Cholesterol induced asymmetry in DOPC bilayers probed by AFM force spectroscopy

• Published in: Biochimica et biophysica acta. Biomembranes 2018-05, Vol.1860 (5), p.953-959
• Main Authors: Adhyapak, Pranav R., Panchal, Suresh V., Murthy, Appala Venkata Ramana
• Format: Article
• Language: English
• Subjects: Asymmetry; Atomic Force Microscopy; Biomimetic Materials - chemistry; Cholesterol; Cholesterol - chemistry; Cholesterol - pharmacology; DOPC; Force spectroscopy; Lipid bilayer; Lipid Bilayers - chemistry; Mechanical Phenomena - drug effects; Membrane Lipids - chemistry; Microscopy, Atomic Force - methods; Molecular Conformation - drug effects; Nanomechanical properties; Phosphatidylcholines - chemistry; Spectrum Analysis
• ISSN: 0005-2736; 1879-2642
• DOI: 10.1016/j.bbamem.2018.01.021

Cholesterol induced mechanical effects on artificial lipid bilayers are well known and have been thoroughly investigated by AFM force spectroscopy. However, dynamics of cholesterol impingement into bilayers at various cholesterol concentrations and their effects have not been clearly understood. In this paper we present, the effect of cholesterol as a function of its concentration in a simple single component dioleoylphosphatidylcholine (DOPC) bilayer. The nature of measured breakthrough forces on a bilayer with the addition of cholesterol, suggested that it is not just responsible to increase the mechanical stability but also introduces irregularities across the leaflets of the bilayer. This cholesterol induced asymmetry across the (in the inner and outer leaflets) bilayer is related to the phenomena of interleaflet coupling and is a function of cholesterol concentration probed by AFM can provide an unprecedented direction on mechanical properties of lipid membrane as it can be directly correlated to biophysical properties of a cell membrane. [Display omitted] •Cholestrol changes the mechanical strength of the DOPC bilayer is a strong function of its concentration.•Bilayer behaves as single coupled system in its pure form resulting in single breakthrough event in AFM force spectroscopy.•At excess cholesterol, interleaflet coupling will weaken and bilayer behave as an uncoupled system.•This results in sequential penetration and gives raise to two breakthrough force event in AFM force spectroscopy.•This induces rapid redistribution of cholesterol in the bilayer leading to lipid asymmetry.