Single-molecule visualization of dynamic transitions of pore-forming peptides among multiple transmembrane positions.
Li. Ying Y; Qian. Zhenyu Z; Ma. Li L; Hu. Shuxin S; Nong. Daguan D; Xu. Chunhua C; Ye. Fangfu F; Lu. Ying Y; Wei. Guanghong G; Li. Ming M
Key Findings
- A single‑molecule fluorescence method (SIFA) can measure a protein’s distance from a surface with a d‑4 dependence.
- LL‑37 was observed shifting among five distinct positions within a lipid bilayer: surface, upper leaflet, centre, lower leaflet, and bottom.
- The technique simultaneously tracks vertical insertion depth and lateral diffusion of membrane proteins.
Practical Outcomes
- For now, the work is mainly a research tool and doesn’t suggest new dosing or usage tips for LL‑37. Biohackers won’t change their protocols based on this study, but it may lead to future insights into how membrane‑active peptides work.
Summary
Scientists created a new imaging trick that lets them see exactly how the antimicrobial peptide LL‑37 moves up and down inside a cell‑like membrane, spotting it in five different layers. While this helps researchers understand the peptide’s behavior, it doesn’t give any direct advice on how to take or use LL‑37 for health purposes.
Abstract
Research on the dynamics of single-membrane proteins remains underdeveloped due to the lack of proper approaches that can probe in real time the protein's insertion depth in lipid bilayers. Here we report a single-molecule visualization method to track both vertical insertion and lateral diffusion of membrane proteins in supported lipid bilayers by exploiting the surface-induced fluorescence attenuation (SIFA) of fluorophores. The attenuation follows a d<sup>-4</sup> dependency, where d is the fluorophore-to-surface distance. The method is validated by observing the antimicrobial peptide LL-37 to transfer among five transmembrane positions: the surface, the upper leaflet, the centre, the lower leaflet and the bottom of the lipid bilayer. These results demonstrate the power of SIFA to study protein-membrane interactions and provide unprecedented in-depth understanding of molecular mechanisms of the insertion and translocation of membrane proteins.
Study Information
pubmed
2016
2016-09-30T00:00:00.000Z
10.1038/ncomms12906
40
82