https://video.igem.org/videos/watch/6f523e0a-e014-4fec-8be1-b95514375191 DEHP Partitioning into the LGG Membrane - All-Atom MD (50 s)A 50-second visualization of what DEHP actually does when it meets the membrane of Lactobacillus rhamnosus GG, built frame-by-frame from our own CHARMM36 production trajectory. What you are watchingThe system - a 3:1 POPG:POPE bilayer standing in for a Gram-positive membrane: 150 lipids, an 8.05 × 8.05 nm patch, 86.4 Ų per lipid, 3.92 nm phosphate-to-phosphate. CHARMM36 all-atom, 437.8 ns of production., Partitioning - eight DEHP molecules start in bulk water and leave it. The last one is inside by 37.0 ns., Depth - they stop at a density peak 0.92 nm from the bilayer midplane: the glycerol and upper acyl region, 47 % of the way out to the phosphate planes at ±1.96 nm. Not the headgroups, not the core., And they stay - across the remaining 401 ns there is not one return to bulk water. Per-molecule mean depths over the 219–438 ns window run −0.93 to +0.85 nm; four sit in the upper leaflet and four in the lower, with no prompting., Why - umbrella sampling puts the free energy of transfer at −3.06 kcal/mol against bulk water: 5.0 kT at 310 K, with a ~5 kJ/mol barrier at the midplane., Cargo held - thermodynamics parks the molecule. No active retention step is required for the chassis to carry it out of the gut., The data behind itEvery depth on screen is read straight from dehp_all_z.xvg, the production trajectory - 8 molecules × 4,379 time points, unwrapped across the periodic boundary. Nothing in the vertical axis is illustrative. On-screen values are colour-coded: white = measured, green = derived, amber = pending. Three things are deliberately not trajectory data and are labelled so: lateral drift is a random walk at the measured diffusion coefficient (1.6 × 10⁻⁷ cm²/s), molecular tilt is set from the measured mean (36.8°, bimodal) rather than per frame, and the PMF curve between its measured minimum and endpoints is schematic. The clock is non-linear - it dwells on the 0-45 ns partitioning window and compresses the steady state. Compute: ≈3,600 single-CPU-hours equivalent. Why it mattersThis is the physical foundation of the entire Lilieum strategy. We do not engineer a DEHP binder because the chassis already binds it, for free, and holds it: a 5 kT well is deep enough that release is rare on gut-transit timescales. It also explains why our bilayer choice matters - our POPG:POPE system puts 66 % of DEHP occupancy in the acyl tails versus 23 % in the published POPC work (Bider 2020), so Gram-positive membrane composition is not a cosmetic detail. Finally, it supplies the input to our sensing logic: DEHP accumulating in the acyl region is what raises chain order and membrane rigidity, which is the signal DesK reads. https://2026.igem.wiki/fsu Tue, 20 Oct 2026 02:54:08 GMT https://validator.w3.org/feed/docs/rss2.html PeerTube - https://video.igem.org https://video.igem.org/client/assets/images/icons/icon-1500x1500.png https://video.igem.org/videos/watch/6f523e0a-e014-4fec-8be1-b95514375191 All rights reserved, unless otherwise specified in the terms specified at https://video.igem.org/about and potential licenses granted by each content's rightholder.