Literature-Grounded Asymmetry Tool

Lipid Flip-Flop Explorer

Explore how spontaneous lipid transbilayer diffusion erodes leaflet asymmetry over time, using literature-backed kinetic presets rather than a single universal flip-flop rule.

Preset-specific kinetics Temperature-aware when supported Symmetry and asymmetry over time

Preset

High confidence

Literature preset

Temperature

°C

Modifier

Asymmetry Setup

Initial state

Starting outer-leaflet fraction

Evaluate at

Plot window

× t½

The plot window scales to the kinetic half-time of the chosen preset. For fixed-temperature reference systems, this keeps slow vesicle presets and fast supported-bilayer presets readable on the same page.

Scope

Caveat

Vesicle and supported-bilayer measurements are not interchangeable.
Temperature is only freely adjustable when the source paper supports it.
Curvature and cholesterol are not generalized in v1 because the quantitative evidence is too system-specific.
DOPS is not yet a standalone preset because I still do not have a comparably clean spontaneous DOPS vesicle dataset to parameterize with confidence.

Asymmetry Outcome

Vesicle

Outer leaflet at selected time 0%

Inner leaflet at selected time 0%

Symmetry between layers 0%

                Asymmetry remaining
                0%
              

Outer→inner rate constant 0 s⁻¹

Inner→outer rate constant 0 s⁻¹

Asymmetry half-time 0 h

Long-time outer leaflet equilibrium 50%

Leaflet Fractions

Time course

outer leaflet inner leaflet selected time

Symmetry vs Asymmetry

Derived metrics

symmetry achieved asymmetry remaining selected time

Export

CSV

Export the current preset and time course as a CSV for plotting elsewhere or documenting assumptions alongside experiments.

Interpretation

Notes

Saturation Evidence

Unsaturation trend

SOPC membrane t½ ≈ 11.5 h

SDPC membrane t½ ≈ 0.29 h

DDPC membrane t½ ≈ 0.086 h

In a probe-based PC membrane study, increasing acyl-chain unsaturation strongly accelerated flip-flop [8]. This is integrated here as an evidence snapshot rather than a universal preset because the source uses an NBD-PE reporter rather than a label-free lipid-specific rate law.

DOPC Evidence

Direct vesicle anchor

DOPC in PSM/DOPC/Cho aLUV k ≈ 6.4 × 10^-6 s^-1

PSM in same system k ≈ 2.7 × 10^-6 s^-1

Measurement temperature 40 °C

This asymmetric-LUV study provides a direct unsaturated-PC reference and supports the idea that DOPC translocates faster than the more tightly packed PSM in the same membrane context [7].

Literature Basis

Primary sources

Garg S, Porcar L, Woodka AC, Butler PD, Perez-Salas U, Lund R. 1H NMR Shows Slow Phospholipid Flip-Flop in Gel and Fluid Bilayers. ACS Central Science. 2017. PMC
Anglin TC, Conboy JC. 1,2-Diacyl-Phosphatidylcholine Flip-Flop Measured Directly by Sum-Frequency Vibrational Spectroscopy. Biophysical Journal. 2005. PMC
Anglin TC, Conboy JC. Kinetics and thermodynamics of flip-flop in binary phospholipid membranes measured by sum-frequency vibrational spectroscopy. Biochemistry. 2009. PubMed
Nakano M, Fukuda M, Kudo T, et al. Flip-flop of phospholipids in vesicles: kinetic analysis with time-resolved small-angle neutron scattering. J Phys Chem B. 2009. PubMed
Nguyen MHL, DiPasquale M, Rickeard BW, et al. Peptide-Induced Lipid Flip-Flop in Asymmetric Liposomes Measured by Small Angle Neutron Scattering. Langmuir. 2019. PMC
Hymas PPH, Conboy JC. Phosphatidylserine affinity for and flip-flop dependence on Ca2+ and Mg2+ ions. Faraday Discussions. 2025. PubMed
Watanabe H, Hanashima S, Yano Y, Yasuda T, Murata M. Passive Translocation of Phospholipids in Asymmetric Model Membranes: Solid-State 1H NMR Characterization of Flip-Flop Kinetics Using Deuterated Sphingomyelin and Phosphatidylcholine. Langmuir. 2023. PubMed
Armstrong VT, Brzustowicz MR, Wassall SR, Jenski LJ, Stillwell W. Rapid flip-flop in polyunsaturated (docosahexaenoate) phospholipid membranes. Archives of Biochemistry and Biophysics. 2003. PubMed

This app intentionally does not generalize a single rate law across all membrane systems. Presets are tied to the model geometry and measurement context of the source literature.