RT Journal Article
T1 Long-term memory in lipid assemblies: Rate-independent hysteresis in the ripple-to-liquid-disordered transition of sphingomyelin bilayers
A1 Llombart, Pablo
A1 De la Arada, Igor
A1 González Ramírez, Emilio J.
A1 Alonso, Alicia
A1 González Mac-Dowell, Luis
A1 Goñi, Félix M.
AB Sphingomyelin (SM) is the most abundant sphingolipid in mammalian cells. It contains a phosphorylcholine headgroup, which makes SM an analog of the (glycerol-containing) phosphatidylcholines. Palmitoyl (C16:0) SM bilayers in excess water exhibit a thermotropic transition from the ripple to the fluid phase centered at ≈41 °C. In phosphatidylcholines, as in most phospholipids, the ripple-to-fluid transition is fully reversible and virtually free of hysteresis. In this paper, however, the corresponding transition was assessed in aqueous SM by infrared (IR) spectroscopy, a technique detecting molecular vibrations. Vibrational spectra as a function of temperature revealed thermotropic phase transitions. When the samples were successively heated up and cooled down, a clear hysteresis was detected. The cooling transition started at the same temperature as the heating one, but the end-point, in terms of IR band position, was clearly different. Hysteresis was particularly visible in the shift of the IR Amide I band, associated with the lipid polar headgroup, and it was rate-independent, within a wide range of heating/cooling rates (from 5.5 °C/min to less than 0.05 °C/min). Atomistic computer simulations of the molecular dynamics provided information consistent with the IR data. In addition, it showed that the in-plane arrangement of SM bilayers displays a significant amount of hexatic order, and that the hexatic order parameter, reflecting primarily polar headgroup ordering, exhibited the same kind of hysteresis described by IR. Rate-independent hysteresis allows the development of durable memories; therefore, the observations in this paper could lead to novel applications of lipid assemblies.
PB American Institute of Physics
SN 0021-9606
YR 2025
FD 2025-04-01
LK https://hdl.handle.net/20.500.14352/119157
UL https://hdl.handle.net/20.500.14352/119157
LA eng
NO Llombart, P.; Arada, I. D. L.; González-Ramírez, E. J.; Alonso, A.; MacDowell, L. G.; Goñi, F. M. Long-Term Memory in Lipid Assemblies: Rate-Independent Hysteresis in the Ripple-to-Liquid-Disordered Transition of Sphingomyelin Bilayers. The Journal of Chemical Physics 2025, 162 (13), 135101. https://doi.org/10.1063/5.0252051.
NO This work was funded in part by the Spanish Ministry of Science, Innovation, and Universities (MCIU), Agencia Estatal de Investigación (AEI), Fondo Europeo de Desarrollo Regional (FEDER) (Grant Nos. PID2021-124461NB-I00 and PID2023-151751NB-100), the Basque Government (Grant No. IT1625-22), Fundación Biofísica Bizkaia, and the Basque Excellence Research Center (BERC) program of the Basque Government.
NO Ministerio de Ciencia, Innovación y Universidades (España)
NO Agencia Estatal de Investigación (España)
NO Fondo Europeo de Desarrollo Regional (EU)
NO Gobierno Vasco
NO Fundación Biofísica Bizkaia
NO Basque Excellence Research Center
DS Docta Complutense
RD 17 dic 2025