LC-LL-37, 5-FAM labeled

Product Name: LC-LL-37, 5-FAM labeled

Sequence One Letter Code: 5-FAM-LC-LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES

Sequence Three Letter Code: 5-FAM-LC-Leu-Leu-Gly-Asp-Phe-Phe-Arg-Lys-Ser-Lys-Glu-Lys-Ile-Gly-Lys-Glu-Phe-Lys-Arg-Ile-Val-Gln-Arg-Ile-Lys-Asp-Phe-Leu-Arg-Asn-Leu-Val-Pro-Arg-Thr-Glu-Ser-OH

Molecular Weight: 4964.9

Purity: 95%

Form: Lyophilized

Storage Conditions: - 20 °C Protected from light

Research Area: Bacterial

Source / Species: human

Conjugation: Conjugated

Conjugation Type: Fluorescent dyes

Code Nacres: NA.26

Application: FAM-LL-37 is a fluorescently labeled form of LL-37, the only human cathelicidin antimicrobial peptide involved in innate immune defense. LL-37 is an amphipathic α-helical peptide that exhibits broad antimicrobial activity by disrupting microbial membranes and modulating host immune responses. Conjugation with the 5-FAM fluorophore enables fluorescence-based visualization and quantification in cellular uptake, localization, and binding assays. This labeled peptide supports studies of peptide–membrane interactions, host–pathogen defense mechanisms, and immune signaling pathways. It is widely used in research investigating antimicrobial activity, inflammatory signaling, wound healing, and epithelial barrier responses. The fluorescent tag also allows convenient tracking of LL-37 behavior in live cells and biochemical assays examining antimicrobial peptide function.

Current Research: Antimicrobial peptides (AMPs) are key components of the innate immune system, acting as rapid-response molecules that protect the host against microbial invasion. Among human AMPs, LL-37 is particularly significant because it is the only cathelicidin-derived antimicrobial peptide identified in humans. Beyond its direct antimicrobial activity, LL-37 plays an important role in regulating immune responses, inflammation, and tissue repair. To better understand how this multifunctional peptide operates within biological systems, researchers often employ FAM-LL-37, a fluorescently labeled version of LL-37 that enables real-time visualization and quantitative analysis in cellular and biochemical experiments. Structural and Functional Features of LL-37 LL-37 is a 37–amino acid amphipathic α-helical peptide generated through proteolytic cleavage of the human cathelicidin precursor protein hCAP-18. Its amphipathic structure allows the peptide to interact efficiently with lipid membranes. This structural property underlies its broad-spectrum antimicrobial activity, which includes activity against bacteria, fungi, and certain viruses. The antimicrobial function of LL-37 largely arises from its ability to disrupt microbial membranes. Because microbial membranes are typically enriched with negatively charged lipids, they attract the positively charged regions of LL-37. The peptide then inserts into the membrane, destabilizing lipid organization and leading to membrane permeabilization or rupture. In addition to its direct antimicrobial action, LL-37 also acts as an immunomodulatory signaling molecule. It can influence immune cell recruitment, regulate inflammatory cytokine production, and enhance barrier defense mechanisms in epithelial tissues. These diverse biological roles make LL-37 a major focus of research in host–pathogen interactions and innate immunity. Fluorescent Labeling with 5-FAM To investigate LL-37 behavior in complex biological systems, researchers often use FAM-LL-37, in which the peptide is conjugated with the fluorophore 5-carboxyfluorescein (5-FAM). This fluorescent dye emits bright green fluorescence when excited by appropriate wavelengths, allowing the peptide to be easily detected using fluorescence microscopy, flow cytometry, or plate-based fluorescence assays. The addition of the FAM label provides several experimental advantages. First, it enables direct visualization of peptide localization within cells and tissues. Second, it allows quantitative tracking of peptide uptake and distribution in live-cell experiments. Finally, fluorescence tagging supports high-throughput biochemical assays that measure peptide binding, membrane interactions, and antimicrobial activity. By combining the biological activity of LL-37 with fluorescent detection capability, FAM-LL-37 serves as a powerful probe for studying antimicrobial peptide dynamics. Investigating Peptide–Membrane Interactions One of the most common applications of FAM-LL-37 is the study of peptide–membrane interactions. Since the antimicrobial activity of LL-37 depends heavily on its interaction with lipid bilayers, understanding how the peptide binds to and disrupts membranes is essential for elucidating its mechanism of action. Fluorescent labeling allows researchers to monitor membrane binding, insertion, and distribution using imaging or fluorescence spectroscopy techniques. For example, FAM-LL-37 can be used to observe how the peptide associates with bacterial membranes or model lipid vesicles. Such experiments provide insights into the structural and biophysical processes that lead to microbial membrane disruption. In addition, fluorescence assays can help determine binding affinity, membrane selectivity, and peptide aggregation behavior, all of which influence antimicrobial potency. Studying Cellular Uptake and Localization Beyond membrane interactions, LL-37 is also known to enter host cells and participate in intracellular signaling processes. FAM-LL-37 enables researchers to track cellular uptake pathways and intracellular distribution of the peptide. Using fluorescence microscopy or flow cytometry, investigators can visualize how LL-37 is internalized by immune cells, epithelial cells, or other cell types involved in host defense. These experiments help clarify whether LL-37 acts primarily at the cell surface or also exerts functions within intracellular compartments. Tracking the peptide in live cells is particularly useful for examining how LL-37 participates in immune signaling pathways, including pathways involved in inflammation and pathogen recognition. Applications in Host–Pathogen Defense Research Because LL-37 plays multiple roles in host defense, FAM-LL-37 has become widely used in studies of innate immunity and microbial pathogenesis. Researchers use the fluorescent peptide to examine how antimicrobial peptides interact with bacterial cells, how pathogens respond to these interactions, and how host cells coordinate immune responses. In infection models, FAM-LL-37 can help visualize the binding of antimicrobial peptides to microbial surfaces, offering insight into how these peptides target pathogens. Such studies are valuable for understanding the mechanisms through which innate immune defenses control microbial populations. Relevance to Inflammation and Tissue Repair LL-37 is also involved in inflammatory signaling, wound healing, and epithelial barrier regulation. The peptide can influence immune cell recruitment, stimulate cytokine production, and promote tissue repair processes in damaged or infected tissues. By enabling real-time tracking of LL-37 localization and activity, FAM-LL-37 supports investigations into how antimicrobial peptides contribute to inflammatory regulation and epithelial barrier responses. These studies are particularly relevant in research areas such as chronic inflammatory diseases, skin disorders, and mucosal immunity. A Versatile Tool for Antimicrobial Peptide Research FAM-LL-37 provides researchers with a convenient and powerful method for studying the behavior of LL-37 in biological systems. The combination of intrinsic antimicrobial activity and fluorescence-based detectability allows scientists to monitor peptide localization, uptake, and interactions in real time. As interest in antimicrobial peptides continues to grow—especially in the context of antibiotic resistance and immune regulation—fluorescent probes such as FAM-LL-37 will remain valuable tools for advancing our understanding of host defense mechanisms and the functional biology of antimicrobial peptides.