LL-37 Peptide Overview
LL-37 is a high-purity, synthetic peptide designed to mirror the structural and functional characteristics of the only human cathelicidin. This 37-amino acid molecule is a vital component of the innate immune system, naturally derived from the hCAP-18 precursor protein through specific proteolytic processing by proteinase 3. It is primarily expressed in neutrophils, monocytes, and various epithelial cells, particularly those lining the skin, respiratory tract, and gastrointestinal system.
In laboratory research, LL-37 is highly valued for its pleiotropic effects. It does not simply act as a passive barrier; it is an active signaling molecule that bridges innate and adaptive immunity. Current experimental models utilize LL-37 to investigate its broad-spectrum antimicrobial properties, its ability to neutralize endotoxins, and its potential to accelerate tissue remodeling. As a cationic peptide, it maintains a strong affinity for anionic surfaces, a trait that governs its interaction with both bacterial membranes and host cell receptors.
LL-37 Peptide Structure
The biological efficacy of LL-37 is a direct result of its secondary structure. Under physiological conditions, the peptide adopts an amphipathic alpha-helical conformation. This allows the hydrophobic side to interact with lipid bilayers while the hydrophilic side remains solvent-exposed, facilitating membrane pore formation in target pathogens.
Product Specifications and Formula:
- Full Sequence: LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES
- Molecular Formula: Carbon 205, Hydrogen 340, Nitrogen 60, Oxygen 53
- Molecular Weight: 4493.33 Grams per Mole
- Structure Solution Formula: C205H340N60O53
Parameter
Specification Details
Peptide Purity
Minimum 98 percent by mass
Physical State
White to off-white lyophilized powder
Net Charge
+6 (Cationic)
Formulation
Preservative-free, lyophilized
Solubility
High solubility in sterile water or dilute acetic acid
LL-37 Peptide Research
LL-37 and Inflammatory Conditions
Research into LL-37 has revealed a sophisticated role in inflammatory modulation. While early studies focused on its presence in autoimmune flare-ups, contemporary data suggests LL-37 may act as a homeostatic regulator. In conditions like psoriasis and rheumatoid arthritis, LL-37 is upregulated as part of the host response. It has been observed to modulate the activity of T-cells and dendritic cells, potentially shifting the immune environment from a pro-inflammatory state to a more balanced, regulatory state depending on the presence of specific cytokines.
LL-37 as a Potent Antimicrobial Agent
The primary investigative focus for LL-37 remains its potent antimicrobial activity. It targets a wide array of pathogens, including multidrug-resistant bacteria. By binding to the lipopolysaccharide (LPS) of Gram-negative bacteria, it disrupts the outer membrane integrity. In Gram-positive bacteria, it targets the peptidoglycan layer. This dual-action mechanism makes it a key subject in the study of alternatives to traditional antibiotics, especially in the context of biofilm prevention.
LL-37 and Respiratory Health
The respiratory tract is a major site of LL-37 activity. Research indicates that the peptide is crucial for maintaining the sterility of the airway surface liquid. Studies involving chronic obstructive pulmonary disease (COPD) and cystic fibrosis explore how LL-37 levels correlate with infection frequency. Furthermore, LL-37 has been shown to stimulate the migration of airway epithelial cells, suggesting a secondary role in repairing damage caused by chronic smoke exposure or pollutants.
Understanding LL-37 in Arthritis
In the context of joint health, LL-37 is found in high concentrations in the synovial fluid of inflamed joints. While its presence was once thought to be purely pathological, newer research suggests that LL-37 may help protect the joint by neutralizing pro-inflammatory DNA/RNA complexes that trigger toll-like receptors. Animal studies have demonstrated that LL-37 analogs can reduce the severity of joint swelling and cartilage degradation.
LL-37 and Intestinal Health
LL-37 is essential for the maintenance of the intestinal barrier. In experimental models of colitis, LL-37 has been shown to reduce the rate of epithelial cell death and promote the expression of tight junction proteins. Its ability to neutralize intestinal pathogens while simultaneously calming the local immune response makes it a candidate for studying the management of inflammatory bowel disease (IBD).
LL-37 and Intestinal Cancer
Ongoing studies are investigating the anti-proliferative effects of LL-37 in certain types of gastrointestinal cancers. It appears that LL-37 can induce apoptosis in cancerous cells while leaving healthy cells intact. This selectivity is thought to be mediated through the FPR2 receptor and is often enhanced by the presence of Vitamin D, which is a known regulator of cathelicidin expression.
LL-37 and Blood Vessel Formation
Angiogenesis, or the formation of new blood vessels, is significantly influenced by LL-37. By interacting with endothelial cells, the peptide triggers pathways that lead to vessel sprouting. This is particularly relevant in wound healing research, where the restoration of blood flow to damaged tissue is a primary goal for successful recovery.
Ongoing LL-37 Research
Current research is diving deeper into the "context-specific" behavior of LL-37. Scientists are studying how the peptide changes its function based on the pH and salt concentration of the surrounding environment. This flexibility allows LL-37 to be effective in diverse areas of the body, from the acidic surface of the skin to the neutral environment of the blood.
Article Author
This comprehensive review was organized and edited by Dr. Ayyalusamy Ramamoorthy, Ph.D. As a leading figure in biophysical chemistry, Dr. Ramamoorthy’s work focuses on the high-resolution structural determination of membrane-associated peptides. His research has paved the way for understanding how LL-37 transitions from a disordered state in solution to a structured helix upon contact with a pathogen.
Scientific Journal Author
Dr. Ayyalusamy Ramamoorthy serves as a Professor at the University of Michigan. His landmark publication, "LL-37, the only human cathelicidin: structure, function, and applications," published in Biochimica et Biophysica Acta in 2006, remains one of the most cited papers in the field. His collaborations with experts such as Dr. Robert E.W. Hancock have expanded the global understanding of host defense peptides.
Reference Citations
- Durr UH, Sudheendra US, Ramamoorthy A. LL-37, the only human cathelicidin: structure, function, and applications. Biochim Biophys Acta. 2006;1758(9):1408-1425.
- Vandamme D, et al. A comprehensive summary of LL-37 and its derived peptides. Cell Mol Life Sci. 2012;69(20): 3885-3908.
- Nijnik A, Hancock RE. The roles of cathelicidin LL-37 in immune defences and novel clinical applications. Curr Opin Hematol. 2009;16(1):41-47.
- Overhage J, et al. Human host defense peptide LL-37 prevents bacterial biofilm formation. Infect Immun. 2008;76(9):4176-4182.
- Heilborn JD, et al. The cathelicidin peptide LL-37 is involved in re-epithelialization of human skin wounds and is lacking in chronic ulcers. J Invest Dermatol. 2003;120(3):379-389.
- Barlow PG, et al. Antiviral activity and increased host defense response of LL-37 in influenza virus infection. J Immunol. 2011;186(10): 6166-6174.
- Kahlenberg JM, Kaplan MJ. Little peptide, big effects: the role of LL-37 in inflammation and autoimmune disease. J Immunol. 2013;191(10):4895-4901.
- Mookherjee N, et al. Modulation of the TLR-mediated inflammatory response by LL-37. J Immunol. 2006;176(4):2455-2464.
- Krasnodembskaya A, et al. Human cathelicidin peptide LL-37 promotes mesenchymal stem cell-mediated immunomodulation and tissue repair. Proc Natl Acad Sci USA. 2010;107(32):14292-14297.
- Ramos R, et al. Wound healing activity of LL-37 peptide. Peptides. 2011;32(9):1849-1858.
Storage
Storage Instructions
LL-37 is produced through a precise lyophilization process, resulting in a crystalline powder that is highly stable for shipping and short-term storage. To maintain long-term stability, the lyophilized peptide should be stored at -20 or -80 degrees Celsius. Once the product is reconstituted in an aqueous solution, its shelf life is reduced to approximately 30 days, provided it is kept under refrigeration at 4 degrees Celsius.
Best Practices For Storing Peptides
Researchers should avoid repeated exposure to light and oxygen. For optimal results, use an airtight container and store the peptide in a dedicated laboratory freezer that does not utilize a frost-free cycle, as the temperature fluctuations in such units can degrade the peptide's delicate alpha-helical structure.
Preventing Oxidation and Moisture Contamination
Before opening the vial, allow it to reach room temperature. This simple step prevents atmospheric moisture from condensing on the cold powder, which can lead to hydrolysis. For peptides used over multiple sessions, the use of a desiccator is highly recommended.
Storing Peptides In Solution
If the peptide must be stored in solution, ensure the pH is slightly acidic (between 5 and 6) to discourage bacterial growth and minimize degradation. Using sterile, deionized water or a phosphate-buffered saline (PBS) solution is standard, but the peptide should be aliquoted into single-use vials to prevent frequent freezing and thawing.
Peptide Storage Containers
While plastic vials are common for shipping, borosilicate glass vials are preferred for long-term laboratory storage due to their chemical inertness. Ensure all containers are sterile and free from contaminants that could interfere with experimental outcomes.
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