimp and cap color.

Research contexts for LL-37

• Peptide-membrane interaction studies with model lipid vesicles and supported bilayers
• Circular dichroism of helix formation in membrane-mimetic solvents
• Cytokine-signaling assays in cultured epithelial cell lines
• Chromatographic method development for late-eluting, cationic, amphipathic peptides
• Discrimination of truncated or substituted cathelicidin-derived variants by LC-MS

LL-37 5mg belongs on the bench, in membrane models, cell-culture wells and chromatographic methods, and has no intended use in a person or animal.

LL-37 questions

Why does LL-37 come off the column at such high organic strength?

Its hydrophobic face, built from four phenylalanines plus several leucines, isoleucines and valines, binds firmly to a C18 phase. Late elution is the normal behavior for this sequence.

Is LL-37 the same molecule as hCAP18?

No. hCAP18 is the full precursor protein, and LL-37 is its 37-residue C-terminal segment, residues 134 to 170.

Why does counter-ion content matter so much for LL-37?

With eleven basic side chains plus the N-terminal amine, a trifluoroacetate salt carries many counter-ions per molecule. That pushes net peptide content noticeably away from the chromatographic purity figure.